G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
heat shock 70kDa protein 5 (glucose-regulated protein, 78kDa)
G00000266 (Mus musculus)

Databases (9)

Curated Gene
OTTHUMG00000020672 (Vega human gene)
ENSG00000044574 (Ensembl human gene)
3309 (Entrez Gene)
595 (G2Cdb plasticity & disease)
HSPA5 (GeneCards)
138120 (OMIM)
Marker Symbol
HGNC:5238 (HGNC)
Protein Expression
5221 (human protein atlas)
Protein Sequence
P11021 (UniProt)

Synonyms (1)

  • BiP

Literature (185)

Pubmed - other

  • GRP78, but Not Protein-disulfide Isomerase, Partially Reverses Hyperglycemia-induced Inhibition of Insulin Synthesis and Secretion in Pancreatic {beta}-Cells.

    Zhang L, Lai E, Teodoro T and Volchuk A

    Division of Cell and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, Ontario M5G 1L7, Canada.

    Chronic hyperglycemia contributes to pancreatic beta-cell dysfunction during the development of type 2 diabetes. Treatment of pancreatic beta-cells with prolonged high glucose concentrations has been shown to reduce insulin promoter activity and insulin gene expression. Here, we examined the effect of high glucose on endoplasmic reticulum (ER) stress pathway activation and insulin production in INS-1 832/13 pancreatic beta-cells. Treatment of cells with 25 mm glucose for 24-48 h decreased insulin mRNA and protein levels and reduced the proinsulin translation rate, which was accompanied by enhanced unfolded protein response pathway activation (XBP-1 mRNA splicing and increased phospho-eIF2alpha, CHOP, and active ATF6 levels). Overexpressing the ER chaperone GRP78 partially rescued high glucose-induced suppression of proinsulin levels and improved glucose-stimulated insulin secretion with no effect on insulin 2 mRNA levels. Under these conditions, there was little effect of GRP78 overexpression on ER stress markers. Knockdown of GRP78 expression under basal glucose conditions reduced cellular insulin levels and glucose-stimulated insulin secretion. Thus, GRP78 is essential for insulin biosynthesis, and enhancing chaperone capacity can improve beta-cell function in the presence of prolonged hyperglycemia. In contrast, overexpression of the ER chaperone and oxidoreductase protein-disulfide isomerase (PDI) reduced glucose-stimulated insulin secretion and induced ER stress resulting from the accumulation of proinsulin in the ER. These results suggest a role for both GRP78 and PDI in insulin biosynthesis, although an excess of PDI disrupts normal proinsulin processing.

    The Journal of biological chemistry 

  • Down-regulation of BiP/GRP78 sensitizes resistant prostate cancer cells to gene-therapeutic overexpression of REIC/Dkk-3.

    Tanimoto R, Sakaguchi M, Abarzua F, Kataoka K, Kurose K, Murata H, Nasu Y, Kumon H and Huh NH

    Department of Cell Biology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan.

    We have recently shown that an adenovirus carrying REIC/Dkk-3 (Ad-REIC) exhibits a potent tumor-specific cell-killing function for various human cancers. It has also become evident that some human cancers are resistant to Ad-REIC-induced apoptosis. The aim of the present study was to determine the molecular mechanisms of resistance to Ad-REIC. First, we isolated resistant clones from a human prostate cancer cell line, PC3, after repeated exposure to Ad-REIC. Infection efficiency of the adenovirus vector and expression level of REIC/Dkk-3 in the resistant clones were similar to those in the parental PC3 cells. By screening for alteration in levels and functional status of proteins involved in Ad-REIC-induced apoptosis, we found that BiP/GRP78, an ER-residing chaperone protein, was expressed at higher levels consistently among resistant cells. Expression levels of BiP and rates of apoptosis induced by Ad-REIC were inversely correlated. Down-regulation of BiP with siRNA sensitized the resistant cells to Ad-REIC in vivo as well as in culture. These results indicate that BiP is a major determinant of resistance to Ad-REIC-induced apoptosis. Thus BiP is useful for diagnosis of inherent and acquired resistance of cancers and also as a target molecule to overcome resistance to the gene therapeutic Ad-REIC.

    International journal of cancer 2010;126;7;1562-9

  • Essential role of the unfolded protein response regulator GRP78/BiP in protection from neuronal apoptosis.

    Wang M, Ye R, Barron E, Baumeister P, Mao C, Luo S, Fu Y, Luo B, Dubeau L, Hinton DR and Lee AS

    Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9176, USA.

    Neurodegenerative diseases are often associated with dysfunction in protein quality control. The endoplasmic reticulum (ER), a key site for protein synthesis, senses stressful conditions by activating the unfolded protein response (UPR). In this study we report the creation of a novel mouse model in which GRP78/BiP, a major ER chaperone and master regulator of UPR, is specifically eliminated in Purkinje cells (PCs). GRP78-depleted PCs activate UPR including the induction of GRP94, PDI, CHOP and GADD34, feedback suppression of eIF2alpha phosphorylation and apoptotic cell death. In contrast to current models of protein misfolding in which an abnormal accumulation of ubiquitinated protein is prominent, cytosolic ubiquitin staining is dramatically reduced in GRP78-null PCs. Ultrastructural evaluation reveals that the ER shows prominent dilatation with focal accumulation of electron-dense material within the ER. The mice show retarded growth and severe motor coordination defect by week 5 and cerebellar atrophy by week 13. Our studies uncover a novel link between GRP78 depletion and reduction in cytosolic ubiquitination and establish a novel mouse model of accelerated cerebellar degeneration with basic and clinical applications.

    Funded by: NCI NIH HHS: R01 CA027607, R01 CA027607-29, R01 CA111700, R01 CA111700-04, R01-CA027607, R01-CA111700

    Cell death and differentiation 2010;17;3;488-98

  • Lactate dehydrogenase 5 expression in melanoma increases with disease progression and is associated with expression of Bcl-XL and Mcl-1, but not Bcl-2 proteins.

    Zhuang L, Scolyer RA, Murali R, McCarthy SW, Zhang XD, Thompson JF and Hersey P

    Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Sydney, NSW, Australia.

    The serum level of lactate dehydrogenase (LDH) is an important predictor of prognosis and treatment response in melanoma patients. It is unknown whether the expression of LDH-5 in tissue sections also has prognostic significance and whether it is related to the expression of the anti-apoptotic proteins, Bcl-2, Bcl-XL and Mcl-1, and endoplasmic reticulum stress protein glucose-regulated protein 78 (GRP78). Identification of an association between LDH-5 expression and anti-apoptotic proteins may have important therapeutic implications for melanoma patients. Sections from 159 pigmented lesions, including nevi and melanoma at different stages of progression were studied by immunohistochemistry. Correlation of LDH-5 expression with clinicopathological factors and with the expression of Bcl-2, Bcl-XL, Mcl-1 and GRP78 was examined. LDH-5 was detected at low levels in 6 of 10 compound nevi (60%) and 6 of 10 dysplastic nevi (60%). The percentage of positive cases was greater in thin (<or=1.0 mm) (74%) and thick primary melanoma (>1.0 mm) (95%) and in metastatic melanoma in the skin (100%) and lymph node (81%). The immunoreactive score was highly related to progression of melanoma (P<0.0001). LDH-5 expression was positively associated with increasing tumor thickness (P=0.02) and dermal tumor mitotic rate (P=0.02). LDH-5 above the median immunoreactive score was associated with reduced disease-free survival and overall survival (P<0.02). LDH-5 expression was negatively associated with Bcl-2 expression. In contrast, LDH-5 expression was strongly associated with Bcl-XL and Mcl-1 expression and also positively associated with GRP78 expression (P<0.0001). The low Bcl-2 expression in melanomas with high LDH-5 expression provides an explanation for the poor response of patients with high serum LDH levels to treatment with the Bcl-2 antisense drug 'Genasense'. The strong correlation of LDH-5 expression with Mcl-1 expression suggests that treatment strategies inhibiting the activity of Mcl-1 in melanoma patients should be investigated.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2010;23;1;45-53

  • N-acetyl cysteine and penicillamine induce apoptosis via the ER stress response-signaling pathway.

    Guan D, Xu Y, Yang M, Wang H, Wang X and Shen Z

    Department of Biochemistry and Molecular Biology, Fudan University, Shanghai, China.

    N-acetyl cysteine (NAC) and penicillamine (PEN) have been shown to induce apoptosis in multiple types of human cancer cells; however, the molecular mechanism underlying this activity is unclear. This study was designed to identify the genes responsible for apoptosis induction by NAC and PEN. We found that glucose-regulated protein 78 (GRP78) was upregulated in HeLa cells following treatment with NAC or PEN. GRP78 is a central regulator of endoplasmic reticulum (ER) stress and has been used as a marker of ER stress. Additionally, both the activating transcription factor 6 (ATF6) protein and X box-binding protein 1 (XBP1) mRNA were processed, which facilitates the expression of C/EBP homologous protein (CHOP), a key-signaling component of ER stress-induced apoptosis. Furthermore, the PERK-ATF4 pathway, which also induces the expression of CHOP, was activated in NAC-treated cells. The role of the ER stress pathway was further confirmed through the small interfering RNA (siRNA)-mediated knockdown of CHOP, which attenuated NAC and PEN-induced apoptosis. These results demonstrate that NAC- and PEN-induced apoptosis in HeLa cells is mediated by the ER stress pathway.

    Molecular carcinogenesis 2010;49;1;68-74

  • Patterns of GRP78 and MTJ1 expression in primary cutaneous malignant melanoma.

    Papalas JA, Vollmer RT, Gonzalez-Gronow M, Pizzo SV, Burchette J, Youens KE, Johnson KB and Selim MA

    Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA. papal002@mc.duke.edu

    Cell surface expression of glucose-regulated protein 78 (GRP78) occurs in several types of cancer; however, its role in the behavior of primary cutaneous melanoma is not well studied. The association of cell surface GRP78 with other proteins such as MTJ1 stimulates cell proliferation. In this study, we characterized the pattern of expression of GRP78 and MTJ1 in invasive primary cutaneous melanomas and analyzed the relationships between the pattern of expression and various clinicopathological parameters. We found two patterns of GRP78 expression in invasive primary cutaneous melanoma. One pattern showed a gradual fading of protein expression from superficial to deeper levels within the same tumor. The second pattern of expression showed a similar fading with an abrupt regaining of expression at the deep invasive edge of the melanoma. These two distinct patterns of GRP78 expression correlated with both patient survival and depth of tumor invasion. A moderate MTJ1 expression was found to be associated with decreased patient survival; however, no significant associations were observed between patterns of GRP78 and MTJ1 expression. Our study (1) describes two distinct patterns of GRP78 in invasive primary cutaneous melanoma, (2) inversely correlates regain of GRP78 expression with patient survival, and (3) suggests a modifying effect of MTJ1 on GRP78 in enhancing tumor aggressiveness.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2010;23;1;134-43

  • Proteomic analysis of cell lines expressing small hepatitis B surface antigen revealed decreased glucose-regulated protein 78 kDa expression in association with higher susceptibility to apoptosis.

    Zhao C, Zhang W, Tian X, Fang C, Lu H, Yuan Z, Yang P and Wen Y

    Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Institute of Biomedical Sciences, Fudan University, Shanghai, China.

    Accumulating evidence suggests a key role of hepatocyte apoptosis in the pathogenesis of viral hepatitis B. It was found in this study that stable expression of small hepatitis B surface antigen (SHBs) in HepG2 and Huh7 cells increased susceptibility to apoptosis. Proteomic analysis of SHBs expressing HepG2 cells revealed 43 down-regulated and 38 up-regulated proteins. Some have been implicated in apoptosis, including glucose-regulated protein 78 kDa (GRP78), heterogeneous nuclear ribonucleoprotein H3 (hnRNP H), Rho GDP dissociation inhibitor (GDI), cystatin B, far upstream element-binding protein (FUSEbp), and TNF receptor-associated protein 1 (TRAP1). Differential expression of GRP78 and several other proteins was confirmed by Western blot analysis. Replenishing GRP78 improved cellular resistance to apoptosis, whereas reduction of GRP78 by siRNA increased susceptibility even in the absence of SHBs. Taken together, these results suggest that HBsAg plays a pro-apoptotic role through down-regulation of GRP78.

    Journal of medical virology 2010;82;1;14-22

  • Hyperoxia augments ER-stress-induced cell death independent of BiP loss.

    Gewandter JS, Staversky RJ and O'Reilly MA

    Department of Biochemistry and Biophysics, The University of Rochester, Rochester, NY 14642, USA.

    Cytotoxic reactive oxygen species are constantly formed as a by-product of aerobic respiration and are thought to contribute to aging and disease. Cells respond to oxidative stress by activating various pathways, whose balance is important for adaptation or induction of cell death. Our lab recently reported that BiP (GRP78), a proposed negative regulator of the unfolded protein response (UPR), declines during hyperoxia, a model of chronic oxidative stress. Here, we investigate whether exposure to hyperoxia, and consequent loss of BiP, activates the UPR or sensitizes cells to ER stress. Evidence is provided that hyperoxia does not activate the three ER stress receptors IRE1, PERK, and ATF6. Although hyperoxia alone did not activate the UPR, it sensitized cells to tunicamycin-induced cell death. Conversely, overexpression of BiP did not block hyperoxia-induced ROS production or increased sensitivity to tunicamycin. These findings demonstrate that hyperoxia and loss of BiP alone are insufficient to activate the UPR. However, hyperoxia can sensitize cells to toxicity from unfolded proteins, implying that chronic ROS, such as that seen throughout aging, could augment the UPR and, moreover, suggesting that the therapeutic use of hyperoxia may be detrimental for lung diseases associated with ER stress.

    Funded by: NHLBI NIH HHS: HL-66988, HL-67392, R01 HL067392, R01 HL067392-07, T32 HL066988, T32 HL066988-09; NIEHS NIH HHS: ES-01247, P30 ES001247, P30 ES001247-359022

    Free radical biology & medicine 2009;47;12;1742-52

  • Glucose-regulated protein 78: a new partner of p53 in trophoblast.

    Arnaudeau S, Arboit P, Bischof P, Shin-ya K, Tomida A, Tsuruo T, Irion O and Cohen M

    Bioimaging Core Facility, University Medical Center, Geneva University, Geneva, Switzerland.

    Although wild-type p53 protein is overexpressed in first trimester trophoblast, it is inactive towards its target genes Metalloproteinase 2 and 9. This seems to be due to a complex mechanism of inactivation and stabilization of p53 relying on the formation of protein complexes involving the N-terminus of p53. To detect the proteins associated with this sequence, we incubated biotinylated p53 N-terminal peptide in cytotrophoblastic cell medium 24 h before lysis of cells. We purified the proteins retained on biotinylated peptide using a neutravidin affinity column. Proteins were then identified by peptide mass finger printing followed or not by peptide fragmentation sequencing. Among these proteins, we identified glucose-regulated protein 78 (GRP78) and verified its interaction with p53 in trophoblastic cells by immunoprecipitation and Western blot analysis. Moreover, the decreased expression of GRP78 induced by GRP78siRNA or versipelostatin decreased the formation of high molecular weight p53 complexes and p53 monomer and increased trophoblastic invasion. These results suggest that GRP78 is involved in inactivation and stabilization of p53 and in the regulation of trophoblastic invasion.

    Proteomics 2009;9;23;5316-27

  • Molecular chaperone BiP interacts with Borna disease virus glycoprotein at the cell surface.

    Honda T, Horie M, Daito T, Ikuta K and Tomonaga K

    partment of Virology, Research Institute for Microbial Diseases (BIKEN), Osaka University, Suita, Osaka 565-0871, Japan.

    Borna disease virus (BDV) is characterized by highly neurotropic infection. BDV enters its target cells using virus surface glycoprotein (G), but the cellular molecules mediating this process remain to be elucidated. We demonstrate here that the N-terminal product of G, GP1, interacts with the 78-kDa chaperone protein BiP. BiP was found at the surface of BDV-permissive cells, and anti-BiP antibody reduced BDV infection as well as GP1 binding to the cell surface. We also reveal that BiP localizes at the synapse of neurons. These results indicate that BiP may participate in the cell surface association of BDV.

    Journal of virology 2009;83;23;12622-5

  • The endoplasmic reticulum chaperone BiP/GRP78 is important in the structure and function of the human cytomegalovirus assembly compartment.

    Buchkovich NJ, Maguire TG, Paton AW, Paton JC and Alwine JC

    Department of Cancer Biology, Abramson Family Cancer Research Institute, Cell and Molecular Biology Graduate Group, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6142, USA.

    Funded by: NCI NIH HHS: R01 CA028379, R01 CA028379-29, T32 CA115299, T32 CA115299-02

    Journal of virology 2009;83;22;11421-8

  • Genetic polymorphisms and haplotype structures of HSPA5 gene in the Han population of Southern China.

    Zhu X, Cheng J, Zhao J, Chen L, Hou S, Zhao G, Lan F, Wang W, Kung H and He M

    Shenzhen Center for Disease Control and Prevention, Shenzhen, PR China.

    The heat shock 70 kDa protein 5 (HSPA5) gene is known to be involved in stress-associated diseases. In this study, the promoter, exons, 3' untranslated region (3'UTR), and subtotal introns of the HSPA5 gene were sequenced in a sub-population of 161 healthy Han Chinese. Nine single-nucleotide polymorphisms (SNPs) including a new one (-86bp T > A from the estimated translation start site) were found and 15 haplotypes (frequencies > 1%) were inferred. Polymorphisms rs391957 and rs11355458 were completely linked in our population (r (2) = 1.00). Using this information, fellow scientists may be able to decrease the number of SNPs to be genotyped in future disease case-control studies.

    Tissue antigens 2009;74;5;420-3

  • Glucose-regulated protein 78 is an intracellular antiviral factor against hepatitis B virus.

    Yu J, Chan HL, Chen YC, Wang H, Chen Y, Chan CY, Go MY, Tsai SN, Ngai SM, To KF, Tong JH, He QY, Sung JJ, Kung HF, Cheng CH and He ML

    Stanley Ho Center for Emerging Infectious Diseases, School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China.

    Hepatitis B virus (HBV) infection is a global public health problem that plays a crucial role in the pathogenesis of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. However, the pathogenesis of HBV infection and the mechanisms of host-virus interactions are still elusive. In this study, two-dimensional gel electrophoresis and mass spectrometry-based comparative proteomics were applied to analyze the host response to HBV using an inducible HBV-producing cell line, HepAD38. Twenty-three proteins were identified as differentially expressed with glucose-regulated protein 78 (GRP78) as one of the most significantly up-regulated proteins induced by HBV replication. This induction was further confirmed in both HepAD38 and HepG2 cells transfected with HBV-producing plasmids by real time RT-PCR and Western blotting as well as in HBV-infected human liver biopsies by immunohistochemistry. Knockdown of GRP78 expression by RNA interference resulted in a significant increase of both intracellular and extracellular HBV virions in the transient HBV-producing HepG2 cells concomitant with enhanced levels of hepatitis B surface antigen and e antigen in the culture medium. Conversely overexpression of GRP78 in HepG2 cells led to HBV suppression concomitant with induction of the positive regulatory circuit of GRP78 and interferon-beta1 (IFN-beta1). In this connection, the IFN-beta1-mediated 2',5'-oligoadenylate synthetase and RNase L signaling pathway was noted to be activated in GRP78-overexpressing HepG2 cells. Moreover GRP78 was significantly down-regulated in the livers of chronic hepatitis B patients after effective anti-HBV treatment (p = 0.019) as compared with their counterpart pretreatment liver biopsies. In conclusion, the present study demonstrates for the first time that GRP78 functions as an endogenous anti-HBV factor via the IFN-beta1-2',5'-oligoadenylate synthetase-RNase L pathway in hepatocytes. Induction of hepatic GRP78 may provide a novel therapeutic approach in treating HBV infection.

    Molecular & cellular proteomics : MCP 2009;8;11;2582-94

  • GRP-78 secreted by tumor cells blocks the antiangiogenic activity of bortezomib.

    Kern J, Untergasser G, Zenzmaier C, Sarg B, Gastl G and Steurer M

    Tumor Biology & Angiogenesis Laboratory, Department of Internal Medicine V, Innsbruck Medical University, Innsbruck, Austria.

    Antiangiogenic effects of the proteasome inhibitor bortezomib were analyzed on tumor xenografts in vivo. Bortezomib strongly inhibited angiogenesis and vascularization in the chicken chorioallantoic membrane. Bortezomib's inhibitory effects on chorioallantoic membrane vascularization were abrogated in the presence of distinct tumor xenografts, thanks to a soluble factor secreted by tumor cells. Through size-exclusion and ion-exchange chromatography as well as mass spectroscopy, we identified GRP-78, a chaperone protein of the unfolded protein response, as being responsible for bortezomib resistance. Indeed, a variety of bortezomib-resistant solid tumor cell lines (PC-3, HRT-18), but not myeloma cell lines (U266, OPM-2), were able to secrete high amounts of GRP-78. Recombinant GRP-78 conferred bortezomib resistance to endothelial cells and OPM-2 myeloma cells. Knockdown of GRP78 gene expression in tumor cells and immunodepletion of GRP-78 protein from tumor cell supernatants restored bortezomib sensitivity. GRP-78 did not bind or complex bortezomib but induced prosurvival signals by phosphorylation of extracellular signal-related kinase and inhibited p53-mediated expression of proapoptotic Bok and Noxa proteins in endothelial cells. From our data, we conclude that distinct solid tumor cells are able to secrete GRP-78 into the tumor microenvironment, thus demonstrating a hitherto unknown mechanism of resistance to bortezomib.

    Blood 2009;114;18;3960-7

  • A new polymorphism in the GRP78 is not associated with HBV invasion.

    Zhu X, Wang Y, Tao T, Li DP, Lan FF, Zhu W, Xie D and Kung HF

    Institute of Oncology, Affiliated Tumor Hospital of Guangzhou Medical College, Guangzhou 510095, Guangdong Province, China.

    Aim: To examine the association between -86 bp (T > A) in the glucose-regulated protein 78 gene (GRP78) and hepatitis B virus (HBV) invasion.

    Methods: DNA was genotyped for the single-nucleotide polymorphism by polymerase chain reaction followed by sequencing in a sample of 382 unrelated HBV carriers and a total of 350 sex- and age-matched healthy controls. Serological markers for HBV infection were determined by enzyme-linked immunosorbent assay kits or clinical chemistry testing.

    Results: The distributions of allelotype and genotype in cases were not significantly different from those in controls. In addition, our findings suggested that neither alanine aminotransferase/hepatitis B e antigen nor HBV-DNA were associated with the allele/genotype variation in HBV infected individuals.

    Conclusion: -86 bp T > A polymorphism in GRP78 gene is not related to the clinical risk and acute exacerbation of HBV invasion.

    World journal of gastroenterology 2009;15;39;4958-61

  • Advanced osteoarthritis in humans is associated with altered collagen VI expression and upregulation of ER-stress markers Grp78 and bag-1.

    Nugent AE, Speicher DM, Gradisar I, McBurney DL, Baraga A, Doane KJ and Horton WE

    Northeastern Ohio Universities Colleges of Medicine and Pharmacy, Rootstown, OH 44272, USA. anugent@neoucom.edu

    To test the hypothesis that a perturbation of endoplasmic reticulum (ER) function is involved in the pathogenesis of osteoarthritis (OA), articular cartilage was isolated from non-OA patients secondary to resection of osteo- or chondrosarcomas. Intra-joint samples of minimal and advanced osteoarthritic cartilage were isolated from patients undergoing total knee arthroplasty and scored for disease severity. Glucose-regulated protein-78 (grp78) and bcl-2-associated athanogene-1 (bag-1) were detected via immunofluorescence as markers of non-homeostatic ER function. Additionally, the expression of type VI collagen and its integrin receptor, NG2, was determined to examine cartilage matrix health and turnover. There was an upregulation of grp78 in advanced OA, and variable expression in minimal OA. Non-OA cartilage was consistently grp78 negative. The downstream regulator bag-1 was also upregulated in OA compared with normal cartilage. Collagen VI was mainly cell-associated in non-OA cartilage, with a more widespread distribution observed in OA cartilage along with increased intracellular staining intensity. The collagen VI integral membrane proteoglycan receptor NG2 was downregulated in advanced OA compared with its patient-matched minimally involved cartilage sample. These results suggest that chondrocytes exhibit ER stress during OA, in association with upregulation of a large secreted molecule, type VI collagen.

    The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 2009;57;10;923-31

  • Single nucleotide polymorphism of rs430397 in the fifth intron of GRP78 gene and clinical relevance of primary hepatocellular carcinoma in Han Chinese: risk and prognosis.

    Zhu X, Chen MS, Tian LW, Li DP, Xu PL, Lin MC, Xie D and Kung HF

    State Key Laboratory of Oncology in South China, Cancer Center, Sun Yat-sen University, Guangzhou, People's Republic of China.

    Large number of data showed that allele variants in certain genes are markers for hepatocellular carcinoma (HCC). GRP78 is a stress-associated protein which is a central regulator of endoplasmic reticulum homeostasis due to its multiple functional roles in the folding, maturation and transport of proteins. A case-control study was conducted on 576 HCC patients, and 539 age- and gender-matched healthy subjects to examine whether rs430397 polymorphism in the fifth intron of GRP78 gene is associated with the development and prognosis of HCC. Polymorphism in rs430397 was analyzed by resequencing and TaqMan real-time PCR. Allele A, genotype AA and combined genotypes (AG+AA) displayed significantly increased risk for HCC (OR = 1.48, 95%CI = 1.07-1.79, p = 0.010; OR = 2.25, 95%CI = 1.08-3.38, p = 0.019; and OR = 1.50, 95%CI = 1.09-1.85, p = 0.012, respectively). Genotypes AA and AG were mainly associated with HBV-related HCC (85.8%; p < 0.00001 versus HBV noncarriers with HCC) and cirrhosis-related HCC (90%; p = 0.011 versus noncirrhosis HCC). Patients carrying the AA genotype had a shorter survival time (median 23.0 months in all cases; median 21.0 months in the cases carrying HBsAg). Like HBV and cirrhosis, the rs430397 is an independent prognostic factor influencing the survival of HCC. In conclusion, allele A and genotypes AA and AG of rs430397 may represent high risk and poor prognosis for HCC.

    International journal of cancer 2009;125;6;1352-7

  • Expression patterns of Trk-A, Trk-B, GRP78, and p75NRT in olfactory neuroblastoma.

    Weinreb I, Goldstein D, Irish J and Perez-Ordonez B

    Department of Pathology, University Health Network, Toronto, Ontario, Canada. weinrebi@yahoo.ca

    Olfactory neuroblastoma is an uncommon neuroectodermal tumor of the sinonasal tract. It represents 2% to 3% of sinonasal neoplasms. Most olfactory neuroblastoma behave locally aggressive with 30% recurrence rates. A subset metastasizes to lymph nodes and/or distant sites. Grading of olfactory neuroblastoma involves a combination of factors with low-grade tumors having better survival than high-grade tumors. The grade does not always predict prognosis, however, as metastases can be seen in all grades of olfactory neuroblastoma. Trk-A, Trk-B, and p75NRT are neurotrophin receptors associated with numerous solid malignancies, particularly pediatric neuroblastoma. GRP78 is an endoplasmic reticulum protein, associated with differentiation of neuroblastic cells. Trk-A, p75NRT, and GRP78 overexpression are favorable prognostic factors in pediatric neuroblastoma, whereas Trk-B is associated with a poorer prognosis in these tumors. Olfactory neuroblastoma is clinically distinct from pediatric neuroblastoma but shares some histological features. Trk-A and p75NRT have been demonstrated in olfactory neuroblastoma previously. Trk-B and GRP78 have not been investigated in olfactory neuroblastoma. None of these markers have been correlated with grade or outcome in olfactory neuroblastoma. To investigate the role of Trk-A, Trk-B, p75NRT, and GRP78, a series of 20 olfactory neuroblastomas was stained with these antibodies. Trk-A and Trk-B stained most cases of olfactory neuroblastoma (90% and 85%). GRP78 stained most cases (90%), although weakly. P75NRT demonstrated focal membranous staining in a sustentacular pattern (60%). None of these markers correlated with Hyams grade. None of these markers definitively correlated with patient outcome. Neurotrophin receptors do not appear to have a prognostic role; however, Trk's may play an oncogenic role in olfactory neuroblastoma.

    Human pathology 2009;40;9;1330-5

  • GRP78 as a marker of pre-eclampsia: an exploratory study.

    Laverrière A, Landau R, Charvet I, Irion O, Bischof P, Morales M and Cohen M

    Laboratoire d'Hormonologie, Department of Obstetrics and Gynaecology, Maternity, University of Geneva, 1211 Geneva 14, Switzerland.

    Although the exact mechanisms that lead to shallow invasion or defective trophoblastic differentiation in pre-eclampsia are still unknown, it is widely admitted that the etiology of pre-eclampsia is a defect in trophoblast invasion of the uterine spiral arteries. We have previously observed that the status of a chaperone protein, glucose regulated protein 78 (GRP78) is associated with the invasive properties of cytotrophoblastic cells; we therefore hypothesized that circulating GRP78 could serve as a diagnostic tool in pre-eclampsia. In a prospective case-control study, we quantified GRP78 autoantibodies, complexes of GRP78 with autoantibodies and GRP78 (C-term fragment, N-term fragment and full-length GRP78) by ELISA. Plasma from women diagnosed with pre-eclampsia (n = 16), from women during the first trimester of pregnancy who subsequently developed pre-eclampsia (n = 10) and from healthy pregnant women (controls, n = 58 at term, n = 26 at first trimester) were analysed and compared. We observed no significant difference between pre-eclamptic and healthy pregnant women for autoantibodies-GRP78 complexes or total GRP78 at both first trimester and at delivery. In contrast, the ratio of C-terminal GRP78 over full length GRP78 was significantly different in plasma of pre-eclamptic patients as compared with controls both during first trimester (P < 0.004) and at term (P < 0.0001). Our findings suggest that circulating C-terminal GRP78 reflect the invasive properties of cells, and could be used as a predictive marker for pre-eclampsia early in pregnancy.

    Molecular human reproduction 2009;15;9;569-74

  • Regulation of PERK signaling and leukemic cell survival by a novel cytosolic isoform of the UPR regulator GRP78/BiP.

    Ni M, Zhou H, Wey S, Baumeister P and Lee AS

    Department of Biochemistry and Molecular Biology and the USC/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America.

    The unfolded protein response (UPR) is an evolutionarily conserved mechanism to allow cells to adapt to stress targeting the endoplasmic reticulum (ER). Induction of ER chaperone GRP78/BiP increases protein folding capacity; as such it represents a major survival arm of UPR. Considering the central importance of the UPR in regulating cell survival and death, evidence is emerging that cells evolve feedback regulatory pathways to modulate the key UPR executors, however, the precise mechanisms remain to be elucidated. Here, we report the fortuitous discovery of GRP78va, a novel isoform of GRP78 generated by alternative splicing (retention of intron 1) and alternative translation initiation. Bioinformatic and biochemical analyses revealed that expression of GRP78va is enhanced by ER stress and is notably elevated in human leukemic cells and leukemia patients. In contrast to the canonical GRP78 which is primarily an ER lumenal protein, GRP78va is devoid of the ER signaling peptide and is cytosolic. Through specific knockdown of endogenous GRP78va by siRNA without affecting canonical GRP78, we showed that GRP78va promotes cell survival under ER stress. We further demonstrated that GRP78va has the ability to regulate PERK signaling and that GRP78va is able to interact with and antagonize PERK inhibitor P58(IPK). Our study describes the discovery of GRP78va, a novel cytosolic isoform of GRP78/BiP, and the first characterization of the modulation of UPR signaling via alternative splicing of nuclear pre-mRNA. Our study further reveals a novel survival mechanism in leukemic cells and other cell types where GRP78va is expressed.

    Funded by: NCI NIH HHS: R01 CA027607, R01 CA111700

    PloS one 2009;4;8;e6868

  • The tumor suppressor Par-4 activates an extrinsic pathway for apoptosis.

    Burikhanov R, Zhao Y, Goswami A, Qiu S, Schwarze SR and Rangnekar VM

    Department of Radiation Medicine, University of Kentucky, Lexington, KY 40536, USA.

    Prostate apoptosis response-4 (Par-4) is a proapoptotic protein with intracellular functions in the cytoplasm and nucleus. Unexpectedly, we noted Par-4 protein is spontaneously secreted by normal and cancer cells in culture, and by Par-4 transgenic mice that are resistant to spontaneous tumors. Short exposure to endoplasmic reticulum (ER) stress-inducing agents further increased cellular secretion of Par-4 by a brefeldin A-sensitive pathway. Secretion occurred independently of caspase activation and apoptosis. Interestingly, extracellular Par-4 induced apoptosis by binding to the stress response protein, glucose-regulated protein-78 (GRP78), expressed at the surface of cancer cells. The interaction of extracellular Par-4 and cell surface GRP78 led to apoptosis via ER stress and activation of the FADD/caspase-8/caspase-3 pathway. Moreover, apoptosis inducible by TRAIL, which also exerts cancer cell-specific effects, is dependent on extracellular Par-4 signaling via cell surface GRP78. Thus, Par-4 activates an extrinsic pathway involving cell surface GRP78 receptor for induction of apoptosis.

    Funded by: NCI NIH HHS: CA105453, CA60872, CA84511, R01 CA060872, R01 CA060872-11, R01 CA084511, R01 CA105453, R01 CA105453-05, R01 CA116658, R01 CA116658-04

    Cell 2009;138;2;377-88

  • Knockdown of ERp57 increases BiP/GRP78 induction and protects against hyperoxia and tunicamycin-induced apoptosis.

    Xu D, Perez RE, Rezaiekhaligh MH, Bourdi M and Truog WE

    Section of Neonatal-Perinatal Medicine, Department of Pediatrics, Neonatology Research Laboratory, Children's Mercy Hospitals and Clinics, University of Missouri-Kansas City School of Medicine, Kansas City, Missouri 64108, USA. xud@umkc.edu

    Supplemental oxygen therapy (hyperoxia) in preterm babies with respiratory stress is associated with lung injury and the development of bronchopulmonary dysplasia. Endoplasmic reticulum (ER) homeostasis plays critical roles in maintaining cellular functions such as protein synthesis, folding, and secretion. Interruption of ER homeostasis causes ER stress and triggers the unfolded protein response, which can lead to apoptosis in persistently stressed cells. ERp57 is an ER protein and is associated with calreticulin and calnexin in protein glycosylation. In this study, we found hyperoxia downregulated ERp57 in neonatal rat lungs and cultured human endothelial cells. Transient transfection of ERp57 small interfering RNA significantly knocked down ERp57 expression and reduced hyperoxia- or tunicamycin-induced apoptosis in human endothelial cells. Apoptosis was decreased from 26.8 to 9.9% in hyperoxia-exposed cells and from 37.8 to 5.0% in tunicamycin-treated cells. The activation of caspase-3 induced by hyperoxia or tunicamycin was diminished and immunoglobulin heavy chain-binding protein/glucose-regulated protein 78-kDa (BiP/GRP78) induction was increased in ERp57 knockdown cells. Overexpression of ERp57 exacerbated hyperoxia- or tunicamycin-induced apoptosis in human endothelial cells. Apoptosis was increased from 10.1 to 14.3% in hyperoxia-exposed cells and from 14.0 to 21.2% in tunicamycin-treated cells. Overexpression of ERp57 also augmented tunicamycin-induced caspase-3 activation and reduced BiP/GRP78 induction. Our results demonstrate that ERp57 can regulate apoptosis in human endothelial cells. It appears that knockdown of ERp57 confers cellular protection against hyperoxia- or tunicamycin-induced apoptosis by inhibition of caspase-3 activation and stimulation of BiP/GRP78 induction.

    American journal of physiology. Lung cellular and molecular physiology 2009;297;1;L44-51

  • Blockade of Cripto binding to cell surface GRP78 inhibits oncogenic Cripto signaling via MAPK/PI3K and Smad2/3 pathways.

    Kelber JA, Panopoulos AD, Shani G, Booker EC, Belmonte JC, Vale WW and Gray PC

    Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.

    Cripto is a developmental oncoprotein that signals via mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/Akt and Smad2/3 pathways. However, the molecular basis for Cripto coupling to these pathways during embryogenesis and tumorigenesis is not fully understood. In this regard, we recently demonstrated that Cripto forms a cell surface complex with the HSP70 family member glucose-regulated protein-78 (GRP78). Here, we provide novel functional evidence demonstrating that cell surface GRP78 is a necessary mediator of Cripto signaling in human tumor, mammary epithelial and embryonic stem cells. We show that targeted disruption of the cell surface Cripto/GRP78 complex using shRNAs or GRP78 immunoneutralization precludes Cripto activation of MAPK/PI3K pathways and modulation of activin-A, activin-B, Nodal and transforming growth factor-beta1 signaling. We further demonstrate that blockade of Cripto binding to cell surface GRP78 prevents Cripto from increasing cellular proliferation, downregulating E-Cadherin, decreasing cell adhesion and promoting pro-proliferative responses to activin-A and Nodal. Thus, disrupting the Cripto/GRP78 binding interface blocks oncogenic Cripto signaling and may have important therapeutic value in the treatment of cancer.

    Funded by: NCI NIH HHS: R01 CA107420, R01 CA107420-04, R01 CA107420-05, R01CA107420, T32 CA009370

    Oncogene 2009;28;24;2324-36

  • Activation of the unfolded protein response is associated with favorable prognosis in acute myeloid leukemia.

    Schardt JA, Weber D, Eyholzer M, Mueller BU and Pabst T

    Departments of Medical Oncology and Clinical Research, University Hospital Bern, Bern, Switzerland.

    Purpose: The unfolded protein response is triggered by the accumulation of misfolded proteins within the endoplasmic reticulum. Previous studies suggest that the unfolded protein response is activated in some cancer cell lines and involved in tumor development. The role of the unfolded protein response during leukemogenesis is unknown thus far.

    Here, we assessed the induction of key effectors of the unfolded protein response in leukemic cells at diagnosis of 105 acute myeloid leukemia (AML) patients comprising all subtypes. We determined the formation of the spliced variant of the X-box-binding protein 1 (XBP1) mRNA, as well as expression levels of calreticulin, GRP78, and CHOP mRNA.

    Results: The formation of the spliced variant of XBP1s was detectable in 16.2% (17 of 105) of AML patients. Consistent with activated unfolded protein response, this group also had significantly increased expression of calreticulin, GRP78, and CHOP. AML patients with activated unfolded protein response had lower WBC counts, lactate dehydrogenase levels, and more frequently, secondary AML. The incidence of fms-related tyrosine kinase 3 (FLT3) mutations was significantly lower in patients with activated unfolded protein response. In addition, an association was observed between activated unfolded protein response and deletion of chromosome 7. Finally, the clinical course of AML patients with activated unfolded protein response was more favorable with lower relapse rate (P = 0.0182) and better overall (P = 0.041) and disease-free survival (P = 0.022).

    Conclusions: These results suggest that the unfolded protein response is activated in a considerable subset of AML patients. AML patients with activated unfolded protein response present specific clinical characteristics and a more favorable course of the disease.

    Clinical cancer research : an official journal of the American Association for Cancer Research 2009;15;11;3834-41

  • Functions and pathologies of BiP and its interaction partners.

    Dudek J, Benedix J, Cappel S, Greiner M, Jalal C, Müller L and Zimmermann R

    Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany.

    The endoplasmic reticulum (ER) is involved in a variety of essential and interconnected processes in human cells, including protein biogenesis, signal transduction, and calcium homeostasis. The central player in all these processes is the ER-lumenal polypeptide chain binding protein BiP that acts as a molecular chaperone. BiP belongs to the heat shock protein 70 (Hsp70) family and crucially depends on a number of interaction partners, including co-chaperones, nucleotide exchange factors, and signaling molecules. In the course of the last five years, several diseases have been linked to BiP and its interaction partners, such as a group of infectious diseases that are caused by Shigella toxin producing E. coli. Furthermore, the inherited diseases Marinesco-Sjögren syndrome, autosomal dominant polycystic liver disease, Wolcott-Rallison syndrome, and several cancer types can be considered BiP-related diseases. This review summarizes the physiological and pathophysiological characteristics of BiP and its interaction partners.

    Cellular and molecular life sciences : CMLS 2009;66;9;1556-69

  • Involvement of GRP78 in inhibition of HBV secretion by Boehmeria nivea extract in human HepG2 2.2.15 cells.

    Huang KL, Lai YK, Lin CC and Chang JM

    Department of Life Sciences and Institute of Biotechnology, National Tsing Hua University, Hsinchu, Taiwan.

    Previous studies showed that the root extract of Boehmeria nivea (BNE) can significantly suppress the production of hepatitis B virus (HBV) in vitro and in vivo. In this study, viral core and large-surface proteins accompanied with their encapsidated viral DNA were observed to accumulate within the cells. Notably, 78-kDa glucose-regulated protein (GRP78) was found to be suppressed by BNE, and stimulation of the GRP78 expression by thapsigargin could rescue virus production initially inhibited by BNE. The antiviral effect of BNE was reversible, which also coincided with the level of GRP78. Furthermore, we synthesized the GRP78 siRNA to knockdown the expression of GRP78 protein, and the production of supernatant HBV DNA was reduced simultaneously. Moreover, combined treatment of BNE and 3TC exhibited an additive anti-hepatitis B virus effect. In conclusion, the inhibitory effect of BNE on blocking assembled virion secretion might be via the reduction of GRP78.

    Journal of viral hepatitis 2009;16;5;367-75

  • Upregulation of GRP78 and GRP94 and its function in chemotherapy resistance to VP-16 in human lung cancer cell line SK-MES-1.

    Zhang L, Wang S, Wangtao, Y, Wang J, Jiang L, Li S, Hu X and Wang Q

    Department of Respiratory Medicine, Affiliated Zhongshan Hospital of Dalian University, Dalian, China.

    The upregulation of GRP78 and GRP94 under the induction of A23187 and its function in drug resistance to etoposide (VP-16) was investigated in human lung cancer cell line SK-MES-1. The expression of GRP78 and GRP94 induced by A23187 at different concentrations was analyzed by RT-PCR and Western blotting. Cell survival to VP-16 was determined using a colony-formation assay. The expression of GRP78 and GRP94 in the cells was found to correspond well with the cell survival to VP-16. The results showed that upregulation of GRP78 and GRP94 can significantly confer the chemoresistance to VP-16 in human lung cancer cell line SK-MES-1.

    Cancer investigation 2009;27;4;453-8

  • Mechanisms targeting apolipoprotein B100 to proteasomal degradation: evidence that degradation is initiated by BiP binding at the N terminus and the formation of a p97 complex at the C terminus.

    Rutledge AC, Qiu W, Zhang R, Kohen-Avramoglu R, Nemat-Gorgani N and Adeli K

    Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.

    Objective: In lipid-poor states, the ubiquitin-proteasomal pathway rapidly degrades misfolded apolipoprotein B100 (apoB) cotranslationally, although the mechanism of delivery from the ER to cytosolic proteasomes is poorly understood. Here we demonstrate key roles of BiP, an ER luminal chaperone, and p97, a cytosolic ATPase anchored to the ER membrane, in the targeting of apoB for proteasomal degradation.

    Using coimmunoprecipitations, we observed associations of apoB with BiP, p97, Derlin-1, VIMP, and the E3 ubiquitin ligase Hrd1 in HepG2 cells. BiP and p97 were found to bind apoB cotranslationally. Expression of C-terminal truncated apoB molecules in COS-7 cells showed an N-terminal region outside apoB15 and a C-terminal region found in apoB72 were required for BiP and p97 binding, respectively. Interestingly, overexpression of dominant negative p97 demonstrated that the ATPase activity of p97 was essential for proteasomal degradation of apoB but not for apoB binding. However, p97 activity did not appear to affect the N terminus of apoB, which may be cleaved before degradation.

    Conclusions: These data suggest that p97 and BiP play critical roles in the cotranslational delivery of apoB to proteasomes and formation of a degradative complex. Proteasomal degradation appears to selectively target apoB molecules with large C-terminal domains.

    Arteriosclerosis, thrombosis, and vascular biology 2009;29;4;579-85

  • Prefrontal cortex shotgun proteome analysis reveals altered calcium homeostasis and immune system imbalance in schizophrenia.

    Martins-de-Souza D, Gattaz WF, Schmitt A, Rewerts C, Maccarrone G, Dias-Neto E and Turck CW

    Laboratório de Neurociências, Instituto de Psiquiatria, Universidade de São Paulo, Rua. Dr. Ovidio Pires de Campos, no 785, Consolação, São Paulo, SP 05403-010, Brazil.

    Schizophrenia is a complex disease, likely to be caused by a combination of serial alterations in a number of genes and environmental factors. The dorsolateral prefrontal cortex (Brodmann's Area 46) is involved in schizophrenia and executes high-level functions such as working memory, differentiation of conflicting thoughts, determination of right and wrong concepts and attitudes, correct social behavior and personality expression. Global proteomic analysis of post-mortem dorsolateral prefrontal cortex samples from schizophrenia patients and non-schizophrenic individuals was performed using stable isotope labeling and shotgun proteomics. The analysis resulted in the identification of 1,261 proteins, 84 of which showed statistically significant differential expression, reinforcing previous data supporting the involvement of the immune system, calcium homeostasis, cytoskeleton assembly, and energy metabolism in schizophrenia. In addition a number of new potential markers were found that may contribute to the understanding of the pathogenesis of this complex disease.

    European archives of psychiatry and clinical neuroscience 2009;259;3;151-63

  • Up regulation of the GRP-78 and GADD-153 and down regulation of Bcl-2 proteins in primary glomerular diseases: a possible involvement of the ER stress pathway in glomerulonephritis.

    Markan S, Kohli HS, Joshi K, Minz RW, Sud K, Ahuja M, Anand S and Khullar M

    Department of Experimental Medicine and Biotechnology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.

    The role of endoplasmic reticulum (ER) stress in kidney diseases is not well elucidated. Fifty patients with primary glomerular diseases (PGD): minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous glomerulonephritis (MGN), membranoproliferative glomerulonephritis (MPGN), and crescentic glomerulonephritis, n = 10 (each group) were enrolled. MCD, FSGS, and MGN patients were sub-grouped as nonproliferative glomerulonephritis (NPGN) and MPGN, RPGN as proliferative glomerulonephritis (PGN). Glucose regulated proteins (GRP-78), growth arrest and DNA damage inducible proteins (GADD-153), and Bcl-2 protein expression was analyzed by Western blotting, immunofluorescence and immunohistochemistry in the kidney biopsy. Up regulation of GADD-153, GRP-78, with more pronounced expression in PGN vs. NPGN (P < 0.05) and down regulation of Bcl-2 proteins was observed in the GN (PGD excluding MCD) as compared to MCD (P < 0.05). Our results suggest that renal injury in PGD is associated with ER stress and ER stress may be involved in the rapid progression of PGN to renal failure.

    Molecular and cellular biochemistry 2009;324;1-2;131-8

  • The Endoplasmic Reticulum-associated Degradation of Transthyretin Variants Is Negatively Regulated by BiP in Mammalian Cells.

    Susuki S, Sato T, Miyata M, Momohara M, Suico MA, Shuto T, Ando Y and Kai H

    Department of Molecular Medicine, Faculty of Medical and Pharmaceutical Sciences, Global Centers of Excellence "Cell Fate Regulation Research and Education Unit," Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.

    Amyloid fibril formation of mutant transthyretin (TTR) that causes familial amyloid polyneuropathy occurs in the extracellular space. Thus, secretion of TTR variants contributes to the pathogenesis of amyloidosis. However, the molecular mechanisms underlying the endoplasmic reticulum (ER) exit or retention and subsequent degradation of TTR variants remain unclear. Here, we demonstrated that the nonsecreted TTR variants, such as D18G TTR and amyloidogenic TTRs with introduced monomeric mutation (M-TTRs), stably interact with the ER chaperone BiP in mammalian cells. These proteins were co-secreted with the secreted form of BiP in which the KDEL signal was removed, indicating that BiP partially contributes to the ER retention of nonsecreted TTR variants. More interestingly, the degradation efficiency of nonsecreted TTRs was increased when BiP was down-regulated by small interfering RNA. Thus, BiP protects the TTR variants from immediate degradation. Additionally, we showed that the stability of nonsecreted TTR variants is not disturbed in the coat complex II-deficient conditions, which are enough to inhibit the ER export of secreted TTR variants, including wild-type TTR. Therefore, the post-ER retrieval mechanism might not contribute to the ER-associated degradation of nonsecreted TTR variants. These findings suggest that the affinity to the ER-resident protein BiP regulates the fate of TTR variants in the ER.

    The Journal of biological chemistry 2009;284;13;8312-21

  • Expression of glucose-regulated stress protein GRP78 is related to progression of melanoma.

    Zhuang L, Scolyer RA, Lee CS, McCarthy SW, Cooper WA, Zhang XD, Thompson JF and Hersey P

    Department of Anatomical Pathology, Royal Prince Alfred Hospital, Sydney, NSW, Australia.

    Aims: Glucose-regulated protein 78 (GRP78) is a protein translated in response to endoplasmic reticulum (ER) stress that has been implicated in the pathogenesis and resistance to therapy of a variety of cancers. The aim of this study was to investigate its expression and role in the development and progression of human melanoma.

    The immunohistochemical expression of GRP78 in naevi, primary melanoma and melanoma metastases from 171 patients was correlated with clinicopathological factors and patient survival. The GRP78 immunoreactivity score (IRS) was 0.2 in compound naevi, 0.65 in dysplastic naevi, 4.65 in naevi adjacent to primary melanoma, 2.4 in melanoma in situ, 11.2 in thin (</=1.0 mm) and 18.1 in thick (>1.0 mm) primary melanoma. It was 18 and 17.3 in subcutaneous and lymph node metastases, respectively (P < 0.0001). GRP78 expression was positively correlated with increasing tumour thickness (P = 0.001) and with increasing dermal tumour mitotic index (P = 0.0004). Disease-free survival (chi(2) = 8.0703, P = 0.0045) and overall survival (chi(2) = 6.2633, P = 0.0123) in melanoma patients with IRS >25 were significantly lower than in melanoma patients with IRS <25.

    Conclusions: GRP78 expression appears to correlate with known correlates of melanoma progression and survival and requires further evaluation as a prognostic biomarker in melanoma.

    Histopathology 2009;54;4;462-70

  • Transcription factor TFII-I causes transcriptional upregulation of GRP78 synthesis in prostate cancer cells.

    Misra UK, Wang F and Pizzo SV

    Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.

    Receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) bind to cell surface-associated GRP78 and induce proliferative and survival signaling in prostate cancer cells. As part of the cellular response to alpha(2)M*, GRP78 expression is itself upregulated. In response to other stimuli, the transcription factor TFII-I upregulates GRP78 by binding to its gene promoter. We have, therefore, studied the role of TFII-I in transcriptional upregulation of GRP78 in 1-LN human prostate cancer cells stimulated with alpha(2)M*. This treatment caused a two- to threefold increase in TFII-I and GRP78 synthesis from [(35)S]-labeled precursor amino acids. Synthesis of both TFII-I and GRP78 were significantly reduced by silencing TFII-I gene expression or pretreatment of cells with genistein or actinomycin D. Confocal microscopy was employed to demonstrate relocation of TFII-I to the nucleus. In alpha(2)M*-stimulated cells, moreover, TFII-I bound to the GRP78 promoter as determined by CHIP assay. We also demonstrate binding of TFII-I to the c-fos promoter, consistent with its role in upregulating c-fos gene expression. In non-lymphoid cells, phosphorylated c-Src is an activator of TFII-I. Ligation of GRP78 on 1-LN cells with alpha(2)M* was followed by tyrosine phosphorylation of c-Src as well as TFII-I. We conclude that alpha(2)M*-induced increase in GRP78 synthesis is caused by transcriptional upregulation of TFII-I which binds to the GRP78 promoter and thus potentiates its cell survival and antipoptotic functions in 1-LN prostate cancer cells.

    Funded by: NHLBI NIH HHS: HL-24066

    Journal of cellular biochemistry 2009;106;3;381-9

  • Glucose-regulated protein 78 antagonizes cisplatin and adriamycin in human melanoma cells.

    Jiang CC, Mao ZG, Avery-Kiejda KA, Wade M, Hersey P and Zhang XD

    Immunology and Oncology Unit, Newcastle Misericordiae Hospital, David Maddison Clinical Sciences Building, Newcastle, New South Wales, Australia.

    Resistance of melanoma cells to chemotherapeutics remains a major obstacle to successful treatment of melanoma once it has spread beyond locoregional sites. We report in this study that activation of the unfolded protein response (UPR) is involved in resistance of melanoma cells to two chemotherapeutic drugs, cisplatin (CDDP) and adriamycin, and this is associated with glucose-regulated protein 78 (GRP78)-mediated inhibition of activation of caspase-4 and -7. The UPR was constitutively activated in cultured melanoma cell lines and fresh melanoma isolates as evidenced by elevated expression levels of the GRP78 protein and the active form of x-box-binding protein 1 messenger RNA. Treatment with CDDP or adriamycin further increased the levels, indicative of induction of endoplasmic reticulum stress and activation of the UPR by the drugs. Inhibition of GRP78 by small-interference RNA (siRNA)-sensitized melanoma cells to CDDP- and adriamycin-induced apoptosis. This was associated with enhanced caspase-4 and -7 activation as siRNA knockdown of the caspases blocked induction of apoptosis. In contrast, overexpression of GRP78 attenuated activation of caspase-4 and -7 and induction of apoptosis by the drugs. CDDP- and adriamycin-induced activation of caspase-4 and -7 appeared to be mediated by calpain activity in that it was blocked by the calpain inhibitors calpeptin and PD150606 even when GRP78 was inhibited by siRNA. These results provide new insights into resistance mechanisms of melanoma cells to CDDP and adriamycin and identify GRP78 as a potential target for enhancing chemosensitivity in melanoma.

    Carcinogenesis 2009;30;2;197-204

  • Altered expression of HSPA5, HSPA8 and PARK7 in spinocerebellar ataxia type 17 identified by 2-dimensional fluorescence difference in gel electrophoresis.

    Lee LC, Chen CM, Chen FL, Lin PY, Hsiao YC, Wang PR, Su MT, Hsieh-Li HM, Hwang JC, Wu CH, Lee GC, Singh S, Lin Y, Hsieh SY, Lee-Chen GJ and Lin JY

    Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.

    Background: Expansion of the CAG repeat of the TATA-box binding protein (TBP) gene has been identified as the causative mutations in spinocerebellar ataxia 17 (SCA17). TBP is ubiquitously expressed in both central nervous system and peripheral tissues. The underlying molecular changes of SCA17 are rarely explored.

    Methods: To study the molecular mechanisms underlying SCA17, we generated stably induced isogenic 293 cells expressing normal TBP-Q(36) and expanded TBP-Q(61) and analyzed the expressed proteins using two-dimensional difference in gel electrophoresis (2D-DIGE), followed by mass spectrometry and immunoblotting.

    Results: Upon induction with doxycycline, the expanded TBP-Q(61) formed aggregates with significant increase in the cell population at subG1 phase and cleaved caspase-3. Proteomics study identified a total of 16 proteins with expression changes greater than 1.5 fold. Among the 16 proteins, PARK7, GLRX3, HNRNPA1, GINS1, ENO1, HNRPK and NPM1 are increased, and SERPINA5, HSPA5, VCL, KHSRP, HSPA8, HNRPH1, IMMT, VCP and HNRNPL are decreased in cells expressing TBP-Q(61) compared with those expressing TBP-Q(36). The altered expression of HSPA5, HSPA8 and PARK7 were further validated by 2D and Western immunoblot analyses.

    Conclusions: The results illustrate the utility of proteomics to identify alterations of proteins which underlie pathogenesis of SCA17, and may serve as potential therapeutic targets.

    Clinica chimica acta; international journal of clinical chemistry 2009;400;1-2;56-62

  • Transcriptional repression of the prosurvival endoplasmic reticulum chaperone GRP78/BIP by E2F1.

    Racek T, Buhlmann S, Rüst F, Knoll S, Alla V and Pützer BM

    Department of Vectorology and Experimental Gene Therapy, Biomedical Research Center, University of Rostock, 18055 Rostock, Germany.

    The endoplasmic reticulum chaperone GRP78/BIP plays a central role in the prosurvival machinery, and its enhanced expression has been implicated in drug resistance, carcinogenesis, and metastasis. E2F1, as part of an antitumor safeguard mechanism, promotes apoptosis regardless of functional p53. Using cells that are defective in p53, we show that E2F1 represses GRP78/BIP at the transcriptional level, and this requires its DNA binding domain. Analysis of human GRP78/BIP promoter reporter constructs revealed that the region between -371 and -109 of the proximal promoter contains major E2F1-responsive elements. Toward understanding the underlying mechanism of this regulation, we performed chromatin immunoprecipitation and gel shift assays, demonstrating that E2F1 directly binds to GC-rich 1f40 regions in the distal GC-box and endoplasmic reticulum stress response element -126 by interfering with the binding of positive regulatory proteins Sp1 and TFII-I of the ER stress response element-binding factor complex. We further show that TFII-I, which is required for optimal stress induction of GRP78/BIP, is suppressed by E2F1 on the protein level. Finally, our studies suggest a molecular link between the inhibition of GRP78/BIP and E2F1-mediated chemosensitization of tumor cells, underscoring its relevance for cancer treatment. Together, the data provide a new mechanism for the incompletely understood tumor suppressor function of E2F1.

    The Journal of biological chemistry 2008;283;49;34305-14

  • Glucose-regulated protein 78 as a novel effector of BRCA1 for inhibiting stress-induced apoptosis.

    Yeung BH, Kwan BW, He, Lee AS, Liu J and Wong AS

    School of Biological Sciences, University of Hong Kong, Hong Kong, China.

    The tumor suppressor BRCA1 is mutated in a high percentage of familial breast and ovarian cancer, but our understanding of its mechanisms of action remains incomplete. We report here that glucose-regulated protein (GRP)-78, a critical regulator of the unfolded protein response (UPR), is a novel downstream target of BRCA1. We showed that overexpression of wild-type BRCA1 suppressed the expression of GRP78, whereas expression of mutant BRCA1 gene or targeted inhibition of endogenous BRCA1 using small-interfering RNA (siRNA) enhanced GRP78 expression. Knockdown of BRCA1 also led to induction of other components of UPR, such as GRP94 and CHOP. Consistent with a role of BRCA1 knockdown in mediating cell survival, forced expression of GRP78 stimulated cell proliferation and prevented apoptosis, including that induced by endoplasmic reticulum stress and chemotherapy, in ovarian OVCAR-3 and breast MCF-7 cancer cells. Overexpression of wild-type BRCA1 could increase the apoptosis of GRP78-overexpressing cells. Conversely, knockdown GRP78 by siRNA sensitized ovarian and breast cancer cells to apoptosis. This effect was reduced when the expression of BRCA1 was simultaneously knockdown by siRNA, indicating that BRCA1 also negatively regulates GRP78-mediated cell survival and resistance to apoptosis.

    Oncogene 2008;27;53;6782-9

  • Oxidative stress, telomere length and biomarkers of physical aging in a cohort aged 79 years from the 1932 Scottish Mental Survey.

    Starr JM, Shiels PG, Harris SE, Pattie A, Pearce MS, Relton CL and Deary IJ

    MRC Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Royal Victoria Hospital, Edinburgh EH4 2DN, UK. jstarr@staffmail.ed.ac.uk

    Telomere shortening is a biomarker of cellular senescence and is associated with a wide range of age-related disease. Oxidative stress is also associated with physiological aging and several age-related diseases. Non-human studies suggest that variants in oxidative stress genes may contribute to both telomere shortening and biological aging. We sought to test whether oxidative stress-related gene polymorphisms contribute to variance in both telomere length and physical biomarkers of aging in humans. Telomere lengths were calculated for 190 (82 men, 108 women) participants aged 79 years and associations with 384 SNPs, from 141 oxidative stress genes, identified 9 significant SNPS, of which those from 5 genes (GSTZ1, MSRA, NDUFA3, NDUFA8, VIM) had robust associations with physical aging biomarkers, respiratory function or grip strength. Replication of associations in a sample of 318 (120 males, 198 females) participants aged 50 years confirmed significant associations for two of the five SNPs (MSRA rs4841322, p=0.008; NDUFA8 rs6822, p=0.048) on telomere length. These data indicate that oxidative stress genes may be involved in pathways that lead to both telomere shortening and physiological aging in humans. Oxidative stress may explain, at least in part, associations between telomere shortening and physiological aging.

    Funded by: Biotechnology and Biological Sciences Research Council: S18386; Chief Scientist Office: CZB/4/505, ETM/55; Medical Research Council; Wellcome Trust

    Mechanisms of ageing and development 2008;129;12;745-51

  • Promoter polymorphisms modulating HSPA5 expression may increase susceptibility to Taiwanese Alzheimer's disease.

    Hsu WC, Wang HK, Lee LC, Fung HC, Lin JC, Hsu HP, Wu YR, Ro LS, Hu FJ, Chang, Lee-Chen GJ and Chen CM

    Department of Neurology, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taipei, 10507, Taiwan.

    Endoplasmic reticulum (ER) chaperone heat shock 70 kDa protein 5 (HSPA5/GRP78) is known to be involved in the metabolism of amyloid precursor protein and neuronal death in Alzheimer's disease (AD) could arise from dysfunction of the ER. Through a case-control study and an expression assay, we investigated the association of HSPA5 -415 G/A (rs391957), -370 C/T (rs17840761) and -180 del/G (rs3216733) polymorphisms with Taiwanese AD. The overall genotype and allele frequency distribution at the completely linked -415 G/A and -180 del/G sites showed significant difference between AD cases and controls (P = 0.020 and 0.009, respectively). A decrease in risk of developing AD was demonstrated for -415 AA/-180 GG genotype [OR = 0.38, 95% confidence interval (CI) = 0.18-0.75, P = 0.007] and -415 A/-180 G allele (OR = 0.69, 95% CI = 0.51-0.91, P = 0.009). The HSPA5 transcriptional activity of the -415 A/-180 G allele was significantly lower than that of the -415 G/-180 del alleles, whereas induction of HSPA5 expression after ER stress was markedly increased in the cells with the -415 A/-180 G allele. Therefore, our preliminary results may suggest a protective role of the HSPA5 -415 A/-180 G allele in Taiwanese AD susceptibility.

    Journal of neural transmission (Vienna, Austria : 1996) 2008;115;11;1537-43

  • Upregulation of 78-kDa glucose-regulated protein in macrophages in peripheral joints of active ankylosing spondylitis.

    Dong W, Zhang Y, Yan M, Liu H, Chen Z and Zhu P

    Department of Clinical Immunology, State Key Discipline of Cell Biology, Xijing Hospital, Fourth Military Medical University, Xi'an, China.

    Objectives: To investigate the expression of the 78-kDa glucose-regulated protein (GRP78), a marker of activation of the unfolded protein response (UPR), in macrophages of ankylosing spondylitis (AS) synovium and synovial fluid and to explore the relationship between the expression of GRP78 and synovial fluid levels of the proinflammatory cytokines, as well as the inflammatory activity of AS.

    Methods: Immunohistochemical staining and Western blotting were performed to detect the expression of GRP78 in macrophages in the involved peripheral joints of 16 patients with active AS, and in 15 patients with osteoarthritis (OA) as controls. Synovial fluid levels of tumour necrosis factor-alpha (TNFalpha) and interleukin-6 (IL-6) of AS peripheral joints were measured using an enzyme-linked immunosorbent assay (ELISA). The inflammatory activity of AS was measured by the sera levels of IL-6 and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI).

    Results: Expression of GRP78 in macrophages was increased significantly in the affected peripheral joints of AS compared with OA patients. Positive correlations were found between the expression of GRP78 in macrophages in AS-affected peripheral joints and the synovial fluid levels of TNFalpha and IL-6, as well as the sera levels of IL-6 and the BASDAI.

    Conclusions: Activation of the UPR occurs in macrophages in both the synovium and synovial fluids of AS-involved peripheral joints, and there may be a link between activation of the UPR of macrophages and local production of the proinflammatory cytokines, as well as the inflammatory activity of AS.

    Scandinavian journal of rheumatology 2008;37;6;427-34

  • Endoplasmic reticulum chaperone protein GRP-78 mediates endocytosis of dentin matrix protein 1.

    Ravindran S, Narayanan K, Eapen AS, Hao J, Ramachandran A, Blond S and George A

    Department of Oral Biology, University of Illinois, Chicago, Illinois 60612, USA.

    Dentin matrix protein 1 (DMP1), a phosphorylated protein present in the mineral phase of both vertebrates and invertebrates, is a key regulatory protein during biogenic formation of mineral deposits. Previously we showed that DMP1 is localized in the nuclear compartment of preosteoblasts and preodontoblasts. In the nucleus DMP1 might play an important role in the regulation of genes that control osteoblast or odontoblast differentiation. Here, we show that cellular uptake of DMP1 occurs through endocytosis. Interestingly, this process is initiated by DMP1 binding to the glucose-regulated protein-78 (GRP-78) localized on the plasma membrane of preodontoblast cells. Binding of DMP1 to GRP-78 receptor was determined to be specific and saturable with a binding dissociation constant K(D)=85 nm. We further depict a road map for the endocytosed DMP1 and demonstrate that the internalization is mediated primarily by caveolae and that the vesicles containing DMP1 are routed to the nucleus along microtubules. Immunohistochemical analysis and binding studies performed with biotin-labeled DMP1 confirm spatial co-localization of DMP1 and GRP-78 in the preodontoblasts of a developing mouse molar. Co-localization of DMP1 with GRP-78 was also observed in T4-4 preodontoblast cells, dental pulp stem cells, and primary preodontoblasts. By small interfering RNA techniques, we demonstrate that the receptor for DMP1 is GRP-78. Therefore, binding of DMP1 with GRP-78 receptor might be an important mechanism by which DMP1 is internalized and transported to the nucleus during bone and tooth development.

    Funded by: NIDCR NIH HHS: DE 11657, DE 16533

    The Journal of biological chemistry 2008;283;44;29658-70

  • Mammalian BiP controls posttranslational ER translocation of the hepatitis B virus large envelope protein.

    Awe K, Lambert C and Prange R

    Department of Medical Microbiology and Hygiene, Johannes Gutenberg-University Mainz, D-55101 Mainz, Germany.

    The hepatitis B virus L protein forms a dual topology in the endoplasmic reticulum (ER) via a process involving cotranslational membrane integration and subsequent posttranslational translocation of its preS subdomain. Here, we show that preS posttranslocation depends on the action of the ER chaperone BiP. To modulate the in vivo BiP activity, we designed an approach based on overexpressing its positive and negative regulators, ER-localized DnaJ-domain containing protein 4 (ERdj4) and BiP-associated protein (BAP), respectively. The feasibility of this approach was confirmed by demonstrating that BAP, but not ERdj4, destabilizes the L/BiP complex. Overexpressing BAP or ERdj4 inhibits preS posttranslocation as does the reduction of ATP levels. These results hint to a new role of BiP in guiding posttranslational polypeptide import into the mammalian ER.

    FEBS letters 2008;582;21-22;3179-84

  • Glucose-regulated protein 78 regulates multiple malignant phenotypes in head and neck cancer and may serve as a molecular target of therapeutic intervention.

    Chiu CC, Lin CY, Lee LY, Chen YJ, Kuo TF, Chang JT, Liao CT, Wang HM, Yen TC, Shen CR, Liao SK and Cheng AJ

    Graduate Institute of Biomedical Science, Chang Gung University, Taoyuan, Taiwan.

    Glucose-regulated protein 78 (Grp78) is an endoplasmic reticulum chaperone protein and is overexpressed in various cancers. However, it is unclear how significance of this molecule play an active role contributing to the oncogenic effect of head and neck cancer (HNC). To investigate the potential function of Grp78, six HNC cell lines were used. We found that Grp78 is highly expressed in all six cell lines and many of the proteins were localized in the periphery regions, implying other function of this molecule aside from endoplasmic reticulum stress response. Knockdown of Grp78 by small interfering RNA significantly reduced cell growth and colony formation to 53% to 12% compared with that of controls in all six HNC cell lines. Using in vitro wound healing and Matrigel invasion assays, we found that cell migration and invasive ability were also inhibited to 23% to 2% in all these cell lines tested. In vivo xenograft studies showed that administration of Grp78-small interfering RNA plasmid into HNC xenografts significantly inhibited both tumor growth in situ (>60% inhibition at day 34) and liver metastasis (>90% inhibition at day 20). Our study showed that Grp78 actively regulates multiple malignant phenotypes, including cell growth, migration, and invasion. Because knockdown Grp78 expression succeeds in the reduction of tumor growth and metastatic potential, this molecule may serve as a molecular target of therapeutic intervention for HNC.

    Molecular cancer therapeutics 2008;7;9;2788-97

  • GRP78 upregulation by atheroprone shear stress via p38-, alpha2beta1-dependent mechanism in endothelial cells.

    Feaver RE, Hastings NE, Pryor A and Blackman BR

    Department of Biomedical Engineering, University of Virginia-Health System, PO Box 800759, Charlottesville, VA 22908, USA.

    Objective: The initiation of atherosclerosis is in part dependent on the hemodynamic shear stress environment promoting a proinflammatory phenotype of the endothelium. Previous studies demonstrated increased expression of ER stress protein and unfolded protein response (UPR) regulator, GRP78, within all vascular cells in atherosclerotic lesions and its regulation in the endothelium by several atherosclerotic stressors; however, regulation of GRP78 by shear stress directly has not been established.

    Using an in vitro model to simulate human arterial shear stress waveforms, atheroprone or atheroprotective flow was applied to human endothelial cells. GRP78 was found to be significantly upregulated (3-fold) in a sustained manner under atheroprone, but not atheroprotective flow up to 24 hours. This response was dependent on both sustained activation of p38, as well integrin alpha2beta1. Increased GRP78 correlated with the activation of the ER stress sensing element (ERSE1) promoter by atheroprone flow as a marker of the UPR. Shear stress regulated GRP78 through increased protein stability when compared to other flow regulated proteins, such as connexin-43 and vascular cell adhesion molecule (VCAM)-1. Increased endothelial expression of GRP78 was also observed in atheroprone versus atheroprotective regions of C57BL6 mice.

    Conclusions: This study supports a role of the hemodynamic environment in preferentially inducing GRP78 and the UPR in atheroprone regions, before lesion development, and suggests a potential atheroprotective (ie, prosurvival), compensatory effect in response to ER stress within atherosclerotic lesions.

    Funded by: NHLBI NIH HHS: R01 HL080956, R01 HL080956-02, R01-HL080956

    Arteriosclerosis, thrombosis, and vascular biology 2008;28;8;1534-41

  • Stress chaperone GRP78/BiP confers chemoresistance to tumor-associated endothelial cells.

    Virrey JJ, Dong D, Stiles C, Patterson JB, Pen L, Ni M, Schönthal AH, Chen TC, Hofman FM and Lee AS

    Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9176, USA.

    The tumor vasculature is essential for tumor growth and survival and is a key target for anticancer therapy. Glioblastoma multiforme, the most malignant form of brain tumor, is highly vascular and contains abnormal vessels, unlike blood vessels in normal brain. Previously, we showed that primary cultures of human brain endothelial cells, derived from blood vessels of malignant glioma tissues (TuBEC), are physiologically and functionally different from endothelial cells derived from nonmalignant brain tissues (BEC) and are substantially more resistant to apoptosis. Resistance of TuBEC to a wide range of current anticancer drugs has significant clinical consequences as it represents a major obstacle toward eradication of residual brain tumor. We report here that the endoplasmic reticulum chaperone GRP78/BiP is generally highly elevated in the vasculature derived from human glioma specimens, both in situ in tissue and in vitro in primary cell cultures, compared with minimal GRP78 expression in normal brain tissues and blood vessels. Interestingly, TuBEC constitutively overexpress GRP78 without concomitant induction of other major unfolded protein response targets. Resistance of TuBEC to chemotherapeutic agents such as CPT-11, etoposide, and temozolomide can be overcome by knockdown of GRP78 using small interfering RNA or chemical inhibition of its catalytic site. Conversely, overexpression of GRP78 in BEC rendered these cells resistant to drug treatments. Our findings provide the proof of principle that targeting GRP78 will sensitize the tumor vasculature to chemotherapeutic drugs, thus enhancing the efficacy of these drugs in combination therapy for glioma treatment.

    Funded by: NCI NIH HHS: CA027607, CA111700, R01 CA027607, R01 CA027607-27A2, R01 CA111700, R01 CA111700-03, R01 CA111700-04; NIA NIH HHS: P50 AG005142

    Molecular cancer research : MCR 2008;6;8;1268-75

  • Human XTP3-B forms an endoplasmic reticulum quality control scaffold with the HRD1-SEL1L ubiquitin ligase complex and BiP.

    Hosokawa N, Wada I, Nagasawa K, Moriyama T, Okawa K and Nagata K

    Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan. nobuko@frontier.kyoto-u.ac.jp

    The recognition of terminally misfolded proteins in the endoplasmic reticulum (ER) and the extraction of these proteins to the cytoplasm for proteasomal degradation are determined by a quality control mechanism in the ER. In yeast, Yos9p, an ER lectin containing a mannose 6-phosphate receptor homology (MRH) domain, enhances ER-associated degradation (ERAD) of glycoproteins. We show here that human XTP3-B (hXTP3-B), an ER lectin containing two MRH domains, has two transcriptional variants, and both isoforms retard ERAD of the human alpha(1)-antitrypsin variant null Hong Kong (NHK), a terminally misfolded glycoprotein. The hXTP3-B long isoform strongly inhibited ERAD of NHK-QQQ, which lacks all of the N-glycosylation sites of NHK, but the short transcriptional variant of hXTP3-B had almost no effect. Examination of complex formation by immunoprecipitation and by fractionation using sucrose density gradient centrifugation revealed that the hXTP3-B long isoform associates with the HRD1-SEL1L membrane-anchored ubiquitin ligase complex and BiP, forming a 27 S ER quality control scaffold complex. The hXTP3-B short isoform, however, is excluded from scaffold formation. Another MRH domain-containing ER lectin, hOS-9, is incorporated into this large complex, but gp78, another mammalian homolog of the yeast ubiquitin ligase Hrd1p, is not. Based on these results, we propose that this large ER quality control scaffold complex, containing ER lectins, a chaperone, and a ubiquitin ligase, provides a platform for the recognition and sorting of misfolded glycoproteins as well as nonglycosylated proteins prior to retrotranslocation into the cytoplasm for degradation.

    The Journal of biological chemistry 2008;283;30;20914-24

  • Overexpression of GRP78 and GRP94 are markers for aggressive behavior and poor prognosis in gastric carcinomas.

    Zheng HC, Takahashi H, Li XH, Hara T, Masuda S, Guan YF and Takano Y

    Department of Biochemistry and Molecular Biology, College of Basic Medicine, China Medical University, Shenyang 110003, China. zheng_huachuan@hotmail.com

    Glucose-related proteins (GRPs) are ubiquitously expressed in endoplasmic reticulum and able to assist in protein folding and assembly; consequently, they are considered as molecular chaperones. GRP78 and GRP94 expression was induced by glucose starvation and up-regulated in the malignancies. To clarify the roles of both molecules in tumorigenesis and progression of gastric carcinomas, immunohistochemistry was used on tissue microarray containing gastric carcinomas, adenomas, and nonneoplastic mucosa using the antibodies against GRP78 and GRP94, with a comparison of their expression with clinicopathological parameters of carcinomas. Gastric carcinoma cell lines (MKN28, AGS, MKN45, KATO-III, and HGC-27) were studied for both proteins by immunohistochemistry and Western blot. There was more expression of both proteins in gastric carcinoma and adenoma than in nonneoplastic mucosas (P < .05). All gastric carcinoma cell lines showed their expression at different levels. They were positively correlated with tumor size, depth of invasion, lymphatic and venous invasion, lymph node metastasis, and Union Internationale Contre le Cancer staging (P < .05), with positive relationship between both proteins (P < .05). Univariate analysis indicated the postsurgical cumulative survival rate of patients with positive GRP78 or GRP94 expression to be lower than that in those without GRP78 or GRP94 expression (P < .05), but the close link disappeared if stratified according to depth of invasion (P > .05). Multivariate analysis showed that age, depth of invasion, lymphatic invasion, lymph node metastasis, Union Internationale Contre le Cancer staging, and Lauren classification (P < .05), but not GRP78 and GRP94 expression, were independent prognostic factors for carcinomas (P > .05). Up-regulated expression of GRP78 and GRP94 was possibly involved in pathogenesis, growth, invasion, and metastasis of gastric carcinomas. They were considered objective and effective markers for the aggressive behavior and poor prognosis in gastric carcinomas.

    Human pathology 2008;39;7;1042-9

  • GRP78 and Raf-1 cooperatively confer resistance to endoplasmic reticulum stress-induced apoptosis.

    Shu CW, Sun FC, Cho JH, Lin CC, Liu PF, Chen PY, Chang MD, Fu HW and Lai YK

    The chaperone glucose-regulated protein, 78/immunoglobulin binding protein (GRP78/Bip), protects cells from cytotoxicity induced by DNA damage or endoplasmic reticulum (ER) stress. In this study, we showed that GRP78 is a major inducible protein in human non-small cell lung cancer H460 cells treated with ER stress inducers, including A23187 and thapsigargin. AEBSF, an inhibitor of serine protease, diminished GRP78 induction, enhanced mitochondrial permeability, and augmented apoptosis in H460 cells during ER stress. Simultaneously, AEBSF promoted Raf-1 degradation and suppressed phosphorylation of Raf-1 at Ser338 and/or Tyr340 during ER stress. Coimmunoprecipitation assays and subcellular fractionations showed that GRP78 associated and colocalized with Raf-1 on the outer membrane of mitochondria, respectively. While treatment of cells with ER stress inducers inactivated BAD by phosphorylation at Ser75, a Raf-1 phosphorylation site; AEBSF attenuated phosphorylation of BAD, leading to cytochrome c release from mitochondria. Additionally, overexpression of GRP78 and/or Raf-1 protected cells from ER stress-induced apoptosis. Taken together, our results indicate that GRP78 may stabilize Raf-1 to maintain mitochondrial permeability and thus protect cells from ER stress-induced apoptosis.

    Journal of cellular physiology 2008;215;3;627-35

  • GRP78 is overexpressed in glioblastomas and regulates glioma cell growth and apoptosis.

    Lee HK, Xiang C, Cazacu S, Finniss S, Kazimirsky G, Lemke N, Lehman NL, Rempel SA, Mikkelsen T and Brodie C

    Department of Neurosurgery and Hermelin Brain Tumor Center, Henry Ford Health System, Detroit, MI 48202, USA.

    We characterized the expression and function of the endoplasmic reticulum protein GRP78 in glial tumors. GRP78 is highly expressed in glioblastomas but not in oligodendrogliomas, and its expression is inversely correlated with median patient survival. Overexpression of GRP78 in glioma cells decreases caspase 7 activation and renders the cells resistant to etoposide- and cisplatin-induced apoptosis, whereas silencing of GRP78 decreases cell growth and sensitizes glioma cells to etoposide, cisplatin, and gamma-radiation. Thus, GRP78 contributes to the increased apoptosis resistance and growth of glioma cells and may provide a target for enhancing the therapeutic responsiveness of these tumors.

    Funded by: NCI NIH HHS: CA-109196, CA-86997, CA-R21-96965, R01 CA086997, R01 CA109196; NINDS NIH HHS: K08 NS045077

    Neuro-oncology 2008;10;3;236-43

  • Identification of proteins associating with glycosylphosphatidylinositol- anchored T-cadherin on the surface of vascular endothelial cells: role for Grp78/BiP in T-cadherin-dependent cell survival.

    Philippova M, Ivanov D, Joshi MB, Kyriakakis E, Rupp K, Afonyushkin T, Bochkov V, Erne P and Resink TJ

    Department of Research, Cardiovascular Laboratories, Basel University Hospital, Hebelstrasse 20, CH 4031 Basel, Switzerland. maria.filippova@unibas.ch

    There is scant knowledge regarding how cell surface lipid-anchored T-cadherin (T-cad) transmits signals through the plasma membrane to its intracellular targets. This study aimed to identify membrane proteins colocalizing with atypical glycosylphosphatidylinositol (GPI)-anchored T-cad on the surface of endothelial cells and to evaluate their role as signaling adaptors for T-cad. Application of coimmunoprecipitation from endothelial cells expressing c-myc-tagged T-cad and high-performance liquid chromatography revealed putative association of T-cad with the following proteins: glucose-related protein GRP78, GABA-A receptor alpha1 subunit, integrin beta3, and two hypothetical proteins, LOC124245 and FLJ32070. Association of Grp78 and integrin beta3 with T-cad on the cell surface was confirmed by surface biotinylation and reciprocal immunoprecipitation and by confocal microscopy. Use of anti-Grp78 blocking antibodies, Grp78 small interfering RNA, and coexpression of constitutively active Akt demonstrated an essential role for surface Grp78 in T-cad-dependent survival signal transduction via Akt in endothelial cells. The findings herein are relevant in the context of both the identification of transmembrane signaling partners for GPI-anchored T-cad as well as the demonstration of a novel mechanism whereby Grp78 can influence endothelial cell survival as a cell surface signaling receptor rather than an intracellular chaperone.

    Molecular and cellular biology 2008;28;12;4004-17

  • Endoplasmic reticulum stress induced by oxidative stress in retinal pigment epithelial cells.

    He S, Yaung J, Kim YH, Barron E, Ryan SJ and Hinton DR

    Department of Pathology, Keck School of Medicine of the University of Southern California, 2011 Zonal Ave., HMR 209, Los Angeles, CA 90033, USA.

    Background: Induction of glucose-regulated protein (GRP)-78 in the endoplasmic reticulum (ER) is a protective mechanism cells use to adapt to ER stress. We evaluated the expression of GRP-78 and its regulation by an oxidant tert-butyl hydroperoxide (tBH) in human retinal pigment epithelium (RPE) cells.

    Methods: We used a carboxy-H2-DCFDA staining method to detect tBH-induced accumulation of reactive oxygen species (ROS) in RPE cells, and analyzed the expression of GRP-78 in normal human fetal and adult retinas and in cultured human RPE cells by immunohistochemistry. The effects of tBH (10-100 microM) on GRP-78 and on growth arrest and DNA damage inducible genes 153 (GADD153) protein and mRNA expression were studied using Western blot and real-time polymerase chain reaction.

    Results: Sections of fetal retinas were negative for GRP-78. Adult retinas showed moderate cytoplasmic GRP-78 staining in the RPE and choroid. tBH-induced ROS accumulation in RPE cells showed partial colocalization with the ER. GRP-78 and GADD153 mRNA and protein expression in cultured RPE cells were significantly upregulated by treatment with tBH.

    Conclusion: tBH increases oxidative stress, increases accumulation of ROS in the ER, and upregulates expression of GRP-78 and GADD153. This supports the connection between oxidative stress and ER stress, and suggests that GRP-78 may serve a protective role in the RPE response to oxidative stress.

    Funded by: NEI NIH HHS: EY01545, EY03040

    Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie 2008;246;5;677-83

  • HSPA5 promoter polymorphisms and risk of Parkinson's disease in Taiwan.

    Chen CM, Wu YR, Hu FJ, Chen YC, Chuang TJ, Cheng YF and Lee-Chen GJ

    Department of Neurology, Chang Gung Memorial Hospital, Chang-Gung University College of Medicine, Taipei, Taiwan.

    Endoplasmic reticulum (ER) stress induced by misfolded proteins has been implicated in Parkinson's disease (PD) pathogenesis. A malfunction of unfolded protein response (UPR) to ER stress can result in PD as well as other neurodegenerative diseases. Heat shock 70 kDa protein 5 (HSPA5) is one of the UPR chaperones reactive to ER stress to block the apoptotic process. HSPA5 promoter polymorphisms -415 G/A (rs391957), -370 C/T (rs17840761) and -180 del/G (rs3216733) and their derived haplotypes may affect promoter activity of the gene. This study examines whether these HSPA5 promoter polymorphisms are associated with the risk of Taiwanese PD and the age of disease onset using a case-control study. Polymorphisms -415 G/A and -180 del/G were completely linked in our population (D'=1.00, Delta(2)=1.00). The genotype or allele frequency distribution of each HSPA5 polymorphism was not significantly different between the controls (n=341) and the PD patients (n=393). Neither the linked -415 G/A and -180 del/G nor -370 C/T polymorphism influences PD onset age. Our data suggest that the HSPA5 -415 G/A, -370 C/T, and -180 del/G polymorphisms are unlikely to play a major role in risk of developing PD in Taiwan.

    Neuroscience letters 2008;435;3;219-22

  • A new tumor-specific variant of GRP78 as target for antibody-based therapy.

    Rauschert N, Brändlein S, Holzinger E, Hensel F, Müller-Hermelink HK and Vollmers HP

    Institute of Pathology, University of Würzburg, Würzburg, Germany.

    The chaperone GRP78 is a member of the heat-shock protein 70 (HSP70) family and is responsible for cellular homeostasis by preventing stress-induced apoptosis. GRP78 is expressed in all cells of the body. In malignant cells, which are permanently exposed to environmental stress, GRP78 is overexpressed and increased levels can be found in the cytoplasm and on the cell membrane. Thus, GRP78 promotes tumor proliferation, survival, metastases and resistance to a wide variety of therapies. Like other tumor-specific membrane molecules, GRP78 can also be present on cancer cells in a variant form. This modification qualifies it as a target for immune surveillance and antibody responses. The fully human monoclonal IgM antibody, SAM-6, was isolated from a gastric cancer patient and it binds to a new variant of GRP78 with a molecular weight of 82 kDa. The epitope is an O-linked carbohydrate moiety and is specific for malignant cells. These data show that cancer-specific modifications of cell-surface protection molecules are (a) subject of an immune response and (b) ideal targets for new therapeutical approaches.

    Laboratory investigation; a journal of technical methods and pathology 2008;88;4;375-86

  • Expression and clinical significance of glucose regulated proteins GRP78 (BiP) and GRP94 (GP96) in human adenocarcinomas of the esophagus.

    Langer R, Feith M, Siewert JR, Wester HJ and Hoefler H

    Institute of Pathology, TU München, München, Germany. Rupert.Langer@lrz.tu-muenchen.de

    Background: Glucose regulated proteins (GRPs) are main regulators of cellular homeostasis due to their role as molecular chaperones. Moreover, the functions of GRPs suggest that they also may play important roles in cancer biology. In this study we investigated the glucose regulated proteins GRP78 (BiP) and GRP94 (GP96) in a series of human esophageal adenocarcinomas to determine their implications in cancer progression and prognosis.

    Methods: Formalin-fixed, paraffin-embedded tissues of primary resected esophageal (Barrett) adenocarcinomas (n = 137) and corresponding normal tissue were investigated. mRNA-gene expression levels of GRP78 and GRP94 were determined by quantitative real-time RT-PCR after mRNA extraction. Protein expression analysis was performed with immunohistochemical staining of the cases, assembled on a tissue micorarray. The results were correlated with pathologic features (pT, pN, G) and overall survival.

    Results: GRP78 and GRP94 mRNA were expressed in all tumors. The relative gene expression of GRP78 was significantly higher in early cancers (pT1m and pT1sm) as compared to more advanced stages (pT2 and pT3) and normal tissue (p = 0.031). Highly differentiated tumors showed also higher GRP78 mRNA levels compared to moder c43 ate and low differentiated tumors (p = 0.035). In addition, patients with higher GRP78 levels tended to show a survival benefit (p = 0.07). GRP94 mRNA-levels showed no association to pathological features or clinical outcome.GRP78 and GRP94 protein expression was detectable by immunohistochemistry in all tumors. There was a significant correlation between a strong GRP78 protein expression and early tumor stages (pT1m and pT1sm, p = 0.038). For GRP94 low to moderate protein expression was significantly associated with earlier tumor stage (p = 0.001) and less lymph node involvement (p = 0.036). Interestingly, the patients with combined strong GRP78 and GRP94 protein expression exclusively showed either early (pT1m or pT1sm) or advanced (pT3) tumor stages and no pT2 stage (p = 0.031).

    Conclusion: We could demonstrate an association of GRP78 and GRP94 mRNA and protein expression with tumor stage and behaviour in esophageal adenocarcinomas. Increased expression of GRP78 may be responsible for controlling local tumor growth in early tumor stages, while high expression of GRP78 and GRP94 in advanced stages may be dependent from other factors like cellular stress reactions due to glucose deprivation, hypoxia or the hosts' immune response.

    BMC cancer 2008;8;70

  • OS-9 and GRP94 deliver mutant alpha1-antitrypsin to the Hrd1-SEL1L ubiquitin ligase complex for ERAD.

    Christianson JC, Shaler TA, Tyler RE and Kopito RR

    Department of Biological Sciences & Bio-X Program, Stanford University, Lorry Lokey Bldg, 337 Campus Drive, Stanford, CA 94305, USA.

    Terminally misfolded or unassembled proteins in the early secretory pathway are degraded by a ubiquitin- and proteasome-dependent process known as ER-associated degradation (ERAD). How substrates of this pathway are recognized within the ER and delivered to the cytoplasmic ubiquitin-conjugating machinery is unknown. We report here that OS-9 and XTP3-B/Erlectin are ER-resident glycoproteins that bind to ERAD substrates and, through the SEL1L adaptor, to the ER-membrane-embedded ubiquitin ligase Hrd1. Both proteins contain conserved mannose 6-phosphate receptor homology (MRH) domains, which are required for interaction with SEL1L, but not with substrate. OS-9 associates with the ER chaperone GRP94 which, together with Hrd1 and SEL1L, is required for the degradation of an ERAD substrate, mutant alpha(1)-antitrypsin. These data suggest that XTP3-B and OS-9 are components of distinct, partially redundant, quality control surveillance pathways that coordinate protein folding with membrane dislocation and ubiquitin conjugation in mammalian cells.

    Funded by: NIGMS NIH HHS: R01 GM074874, R01 GM074874-04

    Nature cell biology 2008;10;3;272-82

  • HSP105 interacts with GRP78 and GSK3 and promotes ER stress-induced caspase-3 activation.

    Meares GP, Zmijewska AA and Jope RS

    Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294-0017, USA.

    Stress of the endoplasmic reticulum (ER stress) is caused by the accumulation of misfolded proteins, which occurs in many neurodegenerative diseases. ER stress can lead to adaptive responses or apoptosis, both of which follow activation of the unfolded protein response (UPR). Heat shock proteins (HSP) support the folding and function of many proteins, and are important components of the ER stress response, but little is known about the role of one of the major large HSPs, HSP105. We identified several new partners of HSP105, including glycogen synthase kinase-3 (GSK3), a promoter of ER stress-induced apoptosis, and GRP78, a key component of the UPR. Knockdown of HSP105 did not alter UPR signaling after ER stress, but blocked caspase-3 activation after ER stress. In contrast, caspase-3 activation induced by genotoxic stress was unaffected by knockdown of HSP105, suggesting ER stress-specificity in the apoptotic action of HSP105. However, knockdown of HSP105 did not alter cell survival after ER stress, but instead diverted signaling to a caspase-3-independent cell death pathway, indicating that HSP105 is necessary for apoptotic signaling after UPR activation by ER stress. Thus, HSP105 appears to chaperone the responses to ER stress through its interactions with GRP78 and GSK3, and without HSP105 cell death following ER stress proceeds by a non-caspase-3-dependent process.

    Funded by: NIA NIH HHS: AG021045, R01 AG021045, R01 AG021045-05; NIMH NIH HHS: MH38752, R01 MH038752, R01 MH038752-23, R56 MH038752

    Cellular signalling 2008;20;2;347-58

  • Down-regulation of molecular chaperone 78-kd glucose-regulated protein/immunoglobulin-binding protein expression involved in enhancement of human RS cell mutability.

    Hirano J, Kita K, Sugaya S, Ichimura Y, Yamamori H, Nakajima N and Suzuki N

    Department of General Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.

    Objectives: Enhancement of cell mutability via extracellular materials of cancer cells is a crucial event leading to the development of cancers; however, the activation process of mutability is still not well understood. In this study, to identify the regulatory mechanism of cell mutability, we investigated mutability modulated in response to human pancreatic cancer cell-conditioned medium and identified the candidates for cellular molecules involved in the mutability modulation.

    Methods: To test the mutation-modulating effects of the conditioned medium, human RS cells were cultured with medium derived by culturing human pancreatic cancer KP-4 cells, followed by irradiation with UV (mainly 254 nm in wavelength). Mutations were detected by phenotypic ouabain resistance and genetic base substitution of K-ras codon 12. Messenger RNA differential display was used to identify genes that were differentially expressed between conditioned medium-treated and mock-treated RSa cells. The influence of 78-kd glucose-regulated protein/immunoglobulin-binding protein (GRP78/BiP) expression on mutability was assessed by the down-regulation of GRP78/BiP using antisense oligonucleotides or antisense complementary DNA.

    Results: The UV-induced mutagenicity in RS cells was strengthened by preculture with KP-4 cell-conditioned medium. Messenger RNA differential display revealed that GRP78/BiP expression was suppressed in RS cells after treatment of the conditioned medium. Furthermore, the level of UV-induced mutations was elevated significantly in GRP78/BiP down-regulated cells.

    Conclusions: Culture of human RS cells with pancreatic cancer KP-4 cell-conditioned medium resulted in increased UV mutagenicity, possibly via the down-regulation of GRP78/BiP.

    Pancreas 2008;36;1;e7-14

  • GRP78 and Cripto form a complex at the cell surface and collaborate to inhibit transforming growth factor beta signaling and enhance cell growth.

    Shani G, Fischer WH, Justice NJ, Kelber JA, Vale W and Gray PC

    Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, La Jolla, CA, 92037, USA.

    Cripto is a multifunctional cell surface protein with important roles in vertebrate embryogenesis and the progression of human tumors. While Cripto has been shown to modulate multiple signaling pathways, its binding partners do not appear to fully explain its molecular actions. Therefore, we conducted a screen aimed at identifying novel Cripto-interacting proteins. This screen led to our identification of glucose-regulated protein 78 (GRP78), an endoplasmic reticulum (ER) chaperone that is also expressed at the surfaces of tumor cells. Here we demonstrate that Cripto and GRP78 interact at the cell surfaces of multiple cell lines and that their interaction is independent of prior association within the ER. Interestingly, short hairpin RNA knockdown of endogenous GRP78 resulted in enhanced transforming growth factor beta (TGF-beta) signaling, indicating that like Cripto, GRP78 inhibits this pathway. We further show that when coexpressed, GRP78 and Cripto collaborate to antagonize TGF-beta responses, including Smad phosphorylation and growth inhibition of prostate cancer cells grown under anchorage-dependent or -independent conditions. Finally, we provide evidence that cells coexpressing GRP78 and Cripto grow much more rapidly in soft agar than do cells expressing either protein individually. Together, our results indicate that these proteins bind at the cell surface to enhance tumor growth via the inhibition of TGF-beta signaling.

    Funded by: NCI NIH HHS: R01 CA107420, R01CA107420

    Molecular and cellular biology 2008;28;2;666-77

  • Human cytomegalovirus specifically controls the levels of the endoplasmic reticulum chaperone BiP/GRP78, which is required for virion assembly.

    Buchkovich NJ, Maguire TG, Yu Y, Paton AW and Alwine JC

    Department of Cancer Biology, 314 Biomedical Research Building, 421 Curie Blvd., School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6142, USA.

    The endoplasmic reticulum (ER) chaperone BiP/GRP78 regulates ER function and the unfolded protein response (UPR). Human cytomegalovirus infection of human fibroblasts induces the UPR but modifies it to benefit viral replication. BiP/GRP78 protein levels are tightly regulated during infection, rising after 36 h postinfection (hpi), peaking at 60 hpi, and decreasing thereafter. To determine the effects of this regulation on viral replication, BiP/GRP78 was depleted using the SubAB subtilase cytotoxin, which rapidly and specifically cleaves BiP/GRP78. Toxin treatment of infected cells for 12-h periods beginning at 36, 48, 60, and 84 hpi caused complete loss of BiP but had little effect on viral protein synthesis. However, progeny virion formation was significantly inhibited, suggesting that BiP/GRP78 is important for virion formation. Electron microscopic analysis showed that infected cells were resistant to the toxin and showed none of the cytotoxic effects seen in uninfected cells. However, all viral activity in the cytoplasm ceased, with nucleocapsids remaining in the nucleus or concentrated in the cytopl 585 asmic space just outside of the outer nuclear membrane. These data suggest that one effect of the controlled expression of BiP/GRP78 in infected cells is to aid in cytoplasmic virion assembly and egress.

    Funded by: NCI NIH HHS: CA28379, R01 CA028379

    Journal of virology 2008;82;1;31-9

  • Reduction of GRP78 expression with siRNA activates unfolded protein response leading to apoptosis in HeLa cells.

    Suzuki T, Lu J, Zahed M, Kita K and Suzuki N

    Department of Environmental Biochemistry, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8670, Japan. piesuke@faculty.chiba-u.jp

    The 78-kDa glucose-regulated protein GRP78 is a central regulator of endoplasmic reticulum (ER) homeostasis, functioning in protein folding, ER calcium binding and modulation of transmembrane ER stress sensor activity. ER stress uncouples the interaction between GRP78 and ER stress sensors, leading to activation of the unfolded protein response (UPR), including upregulation of ER chaperone proteins. In the present study, we observed unexpected and remarkable induction of glucose-regulated protein 94 (GRP94) in HeLa cells following their transfection with 2'-O-methyl-modified siRNA specific to GRP78 mRNA. Additionally, we found that this siRNA also increased the expression of other UPR-induced genes, such as CHOP, ERdj4 and P5. Activation of UPR-dependent transcription and induction of apoptosis were also observed in cells transfected with GRP78 siRNA. Induction of apoptosis by GRP78 siRNA was also observed in PC-3 cells, which expressed high basal levels of GRP78 protein similar to that observed in HeLa cells. By contrast, five other human cell lines with lower basal expression of GRP78 protein did not undergo apoptosis when treated with GRP78 siRNA. Possible reasons for the strong activation of the UPR and apoptosis induced by GRP78 knockdown in HeLa cells, and the therapeutic utility of 2'-O-methyl-modified GRP78 siRNAs in anticancer treatment, are discussed.

    Archives of biochemistry and biophysics 2007;468;1;1-14

  • The endoplasmic reticulum in pancreatic beta cells of type 2 diabetes patients.

    Marchetti P, Bugliani M, Lupi R, Marselli L, Masini M, Boggi U, Filipponi F, Weir GC, Eizirik DL and Cnop M

    Department of Endocrinology and Metabolism, Metabolic Unit, Ospedale Cisanello, University of Pisa, Via Paradisa 2, 56100, Pisa, Italy. marchant@immr.med.unipi.it

    Pancreatic beta cells have highly developed endoplasmic reticulum (ER) due to their role in insulin secretion. Since ER stress has been associated with beta cell dysfunction, we studied several features of beta cell ER in human type 2 diabetes.

    Methods: Pancreatic samples and/or isolated islets from non-diabetic controls (ND) and type 2 diabetes patients were evaluated for insulin secretion, apoptosis (electron microscopy and ELISA), morphometric ER assessment (electron microscopy), and expression of ER stress markers in beta cell prepared by laser capture microdissection and in isolated islets.

    Results: Insulin release was lower and beta cell apoptosis higher in type 2 diabetes than ND islets. ER density volume was significantly increased in type 2 diabetes beta cells. Expression of alpha-mannosidase (also known as mannosidase, alpha, class 1A, member 1) and UDP-glucose glycoprotein glucosyl transferase like 2 (UGCGL2), assessed by microarray and/or real-time reverse transcriptase polymerase chain reaction (RT-PCR), differed between ND and type 2 diabetes beta cells. Expression of immunoglobulin heavy chain binding protein (BiP, also known as heat shock 70 kDa protein 5 [glucose-regulated protein, 78 kDa] [HSPA5]), X-box binding protein 1 (XBP-1, also known as XBP1) and C/EBP homologous protein (CHOP, also known as damage-inducible transcript 3 [DDIT3]) was not higher in type 2 diabetes beta cell or isolated islets cultured at 5.5 mmol/l glucose (microarray and real-time RT-PCR) than in ND samples. When islets were cultured for 24 h at 11.1 mmol/l glucose, there was induction of BiP and XBP-1 in type 2 diabetes islets but not in ND islets.

    Beta cell in type 2 diabetes showed modest signs of ER stress when studied in pancreatic samples or isolated islets maintained at physiological glucose concentration. However, exposure to increased glucose levels induced ER stress markers in type 2 diabetes islet cells, which therefore may be more susceptible to ER stress induced by metabolic perturbations.

    Diabetologia 2007;12;2486-94

  • Coupling cystic fibrosis to endoplasmic reticulum stress: Differential role of Grp78 and ATF6.

    Kerbiriou M, Le Drévo MA, Férec C and Trouvé P

    INSERM, U613, Brest, F-29200, France.

    Cystic fibrosis (CF) is the most common Caucasian autosomal recessive disease. It is due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene encoding the CFTR protein, which is a chloride (Cl(-)) channel. The most common mutation leads to a missing phenylalanine at position 508 (DeltaF508). The DeltaF508-CFTR protein is misfolded and retained in the endoplasmic reticulum and may trigger the unfolded protein response (UPR). Furthermore, CF is accompanied by inflammation and infection, which are also involved in the UPR. To date, the UPR transducer ATF6 and ER stress sensor Grp78 have been used as UPR markers. Therefore, our aim was to study the activation of ATF6 and Grp78 in transfected human epithelial cells expressing the DeltaF508-CFTR protein, and we showed that they are activated in these cells. We investigated the effect of exogenous UPR inducers thapsigargin (Tg) and tunicamycin (Tu) on Grp78 and ATF6 expression. Whereas the cells reacted to the UPR induction, we show a difference in the electrophoretic pattern of ATF6. The Grp78/ATF6 complex was previously described, but its stability during UPR is controversial. Using co-immunoprecipitation we show that it is stable in DeltaF508-CFTR-expressing cells and is maintained under UPR conditions. Finally, using siRNA, we show that decreased ATF6 expression induces increased cAMP-dependent halide flux through DeltaF508-CFTR due to its increased membrane localization. Therefore, our results suggest that UPR may be triggered in CF and that ATF6 may be a therapeutic target.

    Biochimica et biophysica acta 2007;11-12;1236-49

  • Expression of the endoplasmic reticulum stress response marker, BiP, in the central nervous system of HIV-positive individuals.

    Lindl KA, Akay C, Wang Y, White MG and Jordan-Sciutto KL

    Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104-6030, USA.

    The prevalence of HIV-associated neurocognitive impairment (NCI), which includes HIV-associated dementia (HAD) and minor cognitive and motor disorder (MCMD), has been increasing. HIV-infected and/or activated macrophages/microglia in the brain initiate the neurodegeneration seen in HIV-associated NCI via soluble neurotoxic mediators, including reactive oxygen species, viral proteins and excitotoxins. Neurotoxic factors released by macrophages/microglia injure neurones directly and alter astrocytic homeostatic functions, which can lead to excitotoxicity and oxidative stress-mediated neuronal injury. Often, cells respond to oxidative stress by initiating the endoplasmic reticulum (ER) stress response. Thus, we hypothesize that ER stress response is activated in HIV-infected cortex. We used immunofluorescence and immunoblotting to assess expression patterns of the ER stress proteins, BiP and ATF6, in HIV-positive cortical autopsy tissue. Additionally, we performed immunofluorescence using cell type-specific markers to examine BiP staining in different cell types, including neurones, astrocytes and macrophages/microglia. We observed a significant increase in BiP expression by both immunoblotting and immunofluorescence in HIV-positive cortex compared with control tissue. Additionally, phenotypic analysis of immunofluorescence showed cell type-specific increases in BiP levels in neurones and astrocytes. Further, ATF-6beta, an ER stress response initiator, is up-regulated in the same patient group, as assessed by immunoblotting. These results suggest that ER stress response is activated in HIV-infected cortex. Moreover, data presented here indicate for the first time that numbers of macrophages/microglia increase in brains of MCMD patients, as has been observed in HAD.

    Funded by: NIAID NIH HHS: T32AI07632; NIMH NIH HHS: NIH-N01MH32002; NINDS NIH HHS: R01NS41202

    Neuropathology and applied neurobiology 2007;33;6;658-69

  • Plasminogen structural domains exhibit different functions when associated with cell surface GRP78 or the voltage-dependent anion channel.

    Gonzalez-Gronow M, Kaczowka SJ, Payne S, Wang F, Gawdi G and Pizzo SV

    Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA. gonza002@mc.duke.edu

    Both the voltage-dependent anion channel and the glucose-regulated protein 78 have been identified as plasminogen kringle 5 receptors on endothelial cells. In this study, we demonstrate that kringle 5 binds to a region localized in the N-terminal domain of the glucose-regulated protein 78, whereas microplasminogen does so through the C-terminal domain of the glucose-regulated protein 78. Both plasminogen fragments induce Ca(2+) signaling cascades; however, kringle 5 acts through voltage-dependent anion channel and microplasminogen does so via the glucose-regulated protein 78. Because trafficking of voltage-dependent anion channel to the cell surface is associated with heat shock proteins, we investigated a possible association between voltage-dependent anion channel and glucose-regulated protein 78 on the surface of 1-LN human prostate tumor cells. We demonstrate that these proteins co-localize, and changes in the expression of the glucoseregulated protein 78 affect the expression of voltage-dependent anion channel. To differentiate the functions of these receptor proteins, either when acting singly or as a complex, we employed human hexokinase I as a specific ligand for voltage-dependent anion channel, in addition to kringle 5. We show that kringle 5 inhibits 1-LN cell proliferation and promotes caspase-7 activity by a mechanism that requires binding to cell surface voltage-dependent anion channel and is inhibited by human hexokinase I.

    Funded by: NCI NIH HHS: CA 86344; NHLBI NIH HHS: HL 24066

    The Journal of biological chemistry 2007;282;45;32811-20

  • Endoplasmic reticulum chaperones stabilize nicotinic receptor subunits and regulate receptor assembly.

    Wanamaker CP and Green WN

    Department of Neurobiology and Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637, USA.

    We examined interactions between the endoplasmic reticulum (ER) chaperones calnexin (CN), ERp57, and immunological heavy chain-binding protein (BiP) and nicotinic acetylcholine receptor (nAChR) subunits. The three chaperones rapidly associate with newly synthesized nAChR subunits. Interactions between nAChR subunits and ERp57 occur via transient intermolecular disulfide bonds and do not require subunit N-linked glycosylation. The associations of ERp57 or CN with AChR subunits are long lived and prolong subunit lifetime approximately 10-fold. Coexpression of CN or ERp57 alone does not affect nAChR assembly or trafficking, but together they cause a significant decrease in nAChR expression and assembly. In contrast, associations with BiP are shorter lived and do not alter nAChR expression and assembly. However, a mutated BiP that slows its dissociation significantly increases its associations and decreases nAChR expression and assembly. Our results suggest that interactions with the chaperones regulate the levels of nAChRs assembled in the ER by stabilizing and sequestering subunits during assembly.

    Funded by: NINDS NIH HHS: R01 NS032693, R01 NS032693-05A1, R01 NS032693-06, R01 NS032693-07, R01 NS032693-08

    The Journal of biological chemistry 2007;282;43;31113-23

  • Sequential steps and checkpoints in the early exocytic compartment during secretory IgM biogenesis.

    Anelli T, Ceppi S, Bergamelli L, Cortini M, Masciarelli S, Valetti C and Sitia R

    Università Vita-Salute, San Raffaele Scientific Institute, Milano, Italy.

    The biogenesis of secretory IgM occurs stepwise under stringent quality control, formation of micro(2)L(2) preceding polymerization. How is efficiency of IgM secretion coupled to fidelity? We show here that ERp44, a soluble protein involved in thiol-mediated retention, interacts with ERGIC-53. Binding to this hexameric lectin contributes to ERp44 localization in the ER-golgi intermediate compartment. ERp44 and ERGIC-53 increase during B-lymphocyte differentiation, concomitantly with the onset of IgM polymerization. Both preferentially bind micro(2)L(2) and higher order intermediates. Their overexpression or silencing in non-lymphoid cells promotes or decreases secretion of IgM polymers, respectively. In IgM-secreting B-lymphoma cells, micro chains interact first with BiP and later with ERp44 and ERGIC-53. Our findings suggest that ERGIC-53 provides a platform that receives micro(2)L(2) subunits from the BiP-dependent checkpoint, assisting polymerization. In this process, ERp44 couples thiol-dependent assembly and quality control.

    Funded by: Telethon: GGP06155

    The EMBO journal 2007;26;19;4177-88

  • Expression of Hsp60 and Grp78 in the human endometrium and oviduct, and their effect on sperm functions.

    Lachance C, Bailey JL and Leclerc P

    Département d'Obstétrique et de Gynécologie, Centre de Recherche en Biologie de la Reproduction, Université Laval, Unité de Recherche en Ontogénie et Reproduction, Centre de recherche du CHUQ (CHUL), T1-49, 2705 boul. Laurier, Québec, QC, Canada G1V 4G2.

    Background: Within the female genital tract, spermatozoa undergo a series of membranous and intracellular transformations to become competent at fertilizing the oocyte. In the bovine, previous studies have shown that two oviductal proteins, heat shock protein 60 (Hsp60) and glucose regulated protein 78 (Grp78), bind to spermatozoa and may be involved in this acquisition of fertilizing competence.

    Methods: Immunohistochemical studies were performed on human endometrial and oviduct tissues to localize these two chaperones in the female genital tract. Human spermatozoa were incubated under capacitating conditions in the presence or absence of recombinant Hsp60 or Grp78. Following a 4-h incubation, the effects of these proteins were evaluated on sperm acrosomal integrity, motility, protein phosphotyrosine content and free intracellular calcium concentrations.

    Results: Both chaperones were present in the uterus and oviduct epithelial cells and were shown to bind to human spermatozoa. Incubation with either exogenous Hsp60 or Grp78 did not affect sperm viability, motility or acrosomal integrity. Hsp60 partially prevented the increase in p81 phosphotyrosine content induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine and both chaperones significantly increased the sperm intracellular calcium concentration. Moreover, the progesterone-induced increase in intracellular calcium was higher when sperm were pre-treated with either Hsp60 or Grp78.

    Conclusions: Our study suggests that these two proteins may affect human sperm intracellular signalling pathways and capacitation.

    Human reproduction (Oxford, England) 2007;22;10;2606-14

  • Glucose-regulated protein GRP78 is up-regulated in prostate cancer and correlates with recurrence and survival.

    Daneshmand S, Quek ML, Lin E, Lee C, Cote RJ, Hawes D, Cai J, Groshen S, Lieskovsky G, Skinner DG, Lee AS and Pinski J

    Section of Urologic Oncology, Division of Urology, Oregon Health & Science University, Portland, OR 97239, USA.

    Chemotherapy resistance is a significant contributor to treatment failure and death in men with hormone-refractory prostate cancer. One unexplored mechanism for drug resistance is the induction of stress response proteins referred to as the glucose-regulated proteins (GRPs). We sought to determine the level of expression of GRP78, the best characterized GRP in lymph node-positive prostate cancer. Archived, paraffin-embedded, radical prostatectomy specimens were obtained from 153 patients with lymph node-positive prostate cancer (stage D1). The level of GRP78 expression was determined by immunohistochemistry. We assessed the expression and specificity of GRP78 immunoreactivity in benign prostatic tissue, prostate cancer, and lymph node metastasis. We correlated the intensity of immunopositivity with prostate cancer recurrence and survival. Whereas immunohistochemical staining demonstrated that all prostate tissue was immunoreactive for GRP78, the intensity of expression was markedly higher in the primary tumor compared with areas of benign epithelium. GRP78 expression was also evident in lymph node metastases although less intensely than in the primary tumor. Patients with strong GRP78 immunoreactivity in the primary tumor are at higher risk for clinical recurrence (relative risk = 2.0, P = .019) and death (relative risk = 1.8, P = .024) than patients with weak GRP78 expression. This finding confirms that GRP78 protein expression is significantly higher in prostate cancer than in benign prostatic tissue. The intensity of expression is significantly associated with survival and clinical recurrence. GRP78 has considerable potential not only as a prognostic indicator but also as a potential therapeutic target.

    Human pathology 2007;38;10;1547-52

  • Systematic analysis of the protein interaction network for the human transcription machinery reveals the identity of the 7SK capping enzyme.

    Jeronimo C, Forget D, Bouchard A, Li Q, Chua G, Poitras C, Thérien C, Bergeron D, Bourassa S, Greenblatt J, Chabot B, Poirier GG, Hughes TR, Blanchette M, Price DH and Coulombe B

    Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada.

    We have performed a survey of soluble human protein complexes containing components of the transcription and RNA processing machineries using protein affinity purification coupled to mass spectrometry. Thirty-two tagged polypeptides yielded a network of 805 high-confidence interactions. Remarkably, the network is significantly enriched in proteins that regulate the formation of protein complexes, including a number of previously uncharacterized proteins for which we have inferred functions. The RNA polymerase II (RNAP II)-associated proteins (RPAPs) are physically and functionally associated with RNAP II, forming an interface between the enzyme and chaperone/scaffolding proteins. BCDIN3 is the 7SK snRNA methylphosphate capping enzyme (MePCE) present in an snRNP complex containing both RNA processing and transcription factors, including the elongation factor P-TEFb. Our results define a high-density protein interaction network for the mammalian transcription machinery and uncover multiple regulatory factors that target the transcription machinery.

    Funded by: Canadian Institutes of Health Research: 14309-3, 82851-1

    Molecular cell 2007;27;2;262-74

  • A genetic association analysis of cognitive ability and cognitive ageing using 325 markers for 109 genes associated with oxidative stress or cognition.

    Harris SE, Fox H, Wright AF, Hayward C, Starr JM, Whalley LJ and Deary IJ

    Department of Psychology, University of Edinburgh, Edinburgh, UK. Sarah.Harris@hgu.mrc.ac.uk <Sarah.Harris@hgu.mrc.ac.uk&gt;

    Background: Non-pathological cognitive ageing is a distressing condition affecting an increasing number of people in our 'ageing society'. Oxidative stress is hypothesised to have a major role in cellular ageing, including brain ageing.

    Results: Associations between cognitive ageing and 325 single nucleotide polymorphisms (SNPs), located in 109 genes implicated in oxidative stress and/or cognition, were examined in a unique cohort of relatively healthy older people, on whom we have cognitive ability scores at ages 11 and 79 years (LBC1921). SNPs showing a significant positive association were then genotyped in a second cohort for whom we have cognitive ability scores at the ages of 11 and 64 years (ABC1936). An intronic SNP in the APP gene (rs2830102) was significantly associated with cognitive ageing in both LBC1921 and a combined LBC1921/ABC1936 analysis (p < 0.01), but not in ABC1936 alone.

    Conclusion: This study suggests a possible role for APP in normal cognitive ageing, in addition to its role in Alzheimer's disease.

    Funded by: Medical Research Council: MRC_MC_U127561128

    BMC genetics 2007;8;43

  • Endoplasmic reticulum quality control regulates the fate of transthyretin variants in the cell.

    Sato T, Susuki S, Suico MA, Miyata M, Ando Y, Mizuguchi M, Takeuchi M, Dobashi M, Shuto T and Kai H

    Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.

    The secretion of transthyretin (TTR) variants contributes to the pathogenesis of amyloidosis because they form aggregates in the extracellular environment. However, the mechanism of how TTR variants pass the quality control system in the endoplasmic reticulum (ER) has not yet been elucidated. We investigated here the mechanism of how TTR passes ER monitoring. Monomeric mutation introduced in TTRs (M-TTRs) resulted in the ER retention of amyloidogenic M-TTRs but not non-amyloidogenic M-TTRs. Retention of amyloidogenic M-TTRs induced the unfolded protein response and upregulated the expression of ER chaperones BiP and glucose-regulated protein (GRP) 94. Additionally, we showed that the ER-retained amyloidogenic M-TTRs are subject to ER-associated degradation. On the other hand, the amyloidogenic TTR variants and non-amyloidogenic M-TTRs were secreted normally. These findings suggest that unlike for wild-type TTR, the ER quality control system may differentially regulate the fate of the TTR variants and their monomeric counterparts.

    The EMBO journal 2007;26;10;2501-12

  • Purification and identification of G protein-coupled receptor protein complexes under native conditions.

    Daulat AM, Maurice P, Froment C, Guillaume JL, Broussard C, Monsarrat B, Delagrange P and Jockers R

    Department of Cell Biology, Institut Cochin, INSERM U567, CNRS UMR 8104, Université Paris Descartes, France.

    G protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors and are of major therapeutic importance. The identification of GPCR-associated proteins is an important step toward a better understanding of these receptors. However, current methods are not satisfying as only isolated receptor domains (intracellular loops or carboxyl-terminal tails) can be used as "bait." We report here a method based on tandem affinity purification coupled to mass spectrometry that overcomes these limitations as the entire receptor is used to identify protein complexes formed in living mammalian cells. The human MT(1) and MT(2) melatonin receptors were chosen as model GPCRs. Both receptors were tagged with the tandem affinity purification tag at their carboxyl-terminal tails and expressed in human embryonic kidney 293 cells. Receptor solubilization and purification conditions were optimized. The method was validated by the co-purification of G(i) proteins, which are well known GPCR interaction partners but which are difficult to identify with current protein-protein interaction assays. Several new and functionally relevant MT(1)- and MT(2)-associated proteins were identified; some of them were common to both receptors, and others were specific for each subtype. Taken together, our protocol allowed for the first time the purification of GPCR-associated proteins under native conditions in quantities suitable for mass spectrometry analysis.

    Molecular & cellular proteomics : MCP 2007;6;5;835-44

  • Lafora disease proteins malin and laforin are recruited to aggresomes in response to proteasomal impairment.

    Mittal S, Dubey D, Yamakawa K and Ganesh S

    Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016, India.

    Lafora disease (LD), an autosomal recessive neurodegenerative disorder, is characterized by the presence of cytoplasmic polyglucosan inclusions known as Lafora bodies in several tissues including the brain. Laforin, a protein phosphatase, and malin, an ubiquitin ligase, are two of the proteins that are known to be defective in LD. Malin interacts with laforin and promotes its polyubiquitination and degradation. Here we show that malin and laforin co-localize in endoplasmic reticulum (ER) and that they form centrosomal aggregates when treated with proteasomal inhibitors in both neuronal and non-neuronal cells. Laforin/malin aggregates co-localize with gamma-tubulin and cause redistribution of alpha-tubulin. These aggregates are also immunoreactive to ubiquitin, ubiquitin-conjugating enzyme, ER chaperone and proteasome subunits, demonstrating their aggresome-like properties. Furthermore, we show that the centrosomal aggregation of laforin and malin is dependent on the functional microtubule network. Laforin and malin form aggresome when expressed together or otherwise, suggesting that the two proteins are recruited to the centrosome independent of each other. Taken together, our results suggest that the centrosomal accumulation of malin, possibly with the help of laforin, may enhance the ubiquitination of its substrates and facilitate their efficient degradation by proteasome. Defects in malin or laforin may thus lead to increased levels of misfolded and/or target proteins, which may eventually affect the physiological processes of the neuron. Thus, defects in protein degradation and clearance are likely to be the primary trigger in the physiopathology of LD.

    Human molecular genetics 2007;16;7;753-62

  • Proteomics analysis of the interactome of N-myc downstream regulated gene 1 and its interactions with the androgen response program in prostate cancer cells.

    Tu LC, Yan X, Hood L and Lin B

    Institute for Systems Biology, Seattle, Washington 98103, USA.

    NDRG1 is known to play important roles in both androgen-induced cell differentiation and inhibition of prostate cancer metastasis. However, the proteins associated with NDRG1 function are not fully enumerated. Using coimmunoprecipitation and mass spectrometry analysis, we identified 58 proteins that interact with NDRG1 in prostate cancer cells. These proteins include nuclear proteins, adhesion molecules, endoplasmic reticulum (ER) chaperons, proteasome subunits, and signaling proteins. Integration of our data with protein-protein interaction data from the Human Proteome Reference Database allowed us to build a comprehensive interactome map of NDRG1. This interactome map consists of several modules such as a nuclear module and a cell membrane module; these modules explain the reported versatile functions of NDRG1. We also determined that serine 330 and threonine 366 of NDRG1 were phosphorylated and demonstrated that the phosphorylation of NDRG1 was prominently mediated by protein kinase A (PKA). Further, we showed that NDRG1 directly binds to beta-catenin and E-cadherin. However, the phosphorylation of NDRG1 did not interrupt the binding of NDRG1 to E-cadherin and beta-catenin. Finally, we showed that the inhibition of NDRG1 expression by RNA interference decreased the ER inducible chaperon GRP94 expression, directly proving that NDRG1 is involved in the ER stress response. Intriguingly, we observed that many members of the NDRG1 interactome are androgen-regulated and that the NDRG1 interactome links to the androgen response network through common interactions with beta-catenin and heat shock protein 90. Therefore we overlaid the transcriptomic expression changes in the NDRG1 interactome in response to androgen treatment and built a dual dynamic picture of the NDRG1 interactome in response to androgen. This interactome map provides the first road map for understanding the functions of NDRG1 in cells and its roles in human diseases, such as prostate cancer, which can progress from androgen-dependent curable stages to androgen-independent incurable stages.

    Funded by: NCI NIH HHS: 1U54CA119347, 5P01CA085859, 5P50CA097186; NIDA NIH HHS: 1U54DA021519; NIGMS NIH HHS: 1P50GM076547, P50 GM076547

    Molecular & cellular proteomics : MCP 2007;6;4;575-88

  • Lack of association betw d5e een endoplasmic reticulum stress response genes and suicidal victims.

    Sakurai K, Nishiguchi N, Shirakawa O, Nushida H, Ueno Y, Maeda K and Hayashi Y

    Division of Molecular Medicine and Medical Genetics, International Center for Medical Research and Treatment (ICMRT), Kobe University Graduate School of Medicine.

    As lithium has been shown to have a protective effect against suicidal behavior, genes on which mood stabilizers act may be involved in biological susceptibility to suicide. A recent study showed that endoplasmic reticulum (ER) stress response was impaired in the bipolar disorders and the impairment was ameliorated by a mood stabilizer, valproate. We hypothesized that an alteration of ER stress response is involved in the biological susceptibility to suicide through genetic polymorphisms, and examined the association of polymorphisms of X-box binding protein 1 (XBP1) and heat shock 70-kDa protein 5 (HSPA5) genes with suicide. We found no significant difference in the distribution of these polymorphisms between the suicide victims and the controls. These results suggest that the polymorphisms examined in this study are not involved in the susceptibility to suicide of the Japanese.

    The Kobe journal of medical sciences 2007;53;4;151-5

  • Proteomic and bioinformatic characterization of the biogenesis and function of melanosomes.

    Chi A, Valencia JC, Hu ZZ, Watabe H, Yamaguchi H, Mangini NJ, Huang H, Canfield VA, Cheng KC, Yang F, Abe R, Yamagishi S, Shabanowitz J, Hearing VJ, Wu C, Appella E and Hunt DF

    Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.

    Melanin, which is responsible for virtually all visible skin, hair, and eye pigmentation in humans, is synthesized, deposited, and distributed in subcellular organelles termed melanosomes. A comprehensive determination of the protein composition of this organelle has been obstructed by the melanin present. Here, we report a novel method of removing melanin that includes in-solution digestion and immobilized metal affinity chromatography (IMAC). Together with in-gel digestion, this method has allowed us to characterize melanosome proteomes at various developmental stages by tandem mass spectrometry. Comparative profiling and functional characterization of the melanosome proteomes identified approximately 1500 proteins in melanosomes of all stages, with approximately 600 in any given stage. These proteins include 16 homologous to mouse coat color genes and many associated with human pigmentary diseases. Approximately 100 proteins shared by melanosomes from pigmented and nonpigmented melanocytes define the essential melanosome proteome. Proteins validated by confirming their intracellular localization include PEDF (pigment-epithelium derived factor) and SLC24A5 (sodium/potassium/calcium exchanger 5, NCKX5). The sharing of proteins between melanosomes and other lysosome-related organelles suggests a common evolutionary origin. This work represents a model for the study of the biogenesis of lysosome-related organelles.

    Funded by: NCRR NIH HHS: RR01744; NHGRI NIH HHS: U01-HG02712; NICHD NIH HHS: HD40179; NIGMS NIH HHS: GM 37537

    Journal of proteome research 2006;5;11;3135-44

  • Expression of stress response protein Grp78 is associated with the development of castration-resistant prostate cancer.

    Pootrakul L, Datar RH, Shi SR, Cai J, Hawes D, Groshen SG, Lee AS and Cote RJ

    Department of Pathology, University of Southern California, Keck School of Medicine/USC Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA.

    Background: Induction of molecular chaperone Grp78 (78-kDa glucose-regulated protein) occurs in stress conditions that often characterize tumor microenvironments. We investigated the role of Grp78 in prostate cancer progression and the development of castration resistance, where cancer cells continue to survive despite the stress of an androgen-starved environment.

    Immunohistochemistry was done to examine Grp78 expression in 219 prostate cancers from patients with pathologic stage T3N0M0 disease [androgen ablation naive (untreated) and androgen ablation exposed (treated)] and castration-resistant prostate cancer. Classification of tumors was based on intensity of Grp78 cytoplasmic immunoreactivity and percentage of immunoreactive tumor cells. The associations of Grp78 expression with prostate cancer recurrence (clinical and/or serum prostate-specific antigen) and survival were examined in the untreated stage T3N0M0 group. Grp78 expression was also analyzed in the androgen-dependent LNCaP and castration-resistant C42B cell lines.

    Results: The percentage of tumor cells expressing Grp78 was strongly associated with castration-resistant status (P = 0.005). Increased Grp78 expression was consistently associated with greater risk of prostate cancer recurrence and worse overall survival in patients who had not 1f40 undergone prior hormonal manipulation. Grp78 expression was also increased in the castration-resistant LNCaP-derived cell line C42B and in LNCaP cells grown in androgen-deprived conditions compared with LNCaP cells grown in androgen-rich media.

    Conclusion: Our findings show that up-regulation of Grp78 is associated with the development of castration resistance, possibly in part by augmenting cell survival as previously suggested, and may serve as an important prognostic indicator of recurrence in a subset of patients with T3N0M0 disease.

    Funded by: NCI NIH HHS: 1 R01 CA 111700-01A1, 1 R33 CA-1-3455-01, 5 R01 CA 027607-26, P30 CA 14089

    Clinical cancer research : an official journal of the American Association for Cancer Research 2006;12;20 Pt 1;5987-93

  • Constitutive nucleosome depletion and ordered factor assembly at the GRP78 promoter revealed by single molecule footprinting.

    Gal-Yam EN, Jeong S, Tanay A, Egger G, Lee AS and Jones PA

    Department of Urology, USC/Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America.

    Chromatin organization and transcriptional regulation are interrelated processes. A shortcoming of current experimental approaches to these complex events is the lack of methods that can capture the activation process on single promoters. We have recently described a method that combines methyltransferase M.SssI treatment of intact nuclei and bisulfite sequencing allowing the representation of replicas of single promoters in terms of protected and unprotected footprint modules. Here we combine this method with computational analysis to study single molecule dynamics of transcriptional activation in the stress inducible GRP78 promoter. We show that a 350-base pair region upstream of the transcription initiation site is constitutively depleted of nucleosomes, regardless of the induction state of the promoter, providing one of the first examples for such a promoter in mammals. The 350-base pair nucleosome-free region can be dissected into modules, identifying transcription factor binding sites and their combinatorial organization during endoplasmic reticulum stress. The interaction of the transcriptional machinery with the GRP78 core promoter is highly organized, represented by six major combinatorial states. We show that the TATA box is frequently occupied in the noninduced state, that stress induction results in sequential loading of the endoplasmic reticulum stress response elements, and that a substantial portion of these elements is no longer occupied following recruitment of factors to the transcription initiation site. Studying the positioning of nucleosomes and transcription factors at the single promoter level provides a powerful tool to gain novel insights into the transcriptional process in eukaryotes.

    Funded by: NCI NIH HHS: CA27607, CA82422, R01 CA027607, R01 CA082422, R37 CA082422

    PLoS genetics 2006;2;9;e160

  • BiP/GRP78 is an intracellular target for MDA-7/IL-24 induction of cancer-specific apoptosis.

    Gupta P, Walter MR, Su ZZ, Lebedeva IV, Emdad L, Randolph A, Valerie K, Sarkar D and Fisher PB

    Department of Pathology, Herbert Irving Comprehensive Cancer Center, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY 10032, USA.

    Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a unique member of the IL-10 gene family that induces cancer-selective growth suppression and apoptosis in a wide spectrum of human cancers in cell culture and animal models. Additionally, recent clinical trials confirm safety and document significant clinical activity of mda-7/IL-24 in patients with diverse solid cancers and melanomas. Despite intensive study the molecular basis of tumor-cell selectivity of mda-7/IL-24 is not well characterized. Using deletion analysis, a specific mutant of MDA-7/IL-24, M4, consisting of amino acids 104 to 206, is described that retains the cancer-specific growth-suppressive and apoptosis-inducing properties of the full-length protein. Employing rationally designed mutational analysis, we show that MDA-7/IL-24 and M4 physically interact with BiP/GRP78 through their C and F helices, localize in the endoplasmic reticulum, and activate p38 MAPK and GADD gene expression, culminating in cancer-selective apoptosis. These studies provide novel mechanistic insights into the discriminating antitumor activity of MDA-7/IL-24 by elucidating BiP/GRP78 as a defined intracellular target of action and present an unparalleled opportunity to develop improved therapeutic versions of this cancer-specific apoptosis-inducing cytokine.

    Funded by: NCI NIH HHS: CA097318, CA098712, P01 CA104177; NIAID NIH HHS: AI47300, R01 AI047300

    Cancer research 2006;66;16;8182-91

  • GRP78 as a novel predictor of responsiveness to chemotherapy in breast cancer.

    Lee E, Nichols P, Spicer D, Groshen S, Yu MC and Lee AS

    Department of Preventive Medicine, University of Southern California/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9176, USA.

    The discovery of predictive factors for chemoresistance is critical for improving adjuvant therapy for cancer patients. The 78-kDa glucose-regulated protein (GRP78), widely used as an indicator of the unfolded protein response (UPR), is induced in the tumor microenvironment. In vitro studies suggest that GRP78 confers chemoresistance to topoisomerase inhibitors, such as Adriamycin (doxorubicin). Here, we report on a retrospective cohort study of 127 stage II and III breast cancer patients who were treated with Adriamycin-based chemotherapy. Archival tumor specimens were available for analysis and the relationship of GRP78 expression level to "time to recurrence" (TTR), used as a surrogate marker for drug resistance, was examined. Our data show that 67% of the study subjects expressed high level of GRP78 in their tumors before the initiation of chemotherapy and suggest an association between GRP78 positivity and shorter TTR [hazard ratio (HR), 1.78; P = 0.16]. Interestingly, subgroup analysis reveals that the HR for the GRP78-positive group increased significantly among patients who did not receive further taxane treatment (HR, 3.00; P = 0.022) and among mastectomy patients (HR, 3.33; P = 0.027). The HR was even stronger among mastectomy patients who did not receive further taxane treatment (HR, 4.82; P = 0.010). The use of GRP78 as a predictor for chemoresponsiveness and the potential interaction of GRP78 and/or the UPR pathways with taxanes warrant larger studies.

    Cancer research 2006;66;16;7849-53

  • The role of BiP in endoplasmic reticulum-associated degradation of major histocompatibility complex class I heavy chain induced by cytomegalovirus proteins.

    Hegde NR, Chevalier MS, Wisner TW, Denton MC, Shire K, Frappier L and Johnson DC

    Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, 97239, USA.

    Human cytomegalovirus (HCMV1) US11 and US2 proteins cause rapid degradation of major histocompatibility complex (MHC) molecules, apparently by ligating cellular endoplasmic reticulum (ER)-associated degradation machinery. Here, we show that US11 and US2 bind the ER chaperone BiP. Four related HCMV proteins, US3, US7, US9, and US10, which do not promote degradation of MHC proteins, did not bind BiP. Silencing BiP reduced US11- and US2-mediated degradation of MHC class I heavy chain (HC) without altering the synthesis or translocation of HC into the ER or the stability of HC in the absence of US11 or US2. Induction of the unfolded protein response (UPR) did not affect US11-mediated HC degradation and could not explain the stabilization of HC when BiP was silenced. Unlike in yeast, BiP did not act by maintaining substrates in a retrotranslocation-competent form. Our studies go beyond previous observations in mammalian cells correlating BiP release with degradation, demonstrating that BiP is functionally required for US2- and US11-mediated HC degradation. Further, US2 and US11 bound BiP even when HC was absent and degradation of US2 depended on HC. These data were consistent with a model in which US2 and US11 bridge HC onto BiP promoting interactions with other ER-associated degradation proteins.

    Funded by: NEI NIH HHS: EY11245; NIAID NIH HHS: AI055051

    The Journal of biological chemistry 2006;281;30;20910-9

  • Activation and cross-talk between Akt, NF-kappaB, and unfolded protein response signaling in 1-LN prostate cancer cells consequent to ligation of cell surface-associated GRP78.

    Misra UK, Deedwania R and Pizzo SV

    Department of Pathology, Duke University, Medical Center, Durham, North Carolina 27710, USA.

    Binding of activated forms of the proteinase inhibitor alpha2-macroglobulin (alpha2M*) to cell surface-associated GRP78 on 1-LN human prostate cancer cells causes their proliferation. We have now examined the interplay between Akt activation, regulation of apoptosis, the unfolded protein response, and activation of NF-kappaB in alpha2M*-induced proliferation of 1-LN cells. Exposure of cells to alpha2M* (50 pM) induced phosphatidylinositol 3-kinase-dependent activation of Akt by phosphorylation at Thr-308 and Ser-473 with a concomitant 60-80% increase in Akt-associated kinase activity. ERK1/2 and p38 MAPK were also activated, but there was only a marginal effect on JNK activation. Treatment of 1-LN cells with alpha2M* down-regulated apoptosis and promoted NF-kappaB activation as shown by increases of Bcl-2, p-Bad(Ser-136), p-FOXO1(Ser-253), p-GSK3beta(Ser-9), XIAP, NF-kappaB, cyclin D1, GADD45beta, p-ASK1(Ser-83), and TRAF2 in a time of incubation-dependent manner. alpha2M* treatment of 1-LN cells, however, showed no increase in the activation of caspase -3, -9, or -12. Under these conditions, we observed increased unfolded protein response signaling as evidenced by elevated levels of GRP78, IRE1alpha, XBP-1, ATF4, ATF6, p-PERK, p-eIF2alpha, and GADD34 and reduced levels of GADD153. Silencing of GRP78 gene expression by RNAi suppressed activation of Akt(Thr-308), Akt(Ser-473), and IkappaB kinase alpha kinase. The effects of alpha2M* on the NF-kappaB activation, antiapoptotic signaling, unfolded protein response signaling, and proapoptotic signaling were also reversed by this treatment. In conclusion, alpha2M* promotes cellular proliferation of 1-LN prostate cancer cells by activating MAPK and Akt-dependent signaling, down-regulating apoptotic signaling, and activating unfolded protein response signaling.

    Funded by: NHLBI NIH HHS: HL-24066

    The Journal of biological chemistry 2006;281;19;13694-707

  • Induced endoplasmic reticulum (ER) stress and binding of over-expressed ER specific chaperone GRP78/BiP with dimerized epidermal growth factor receptor in mammalian cells exposed to low concentration of N-methyl-N'-nitro-N-nitrosoguanidine.

    Liu G, Shang Y and Yu Y

    Department of Pathology and Pathophysiology, Zhejiang University School of Medicine, Hangzhou 310031, China.

    Previously we have shown that alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) can induce the clustering of epidermal growth factor receptor (EGFR) in human amnion FL cells. However, the biological consequence of MNNG-induced clustering is different from that of epidermal growth factor (EGF)-induced clustering. In addition, MNNG strongly blocks the autophosphorylation of EGFR in response to its ligand, we speculate it might be due to the altered conformation of EGFR by MNNG alkylation, or the binding of some unknown suppressive molecules to EGFR, which could lead to the down-regulation of EGFR pathway. In this study, we further demonstrated that EGFR could not be phosphorylated by EGF in lysates prepared from MNNG-pretreated cell. In addition, it was found that the clustering of EGFR induced by low concentration (<or=1 microM) of MNNG on cell surface was indeed the dimerization of EGFR; however, unlike EGF treatment, the dimerization initiated by MNNG was irreversible upon mild-acid washing. Besides, in accordance with our previous results, the recruitment of adaptor proteins Grb-2/Sos1, which play key roles in activating ensuing RAS-MAPK pathway, was also suppressed. Interestingly, we found that endoplasmic reticulum (ER) stress participates in MNNG-induced down-regulation of EGFR signaling. It was demonstrated that the ER specific chaperone, glucose-regulated protein 78 (GRP78/BiP) formed a stable complex with EGFR in MNNG-treated cell. However, in the presence of 1mM ATP, EGF induced phosphorylation of tyrosine residues of EGFR can be revitalized in lysates prepared from MNNG pretreated cells. We also found that MNNG can induce ER stress or unfolded protein response (UPR) which is characterized by induced expression of ER-stress response proteins, such as GRP78/BiP, GADD153/CHOP, and activation of ER-localized caspase-12. Therefore, it is concluded MNNG is also an ER stress inducer. In MNNG-exposed cells, ER stress plays an important role in the blockage of EGFR-signaling pathway by forming a stable complex of EGFR/BiP.

    Mutation research 2006;596;1-2;12-21

  • Decreased protein and mRNA expression of ER stress proteins GRP78 and GRP94 in HepG2 cells over-expressing CYP2E1.

    Dey A, Kessova IG and Cederbaum AI

    Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029, USA.

    CYP2E1 causes oxidative stress mediated cell death; the latter is one mechanism for endoplasmic reticulum (ER) stress in the cell. Unfolded proteins accumulate during ER stress and ER resident proteins GRP78 and GRP94 protect cells against ER dysfunction. We examined the possible role of GRP78 and GRP94 as protective factors against CYP2E1-mediated toxicity in HepG2 cells expressing CYP2E1 (E47 cells). E47 cells expressed high levels of CYP2E1 protein and catalytic activity which is associated with increased ROS generation, lipid peroxidation and the elevated presence of ubiquinated and aggregated proteins as compared to control HepG2 C34 cells which do not express CYP2E1. The mRNA and protein expression of GRP78 and GRP94 were decreased in E47 cells compared to the C34 cells, which may explain the accumulation of ubiquinated and aggregated proteins. Expression of these GRP proteins was induced with the ER stress agent thapsigargin in E47 cells, and E47 cells were more resistant to the toxicity caused by thapsigargin and calcimycin, possibly due to this upregulation and also because of the high expression of GSH and antioxidant enzymes in E47 cells. Antioxidants such as trolox and N-acetylcysteine increased GRP78 and GRP94 levels in the E47 cells, suggesting that CYP2E1- derived oxidant stress was responsible for down regulation of these GRPs in the E47 cells. Thapsigargin mediated toxicity was decreased in cells treated with the antioxidant trolox indicating a role for oxidative stress in this toxicity. These results suggest that CYP2E1 mediated oxidative stress downregulates the expression of GRP proteins in HepG2 cells and oxidative stress is an important mechanism in causing ER dysfunction in these cells.

    Funded by: NIAAA NIH HHS: AA 06610

    Archives of biochemistry and biophysics 2006;447;2;155-66

  • Overexpression of glucose-regulated protein 78 in colon cancer.

    Xing X, Lai M, Wang Y, Xu E and Q

    Department of Pathology and Pathophysiology, Center for Environmental Genomics, School of Medicine, Zhejiang University, Hangzhou 310031, PR China.

    Background: The 78 kDa glucose-regulated protein (GRP78) has been implicated in the development of tumorigenicity, drug resistance, and cytotoxic immunology. We investigated the expression pattern of GRP78 at the protein and mRNA level in human colon carcinoma, colon adenoma and normal colon mucosa.

    Methods: Two-dimensional (2-D) gel electrophoresis, electrospray ionization tandem mass spectrometry, immunoblot analysis, reverse-transcriptase PCR and immunohistochemistry were used on colon normal and cancer tissues.

    Results: Comparative 2-D gel electrophoresis of individual-matched colon normal and cancer tissues revealed 15 protein spots with concordantly increased and 20 protein spots with concordantly decreased intensity in tumor tissue. Fourteen of these proteins were identified by tandem mass spectrometry. One of the identified proteins, GRP78, exhibited a marked up-regulation in colon cancer tissue. This result was further confirmed by Western blot and immunohistochemical analysis. Immunohistochemistry also revealed increased cytoplasmic GRP78 expression with progression along the normal tissue-adenoma-carcinoma sequence. However, to our surprise, there was essentially no difference in the relative mRNA expression levels of GRP78 between normal and colon tumors.

    Conclusions: Our findings indicate that overexpression of GRP78 protein may be an important biomarker for malignant transformation, and increased expression might be related with the posttranscriptional regulation of GRP78 in tumor tissues.

    Clinica chimica d5d acta; international journal of clinical chemistry 2006;364;1-2;308-15

  • Proteomic profiling of hepatocellular carcinoma in Chinese cohort reveals heat-shock proteins (Hsp27, Hsp70, GRP78) up-regulation and their associated prognostic values.

    Luk JM, Lam CT, Siu AF, Lam BY, Ng IO, Hu MY, Che CM and Fan ST

    Centre for the Study of Liver Disease and Department of Surgery, The University of Hong Kong, Hong Kong SAR, P. R. China. jmluk@hkucc.hku.hk

    To facilitate the identification of candidate molecular biomarkers that are linked to the pathogenesis of hepatocellular carcinoma (HCC), we investigated protein-expression profiles of 146 tissue specimens including 67 pairs of tumors and adjacent non-tumors resected from HCC patients as well as 12 normal livers by 2-DE. Among the 1800 spots displayed in the liver proteome, a total of 90 protein species were found to be significantly different between the three groups (P < 0.05). Three of the top candidate markers up-regulated in HCC, with high receiver operating characteristic (ROC) curves, were identified by MS/MS analysis and belonged to the chaperone members: heat-shock protein (Hsp)27, Hsp70 and glucose-regulated protein (GRP)78. Over-expression of these chaperone proteins in HCC tissues was confirmed by Western blotting and immunohistochemistry. In correlation with clinico-pathological parameters, expression of Hsp27 was linked to alpha-fetoprotein level (P = 0.007) whereas up-regulation of GRP78 was associated with tumor venous infiltration (P = 0.035). No significant association of Hsp70 with any pathologic features was observed. The present HCC proteome analysis revealed that in response to the stressful cancerous microenvironment, tumor cells strived to increase the expression of chaperone proteins for cyto-protective function and to enhance tumor growth and metastasis.

    Proteomics 2006;6;3;1049-57

  • Stress induction of GRP78/BiP and its role in cancer.

    Li J and Lee AS

    Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, 90089-9176, USA.

    GRP78, also referred to as BiP, is a central regulator of endoplasmic reticulum (ER) function due to its roles in protein folding and assembly, targeting misfolded protein for degradation, ER Ca(2+)-binding and controlling the activation of trans-membrane ER stress sensors. Further, due to its anti-apoptotic property, stress induction of GRP78 represents an important pro-survival component of the unfolded protein response. GRP78 is induced in a wide variety of cancer cells and cancer biopsy tissues. Recent progress, utilizing overexpression and siRNA approaches, establishes that GRP78 contributes to tumor growth and confers drug resistance to cancer cells. The discovery of GRP78 expression on the cell surface of cancer cells further leads to the development of new therapeutic approaches targeted against cancer, in particular, hypoxic tumors where GRP78 is highly induced. Progress has also been made in understanding how Grp78 is induced by ER stress. The identification of the transcription factors interacting with the ER stress response element leads to the discovery of multiple pathways whereby mammalian cells can sense ER stress and trigger the transcription of Grp78. In addition, advances have been made in understanding how Grp78 expression is regulated in the context of chromatin modification. This review summarizes the transcriptional regulation of Grp78, the molecular basis for the cytoprotective function of GRP78 and its role in cancer progression, drug resistance and potential future cancer therapy.

    Funded by: NCI NIH HHS: CA111700, CA27607

    Current molecular medicine 2006;6;1;45-54

  • Glucose regulated proteins 78 and 75 bind to the receptor for hyaluronan mediated motility in interphase microtubules.

    Kuwabara H, Yoneda M, Hayasaki H, Nakamura T and Mori H

    Department of Pathology, Osaka Medical College, 2-7, Takatsuki, Osaka 569-8686, Japan. pa2020@art.osaka-med.ac.jp

    The receptor for hyaluronan mediated motility (RHAMM), which is a hyaluronan-binding protein, is a centrosomal and microtubal protein. Here, we have identified two RHAMM-binding proteins, glucose regulated protein (GRP) 78 and GRP75, using co-immunoprecipitation analysis. These two proteins directly bound to glutathione-S-transferase-RHAMM fusion proteins. By double immunostaining, GRP78 and GRP75 colocalized with RHAMM in interphase microtubules, but were separated in mitotic spindles. Prevention of microtubule polymerization by TN-16 and vincristine sulfate induced RHAMM overexpression without a significant change in GRP78/75. Taken together, GRP78/75 and RHAMM complexes may stabilize microtubules in the interphase, associated with a downregulation of RHAMM. These results reveal a new biochemical activity of RHAMM.

    Biochemical and biophysical research communications 2006;339;3;971-6

  • The C-terminal region of cis-retinol/androgen dehydrogenase 1 (CRAD1) confers ER localization and in vivo enzymatic function.

    Lidén M, Tryggvason K and Eriksson U

    Ludwig Institute for Cancer Research, Stockholm Branch, Box 240, S-17177 Stockholm, Sweden.

    Retinoic acid is generated from retinol (vitamin A) by the sequential actions of two different classes of enzymes, retinol dehydrogenases and retinal dehydrogenases. Several enzymes implicated in this process have been identified and characterized in vitro. However, our understanding of the cell biological function and regulation of this process is limited. To get further knowledge regarding the regulation of RA biosynthesis, we have determined possible regulatory mechanisms at the transcriptional and post-transcriptional levels for the prototypic microsomal retinol dehydrogenase cis-retinol/androgen dehydrogenase 1 (CRAD1). We note that the expression and stability of the enzyme are only moderately controlled by the retinoid status. Instead, we find that the cytosolic tail dramatically affects the activity of the enzyme, and we have mapped the structural elements required for ER retention and in vivo functional activity, respectively. Although inactive tail-deletion mutants display an abnormal subcellular localization, restoration of ER localization per se is not sufficient for enzymatic activity suggesting that additional trans-acting components interacting with, or modifying, the cytosolic tail are required for controlling the activity of the enzyme in vivo.

    Experimental cell research 2005;311;2;205-17

  • Proteomic analysis of SUMO4 substrates in HEK293 cells under serum starvation-induced stress.

    Guo D, Han J, Adam BL, Colburn NH, Wang MH, Dong Z, Eizirik DL, She JX and Wang CY

    Center for Biotechnology and Genomic Medicine, Medical College of Georgia, 1120 15th Street, CA4098, Augusta, GA 30912, USA.

    The substrates of SUMO4, a novel member for the SUMO gene family, were characterized in HEK293 cells cultured under serum starvation by proteomic analysis. We identified 90 SUMO4 substrates including anti-stress proteins such as antioxidant enzymes and molecular chaperones or co-chaperones. The substrates also include proteins involved in the regulation of DNA repair and synthesis, RNA processing, protein degradation, and glucose metabolism. Several SUMO4-associated transcription factors were characterized by Western blot analyses. AP-1 was selected for in vitro conjugation assays to confirm SUMO4 sumoylation of these transcription factors. Further functional analyses of the transcription factors suggested that SUMO4 sumoylation represses AP-1 and AP-2alpha transcriptional activity, but enhances GR DNA binding capacity. These results demonstrate that SUMO4 sumoylation may play an important role in the regulation of intracellular stress.

    Biochemical and biophysical research communications 2005;337;4;1308-18

  • The gene disrupted in Marinesco-Sjögren syndrome encodes SIL1, an HSPA5 cochaperone.

    Anttonen AK, Mahjneh I, Hämäläinen RH, Lagier-Tourenne C, Kopra O, Waris L, Anttonen M, Joensuu T, Kalimo H, Paetau A, Tranebjaerg L, Chaigne D, Koenig M, Eeg-Olofsson O, Udd B, Somer M, Somer H and Lehesjoki AE

    Folkhälsan Institute of Genetics and Neuroscience Center, University of Helsinki, PO Box 63, FI-00014 Helsinki, Finland.

    We identified the gene underlying Marinesco-Sjögren syndrome, which is characterized by cerebellar ataxia, progressive myopathy and cataracts. We identified four disease-associated, predicted loss-of-function mutations in SIL1, which encodes a nucleotide exchange factor for the heat-shock protein 70 (HSP70) chaperone HSPA5. These data, together with the similar spatial and temporal patterns of tissue expression of Sil1 and Hspa5, suggest that disturbed SIL1-HSPA5 interaction and protein folding is the primary pathology in Marinesco-Sjögren syndrome.

    Nature genetics 2005;37;12;1309-11

  • Cooperation of ER-60 and BiP in the oxidative refolding of denatured proteins in vitro.

    Okudo H, Kato H, Arakaki Y and Urade R

    Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011.

    ER-60 is a PDI family protein that has protein thiol-disulfide oxidoreductase activity. It has been shown to associate with BiP in the endoplasmic reticulum. Here, we analyzed the cooperation of ER-60 and BiP in the oxidative refolding of denatured proteins in vitro. ER-60 facilitated the refolding of 20 or 30% of denatured alpha-lactalbumin or ribonuclease B during incubation for 80 min, and these levels of nearly doubled on the addition of BiP to the reaction mixture. BiP alone could not refold denatured ribonuclease B, but could refold denatured alpha-lactalbumin a little. Enhancement of oxidative refolding of alpha-lactalbumin by ER-60 could be detected only when ER-60 was present from the start of refolding. On surface plasmon resonance analysis, ER-60 was shown to associate with BiP. The association was not influenced by ATP or ADP. Domains a and/or b' of ER-60 were implicated in the association with BiP.

    Journal of biochemistry 2005;138;6;773-80

  • Functional polymorphisms of HSPA5: possible association with bipolar disorder.

    Kakiuchi C, Ishiwata M, Nanko S, Kunugi H, Minabe Y, Nakamura K, Mori N, Fujii K, Umekage T, Tochigi M, Kohda K, Sasaki T, Yamada K, Yoshikawa T and Kato T

    Laboratory for Molecular Dynamics of Mental Disorders, Brain Science Institute, RIKEN, Wako-shi, Saitama, Japan.

    Altered endoplasmic reticulum stress (ER) response signaling is suggested in bipolar disorder. Previously, we preliminarily reported the genetic association of HSPA5 (GRP78/BiP) with bipolar disorder. Here, we extended our analysis by increasing the number of Japanese case-control samples and NIMH Genetics Initiative bipolar trio samples (NIMH trios), and also analyzed schizophrenia samples. In Japanese, nominally significant association of one haplotype was observed in extended samples of bipolar disorder but not in schizophrenia. In NIMH trios, no association was found in total samples. However, an exploratory analysis suggested that the other haplotype was significantly over-transmitted to probands only from the paternal side. The associated haplotype in Japanese or NIMH pedigrees shared three common polymorphisms in the promotor, which was found to alter promotor activity. These findings suggested promotor polymorphisms of HSPA5 may affect the interindividual variability of ER stress response and may confer a genetic risk factor for bipolar disorder.

    Biochemical and biophysical research communications 2005;336;4;1136-43

  • Proteomics of human umbilical vein endothelial cells applied to etoposide-induced apoptosis.

    Bruneel A, Labas V, Mailloux A, Sharma S, Royer N, Vinh J, Pernet P, Vaubourdolle M and Baudin B

    Service de Biochimie A, Hôpital Saint-Antoine, AP-HP, Paris, France. arnaud.bruneel@sat.ap-hop-paris.fr

    We have undertaken to continue the proteomic study of human umbilical vein endothelial cells (HUVECs) using the combination of 2-DE, automated trypsin digestion, and PMF analysis after MALDI-TOF MS and peptide sequencing using nano LC-ESI-MS/MS. The overall functional characterization of the 162 identified proteins from primary cultures of HUVECs confirms the metabolic capabilities of endothelium and illustrates various cellular functions more related to cell motility and angiogenesis, protein folding, anti-oxidant defenses, signal transduction, proteasome pathway and resistance to apoptosis. In comparison with controls cells, the differential proteomic analysis of HUVECs treated by the pro-apoptotic topoisomerase inhibitor etoposide further revealed the variation of eight proteins, namely, GRP78, GRP94, valosin-containing protein, proteinase inhibitor 9, cofilin, 37-kDa laminin receptor protein, bovine apolipoprotein, and tropomyosin. These data suggest that etoposide-induced apoptosis of human vascular endothelial cells results from the intricate involvement of multiple apoptosis processes including at least the mitochondrial and the ER stress pathways. The presented 2-D pattern and protein database, as well as the data related to apoptosis of HUVECs, are available at http://www.huvec.com.

    Proteomics 2005;5;15;3876-84

  • A human protein-protein interaction network: a resource for annotating the proteome.

    Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H and Wanker EE

    Max Delbrueck Center for Molecular Medicine, 13092 Berlin-Buch, Germany.

    Protein-protein interaction maps provide a valuable framework for a better understanding of the functional organization of the proteome. To detect interacting pairs of human proteins systematically, a protein matrix of 4456 baits and 5632 preys was screened by automated yeast two-hybrid (Y2H) interaction mating. We identified 3186 mostly novel interactions among 1705 proteins, resulting in a large, highly connected network. Independent pull-down and co-immunoprecipitation assays validated the overall quality of the Y2H interactions. Using topological and GO criteria, a scoring system was developed to define 911 high-confidence interactions among 401 proteins. Furthermore, the network was searched for interactions linking uncharacterized gene products and human disease proteins to regulatory cellular pathways. Two novel Axin-1 interactions were validated experimentally, characterizing ANP32A and CRMP1 as modulators of Wnt signaling. Systematic human protein interaction screens can lead to a more comprehensive understanding of protein function and cellular processes.

    Cell 2005;122;6;957-68

  • Expression of endoplasmic reticulum molecular chaperone Grp78 in human lung cancer and its clinical significance.

    Uramoto H, Sugio K, Oyama T, Nakata S, Ono K, Yoshimastu T, Morita M and Yasumoto K

    Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Kitakyushu 807-8555, Japan. hidetaka@medmed.uoeh-u.ac.jp

    All eukaryotic cells respond to the accumulation of unfolded proteins in the endoplasmic reticulum (ER) by signaling an adaptive pathway termed the unfolded protein response (UPR). Glucose-regulated protein (Grp) 78 is a molecular chaperone involved in the UPR. The aim of this study was to detect Grp78 expression in lung cancer using immunohistochemical (IHC) staining, and also to evaluate the relationship between the Grp78 expression level and the prognosis of patients with lung cancer. We used immunohistochemistry to analyze the protein expression of Grp78 in paraffin-embedded tumor samples from 132 well-characterized lung cancer patients and compared the expression level of Grp78, clinical variables and survival outcome. A positive expression of Grp78 was detected in the cytoplasm of tumor cells in 88 of the 132 patients (66.7%) with lung cancer. No significant difference was observed between the Grp78 expression and the gender, age at operation, histological type, pathologic stage, pathologic T status, and pathologic N status. Lung cancer patients with a positive Grp78 expression tended to show a better prognosis than those with a negative Grp78 expression. In addition, a multivariate analysis of the clinicopathologic characteristics of lung cancer indicated a positive expression of Grp78 to be a significant factor for predicting a favorable prognosis (p < 0.001, risk ratio = 2.35). A positive expression of Grp78 may thus be a useful marker for predicting a favorable prognosis in patients undergoing a resection of lung cancer. The ER stress pathway mediated by Grp78 may therefore be responsible for controlling the growth of lung cancer cells.

    Lung cancer (Amsterdam, Netherlands) 2005;49;1;55-62

  • Endoplasmic reticulum stress induction of the Grp78/BiP promoter: activating mechanisms mediated by YY1 and its interactive chromatin modifiers.

    Baumeister P, Luo S, Skarnes WC, Sui G, Seto E, Shi Y and Lee AS

    Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, Keck School of Medicine, 1441 Eastlake Ave., Room 5308, MC-9176, Los Angeles, CA 90089-9176, USA.

    The unfolded protein response is an evolutionarily conserved mechanism whereby cells respond to stress conditions that target the endoplasmic reticulum (ER). The transcriptional activation of the promoter of GRP78/BiP, a prosurvival ER chaperone, has been used extensively as an indicator of the onset of the UPR. YY1, a constitutively expressed multifunctional transcription factor, activates the Grp78 promoter only under ER stress conditions. Previously, in vivo footprinting analysis revealed that the YY1 binding site of the ER stress response element of the Grp78 promoter exhibits ER stress-induced changes in occupancy. Toward understanding the underlying mechanisms of these unique phenomena, we performed chromatin immunoprecipitation analyses, revealing that YY1 only occupies the Grp78 promoter upon ER stress and is mediated in part by the nuclear form of ATF6. We show that YY1 is an essential coactivat 134a or of ATF6 and uncover their specific interactive domains. Using small interfering RNA against YY1 and insertional mutation of the gene encoding ATF6alpha, we provide direct evidence that YY1 and ATF6 are required for optimal stress induction of Grp78. We also discovered enhancement of the ER-stressed induction of the Grp78 promoter through the interaction of YY1 with the arginine methyltransferase PRMT1 and evidence of its action through methylation of the arginine 3 residue on histone H4. Furthermore, we detected ER stress-induced binding of the histone acetyltransferase p300 to the Grp78 promoter and histone H4 acetylation. A model for the ER stress-mediated transcription factor binding and chromatin modifications at the Grp78 promoter leading to its activation is proposed.

    Funded by: NCI NIH HHS: CA 27607, R01 CA027607; NIGMS NIH HHS: GM 53874, GM 58486, GM 64850, R01 GM053874, R01 GM058486, R01 GM064850

    Molecular and cellular biology 2005;25;11;4529-40

  • Expression of stress response protein glucose regulated protein-78 mediated by c-Myb.

    Ramsay RG, Ciznadija D, Mantamadiotis T, Anderson R and Pearson R

    Differentiation and Transcription Laboratory, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, St. Andrews Place, East Melbourne 3002, Australia. rob.ramsay@petermac.org

    Glucose regulated protein-78, GRP78 has been implicated in the protection of tumor cells from cytotoxic damage and apoptosis. When protein profiles of colon cell lines were investigated we found remarkably high GRP78 expression in two cell lines. These cell lines express elevated levels of the transcription factor c-Myb due to genomic amplification of the c-myb locus and we hypothesized that c-Myb regulates GRP78 expression in colon cancer cells. The promoters of human and murine GRP78 and the related family member GRP94 were examined and potential c-Myb binding sites were identified and characterized. DNA binding studies with recombinant c-Myb and nuclear extracts together with ChIP assays on colon cell lines validated these sites. Endogenous GRP78 expression was further induced in these colon cells in response to Thapsigargin treatment, a potent inducer of the unfolded protein response. Transactivation studies with the human GRP78 promoter in colon cell lines showed reporter activity was dependent upon the presence of a conserved c-Myb binding site independent of sequences associated with the unfolded protein response. Finally, over-expression of c-Myb induced the endogenous GRP78 gene. These data suggest that amplification of c-myb in tumor cells may lead to robust GRP78 gene induction, which may in turn assist cells in survival under conditions of oxygen deprivation and nutrient stress.

    The international journal of biochemistry & cell biology 2005;37;6;1254-68

  • Decreased cell survival and DNA repair capacity after UVC irradiation in association with down-regulation of GRP78/BiP in human RSa cells.

    Zhai L, Kita K, Wano C, Wu Y, Sugaya S and Suzuki N

    Department of Environmental Biochemistry, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chiba 260-8670, Japan.

    In contrast to extensive studies on the roles of molecular chaperones, such as heat shock proteins, there are only a few reports about the roles of GRP78/BiP, an endoplasmic reticulum (ER) stress-induced molecular chaperone, in mammalian cell responses to DNA-damaging stresses. To investigate whether GRP78/BiP is involved in resistance to a DNA-damaging agent, UVC (principally 254 nm in wavelength), we established human cells with down-regulation of GRP78/BiP by transfection of human RSa cells with antisense cDNA for GRP78/BiP. We found that the transfected cells showed higher sensitivity to UVC-induced cell death than control cells transfected with the vector alone. In the antisense-cDNA transfected cells, the removal capacities of the two major types of UVC-damaged DNA (thymine dimers and (6-4) photoproducts) in vivo and DNA synthesis activity of whole cell extracts to repair UVC-irradiated plasmids in vitro were remarkably decreased compared with those in the control cells. Furthermore, the antisense-cDNA transfected cells also showed slightly higher sensitivity to cisplatin-induced cell death than the control cells. Cisplatin-induced DNA damage is primarily repaired by nucleotide excision repair, like UVC-induced DNA damage. The present results suggest that GRP78/BiP plays a protective role against UVC-induced cell death possibly via nucleotide excision repair, at least in the human RSa cells tested.

    Experimental cell research 2005;305;2;244-52

  • Protein profiling of human pancreatic islets by two-dimensional gel electrophoresis and mass spectrometry.

    Ahmed M, Forsberg J and Bergsten P

    Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden. meftun.khandker@drl.ox.ac.uk

    Completion of the human genome sequence has provided scientists with powerful resources with which to explore the molecular events associated with disease states such as diabetes. Understanding the relative levels of expression of gene products, especially of proteins, and their post-translational modifications will be critical. However, though the pancreatic islets play a key role in glucose homeostasis, global protein expression data in human are decidedly lacking. We here report the two-dimensional protein map and database of human pancreatic islets. A high level of reproducibility was obtained among the gels and a total of 744 protein spots were detected. We have successfully identified 130 spots corresponding to 66 different protein entries and generated a reference map of human islets. The functionally characterized proteins include enzymes, chaperones, cellular structural proteins, cellular defense proteins, signaling molecules, and transport proteins. A number of proteins identified in this study (e.g., annexin A2, elongation factor 1-alpha 2, histone H2B.a/g/k, heat shock protein 90 beta, heat shock 27 kDa protein, cyclophilin B, peroxiredoxin 4, cytokeratins 7, 18, and 19) have not been previously described in the database of mouse pancreatic islets. In addition, altered expression of several proteins, like GRP78, GRP94, PDI, calreticulin, annexin, cytokeratins, profilin, heat shock proteins, and ORP150 have been associated with the development of diabetes. The data presented in this study provides a first-draft reference map of the human islet proteome, that will pave the way for further proteome analysis of pancreatic islets in both healthy and diabetic individuals, generating insights into the pathophysiology of this condition.

    Journal of proteome research 2005;4;3;931-40

  • Transcriptional regulation of the Grp78 promoter by endoplasmic reticulum stress: role of TFII-I and its tyrosine phosphorylation.

    Hong M, Lin MY, Huang JM, Baumeister P, Hakre S, Roy AL and Lee AS

    Department of Biochemistry and Molecular Biology and the University of Southern California/Norris Comprehensive Cancer Center, Keck School of Medicine of the University of Southern California, Los Angeles, California 90089-9176, USA.

    TFII-I is a signal-induced multi-functional transcription factor that has recently been implicated as a regulatory component of the endoplasmic reticulum (ER) stress response. TFII-I acts through ER stress-induced binding to the ER stress element, which is highly conserved in promoters of ER stress-inducible genes such as Grp78/BiP. Interestingly, its tyrosine phosphorylation sites are required for its activation of the Grp78 promoter. Toward understanding the link between TFII-I, the tyrosine kinase signaling pathway, and Grp78 activation, we discovered that Tg stress induces a dramatic increase of TFII-I phosphorylation at Tyr248 and localization of this form of TFII-I to the nucleus. Chromatin immunoprecipitation analysis further reveals enhanced TFII-I binding to the Grp78 promoter in vivo upon ER stress. Previously, we reported that genistein, a general inhibitor of tyrosine kinase, could suppress ER stress induction of Grp78 by inhibiting complex formation on the ER stress element; however, the mechanism is not known. Consistent with TFII-I being a target of genistein suppression, we observed that genistein could suppress Tg stress-induced phosphorylation of TFII-I. We further demonstrate that c-Src, which is one of kinases identified to mediate phosphorylation of TFII-I at Tyr248, is activated by Tg stress and is able to stimulate the Grp78 promoter activity. Lastly, using stable cell lines with suppressed TFII-I levels, we show that TFII-I is required for optimal induction of Grp78 by ER stress. Our studies provide a molecular link that connects the c-Src tyrosine kinase transduction pathway to ER stress-induced transcriptional activation of Grp78 mediated by TFII-I.

    Funded by: NCI NIH HHS: CA27607; NIAID NIH HHS: AI45150

    The Journal of biological chemistry 2005;280;17;16821-8

  • GRP78 expression correlates with histologic differentiation and favorable prognosis in neuroblastic tumors.

    Hsu WM, Hsieh FJ, Jeng YM, Kuo ML, Tsao PN, Lee H, Lin MT, Lai HS, Lai DM and Chen WJ

    Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.

    Glucose-regulated protein 78 (GRP78), an endoplasmic reticulum protein, is essential for the differentiation of neuroblastoma cells and is selectively induced when the cells are undergoing apoptosis. These findings suggest that GRP78 may affect the tumor behavior of neuroblastoma. Our study evaluates the association of clinicopathologic factors and patient survival with the expression of GRP78 in patients with neuroblastoma. GRP78 expression in 68 neuroblastic tumors was investigated semiquantitatively by immunohistochemistry. GRP78 mRNA and protein levels in 7 tumor tissues were also quantified by real-time PCR and Western blot respectively and correlated well with the immunohistochemical results. Forty (58.8%) of the 68 neuroblastic tumors showed positive GRP78 expression. The percentage of positive GRP78 immunostaining increased as the tumor histology became differentiated (p = 0.001). Furthermore, positive GRP78 expression strongly correlated with early clinical stages (P = 0.002) but inversely correlated with MYCN amplification (p = 0.001). Kaplan-Meier analysis showed that patients with positive GRP78 expression did have better survival than those with negative expression (5-year survival rate, 72.9% and 23.4% respectively, p < 0.001). Multivariate analysis further showed that GRP78 expression was an independent prognostic factor. Moreover, GRP78 expression predicted better survival in patients with either undifferentiated or differentiated histologies. GRP78 expression still had significant prognostic value when the analysis was restricted to tumors of advanced stages or without MYCN amplification. Thus, GRP78 can serve as a novel independent favorable prognostic factor for patients with neuroblastoma.

    International journal of cancer 2005;113;6;920-7

  • Glucosamine-induced endoplasmic reticulum stress promotes ApoB100 degradation: evidence for Grp78-mediated targeting to proteasomal degradation.

    Qiu W, Kohen-Avramoglu R, Mhapsekar S, Tsai J, Austin RC and Adeli K

    Division of Clinical Biochemistry, Department of Laboratory Medicine & Pathobiology, Hospital for Sick Children, University of Toronto, Ontario, Canada.

    Objective: To investigate the role of glucosamine-mediated endoplasmic reticulum (ER) stress and Grp78 (BiP) in the intracellular degradation of apolipoprotein B100 (apoB100) in cultured hepatocytes.

    Glucosamine treatment (2.5 to 10 mmol/L) of HepG2 cells increased levels of the ER chaperones, 78-kDa glucose-regulated protein (Grp78) and Grp94, in a dose-dependent manner and led to significant decreases in both cellular and secreted apoB100 by up to 97% (P<0.01). In contrast, no changes were observed in ER resident (ER60, PTP-1B) or secretory (albumin, apoE) control proteins. Glucosamine-induced apoB degradation was similarly observed in primary hamster hepatocytes and McA-RH7777 cells. Glucosamine treatment led to reduced tranlocational efficiency of apoB100 in the ER and enhanced its ubiquitination and proteasomal degradation. Adenoviral overexpression of Grp78 also led to significantly decreased levels of newly synthesized apoB100 in a dose-dependent manner (P<0.01). Grp78-induced downregulation of apoB100 was sensitive to inhibition by the proteasome inhibitor, lactacystin, but not lysosomal protease inhibitors, E64 and leupeptin, suggesting that overexpression of Grp78 selectively induced proteasomal degradation of apoB100.

    Conclusions: These findings suggest that binding and retention by Grp78 may play a critical role in proteasomal targeting and the ER quality-control of misfolded apoB. Interaction with core lipoprotein lipids may facilitate apoB transport out of the ER by reducing Grp78-mediated ER retention.

    Arteriosclerosis, thrombosis, and vascular biology 2005;25;3;571-7

  • Stable binding of ATF6 to BiP in the endoplasmic reticulum stress response.

    Shen J, Snapp EL, Lippincott-Schwartz J and Prywes R

    Department of Biological Sciences, Columbia University, Fairchild 813B, MC 2420, 1212 Amsterdam Avenue, New York, NY 10027, USA.

    Endoplasmic reticulum (ER) stress-induced activation of ATF6, an ER membrane-bound transcription factor, requires 1722 a dissociation step from its inhibitory regulator, BiP. It has been generally postulated that dissociation of the BiP-ATF6 complex is a result of the competitive binding of misfolded proteins generated during ER stress. Here we present evidence against this model and for an active regulatory mechanism for dissociation of the complex. Contradictory to the competition model that is based on dynamic binding of BiP to ATF6, our data reveal relatively stable binding. First, the complex was easily isolated, in contrast to many chaperone complexes that require chemical cross-linking. Second, ATF6 bound at similar levels to wild-type BiP and a BiP mutant form that binds substrates stably because of a defect in its ATPase activity. Third, ER stress specifically induced the dissociation of BiP from ER stress transducers while the competition model would predict dissociation from any specific substrate. Fourth, the ATF6-BiP complex was resistant to ATP-induced dissociation in vitro when isolated without detergents, suggesting that cofactors stabilize the complex. In favor of an active dissociation model, one specific region within the ATF6 lumenal domain was identified as a specific ER stress-responsive sequence required for ER stress-triggered BiP release. Together, our results do not support a model in which competitive binding of misfolded proteins causes dissociation of the BiP-ATF6 complex in stressed cells. We propose that stable BiP binding is essential for ATF6 regulation and that ER stress dissociates BiP from ATF6 by actively restarting the BiP ATPase cycle.

    Funded by: NCI NIH HHS: CA 50329, R01 CA050329

    Molecular and cellular biology 2005;25;3;921-32

  • Nucleolar proteome dynamics.

    Andersen JS, Lam YW, Leung AK, Ong SE, Lyon CE, Lamond AI and Mann M

    Department of Biochemistry and Molecular Biology, Campusvej 55, DK-5230 Odense M, Denmark.

    The nucleolus is a key organelle that coordinates the synthesis and assembly of ribosomal subunits and forms in the nucleus around the repeated ribosomal gene clusters. Because the production of ribosomes is a major metabolic activity, the function of the nucleolus is tightly linked to cell growth and proliferation, and recent data suggest that the nucleolus also plays an important role in cell-cycle regulation, senescence and stress responses. Here, using mass-spectrometry-based organellar proteomics and stable isotope labelling, we perform a quantitative analysis of the proteome of human nucleoli. In vivo fluorescent imaging techniques are directly compared to endogenous protein changes measured by proteomics. We characterize the flux of 489 endogenous nucleolar proteins in response to three different metabolic inhibitors that each affect nucleolar morphology. Proteins that are stably associated, such as RNA polymerase I subunits and small nuclear ribonucleoprotein particle complexes, exit from or accumulate in the nucleolus with similar kinetics, whereas protein components of the large and small ribosomal subunits leave the nucleolus with markedly different kinetics. The data establish a quantitative proteomic approach for the temporal characterization of protein flux through cellular organelles and demonstrate that the nucleolar proteome changes significantly over time in response to changes in cellular growth conditions.

    Funded by: Wellcome Trust: 073980

    Nature 2005;433;7021;77-83

  • ERdj3, a stress-inducible endoplasmic reticulum DnaJ homologue, serves as a cofactor for BiP's interactions with unfolded substrates.

    Shen Y and Hendershot LM

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.

    We recently identified ERdj3 as a component of unassembled immunoglobulin (Ig) heavy chain:BiP complexes. ERdj3 also associates with a number of other protein substrates, including unfolded light chains, a nonsecreted Ig light chain mutant, and the VSV-G ts045 mutant at the nonpermissive temperature. We produced an ERdj3 mutant that was unable to stimulate BiP's ATPase activity in vitro or to bind BiP in vivo. This mutant retained the ability to interact with unfolded protein substrates, suggesting that ERdj3 binds directly to proteins instead of via interactions with BiP. BiP remained bound to unfolded light chains longer than ERdj3, which interacted with unfolded light chains initially, but quickly disassociated before protein folding was completed. This suggests that ERdj3 may bind first to substrates and serve to inhibit protein aggregation until BiP joins the complex, whereas BiP remains bound until folding is complete. Moreover, our findings support a model where interactions with BiP help trigger the release of ERdj3 from the substrate:BiP complex.

    Funded by: NCI NIH HHS: CA21765, P30 CA021765; NIGMS NIH HHS: GM-54068, R01 GM054068

    Molecular biology of the cell 2005;16;1;40-50

  • Proteomics of endoplasmic reticulum-Golgi intermediate compartment (ERGIC) membranes from brefeldin A-treated HepG2 cells identifies ERGIC-32, a new cycling protein that interacts with human Erv46.

    Breuza L, Halbeisen R, Jenö P, Otte S, Barlowe C, Hong W and Hauri HP

    Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.

    Cycling proteins play important roles in the organization and function of the early secretory pathway by participating in membrane traffic and selective transport of cargo between the endoplasmic reticulum (ER), the intermediate compartment (ERGIC), and the Golgi. To identify new cycling proteins, we have developed a novel procedure for the purification of ERGIC membranes from HepG2 cells treated with brefeldin A, a drug known to accumulate cycling proteins in the ERGIC. Membranes enriched 110-fold over the homogenate for ERGIC-53 were obtained and analyzed by mass spectrometry. Major proteins corresponded to established and putative cargo receptors and components mediating protein maturation and membrane traffic. Among the uncharacterized proteins, a 32-kDa protein termed ERGIC-32 is a novel cycling membrane protein with sequence homology to Erv41p and Erv46p, two proteins enriched in COPII vesicles of yeast. ERGIC-32 localizes to the ERGIC and partially colocalizes with the human homologs of Erv41p and Erv46p, which mainly localize to the cis-Golgi. ERGIC-32 interacts with human Erv46 (hErv46) as revealed by covalent cross-linking and mistargeting experiments, and silencing of ERGIC-32 by small interfering RNAs increases the turnover of hErv46. We propose that ERGIC-32 functions as a modulator of the hErv41-hErv46 complex by stabilizing hErv46. Our novel approach for the isolation of the ERGIC from BFA-treated cells may ultimately lead to the identification of all proteins rapidly cycling early in the secretory pathway.

    The Journal of biological chemistry 2004;279;45;47242-53

  • The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

    Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Morrin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J and MGC Project Team

    The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

    Funded by: PHS HHS: N01-C0-12400

    Genome research 2004;14;10B;2121-7

  • The WW domain-containing proteins interact with the early spliceosome and participate in pre-mRNA splicing in vivo.

    Lin KT, Lu RM and Tarn WY

    Institute of Biomedical Sciences, Academia Sinica, 128 Academy Rd., Section 2, Nankang, Taipei 11529, Taiwan.

    A growing body of evidence supports the coordination of mRNA synthesis and its subsequent processing events. Nuclear proteins harboring both WW and FF protein interaction modules bind to splicing factors as well as RNA polymerase II and may serve to link transcription with splicing. To understand how WW domains coordinate the assembly of splicing complexes, we used glutathione S-transferase fusions containing WW domains from CA150 or FBP11 in pull-down experiments with HeLa cell nuclear extract. The WW domains associate preferentially with the U2 small nuclear ribonucleoprotein and with splicing factors SF1, U2AF, and components of the SF3 complex. Accordingly, WW domain-associating factors bind to the 3' part of a pre-mRNA to form a pre-spliceosome-like complex. We performed both in vitro and in vivo splicing assays to explore the role of WW/FF domain-containing proteins in this process. However, although CA150 is associated with the spliceosome, it appears to be dispensable for splicing in vitro. Nevertheless, in vivo depletion of CA150 substantially reduced splicing efficiency of a reporter pre-mRNA. Moreover, overexpression of CA150 fragments containing both WW and FF domains activated splicing and modulated alternative exon selection, probably by facilitating 3' splice site recognition. Our results suggest an essential role of WW/FF domain-containing factors in pre-mRNA splicing that likely occurs in concert with transcription in vivo.

    Molecular and cellular biology 2004;24;20;9176-85

  • Proteomic, functional, and domain-based analysis of in vivo 14-3-3 binding proteins involved in cytoskeletal regulation and cellular organization.

    Jin J, Smith FD, Stark C, Wells CD, Fawcett JP, Kulkarni S, Metalnikov P, O'Donnell P, Taylor P, Taylor L, Zougman A, Woodgett JR, Langeberg LK, Scott JD and Pawson T

    Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.

    Background: 14-3-3 proteins are abundant and conserved polypeptides that mediate the cellular effects of basophilic protein kinases through their ability to bind specific peptide motifs phosphorylated on serine or threonine.

    Results: We have used mass spectrometry to analyze proteins that associate with 14-3-3 isoforms in HEK293 cells. This identified 170 unique 14-3-3-associated proteins, which show only modest overlap with previous 14-3-3 binding partners isolated by affinity chromatography. To explore this large set of proteins, we developed a domain-based hierarchical clustering technique that distinguishes structurally and functionally related subsets of 14-3-3 target proteins. This analysis revealed a large group of 14-3-3 binding partners that regulate cytoskeletal architecture. Inhibition of 14-3-3 phosphoprotein recognition in vivo indicates the general importance of such interactions in cellular morphology and membrane dynamics. Using tandem proteomic and biochemical approaches, we identify a phospho-dependent 14-3-3 binding site on the A kinase anchoring protein (AKAP)-Lbc, a guanine nucleotide exchange factor (GEF) for the Rho GTPase. 14-3-3 binding to AKAP-Lbc, induced by PKA, suppresses Rho activation in vivo.

    Conclusion: 14-3-3 proteins can potentially engage around 0.6% of the human proteome. Domain-based clustering has identified specific subsets of 14-3-3 targets, including numerous proteins involved in the dynamic control of cell architecture. This notion has been validated by the broad inhibition of 14-3-3 phosphorylation-dependent binding in vivo and by the specific analysis of AKAP-Lbc, a RhoGEF that is controlled by its interaction with 14-3-3.

    Funded by: NIDDK NIH HHS: DK44239

    Current biology : CB 2004;14;16;1436-50

  • Time-controlled transcardiac perfusion cross-linking for the study of protein interactions in complex tissues.

    Schmitt-Ulms G, Hansen K, Liu J, Cowdrey C, Yang J, DeArmond SJ, Cohen FE, Prusiner SB and Baldwin MA

    Institute for Neurodegenerative Disease, San Francisco, California 94143, USA. g.schmittulms@utoronto.ca

    Because of their sensitivity to solubilizing detergents, membrane protein assemblies are difficult to study. We describe a protocol that covalently conserves protein interactions through time-controlled transcardiac perfusion cross-linking (tcTPC) before disruption of tissue integrity. To validate tcTPC for identifying protein-protein interactions, we established that tcTPC allowed stringent immunoaffinity purification of the gamma-secretase complex in high salt concentrations and detergents and was compatible with mass spectrometric identification of cross-linked aph-1, presenilin-1 and nicastrin. We then applied tcTPC to identify more than 20 proteins residing in the vicinity of the cellular prion protein (PrPC), suggesting that PrP is embedded in specialized membrane regions with a subset of molecules that, like PrP, use a glycosylphosphatidylinositol anchor for membrane attachment. Many of these proteins have been implicated in cell adhesion/neuritic outgrowth, and harbor immunoglobulin C2 and fibronectin type III-like motifs.

    Funded by: NCRR NIH HHS: NCRR RR01614; NIA NIH HHS: AG010770, AG02132

    Nature biotechnology 2004;22;6;724-31

  • Inhibition of antigen-presenting cell function and stimulation of human peripheral blood mononuclear cells to express an antiinflammatory cytokine profile by the stress protein BiP: relevance to the treatment of inflammatory arthritis.

    Corrigall VM, Bodman-Smith MD, Brunst M, Cornell H and Panayi GS

    Department of Rheumatology, Guy's, King's, and St. Thomas' School of Medicine, Guy's Hospital, King's College London, London, UK. valerie.corrigal@kcl.ac.uk

    Objective: The stress protein and endoplasmic reticulum chaperone, immunoglobulin binding protein (BiP), is an autoantigen in rheumatoid arthritis (RA). Stress proteins, however, may have extracellular functions, mediated via cell surface receptors, that may include immunomodulatory functions. We sought to determine whether cell-free BiP is present in the synovial fluid (SF) of patients with RA and to further investigate the possible extracellular antiinflammatory and immunomodulatory properties of BiP in peripheral blood mononuclear cells (PBMCs) in vitro.

    Methods: The presence of BiP in SF was established by Western blotting. PBMCs were stimulated with exogenous recombinant human BiP, and cytokine production and cell proliferation were measured in the presence and absence of cell signaling inhibitors or neutralizing anti-interleukin-10 (anti-IL-10) monoclonal antibody. Cytokine levels were quantified by enzyme-linked immunosorbent assay, cell proliferation by tritiated thymidine uptake, and cell surface molecule expression by flow cytometry.

    Results: PBMCs responded to BiP with secretion of an antiinflammatory profile of cytokines. Although BiP stimulated the early production of tumor necrosis factor alpha (TNF alpha), the major cytokine induced was IL-10. Soluble TNF receptor II and IL-1 receptor antagonist secretion was also increased. Addition of SB203580, the MAPK p38 pathway inhibitor, partially inhibited the production of IL-10 and TNF alpha, whereas they were unaffected by the MAPK ERK-1/2 inhibitor PD98059. BiP also inhibited the recall antigen response by PBMCs to tuberculin purified protein derivative. Further investigation showed that incubation of monocytes in the presence of either BiP or IL-10 down-regulated CD86 and HLA-DR expression. The effect observed with IL-10 was transient compared with the long-lasting reduction induced by BiP.

    Conclusion: Extracellular BiP may stimulate immunomodulatory and antiinflammatory pathways, which are only partly due to the production of IL-10. These properties may be of relevance for the treatment of diseases such as RA.

    Arthritis and rheumatism 2004;50;4;1164-71

  • A physical and functional map of the human TNF-alpha/NF-kappa B signal transduction pathway.

    Bouwmeester T, Bauch A, Ruffner H, Angrand PO, Bergamini G, Croughton K, Cruciat C, Eberhard D, Gagneur J, Ghidelli S, Hopf C, Huhse B, Mangano R, Michon AM, Schirle M, Schlegl J, Schwab M, Stein MA, Bauer A, Casari G, Drewes G, Gavin AC, Jackson DB, Joberty G, Neubauer G, Rick J, Kuster B and Superti-Furga G

    Cellzome AG, Meyerhofstrasse 1, 69117 Heidelberg, Germany. tewis.bouwmeester@cellzome.com

    Signal transduction pathways are modular composites of functionally interdependent sets of proteins that act in a coordinated fashion to transform environmental information into a phenotypic response. The pro-inflammatory cytokine tumour necrosis factor (TNF)-alpha triggers a signalling cascade, converging on the activation of the transcription factor NF-kappa B, which forms the basis for numerous physiological and pathological processes. Here we report the mapping of a protein interaction network around 32 known and candidate TNF-alpha/NF-kappa B pathway components by using an integrated approach comprising tandem affinity purification, liquid-chromatography tandem mass spectrometry, network analysis and directed functional perturbation studies using RNA interference. We identified 221 molecular associations and 80 previously unknown interactors, including 10 new functional modulators of the pathway. This systems approach provides significant insight into the logic of the TNF-alpha/NF-kappa B pathway and is generally applicable to other pathways relevant to human disease.

    Nature cell biology 2004;6;2;97-105

  • Proteomics analysis of the centromere complex from HeLa interphase cells: UV-damaged DNA binding protein 1 (DDB-1) is a component of the CEN-complex, while BMI-1 is transiently co-localized with the centromeric region in interphase.

    Obuse C, Yang H, Nozaki N, Goto S, Okazaki T and Yoda K

    Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0101, Japan.

    CENP-A, a centromere-specific histone H3, is conserved throughout eukaryotes, and formation of CENP-A chromatin defines the active centromere region. Here, we report the isolation of CENP-A chromatin from HeLa interphase nuclei by chromatin immunoprecipitation using anti-CENP-A monoclonal antibody, and systematic identification of its components by mass spectrometric analyses. The isolated chromatin contained CENP-B, CENP-C, CENP-H, CENP-I/hMis 6 and hMis 12 as well as CENP-A, suggesting that the isolated chromatin may represent the centromere complex (CEN-complex). Mass spectrometric analyses of the CEN-complex identified approximately 40 proteins, including the previously reported centromere proteins and the proteins of unknown function. In addition, we unexpectedly identified a series of proteins previously reported to be related to functions other than chromosome segregation, such as uvDDB-1, XAP8, hSNF2H, FACTp180, FACTp80/SSRP1, polycomb group proteins (BMI-1, RING1, RNF2, HPC3 and PHP2), KNL5 and racGAP. We found that uvDDB-1 was actually localized to the centromeric region throughout cell cycle, while BMI-1 was transiently co-localized with the centromeres in interphase. These results give us new insights into the architecture, dynamics and function of centromeric chromatin in interphase nuclei, which might reflect regulation of cell proliferation and differentiation.

    Genes to cells : devoted to molecular & cellular mechanisms 2004;9;2;105-20

  • Nuclear coactivator-62 kDa/Ski-interacting protein is a nuclear matrix-associated coactivator that may couple vitamin D receptor-mediated transcription and RNA splicing.

    Zhang C, Dowd DR, Staal A, Gu C, Lian JB, van Wijnen AJ, Stein GS and MacDonald PN

    Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106, USA.

    Nuclear coactivator-62 kDa/Ski-interacting protein (NCoA62/SKIP) is a putative vitamin D receptor (VDR) and nuclear receptor coactivator protein that is unrelated to other VDR coactivators such as those in the steroid receptor coactivator (SRC) family. The mechanism through which NCoA62/SKIP functions in VDR-activated transcription is unknown. In the present study, we identified a nuclear localization sequence in the COOH terminus of NCoA62/SKIP and showed that NCoA62/SKIP was targeted to nuclear matrix subdomains. Chromatin immunoprecipitation studies revealed that endogenous NCoA62/SKIP associated in a 1,25-dihydroxyvitamin D3-dependent manner with VDR target genes in ROS17/2.8 osteosarcoma cells. A cyclic pattern of promoter occupancy by VDR, SRC-1, and NCoA62/SKIP was observed, with NCoA62/SKIP entering these promoter complexes after SRC-1. These studies provide strong support for the proposed role of NCoA62/SKIP as a VDR transcriptional coactivator, and they indicate that key mechanistic differences probably exist between NCoA62/SKIP and SRC coactivators. To explore potential mechanisms, NCoA62/SKIP-interacting proteins were purified from HeLa cell nuclear extracts and identified by mass spectrometry. The identified proteins represent components of the spliceosome as well as other nuclear matrix-associated proteins. Here, we show that a dominant negative inhibitor of NCoA62/SKIP (dnNCoA62/SKIP) interfered with appropriate splicing of transcripts derived from 1,25-dihydroxyvitamin D3-induced expression of a growth hormone minigene cassette. Taken together, these data show that NCoA62/SKIP has properties that are consistent with those of nuclear receptor coactivators and with RNA spliceosome components, thus suggesting a potential role for NCoA62/SKIP in coupling VDR-mediated transcription to RNA splicing.

    Funded by: NIAMS NIH HHS: R01 AR049069; NIDDK NIH HHS: DK53980

    The Journal of biological chemistry 2003;278;37;35325-36

  • gp120 neurotoxicity fails to induce heat shock defenses, while the over expression of hsp70 protects against gp120.

    Lim MC, Brooke SM and Sapolsky RM

    Department of Biological Sciences, Stanford University MC 5020, Stanford, CA 94305-5020, USA.

    gp120, the coat glycoprotein of HIV, can damage CNS neurons. This appears to mostly involve an indirect pathway in which gp120 infects microglia, triggering the release of cytokines and glutamatergic excitotoxins which then damage neurons. A well-characterized response of cells to insults is to mobilize the heat stress response, a defense that has a number of protective consequences. We tested the capacity of gp120, at a dose well-documented to be neurotoxic, to activate the heat shock response in cultures from cortex and hippocampus, two brain regions sensitive to the neurotoxic effects of gp120. We found that gp120 failed to induce expression of hsp70, hsp25 or hsp90 in cortical or hippocampal cultures, under conditions where induction can be demonstrated in response to other insults. The failure of gp120 to induce a heat shock response is significant because we subsequently demonstrated that such an induction would have been beneficial. Specifically, over expression of hsp70 with a herpes viral amplicon vector protected cultured hippocampal neurons from gp120 neurotoxicity.

    Funded by: NIMH NIH HHS: R01 MH 53814

    Brain research bulletin 2003;61;2;183-8

  • Endoplasmic reticulum chaperone protein GRP78 protects cells from apoptosis induced by topoisomerase inhibitors: role of ATP binding site in suppression of caspase-7 activation.

    Reddy RK, Mao C, Baumeister P, Austin RC, Kaufman RJ and Lee AS

    Department of Biochemistry and Molecular Biology and the USC/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9176, USA.

    A large number of correlative studies have established that the activation of the unfolded protein response (UPR) alters the cell's sensitivity to chemotherapeutic agents. Although the induction of the glucose-regulated proteins (GRPs) is commonly used as an indicator for the UPR, the direct role of the GRPs in conferring resistance to DNA damaging agents has not been proven. We report here that without the use of endoplasmic reticulum (ER) stress inducers, specific overexpression of GRP78 results in reduced apoptosis and higher colony survival when challenged with topoisomerase II inhibitors, etoposide and doxorubicin, and topoisomerase I inhibitor, camptothecin. While investigating the mechanism for the GRP78 protective effect against etoposide-induced cell death, we discovered that in contrast to the UPR, GRP78 overexpression does not result in G1 arrest or depletion of topoisomerase II. Caspase-7, an executor caspase that is associated with the ER, is activated by etoposide. We show here that specific expression of GRP78 blocks caspase-7 activation by etoposide both in vivo and in vitro, and this effect can be reversed by addition of dATP in a cell-free system. Recently, it was reported that ectopically expressed GRP78 and caspases-7 and -12 form a complex, thus coupling ER stress to the cell death program. However, the mechanism of how GRP78, a presumably ER lumen protein, can regulate cytosolic effectors of apoptosis is not known. Here we provide evidence that a subpopulation of GRP78 can exist as an ER transmembrane protein, as well as co-localize with caspase-7, as confirmed by fluorescence microscopy. Co-immunoprecipitation studies further reveal endogenous GRP78 constitutively associates with procaspase-7 but not with procaspase-3. Lastly, a GRP78 mutant deleted of its ATP binding domain fails to bind procaspase-7 and loses its protective effect against etoposide-induced apoptosis.

    Funded by: NCI NIH HHS: 2P30 CA14089, CA27607; NEI NIH HHS: EY03040; NIAID NIH HHS: AI42394

    The Journal of biological chemistry 2003;278;23;20915-24

  • Structure and intermolecular interactions of the luminal dimerization domain of human IRE1alpha.

    Liu CY, Xu Z and Kaufman RJ

    Howard Hughes Medical Institute, Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650, USA.

    Accumulation of unfolded proteins in the lumen of the endoplasmic reticulum activates a signal transduction cascade that culminates in the transcriptio 1ea nal induction of genes encoding adaptive functions. One proximal sensor for this unfolded protein response is the protein kinase/endoribonuclease IRE1alpha. IRE1alpha is a type-I transmembrane glycoprotein for which the N-terminal luminal domain (NLD) senses the accumulation of unfolded proteins. Previously we demonstrated that the NLD forms a stable ligand-independent dimer linked by disulfide bridges. In this report we have identified the cysteine residues responsible for intermolecu 1f40 lar disulfide bonding. However, this covalent interaction was not required for dimerization and/or signaling, suggesting that a cryptic dimer interface exists in the NLD that is independent of covalent disulfide interactions. Limited proteolysis of the NLD revealed characteristic fragments, all retaining the same N-terminal sequences as full-length NLD. Biochemical and functional studies using NLD truncation mutants indicated that the dimerization domain of the NLD is confined to the conserved motifs at the N-terminal regions where putative hydrophobic interactions exist. In addition, the peptide binding domain of the endoplasmic reticulum protein chaperone BiP interacted with the N-terminal region within the NLD. Our findings suggest that the NLD has at least two distinct types of interactions mediating dimerization and function in signaling, i.e. covalent interactions involving disulfide bond formation and hydrophobic interactions, with the hydrophobic interaction being the driving force for dimerization.

    Funded by: NHLBI NIH HHS: HL52173

    The Journal of biological chemistry 2003;278;20;17680-7

  • Overexpression of the 78-kDa glucose-regulated protein/immunoglobulin-binding protein (GRP78/BiP) inhibits tissue factor procoagulant activity.

    Watson LM, Chan AK, Berry LR, Li J, Sood SK, Dickhout JG, Xu L, Werstuck GH, Bajzar L, Klamut HJ and Austin RC

    Department of Pathology, McMaster University, Hamilton, Ontario L8V 1C3, Canada.

    Previous studies have demonstrated that overexpression of GRP78/BiP, an endoplasmic reticulum (ER)-resident molecular chaperone, in mammalian cells inhibits the secretion of specific coagulation factors. However, the effects of GRP78/BiP on activation of the coagulation cascade leading to thrombin generation are not known. In this study, we examined whether GRP78/BiP overexpression mediates cell surface thrombin generation in a human bladder cancer cell line T24/83 having prothrombotic characteristics. We report here that cells overexpressing GRP78/BiP exhibited significant decreases in cell surface-mediated thrombin generation, prothrombin consumption and the formation of thrombin-inhibitor complexes, compared with wild-type or vector-transfected cells. This effect was attributed to the ability of GRP78/BiP to inhibit cell surface tissue factor (TF) procoagulant activity (PCA) because conversion of factor X to Xa and factor VII to VIIa were significantly lower on the surface of GRP78/BiP-overexpressing cells. The additional findings that (i) cell surface factor Xa generation was inhibited in the absence of factor VIIa and (ii) TF PCA was inhibited by a neutralizing antibody to human TF suggests that thrombin generation is mediated exclusively by TF. GRP78/BiP overexpression did not decrease cell surface levels of TF, suggesting that the inhibition in TF PCA does not result from retention of TF in the ER by GRP78/BiP. The additional observations that both adenovirus-mediated and stable GRP78/BiP overexpression attenuated TF PCA stimulated by ionomycin or hydrogen peroxide suggest that GRP78/BiP indirectly alters TF PCA through a mechanism involving cellular Ca(2+) and/or oxidative stress. Similar results were also observed in human aortic smooth muscle cells transfected with the GRP78/BiP adenovirus. Taken together, these findings demonstrate that overexpression of GRP78/BiP decreases thrombin generation by inhibiting cell surface TF PCA, thereby suppressing the prothrombotic potential of cells.

    The Journal of biological chemistry 2003;278;19;17438-47

  • Activation of the ATF6, XBP1 and grp78 genes in human hepatocellular carcinoma: a possible involvement of the ER stress pathway in hepatocarcinogenesis.

    Shuda M, Kondoh N, Imazeki N, Tanaka K, Okada T, Mori K, Hada A, Arai M, Wakatsuki T, Matsubara O, Yamamoto N and Yamamoto M

    Department of Microbiology and Cell Biology, The Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.

    We identified the glucose-regulated protein (grp) 78 as a transformation-associated gene in hepatocellular carcinoma (HCC). Grp78 is a molecular chaperone involved in the unfolded protein response, the expression of which can be regulated by the transcription factors ATF6 and XBP1. Thus, we investigated the regulatory mechanisms of the grp78 gene in liver malignancy.

    Methods: Expression of grp78, ATF6 and XBP1 was examined by Northern blot, RT-PCR, immunoblot and immunohistochemical analyses. A reporter assay of the grp78 promoter was also performed.

    Results: Elevation of grp78 and ATF6 mRNAs and the splicing of XBP1 mRNA, resulting in the activation of XBP1 product, occurred in HCC tissues with increased histological grading. Higher accumulation of the grp78 product in the cytoplasm, concomitantly with marked nuclear localization of the activated ATF6 product (p50ATF6), was observed in moderately to poorly differentiated HCC tissues. Cooperation between the distal DNA segment and the proximal endoplasmic reticulum stress response elements was essential for maximum transcription of the grp78 promoter in HCC cells.

    Conclusions: The endoplasmic reticulum stress pathway mediated by ATF6 and by IRE1-XBP1 systems seems essential for the transformation-associated expression of the grp78 gene in HCCs.

    Journal of hepatology 2003;38;5;605-14

  • Cloning and characterization of a novel GRP78-binding protein in the rat brain.

    Oh-hashi K, Naruse Y, Amaya F, Shimosato G and Tanaka M

    Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamikyo-ku, Japan.

    The full-length cDNA clone of a novel GRP78-binding protein (GBP) was isolated from rat brain using PCR-selected cDNA subtraction. GBP was predominantly expressed in neuronal cells among various brain tissues. GBP mRNA was already detected in the E12 brain and then gradually increased to reach a peak within P0-2 weeks after birth. GBP expression in the brain decreased age-dependently to approximately 30% of the postnatal level at 12 months. GBP encoded 1021 amino acids and was predicted to have two transmembrane regions and glutamic acid- and proline-rich regions. Because the sequence of GBP offered few clues to the possible function, we performed a GST-tagged GBP pull-down assay in PC12 lysates and identified GRP78, one of the heat shock proteins, as a counterpart. Observation of COS7 cells expressing green fluorescent protein- or Myc-tagged GBP showed that GBP was localized in the endoplasmic reticulum-Golgi domain where BODIPY 558/568 (4,4-difluro-5-(2-thienyl)-4-bora-3alpha,4alpha-diaza-S-indacene)-labeled brefeldin A accumulated. To investigate a biological role for GBP, we established Neuro2a cells stably expressing Myc-tagged GBP. Overexpression of GBP did not affect cell growth or morphological features but attenuated the time-dependent decrease in cell viability caused by serum deprivation compared with control cells. After 48 h of serum starvation, Neuro2a cells overexpressing GBP were resistant to the cell death induced by serum withdrawal. These results suggest that GBP would have a relevant functional role in embryonic and postnatal development of the brain.

    The Journal of biological chemistry 2003;278;12;10531-7

  • Global profiling of the cell surface proteome of cancer cells uncovers an abundance of proteins with chaperone function.

    Shin BK, Wang H, Yim AM, Le Naour F, Brichory F, Jang JH, Zhao R, Puravs E, Tra J, Michael CW, Misek DE and Hanash SM

    Departments of Pediatrics and Pathology, University of Michigan, Ann Arbor, Michigan 48109-0656, USA.

    There is currently limited data available pertaining to the global characterization of the cell surface proteome. We have implemented a strategy for the comprehensive profiling and identification of surface membrane proteins. This strategy has been applied to cancer cells, including the SH-SY5Y neuroblastoma, the A549 lung adenocarcinoma, the LoVo colon adenocarcinoma, and the Sup-B15 acute lymphoblastic leukemia (B cell) cell lines and ovarian tumor cells. Surface membrane proteins of viable, intact cells were subjected to biotinylation then affinity-captured and purified on monomeric avidin columns. The biotinylated proteins were eluted from the monomeric avidin columns as intact proteins and were subsequently separated by two-dimensional PAGE, transferred to polyvinylidene difluoride membranes, and visualized by hybridization with streptavidin-horseradish peroxidase. Highly reproducible, but distinct, two-dimensional patterns consisting of several hundred biotinylated proteins were obtained for the different cell populations analyzed. Identification of a subset of biotinylated proteins among the different cell populations analyzed using matrix-assisted laser desorption ionization and tandem mass spectrometry uncovered proteins with a restricted expression pattern in some cell line(s), such as CD87 and the activin receptor type IIB. We also identified more widely expressed proteins, such as CD98, and a sushi repeat-containing protein, a member of the selectin family. Remarkably, a set of proteins identified as chaperone proteins were found to be highly abundant on the cell surface, including GRP78, GRP75, HSP70, HSP60, HSP54, HSP27, and protein disulfide isomerase. Comprehensive profiling of the cell surface proteome provides an effective approach for the identification of commonly occurring proteins as well as proteins with restricted expression patterns in this compartment.

    The Journal of biological chemistry 2003;278;9;7607-16

  • Nascent lipidated apolipoprotein B is transported to the Golgi as an incompletely folded intermediate as probed by its association with network of endoplasmic reticulum molecular chaperones, GRP94, ERp72, BiP, calreticulin, and cyclophilin B.

    Zhang J and Herscovitz H

    Department of Physiology and Biophysics, Center for Advanced Biomedical Research, Boston University School of Medicine, Boston, Massachusetts 02118, USA.

    We have previously demonstrated that endoplasmic reticulum (ER)-resident molecular chaperones interact with apolipoprotein B-100 (apoB) during its maturation. The initial stages of apoB folding occur while it is bound to the ER membrane, where it becomes partially lipidated to form a primordial intermediate. We determined whether this intermediate is dependent on the assistance of molecular chaperones for its subsequent folding steps. To that end, microsomes were prepared from HepG2 cells and luminal contents were subjected to KBr density gradient centrifugation. Immunoprecipitation of apoB followed by Western blotting showed that the luminal pool floated at a density of 1.12 g/ml and, like the membrane-bound pool, was associated with GRP94, ERp72, BiP, calreticulin, and cyclophilin B. Except for calreticulin, chaperone/apoB ratio in the lumen was severalfold higher than that in the membrane, suggesting a role for these chaperones both in facilitating the release of the primordial intermediate into the ER lumen and in providing stability. Subcellular fractionation on sucrose gradients showed that apoB in the Golgi was associated with the same array of chaperones as the pool of apoB recovered from heavy microsomes containing the ER, except that chaperone/apoB ratio was lower. KBr density gradient fractionation showed that the major pool of luminal apoB in the Golgi was recovered from 1.02 < d < 1.08 g/ml, whereas apoB in ER was recovered primarily from 1.08 < d < 1.2 g/ml. Both fractions were associated with the same spectrum of chaperones. Together with the finding that GRP94 was found associated with sialylated apoB, we conclude that correct folding of apoB is dependent on the assistance of molecular chaperone, which play multiple roles in its maturation throughout the secretory pathway including distal compartments such as the trans-Golgi network.

    Funded by: NHLBI NIH HHS: HL-26335, HL-58833

    The Journal of biological chemistry 2003;278;9;7459-68

  • Molecular chaperone GRP78/BiP interacts with the large surface protein of hepatitis B virus in vitro and in vivo.

    Cho DY, Yang GH, Ryu CJ and Hong HJ

    Antibody Engineering Research Unit, Laboratory of Immunology, Korea Research Institute of Bioscience and Biotechnology, Yusong, Taejon 305-600, Korea.

    The proper folding and assembly of viral envelope proteins are mediated by host chaperones. In this study, we demonstrated that an endoplasmic reticulum luminal chaperone GRP78/BiP bound specifically to the pre-S1 domain of the L protein in vitro and in vivo where complete viral particles were secreted, suggesting that GRP78/BiP plays an essential role in the proper folding of the L protein and/or assembly of viral envelope proteins.

    Journal of virology 2003;77;4;2784-8

  • ERdj5, an endoplasmic reticulum (ER)-resident protein containing DnaJ and thioredoxin domains, is expressed in secretory cells or following ER stress.

    Cunnea PM, Miranda-Vizuete A, Bertoli G, Simmen T, Damdimopoulos AE, Hermann S, Leinonen S, Huikko MP, Gustafsson JA, Sitia R and Spyrou G

    Centre for Biotechnology, Department of Biosciences at Novum, Karolinska Institute, Södertörns Högskola, S-14157 Huddinge, Sweden.

    A complex array of chaperones and enzymes reside in the endoplasmic reticulum (ER) to assist the folding and assembly of and the disulfide bond formation in nascent secretory proteins. Here we characterize a novel human putative ER co-chaperone (ERdj5) containing domains resembling DnaJ, protein-disulfide isomerase, and thioredoxin domains. Homologs of ERdj5 have been found in Caenorhabditis elegans and Mus musculus. In vitro experiments demonstrated that ERdj5 interacts via its DnaJ domain with BiP in an ATP-dependent manner. ERdj5 is a ubiquitous protein localized in the ER and is particularly abundant in secretory cells. Its transcription is induced during ER stress, suggesting potential roles for ERdj5 in protein folding and translocation across the ER membrane.

    Funded by: Telethon: GP0117Y01

    The Journal of biological chemistry 2003;278;2;1059-66

  • Proteomic analysis of early melanosomes: identification of novel melanosomal proteins.

    Basrur V, Yang F, Kushimoto T, Higashimoto Y, Yasumoto K, Valencia J, Muller J, Vieira WD, Watabe H, Shabanowitz J, Hearing VJ, Hunt DF and Appella E

    Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

    Melanin is a heterogeneous biopolymer produced only by specific cells termed melanocytes, which synthesize and deposit the pigment in specialized membrane-bound organelles known as melanosomes. Although melanosomes have been suspected of being closely related to lysosomes and platelets, the total number of melanosomal proteins is still unknown. Thus far, six melanosome-specific proteins have been identified, and the challenge is to characterize the complete proteome of the melanosome to further understand its mechanism of biogenesis. In this report, we used mass spectrometry and subcellular fractionation to identify protein components of early melanosomes. Using this approach, we have identified all 6 of the known melanosome-specific proteins, 56 proteins that are shared with other organelles, and confirmed the presence of 6 novel melanosomal proteins using western blotting and by immunohistochemistry.

    Funded by: NIGMS NIH HHS: GM 37537

    Journal of proteome research 2003;2;1;69-79

  • A subset of chaperones and folding enzymes form multiprotein complexes in endoplasmic reticulum to bind nascent proteins.

    Meunier L, Usherwood YK, Chung KT and Hendershot LM

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

    We demonstrate the existence of a large endoplasmic reticulum (ER)-localized multiprotein complex that is comprised of the molecular chaperones BiP; GRP94; CaBP1; protein disulfide isomerase (PDI); ERdj3, a recently identified ER Hsp40 cochaperone; cyclophilin B; ERp72; GRP170; UDP-glucosyltransferase; and SDF2-L1. This complex is associated with unassembled, incompletely folded immunoglobulin heavy chains. Except for ERdj3, and to a lesser extent PDI, this complex also forms in the absence of nascent protein synthesis and is found in a variety of cell types. Cross-linking studies reveal that the majority of these chaperones are included in the complex. Our data suggest that this subset of ER chaperones forms an ER network that can bind to unfolded protein substrates instead of existing as free pools that assembled onto substrate proteins. It is noticeable that most of the components of the calnexin/calreticulin system, which include some of the most abundant chaperones inside the ER, are either not detected in this complex or only very poorly represented. This study demonstrates an organization of ER chaperones and folding enzymes that has not been previously appreciated and suggests a spatial separation of the two chaperone systems that may account for the temporal interactions observed in other studies.

    Funded by: NCI NIH HHS: CA-21765, P30 CA021765; NIGMS NIH HHS: GM-54068, R01 GM054068

    Molecular biology of the cell 2002;13;12;4456-69

  • The role of Grp 78 in alpha 2-macroglobulin-induced signal transduction. Evidence from RNA interference that the low density lipoprotein receptor-related protein is associated with, but not necessary for, GRP 78-mediated signal transduction.

    Misra UK, Gonzalez-Gronow M, Gawdi G, Hart JP, Johnson CE and Pizzo SV

    Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.

    The low density lipoprotein receptor-related protein (LRP) is a scavenger receptor that binds to many proteins, some of which trigger signal transduction. Receptor-recognized forms of alpha(2)-Macroglobulin (alpha(2)M*) bind to LRP, but the pattern of signal transduction differs significantly from that observed with other LRP ligands. For example, neither Ni(2+) nor the receptor-associated protein, which blocks binding of all known ligands to LRP, block alpha(2)M*-induced signal transduction. In the current study, we employed alpha(2)-macroglobulin (alpha(2)M)-agarose column chromatography to purify cell surface membrane binding proteins from 1-LN human prostate cancer cells and murine macrophages. The predominant binding protein purified from 1-LN prostate cancer cells was Grp 78 with small amounts of LRP, a fact that is consistent with our previous observations that there is little LRP present on the surface of these cells. The ratio of LRP:Grp 78 is much higher in macrophages. Flow cytometry was employed to demonstrate the presence of Grp 78 on the cell surface of 1-LN cells. Purified Grp 78 binds to alpha(2)M* with high affinity (K(d) approximately 150 pm). A monoclonal antibody directed against Grp 78 both abolished alpha(2)M*-induced signal transduction and co-precipitated LRP. Ligand blotting with alpha(2)M* showed binding to both Grp 78 and LRP heavy chains in these preparations. Use of RNA interference to silence LRP expression had no effect on alpha(2)M*-mediated signaling. We conclude that Grp 78 is essential for alpha(2)M*-induced signal transduction and that a "co-receptor" relationship exists with LRP like that seen with several other ligands and receptors such as the uPA/uPAR (urinary type plasminogen activator or urokinase/uPA receptor) system.

    The Journal of biological chemistry 2002;277;44;42082-7

  • Possible involvement of ER chaperone Grp78 on reduced formation of amyloid-beta deposits.

    Kakimura J, Kitamura Y, Takata K, Tsuchiya D, Taniguchi T, Gebicke-Haerter PJ, Smith MA, Perry G and Shimohama S

    Department of Neurobiology, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan.

    Annals of the New York Academy of Sciences 2002;977;327-32

  • Association of the thyrotropin receptor with calnexin, calreticulin and BiP. Efects on the maturation of the receptor.

    Siffroi-Fernandez S, Giraud A, Lanet J and Franc JL

    U555 INSERM, Faculté de Médecine, Université de la Méditerranée, Marseille, France.

    The thyrotropin receptor (TSHR) is a member of the G protein-coupled receptor superfamily. It has by now been clearly established that the maturation of the glycoproteins synthesized in the endoplasmic reticulum involves interactions with molecular chaperones, which promote the folding and assembly of the glycoproteins. In this study, we investigated whether calnexin (CNX), calreticulin (CRT) and BiP, three of the main molecular chaperones present in the endoplasmic reticulum, interact with the TSHR and what effects these interactions might have on the folding of the receptor. In the first set of experiments, we observed that in a K562 cell line expressing TSHR, about 50% of the receptor synthesized was degraded by the proteasome after ubiquitination. In order to determine whether TSHR interact with CNX, CRT and BiP, coimmunoprecipitation experiments were performed. TSHR was found to be associated with all three molecular chaperones. To study the role of the interactions between CNX and CRT and the TSHR, we used castanospermine, a glucosidase I and II inhibitor that blocks the interactions between 3e these chaperones and glycoproteins. In K562 cells expressing 1efa the TSHR, these drugs led to a faster degradation of the receptor, which indicates that these interactions contribute to stabilizing the receptor after its synthesis. The overexpression of calnexin and calreticulin in these cells stabilizes the receptor during the first hour after its synthesis, whereas the degradation of TSHR increased in a cell line overexpressing BiP and the quantity of TSHR able to acquire complex type oligosaccharides decreased. These results show that calnexin, calreticulin and BiP all interact with TSHR and that the choice made between these two chaperone systems is crucial because each of them has distinct effects on the folding and stability of this receptor at the endoplasmic reticulum level.

    European journal of biochemistry 2002;269;20;4930-7

  • Requirement of the p38 mitogen-activated protein kinase signalling pathway for the induction of the 78 kDa glucose-regulated protein/immunoglobulin heavy-chain binding protein by azetidine stress: activating transcription factor 6 as a target for stress-induced phosphorylation.

    Luo S and Lee AS

    Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, Keck School of Medicine of the University of Southern California, Los Angeles 90089-9176, USA.

    Malfolded protein formation and perturbance of calcium homoeostasis results in the induction of the endoplasmic reticulum (ER) chaperone protein, namely the 78 kDa glucose-regulated protein (GRP78)/immunoglobulin heavy-chain binding protein. Various ER stress inducers can activate grp78, but signal transduction mechanisms are not well understood. We report in the present study that the induction of endogenous grp78 mRNA by the amino acid analogue azetidine (AzC) requires the integrity of a signal transduction pathway mediated by p38 mitogen-activated protein kinase (p38 MAPK). In contrast, induction of grp78 by thapsigargin that depletes the ER calcium storage can occur even when the p38 MAPK pathway is blocked. Treatment of cells with AzC results in the sustained activation of p38 MAPK. We identified an ER transmembrane activating transcription factor 6 (ATF6) as a target of p38 MAPK phosphorylation in AzC-treated cells. ATF6 undergoes proteolytic cleavage on AzC treatment, releasing a nuclear form that is an activator of the grp78 promoter. We show here that constitutively active mitogen-activated protein kinase kinase 6, a selective p38 MAPK activator, enhances the ability of the nuclear form of ATF6 to transactivate the grp78 promoter. Our results provide direct evidence that different ER stress inducers use diverse pathways to activate grp78 and that in addition to activation by proteolytic cleavage, ATF6 undergoes specific ER stress-induced phosphorylation. We propose that phosphorylation of ATF6 is a novel mechanism for augmenting its potential as a transcription activator.

    Funded by: NCI NIH HHS: CA27607

    The Biochemical journal 2002;366;Pt 3;787-95

  • Assembly and cell surface expression of homomeric and heteromeric 5-HT3 receptors: the role of oligomerization and chaperone proteins.

    Boyd GW, Low P, Dunlop JI, Robertson LA, Vardy A, Lambert JJ, Peters JA and Connolly CN

    Department of Pharmacology and Neuroscience, Ninewells Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom.

    The ability of differing subunit combinations of 5-HT3 receptors to form functional cell surface receptors was analyzed by a variety of approaches. The results revealed that 5-HT3 receptor assembly occurred within the endoplasmic reticulum (ER) and involved the interaction with chaperone proteins. The 5-HT3A subunit could assemble into functional homomeric receptors that were expressed on the cell surface. In contrast, the 5-HT3B subunit did not exhibit 5-hydroxytryptamine binding or function, could not assemble, and was efficiently retained and degraded within the ER. However, upon the coexpression of the 5-HT3A subunit, 5-HT3B could be "rescued" from the ER and transported to the cell surface to form functional heteromeric receptors with distinct functional characteristics. In support of the existence of homomeric 5-HT3 receptors in vivo, recombinantly expressed 5-HT3A receptors were capable of clustered cell surface expression in cortical neurons.

    Molecular and cellular neurosciences 2002;21;1;38-50

  • Hepatitis C virus subgenomic replicons induce endoplasmic reticulum stress activating an intracellular signaling pathway.

    Tardif KD, Mori K and Siddiqui A

    Department of Microbiology and Program in Molecular Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.

    Hepatitis C virus (HCV) replicates from a ribonucleoprotein (RNP) complex that is associated with the endoplasmic reticulum (ER) membrane. The replication activities of the HCV subgenomic replicon are shown here to induce ER stress. In response to this stress, cells expressing HCV replicons induce the unfolded protein response (UPR), an ER-to-nucleus intracellular signaling pathway. The UPR is initiated by the proteolytic cleavage of a transmembrane protein, ATF6. The resulting cytoplasmic protein fragment of ATF6 functions as a transcription factor in the nucleus and activates selective genes required for an ER stress response. ATF6 activation leads to increased transcriptional levels of GRP78, an ER luminal chaperone protein. However, the overall level of GRP78 protein is decreased. While ER stress is also known to affect translational attenuation, cells expressing HCV replicons have lower levels of phosphorylation of the alpha subunit of eukaryotic initiation factor 2. Interestingly, cap-independent internal ribosome entry site-mediated translation directed by the 5' noncoding region of HCV and GRP78 is activated in cells expressing HCV replicons. These studies provide insight into the effects of HCV replication on intracellular events and the mechanisms underlying liver pathogenesis.

    Funded by: NIDDK NIH HHS: T3-DK07038, T32 DK007038

    Journal of virology 2002;76;15;7453-9

  • The 78 kDa glucose-regulated protein (GRP78/BIP) is expressed on the cell membrane, is released into cell culture medium and is also present in human peripheral circulation.

    Delpino A and Castelli M

    Regina Elena Cancer Institute, Center for Experimental Research, Via delle Messi d'Ora 156 00158 Roma, Italy. castelli@ifo.it

    In human rabdomiosarcoma cells (TE671/RD) chronic exposure to 500 nM thapsigargin (a powerful inhibitor of the endoplasmic reticulum Ca2+-ATPases) resulted in the induction of the stress protein GRP78/BIP. Making use of the surface biotinylation method, followed by the isolation of the GRP78 using ATP-agarose affinity chromatography, it was found that a fraction of the thapsigargin-induced GRP78 is expressed on the cell surface. The presence of GRP78 on the membrane of thapsigargin-treated cells was confirmed by fractionation of cell lysates into a soluble and a membrane fraction, followed by Western blot analysis with an anti-GRP78 antibody. It was also found that conspicuous amounts of GRP78 are present in the culture medium collected from thapsigargin-treated cultures. This extracellular GRP78 originates mostly by an active release from intact cells and does not result solely from the leakage of proteins from dead cells. Moreover, small amounts of circulating, free GRP78 and naturally-occurring anti-GRP78 autoantibodies were detected in the peripheral circulation of healthy human individuals.

    Bioscience reports 2002;22;3-4;407-20

  • Dimerization and release of molecular chaperone inhibition facilitate activation of eukaryotic initiation factor-2 kinase in response to endoplasmic reticulum stress.

    Ma K, Vattem KM and Wek RC

    Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.

    Phosphorylation of eukaryotic initiation factor-2 (eIF2) by pancreatic eIF2 kinase (PEK), induces a program of translational expression in response to accumulation of malfolded protein in the endoplasmic reticulum (ER). This study addresses the mechanisms activating PEK, also designated PERK or EIF2AK3. We describe the characterization of two regions in the ER luminal portion of the transmembrane PEK that carry out distinct functions in the regulation of this eIF2 kinase. The first region mediates oligomerization between PEK polypeptides, and deletion of this portion of PEK blocked induction of eIF2 kinase activity. The second characterized region of PEK facilitates interaction with ER chaperones. In the absence of stress, PEK associates with ER chaperones GRP78 (BiP) and GRP94, and this binding is released in response to ER stress. ER luminal sequences flanking the transmembrane domain are required for GRP78 interaction, and deletion of this portion of PEK led to its activation even in the absence of ER stress. These results suggest that this ER chaperone serves as a repressor of PEK activity, and release of ER chaperones from PEK when misfolded proteins accumulate in the ER induces gene expression required to enhance the protein folding capacity of the ER.

    Funded by: NIGMS NIH HHS: R01GM49164, R01GM643540

    The Journal of biological chemistry 2002;277;21;18728-35

  • Specific incorporation of heat shock protein 70 family members into primate lentiviral virions.

    Gurer C, Cimarelli A and Luban J

    Departments of Microbiology and Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.

    To determine if any heat shock proteins are incorporated into human immunodeficiency virus type 1 (HIV-1) virions in a manner similar to that of the peptidyl-prolyl isomerase cyclophilin A, we probed purified virions with antibodies against heat shock proteins Hsp27, Hsp40, Hsp60, Hsp70, Hsc70, and Hsp90. Of these proteins, Hsp60, Hsp70, and Hsc70 associated with virions purified based on either particle density or size and were shown to be incorporated within the virion membrane, where they were protected from digestion by exogenous protease. Virion incorporation of Hsp70 was also observed with HIV-2 and with simian immunodeficiency viruses SIV(MAC) and SIV(AGM), but it appears to be specific for primate lentiviruses, since Hsp70 was not detected in association with Moloney murine leukemia virus virions. Of the HIV-1 genes, gag was found to be sufficient for Hsp70 incorporation, though Hsp70 was roughly equimolar with pol-encoded proteins in virions.

    Funded by: NIAID NIH HHS: AI 41857, P30 AI042848, P30 AI42848, R01 AI041857

    Journal of virology 2002;76;9;4666-70

  • Coupling endoplasmic reticulum stress to the cell death program: role of the ER chaperone GRP78.

    Rao RV, Peel A, Logvinova A, del Rio G, Hermel E, Yokota T, Goldsmith PC, Ellerby LM, Ellerby HM and Bredesen DE

    Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945-1400, USA.

    Alterations in Ca(2+) homeostasis and accumulation of unfolded proteins in the endoplasmic reticulum (ER) lead to an ER stress response. Prolonged ER stress may lead to cell death. Glucose-regulated protein (GRP) 78 (Bip) is an ER lumen protein whose expression is induced during ER stress. GRP78 is involved in polypeptide translocation across the ER membrane, and also acts as an apoptotic regulator by protecting the host cell against ER stress-induced cell death, although the mechanism by which GRP78 exerts its cytoprotective effect is not understood. The present study was carried out to determine whether one of the mechanisms of cell death inhibition by GRP78 involves inhibition of caspase activation. Our studies indicate that treatment of cells with ER stress inducers causes GRP78 to redistribute from the ER lumen with subpopulations existing in the cytosol and as an ER transmembrane protein. GRP78 inhibits cytochrome c-mediated caspase activation in a cell-free system, and expression of GRP78 blocks both caspase activation and caspase-mediated cell death. GRP78 forms a complex with caspase-7 and -12 and prevents release of caspase-12 from the ER. Addition of (d)ATP dissociates this complex and may facilitate movement of caspase-12 into the cytoplasm to set in motion the cytosolic component of the ER stress-induced apoptotic cascade. These results define a novel protective role for GRP78 in preventing ER stress-induced cell death.

    Funded by: NCI NIH HHS: R01 CA 84262, R01 CA084262; NIA NIH HHS: AG 12282, R01 AG012282, T32 AG 00252, T32 AG000252; NINDS NIH HHS: NS 33376, NS 35155, R01 NS033376

    FEBS letters 2002;514;2-3;122-8

  • The prosequence of human lactase-phlorizin hydrolase modulates the folding of the mature enzyme.

    Jacob R, Peters K and Naim HY

    Department of Physiological Chemistry, School of Veterinary Medicine Hannover, Bünteweg 17, Hannover D-30559, Germany.

    The efficient transport of proteins along the secretory pathway requires that the polypeptide adopts a stably folded conformation to egress the endoplasmic reticulum (ER). The transport-competent precursor of the brush border enzyme LPH, pro-LPH, undergoes an intracellular cleavage process in the trans-Golgi network between Arg(734) and Leu(735) to yield LPH beta(initial). The role of the prodomain comprising the N-terminally located 734 amino acids of pro-LPH, LPH alpha, in the folding events of LPH beta(initial) has been analyzed by the individual expression of both forms in COS-1 cells. Following synthesis at 37 degrees C LPH beta(initial) acquires a misfolded and enzymatically inactive conformation that is degraded by trypsin. A temperature shift to 20 degrees C generates a stable, trypsin-resistant, and enzymatically active LPH beta(initial) indicating that the individual expression of LPH beta(initial) results in a temperature-sensitive conformation. This form interacts at non-permissive temperatures sequentially with the ER chaperones immunoglobulin-binding protein and calnexin resulting in an ER retention. The LPH alpha prodomain resides in the ER when individually expressed. It reveals compact structural features that are stabilized by disulfide bridges. LPH alpha and LPH beta(initial) readily interact with each other upon coexpression, and this interaction appears to trigger the formation of a trypsin-resistant, correctly folded, enzymatically active, and transport-competent LPH beta(initial) polypeptide. These data clearly demonstrate that the proregion of pro-LPH is an intramolecular chaperone that is critically essential in facilitating the folding of the intermediate form LPH beta(initial) in the context of the pro-LPH polypeptide.

    The Journal of biological chemistry 2002;277;10;8217-25

  • Directed proteomic analysis of the human nucleolus.

    Andersen JS, Lyon CE, Fox AH, Leung AK, Lam YW, Steen H, Mann M and Lamond AI

    Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark.

    Background: The nucleolus is a subnuclear organelle containing the ribosomal RNA gene clusters and ribosome biogenesis factors. Recent studies suggest it may also have roles in RNA transport, RNA modification, and cell cycle regulation. Despite over 150 years of research into nucleoli, many aspects of their structure and function remain uncharacterized.

    Results: We report a proteomic analysis of human nucleoli. Using a combination of mass spectrometry (MS) and sequence database searches, including online analysis of the draft human genome sequence, 271 proteins were identified. Over 30% of the nucleolar proteins were encoded by novel or uncharacterized genes, while the known proteins included several unexpected factors with no previously known nucleolar functions. MS analysis of nucleoli isolated from HeLa cells in which transcription had been inhibited showed that a subset of proteins was enriched. These data highlight the dynamic nature of the nucleolar proteome and show that proteins can either associate with nucleoli transiently or accumulate only under specific metabolic conditions.

    Conclusions: This extensive proteomic analysis shows that nucleoli have a surprisingly large protein complexity. The many novel factors and separate classes of proteins identified support the view that the nucleolus may perform additional functions beyond its known role in ribosome subunit biogenesis. The data also show that the protein composition of nucleoli is not static and can alter significantly in response to the metabolic state of the cell.

    Current biology : CB 2002;12;1;1-11

  • GRP78, a coreceptor for coxsackievirus A9, interacts with major histocompatibility complex class I molecules which mediate virus internalization.

    Triantafilou K, Fradelizi D, Wilson K and Triantafilou M

    School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, United Kingdom.

    It is becoming apparent that over the years cell infection by virus seems to have evolved into a multistep process in which many viruses employ distinct cell surface molecules for their attachment and cell entry. In this study the attachment and entry pathway of coxsackievirus A9 (CAV-9), a member of the Picornaviridae family, was investigated. It has been known that, although integrin alpha(v)beta3 is utilized as a receptor, its presence alone is insufficient for CAV-9 infection and that CAV-9 also requires a 70-kDa major histocompatibility complex class I (MHC-I)-associated protein (MAP-70) as a coreceptor molecule. We document by protein isolation and peptide sequencing that the 70-kDa protein is GRP78, a member of the heat shock protein 70 family of stress proteins. Furthermore we show by using fluorescence resonance energy transfer (FRET) that GRP78 is also expressed on the cell surface and associates with MHC-I molecules. In addition CAV-9 infection of permissive cells requires GRP78 and also MHC-I molecules, which are essential for virus internalization. The identification of GRP78 as a coreceptor for CAV-9 and the revelation of GRP78 and MHC-I associations have provided new insights into the life cycle of CAV-9, which utilizes integrin alpha(v)beta3 and GRP78 as receptor molecules whereas MHC-I molecules serve as the internalization pathway of this virus to mammalian cells.

    Journal of virology 2002;76;2;633-43

  • Induction of glucose-regulated protein 78 by chronic hypoxia in human gastric tumor cells through a protein kinase C-epsilon/ERK/AP-1 signaling cascade.

    Song MS, Park YK, Lee JH and Park K

    Center for Molecular Medicine, Samsung Biomedical Research Institute and Molecular Therapy Research Center, Sungkyunkwan University, Seoul, 135-230 Korea.

    The M(r) 78,000 glucose-regulated protein (GRP78) can be induced by physiological stresses such as glucose deprivation and hypoxia. In solid tumors, hypoxia can promote malignant progression and confer resistance to irradiation and chemotherapy by altering gene expression. Here, we investigated the molecular mechanisms and signaling pathway involved in the late and prolonged induction of the GRP78 gene by hypoxia in a human gastric cancer cell line, MKN28. Nuclear run-on assays and mRNA stability measurements revealed that transcriptional activation, not stabilization of mRNA, contributed to the dramatic induction of GRP78 gene under hypoxia. Induction of GRP78 by chronic hypoxia was completely abolished by pretreatmen 1f40 t with PD98059 [a specific inhibitor of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK1)] or by overexpression of a dominant-negative MEK1 mutant, demonstrating a direct involvement of ERK in the induction of transcription at the GRP78 promoter under these conditions. Furthermore, hypoxia increased the transcriptional activity of a 12-O-tetradecanoylphorbol-13-acetate response element-like motif on the GRP78 promoter and increased the abundance and DNA binding activity of AP-1 complex composed of c-Jun and c-Fos. A selective protein kinase C (PKC) inhibitor, GF109203X, inhibited the induction of GRP78 gene expression as well as the activities of both ERK and Raf-1. Among six PKC isoforms expressed in MKN28 cells, PKC-epsilon expression level and kinase activity were increased by hypoxia. Transfection of MKN28 cells with a dominant-negative PKC-epsilon blocked the induction of GRP78 through ERK by hypoxia, indicating that PKC-epsilon directly participated in GRP78 induction under hypoxia. Taken together, this study shows that a PKC-epsilon-Raf-1-MEK-ERK-AP1 signaling cascade acts on a 12-O-tetradecanoylphorbol-13-acetate response element-like element to mediate hypoxia-induced GRP78 expression in human gastric cancer cells. We also confirmed in vivo the overexpression of GRP78 in surgical specimens of human primary gastric tumors.

    Cancer research 2001;61;22;8322-30

  • Major histocompatibility class one molecule associates with glucose regulated protein (GRP) 78 on the cell surface.

    Triantafilou M, Fradelizi D and Triantafilou K

    Department of Biological Sciences, University of Essex, Colchester, UK. mtrian@hotmail.com

    Glucose regulated protein 78 (GRP78) is a member of the heat shock protein (hsp) 70 family. It is an endoplasmic reticulum (ER) chaperone, whose function is generally thought to be limited to the structural maturation of nascent glycoproteins. However, recent observations have shown that ER chaperones, such as GRP78, display peptide-binding activity. These peptide-binding activities along with the observation that heat shock proteins associated with peptides can elicit antigen-specific CTL responses suggest additional roles for these proteins. In this study we provide evidence that GRP78 is not only resident in the ER, but also exists on the cell surface. Furthermore, using biochemical and imaging studies we have found that GRP78 associates with MHC class I on the cell surface. Its presence on the cell surface is not dependent on MHC class I expression. In the absence of MHC class I its cell surface expression is upregulated.

    Human immunology 2001;62;8;764-70

  • Role of extracellular molecular chaperones in the folding of oxidized proteins. Refolding of colloidal thyroglobulin by protein disulfide isomerase and immunoglobulin heavy chain-binding protein.

    Delom F, Mallet B, Carayon P and Lejeune PJ

    Unité 555 INSERM and Laboratoire de Biochimie Endocrinienne et Métabolique, Faculté de Médecine, Université de la Méditerranée, 13385 Marseille Cedex 5, France.

    The process of thyroid hormone synthesis, which occurs in the lumen of the thyroid follicles, results from an oxidative reaction leading, as side effects, to the multimerization of thyroglobulin (TG), the prothyroid hormone. Although hormone synthesis is a continuous process, the amount of Tg multimers is relatively constant. Here, we investigated the role of two molecular chaperones, protein disulfide isomerase (PDI) and immunoglobulin heavy chain-binding protein (BiP), present in the follicular lumen, on the multimerization process due to oxidation using both native Tg and its N-terminal domain (NTD). In vitro, PDI decreased multimerization of Tg and even suppressed the formation of NTD multimers. Under the same conditions, BiP was able to bind to Tg and NTD multimers but did not affect the process of multimerization. Associating BiP with PDI did not enhance the ability of PDI to limit the formation of multimers produced by oxidation. However, when BiP and PDI were reacted together with the multimeric forms and for a longer time (48 h), BiP greatly increased the efficiency of PDI. Accordingly, these two molecular chaperones probably act sequentially on the reduction of the intermolecular disulfide bridges. In the thyroid, a similar process may also be effective and participate in limiting the amount of Tg multimers present in the colloid. These results suggest that extracellular molecular chaperones play a similar role to that occurring in the endoplasmic reticulum and, furthermore, take part in the control of multimerization and aggregation of proteins formed by oxidation.

    The Journal of biological chemistry 2001;276;24;21337-42

  • WFS1 (Wolfram syndrome 1) gene product: predominant subcellular localization to endoplasmic reticulum in cultured cells and neuronal expression in rat brain.

    Takeda K, Inoue H, Tanizawa Y, Matsuzaki Y, Oba J, Watanabe Y, Shinoda K and Oka Y

    Third Department of Internal Medicine, Yamaguchi University School of Medicine, Ube, Yamaguchi 755-8505, Japan.

    Wolfram (DIDMOAD) syndrome is an autosomal recessive neurodegenerative disorder accompanied by insulin-dependent diabetes mellitus and progressive optic atrophy. Recent positional cloning led to identification of the WFS1 (Wolfram syndrome 1) gene, a member of a novel gene family of unknown function. In this study, we generated a specific antibody against the C-terminus of the WFS1 protein and investigated its subcellular localization in cultured cells. We also studied its distribution in the rat brain. Biochemical studies indicated the WFS1 protein to be an integral, endoglycosidase H-sensitive membrane glycoprote 31 in that localizes primarily in the endoplasmic re b1f ticulum (ER). Consistent with this, immunofluorescence cell staining of overexpressed WFS1 showed a characteristic reticular pattern over the cytoplasm and overlapped with the ER marker staining. No co-localization of WFS1 with mitochondria argues against an earlier clinical hypothesis that Wolfram syndrome is a mitochondria-mediated disorder. In the rat brain, at both the protein and mRNA level, WFS1 was found to be present predominantly in selected neurons in the hippocampus CA1, amygdaloid areas, olfactory tubercle and superficial layer of the allocortex. These expression sites, i.e. components of the limbic system or structures closely associated with this system, may be involved in the psychiatric, behavioral and emotional abnormalities characteristic of this syndrome. ER localization of WFS1 suggests that this protein plays an as yet undefined role in membrane trafficking, protein processing and/or regulation of ER calcium homeostasis. These studies represent a first step toward the characterization of WFS1 protein, which presumably functions to maintain certain populations of neuronal and endocrine cells.

    Human molecular genetics 2001;10;5;477-84

  • The human endoplasmic reticulum molecular chaperone BiP is an autoantigen for rheumatoid arthritis and prevents the induction of experimental arthritis.

    Corrigall VM, Bodman-Smith MD, Fife MS, Canas B, Myers LK, Wooley P, Soh C, Staines NA, Pappin DJ, Berlo SE, van Eden W, van Der Zee R, Lanchbury JS and Panayi GS

    Department of Rheumatology, Guy's, King's and St. Thomas School of Medicine, King's College London, Guy's Hospital, London, United Kingdom.

    Rheumatoid arthritis (RA) is the most common, crippling human autoimmune disease. Using Western blotting and tandem mass spectroscopy, we have identified the endoplasmic reticulum chaperone BiP, a 78-kDa glucose-regulated protein, as a possible autoantigen. It preferentially stimulated increased proliferation of synovial T cells from patients with RA but not from patients with other arthritides. Mice with established collagen- or pristane-induced arthritis developed IgG Abs to BiP. Although BiP injected in CFA failed to induce arthritis in several strains of rats and mice, including HLA-DR4(+/-)- and HLA-DR1(+/+)-transgenic animals, it completely inhibited the development of arthritis when given i.v. 1 wk before the injection of type II collagen arthritis. Preimmunization with BiP suppressed the development of adjuvant arthritis in Lewis rats in a similar manner. This is the first report of a mammalian chaperone that is an autoantigen in human RA and in experimental arthritis and that can also prevent the induction of experimental arthritis. These findings may stimulate the development of new immunotherapies for the treatment of RA.

    Journal of immunology (Baltimore, Md. : 1950) 2001;166;3;1492-8

  • Molecular cloning of a novel ubiquitin-like protein, UBIN, that binds to ER targeting signal sequences.

    Matsuda M, Koide T, Yorihuzi T, Hosokawa N and Nagata K

    Department of Molecular and Cellular Biology, Kyoto University, Sakyo-ku, Kyoto, 606-8397, Japan.

    To identify proteins that interact with HSP47, an endoplasmic reticulum (ER)-resident molecular chaperone, a yeast two-hybrid screening was performed using mouse full-length HSP47 including an N-terminal signal sequence as a bait. Analysis of several positive clones led to the identification and cloning of a novel gene, ubin, encoding a ubiquitin-like protein. Unlike other ubiquitin-like proteins, UBIN was shown to interact with signal sequences of various secretory and ER-luminal proteins, including HSP47, but not interact with signal sequences of mitochondrial targeting in two-hybrid system. The possible function of UBIN will be discussed with regards to novel characteristics of binding to signal sequences for ER targeting.

    Biochemical and biophysical research communications 2001;280;2;535-40

  • Deranged expression of molecular chaperones in brains of patients with Alzheimer's disease.

    Yoo BC, Kim SH, Cairns N, Fountoulakis M and Lubec G

    Department of Pediatrics, University of Vienna, Vienna, Austria.

    Alzheimer's disease (AD) is one of the disorders caused by protein conformational changes and recent studies have shown that several chaperone proteins are involved in this process. As information of chaperone expression in AD brain is limited, we aimed to study the expressional pattern of chaperones in several brain regions, as this may be essential to understand how folding defects can lead to disease. We studied the concomitant expressional patterns of molecular chaperones in seven brain regions of adults with AD using two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-associated laser desorption ionization mass spectroscopy (MALDI-MS). We unambiguously identified and quantified nine different chaperone proteins. Six chaperone proteins, heat shock protein 60 (HSP 60), HSP 70 RY, heat shock cognate (HSC) 71, alpha crystallin B chain, glucose regulated protein (GRP) 75, and GRP 94 showed aberrant expressional patterns depending on brain region. HSP 70.1, GRP 78 and T-complex 1 (TCP-1) epsilon subunit did not show any significant expressional change. These findings are compatible with neuropathological and biochemical abnormalities in AD brain and this report presents the first approach to quantify nine different chaperones simultaneously at the protein level in individual AD brain regions providing evidence for the relevance of aberrant chaperone expression to AD neuropathology.

    Biochemical and biophysical research communications 2001;280;1;249-58

  • The measles virus (MV) glycoproteins interact with cellular chaperones in the endoplasmic reticulum and MV infection upregulates chaperone expression.

    Bolt G

    Department of Medical Microbiology and Immunology, Panum Institute, University of Copenhagen, Denmark. gb@kvl.dk

    The present study examines the coprecipitation of measles virus (MV) glycoproteins with host cell endoplasmic reticulum (ER) chaperone proteins. Both the haemagglutinin (H) and fusion (F) glycoproteins interacted with calnexin and GRP78, whereas interaction with calreticulin was only demonstrated for the H glycoprotein. The alpha-glucosidase inhibitor castanospermine reduced and delayed the association of F proteins with calnexin. We have previously shown that alpha-glucosidase activity is important for the functionality and antigenicity of the MV F glycoprotein and for release of MV particles from infected cells. Thus, interaction with calnexin appears vital for processing of nascent MV F protein into its functional conformation. In contrast to many other viral glycoproteins, a substantial proportion of the pulsed MV glycoproteins remained associated with ER chaperones for more than 2(1/2) h. Thus, the slow and incomplete migration of MV glycoproteins to the cell surface may result from their retention by ER chaperones, probably due to malfolding. MV infection upregulated the cellular expression of calreticulin and GRP78 and also increased their presence at the cell surface. The chaperone proteins are involved in a wide range of cellular processes, and their induction by MV may play a role for the pathogenesis of measles and its sequelae.

    Archives of virology 2001;146;11;2055-68

  • The chaperone protein BiP binds to a mutant prion protein and mediates its degradation by the proteasome.

    Jin T, Gu Y, Zanusso G, Sy M, Kumar A, Cohen M, Gambetti P and Singh N

    Division of Neuropathology, Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA.

    Familial prion diseases are thought to result from a change in structure of the mutant prion protein (PrP), which takes a pathogenic conformation. We have examined the role of molecular chaperones in the folding of normal and mutant PrP Q217R (PrP(217)) in transfected neuroblastoma cells. In a previous report we showed that, although most of the PrP(217) forms escape the endoplasmic reticulum quality control system and aggregate in post-Golgi compartments, a significant proportion of PrP(217) retains the C-terminal glycosylphosphatidyl inositol signal peptide (PrP32), and does not exit the endoplasmic reticulum (Singh, N., Zanusso, G., Chen, S. G., Fujioka, H., Richardson, S., Gambetti, P., and Petersen, R. B. (1997) J. Biol. Chem. 272, 28461-28470). We have now studied the folding and turnover of PrP32 to understand the mechanism by which abnormal PrP forms cause cellular toxicity in our cell culture model and in the human brain carrying the Gerstmann-Sträussler-Scheinker disease Q217R mutation. In this report, we show that PrP32 remains associated with the chaperone BiP for an abnormally prolonged period of time and is degraded by the proteasomal pathway. This study is the first demonstration that BiP is chaperoning the folding of PrP and plays a role in maintaining the quality control in the PrP maturation pathway. Our data provide new insight into the diverse pathways of mutant PrP metabolism and neurotoxicity.

    The Journal of biological chemistry 2000;275;49;38699-704

  • Binding of BiP to the processing enzyme lymphoma proprotein convertase prevents aggregation, but slows down maturation.

    Creemers JW, van de Loo JW, Plets E, Hendershot LM and Van De Ven WJ

    Laboratory for Molecular Oncology, Center for Human Genetics, University of Leuven and Flanders Interuniversity Institute for Biotechnology, Leuven, Belgium. john.creemers@med.kuleuven.ac.be

    Lymphoma proprotein convertase (LPC) is a subtilisin-like serine protease of the mammalian proprotein convertase family. It is synthesized as an inactive precursor protein, and propeptide cleavage occurs via intramolecular cleavage in the endoplasmic reticulum. In contrast to other convertases like furin and proprotein convertase-1, propeptide cleavage occurs slowly. Also, both a glycosylated and an unglycosylated precursor are detected. Here we demonstrate that the unglycosylated precursor form of LPC is localized in the cytosol due to the absence of a signal peptide. Using a reducible cross-linker, we found that glycosylated pro-LPC is associated with the molecular chaperone BiP. In addition, we show that pro-LPC is prone to aggregation and forms large complexes linked via interchain disulfide bonds. BiP is associated mainly with non-aggregated pro-LPC and pro-LPC dimers and trimers, suggesting that BiP prevents aggregation. Overexpression of wild-type BiP or a dominant-negative BiP ATPase mutant resulted in reduced processing of pro-LPC. Taken together, these results suggest that binding of BiP to pro-LPC prevents aggregation, but results in slower maturation.

    The Journal of biological chemistry 2000;275;49;38842-7

  • Grp78 is involved in retention of mutant low density lipoprotein receptor protein in the endoplasmic reticulum.

    Jørgensen MM, Jensen ON, Holst HU, Hansen JJ, Corydon TJ, Bross P, Bolund L and Gregersen N

    Research Unit for Molecular Medicine, Aarhus University Hospital, Skejby Sygehus, DK-8200 Aarhus N, Denmark. mmj@mmf.au.dk

    The low density lipoprotein (LDL) receptor is responsible for removing the majority of the LDL cholesterol from the plasma. Mutations in the LDL receptor gene cause the disease familial hypercholesterolemia (FH). Approximately 50% of the mutations in the LDL receptor gene in patients with FH lead to receptor proteins that are retained in the endoplasmic reticulum (ER). Misfolding of mutant LDL receptors is a probable cause of this ER retention, resulting in no functional LDL receptors at the cell surface. However, the specific factors and mechanisms responsible for retention of mutant LDL receptors are unknown. In the present study we show that the molecular chaperone Grp78/BiP co-immunoprecipitates with both the wild type and two different mutant (W556S and C646Y) LDL receptors in lysates obtained from human liver cells overexpressing wild type or mutant LDL receptors. A pulse-chase study shows that the interaction between the wild type LDL receptor and Grp78 is no longer detectable after 2(1/2) h, whereas it persists for more than 4 h with the mutant receptors. Furthermore, about five times more Grp78 is co-immunoprecipitated with the mutant receptors than with the wild type receptor suggesting that Grp78 is involved in retention of mutant LDL receptors in the ER. Overexpression of Grp78 causes no major alterations on the steady state level of active LDL receptors at the cell surface. However, overexpression of Grp78 decreases the processing rate of newly synthesized wild type LDL receptors. This indicates that the Grp78 interaction is a rate-limiting step in the maturation of the wild type LDL receptor and that Grp78 may be an important factor in the quality control of newly synthesized LDL receptors.

    The Journal of biological chemistry 2000;275;43;33861-8

  • Identification and structural analysis of human RBM8A and RBM8B: two highly conserved RNA-binding motif proteins that interact with OVCA1, a candidate tumor suppressor.

    Salicioni AM, Xi M, Vanderveer LA, Balsara B, Testa JR, Dunbrack RL and Godwin AK

    Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.

    The OVCA1 gene is a candidate for the breast and ovarian tumor suppressor gene at chromosome 17p13.3. To help determine the function(s) of OVCA1, we used a yeast two-hybrid screening approach to identify OVCA1-associating proteins. One such protein, which we initially referred to as BOV-1 (binder of OVCA1-1) is 173 or 174 amino acids in length and appears to be a new member of a highly conserved RNA-binding motif (RBM) protein family that is hig 1f40 hly conserved evolutionarily. Northern blot analysis revealed that BOV-1 is ubiquitously expressed and that three distinct messenger RNA species are expressed, 1-, 3.2-, and 5.8-kb transcripts. The 1-kb transcript is the most abundant and is expressed at high levels in the testis, heart, placenta, spleen, thymus, and lymphocytes. Using fluorescence in situ hybridization and the 5.8-kb complementary DNA probe, we determined that BOV-1 maps to both chromosome 5q13-q14 and chromosome 14q22-q23. Further sequence analysis determined that the gene coding the 1- and the 3.2-kb transcripts (HGMW-approved gene symbol RBM8A) maps to 14q22-q23, whereas a second highly related gene coding for the 5.8-kb transcript resides at chromosome 5q13-q14 (HGMW-approved gene symbol RBM8B). The predicted proteins encoded by RBM8A and RBM8B are identical except that RBM8B is 16 amino acids shorter at its N-terminus. Molecular modeling of the RNA-binding domain of RBM8A and RBM8B, based on homology to the sex-lethal protein of Drosophila, identifies conserved residues in the RBM8 protein family that are likely to contact RNA in a protein-RNA complex. The conservation of sequence and structure through such an evolutionarily divergent group of organisms suggests an important function for the RBM8 family of proteins.

    Funded by: NCI NIH HHS: R01 CA-70328

    Genomics 2000;69;1;54-62

  • Heat-shock protein 70 can replace viral protein R of HIV-1 during nuclear import of the viral preintegration complex.

    Agostini I, Popov S, Li J, Dubrovsky L, Hao T and Bukrinsky M

    The Picower Institute for Medical Research, Manhasset, New York 11030, USA.

    Heat-shock proteins (Hsp's) are a family of molecular chaperones that contribute to protection from environmental stress. In this report, we demonstrate that a member of this family, Hsp70, facilitates nuclear import of HIV-1 preintegration complexes (PICs). The mechanism of this activity appears to be similar to the one used by Vpr, an HIV-1 protein regulating viral nuclear import and replication in macrophages. Indeed Hsp70 stimulated binding of HIV-1 matrix antigen to GST-karyopherin alpha fusion protein and rescued nuclear import of a Vpr-defective HIV-1 strain in vitro. Binding studies with truncated forms of GST-karyopherin alpha demonstrated that both Vpr and Hsp70 bind to a region in the amino-terminal part of the karyopherin alpha molecule. This region appears to be distinct from the binding sites for two other karyopherin alpha cargoes, basic-type NLS-containing proteins and transcription factor STAT-1. Vpr competed with Hsp70 for binding to karyopherin alpha. These results suggest the presence of a novel regulatory site on karyopherin alpha which is used by Hsp70 and Vpr to stimulate interaction between the HIV-1 PIC and karyopherin alpha and thus promote viral nuclear import.

    Funded by: NIAID NIH HHS: R01 AI 33776

    Experimental cell research 2000;259;2;398-403

  • A novel von Willebrand disease-causing mutation (Arg273Trp) in the von Willebrand factor propeptide that results in defective multimerization and secretion.

    Allen S, Abuzenadah AM, Hinks J, Blagg JL, Gursel T, Ingerslev J, Goodeve AC, Peake IR and Daly ME

    Division of Molecular and Genetic Medicine, Royal Hallamshire Hospital, University of Sheffield, UK. simon.allen@sheffield.ac.uk

    In this report we describe the molecular defect underlying partial and severe quantitative von Willebrand factor (VWF) deficiencies in 3 families previously diagnosed with types 1 and 3 Von Willebrand-disease. Analysis of the VWF gene in affected family members revealed a novel C to T transition at nucleotide 1067 of the VWF complemetary DNA (cDNA), predicting substitution of arginine by tryptophan at amino acid position 273 (R273W) of pre-pro-VWF. Two patients, homozygous for the R273W mutation, had a partial VWF deficiency (VWF:Ag levels of 0.06 IU/mL and 0.09 IU/mL) and lacked high-molecular weight VWF multimers in plasma. A third patient, also homozygous for the R273W mutation, had a severe VWF deficiency (VWF:Ag level of less than 0.01 IU/mL) and undetectable VWF multimers in plasma. Recombinant VWF having the R273W mutation was expressed in COS-7 cells. Pulse-chase experiments showed that secretion of rVWFR273W was severely impaired compared with wild-type rVWF. However, the mutation did not affect the ability of VWF to form dimers in the endoplasmic reticulum (ER). Multimer analysis showed that rVWFR273W failed to form high-molecular-weight multimers present in wild-type rVWF. We concluded that the R273W mutation is responsible for the quantitative VWF deficiencies and aberrant multimer patterns observed in the affected family members. To identify factors that may function in the intracellular retention of rVWFR273W, we investigated the interactions of VWF expressed in COS-7 cells with molecular chaperones of the ER. The R273W mutation did not affect the ability of VWF to bind to BiP, Grp94, ERp72, calnexin, and calreticulin in COS-7 cells. (Blood. 2000;96:560-568)

    Blood 2000;96;2;560-8

  • Interaction of murine BiP/GRP78 with the DnaJ homologue MTJ1.

    Chevalier M, Rhee H, Elguindi EC and Blond SY

    Department of Medicinal Chemistry and Pharmacognosy, University of Illinois, Chicago, Illinois 60607-7173, USA.

    The activity of Hsp70 proteins is regulated by accessory proteins, among which the most studied are the members of the DnaJ-like protein family. BiP/GRP78 chaperones the translocation and maturation of secreted and membrane proteins in the endoplasmic reticulum. No DnaJ-like partner has been described so far to regulate the function of mammalian BiP/GRP78. We show here that murine BiP/GRP78 interacts with the lumenal J domain of the murine transmembrane protein MTJ1 (J-MTJ1). J-MTJ1 stimulates the ATPase activity of BiP/GRP78 at stoichiometric concentrations. The C-terminal tail of BiP/GRP78 is not required for the interaction with J-MTJ1, leaving the function of this portion of the molecule still unclear. Physical interactions between J-MTJ1 and BiP/GRP78 are stable and can be abolished by a single histidine --> glutamine substitution in the highly conserved HPD motif shared by all DnaJ-like proteins. The J-MTJ1 fragment, but not the mutant J-MTJ1:H89Q fragment, stimulates the ATPase activity of Escherichia coli DnaK, although at a higher concentration than its genuine partner DnaJ. Full-length DnaJ does not stimulate BiP over the range of concentrations investigated. These results indicate that the J domain of MTJ1 is sufficient for its interaction with BiP/GRP78 and cannot be substituted by E. coli DnaJ.

    Funded by: NIGMS NIH HHS: GM58107, R01 GM058107-02, R01 GM058107-03

    The Journal of biological chemistry 2000;275;26;19620-7

  • Stress protein GRP78 prevents apoptosis induced by calcium ionophore, ionomycin, but not by glycosylation inhibitor, tunicamycin, in human prostate cancer cells.

    Miyake H, Hara I, Arakawa S and Kamidono S

    Department of Urology, Kobe University School of Medicine, Kobe 650-0017, Japan.

    GRP78 induction has recently been shown to play a critical role in maintaining cell viability against several kinds of stress, including depletion of endoplasmic reticulum Ca(2+) and accumulation of unglycosylated proteins, under specific experimental conditions. However, the functional significance of GRP78 induction after stressful treatment has not been well defined. This article characterizes the different biological features associated with GRP78 induction by two kinds of stress agents, calcium ionophore, ionomycin (IM), and glycosylation inhibitor, tunicamycin (TM), focusing on the association with apoptosis in human prostate cancer cells. Both IM and TM treatment resulted in marked induction of GRP78 transcription in androgen-dependent prostate cancer LNCaP cells maintained in medium without androgen, but not in medium containing androgen, as measured by Northern blotting and nuclear run-off assays. After pretreatment with tumor necrosis factor-alpha, which has potent cytotoxic effects on LNCaP cells, both IM and TM could induce substantial increases in GRP78 transcription in LNCaP cells, even in medium containing androgen. Under both experimental conditions described, DNA fragmentation assays showed a direct correlation between the onset of apoptosis in LNCaP cells after IM treatment and the initiation of GRP78 transcript induction, while induction of GRP78 expression preceded TM-induced apoptosis. To elucidate the functional differences of GRP78 induction by IM and TM, an antisense oligodeoxynucleotide (ODN) targeted against the grp78 gene was designed to reduce GRP78 expression in a sequence-specific and dose-dependent manner. Antisense GRP78 ODN treatment substantially enhanced apoptosis of LNCaP cells induced by IM compared with mismatch control ODN treatment, whereas no marked differences were observed in apoptotic features induced by TM with antisense GRP78 and mismatch control ODN treatment. Studies of additional androgen-independent prostate cancer PC3 cells also demonstrated a correlation between GRP78 induction and resistance to apoptosis after IM treatment, but not after TM treatment. These findings suggest that there are at least two GRP78 signaling pathways, which play different roles in resistance against stress-induced apoptosis.

    Journal of cellular biochemistry 2000;77;3;396-408

  • Requirement for a kinase-specific chaperone pathway in the production of a Cdk9/cyclin T1 heterodimer responsible for P-TEFb-mediated tat stimulation of HIV-1 transcription.

    O'Keeffe B, Fong Y, Chen D, Zhou S and Zhou Q

    Department of Molecular Biology, University of California at Berkeley, Berkeley, California 94720-3206, USA.

    Tat activation of HIV-1 transcription is mediated by human transcription elongation factor P-TEFb, which interacts with Tat and phosphorylates the C-terminal domain of RNA polymerase II. The catalytic subunit of the P-TEFb complex, Cdk9, has been shown to interact with cyclin T and several other proteins of unknown identity. Consequently, the exact subunit composition of active P-TEFb has not been determined. Here we report the affinity purification and identification of the Cdk9-associated proteins. In addition to forming a heterodimer with cyclin T1, Cdk9 interacted with the molecular chaperone Hsp70 or a kinase-specific chaperone complex, Hsp90/Cdc37, to form two separate chaperone-Cdk9 complexes. Although the Cdk9/cyclin T1 dimer was exceptionally stable and produced slowly in the cell, free and unprotected Cdk9 appeared to be degraded rapidly. Several lines of evidence indicate the heterodimer of Cdk9/cyclin T1 to be the mature, active form of P-TEFb responsible for phosphorylation of the C-terminal domain of RNA polymerase II interaction with the Tat activation domain, and mediation of Tat activation of HIV-1 transcription. Pharmacological inactivation of Hsp90/Cdc37 function by geldanamycin revealed an essential role for the chaperone-Cdk9 complexes in generation of Cdk9/cyclin T1. Our data suggest a previously unrecognized chaperone-dependent pathway involving the sequential actions of Hsp70 and Hsp90/Cdc37 in the stabilization/folding of Cdk9 as well as the assembly of an active Cdk9/cyclin T1 complex responsible for P-TEFb-mediated Tat transactivation.

    Funded by: NIAID NIH HHS: AI-41757

    The Journal of biological chemistry 2000;275;1;279-87

  • BiP-binding sequences in HIV gp160. Implications for the binding specificity of bip.

    Knarr G, Modrow S, Todd A, Gething MJ and Buchner J

    Institut für Biophysik & Physikalische Biochemie, Universität Regensburg, 93040 Regensburg, Germany.

    BiP, a resident endoplasmic reticulum member of the HSP70 family of molecular chaperones, associates transiently with a wide variety of newly synthesized exocytotic proteins. In addition to immunoglobulin heavy and light chains, the first natural substrates identified for BiP, a number of viral polypeptides including the human immunodeficiency virus type 1 envelope glycoprotein gp160 interact with BiP during their passage through the endoplasmic reticulum. We have used a computer algorithm developed to predict BiP-binding sites within protein primary sequences to identify sites within gp160 that might mediate its association with BiP. Analysis of the ability of 22 synthetic heptapeptides corresponding to predicted binding sites to stimulate the ATPase activity of BiP or to compete with an unfolded polypeptide for binding to BiP indicated that about half of them are indeed recognized by the chaperone. All of the confirmed binding sites are localized within conserved regions of gp160, suggesting a conserved role for BiP in the folding of gp160. Information on the characteristics of confirmed BiP-binding peptides gained in this and previous studies has been utilized to improve the predictive power of the BiP Score algorithm and to investigate the differences in peptide binding specificities of HSP70 family members.

    The Journal of biological chemistry 1999;274;42;29850-7

  • Calnexin and the immunoglobulin binding protein (BiP) coimmunoprecipitate with AMPA receptors.

    Rubio ME and Wenthold RJ

    Laboratory of Neurochemistry, NIDCD, NIH, Bethesda, Maryland 20892-4162, USA.

    To identify proteins that interact with alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors, we carried out coimmunoprecipitation analyses on detergent-solubilized rat forebrain membranes. Membranes were solubilized with Triton X-100, and immunoprecipitation was done using subunit-specific antibodies to GluR1, GluR2/3, and GluR4 attached to protein Aagarose. Proteins bound to the antibodies were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by silver staining and western blotting. With solubilization in low ionic strength buffer, several coimmunoprecipitating proteins, with Mr = 17,000-100,000, were identified in silver-stained gels. Western blots were then probed with antibodies to a series of candidate proteins that were chosen based on the molecular masses of the copurifying proteins. Two of these were identified as the molecular chaperones calnexin (90 kDa) and the immunoglobulin binding protein (BiP; 78 kDa). Immunoprecipitation with antibodies to calnexin and BiP demonstrated that glycosylated AMPA receptor subunits were associated. The relationship between AMPA receptors and calnexin and BiP was further studied with immunocytochemistry of the hippocampus. Both calnexin and BiP labeling was present not only in the cell body but also in dendrites of hippocampal pyramidal neurons, where double-label immunofluorescence also showed the presence of AMPA receptor subunits.

    Journal of neurochemistry 1999;73;3;942-8

  • BiP and immunoglobulin light chain cooperate to control the folding of heavy chain and ensure the fidelity of immunoglobulin assembly.

    Lee YK, Brewer JW, Hellman R and Hendershot LM

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

    The immunoglobulin (Ig) molecule is composed of two identical heavy chains and two identical light chains (H2L2). Transport of this heteromeric complex is dependent on the correct assembly of the component parts, which is controlled, in part, by the association of incompletely assembled Ig heavy chains with the endoplasmic reticulum (ER) chaperone, BiP. Although other heavy chain-constant domains interact transiently with BiP, in the absence of light chain synthesis, BiP binds stably to the first constant domain (CH1) of the heavy chain, causing it to be retained in the ER. Using a simplified two-domain Ig heavy chain (VH-CH1), we have determined why BiP remains bound to free heavy chains and how light chains facilitate their transport. We found that in the absence of light chain expression, the CH1 domain neither folds nor forms its intradomain disulfide bond and therefore remains a substrate for BiP. In vivo, light chains are required to facilitate both the folding of the CH1 domain and the release of BiP. In contrast, the addition of ATP to isolated BiP-heavy chain complexes in vitro causes the release of BiP and allows the CH1 domain to fold in the absence of light chains. Therefore, light chains are not intrinsically essential for CH1 domain folding, but play a critical role in removing BiP from the CH1 domain, thereby allowing it to fold and Ig assembly to proceed. These data suggest that the assembly of multimeric protein complexes in the ER is not strictly dependent on the proper folding of individual subunits; rather, assembly can drive the complete folding of protein subunits.

    Funded by: NCI NIH HHS: CA-21765, P30 CA021765; NIGMS NIH HHS: F32 GM-18443, F32 GM018443, GM-54068, R01 GM054068

    Molecular biology of the cell 1999;10;7;2209-19

  • Transcriptional regulation of the human asparagine synthetase gene by carbohydrate availability.

    Barbosa-Tessmann IP, Pineda VL, Nick HS, Schuster SM and Kilberg MS

    Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Box 100245, JHMHC Gainesville, FL 32610-0245, USA.

    Transcription of the asparagine synthetase (AS) gene is induced by amino acid deprivation. The present data illustrate that this gene is also under transcriptional control by carbohydrate availability. Incubation of human HepG2 hepatoma cells in glucose-free medium resulted in an increased AS mRNA content, reaching a maximum of about 14-fold over control cells after approx. 12 h. Extracellular glucose caused the repression of the content of AS mRNA in a concentration-dependent manner, with a k1/2 (concentration causing a half-maximal repression) of 1 mM. Fructose, galactose, mannose, 2-deoxyglucose and xylitol were found to maintain the mRNA content of both AS and the glucose-regulated protein GRP78 in a state of repression, whereas 3-O-methylglucose did not. Incubation in either histidine-free or glucose-free medium also resulted in adaptive regulation of the AS gene in BNL-CL.2 mouse hepatocytes, rat C6 glioma cells and human MOLT4 lymphocytes, in addition to HepG2 cells. In contrast, the steady-state mRNA content of GRP78 was unaffected by amino acid availability. Transient transfection assays using a reporter gene construct documented that glucose deprivation increases AS gene transcription via elements within the proximal 3 kbp of the AS promoter. These results illustrate that human AS gene transcription is induced following glucose limitation of the cells.

    Funded by: NIDDK NIH HHS: DK-52064

    The Biochemical journal 1999;339 ( Pt 1);151-8

  • Involvement of oxidative reactions and extracellular protein chaperones in the rescue of misassembled thyroglobulin in the follicular lumen.

    Delom F, Lejeune PJ, Vinet L, Carayon P and Mallet B

    Unité 38 INSERM, Faculté de Médecine, Marseille, France.

    Reactive oxygen species (ROS) are involved in many pathological processes through modifications of structure and activity of proteins. ROS also participate in physiological pathways such as thyroid hormone biosynthesis, which proceeds through oxidation of the prothyroid hormone (thyroglobulin, Tg) and iodide. Regarding the colloidal insoluble multimerized Tg (m-Tg), which bears dityrosine bridges and is present in the follicular lumen, a mild oxidative system generated different soluble forms of Tg, more or less compacted by hydrophobic associations, and linked with Grp78 and Grp94. In vitro, the combined action of ROS and PDI, in the presence of free glutathione (reduced/oxidized), increased the solubility of this misassembled Tg and partially restored the ability of Tg to synthesize hormones. Our results show that protein chaperones escape from the ER and are involved with ROS in thyroid hormone synthesis. Therefore, we propose a model of roles of m-Tg in the follicular lumen.

    Biochemical and biophysical research communications 1999;255;2;438-43

  • Stathmin interaction with HSC70 family proteins.

    Manceau V, Gavet O, Curmi P and Sobel A

    INSERM U440-IFM, Paris, France.

    Stathmin is a ubiquitous cytosolic phosphoprotein participating in the relay and integration of diverse intracellular signaling pathways involved in the control of cell proliferation, differentiation, and activities. It is phosphorylated in response to diverse extracellular signals including hormones and growth factors, and it is highly expressed during development and in diverse tumoral cells and tissues. Stathmin interacts with tubulin and other potential protein partners such as BiP, KIS, CC1 and CC2/tsg101. In our present search for further functional partners of stathmin, we identified proteins in the Hsp70 family, and in particular Hsc70, as interacting with stathmin in vitro. Hsc70 is among the proteins coimmunoprecipitated with stathmin, and it is the main protein retained specifically on stathmin-Sepharose beads identified by one- and two-dimensional electrophoresis and immunoblots. Bovine serum albumin (BSA)-Sepharose did not bind Hsc70, and anti-stathmin antisera specifically inhibited the interaction of Hsc70 with stathmin-Sepharose. The binding of Hsc70 to stathmin is dependent on the phosphorylation status of stathmin, as it did not occur with a "pseudophosphorylated" mutant form of stathmin. This interaction is further dependent on the ATP status of Hsc70. It was inhibited in the presence of ATP-Mg++ but not in the presence of ATP-Mg++ and ethylenediaminetetraacetic acid (EDTA) or of ADP. Our results suggest that the interaction of stathmin with Hsc70 is specific in both proteins and most likely biologically relevant in the context of their functional implication in the control of numerous intracellular signaling and regulatory pathways, and hence of normal cell growth and differentiation.

    Electrophoresis 1999;20;2;409-17

  • The in vivo association of BiP with newly synthesized proteins is dependent on the rate and stability of folding and not simply on the presence of sequences that can bind to BiP.

    Hellman R, Vanhove M, Lejeune A, Stevens FJ and Hendershot LM

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

    Immunoglobulin heavy chain-binding protein (BiP) is a member of the hsp70 family of chaperones and one of the most abundant proteins in the ER lumen. It is known to interact transiently with many nascent proteins as they enter the ER and more stably with protein subunits produced in stoichiometric excess or with mutant proteins. However, there also exists a large number of secretory pathway proteins that do not apparently interact with BiP. To begin to understand what controls the likelihood that a nascent protein entering the ER will associate with BiP, we have examined the in vivo folding of a murine lambdaI immunoglobulin (Ig) light chain (LC). This LC is composed of two Ig domains that can fold independent of the other and that each possess multiple potential BiP-binding sequences. To detect BiP binding to the LC during folding, we used BiP ATPase mutants, which bind irreversibly to proteins, as "kinetic traps." Although both the wild-type and mutant BiP clearly associated with the unoxidized variable region domain, we were unable to detect binding of either BiP protein to the constant region domain. A combination of in vivo and in vitro folding studies revealed that the constant domain folds rapidly and stably even in the absence of an intradomain disulfide bond. Thus, the simple presence of a BiP-binding site on a nascent chain does not ensure that BiP will bind and play a role in its folding. Instead, it appears that the rate and stability of protein folding determines whether or not a particular site is recognized, with BiP preferentially binding to proteins that fold slowly or somewhat unstably.

    Funded by: NCI NIH HHS: P30 CA021765, P30 CA21765; NIGMS NIH HHS: GM-4068, R01 GM054068

    The Journal of cell biology 1999;144;1;21-30

  • A stress-inducible rat liver endoplasmic reticulum protein, ERp29.

    Mkrtchian S, Fang C, Hellman U and Ingelman-Sundberg M

    Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden. soumkr@ki.se

    We have isolated, cDNA cloned and characterised a 29-kDa protein (ERp29), containing a C-terminal endoplasmic reticulum(ER)-retrieval signal, from the rat liver ER. ERp29 was induced to high levels in the rat hepatoma cells under metabolic stress conditions known to cause an aberrant accumulation of proteins in the ER [(e.g. culture in presence of the Ca2+ ionophore A23187, inhibitors of Ca2+-ATPase (thapsigargin), intracellular protein transport (brefeldin A), or protein N-glycosylation (tunicamycin)]. Experimental evidence of its localisation in the luminal compartment of the ER was obtained by topology studies including immunofluorescence microscopy, in vitro translation and proteinase protection assay. ERp29 constitutes about 0.1% of the rat hepatic microsomal proteins and is constitutively expressed in all rat tissues examined, as evident from northern blot analysis. In rat hepatoma cells ERp29 was found to be associated with the abundant molecular chaperone/stress protein BiP/GRP78 and this interaction was significantly enhanced after treatment with tunicamycin and A23187. Taken together, these results suggest that ERp29 is a member of the stress-response machinery of the ER.

    European journal of biochemistry 1998;251;1-2;304-13

  • Association of glucose-regulated protein (grp78) with human keratin 8.

    Liao J, Price D and Omary MB

    Clontech Laboratories Inc., Palo Alto, CA 94303, USA.

    Keratin polypeptides 8 and 18 (K8/18) are intermediate filament proteins that are expressed in 'simple-type' epithelial cells. They associate with several proteins including the 70 kDa cytoplasmic heat shock proteins (hsp70). We identified the human 78 kDa glucose-regulated protein (grp78) as a keratin-associated protein. Keratin-grp78 association was noted after co-immunoprecipitation of K8/18 from HT29 detergent solubilized cell lysates, and appears to involve non-posttranslationally modified grp78. The grp78-K8/18 association is induced by culturing cells in the presence of tunicamycin or after glucose starvation. K8/18-bound grp78 can be dissociated by Mg-ATP and the association can be reconstituted in vitro using purified grp78, then redissociated again by Mg-ATP. Binding of grp78 occurs preferentially with K8, and when reconstituted does not depend on the posttranslational modification state of K8/18. Co-incubation of K8/18 with hsp70 and grp78 shows preferential association with hsp70. Our results demonstrate a direct association of grp78 with K8 under conditions that induce grp78 expression.

    Funded by: NIDDK NIH HHS: DK47918

    FEBS letters 1997;417;3;316-20

  • Mutagenesis of a potential immunoglobulin-binding protein-binding site enhances secretion of coagulation factor VIII.

    Swaroop M, Moussalli M, Pipe SW and Kaufman RJ

    Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.

    Coagulation factor VIII (FVIII) and factor V are homologous glycoproteins that have a domain structure of A1-A2-B-A3-C1-C2. FVIII is a heterodimer of the heavy chain (domains A1-A2-B) and the light chain (domains A3-C1-C2) in a metal ion-dependent association between the A1- and A3-domains. Previous studies identified a 110-amino acid region within the FVIII A1-domain that inhibits its secretion and contains multiple short peptide sequences that have potential to bind immunoglobulin-binding protein (BiP). FVIII secretion requires high levels of intracellular ATP, consistent with an ATP-dependent release from BiP. Site-directed mutagenesis was used to elucidate the importance of the potential BiP-binding sites in FVIII secretion. Mutation of Phe at position 309 to Ser or Ala enhanced the secretion of functional FVIII and reduced its ATP dependence. The F309S FVIII had a specific activity, thrombin activation profile, and heat inactivation properties similar to those of wild-type FVIII. However, F309S FVIII displayed increased sensitivity to EDTA-mediated inactivation that is known to occur through metal ion chelation-induced dissociation of the heavy and light chains of FVIII. The results support that Phe309 is important in high affinity heavy and light chain interaction, and this correlates with a high affinity BiP-binding site. Introduction of the F309S mutation into other secretion defective FVIII mutants rescued their secretion, demonstrating the ability of the this mutation to improve secretion of mutant FVIII proteins retained in the cell.

    Funded by: NHLBI NIH HHS: HL52173, HL53777

    The Journal of biological chemistry 1997;272;39;24121-4

  • A two-dimensional gel database of human colon carcinoma proteins.

    Ji H, Reid GE, Moritz RL, Eddes JS, Burgess AW and Simpson RJ

    Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research (Melbourne Branch), Parkville, Victoria, Australia.

    The master two-dimensional gel database of human colon carcinoma cells currently lists cellular proteins from normal crypts and the colorectal cancer cell lines LIM 1863, LIM 1215 and LIM 1899 (Ward et al., Electrophoresis 1990, 11, 883-891; Ji et al., Electrophoresis 1994, 15, 391-405). Updated two-dimensional electrophoretic (2-DE) maps of cellular proteins from LIM 1215 cells, acquired under both nonreducing and reducing conditions, are presented. Fifteen cellular proteins are identified in the reducing 2-DE gel map, and seven in the nonreducing gel map, along with a tabular listing of their M(r)/pI loci and mode of identification. We also include our mass spectrometric based procedures for identifying 2-DE resolved proteins. This procedure relies on a combination of capillary column (0.10-0.32 mm internal diameter) reversed-phase HPLC peptide mapping of in-gel digested proteins, peptide mass fingerprinting, sequence analysis by either collision-induced dissociation or post-source-decay fragmentation, and protein identification using available database search algorithms. These data, and descriptions of the micro-techniques employed in this laboratory for identifying 2-DE resolved proteins can be accessed via the internet URL: http:(/)/www.ludwig.edu.au.

    Electrophoresis 1997;18;3-4;605-13

  • Two-dimensional electrophoretic analysis of human breast carcinoma proteins: mapping of proteins that bind to the SH3 domain of mixed lineage kinase MLK2.

    Rasmussen RK, Ji H, Eddes JS, Moritz RL, Reid GE, Simpson RJ and Dorow DS

    Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research, Parkville, Victoria, Australia.

    MLK2, a member of the mixed lineage kinase (MLK) family of protein kinases, first reported by Dorow et al. (Eur. J. Biochem. 1993, 213, 701-710), comprises several distinct structural domains including an src homology-3 (SH3) domain, a kinase catalytic domain, a unique domain containing two leucine zipper motifs, a polybasic sequence, and a cdc42/rac interactive binding motif. Each of these domains has been shown in other systems to be associated with a specific type of protein interaction in the regulation of cellular signal transduction. To study the role of MLK2 in recruiting specific substrates, we constructed a recombinant cDNA encoding the N-terminal 100 amino acids of MLK2 (MLK2N), including the SH3 domain (residues 23-77), fused to glutathione S-transferase. This fusion protein was expressed in Escherichia coli, purified using gluthathione-Sepharose affinity chromatography and employed in an affinity approach to isolate MLK2-SH3 domain binding proteins from lysates of 35S-labelled MDA-MB231 human breast tumour cells. Electrophoretic analysis of bound proteins revealed that two low-abundance proteins with a molecular weights (Mr) of approximately 31,500 and approximately 34,000, bound consistently to the MLK2N protein. To establish accurately the Mt / isoelectric point (pI) loci of these MLK2-SH3 domain binding proteins, a number of abundant proteins in a two-dimensional electrophoresis (2-DE) master gel were identified to serve as triangulation marker points. Proteins were identified by (i) direct Edman degradation following electroblotting onto polyvinylidene difluoride (PVDF) membranes, (ii) Edman degradation of peptides generated by in-gel proteolysis and fractionation by rapid (approximately 12 min) microbore column (2.1 mm ID) reversed-phase high performance liquid chromatography (HPLC), (iii) mass spectrometric methods including peptide-mass fingerprinting and electrospray (ESI)-mass spectrometry (MS)-MS utilizing capillary (0.2-0.3 mm ID) column chromatography, or (iv) immunoblot analysis. Using this information, a preliminary 2-DE protein database for the human breast carcinoma cell line MDA-MB231, comprising 21 identified proteins, has been constructed and can be accessed via the World Wide Web (URL address: http:(/)/ www.ludwig.edu.au/www/jpsl/jpslhome.htm l).

    Electrophoresis 1997;18;3-4;588-98

  • Multiple molecular chaperones complex with misfolded large oligomeric glycoproteins in the endoplasmic reticulum.

    Kuznetsov G, Chen LB and Nigam SK

    Harvard Medical School, Boston, Massachusetts 02115, USA.

    Thyroglobulin (Tg), the major protein secreted by thyroid epithelial cells and precursor of thyroid hormones, is a large dimeric glycoprotein with multiple disulfide bonds. The folding and assembly of this complex molecule begins in the endoplasmic reticulum (ER) and is likely to involve a variety of reactions catalyzed by molecular chaperones (Kuznetsov, G., Chen, L. B., and Nigam, S. K. (1994) J. Biol. Chem. 269, 22990-22995). By coimmunoprecipitation in rat thyroid cells, we were able to demonstrate that BiP, grp94, ERp72, and grp170, four proteins believed to function as specific molecular chaperones, complex with Tg during its maturation. The same complex of the four putative chaperones with Tg was observed in cells treated with tunicamycin, indicating that these four ER chaperones stably associate with Tg when it is misfolded/misassembled due to inhibition of its glycosylation. BiP, grp94, and ERp72 were also found to associate with Tg in cells in which misfolding was induced by perturbing ER calcium stores. To determine if the assembly of a complex between the four chaperones and Tg under conditions of misglycosylation was unique to the maturation of this particular secretory protein or a more general phenomenon, adenovirus-transformed rat thyroid cells that do not synthesize Tg were analyzed. In these transformed cells, the only protein these same four chaperones were found to complex with was a protein of approximately 200 kDa. This protein was subsequently identified as thrombospondin, which, like Tg, is a large oligomeric secreted glycoprotein with multiple disulfide bonds. We therefore propose that these ER chaperones complex together with a variety of large oligomeric secretory glycoproteins as they fold and assemble in the ER.

    Funded by: NIDDK NIH HHS: DK44503, R01 DK49517

    The Journal of biological chemistry 1997;272;5;3057-63

  • Stathmin interaction with a putative kinase and coiled-coil-forming protein domains.

    Maucuer A, Camonis JH and Sobel A

    Institut National de la Santé et de la Recherche Médicale, Unité 153, Paris, France.

    Stathmin is a ubiquitous, cytosolic 19-kDa protein, which is phosphorylated on up to four sites in response to many regulatory signals within cells. Its molecular characterization indicates a functional organization including an N-terminal regulatory domain that bears the phosphorylation sites, linked to a putative alpha-helical binding domain predicted to participate in coiled-coil, protein-protein interactions. We therefore proposed that stathmin may play the role of a relay integrating diverse intracellular regulatory pathways; its action on various target proteins would be a function of its combined phosphorylation state. To search for such target proteins, we used the two-hybrid screen in yeast, with stathmin as a "bait." We isolated and characterized four cDNAs encoding protein domains that interact with stathmin in vivo. One of the corresponding proteins was identified as BiP, a member of the hsp70 heat-shock protein family. Another is a previously unidentified, putative serine/threonine kinase, KIS, which might be regulated by stathmin or, more likely, be part of the kinases controlling its phosphorylation state. Finally, two clones code for subdomains of two proteins, CC1 and CC2, predicted to form alpha-helices participating in coiled-coil interacting structures. Their isolation by interaction screening further supports our model for the regulatory function of stathmin through coiled-coil interactions with diverse downstream targets via its presumed alpha-helical binding domain. The molecular and biological characterization of KIS, CC1, and CC2 proteins will give further insights into the molecular functions and mechanisms of action of stathmin as a relay of integrated intracellular regulatory pathways.

    Proceedings of the National Academy of Sciences of the United States of America 1995;92;8;3100-4

  • Molecular chaperones involved in protein degradation in the endoplasmic reticulum: quantitative interaction of the heat shock cognate protein BiP with partially folded immunoglobulin light chains that are degraded in the endoplasmic reticulum.

    Knittler MR, Dirks S and Haas IG

    Institute for Biochemistry I, University of Heidelberg, Germany.

    In the absence of immunoglobulin heavy-chain expression, some immunoglobulin light (L) chains are retained and degraded within the cell. We investigated the fate of two different nonsecreted murine L chains which exhibit different half-lives (50 min and 3-4 hr). Our results demonstrate that both nonsecreted L chains are quantitatively bound to BiP as partially oxidized molecules. The kinetics of L-chain degradation coincided with those of L-chain dissociation from BiP, which suggests that these two processes are functionally related. L-chain degradation does not depend on vesicular transport, indicating that these soluble proteins are degraded in the endoplasmic reticulum (ER). In contrast, secreted L chains, which interact only transiently with BiP, are completely oxidized and are not degraded even when they are artificially retained in the ER. Our data support the model that, by means of BiP interaction, the ER degradation mechanism has the potential to discriminate between partially and completely folded molecules.

    Proceedings of the National Academy of Sciences of the United States of America 1995;92;5;1764-8

  • Biogenesis of MHC class I antigens: involvement of multiple chaperone molecules.

    Kahn-Perlès B, Salamero J and Jouans O

    Centre d'Immunologie de Marseille-Luminy, France.

    To analyze the early events occurring during the folding and assembly of major histocompatibility complex class I antigens, we used a panel of P815 mouse mastocytoma transfectants expressing wild-type or mutant human leukocyte antigen (HLA)-Cw3 proteins. We observed that newly synthesized unassembled HLA-Cw3 heavy chains (Cw3 alpha) specifically associate with three major long-lived proteins denoted p105, p88 and p78, according to their size. These proteins display different kinetics of interaction. The association of p105 is transient, while p78, which we identified as the immunoglobulin binding protein BiP, interacts permanently with Cw3 alpha chains. Furthermore, the binding of p88, a calnexin candidate, seems delayed compared to that of p105 and p78. As the great majority of newly synthesized Cw3 alpha proteins expressed in P815 cells can associate with cotransfected human beta 2-microglobulin (beta 2m), our observations suggest that multiple molecular chaperones cooperate in the folding of class I heavy chains. We were unable to coimmunoprecipitate detectable levels of these proteins with oligomerized Cw3 alpha chains. However, we could still detect p78/BiP in transient association with mutant HLA-Cw3 heterodimers which were delayed in the endoplasmic reticulum (ER) compared to their wild-type counterparts. In this case, the dissociation of BiP preceded the ER to Golgi transport of these proteins. These results suggest that BiP release is neither related to the process of class I oligomerization nor to the ER retention of class I assembly intermediates.

    European journal of cell biology 1994;64;1;176-85

  • Localization of the gene encoding human BiP/GRP78, the endoplasmic reticulum cognate of the HSP70 family, to chromosome 9q34.

    Hendershot LM, Valentine VA, Lee AS, Morris SW and Shapiro DN

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.

    BiP/GRP78 is a member of the HSP70 family involved in the folding and assembly of proteins in the endoplasmic reticulum. Using PCR amplification of DNA from human x rodent somatic hybrids that segregate human chromosomes in conjunction with fluorescence in situ hybridization, we have assigned GRP78 to chromosome 9q34. This is in agreement with the localization of murine and bovine homologues based on the high degree of synteny in this region. Several interesting genes and disorders map to this region and are discussed.

    Funded by: NCI NIH HHS: CA23099, CA27607; NIGMS NIH HHS: GM43576; ...

    Genomics 1994;20;2;281-4

  • Human immunodeficiency virus type 1 interaction with the membrane of CD4+ cells induces the synthesis and nuclear translocation of 70K heat shock protein.

    Furlini G, Vignoli M, Re MC, Gibellini D, Ramazzotti E, Zauli G and La Placa M

    Institute of Microbiology, University of Bologna, St Orsola General Hospital, Italy.

    In the last few years a growing body of experimental evidence has indicated that the interaction of human immunodeficiency virus type 1 (HIV-1) surface glycoprotein (gp120) with the membrane of CD4+ cells may deliver negative signals, eventually leading to programmed cell death (apoptosis) of either mature CD4+ lymphocytes or CD34+ haematopoietic progenitor cells, in the absence of cell infection with HIV-1. However, information on the possible activation of the classical signal transduction pathway through gp120 engagement of cell surface CD4 is contradictory. Heat shock proteins (hsp) or 'stress' proteins' are involved in protecting cells from the deleterious effects of heat and other stresses and perform various cell roles. In mammalian cells there is evidence that hsp70 is involved in the transport of proteins to lysosomes, mitochondria and the nucleus. The results obtained in our study demonstrate that early (3 h) after the exposure of permissive CD4+ cells to HIV-1 (or to purified recombinant gp120) a peak of increased synthesis and nuclear translocation of a 70K hsp (and possibly other proteins) is observed. These data indicate that gp120 possesses the capacity to trigger a cascade of events through a transmembrane signalling activity.

    The Journal of general virology 1994;75 ( Pt 1);193-9

  • A direct-repeat sequence of the human BiP gene is required for A23187-mediated inducibility and an inducible nuclear factor binding.

    Chao CC and Lin-Chao S

    Department of Biochemistry, Chang Gung Medical College, Taoyuan, Taiwan, China.

    We have recently isolated a functional promoter encoding the human polypeptide-binding protein (BiP) gene from Burkitt's lymphoma cells by polymerase chain reaction (The EMBL Data Library accession number X59969, 1991). This promoter DNA segment (termed BiP670) was fused to the bacterial chloramphenicol acetyltransferase (CAT) reporter gene and expressed in NIH3T3 cells. BiP670 retains basal and Ca2+ ionophore A23187-inducible activities. Using 5' deletion assay, we found three basal expression elements (BEE) in the BiP670. Removal of the distal BBE (BBE3), which is contained in a segment spanning -368/-170, caused a 50% loss of the basal activity; removal together with the middle BBE (BBE2), which is contained in a segment spanning -170/-107, resulted in a further 30% loss of the activity. Further removal of the proximal BBE (BBE1), which spans -107/-39, abolished greater than 95% of the basal expression. In addition, an A23187-inducible element (AIE) appeared to be associated with the BBE1. At least a six-fold inducibility remained as long as the BiP promoter retained the sequences -107/-39. Using an in vitro gel mobility shift assay, an A23187-inducible nuclear factor (AINF) was detected from NIH3T3 cells. DNA binding competition experiments indicate that the -107/-39 segment contains a sequence motif which interacts with this cellular factor. Further analysis showed that the two direct repeats, ranging -108/-73 and -72/-40, are the target for AINF binding. A 3-4 fold increase of the AINF binding to both repeated sequences was detected from induced cells. Similar results were also demonstrated in HeLa cells, suggesting that transcriptional control of BiP gene expression in mammalian cells is conserved. These findings also imply that the identified nuclear factor may be important in mediating transcriptional activation of the BiP gene.

    Nucleic acids research 1992;20;24;6481-5

  • Treatment of Haemophilus aphrophilus endocarditis with ciprofloxacin.

    Dawson SJ and White LA

    Department of Microbiology, Southampton General Hospital, U.K.

    A patient with Haemophilus aphrophilus endocarditis was successfully treated with ciprofloxacin. The response to treatment with cefotaxime and netilmicin for 12 days was poor but was satisfactory to a 6 weeks' course of ciprofloxacin.

    The Journal of infection 1992;24;3;317-20

  • Regulating the retention of T-cell receptor alpha chain variants within the endoplasmic reticulum: Ca(2+)-dependent association with BiP.

    Suzuki CK, Bonifacino JS, Lin AY, Davis MM and Klausner RD

    Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.

    Immunoglobulin heavy chain binding protein (BiP, GRP 78) coprecipitates with soluble and membrane-associated variants of the T-cell antigen receptor alpha chain (TCR-alpha) which are stably retained within the ER. Chelation of Ca2+ during solubilization of cells leads to the dissociation of BiP from the TCR-alpha variants, which is dependent upon the availability of Mg2+ and hydrolyzable ATP; this suggests that Ca2+ levels can serve to modulate the association/dissociation of these proteins with BiP. In vivo treatment of cells expressing either the soluble or membrane-anchored TCR-alpha variants with the Ca2+ ionophore, A23187, or an inhibitor of an ER Ca(2+)-ATPase, thapsigargin, or the membrane-permeant Ca2+ chelator BAPTA-AM, results in the redistribution of these proteins out of the ER and their subsequent secretion or cell surface expression. Under the same assay conditions, no movement of BiP out of the ER is observed. Taken together, these observations indicate that decreased Ca2+ levels result in the dissociation of a protein bound to BiP, leading to its release from ER retention. These data suggest that the intracellular fate of newly synthesized proteins stably associated with BiP can be regulated by Ca2+ levels in the ER.

    The Journal of cell biology 1991;114;2;189-205

  • Folding, interaction with GRP78-BiP, assembly, and transport of the human immunodeficiency virus type 1 envelope protein.

    Earl PL, Moss B and Doms RW

    Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.

    A detailed kinetic and quantitative analysis of the early and late biosynthetic events undergone by the human immunodeficiency virus type 1 envelope protein expressed by a recombinant vaccinia virus was performed. Early folding events that occurred in the endoplasmic reticulum included disulfide bond formation (t1/2 approximately 10 min), folding of envelope protein into a form competent to bind CD4 (t1/2 approximately 15 min), and specific and transient association and dissociation with GRP78-BiP (t1/2 approximately 25 min). After initial folding, envelope protein monomers formed noncovalently associated dimers with high efficiency (t1/2 approximately 30 min). Studies with brefeldin A, a compound that inhibits endoplasmic reticulum-to-Golgi transport, suggested that assembly occurred in the endoplasmic reticulum while cleavage of gp160 into gp120/gp41 subunits occurred in a post-endoplasmic reticulum compartment. Transport to the Golgi was monitored by modification of N-linked sugars to forms partially resistant to endoglycosidase H. The kinetics of endoglycosidase H resistance were nearly identical to the kinetics of gp160 cleavage (t1/2 approximately 80 min). Cleavage efficiency was strongly cell type dependent, ranging from 13 to 70%. By contrast, approximately 50% of the gp120 generated by the cleavage event was shed (t1/2 approximately 120 min) regardless of the cell type used. The results are discussed in terms of the overall biosynthetic pathway of the envelope protein and provide a framework with which to assess the effects of mutations on structure and function.

    Journal of virology 1991;65;4;2047-55

  • Heat shock proteins bind calcitonin.

    Dana RC, Welch WJ and Deftos LJ

    Department of Medicine, University of California, La Jolla.

    We have demonstrated two heat shock proteins (HSP's) in the human placenta that specifically bind calcitonin. Binding specificity was shown by ligand-affinity chromatography and by competitive binding studies. The HSP's were identified by Western analysis and by amino acid sequence. Our observations are consistent with the hypothesis that HSP's may function by binding and interacting with cellular proteins and peptides during their biogenesis. This interaction may both depend upon and produce conformational changes in these ligands during their intracellular processing. Additionally, HSP-peptide hormone interactions may confound studies designed to investigate classical receptor-hormone interactions.

    Funded by: NIADDK NIH HHS: AM15888; NIGMS NIH HHS: GM33551

    Endocrinology 1990;126;1;672-4

  • Human gene encoding the 78,000-dalton glucose-regulated protein and its pseudogene: structure, conservation, and regulation.

    Ting J and Lee AS

    Department of Biochemistry, University of Southern California School of Medicine, Los Angeles 90033.

    Funded by: NCI NIH HHS: CA27607; NCRR NIH HHS: 1U41 RR-01695-01

    DNA (Mary Ann Liebert, Inc.) 1988;7;4;275-86

  • Molecular basis of the cell-surface expression of immunoglobulin mu chain without light chain in human B lymphocytes.

    Pollok BA, Anker R, Eldridge P, Hendershot L and Levitt D

    Guthrie Research Institute, Sayre, PA 18840.

    Four distinct human B-lymphoid cell lines possess the ability to circumvent the mechanism regulating intracellular transport of immunoglobulin protein. These cells do not produce light chains, yet they express mu heavy chains on the cell surface at comparable levels to B-cell lines that produce native forms of both proteins. The mu-chain mRNA produced in all four cell lines was found to contain an identical deletion of most of the heavy-chain variable (VH) region (75% of the 3' portion), with no apparent alteration in constant (C) region structure. The truncated mu (mu*)-chain mRNA in these cells was created through the use of a cryptic splice donor site found within the human VH gene(s) utilized by these B-cell lines. The truncated mu chains exhibited a decreased ability to associate with the intracellular transport regulatory protein, heavy-chain binding protein (BiP). This result indicates that VH region structure, in addition to C mu 1 region structure, influences the formation of the BiP recognition site on the heavy chain. Furthermore, it suggests that the mechanism allowing for cell-surface expression of the mu* chains in the absence of light-chain pairing is the inability of BiP to bind to the mu* chains and hence prevent their intracellular transport. The high frequency with which the mu-only surface immunoglobulin positive phenotype is present in our collection of human B-cell lines and the isolation of one of the cell lines from a healthy individual also suggest that B cells of this type may represent a significant subpopulation among the normal human B-cell repertoire.

    Proceedings of the National Academy of Sciences of the United States of America 1987;84;24;9199-203

  • An Hsp70-like protein in the ER: identity with the 78 kd glucose-regulated protein and immunoglobulin heavy chain binding protein.

    Munro S and Pelham HR

    We have characterized a cDNA clone that encodes a protein related to the 70 kd heat shock protein, but is expressed in normal rat liver. This protein has a hydrophobic leader and is secreted into the endoplasmic reticulum. We show that it is identical with two previously described proteins: GRP78, whose synthesis is induced by glucose starvation, and BiP, which is found bound to immunoglobulin heavy chains in pre-B cells. This protein, which is abundant in antibody-secreting cells, can be released from heavy chains by ATP, a reaction analogous to the release of hsp70 from heat shocked nuclear structures. We propose a specific role for this protein in the assembly of secreted and membrane-bound proteins.

    Cell 1986;46;2;291-300

  • BAP, a mammalian BiP-associated protein, is a nucleotide exchange factor that regulates the ATPase activity of BiP.

    Chung KT, Shen Y and Hendershot LM

    Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

    We identified a mammalian BiP-associated protein, BAP, using a yeast two-hybrid screen that shared low homology with yeast Sls1p/Sil1p and mammalian HspBP1, both of which regulate the ATPase activity of their Hsp70 partner. BAP encoded an approximately 54-kDa protein with an N-terminal endoplasmic reticulum (ER) targeting sequence, two sites of N-linked glycosylation, and a C-terminal ER retention sequence. Immunofluorescence staining demonstrated that BAP co-localized with GRP94 in the endoplasmic reticulum. BAP was ubiquitously expressed but showed the highest levels of expression in secretory organ tissues, a pattern similar to that observed with BiP. BAP binding was affected by the conformation of the ATPase domain of BiP based on in vivo binding studies with BiP mutants. BAP stimulated the ATPase activity of BiP when added alone or together with the ER DnaJ protein, ERdj4, by promoting the release of ADP from BiP. Together, these data demonstrate that BAP serves as a nucleotide exchange factor for BiP and provide insights into the mechanisms that control protein folding in the mammalian ER.

    Funded by: NCI NIH HHS: CA21765; NIGMS NIH HHS: GM54068

    The Journal of biological chemistry 20;277;49;47557-63

Gene lists (8)

Gene List Source Species Name Description Gene count
L00000009 G2C Homo sapiens Human PSD Human orthologues of mouse PSD adapted from Collins et al (2006) 1080
L00000011 G2C Homo sapiens Human clathrin Human orthologues of mouse clathrin coated vesicle genes adapted from Collins et al (2006) 150
L00000012 G2C Homo sapiens Human Synaptosome Human orthologues of mouse synaptosome adapted from Collins et al (2006) 152
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000059 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus 748
L00000061 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus (ortho) 984
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
L00000071 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list (ortho) 1556
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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