G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
G00000611 (Mus musculus)

Databases (9)

Curated Gene
OTTHUMG00000015917 (Vega human gene)
ENSG00000092820 (Ensembl human gene)
7430 (Entrez Gene)
1014 (G2Cdb plasticity & disease)
VIL2 (GeneCards)
123900 (OMIM)
Marker Symbol
HGNC:12691 (HGNC)
Protein Expression
4035 (human protein atlas)
Protein Sequence
P15311 (UniProt)

Literature (177)

Pubmed - other

  • Genetic susceptibility to distinct bladder cancer subphenotypes.

    Guey LT, García-Closas M, Murta-Nascimento C, Lloreta J, Palencia L, Kogevinas M, Rothman N, Vellalta G, Calle ML, Marenne G, Tardón A, Carrato A, García-Closas R, Serra C, Silverman DT, Chanock S, Real FX, Malats N and EPICURO/Spanish Bladder Cancer Study investigators

    Spanish National Cancer Research Centre, Madrid, Spain.

    Background: Clinical, pathologic, and molecular evidence indicate that bladder cancer is heterogeneous with pathologic/molecular features that define distinct subphenotypes with different prognoses. It is conceivable that specific patterns of genetic susceptibility are associated with particular subphenotypes.

    Objective: To examine evidence for the contribution of germline genetic variation to bladder cancer heterogeneity.

    The Spanish Bladder Cancer/EPICURO Study is a case-control study based in 18 hospitals located in five areas in Spain. Cases were patients with a newly diagnosed, histologically confirmed, urothelial cell carcinoma of the bladder from 1998 to 2001. Case diagnoses were reviewed and uniformly classified by pathologists following the World Health Organisation/International Society of Urological Pathology 1999 criteria. Controls were hospital-matched patients (n=1149).

    Measurements: A total of 1526 candidate variants in 423 candidate genes were analysed. Three distinct subphenotypes were defined according to stage and grade: low-grade nonmuscle invasive (n=586), high-grade nonmuscle invasive (n=219), and muscle invasive (n=246). The association between each variant and subphenotype was assessed by polytomous risk models adjusting for potential confounders. Heterogeneity in genetic susceptibility among subphenotypes was also tested.

    Two established bladder cancer susceptibility genotypes, NAT2 slow-acetylation and GSTM1-null, exhibited similar associations among the subphenotypes, as did VEGF-rs25648, which was previously identified in our study. Other variants conferred risks for specific tumour subphenotypes such as PMS2-rs6463524 and CD4-rs3213427 (respective heterogeneity p values of 0.006 and 0.004), which were associated with muscle-invasive tumours (per-allele odds ratios [95% confidence interval] of 0.56 [0.41-0.77] and 0.71 [0.57-0.88], respectively) but not with non-muscle-invasive tumours. Heterogeneity p values were not robust in multiple testing according to their false-discovery rate.

    Conclusions: These exploratory analyses suggest that genetic susceptibility loci might be related to the molecular/pathologic diversity of bladder cancer. Validation through large-scale replication studies and the study of additional genes and single nucleotide polymorphisms are required.

    Funded by: Intramural NIH HHS: ZIA CP010136-16

    European urology 2010;57;2;283-92

  • Internalization of NK cells into tumor cells requires ezrin and leads to programmed cell-in-cell death.

    Wang S, Guo Z, Xia P, Liu T, Wang J, Li S, Sun L, Lu J, Wen Q, Zhou M, Ma L, Ding X, Wang X and Yao X

    School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510641, China.

    Cytotoxic lymphocytes are key players in the orchestration of immune response and elimination of defective cells. We have previously reported that natural killer (NK) cells enter target tumor cells, leading to either target cell death or self-destruction within tumor cells. However, it has remained elusive as to the fate of NK cells after internalization and whether the heterotypic cell-in-cell process is different from that of the homotypic cell-in-cell event recently named entosis. Here, we show that NK cells undergo a cell-in-cell process with the ultimate fate of apoptosis within tumor cells and reveal that the internalization process requires the actin cytoskeletal regulator, ezrin. To visualize how NK cells enter into tumor cells, we carried out real-time dual color imaging analyses of NK cell internalization into tumor cells. Surprisingly, most NK cells commit to programmed cell death after their entry into tumor cells, which is distinctively different from entosis observed in the homotypic cell-in-cell process. The apoptotic cell death of the internalized NK cells was evident by activation of caspase 3 and DNA fragmentation. Furthermore, NK cell death after internalization is attenuated by the caspase inhibitor, Z-VAD-FMK, confirming apoptosis as the mode of NK cell death within tumor cells. To determine protein factors essential for the entry of NK cells into tumor cells, we carried out siRNA-based knockdown analysis and discovered a critical role of ezrin in NK cell internalization. Importantly, PKA-mediated phosphorylation of ezrin promotes the NK cell internalization process. Our findings suggest a novel regulatory mechanism by which ezrin governs NK cell internalization into tumor cells.

    Cell research 2009;19;12;1350-62

  • PTEN identified as important risk factor of chronic obstructive pulmonary disease.

    Hosgood HD, Menashe I, He X, Chanock S and Lan Q

    Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.

    Common genetic variation may play an important role in altering chronic obstructive pulmonary disease (COPD) risk. In Xuanwei, China, the COPD rate is more than twice the Chinese national average, and COPD is strongly associated with in-home coal use. To identify genetic variation that may be associated with COPD in a population with substantial in-home coal smoke exposures, we evaluated 1261 single nucleotide polymorphisms (SNPs) in 380 candidate genes potentially relevant for cancer and other human diseases in a population-based case-control study in Xuanwei (53 cases; 107 controls). PTEN was the most significantly associated gene with COPD in a minP analysis using 20,000 permutations (P=0.00005). SNP-based analyses found that homozygote variant carriers of PTEN rs701848 (OR(TT)=0.12, 95% CI=0.03-0.47) had a significant decreased risk of COPD. PTEN, or phosphatase and tensin homolog, is an important regulator of cell cycle progression and cellular survival via the AKT signaling pathway. Our exploratory analysis suggests that genetic variation in PTEN may be an important risk factor of COPD in Xuanwei. However, due to the small sample size, additional studies are needed to evaluate these associations within Xuanwei and other populations with coal smoke exposures.

    Funded by: Intramural NIH HHS: Z99 CA999999

    Respiratory medicine 2009;103;12;1866-70

  • Regulation of NK cell trafficking by CD81.

    Krämer B, Schulte D, Körner C, Zwank C, Hartmann A, Michalk M, Söhne J, Langhans B, Nischalke HD, Coenen M, Möhl C, Vogt A, Hennenberg M, Sauerbruch T, Spengler U and Nattermann J

    Department of Internal Medicine I, University of Bonn, Bonn, Germany.

    NK cells, a heterogeneous sub-population of lymphocytes, are critically involved in the regulation of both innate and adaptive immune responses in humans. Besides their participation in the control of tumors and viral infections, they also regulate inflammatory processes, mediating both beneficial and detrimental effects. To effectively fulfil their role in immune surveillance, proper trafficking of NK cells is essential. However, the mechanisms and factors governing NK cell recruitment are only poorly dissected. Here, we describe the functional role of tetraspanins, a family of evolutionary conserved cell-surface proteins, in modulating migration and transmigration of human NK cells. We demonstrate expression of various tetraspanins on NK cells. Furthermore, we show that stimulation of the NK cell-expressed tetraspanin CD81 induces phosphorylation of ezrin/radixin/moesin proteins and leads to NK cell polarization thereby facilitating NK cell migration toward various chemokines/cytokines. Finally, we provide evidence for a role of CD81 in promoting adhesion of NK cells to components of the extracellular matrix, a prerequisite for extravasation of lymphocytes in inflamed tissues. Thus, our data suggest that the tetraspanin CD81 is importantly involved in the regulation of NK cell recruitment.

    European journal of immunology 2009;39;12;3447-58

  • Phosphorylation of ezrin/radixin/moesin proteins by LRRK2 promotes the rearrangement of actin cytoskeleton in neuronal morphogenesis.

    Parisiadou L, Xie C, Cho HJ, Lin X, Gu XL, Long CX, Lobbestael E, Baekelandt V, Taymans JM, Sun L and Cai H

    Unit of Transgenesis, Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20892, USA.

    Leucine-rich repeat kinase 2 (LRRK2) functions as a putative protein kinase of ezrin, radixin, and moesin (ERM) family proteins. A Parkinson's disease-related G2019S substitution in the kinase domain of LRRK2 further enhances the phosphorylation of ERM proteins. The phosphorylated ERM (pERM) proteins are restricted to the filopodia of growing neurites in which they tether filamentous actin (F-actin) to the cytoplasmic membrane and regulate the dynamics of filopodia protrusion. Here, we show that, in cultured neurons derived from LRRK2 G2019S transgenic mice, the number of pERM-positive and F-actin-enriched filopodia was significantly increased, and this correlates with the retardation of neurite outgrowth. Conversely, deletion of LRRK2, which lowered the pERM and F-actin contents in filopodia, promoted neurite outgrowth. Furthermore, inhibition of ERM phosphorylation or actin polymerization rescued the G2019S-dependent neuronal growth defects. These data support a model in which the G2019S mutation of LRRK2 causes a gain-of-function effect that perturbs the homeostasis of pERM and F-actin in sprouting neurites critical for neuronal morphogenesis.

    Funded by: Intramural NIH HHS: Z01 AG000944-01, Z01 AG000959-04, Z01 AG000959-05, ZIA AG000944-02, ZIA AG000959-06; NIA NIH HHS: AG000944-01, Z01 AG000944

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;44;13971-80

  • Ezrin overexpression in gastrointestinal stromal tumors: an independent adverse prognosticator associated with the non-gastric location.

    Wei YC, Li CF, Yu SC, Chou FF, Fang FM, Eng HL, Uen YH, Tian YF, Wu JM, Li SH, Huang WW, Li WM and Huang HY

    Department of Pathology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan.

    Ezrin, a member of the ezrin-radixin-moesin family, acts as a link between the cell membrane and actin cytoskeleton to integrate cell adhesion-mediated signaling. It implicates tumor progression, metastatic dissemination, and adverse outcomes in several cancer types, including pediatric and adult sarcomas. Although ezrin upregulation was shown by cDNA expression profiling, no study has systematically evaluated the significance of ezrin expression in a large cohort of gastrointestinal stromal tumors (GISTs). Ezrin immunostaining was carried out on tissue microarrays of primary GISTs and assessable in 347 cases, 188 of which were successfully evaluated for mutation variants of KIT and PDGFRA receptor tyrosine kinase (RTK) genes by sequencing with or without screening by denatured high-performance liquid chromatography. These GISTs with known RTK genotypes were dichotomized into two prognostically different groups. The endogenous expression and phosphorylation of ezrin in GIST cell lines were analyzed by western blotting. By immunohistochemistry, ezrin overexpression was present in 66% of GISTs and significantly associated with the non-gastric location (P=0.002) and decreased disease-free survival (P=0.032, univariately). However, it was not related to the National Institute of Health (NIH) risk category, Ki-67 labeling index, RTK genotypes, and other variables. In multivariate analyses, ezrin overexpression remained independently predictive of adverse outcome (P=0.008, risk ratio=2.363), together with Ki-67 labeling index >5% (P<0.001, risk ratio=3.581), high-risk category (P<0.001, risk ratio=2.156), and the non-gastric location (P=0.029, risk ratio=1.899). Despite the variation in the ezrin expression level, phosphorylated ezrin at threonine(567) was only detectable in GIST882 and GIST48 cells, but not in colonic smooth muscle cells. In conclusion, ezrin is frequently overexpressed in GISTs, especially those arising from the non-gastric sites. Given that its impact is independent of the NIH risk category, cell proliferation, and tumor location, ezrin immunoreactivity represents a valuable prognostic adjunct of GISTs, suggesting a causative role in conferring an aggressive phenotype.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2009;22;10;1351-60

  • Beta4 integrin promotes osteosarcoma metastasis and interacts with ezrin.

    Wan X, Kim SY, Guenther LM, Mendoza A, Briggs J, Yeung C, Currier D, Zhang H, Mackall C, Li WJ, Tuan RS, Deyrup AT, Khanna C and Helman L

    Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892-1928, USA. xiaolinw@mail.nih.gov

    The development of pulmonary metastasis is the major cause of death in osteosarcoma, and its molecular basis is poorly understood. In this study, we show that beta4 integrin is highly expressed in human osteosarcoma cell lines and tumor samples. Furthermore, highly metastatic MNNG-HOS cells have increased levels of beta4 integrin. Suppression of beta4 integrin expression by shRNA and disruption of beta4 integrin function by transfection of dominant-negative beta4 integrin was sufficient to revert this highly metastatic phenotype in the MNNG-HOS model without significantly affecting primary tumor growth. These findings suggest a role for beta4 integrin expression in the metastatic phenotype in human osteosarcoma cells. In addition, we identified a previously uncharacterized interaction between beta4 integrin and ezrin, a membrane-cytoskeletal linker protein that is implicated in the metastatic behavior of osteosarcoma. The beta4 integrin-ezrin interaction appears to be critical for maintenance of beta4 integrin expression. These data begin to integrate ezrin and beta4 integrin expression into a model of action for the mechanism of osteosarcoma metastases.

    Funded by: NCI NIH HHS: Z01 SC006891-19, Z01 SC006892-19, Z99 CA999999

    Oncogene 2009;28;38;3401-11

  • Ezrin induces long-range interdomain allostery in the scaffolding protein NHERF1.

    Li J, Callaway DJ and Bu Z

    Fox Chase Cancer Center, Philadelphia, PA 19111, USA.

    Scaffolding proteins are molecular switches that control diverse signaling events. The scaffolding protein Na(+)/H(+) exchanger regulatory factor 1 (NHERF1) assembles macromolecular signaling complexes and regulates the macromolecular assembly, localization, and intracellular trafficking of a number of membrane ion transport proteins, receptors, and adhesion/antiadhesion proteins. NHERF1 begins with two modular protein-protein interaction domains-PDZ1 and PDZ2-and ends with a C-terminal (CT) domain. This CT domain binds to ezrin, which, in turn, interacts with cytosekeletal actin. Remarkably, ezrin binding to NHERF1 increases the binding capabilities of both PDZ domains. Here, we use deuterium labeling and contrast variation neutron-scattering experiments to determine the conformational changes in NHERF1 when it forms a complex with ezrin. Upon binding to ezrin, NHERF1 undergoes significant conformational changes in the region linking PDZ2 and its CT ezrin-binding domain, as well as in the region linking PDZ1 and PDZ2, involving very long range interactions over 120 A. The results provide a structural explanation, at mesoscopic scales, of the allosteric control of NHERF1 by ezrin as it assembles protein complexes. Because of the essential roles of NHERF1 and ezrin in intracellular trafficking in epithelial cells, we hypothesize that this long-range allosteric regulation of NHERF1 by ezrin enables the membrane-cytoskeleton to assemble protein complexes that control cross-talk and regulate the strength and duration of signaling.

    Funded by: NHLBI NIH HHS: R01 HL086496, R01 HL086496-01A1, R01 HL086496-02

    Journal of molecular biology 2009;392;1;166-80

  • Engagement of CD81 induces ezrin tyrosine phosphorylation and its cellular redistribution with filamentous actin.

    Coffey GP, Rajapaksa R, Liu R, Sharpe O, Kuo CC, Krauss SW, Sagi Y, Davis RE, Staudt LM, Sharman JP, Robinson WH and Levy S

    Stanford University, School of Medicine, Division of Oncology, Stanford, CA 94305, USA.

    CD81 is a tetraspanin family member involved in diverse cellular interactions in the immune and nervous systems and in cell fusion events. However, the mechanism of action of CD81 and of other tetraspanins has not been defined. We reasoned that identifying signaling molecules downstream of CD81 would provide mechanistic clues. We engaged CD81 on the surface of B-lymphocytes and identified the induced tyrosine-phosphorylated proteins by mass spectrometry. This analysis showed that the most prominent tyrosine phosphorylated protein was ezrin, an actin-binding protein and a member of the ezrin-radixin-moesin family. We also found that CD81 engagement induces spleen tyrosine kinase (Syk) and that Syk was involved in tyrosine phosphorylation of ezrin. After engagement of CD81, it colocalized with ezrin and F-actin, and this association was disrupted when Syk activation was blocked. Taken together, these studies suggest a model in which CD81 interfaces between the plasma membrane and the cytoskeleton by activating Syk, mobilizing ezrin, and recruiting F-actin to facilitate cytoskeletal reorganization and cell signaling. This mechanism might explain the pleiotropic effects induced in response to stimulation of cells by anti-CD81 antibodies or by the hepatitis C virus, which uses this molecule as its key receptor.

    Funded by: NIAID NIH HHS: AI068100; NIDDK NIH HHS: DK059079

    Journal of cell science 2009;122;Pt 17;3137-44

  • The calcineurin homologous protein-1 increases Na(+)/H(+) -exchanger 3 trafficking via ezrin phosphorylation.

    Di Sole F, Babich V and Moe OW

    Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-8885, USA. francesca.disole@utsouthwestern.edu

    The Na(+)/H(+)-exchanger 3 (NHE3) is essential for regulation of Na(+) transport in the renal and intestinal epithelium. Although changes in cell surface abundance control NHE3 function, the molecular signals that regulate NHE3 surface expression are not well defined. We found that overexpression of the calcineurin homologous protein-1 (CHP1) in opossum kidney cells increased NHE3 transport activity, surface protein abundance, and ezrin phosphorylation. CHP1 knockdown by small interfering RNA had the opposite effects. Overexpression of wild-type ezrin increased both NHE3 transport activity and surface protein abundance, confirming that NHE3 is downstream of ezrin. Expression of a pseudophosphorylated ezrin enhanced these effects, whereas expression of an ezrin variant that could not be phosphorylated prevented the downstream effects on NHE3. Furthermore, CHP1 knockdown reversed the activation of NHE3 by wild-type ezrin but not by the pseudophosphorylated ezrin. Taken together, these results demonstrate that CHP1 increases NHE3 abundance and constitutive function in a manner dependent on ezrin phosphorylation.

    Funded by: NIDDK NIH HHS: DK-48482, DK-54396

    Journal of the American Society of Nephrology : JASN 2009;20;8;1776-86

  • The role of the membrane cytoskeleton cross-linker ezrin in medulloblastoma cells.

    Osawa H, Smith CA, Ra YS, Kongkham P and Rutka JT

    Division of Neurosurgery, The Hospital for Sick Children, Toronto, ONM5G 1X8, Canada.

    Medulloblastoma is a highly malignant brain tumor that occurs predominantly in children. The molecular pathogenesis of medulloblastoma is under investigation. Previously, we used complementary DNA microarray analysis to compare patterns of gene expression in medulloblastoma samples versus normal cerebellum. The cytoskeletal protein ezrin was found to be overexpressed in medulloblastoma compared with normal cerebellum, an observation that was further validated by immunohistochemistry and real-time PCR analysis. To assess the role of ezrin in medulloblastoma, we studied ezrin's role in medulloblastoma migration, invasion, and adhesion. Western blotting and immunofluorescence showed high expression of ezrin in four medulloblastoma cell lines, and ezrin was primarily localized to filopodia. Ezrin-specific small interfering RNA suppressed the formation of filopodia and in vitro migration, invasion, and adhesion. We also used a stably transfected medulloblastoma cell line to study the effect of ezrin overexpression. We showed that high expression of ezrin promotes filopodia formation and in vitro invasion. Finally, athymic mice implanted with ezrin-overexpressing DAOY medullo-blastoma cell clones in the cerebellum showed shortened survival compared with controls. These findings suggest that, in addition to other cytoskeletal proteins, ezrin plays an important role in medulloblastoma adhesion, migration, and invasion.

    Neuro-oncology 2009;11;4;381-93

  • Defining the human deubiquitinating enzyme interaction landscape.

    Sowa ME, Bennett EJ, Gygi SP and Harper JW

    Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

    Deubiquitinating enzymes (Dubs) function to remove covalently attached ubiquitin from proteins, thereby controlling substrate activity and/or abundance. For most Dubs, their functions, targets, and regulation are poorly understood. To systematically investigate Dub function, we initiated a global proteomic analysis of Dubs and their associated protein complexes. This was accomplished through the development of a software platform called CompPASS, which uses unbiased metrics to assign confidence measurements to interactions from parallel nonreciprocal proteomic data sets. We identified 774 candidate interacting proteins associated with 75 Dubs. Using Gene Ontology, interactome topology classification, subcellular localization, and functional studies, we link Dubs to diverse processes, including protein turnover, transcription, RNA processing, DNA damage, and endoplasmic reticulum-associated degradation. This work provides the first glimpse into the Dub interaction landscape, places previously unstudied Dubs within putative biological pathways, and identifies previously unknown interactions and protein complexes involved in this increasingly important arm of the ubiquitin-proteasome pathway.

    Funded by: NIA NIH HHS: AG085011, R01 AG011085, R01 AG011085-16; NIDDK NIH HHS: K01 DK098285; NIGMS NIH HHS: GM054137, GM67945, R01 GM054137, R01 GM054137-14, R01 GM067945

    Cell 2009;138;2;389-403

  • Roles of ezrin in the growth and invasiveness of esophageal squamous carcinoma cells.

    Xie JJ, Xu LY, Xie YM, Zhang HH, Cai WJ, Zhou F, Shen ZY and Li EM

    Department of Biochemistry and Molecular Biology, Medical College of Shantou University, Shantou, People's Republic of China.

    Ezrin, which crosslinks the cytoskeleton and plasma membrane, is involved in the growth and metastatic potential of cancer cells. Ezrin expression in esophageal squamous cell carcinoma (ESCC) was described recently, but its roles and the underlying mechanism(s) remain unclear. In our study, we first showed that ezrin in ESCC cell is expressed in the nucleus as well as in the cytoplasm and plasma membrane. Then, by using RNAi, we revealed that interference of ezrin expression suppressed the growth, adhesion and invasiveness of ESCC cells. Tumorigenesis experiments revealed that ezrin may directly regulate tumor formation in vivo. To explore the molecular mechanisms through which ezrin contributes to the proliferation and invasiveness of ESCC cells, we used cDNA microarrays to analyze ezrin knockdown cells and the control cells; of 39,000 genes examined, 297 were differentially expressed upon ezrin knockdown, including some proliferation- and invasiveness-related genes such as ATF3, CTGF and CYR61. Furthermore, pathway analysis showed that ezrin knockdown led to decreased activation of the TGF-beta and MAPK pathways, and ezrin-mediated cell invasiveness alteration was dependent on the activation of these pathways. Finally, immunohistochemical staining on 80 ESCC specimens and 50 normal esophageal mucosae revealed that the expression levels of 3 altered genes involved in the regulation of cell proliferation and tumor metastasis, including CTGF, CYR61 and ATF3, were altered in ESCCs, and their expression pattern correlated with ezrin expression. Taken together, we propose that ezrin might function in the growth and invasiveness of ESCC cells through the MAPK and TGF-beta pathways.

    International journal of cancer. Journal international du cancer 2009;124;11;2549-58

  • The classic prognostic factors tumor stage, tumor size, and tumor grade are the strongest predictors of outcome in synovial sarcoma: no role for SSX fusion type or ezrin expression.

    ten Heuvel SE, Hoekstra HJ, Bastiaannet E and Suurmeijer AJ

    Department of Surgical Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.

    Background: The aim of this study was to investigate prognostic factors influencing the survival of synovial sarcoma, including the debated role of SYT-SSX fusion type and the newly suggested immunohistochemical marker ezrin.

    From 1984 to 2005, 45 patients-25 men (56%) and 20 women (44%) with a median age of 31 (range: 2 to 81) years-were diagnosed with a synovial sarcoma. Age at diagnosis, tumor site, tumor size, tumor histology (biphasic vs. monophasic), mitotic count, necrosis, histologic grade, SYT-SSX fusion type, and ezrin immunostaining were analyzed for influence on survival by univariate and multivariate methods.

    Results: The median follow-up for all patients was 55 (range: 2 to 238) months. Five patients had metastatic disease at the time of presentation. Five-year disease-specific survivals (DSS) were 67% overall and 72% for the 40 patients presenting with localized disease at diagnosis. Nineteen patients (48%) developed metastases during follow-up. Five-year metastasis-free survival (MFS) for the 40 patients with localized disease at diagnosis was 60% and the 10-year MFS was 52%. Disease stage at presentation, tumor size >5 cm, and histologic grade 3 were univariate significant factors associated with a worse DSS. Age >or=30 years, tumor size >5 cm, necrosis, and histologic grade were univariate significant factors associated with a worse MFS. In multivariate analysis, tumor size and tumor grade remained significant prognostic factors for DSS and MFS. A role of SYT-SSX fusion type could not be confirmed in our patient group. Ezrin showed high expression in glandular and nonglandular epithelioid components in biphasic synovial sarcoma. Variable expression was found in the mesenchymal component of monophasic and biphasic synovial sarcoma. Low versus high ezrin expression levels in monophasic and/or biphasic synovial sarcoma did not correlate with patient outcome.

    Conclusions: Disease stage at presentation, tumor size, and tumor grade were significant predictors of survival in synovial sarcoma. SYT-SSX fusion type was not correlated with survival in our series. Ezrin expression levels were not discriminative in predicting outcome.

    Applied immunohistochemistry & molecular morphology : AIMM 2009;17;3;189-95

  • High level of ezrin expression in colorectal cancer tissues is closely related to tumor malignancy.

    Wang HJ, Zhu JS, Zhang Q, Sun Q and Guo H

    Department of Gastroenterology, The Sixth People's Hospital Affiliated to Shanghai Jiao Tong University, Shanghai, China.

    Aim: To investigate the ezrin expression in normal colorectal mucosa and colorectal cancer tissues, and study the correlation between ezrin expression in colorectal cancer tissues and tumor invasion and metastasis.

    Methods: Eighty paraffin-embedded cancer tissue samples were selected from primary colorectal adenocarcinoma. Twenty-eight patients had well-differentiated, 22 had moderately differentiated and 30 had poorly differentiated adenocarcinoma. Forty-five patients and 35 patients had lymph node metastasis. Forty-five patients were of Dukes A to B stage, and 35 were of C to D stage. Another 22 paraffin-embedded tissue blocks of normal colorectal epithelium (> 5 cm away from the edge of the tumor) were selected as the control group. All patients with colorectal cancer were treated surgically and diagnosed histologically, without preoperative chemotherapy or radiotherapy. The immunohistochemistry was used to detect the ezrin expression in paraffin-embedded normal colorectal mucosa tissues and colorectal cancer tissue samples.

    Results: Ezrin expression in colorectal cancer was significantly higher than in normal colorectal mucosa (75.00% vs 9.09%, P < 0.01), and there was a close relationship between ezrin expression and the degree of tumor differentiation, lymph node metastasis and Dukes stage (88.46% vs 50.00%, P < 0.01; 94.28% vs 51.11%, P < 0.01; 94.28% vs 51.11%, P < 0.01).

    Conclusion: Ezrin expression is obviously higher in colorectal cancer tissues than in normal colorectal mucosa tissues, and the high level of ezrin expression is closely related to the colorectal cancer invasion and metastasis process.

    World journal of gastroenterology : WJG 2009;15;16;2016-9

  • Phosphorylated ezrin is associated with EBV latent membrane protein 1 in nasopharyngeal carcinoma and induces cell migration.

    Endo K, Kondo S, Shackleford J, Horikawa T, Kitagawa N, Yoshizaki T, Furukawa M, Zen Y and Pagano JS

    Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599-7295, USA.

    Tumor metastasis is a complex phenomenon that is the culmination of effects of numerous cellular factors. We have shown that the Epstein-Barr virus (EBV) oncoprotein, latent membrane protein 1 (LMP1), is capable of inducing a wide range of such factors in cell culture, expression of which is also elevated in the LMP1-expressing tumor, nasopharyngeal carcinoma (NPC), a highly invasive neoplasm. Recently, the membrane crosslinker protein, ezrin, has been implicated in tumor cell metastasis and malignant progression. In this study, we evaluated the possible role of LMP1 and ezrin in the pathophysiology of NPC. We show that C-terminal phosphorylation of ezrin is increased by the expression of LMP1 in nasopharyngeal (NP) cells through a protein kinase C (PKC) pathway. LMP1 enhances the organization of a ternary complex of CD44, ezrin and F-actin, which is a prerequisite for ezrin phosphorylation. In NPC tissues, the expression of phosphoezrin and LMP1 is directly correlated. Silencing of endogenously expressed ezrin suppresses LMP1-induced cell motility and invasiveness. Moreover, the inhibition of ezrin phosphorylation by PKC inhibitor suppresses migration and invasion of NP cells. These data show that the phosphorylation of ezrin and its recruitment to the cell membrane linked to F-actin and CD44 is a process required for LMP1-stimulated cell motility and invasion of NP cells.

    Funded by: NCI NIH HHS: CA 19014; NIAID NIH HHS: R21 AI042371-06

    Oncogene 2009;28;14;1725-35

  • Expression of Ezrin correlates with lung metastasis in Chinese patients with osteosarcoma.

    Xu-Dong S, Zan S, Shui-er Z, Li-na T, Wen-xi Y, Feng L and Yang Y

    Department of Oncology, Shanghai 6th People's Hospital, Shanghai Jiao Tong University, Shanghai, China.

    Purpose: To determine the prognostic value of the expression of Ezrin, CD44 and Six1 genes in osteosarcoma tissues of Chinese patients.

    Methods: Fluorescent quantitative real-time PCR was applied to study the mRNA levels of Ezrin, CD44 and Six1 genes in 32 osteosarcoma patient samples and 10 adjacent normal tissues and MG63 osteosarcoma cell lines. The analysis of relationships between pulmonary metastasis and overall survival time were carried out based on the clinical data.

    Results: mRNA levels of Ezrin and Six1 genes in osteosarcoma tissues were higher than those in adjacent normal tissues (P=0.015, 0.025). The mRNA levels of Ezrin, CD44 and Six1 genes were closely correlated with Enneking GTM clinical staging, while no correlations were demonstrated between the mRNA level of these genes with sex, age, location or pathological types. In addition, we demonstrated that the high mRNA level of Ezrin gene was related to shorter lung metastasis-free and overall survival time of the Chinese patients with osteosarcoma (P < 0.001).

    Conclusion: Our data suggest that Ezrin, but not CD44 and Six1, could be a prognostic factor and a predictor of potential lung metastasis in osteosarcoma. Further large sample studies need to be done to confirm the potential value of Ezrin as a new therapeutic target.

    Clinical and investigative medicine. Medecine clinique et experimentale 2009;32;2;E180-8

  • Proteomic profiling in pancreatic cancer with and without lymph node metastasis.

    Cui Y, Wu J, Zong M, Song G, Jia Q, Jiang J and Han J

    Shandong Medicinal Biotechnology Center, Shandong Academy of Medical Sciences, Key Laboratory for Biotech-Drugs Ministry of Health, Key Laboratory for Modern Medicine and Technology of Shandong Province. Jinan, China.

    The aim of the study was to observe different protein profiles in pancreatic cancer with and without lymph node metastasis (LNM), and search for novel LNM-associated proteins, which would help to understand the metastatic mechanisms and provide targets for therapeutic interventions. Cancer nests were manually miscrodissected from 8 LNM and 7 non-LNM pancreatic cancer tissues, and the protein extracts were then separated by difference gel electrophoresis (DIGE) and identified by MALDI-TOF-TOF. Four differently regulated proteins, ezrin, radixin, moesin, and c14orf166, were selected for further validation by Western blot and immunohistochemistry. In DIGE analysis, we identified 18 up-regulated proteins and 15 down-regulated proteins in LNM pancreatic cancer nests compared with non-LNM ones. Western blot and immunohistochemical analyses confirmed that radixin, moesin and c14orf166, but not ezrin, had significantly higher expression levels in LNM pancreatic cancers than in non-LNM controls. In conclusion, the specific protein profiles found in this study might provide new insights into the mechanism of lymph node metastasis. For the first time, c14orf166 was identified asa novel metastasis-associated protein, and the roles of radixin, moesin and c14orf166 in cancer metastasis deserve further investigations.

    International journal of cancer. Journal international du cancer 2009;124;7;1614-21

  • Mst4 and Ezrin induce brush borders downstream of the Lkb1/Strad/Mo25 polarization complex.

    ten Klooster JP, Jansen M, Yuan J, Oorschot V, Begthel H, Di Giacomo V, Colland F, de Koning J, Maurice MM, Hornbeck P and Clevers H

    Hubrecht Institute, KNAW and University Medical Centre, Utrecht, The Netherlands.

    The human Lkb1 kinase, encoded by the ortholog of the invertebrate Par4 polarity gene, is mutated in Peutz-Jeghers cancer syndrome. Lkb1 activity requires complex formation with the pseudokinase Strad and the adaptor protein Mo25. The complex can induce complete polarization in a single isolated intestinal epithelial cell. We describe an interaction between Mo25alpha and a human serine/threonine kinase termed Mst4. A homologous interaction occurs in the yeast Schizosaccharomyces pombe in the control of polar tip growth. Human Mst4 translocates from the Golgi to the subapical membrane compartment upon activation of Lkb1. Inhibition of Mst4 activity inhibits Lkb1-induced brush border formation, whereas other aspects of polarity such as the formation of lateral junctions remain unaffected. As an essential event in brush border formation, Mst4 phosphorylates the regulatory T567 residue of Ezrin. These data define a brush border induction pathway downstream of the Lkb1/Strad/Mo25 polarization complex, yet separate from other polarity events.

    Developmental cell 2009;16;4;551-62

  • In Vitro and in Vivo Characterization of Molecular Interactions between Calmodulin, Ezrin/Radixin/Moesin, and L-selectin.

    Killock DJ, Parsons M, Zarrouk M, Ameer-Beg SM, Ridley AJ, Haskard DO, Zvelebil M and Ivetic A

    Cardiovascular Science Unit, National Heart and Lung Institute, Imperial College London, Hammersmith Campus, London W12 0NN.

    L-selectin is a cell adhesion molecule that tethers leukocytes to the luminal walls of venules during inflammation and enables them to roll under the force of blood flow. Clustering of L-selectin during rolling is thought to promote outside-in signals that lead to integrin activation and chemokine receptor expression, ultimately contributing to leukocyte arrest. Several studies have underscored the importance of the L-selectin cytoplasmic tail in functionally regulating adhesion and signaling. Interestingly, the L-selectin tail comprises only 17 amino acids, and yet it is thought to bind simultaneously to several proteins. For example, constitutive association of calmodulin (CaM) and ezrin/radixin/moesin (ERM) to L-selectin confers resistance to proteolysis and microvillar positioning, respectively. In this report we found that recombinant purified CaM and ERM bound non-competitively to the same tail of L-selectin. Furthermore, molecular modeling supported the possibility that CaM, L-selectin, and moesin could form a heterotrimeric complex. Finally, using fluorescence lifetime imaging microscopy to measure fluorescence resonance energy transfer, it was shown that CaM, L-selectin, and ERM could interact simultaneously in vivo. Moreover, L-selectin clustering promoted CaM/ERM interaction in cis (i.e. derived from neighboring L-selectin tails). These results highlight a novel intracellular event that occurs as a consequence of L-selectin clustering, which could participate in transducing signals that promote the transition from rolling to arrest.

    Funded by: Wellcome Trust

    The Journal of biological chemistry 2009;284;13;8833-45

  • LOK is a major ERM kinase in resting lymphocytes and regulates cytoskeletal rearrangement through ERM phosphorylation.

    Belkina NV, Liu Y, Hao JJ, Karasuyama H and Shaw S

    Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.

    ERM (ezrin-radixin-moesin) proteins mediate linkage of actin cytoskeleton to plasma membrane in many cells. ERM activity is regulated in part by phosphorylation at a C-terminal threonine, but the identity of ERM kinases is unknown in lymphocytes and incompletely defined in other mammalian cells. Our studies show that lymphocyte-oriented kinase (LOK) is an ERM kinase in vitro and in vivo. Mass spectrometric analysis indicates LOK is abundant at the lymphocyte plasma membrane and immunofluorescence studies show LOK enrichment at the plasma membrane near ERM. In vitro peptide specificity analyses characterize LOK as a basophilic kinase whose optimal substrate sequence resembles the ERM site, including unusual preference for tyrosine at P-2. LOK's activity on moesin peptide and protein was comparable to reported ERM kinases ROCK and PKC but unlike them LOK displayed preferential specificity for moesin compared to traditional basophilic kinase substrates. Two genetic approaches demonstrate a role for LOK in ERM phosphorylation: cell transfection with LOK kinase domain augments ERM phosphorylation and lymphocytes from LOK knockout mice have >50% reduction in ERM phosphorylation. The findings on localization and specificity argue that LOK is a direct ERM kinase. The knockout mice have normal hematopoietic cell development but notably lymphocyte migration and polarization in response to chemokine are enhanced. These functional alterations fit the current understanding of the role of ERM phosphorylation in regulating cortical reorganization. Thus, these studies identify a new ERM kinase of importance in lymphocytes and confirm the role of ERM phosphorylation in regulating cell shape and motility.

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;12;4707-12

  • Sp1 and AP-1 regulate expression of the human gene VIL2 in esophageal carcinoma cells.

    Gao SY, Li EM, Cui L, Lu XF, Meng LY, Yuan HM, Xie JJ, Du ZP, Pang JX and Xu LY

    Department of Biochemistry and Molecular Biology, Shantou University, Shantou, China.

    Ezrin, encoded by VIL2, is a membrane-cytoskeletal linker protein that has been suggested to be involved in tumorigenesis. Ezrin expression in esophageal squamous cell carcinoma (ESCC) was described recently, but its clinical significance and the molecular mechanism underlying its regulated expression remain unclear. Thus, we retrospectively evaluated ezrin expression by immunohistochemistry in a tissue microarray representing 193 ESCCs. Ezrin overexpression in 90 of 193 tumors (46.6%) was associated with poor survival (p = 0.048). We then explored the mechanism by which ezrin expression is controlled in ESCC by assessing the transcriptional regulatory regions of human VIL2 by fusing deletions or site-directed mutants of the 5'-flanking region of the gene to a luciferase reporter. We found that the region -87/-32 containing consensus Sp1 (-75/-69) and AP-1 (-64/-58) binding sites is crucial for VIL2 promoter activity in esophageal carcinoma cells (EC109) derived from ESCC. AP-1 is comprised of c-Jun and c-Fos. Electrophoretic mobility shift and chromatin immunoprecipitation experiments demonstrated that Sp1 and c-Jun bound specifically to their respective binding sites within the VIL2 promoter. In addition, transient expression of Sp1, c-Jun, or c-Fos increased ezrin expression and VIL2 promoter activity. Use of selective inhibitors revealed that VIL2 transactivation required the MEK1/2 signal transduction pathway but not JNK or p38 MAPK. Taken together, we propose a possible signal transduction pathway whereby MEK1/2 phosphorylates ERK1/2, which phosphorylates Sp1 and AP-1 that in turn bind to their respective binding sites to regulate the expression of human VIL2 in ESCC cells.

    The Journal of biological chemistry 2009;284;12;7995-8004

  • The actin-cytoskeleton linker protein ezrin is regulated during osteosarcoma metastasis by PKC.

    Ren L, Hong SH, Cassavaugh J, Osborne T, Chou AJ, Kim SY, Gorlick R, Hewitt SM and Khanna C

    Tumor and Metastasis Biology Section, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.

    Ezrin is a member of the ERM (ezrin, radixin, moesin) protein family and links F-actin to the cell membrane following phosphorylation. Ezrin has been associated with tumor progression and metastasis in several cancers including the pediatric solid tumors, osteosarcoma and rhabdomyosarcoma. In this study, we were surprised to find that ezrin was not constitutively phosphorylated but rather was dynamically regulated during metastatic progression in osteosarcoma. Metastatic osteosarcoma cells expressed phosphorylated ERM early after their arrival in the lung, and then late in progression, only at the invasive front of larger metastatic lesions. To pursue mechanisms for this regulation, we found that inhibitors of PKC (protein kinase C) blocked phosphorylation of ezrin, and that ezrin coimmunoprecipitated in cells with PKCalpha, PKCiota and PKCgamma. Furthermore, phosphorylated forms of ezrin and PKC had identical expression patterns at the invasive front of pulmonary metastatic lesions in murine and human patient samples. Finally, we showed that the promigratory effects of PKC were linked to ezrin phosphorylation. These data are the first to suggest a dynamic regulation of ezrin phosphorylation during metastasis and to connect the PKC family members with this regulation.

    Oncogene 2009;28;6;792-802

  • Effect of RhoA signaling transduction on expression of Ezrin in breast cancer cell lines.

    Ma L, Liu YP, Zhang XH, Xing LX, Wang JL and Geng CZ

    Department of Pathology, The Fourth Affiliated Hospital, Hebei Medical University, Shijiazhuang, Hebei, PR China.

    Both RhoA and Ezrin are confirmed to play an important role in the development and metastasis of tumors. However, the mechanism remains unclear. This study rudimentally investigates the regulatory effect of RhoA on the expression of Ezrin.

    Methods: After MDA-MB-231 cells were treated with epidermal growth factor (EGF) or following pretreatment of fasudil (the special inhibitor of RhoA), the expression of RhoA, p-RhoA and Ezrin in MDA-MB-231 cells was detected by western blot.

    Results: Stimulation of EGF triggered RhoA phosphorylation in MDA-MB-231 cells which reached the maximum at 30 min; RhoA expression did not change; Ezrin expression was enhanced and reached the maximum at 24 h. However, pretreatment of fasudil before EGF stimulation decreased RhoA phosphorylation and Ezrin expression in MDA-MB-231 cells by 72.73% and 51.28%, respectively.

    Conclusion: RhoA may regulate the invasion and metastasis of breast cancer cells as an upstream signaling of Ezrin.

    Ai zheng = Aizheng = Chinese journal of cancer 2009;28;2;108-11

  • Ezrin interacts with cortactin to form podosomal rosettes in pancreatic cancer cells.

    Kocher HM, Sandle J, Mirza TA, Li NF and Hart IR

    Centre for Tumour Biology, Institute of Cancer and CR-UK Clinical Centre, Barts & The London School of Medicine & Dentistry, John Vane Science Centre, London, UK. hemant.kocher@cancer.org.uk

    Pancreatic cancer is a highly invasive malignancy. Ezrin, a plasma membrane-cytoskeletal linker protein, is associated with the invasive behaviour of cancers. The purpose of this study was to elucidate a possible molecular mechanism for the invasive phenotype.

    Methods: Using a combination of techniques, such as western blotting, co-immunoprecipitation, confocal and light microscopy, invasion and adhesion assays, organotypic cultures and human samples as well as RNA interference (RNAi) and expression of various mutant ezrin constructs, the dynamic molecular nature of podosomes in pancreatic cancer was dissected out.

    Results: Podosome and podosomal rosette formation in pancreatic carcinoma (PaCa3) cells is ezrin dependent and associated with adhesion to fibronectin with subsequent digestion of this substrate. Ezrin binds to increasing amounts of cortactin during formation of the podosomal rosette, with the C-terminal region, specifically the actin-binding domain, mediating this molecular linkage. Further, it is shown that phosphorylation of Tyr353 and Thr567 sites on ezrin (conventionally shown to translocate ezrin to the plasma membrane) is not required for podosome formation. The podosomal rosette is revealed to be a highly dynamic and transient structure, which can metamorphose into other cellular processes, such as filopodia or lamellipodia, and thereby enable epithelial cancer cells to "palpate" the underlying substrate and modify their cytoskeletal behaviour accordingly. In human tumour tissues and organotypic cultures, specific subcellular expression of ezrin (basal membranous; cellular processes invading stroma) in pancreatic cancer cells can be correlated with tumour progression and disease-free survival (log-rank test (Mantel-Cox), p = 0.019).

    Conclusion: Podosomes and their rosettes are driven by ezrin-cortactin interaction and this plays a role in pancreatic cancer invasion.

    Funded by: Department of Health

    Gut 2009;58;2;271-84

  • Properties of an ezrin mutant defective in F-actin binding.

    Saleh HS, Merkel U, Geissler KJ, Sperka T, Sechi A, Breithaupt C and Morrison H

    Leibniz Institute of Age Research, Fritz Lipmann Institute, Beutenbergstrasse 11, 07745 Jena, Germany.

    Ezrin, radixin and moesin are a family of proteins that provide a link between the plasma membrane and the cortical actin cytoskeleton. The regulated targeting of ezrin to the plasma membrane and its association with cortical F-actin are more than likely functions necessary for a number of cellular processes, such as cell adhesion, motility, morphogenesis and cell signalling. The interaction with F-actin was originally mapped to the last 34 residues of ezrin, which correspond to the last three helices (alphaB, alphaC and alphaD) of the C-terminal tail. We set out to identify and mutate the ezrin/F-actin binding site in order to pinpoint the role of F-actin interaction in morphological processes as well as signal transduction. We report here the generation of an ezrin mutant defective in F-actin binding. We identified four actin-binding residues, T576, K577, R579 and I580, that form a contiguous patch on the surface of the last helix, alphaD. Interestingly, mutagenesis of R579 also eliminated the interaction of band four-point one, ezrin, radixin, moesin homology domains (FERM) and the C-terminal tail domain, identifying a hotspot of the FERM/tail interaction. In vivo expression of the ezrin mutant defective in F-actin binding and FERM/tail interaction (R579A) altered the normal cell surface structure dramatically and inhibited cell migration. Further, we showed that ezrin/F-actin binding is required for the receptor tyrosine kinase signal transfer to the Ras/MAP kinase signalling pathway. Taken together, these observations highlight the importance of ezrin/F-actin function in the development of dynamic membrane/actin structures critical for cell shape and motility, as well as signal transduction.

    Journal of molecular biology 2009;385;4;1015-31

  • Ezrin and moesin function together to promote T cell activation.

    Shaffer MH, Dupree RS, Zhu P, Saotome I, Schmidt RF, McClatchey AI, Freedman BD and Burkhardt JK

    Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104, USA.

    The highly homologous proteins ezrin, radixin, and moesin link proteins to the actin cytoskeleton. The two family members expressed in T cells, ezrin and moesin, are implicated in promoting T cell activation and polarity. To elucidate the contributions of ezrin and moesin, we conducted a systematic analysis of their function during T cell activation. In response to TCR engagement, ezrin and moesin were phosphorylated in parallel at the regulatory threonine, and both proteins ultimately localized to the distal pole complex (DPC). However, ezrin exhibited unique behaviors, including tyrosine phosphorylation and transient localization to the immunological synapse before movement to the DPC. To ask whether these differences reflect unique requirements for ezrin vs moesin in T cell signaling, we generated mice with conditional deletion of ezrin in mature T cells. Ezrin-/- T cells exhibited normal immunological synapse organization based upon localization of protein kinase C-theta, talin, and phospho-ZAP70. DPC localization of CD43 and RhoGDP dissociation inhibitor, as well as the novel DPC protein Src homology region 2 domain-containing phosphatase-1, was also unaffected. However, recruitment of three novel DPC proteins, ezrin binding protein of 50 kDa, Csk binding protein, and the p85 subunit of PI3K was partially perturbed. Biochemical analysis of ezrin-/- T cells or T cells suppressed for moesin using small interfering RNA showed intact early TCR signaling, but diminished levels of IL-2. The defects in IL-2 production were more pronounced in T cells deficient for both ezrin and moesin. These cells also exhibited diminished phospholipase C-gamma1 phosphorylation and calcium flux. We conclude that despite their unique movement and phosphorylation patterns, ezrin and moesin function together to promote T cell activation.

    Funded by: NCI NIH HHS: P01 CA093615; NIAID NIH HHS: R01 AI050098, R01 AI060921, R01 AI50098; NICHD NIH HHS: T32 HD007516, T32-HD07516-09; NIGMS NIH HHS: T32 GM007229, T32-GM7229-29

    Journal of immunology (Baltimore, Md. : 1950) 2009;182;2;1021-32

  • Expression of ezrin and metastatic tumor antigen in osteosarcomas of the jaw.

    Park HR, Cabrini RL, Araujo ES, Paparella ML, Brandizzi D and Park YK

    Department of Pathology College of Medicine, Hallym University, Anyang, Korea.

    Ezrin is a membrane-cytoskeleton linker protein involved in regulation of the growth and metastatic behavior of cancer cells. Metastatic tumor antigen (MTA) is a potential metastasis-associated protein. The objective of this study was to evaluate the expression of ezrin and MTA and their correlation with clinicopathological features in osteosarcomas of the jaw.

    Methods: We analyzed ezrin and MTA protein levels by immunohistochemistry in 31 osteosarcomas of the jaw.

    Results: The mean age at diagnosis was 39 years and half of the patients were male. The mandible (n = 19) was more frequently involved than the maxilla (n = 12). The predominant histological type was chondroblastic (58.1%) and 24 patients (77.4%) were classified as having a high grade of malignancy. Immunoreactivity for ezrin was identified in 6 of 31 cases (19.4%), while 77.4% displayed expression of MTA. All ezrin-positive patients had high-grade tumors. The high-grade tumors (n = 24) had a higher rate of MTA expression (42.9% vs 87.5%). Expression of ezrin and MTA was not significantly different according to age, sex, tumor site, histological type, and tumor ploidy. Follow-up information was available for 13 patients, with a mean follow-up time of 26.7 months (range, 6-48 months). At the time of last follow-up, 5 (38.5%) patients had died of disease and 8 patients (61.5%) were alive with no evidence of disease. Expression of ezrin and MTA was not significantly different according to the follow-up data.

    Conclusions: In our study, high-grade tumors had a higher rate of ezrin and MTA expression. This expression pattern indicates that ezrin and MTA positivity can be additional prognostic markers in osteosarcoma of the jaw.

    Tumori 2009;95;1;81-6

  • Ezrin immunohistochemical expression in cartilaginous tumours: a useful tool for differential diagnosis between chondroblastic osteosarcoma and chondrosarcoma.

    Salas S, de Pinieux G, Gomez-Brouchet A, Larrousserie F, Leroy X, Aubert S, Decouvelaere AV, Giorgi R, Fernandez C and Bouvier C

    Service d'Anatomie Pathologique, Hôpital la Timone, Assistance Publique-Hôpitaux de Marseille, 264 rue Saint Pierre, 13385, Marseille cedex 5, France.

    Ezrin is a cytoskeleton linker protein that is actively involved in the metastatic process of cancer cells. We have recently reported that ezrin expression in conventional osteosarcoma was an independent prognostic factor for event-free survival and overall survival. In this work, ezrin expression was found in all histological subtypes. Especially cartilaginous areas in chondroblastic osteosarcomas were immunopositive for ezrin. We wanted to know if ezrin could be a useful diagnostic marker in bone pathology. We have searched for ezrin expression in 208 cartilaginous tumours by immunohistochemistry and in 16 chondroblastic osteosarcomas. All conventional chondrosarcomas, whatever their grade, were negative, while ten of 16 chondroblastic osteosarcomas were positive. In contrast, dedifferentiated (five of 14) and mesenchymal chondrosarcomas (five of ten) showed ezrin positivity. Some chondroblastomas and more rarely chondromyxoid fibromas also exhibited ezrin expression. These data suggest that ezrin is a useful immunohistochemical marker for differential diagnosis between chondroblastic osteosarcomas and conventional chondrosarcomas with a specificity of 100%. Ezrin expression in dedifferentiated and mesenchymal chondrosarcomas which are aggressive neoplasms resistant to conventional treatment means that ezrin could be a therapeutic target. Ezrin expression in chondroblastomas is more intriguing and requires further study to assess prognostic value.

    Virchows Archiv : an international journal of pathology 2009;454;1;81-7

  • Expression of ezrin is associated with invasion and dedifferentiation of hepatitis B related hepatocellular carcinoma.

    Yeh CN, Pang ST, Chen TW, Wu RC, Weng WH and Chen MF

    Department of Surgery, Chang Gung Memorial Hospital; Chang Gung University, Taoyuan, Taiwan, ROC. ycn@adm.cgmh.org.tw

    Background: Hepatocellular carcinoma (HCC) is the fifth most common malignancy in the world and constitutes the leading cause of cancer-related death among men, and second among women in Taiwan. Liver cirrhosis and HCC are relatively prevalent, and 80% to 85% of the patients with these conditions have positive results for hepatitis B surface antigen in Taiwan. Only 5% of the general population is seronegative for all hepatititis B virus (HBV) markers. This is the first study to determine the role of ezrin upon HBV HCC cell and patients with HBV HCC undergoing hepatectomy

    Methods: Immunohistochemical study with ezrin in 104 human HBV-HCC cases were carried out to investigate its association with the clinicopathological features and the outcomes of 104 HBV-HCC patients undergoing hepatetomy. In addition, DNA constructs including the wild type ezrin (wt-ezrin) and mutant ezrin Tyr353 (Y353) were transfected into Hep3B cell to study its role in tumor invasion and differentiation.

    Results: HBV HCC patients with ezrin over-expression independently have smaller tumor size, cirrhotic liver background, poor tumor differentiation, and more vascular invasion. Ezrin expression status has no impact on survival for HBV-HCC patients undergoing hepatectomy. The in vitro assay showed that wt-ezrin Hep3B cells have a significant higher level of AFP secretion and higher invasion ability as compared with the control and Y353- ezrin Hep3B cells.

    Conclusion: Ezrin over-expression contributed to de-differentiation and invasion of HBV-HCC cell. HBV-HCC patients with ezrin over-expression were independently associated with tumor with smaller size, cirrhotic liver background, poor differentiation, and vascular invasion.

    BMC cancer 2009;9;233

  • Intense cytoplasmic ezrin immunoreactivity predicts poor survival in colorectal cancer.

    Elzagheid A, Korkeila E, Bendardaf R, Buhmeida A, Heikkilä S, Vaheri A, Syrjänen K, Pyrhönen S and Carpén O

    Department of Oncology and Radiotherapy, Turku University Hospital, FIN-20521 Turku, Finland. adibel@utu.fi

    Ezrin is a membrane-cytoskeleton anchor, which, in experimental models, regulates tumor cell invasion and metastatic ability. We carried out immunohistochemical analysis of ezrin in 74 advanced colorectal cancer patients and correlated it to clinicopathologic variables and disease outcome. In contrast to the predominantly membraneous immunoreactivity of normal colorectal epithelium, ezrin expression in the colorectal cells was typically cytoplasmic. Altogether, 16.2% (12/74) of the tumors showed negative/weak ezrin staining, 35.1% (26/74) had moderate staining, and 48.6% (36/74) had intense staining. The expression was more intense in colon than in rectal carcinomas (P = .003). Increased ezrin expression was associated with adverse outcome, that is, shorter disease-specific survival; 48.3 months and 36.6 months for negative-weak versus intense expression (P = .041) as well as shorter survival with metastases at 36 months (P = .030); the metastases(36) rates in ezrin(neg/weak), ezrin(moderate), ezrin(intense) are 58.3%, 25.0%, and 18.4%, respectively. In univariate survival analysis, dichotomized (negative/weak versus moderate/strong) ezrin expression significantly predicted both the 5-year disease specific survival (P = .035) and 5-year metastases (P = .018) but lost this predictive power in multivariate (Cox) analysis. High ezrin expression was also related to high E-cadherin (cytoplasmic) expression, DNA aneuploidy, and high thymidylate synthase expression (P = .046, P = .042, P = .046, respectively). These results suggest that ezrin may play a role in colorectal cancer progression and that ezrin expression might provide clinically valuable information in predicting the biological behavior of colorectal cancer.

    Human pathology 2008;39;12;1737-43

  • Rho-ROCK-dependent ezrin-radixin-moesin phosphorylation regulates Fas-mediated apoptosis in Jurkat cells.

    Hébert M, Potin S, Sebbagh M, Bertoglio J, Bréard J and Hamelin J

    Institut National de la Santé et de la Recherche Médicale U749, Faculté de Pharmacie, Châtenay-Malabry, France.

    Upon engagement by its ligand, the Fas receptor (CD95/APO-1) is oligomerized in a manner dependent on F-actin. It has been shown that ezrin, a member of the ERM (ezrin-radixin-moesin) protein family can link Fas to the actin cytoskeleton. We show herein that in Jurkat cells, not only ezrin but also moesin can associate with Fas. The same observation was made in activated human peripheral blood T cells. Fas/ezrin or moesin (E/M) association increases in Jurkat cells following Fas triggering and occurs concomitantly with the formation of SDS- and 2-ME-stable high molecular mass Fas aggregates. Ezrin and moesin have to be present together for the formation of Fas aggregates since down-regulation of either ezrin or moesin expression with small interfering RNAs completely inhibits Fas aggregate formation. Although FADD (Fas-associated death domain protein) and caspase-8 associate with Fas in the absence of E/M, subsequent events such as caspase-8 activation and sensitivity to apoptosis are decreased. During the course of Fas stimulation, ezrin and moesin become phosphorylated, respectively, on T567 and on T558. This phosphorylation is mediated by the kinase ROCK (Rho-associated coiled coil-containing protein kinase) I subsequently to Rho activation. Indeed, inhibition of either Rho or ROCK prevents ezrin and moesin phosphorylation, abrogates the formation of Fas aggregates, and interferes with caspase-8 activation. Thus, phosphorylation of E/M by ROCK is involved in the early steps of apoptotic signaling following Fas triggering and regulates apoptosis induction.

    Journal of immunology (Baltimore, Md. : 1950) 2008;181;9;5963-73

  • MicroRNA-183 regulates Ezrin expression in lung cancer cells.

    Wang G, Mao W and Zheng S

    The 2nd Affiliated Hospital, School of Medicine, College of Life Sciences, Zhejiang University, Hangzhou, China.

    Lung cancer is the leading cause of cancer death. However, the mechanism of lung cancer relapse and metastasis has been poorly elucidated. Recent researches have addressed the role of MicroRNAs (miRNAs) in mediating tumor metastasis. In the present study, we identified microRNA-183 (miR-183) as a potential metastasis-inhibitor. Expression level of miR-183 was reversely correlated with the metastatic potential of lung cancer cells. Furthermore, over-expression of miR-183 inhibited migration and invasion of lung cancer cells. Mechanistically, we identified VIL2-coding-protein Ezrin as a bona fide target of miR-183. We also found that miR-183 could regulate the expression of other genes involved in migration and invasion. Taken together, our findings demonstrated a new role and regulatory mechanism of miR-183 in controlling cancer metastasis.

    FEBS letters 2008;582;25-26;3663-8

  • Characterization of the Ca2+ -regulated ezrin-S100P interaction and its role in tumor cell migration.

    Austermann J, Nazmi AR, Müller-Tidow C and Gerke V

    Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, University of Muenster, 48149 Muenster, Germany.

    Ezrin is a multidomain protein providing regulated membrane-cytoskeleton contacts that play a role in cell differentiation, adhesion, and migration. Within the cytosol of resting cells ezrin resides in an autoinhibited conformation in which the N- and C-terminal ezrin/radixin/moesin (ERM) association domains (ERMADs) interact with one another. Activation of the ezrin membrane-cytoskeleton linker function requires an opening of this interdomain association that can result from phosphatidylinositol 4,5-bisphosphate binding to the N-ERMAD and threonine 567 phosphorylation in the C-ERMAD. We have shown that ezrin can also be activated by Ca(2+)-dependent binding of the EF-hand protein S100P. We now provide a quantitative analysis of this interaction and map the respective binding sites to the F2 lobe in the ezrin N-ERMAD and a stretch of hydrophobic residues in the C-terminal extension of S100P. Phospholipid binding assays reveal that S100P and phosphatidylinositol 4,5-bisphosphate compete to some extent for at least partially overlapping binding sites in N-ERMAD. Using interaction-competent as well as interaction-incompetent S100P derivatives and permanently active ezrin mutants, we also show that the protein interaction and a resulting activation of ezrin promote the transendothelial migration of tumor cells. Thus, a prometastatic role of ezrin and S100P that had been proposed based on their overexpression in highly metastatic cancers is probably due to a direct interaction between the two proteins and the S100P-mediated activation of ezrin.

    The Journal of biological chemistry 2008;283;43;29331-40

  • Pathway-based evaluation of 380 candidate genes and lung cancer susceptibility suggests the importance of the cell cycle pathway.

    Hosgood HD, Menashe I, Shen M, Yeager M, Yuenger J, Rajaraman P, He X, Chatterjee N, Caporaso NE, Zhu Y, Chanock SJ, Zheng T and Lan Q

    Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. hosgoodd@mail.nih.gov

    Common genetic variation may play an important role in altering lung cancer risk. We conducted a pathway-based candidate gene evaluation to identify genetic variations that may be associated with lung cancer in a population-based case-control study in Xuan Wei, China (122 cases and 111 controls). A total of 1260 single-nucleotide polymorphisms (SNPs) in 380 candidate genes for lung cancer were successfully genotyped and assigned to one of 10 pathways based on gene ontology. Logistic regression was used to assess the marginal effect of each SNP on lung cancer susceptibility. The minP test was used to identify statistically significant associations at the gene level. Important pathways were identified using a test of proportions and the rank truncated product methods. The cell cycle pathway was found as the most important pathway (P = 0.044) with four genes significantly associated with lung cancer (PLA2G6 minP = 0.001, CCNA2 minP = 0.006, GSK3 beta minP = 0.007 and EGF minP = 0.013), after adjusting for multiple comparisons. Interestingly, most cell cycle genes that were associated with lung cancer in this analysis were concentrated in the AKT signaling pathway, which is essential for regulation of cell cycle progression and cellular survival, and may be important in lung cancer etiology in Xuan Wei. These results should be viewed as exploratory until they are replicated in a larger study.

    Funded by: Intramural NIH HHS; NCI NIH HHS: TU2 CA105666

    Carcinogenesis 2008;29;10;1938-43

  • Regulation and activation of ezrin protein in endometriosis.

    Ornek T, Fadiel A, Tan O, Naftolin F and Arici A

    Division of Reproductive Endocrinology, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520-8063, USA.

    Background: Ezrin protein and its activated form phospho-ezrin play a role in cell morphology, motility and adhesiveness. In this study, we hypothesized that these proteins play a role in the pathogenesis of endometriosis by promoting adhesion and invasion of endometrial stromal cells (ESCs) in ectopic sites.

    Methods: We compared the expression of ezrin and phospho-ezrin in normal endometrium from women without endometriosis with their expression in eutopic and ectopic endometrial tissues from women with endometriosis, using immunohistochemistry and western blot analysis. Paired eutopic and ectopic endometrial tissue samples from women with endometriosis (n = 13) and normal endometrium from women without endometriosis (n = 12) were collected. Invasive potential of ESCs from each of these samples was compared using Matrigel membrane invasion assay.

    Results: Eutopic and ectopic endometrial tissues from women with endometriosis have higher ezrin and phospho-ezrin levels as confirmed by immunohistochemistry and western blot analysis (P < 0.05). The Matrigel membrane invasion assay revealed that ectopic ESCs have more invasive characteristics, more protrusions and higher ezrin staining than normal ESCs (P < 0.05).

    Conclusions: Ezrin can be a potential marker for endometrial cell invasion and may play a role in the pathogenesis of endometriosis.

    Human reproduction (Oxford, England) 2008;23;9;2104-12

  • A novel juxtamembrane domain in tumor necrosis factor receptor superfamily molecules activates Rac1 and controls neurite growth.

    Ruan W, Lee CT and Desbarats J

    Department of Physiology, McGill University, Montréal, Québec H3G 1Y6, Canada.

    Members of the tumor necrosis factor receptor (TNFR) superfamily control cell fate determination, including cell death and differentiation. Fas (CD95) is the prototypical "death receptor" of the TNFR superfamily and signals apoptosis through well established pathways. In the adult nervous system, Fas induces apoptosis in the context of neuropathology such as stroke or amyotrophic lateral sclerosis. However, during nervous system development, Fas promotes neurite growth and branching. The molecular mechanisms underlying Fas-induced process formation and branching have remained unknown to date. Here, we define the molecular pathway linking Fas to process growth and branching in cell lines and in developing neurons. We describe a new cytoplasmic membrane proximal domain (MPD) that is essential for Fas-induced process growth and that is conserved in members of the TNFR superfamily. We show that the Fas MPD recruits ezrin, a molecule that links transmembrane proteins to the cytoskeleton, and activates the small GTPase Rac1. Deletion of the MPD, but not the death domain, abolished Rac1 activation and process growth. Furthermore, an ezrin-derived inhibitory peptide prevented Fas-induced neurite growth in primary neurons. Our results define a new domain, topologically and functionally distinct from the death domain, which regulates neuritogenesis via recruitment of ezrin and activation of Rac1.

    Molecular biology of the cell 2008;19;8;3192-202

  • Primary hepatic malignant fibrous histiocytoma: clinicopathologic characteristics and prognostic value of ezrin expression.

    Li YR, Akbari E, Tretiakova MS, Hart J, Akbari M, Urbanski SJ and Gao ZH

    Department of Pathology and Laboratory Medicine, University of Calgary and Calgary Laboratory Services, Calgary, Alberta, Canada.

    Primary hepatic malignant fibrous histiocytoma (MFH) is a rare entity with ill-defined clinicopathologic characteristics. We present the largest series to date (7 cases) of primary hepatic MFH, a systematic review of 27 cases published in the English literature, and an analysis of prognostic factors including ezrin expression. The 2 men and 5 women in our series were 34 to 80 years old (average 61 y) and presented with abdominal pain (6/7), systemic symptoms of low-grade fever, malaise, anorexia and weight loss (4/7), and spiking fever (1/7). One case was an incidental finding. Computed tomography and ultrasound revealed a well-demarcated solitary heterogeneous low-density mass ranging from 5.5 to 20 cm (average 12 cm) in largest dimension (5/7), or multiple small nodules up to 2 cm in diameter (1/7) or a 10 cm multiloculated cystic lesion owing to extensive necrosis (1/7). Histologically, a storiform-pleomorphic pattern with variable degrees of necrosis predominated (6/7). A myxoid pattern was seen in only 1 case and this case lacked necrosis. Lymphoplasmacytic infiltration was seen in 3/7 of the cases. Tumors were grade I (1/7), grade II (2/7), grade III (4/7), stage pT1 (4/7), pT2 (1/7), pT4 (1/7), and pT4, cM1 (1/7) at diagnosis. Three patients with tumor cell ezrin immunoreactivity score >or=1 died of tumor within 1 year. Two patients with tumor cell ezrin immunoreactivity score <1 survived >4 years after surgery. Combined analysis of our series and previously reported cases suggest that primary hepatic MFH possess certain characteristic clinicopathologic features that may help in making the diagnosis and in differentiating it from other more common neoplasms in the liver. The prognosis of hepatic MFH depends primarily on tumor size and stage at the time of diagnosis. Ezrin expression in tumor cells can provide additional prognostic information and may be a potential target for new adjuvant therapies.

    The American journal of surgical pathology 2008;32;8;1144-58

  • Ezrin expression is associated with hepatocellular carcinoma possibly derived from progenitor cells and early recurrence after surgical resection.

    Okamura D, Ohtsuka M, Kimura F, Shimizu H, Yoshidome H, Kato A and Miyazaki M

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

    Heterogeneous biological characteristics of hepatocellular carcinoma may be attributed to the cellular origin of the tumor. Patients with hepatocellular carcinoma probably derived from hepatic progenitor cells had early tumor recurrence after surgical resection or liver transplantation, suggesting that these tumors have aggressive characteristics. Ezrin, a member of the ERM (ezrin-radixin-moesin) cytoskeleton-associated protein family, is highly expressed in several types of human cancers and correlations between its immunoreactivity and patient outcome have been shown. In this study, ezrin expression, as well as cytokeratin19 and cytokeratin 7 expression, which are regarded as progenitor cell/ductular markers were immunohistochemically assessed in cases of hepatocellular carcinoma. In normal livers, ezrin expression was not found in any cell types, whereas cytokeratin 7 and cytokeratin 19 were exclusively stained in bile duct cells. In contrast, in livers with chronic hepatitis or cirrhosis, positive ezrin expression was observed in ductular reactions with strong intensity and intermediate hepatobiliary cells with various intensity. Of 77 cases of hepatocellular carcinoma, 28 (36%) had positive ezrin expression, 32 (42%) had cytokeratin 7 expression, and 11 (14%) had cytokeratin 19 expression. Ezrin expression in hepatocellular carcinoma was significantly associated with cytokeratin 19 expression, but not with cytokeratin 7 expression. Patients with ezrin-positive hepatocellular carcinoma had a significantly higher prevalence of elevated serum alpha-fetoprotein. Patients with immunohistochemical ezrin-positive hepatocellular carcinoma demonstrated significantly shorter recurrence-free and overall survival compared to patients with ezrin-negative hepatocellular carcinoma. Multivariate analysis revealed positive ezrin expression and multiple tumors to be independently associated with early recurrence in patients with hepatocellular carcinoma after curative surgical resection. These results suggested that hepatocellular carcinoma with ezrin expression might be at least partly derived from hepatic progenitor cells. Measurement of ezrin expression might be used to identify patients with an increased risk of early recurrence.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2008;21;7;847-55

  • Ezrin, Radixin, and Moesin (ERM) proteins function as pleiotropic regulators of human immunodeficiency virus type 1 infection.

    Kubo Y, Yoshii H, Kamiyama H, Tominaga C, Tanaka Y, Sato H and Yamamoto N

    Department of AIDS Research, Institute of Tropical Medicine, Nagasaki University, Nagasaki, National Institute of Infectious Diseases, Tokyo, Japan. yoshinao@net.nagasaki-u.ac.jp

    Ezrin, radixin, and moesin (ERM) proteins supply functional linkage between integral membrane proteins and cytoskeleton in mammalian cells to regulate membrane protein dynamisms and cytoskeleton rearrangement. To assess potential role of the ERM proteins in HIV-1 lifecycle, we examined if suppression of ERM function in human cells expressing HIV-1 infection receptors influences HIV-1 envelope (Env)-mediated HIV-1-vector transduction and cell-cell fusion. Expression of an ezrin dominant negative mutant or knockdown of ezrin, radixin, or moesin with siRNA uniformly decreased transduction titers of HIV-1 vectors having X4-tropic Env. In contrast, transduction titers of R5-tropic Env HIV-1 vectors were decreased only by radixin knockdown: ezrin knockdown had no detectable effects and moesin knockdown rather increased transduction titer. Each of the ERM suppressions had no detectable effects on cell surface expression of CD4, CCR5, and CXCR4 or VSV-Env-mediated HIV-1 vector transductions. Finally, the individual knockdown of ERM mRNAs uniformly decreased efficiency of cell-cell fusion mediated by X4- or R5-tropic Env and HIV-1 infection receptors. These results suggest that (i) the ERM proteins function as positive regulators of infection by X4-tropic HIV-1, (ii) moesin additionally functions as a negative regulator of R5-tropic HIV-1 virus infection at the early step(s) after the membrane fusion, and (iii) receptor protein dynamisms are regulated differently in R5- and X4-tropic HIV-1 infections.

    Virology 2008;375;1;130-40

  • Ezrin is a key element in the human vagina.

    Fadiel A, Lee HH, Demir N, Richman S, Iwasaki A, Connell K and Naftolin F

    Department of Obstetrics and Gynecology, New York University, 550 First Avenue, TH528, New York, NY 10016, United States.

    Objective: The vagina is a complex tubular structure that has reproductive, support and barrier functions. These depend on the cytoarchitecture of the vaginal cells, which is controlled by key proteins. Cytoskeletal proteins determine cell polarity and membrane specializations by integrating the actin cytoskeleton with cell membranes. This integration is the domain of cytoskeletal proteins including the MERM protein family (moesin-ezrin-radixin-Merlin). Nothing is known about the cyto-localization of the MERM's in the vaginal epithelium or how it influences the cytoarchitecture of the vaginal epithelium and stroma.

    Design: Full-thickness human vaginal fornix samples were obtained from 20 normal human specimens obtained at surgery for pelvic relaxation. Light- and electron microscopical immunohistochemistry (IHC) were used to identify and study activation and cellular localization of immuno-reactive-ezrin (ir-ezrin), a prototypical MERM.

    Results: Ir-ezrin was identified in the stratified squamous vaginal epithelium and connective tissue (fibroblasts, blood vessels and leucocytes). "H" scoring indicated that ir-ezrin staining is denser in the vaginal epithelium than in other layers, that the ir-ezrin staining was associated with increased keratinization and with the size of the tight junctions (p<0.01). Both the amounts and localization of ir-ezrin were associated with high levels of estrogen, identified by the menstrual history and keratinization of the superficial vaginal epithelium. The density of stromal ir-ezrin was increased in the presence of dense epithelial keratinization. Immuno-reactive-ezrin staining was most pronounced near the cell membranes of both keratinized and non-keratinized epithelium, indicating that ezrin activation (unfolding and movement to the membrane) had occurred. Ultra-structural examination of the epithelium showed intra-cellular ir-ezrin to be localized to junctional complexes that have been associated with decreased mucosal penetration by microorganisms. Ir-ezrin was widely distributed throughout stromal fibro-muscular cell, vessels and immunocytes.

    Conclusions: MERM's, represented by ezrin, are widely present in the vaginal wall. This has implications for the strength and resilience of this tubular structure and may be the case in other internal genital tissues. Ezrin's localization and association with cell specializations indicate that in the vagina, as in other tissues, ezrin likely modulates vaginal cell-cell interactions including the changing vaginal cellular interface with the external environment, the regulation of the elasticity of the vagina, and the regulation of microbial and chemical traffic that determine the pH and microbial environment of the vagina. In other work we have shown that ezrin expression is induced by estradiol. The increase of ir-ezrin staining during the appearance of keratinization and maturation of the vaginal cytology indicates that estrogen may regulate vaginal ezrin and thereby the properties of the vaginal wall and epithelium.

    Maturitas 2008;60;1;31-41

  • The Ezrin-radixin-moesin family member ezrin regulates stable microtubule formation and retroviral infection.

    Haedicke J, de Los Santos K, Goff SP and Naghavi MH

    Centre for Research in Infectious Diseases, University College Dublin, Belfield, Dublin 4, Ireland.

    We recently identified the cytoskeletal regulatory protein moesin as a novel gene that inhibits retroviral replication prior to reverse transcription by downregulation of stable microtubule formation. Here, we provide evidence that overexpression of ezrin, another closely related ezrin-radixin-moesin (ERM) family member, also blocks replication of both murine leukemia viruses and human immunodeficiency virus type 1 (HIV-1) in Rat2 fibroblasts before reverse transcription, while knockdown of endogenous ezrin increases the susceptibility of human cells to HIV-1 infection. Together, these results suggest that ERM proteins may be important determinants of retrovirus susceptibility through negative regulation of stable microtubule networks.

    Funded by: Howard Hughes Medical Institute; NCI NIH HHS: R37-CA30488

    Journal of virology 2008;82;9;4665-70

  • Prognostic significance of immunohistochemical expression of ezrin in non-metastatic high-grade osteosarcoma.

    Ferrari S, Zanella L, Alberghini M, Palmerini E, Staals E and Bacchini P

    Chemotherapy Unit, Istituto Ortopedico Rizzoli, Bologna, Italy. stefano.ferrari@ior.it

    Background: Ezrin is a membrane-cytoskeleton linker protein involved in regulating growth and metastatic behaviour of cancer cells. The study evaluated ezrin expression and its prognostic value in patients with non-metastatic osteosarcoma.

    Procedures: Ezrin expression and pattern of staining (cytoplasmic or membraneous and cytoplasmic) were assessed using immunohistochemistry on slides from tumour biopsy. We studied 95 patients (median 16 years, range: 4-39 years) with primary non-metastatic osteosarcoma of the extremity treated by neoadjuvant chemotherapy based on methotrexate, cisplatin, doxorubicin and ifosfamide.

    Results: Seventy-six patients (80%) showed ezrin immunoreactivity: in cytoplasm (37, 47%) and in cytoplasm and membrane (42, 53%) of tumour cells. Immunohistochemical staining score was: 1+ (16, 24%), 2+ (10, 13%), 3+ (17, 21.5%) and 4+ (36, 45.5%). Ezrin and score expression were not related to gender, site, alkaline phosphatase (AP), LDH serum levels, chemotherapy-induced tumour necrosis or patient outcome. A significant association was seen between expression pattern and prognosis. The 3-year probability of disease-free survival was 80% for patients with only cytoplasmic immunostaining and 54% for patients with cytoplasmic and membranous immunostaining (P < 0.02).

    Conclusion: Ezrin immunoreactivity can be detected in the majority of patients with non-metastatic osteosarcoma of the extremity. The pattern of ezrin staining can identify patients with different risks of relapse. In patients who only have ezrin cytoplasmic expression, a probability of EFS >80% at 5 years can be expected. These results suggest further investigations to define the relation between expression pattern, ezrin functional status and outcome in patients with non-metastatic osteosarcoma.

    Pediatric blood & cancer 2008;50;4;752-6

  • Ezrin silencing by small hairpin RNA reverses metastatic behaviors of human breast cancer cells.

    Li Q, Wu M, Wang H, Xu G, Zhu T, Zhang Y, Liu P, Song A, Gang C, Han Z, Zhou J, Meng L, Lu Y, Wang S and Ma D

    Cancer Biology Research Center, Tongji Hospital, Huazhong University of Science and Technology, 1095 Jiefang Anv, Wuhan, Hubei 430030, PR China.

    Ezrin primarily acts as a linker between the plasma membrane and the cytoskeleton and is a key component in tumor metastasis. In the present study, RNA interference (RNAi) using ezrin small hairpin RNAs (ezrin shRNAs) was used to define the roles of ezrin in the regulation of malignant behaviors of human breast cancer. The highly metastatic human breast cancer cell MDA-MB-231, in which ezrin mRNA and protein levels are the highest, was selected as a cell model in vitro. In addition, we also found that ezrin expression was up-regulated and its immuno-staining trans-located from cell membrane to cytoplasm, whereas E-cadherin expression decreased and showed the same cell distribution as ezrin in lymphatic metastases of human breast carcinomas. After repression of ezrin by more than 85% of G3PDH and 75% of beta-actin in mRNA and protein levels was maintained in the stable expressing ezrin shRNAs MDA-MB-231 cell clones, the abilities of cell motility and invasiveness were obviously inhibited with a 4-fold and 2-fold, respectively, and the altered cell polarity was observed. Western blot analyses further revealed that the silencing of ezrin induced an increased E-cadherin expression and a decreased phosphorylation of beta-catenin by inhibiting phosphorylation levels of c-src. These data indicate that ezrin overexpression positively correlated with metastatic potentials of human breast cancer cells, especially lymphatic system metastasis. Decreased ezrin expression by shRNA reversed metastatic behaviors of human breast cancer cells by inducing c-src-mediated E-cadherin expression, suggesting that ezrin may have potential values in assessing lymphatic metastasis of human breast cancers.

    Cancer letters 2008;261;1;55-63

  • Atypical protein kinase C (iota) activates ezrin in the apical domain of intestinal epithelial cells.

    Wald FA, Oriolo AS, Mashukova A, Fregien NL, Langshaw AH and Salas PJ

    Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, FL 33135, USA.

    Atypical protein kinase iota (PKCiota) is a key organizer of the apical domain in epithelial cells. Ezrin is a cytosolic protein that, upon activation by phosphorylation of T567, is localized under the apical membrane where it connects actin filaments to membrane proteins and recruits protein kinase A (PKA). To identify the kinase that phosphorylates ezrin T567 in simple epithelia, we analyzed the expression of active PKC and the appearance of T567-P during enterocyte differentiation in vivo. PKCiota phosphorylated ezrin on T567 in vitro, and in Sf9 cells that do not activate human ezrin. In CACO-2 human intestinal cells in culture, PKCiota co-immunoprecipitated with ezrin and was knocked down by shRNA expression. The resulting phenotype showed a modest decrease in total ezrin, but a steep decrease in T567 phosphorylation. The PKCiota-depleted cells showed fewer and shorter microvilli and redistribution of the PKA regulatory subunit. Expression of a dominant-negative form of PKCiota also decreased T567-P signal, and expression of a constitutively active PKCiota mutant showed depolarized distribution of T567-P. We conclude that, although other molecular mechanisms contribute to ezrin activation, apically localized phosphorylation by PKCiota is essential for the activation and normal distribution of ezrin at the early stages of intestinal epithelial cell differentiation.

    Funded by: NIDDK NIH HHS: R01 DK057805-06, R01 DK076652-02, R01DK057805, R01DK076652

    Journal of cell science 2008;121;Pt 5;644-54

  • Ezrin is a specific and direct target of protein tyrosine phosphatase PRL-3.

    Forte E, Orsatti L, Talamo F, Barbato G, De Francesco R and Tomei L

    IRBM P. Angeletti, via Pontina, Pomezia, Rome, Italy.

    Phosphatase of Regenerating Liver-3 (PRL-3) is a small protein tyrosine phosphatase considered an appealing therapeutic cancer target due to its involvement in metastatic progression. However, despite its importance, the direct molecular targets of PRL-3 action are not yet known. Here we report the identification of Ezrin as a specific and direct cellular substrate of PRL-3. In HCT116 colon cancer cell line, Ezrin was identified among the cellular proteins whose phosphorylation level decreased upon ectopic over-expression of wtPRL-3 but not of catalytically inactive PRL-3 mutants. Although PRL-3 over-expression in HCT116 cells appeared to affect Ezrin phosphorylation status at both tyrosine residues and Thr567, suppression of the endogenous protein by RNA interference pointed to Ezrin-Thr567 as the residue primarily affected by PRL-3 action. In vitro dephosphorylation assays suggested Ezrin-Thr567 as a direct substrate of PRL-3 also proving this enzyme as belonging to the dual specificity phosphatase family. Furthermore, the same effect on levels of pThr567, but not on pTyr residues, was observed in endothelial cells pointing to Ezrin-pThr567 dephosphorylation as a mean through which PRL-3 exerts its function in promoting tumor progression as well as in the establishment of the new vasculature needed for tumor survival and expansion.

    Biochimica et biophysica acta 2008;1783;2;334-44

  • Spatial recruitment and activation of the Fes kinase by ezrin promotes HGF-induced cell scattering.

    Naba A, Reverdy C, Louvard D and Arpin M

    Centre National de la Recherche Scientifique (CNRS), UMR 144, Paris, France.

    The remodeling of epithelial monolayers induced by hepatocyte growth factor (HGF) results in the reorganization of actin cytoskeleton and cellular junctions. We previously showed that the membrane-cytoskeleton linker ezrin plays a major role in HGF-induced morphogenic effects. Here we identified a novel partner of phosphorylated ezrin, the Fes kinase, that acts downstream of ezrin in HGF-mediated cell scattering. We found that Fes interacts directly, through its SH2 domain, with ezrin phosphorylated at tyrosine 477. We show that in epithelial cells, activated Fes localizes either to focal adhesions or cell-cell contacts depending on cell confluency. The recruitment and the activation of Fes to the cell-cell contacts in confluent cells depend on its interaction with ezrin. When this interaction is impaired, Fes remains in focal adhesions and as a consequence the cells show defective spreading and scattering in response to HGF stimulation. Altogether, these results provide a novel mechanism whereby ezrin/Fes interaction at cell-cell contacts plays an essential role in HGF-induced cell scattering and implicates Fes in the cross-talk between cell-cell and cell-matrix adhesion.

    The EMBO journal 2008;27;1;38-50

  • Genes to diseases (G2D) computational method to identify asthma candidate genes.

    Tremblay K, Lemire M, Potvin C, Tremblay A, Hunninghake GM, Raby BA, Hudson TJ, Perez-Iratxeta C, Andrade-Navarro MA and Laprise C

    Department of Medicine, Laval University, Québec, Quebec, Canada.

    Asthma is a complex trait for which different strategies have been used to identify its environmental and genetic predisposing factors. Here, we describe a novel methodological approach to select candidate genes for asthma genetic association studies. In this regard, the Genes to Diseases (G2D) computational tool has been used in combination with a genome-wide scan performed in a sub-sample of the Saguenay-Lac-St-Jean (SLSJ) asthmatic familial collection (n = 609) to identify candidate genes located in two suggestive loci shown to be linked with asthma (6q26) and atopy (10q26.3), and presenting differential parent-of-origin effects. This approach combined gene selection based on the G2D data mining analysis of the bibliographic and protein public databases, or according to the genes already known to be associated with the same or a similar phenotype. Ten genes (LPA, NOX3, SNX9, VIL2, VIP, ADAM8, DOCK1, FANK1, GPR123 and PTPRE) were selected for a subsequent association study performed in a large SLSJ sample (n = 1167) of individuals tested for asthma and atopy related phenotypes. Single nucleotide polymorphisms (n = 91) within the candidate genes were genotyped and analysed using a family-based association test. The results suggest a protective association to allergic asthma for PTPRE rs7081735 in the SLSJ sample (p = 0.000463; corrected p = 0.0478). This association has not been replicated in the Childhood Asthma Management Program (CAMP) cohort. Sequencing of the regions around rs7081735 revealed additional polymorphisms, but additional genotyping did not yield new associations. These results demonstrate that the G2D tool can be useful in the selection of candidate genes located in chromosomal regions linked to a complex trait.

    Funded by: NHLBI NIH HHS: F32 HL083634-02, P01 HL083069, R01 HL 086601, T32 HL07427, U01 HL075419, U01 HL65899

    PloS one 2008;3;8;e2907

  • Localization of the ezrin binding epitope for advanced glycation endproducts.

    McRobert EA, Tikoo A, Cooper ME and Bach LA

    Central and Eastern Clinical School, Department of Medicine, Monash University, AMREP, Alfred Hospital, Commercial Road, Prahran 3181, Victoria, Australia. Anne.McRobert@med.monash.edu.au

    Glycated proteins/advanced glycation endproducts contribute to the development of diabetic complications but the precise pathway from glycated proteins to complications is still being delineated. The ezrin, radixin and moesin protein family is a new class of advanced glycation endproduct-binding protein and we hypothesize that advanced glycation endproducts mediate some of their detrimental effects leading to diabetic complications by inhibiting ezrin's actions. Our previous study revealed that glycated proteins bind to the N-terminal domain of ezrin (aa 1-324) and this study further defines the ezrin binding epitope. Binding of glycated albumin to recombinant N-ezrin deletion constructs (aa 1-280, 1-170 and 1-144) and glutathione-S-transferase-N-ezrin fusion proteins, (aa 200-324 and 270-324) was analysed using ligand and far Western blotting, and surface plasmon resonance. Glycated albumin binding was markedly reduced on removal of amino acids 280-324, while binding was preserved in the fusion proteins. A series of peptides based on residues 280-324 was synthesized and those containing residues 277-299 of ezrin bound maximally. Peptide binding to glycated albumin was glycation-specific. An ezrin peptide (aa 277-299) dose-dependently reversed the inhibitory effect of glycated albumin on ezrin (1-324) phosphorylation in vitro, suggesting that binding of advanced glycation endproducts to ezrin changes the conformation of the latter sufficiently to alter binding interactions distant from the advanced glycation endproduct-binding site. This may have consequences for subcellular ezrin localization and signalling pathways. Altogether, these studies provide important structural knowledge for developing peptide antagonists that may be therapeutically useful in preventing advanced glycation endproduct:ezrin interactions in diabetes.

    The international journal of biochemistry & cell biology 2008;40;8;1570-80

  • Ezrin and alpha-smooth muscle actin are immunohistochemical prognostic markers in conventional osteosarcomas.

    Salas S, Bartoli C, Deville JL, Gaudart J, Fina F, Calisti A, Bollini G, Curvale G, Gentet JC, Duffaud F, Figarella-Branger D and Bouvier C

    Service d'Oncologie Médicale Adulte CHU Timone, APHM, Marseilles, France.

    Ezrin is a cytoskeleton linker protein that is actively involved in the metastatic process of cancer cells. We have searched for a prognostic value of ezrin and some of its partners: alpha-smooth muscle actin and CD44H in 37 patients with an osteosarcoma. Automate immunohistochemistry (IHC) with anti-ezrin, alpha-smooth muscle actin and CD44H antibodies was performed in 66 specimens: 37 biopsies before chemotherapy, 16 resected tumours of "poor" responders and 13 metastases. The messenger RNA (mRNA) levels of ezrin of 13 frozen biopsies and 4 metastases were evaluated by real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR). All results were correlated to the following clinical data. Ezrin expression by IHC was found in 62% of 37 biopsies in the different histological subtypes. A good correlation was found between positive or negative samples by IHC and mRNA levels. Ezrin expression was recorded in 84.5% of metastastic samples. The mean expression of ezrin was higher in metastases than biopsies (p = 0.024). In multivariate analysis, ezrin was an independent prognostic marker for event-free survival and overall survival (OS) with p < 0.001 and p = 0.003, respectively, and alpha-smooth muscle actin for OS only (p = 0.024). Our findings suggest that ezrin and alpha-smooth muscle actin are predictive IHC prognostic markers for patients with an osteosarcoma.

    Virchows Archiv : an international journal of pathology 2007;451;6;999-1007

  • Interaction of ezrin with the novel guanine nucleotide exchange factor PLEKHG6 promotes RhoG-dependent apical cytoskeleton rearrangements in epithelial cells.

    D'Angelo R, Aresta S, Blangy A, Del Maestro L, Louvard D and Arpin M

    Centre National de la Recherche Scientifique, Unité Mixte de Recherche 144, Paris 75248, France.

    The mechanisms underlying functional interactions between ERM (ezrin, radixin, moesin) proteins and Rho GTPases are not well understood. Here we characterized the interaction between ezrin and a novel Rho guanine nucleotide exchange factor, PLEKHG6. We show that ezrin recruits PLEKHG6 to the apical pole of epithelial cells where PLEKHG6 induces the formation of microvilli and membrane ruffles. These morphological changes are inhibited by dominant negative forms of RhoG. Indeed, we found that PLEKHG6 activates RhoG and to a much lesser extent Rac1. In addition we show that ezrin forms a complex with PLEKHG6 and RhoG. Furthermore, we detected a ternary complex between ezrin, PLEKHG6, and the RhoG effector ELMO. We demonstrate that PLEKHG6 and ezrin are both required in macropinocytosis. After down-regulation of either PLEKHG6 or ezrin expression, we observed an inhibition of dextran uptake in EGF-stimulated A431 cells. Altogether, our data indicate that ezrin allows the local activation of RhoG at the apical pole of epithelial cells by recruiting upstream and downstream regulators of RhoG and that both PLEKHG6 and ezrin are required for efficient macropinocytosis.

    Molecular biology of the cell 2007;18;12;4780-93

  • The CD44 standard/ezrin complex regulates Fas-mediated apoptosis in Jurkat cells.

    Mielgo A, Brondani V, Landmann L, Glaser-Ruhm A, Erb P, Stupack D and Günthert U

    Institute of Medical Microbiology, Department of Clinical and Biological Sciences, University of Basel, Petersplatz 10, 4003 Basel, Switzerland.

    The transmembrane receptor CD44 conveys important signals from the extracellular microenvironment to the cytoplasm, a phenomena known as "outside-in" signaling. CD44 exists as several isoforms that result from alternative splicing, which differ only in the extracellular domain but yet exhibit different activities. CD44 is a binding partner for the membrane-cytoskeleton cross-linker protein ezrin. In this study, we demonstrate that only CD44 standard (CD44s) colocalizes and interacts with the actin cross-linkers ezrin and moesin using well-characterized cell lines engineered to express different CD44 isoforms. Importantly, we also show that the association CD44s-ezrin-actin is an important modulator of Fas-mediated apoptosis. The results highlight a mechanism by which signals from the extracellular milieu regulate intracellular signaling activities involved in programmed cell death.

    Apoptosis : an international journal on programmed cell death 2007;12;11;2051-61

  • Inhibition of T cell activation by cyclic adenosine 5'-monophosphate requires lipid raft targeting of protein kinase A type I by the A-kinase anchoring protein ezrin.

    Ruppelt A, Mosenden R, Grönholm M, Aandahl EM, Tobin D, Carlson CR, Abrahamsen H, Herberg FW, Carpén O and Taskén K

    The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.

    cAMP negatively regulates T cell immune responses by activation of type I protein kinase A (PKA), which in turn phosphorylates and activates C-terminal Src kinase (Csk) in T cell lipid rafts. Using yeast two-hybrid screening, far-Western blot, immunoprecipitation and immunofluorescense analyses, and small interfering RNA-mediated knockdown, we identified Ezrin as the A-kinase anchoring protein that targets PKA type I to lipid rafts. Furthermore, Ezrin brings PKA in proximity to its downstream substrate Csk in lipid rafts by forming a multiprotein complex consisting of PKA/Ezrin/Ezrin-binding protein 50, Csk, and Csk-binding protein/phosphoprotein associated with glycosphingolipid-enriched microdomains. The complex is initially present in immunological synapses when T cells contact APCs and subsequently exits to the distal pole. Introduction of an anchoring disruptor peptide (Ht31) into T cells competes with Ezrin binding to PKA and thereby releases the cAMP/PKA type I-mediated inhibition of T cell proliferation. Finally, small interfering RNA-mediated knockdown of Ezrin abrogates cAMP regulation of IL-2. We propose that Ezrin is essential in the assembly of the cAMP-mediated regulatory pathway that modulates T cell immune responses.

    Journal of immunology (Baltimore, Md. : 1950) 2007;179;8;5159-68

  • Ezrin and radixin both regulate the apical membrane localization of ABCC2 (MRP2) in human intestinal epithelial Caco-2 cells.

    Yang Q, Onuki R, Nakai C and Sugiyama Y

    School of Pharmacy, Fudan University, Yixueyuan Road 138, Shanghai, China.

    Multidrug resistance-associated protein ABCC2 (MRP2) is widely expressed in mammalian tissues including intestine, liver and kidney, and it has been shown to be located exclusively on the apical membrane of polarized cells. Recently, several reports suggest that apical membrane localization of ABCC2 (Mrp2) was regulated by radixin in rodent liver. To investigate the mechanism underlying this apical membrane targeting of MRP2 in human intestine, we chose Caco-2 cells as a model to examine the unique roles of ezrin and radixin. Following immunostaining, radixin and ezrin were found to be concentrated at the apical membrane of Caco-2 cells. Using the RNAi method, radixin and ezrin stable knockdown Caco-2 cells were constructed. A cell surface biotinylation experiment with radixin or ezrin stable knockdown Caco-2 cells showed that radixin or ezrin deficiency caused the loss of ABCC2 (MRP2) from the cell surface. An immunoprecipitation assay showed that radixin and ezrin were associated with ABCC2 (MRP2). These findings indicate that both ezrin and radixin are independently required for the apical membrane localization of ABCC2 (MRP2) in Caco-2 cells. Radixin and ezrin play similar roles in the apical membrane localization of ABCC2 (MRP2) and their expression level and subcellular distribution are important factors in the regulation of ABCC2 (MRP2) at the post-transcriptional level.

    Experimental cell research 2007;313;16;3517-25

  • Akt phosphorylation regulates the tumour-suppressor merlin through ubiquitination and degradation.

    Tang X, Jang SW, Wang X, Liu Z, Bahr SM, Sun SY, Brat D, Gutmann DH and Ye K

    Department of Pathology and Laboratory Medicine, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322, USA.

    The neurofibromatosis-2 (NF2) tumour-suppressor gene encodes an intracellular membrane-associated protein, called merlin, whose growth-suppressive function is dependent on its ability to form interactions through its intramolecular amino-terminal domain (NTD) and carboxy-terminal domain (CTD). Merlin phosphorylation plays a critical part in dictating merlin NTD/CTD interactions as well as in controlling binding to its effector proteins. Merlin is partially regulated by phosphorylation of Ser 518, such that hyperphosphorylated merlin is inactive and fails to form productive intramolecular and intermolecular interactions. Here, we show that the protein kinase Akt directly binds to and phosphorylates merlin on residues Thr 230 and Ser 315, which abolishes merlin NTD/CTD interactions and binding to merlin's effector protein PIKE-L and other binding partners. Furthermore, Akt-mediated phosphorylation leads to merlin degradation by ubiquitination. These studies demonstrate that Akt-mediated merlin phosphorylation regulates the function of merlin in the absence of an inactivating mutation.

    Funded by: NCI NIH HHS: R01 (CA117872)

    Nature cell biology 2007;9;10;1199-207

  • [Expression of ezrin and CD44-v6 in human esophageal squamous cell carcinoma and its clinical significance].

    Chai LX, Sun KL, Guo LP, Zhang HT and Lu SX

    Department of Thoracic Surgery, Shanxi Provincial People's Hospital, Taiyuan 030012, China.

    Objective: To evaluate the expression of ezrin and CD44-v6 in esophageal squamous cell carcinoma, and to evaluate its relationship with lymph node metastasis (LNM) and histological grading.

    Methods: The expression of ezrin and CD44-v6 in 71 patients with esophageal squamous cell carcinoma was studied using immunohistochemical (SP) method. The correlation of their expression with relevant clinical data was statistically analyzed.

    Results: In normal esophageal squamous epithelia, the expression of ezrin was found in 33 cases among 71 cases and the expression of CD44-v6 in 18 cases among 71 cases. In esophageal squamous cell carcinoma, the expression of ezrin was found in 64 cases among 71 cases and CD44-v6 in 58 cases among 71 cases. The expression of ezrin was closely related to LNM. The positive rate of ezrin expression in LNM cases was significantly higher than that in cases without LNM. The expression of CD44-v6 had a close relation to tumor differentiation and LNM. The positive rate of CD44-v6 expression in LNM cases was significantly higher than that in patients without LNM. The expression of ezrin in CD44-v6 positive cases was significantly higher than that of CD44-v6 negative cases. The LNM rate was 60.0% in 48 patients with positive expression of both ezrin and CD44-v6, while none of lymph node metastasis was found in the 6 patients with both negative.

    Conclusion: The test of CD44-v6 and ezrin expression may have significant prognostic value for assessing the degree of malignancy and potential LNM probability of ESCC. Ezrin may become a new target in evaluation of tumor prognosis.

    Zhonghua zhong liu za zhi [Chinese journal of oncology] 2007;29;9;685-8

  • Activated ezrin promotes cell migration through recruitment of the GEF Dbl to lipid rafts and preferential downstream activation of Cdc42.

    Prag S, Parsons M, Keppler MD, Ameer-Beg SM, Barber P, Hunt J, Beavil AJ, Calvert R, Arpin M, Vojnovic B and Ng T

    Richard Dimbleby Department of Cancer Research, King's College London, Guy's Medical School Campus, London SE1 1UL, United Kingdom. sprag@fm.ul.pt

    Establishment of polarized cell morphology is a critical factor for migration and requires precise spatial and temporal activation of the Rho GTPases. Here, we describe a novel role of the actin-binding ezrin/radixin/moesin (ERM)-protein ezrin to be involved in recruiting Cdc42, but not Rac1, to lipid raft microdomains, as well as the subsequent activation of this Rho GTPase and the downstream effector p21-activated kinase (PAK)1, as shown by fluorescence lifetime imaging microscopy. The establishment of a leading plasma membrane and the polarized morphology necessary for random migration are also dependent on ERM function and Cdc42 in motile breast carcinoma cells. Mechanistically, we show that the recruitment of the ERM-interacting Rho/Cdc42-specific guanine nucleotide exchange factor Dbl to the plasma membrane and to lipid raft microdomains requires the phosphorylated, active conformer of ezrin, which serves to tether the plasma membrane or its subdomains to the cytoskeleton. Together these data suggest a mechanism whereby precise spatial guanine nucleotide exchange of Cdc42 by Dbl is dependent on functional ERM proteins and is important for directional cell migration.

    Molecular biology of the cell 2007;18;8;2935-48

  • Association of ezrin expression in intestinal and diffuse gastric carcinoma with clinicopathological parameters and tumor type.

    Bal N, Yildirim S, Nursal TZ, Bolat F and Kayaselcuk F

    Baskent University, Adana Research and Medical Center, Pathology Department, Yuregir, Adana 01250, Turkey.

    Aim: To investigate the correlation between ezrin expression and types of gastric carcinoma and clinico-pathological variables.

    Methods: We examined ezrin protein expression in 75 gastric carcinoma (53 intestinal types of adenocarcinoma, 22 diffuse types of carcinoma) tissues by immunohistochemistry. The results were compared with clinicopathological parameters such as tumor type, grade of tumor, clinical stage, presence of metastatic lymph node, and depth of invasion.

    Results: Ezrin immunostaining was positive in 43 cases (81.1%) of intestinal type and in 9 (40.9%) cases of diffuse type adenocarcinomas (P < 0.001). In gastric carcinomas, the expression of ezrin protein correlated with the status of H pylori and survival. There was no correlation between expression of ezrin with TNM stage and histological grade of gastric carcinomas (P > 0.05).

    Conclusion: The low expression of ezrin implicates the loss of adhesion in diffuse carcinomas. Furthermore, overexpression of ezrin in carcinomas with H pylori infection may be a genuine specific pathway in which H pylori may cause/initiate gastric carcinoma.

    World journal of gastroenterology 2007;13;27;3726-9

  • Podocalyxin increases the aggressive phenotype of breast and prostate cancer cells in vitro through its interaction with ezrin.

    Sizemore S, Cicek M, Sizemore N, Ng KP and Casey G

    Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA.

    Podocalyxin is an anti-adhesive transmembrane sialomucin that has been implicated in the development of more aggressive forms of breast and prostate cancer. The mechanism through which podocalyxin increases cancer aggressiveness remains poorly understood but may involve the interaction of podocalyxin with ezrin, an established mediator of metastasis. Here, we show that overexpression of podocalyxin in MCF7 breast cancer and PC3 prostate cancer cell lines increased their in vitro invasive and migratory potential and led to increased expression of matrix metalloproteases 1 and 9 (MMP1 and MMP9). Podocalyxin expression also led to an increase in mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) activity. To determine the role of ezrin in these podocalyxin-dependent phenotypic events, we first confirmed that podocalyxin formed a complex with ezrin in MCF7 and PC3 cells. Furthermore, expression of podocalyxin was associated with a changed ezrin subcellular localization and increased ezrin phosphorylation. Transient knockdown of ezrin protein abrogated MAPK and PI3K signaling as well as MMP expression and invasiveness in cancer cells overexpressing podocalyxin. These findings suggest that podocalyxin leads to increased in vitro migration and invasion, increased MMP expression, and increased activation of MAPK and PI3K activity in MCF7 and PC3 cells through its ability to form a complex with ezrin.

    Funded by: NCI NIH HHS: CA88164, CA98683

    Cancer research 2007;67;13;6183-91

  • The cytoskeletal proteins alpha-actinin, Ezrin, and talin are De-expressed in endometriosis and endometrioid carcinoma compared with normal uterine epithelium.

    Slater M, Cooper M and Murphy CR

    Department of Anatomy and Histology, School of Biomedical Sciences, The University of Sydney, NSW, Australia. michaels@anatomy.usyd.edu.au

    In this retrospective study on banked tissue, we found that alpha-actinin and talin were completely de-expressed in both endometriosis and endometrioid carcinoma tissue. Some patchy, depolarized labeling for ezrin was noted in the endometrioid carcinoma but not in endometriosis. The loss of these proteins in both endometriosis and endometrioid carcinoma tissue indicates a significant change in the integrity of these tissues compared with normal and the possibility that individual cells may break away from the parent histology due to loss of cell adhesion. It also indicates a similarity between endometrioid cancer and endometriosis with respect to epithelial cell function and adhesion.

    Applied immunohistochemistry & molecular morphology : AIMM 2007;15;2;170-4

  • Phosphorylated ERM is responsible for increased T cell polarization, adhesion, and migration in patients with systemic lupus erythematosus.

    Li Y, Harada T, Juang YT, Kyttaris VC, Wang Y, Zidanic M, Tung K and Tsokos GC

    Department of Cellular Injury, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.

    Systemic lupus erythematosus (SLE) is an autoimmune/inflammatory disease characterized by autoantibody production and abnormal T cells that infiltrate tissues through not well-known mechanisms. We report that SLE T lymphocytes display increased levels of CD44, ezrin, radixin, and moesin (ERM) phosphorylation, stronger actin polymerization, higher polar cap formation, and enhanced adhesion and chemotactic migration compared with T cells from patients with rheumatoid arthritis and normal individuals. Silencing of CD44 by CD44 small interfering RNA in SLE T cells inhibited significantly their ability to adhere and migrate as did treatment with Rho kinase and actin polymerization inhibitors. Forced expression of T567D-ezrin, a phosphorylation-mimic form, enhanced remarkably the adhesion and migration rate of normal T cells. Anti-CD3/TCR autoantibodies present in SLE sera caused increased ERM phosphorylation, adhesion, and migration in normal T cells. pERM and CD44 are highly expressed in T cells infiltrating in the kidneys of patients with lupus nephritis. These data prove that increased ERM phosphorylation represents a key molecular abnormality that guides T cell adhesion and migration in SLE patients.

    Funded by: NIAID NIH HHS: R01 AI42269, R01 AI49954

    Journal of immunology (Baltimore, Md. : 1950) 2007;178;3;1938-47

  • Palmitoylation is required for efficient Fas cell death signaling.

    Chakrabandhu K, Hérincs Z, Huault S, Dost B, Peng L, Conchonaud F, Marguet D, He HT and Hueber AO

    Equipe labelisée La Ligue, Institute of Signaling, Developmental Biology and Cancer Research, CNRS UMR 6543, Nice, France.

    Localization of the death receptor Fas to specialized membrane microdomains is crucial to Fas-mediated cell death signaling. Here, we report that the post-translational modification of Fas by palmitoylation at the membrane proximal cysteine residue in the cytoplasmic region is the targeting signal for Fas localization to lipid rafts, as demonstrated in both cell-free and living cell systems. Palmitoylation is required for the redistribution of Fas to actin cytoskeleton-linked rafts upon Fas stimulation and for the raft-dependent, ezrin-mediated cytoskeleton association, which is necessary for the efficient Fas receptor internalization, death-inducing signaling complex assembly and subsequent caspase cascade leading to cell death.

    The EMBO journal 2007;26;1;209-20

  • Gene expression in temporal lobe epilepsy is consistent with increased release of glutamate by astrocytes.

    Lee TS, Mane S, Eid T, Zhao H, Lin A, Guan Z, Kim JH, Schweitzer J, King-Stevens D, Weber P, Spencer SS, Spencer DD and de Lanerolle NC

    Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520-8082, USA.

    Patients with temporal lobe epilepsy (TLE) often have a shrunken hippocampus that is known to be the location in which seizures originate. The role of the sclerotic hippocampus in the causation and maintenance of seizures in temporal lobe epilepsy (TLE) has remained incompletely understood despite extensive neuropathological investigations of this substrate. To gain new insights and develop new testable hypotheses on the role of sclerosis in the pathophysiology of TLE, the differential gene expression profile was studied. To this end, DNA microarray analysis was used to compare gene expression profiles in sclerotic and non-sclerotic hippocampi surgically removed from TLE patients. Sclerotic hippocampi had transcriptional signatures that were different from non-sclerotic hippocampi. The differentially expressed gene set in sclerotic hippocampi revealed changes in several molecular signaling pathways, which included the increased expression of genes associated with astrocyte structure (glial fibrillary acidic protein, ezrin-moesin-radixin, palladin), calcium regulation (S100 calcium binding protein beta, chemokine (C-X-C motif) receptor 4) and blood-brain barrier function (Aquaaporin 4, Chemokine (C-C- motif) ligand 2, Chemokine (C-C- motif) ligand 3, Plectin 1, intermediate filament binding protein 55kDa) and inflammatory responses. Immunohistochemical localization studies show that there is altered distribution of the gene-associated proteins in astrocytes from sclerotic foci compared with non-sclerotic foci. It is hypothesized that the astrocytes in sclerotic tissue have activated molecular pathways that could lead to enhanced release of glutamate by these cells. Such glutamate release may excite surrounding neurons and elicit seizure activity.

    Funded by: NINDS NIH HHS: R21 NS48434, R21 NS048434

    Molecular medicine (Cambridge, Mass.) 2007;13;1-2;1-13

  • Pseudomonas aeruginosa ExoS ADP-ribosyltransferase inhibits ERM phosphorylation.

    Maresso AW, Deng Q, Pereckas MS, Wakim BT and Barbieri JT

    Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.

    Pseudomonas aeruginosa causes life-threatening infections in compromised and cystic fibrosis patients. Pathogenesis stems from a number of virulence factors, including four type III translocated cytotoxins: ExoS, ExoT, ExoY and ExoU. ExoS is a bifunctional toxin: the N terminus (amino acids 96-219) encodes a Rho GTPase Activating Protein (GAP) domain. The C terminus (amino acids 234-453) encodes a 14-3-3-dependent ADP-ribosyltransferase domain which transfers ADP-ribose from NAD onto substrates such as the Ras GTPases and vimentin. Ezrin/radixin/moesin (ERM) proteins have recently been identified as high-affinity substrates for ADP-ribosylation by ExoS. Expression of ExoS in HeLa cells led to a loss of phosphorylation of ERM proteins that was dependent upon the expression of ADP-ribosyltransferase activity. MALDI-MS and site-directed mutagenesis studies determined that ExoS ADP-ribosylated moesin at three C-terminal arginines (Arg553, Arg560 and Arg563), which cluster Thr558, the site of phosphorylation by protein kinase C and Rho kinase. ADP-ribosylated-moesin was a poor target for phosphorylation by protein kinase C and Rho kinase, which showed that ADP-ribosylation directly inhibited ERM phosphorylation. Expression of dominant active-moesin inhibited cell rounding elicited by ExoS, indicating that moesin is a physiological target in cultured cells. This is the first demonstration that a bacterial toxin inhibits the phosphorylation of a mammalian protein through ADP-ribosylation. These data explain how the expression of the ADP-ribosylation of ExoS modifies the actin cytoskeleton and indicate that ExoS possesses redundant enzymatic activities to depolymerize the actin cytoskeleton.

    Funded by: NHLBI NIH HHS: HL68912; NIAID NIH HHS: AI30162

    Cellular microbiology 2007;9;1;97-105

  • Expression of the cytoskeleton linker protein ezrin in human cancers.

    Bruce B, Khanna G, Ren L, Landberg G, Jirström K, Powell C, Borczuk A, Keller ET, Wojno KJ, Meltzer P, Baird K, McClatchey A, Bretscher A, Hewitt SM and Khanna C

    Tumor and Metastasis Biology Section, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.

    Expression of the metastasis-associated protein, ezrin, in over 5,000 human cancers and normal tissues was analyzed using tissue microarray immunohistochemistry. Ezrin staining was compared between cancers and their corresponding normal tissues, between cancers of epithelial and mesenchymal origin, in the context of the putative inhibitor protein, merlin, and against clinicopathological data available for breast, lung, prostate cancers and sarcomas. Ezrin was found in most cancers and normal tissues at varying levels of intensity. In general ezrin was expressed at higher levels in sarcomas than in carcinomas. By normalizing the expression of ezrin in each cancer using ezrin expression found in the corresponding normal tissue, significant associations between ezrin were found in advancing histological grade in sarcomas (P = 0.02) and poor outcome in breast cancer (P = 0.025). Clinicopathologic associations were not changed by simultaneous assessment of ezrin and merlin in each patient sample for the cancer types examined. These data support a role for ezrin in the biology of human cancers and the need for additional studies in breast cancer and sarcoma patients that may validate ezrin as a marker of cancer progression and as a potential target for cancer therapy.

    Funded by: NCI NIH HHS: 1P50 CA69568, P01 CA093900

    Clinical & experimental metastasis 2007;24;2;69-78

  • Large-scale mapping of human protein-protein interactions by mass spectrometry.

    Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T and Figeys D

    Protana, Toronto, Ontario, Canada.

    Mapping protein-protein interactions is an invaluable tool for understanding protein function. Here, we report the first large-scale study of protein-protein interactions in human cells using a mass spectrometry-based approach. The study maps protein interactions for 338 bait proteins that were selected based on known or suspected disease and functional associations. Large-scale immunoprecipitation of Flag-tagged versions of these proteins followed by LC-ESI-MS/MS analysis resulted in the identification of 24,540 potential protein interactions. False positives and redundant hits were filtered out using empirical criteria and a calculated interaction confidence score, producing a data set of 6463 interactions between 2235 distinct proteins. This data set was further cross-validated using previously published and predicted human protein interactions. In-depth mining of the data set shows that it represents a valuable source of novel protein-protein interactions with relevance to human diseases. In addition, via our preliminary analysis, we report many novel protein interactions and pathway associations.

    Molecular systems biology 2007;3;89

  • Parathyroid hormone-related protein and ezrin are up-regulated in human lung cancer bone metastases.

    Deng X, Tannehill-Gregg SH, Nadella MV, He G, Levine A, Cao Y and Rosol TJ

    Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.

    Lung cancer often metastasizes to bone in patients with advanced disease. Identification of the factors involved in the interactions between lung cancer cells and bone will improve the prevention and treatment of bone metastases. We identified changes in metastasis-related gene expression of human HARA lung squamous carcinoma cells co-cultured with neonatal mouse calvariae using a pathway-specific microarray analysis. Nine genes were up-regulated and two genes down-regulated in HARA cells co-cultured with mouse calvariae. Five of the nine up-regulated genes, including caveolin 1, CD44, EphB2, ezrin, and Parathyroid hormone-related protein (PTHrP), and one down-regulated gene, SLPI, were further confirmed by Reverse transcription-polymerase chain reaction (RT-PCR). A mouse model was subsequently used to study the role of PTHrP and ezrin in bone metastasis in vivo. PTHrP (all three isoforms) and ezrin were up-regulated in HARA cells at sites of bone metastasis as detected by RT-PCR and immunohistochemistry. The PTHrP 141 mRNA isoform was increased by the greatest extent (13.9-fold) in bone metastases compared to PTHrP 139 and PTHrP 173 mRNA. We then generated a HARA cell line in which PTHrP expression was inducibly silenced by RNA interference. Silencing of PTHrP expression caused significant reduction of submembranous F-actin and decreased HARA cell invasion. Ezrin up-regulation was confirmed by Western blots on HARA cells co-cultured with adult mouse long bones. Further, Transforming growth factor beta (TGF-beta) was identified as one of the factors in the bone microenvironment that was responsible for the up-regulation of ezrin. The identification of PTHrP and ezrin as important regulators of lung cancer bone metastasis offers new mechanistic insights into the metastasis of lung cancer and provides potential targets for the prevention and treatment of lung cancer metastasis.

    Funded by: NCI NIH HHS: P01 CA100730, R01 CA 77911; NCRR NIH HHS: K26 RR00168

    Clinical & experimental metastasis 2007;24;2;107-19

  • Prognostic significance of E-cadherin and ezrin immunohistochemical expression in prostate cancer.

    Musiał J, Sporny S and Nowicki A

    Department of Pathology, Medical University of Lódź. j-proteus@wp.pl

    Objective: Abnormal expression of molecules connected with cell to cell adhesion, such as E-cadherin or ezrin, can be contributing factors for increased invasiveness and metastatic potential of cancer. We investigated E-cadherin and ezrin immunoreactivity in prostate carcinomas, and its relation with clinical parameters and patient outcome.

    Methods: E-cadherin and ezrin expression was examined by immunohistochemistical analysis of bioptate tissues from patients with prostate cancer. Normal appearing prostate epithelium was used as an internal control for each specimen. The relation between E-cadherin and ezrin staining, and other clinicopathological features (e.g. patient survival) were analyzed using Kaplan-Meier and Cox regression methods.

    Results: In moderate differentiated to poorly differentiated tumors (Gleason scores 5-10), we observed a trend of increasing percentage of tumors with aberrant staining for E-cadherin (P < 0.001 by Chi2 for linear trend). A significant inverse correlation between ezrin expression and tumor differentiation was also found (P < 0.002 by Chi Chi2 for linear trend). The survival time of patients with aberrant staining of ezrin and E-cadherin was significantly shorter than that of patients with a normal staining pattern but in Cox multivariate survival analysis, only E-cadherin immunoreactivity had independent effect on survival (P = 0.03), when controlling for the other clinicopathological factors.

    Conclusions: The aberrant or decreased expression of E-cadherin seems to be one of most promising markers of poor prognosis in localized prostate cancer. Our study also supports a role of ezrin in progression in human prostate cancers but additional studies are mandatory to provide further evidence for an important role of ezrin in prostate tumors progression.

    Polish journal of pathology : official journal of the Polish Society of Pathologists 2007;58;4;235-43

  • Androgen induction of prostate cancer cell invasion is mediated by ezrin.

    Chuan YC, Pang ST, Cedazo-Minguez A, Norstedt G, Pousette A and Flores-Morales A

    Department of Molecular Medicine and Surgery, Section of Experimental Geriatrics, Karolinska Institute, Neurotec, Stockholm, Sweden.

    Ezrin is a key signaling molecule that regulates cell survival, adhesion migration, and invasion. We have previously shown that ezrin is regulated by androgen in rat prostate and that its expression is increased in prostate cancer and in prostate intraepithelial neoplasia. We have used the androgen-sensitive cell line LNCaP-FGC to investigate the role of ezrin in androgen-induced cell invasion. We found that androgen treatment of LNCaP-FGC cells induces ezrin expression, an effect that is inhibited by the androgen receptor antagonist, bicalutamide. In addition, androgen treatment induces the phosphorylation of ezrin in Thr-567 and Tyr-353 in a sequential manner. This is mediated through protein kinase C alpha and Src tyrosine kinase, respectively. Androgen treatment induces the translocation of both protein kinase C alpha and ezrin to the cell membrane and their association. Inhibition of ezrin function using short interference RNA or the overexpression of T567A and Y353F-ezrin mutants significantly reduces androgen-induced Matrigel invasion but does not affect cell proliferation or cell adhesion. Matrigel invasion of the androgen-insensitive prostate cancer cell lines PC-3 and LNCaP-R is also dependent on ezrin. In summary, we have shown that androgens regulate ezrin at transcriptional and posttranscriptional levels. Hormonal regulation of ezrin phosphorylation is required for androgen-induced cell invasion.

    The Journal of biological chemistry 2006;281;40;29938-48

  • Proteomic identification and functional characterization of a novel ARF6 GTPase-activating protein, ACAP4.

    Fang Z, Miao Y, Ding X, Deng H, Liu S, Wang F, Zhou R, Watson C, Fu C, Hu Q, Lillard JW, Powell M, Chen Y, Forte JG and Yao X

    Laboratory of Cellular Dynamics, Hefei National Laboratory for Physical Sciences at Microscale, Hefei 230027, China.

    ARF6 GTPase is a conserved regulator of membrane trafficking and actin-based cytoskeleton dynamics at the leading edge of migrating cells. A key determinant of ARF6 function is the lifetime of the GTP-bound active state, which is orchestrated by GTPase-activating protein (GAP) and GTP-GDP exchanging factor. However, very little is known about the molecular mechanisms underlying ARF6-mediated cell migration. To systematically analyze proteins that regulate ARF6 activity during cell migration, we performed a proteomic analysis of proteins selectively bound to active ARF6 using mass spectrometry and identified a novel ARF6-specific GAP, ACAP4. ACAP4 encodes 903 amino acids and contains two coiled coils, one pleckstrin homology domain, one GAP motif, and two ankyrin repeats. Our biochemical characterization demonstrated that ACAP4 has a phosphatidylinositol 4,5-bisphosphate-dependent GAP activity specific for ARF6. The co-localization of ACAP4 with ARF6 occurred in ruffling membranes formed upon AIF(4) and epidermal growth factor stimulation. ACAP4 overexpression limited the recruitment of ARF6 to the membrane ruffles in the absence of epidermal growth factor stimulation. Expression of GTP hydrolysis-resistant ARF6(Q67L) resulted in accumulations of ACAP4 and ARF6 in the cytoplasmic membrane, suggesting that GTP hydrolysis is required for the ARF6-dependent membrane remodeling. Significantly the depletion of ACAP4 by small interfering RNA or inhibition of ARF6 GTP hydrolysis by overexpressing GAP-deficient ACAP4 suppressed ARF6-dependent cell migration in wound healing, demonstrating the importance of ACAP4 in cell migration. Thus, our study sheds new light on the biological function of ARF6-mediated cell migration.

    Funded by: NCI NIH HHS: CA89019, CA92080; NCRR NIH HHS: RR01614, RR12961; NIDDK NIH HHS: DK56292

    Molecular & cellular proteomics : MCP 2006;5;8;1437-49

  • Abnormal ezrin localization is associated with clinicopathological features in invasive breast carcinomas.

    Sarrió D, Rodríguez-Pinilla SM, Dotor A, Calero F, Hardisson D and Palacios J

    Breast and Gynaecological Cancer Group, Molecular Pathology Programme, Centro Nacional de Investigaciones Oncológicas (CNIO), Madrid, Spain.

    The membrane-cytoskeleton crosslinker ezrin is associated with malignant progression and metastasis in human neoplasias. To study the role of ezrin in breast cancer, we first assessed ezrin expression in a panel of breast cancer cell lines by western blot and confocal microscopy. Western blot revealed no differences in total ezrin levels among these breast cell lines. However, immunofluorescence staining revealed that Estrogen receptor (ER)-positive, noninvasive and nontumorigenic cell lines concentrated ezrin at the apical surface, whereas invasive cell lines localized ezrin in motile structures (membrane ruffles and filopodia) but also had more diffuse cytoplasmic staining. We next studied ezrin expression in 509 breast carcinomas using tissue microarrays. Immunohistochemical staining for ezrin, p53, Ki-67, phospho-Akt, HER2, and hormonal receptors was performed. Ezrin staining in normal breast epithelium localized at the apical, but not lateral, cell surface, whereas, in most breast tumor cases (331, 70.3%), it localized in the cytoplasm. Complete membranous staining occurred in 89 (18.9%) samples, and apical staining was seen in 51 (10.8%) cases. There were significant positive associations between cytoplasmic ezrin localization and adverse tumor characteristics such as high grade, high level of Ki-67 expression, hormonal-receptor negativity, and lymph-node metastases. Apical ezrin staining was associated with favorable clinicopathological features and node-negative tumors. Membranous ezrin staining was associated with high grade, strong HER2 and p-Akt expression. In conclusion, the switch of ezrin localization from the apical membrane to either the complete membrane or to the cytoplasm is correlated with dedifferentiation and adverse features in invasive breast tumors and cancer cell lines.

    Breast cancer research and treatment 2006;98;1;71-9

  • Quantitative proteomic analysis of B cell lipid rafts reveals that ezrin regulates antigen receptor-mediated lipid raft dynamics.

    Gupta N, Wollscheid B, Watts JD, Scheer B, Aebersold R and DeFranco AL

    Department of Microbiology and Immunology, University of California, San Francisco, California 94143, USA.

    Ligation of the B cell antigen receptor (BCR) with antigen induces lipid raft coalescence, a process that occurs after crosslinking of a variety of signaling receptors and is thought to potentiate cellular activation. To investigate lipid raft dynamics during BCR signaling, we quantitatively analyzed the B cell lipid raft proteome. BCR engagement induced dissociation of the adaptor protein ezrin from lipid rafts as well as threonine dephosphorylation of ezrin and its concomitant detachment from actin, indicating a transient uncoupling of lipid rafts from the actin cytoskeleton. Expression of constitutively active ezrin chimeras inhibited the BCR-induced coalescence of lipid rafts. Our data demonstrate that the release of ezrin from lipid rafts acts as a critical trigger that regulates lipid raft dynamics during BCR signaling.

    Funded by: NHLBI NIH HHS: N01-HV-28179; NIAID NIH HHS: AI20038, AI41109; NIDDK NIH HHS: DK068292

    Nature immunology 2006;7;6;625-33

  • Ezrin expression is related to poor prognosis in FIGO stage I endometrioid carcinomas.

    Köbel M, Langhammer T, Hüttelmaier S, Schmitt WD, Kriese K, Dittmer J, Strauss HG, Thomssen C and Hauptmann S

    Institute of Pathology, Martin-Luther-University Halle-Wittenberg, Halle, Germany. martin.koebel@medizin.uni-halle.de

    As a cortical cytoskeletal protein, ezrin adapts the cytoplasmic tail of CD44 to the actin-based cytoskeleton and is functionally involved in migration and adhesion that are prerequisites for metastasis. To assess the importance of ezrin and its associated protein osteopontin for the progression of endometrioid carcinoma in FIGO stage I, we analyzed paraffin-embedded tissue from 164 patients by immunohistochemistry and correlated these data with clinicopathological parameters. Ezrin was expressed in normal proliferating endometrial glands, as was confirmed by quantitative PCR and immunohistochemistry. In endometrioid carcinoma, enhanced ezrin expression correlated with a reduced overall survival in univariate analysis (P = 0.041). In contrast, no significant correlation was found for osteopontin. In multivariate survival analysis, among FIGO grade 3 and age, ezrin was still found to be an independent risk factor (relative risk 2.2, confidence interval 1.0-5.4, P = 0.047). Hence, elevated ezrin expression is a new independent prognostic marker in FIGO stage I endometrioid carcinoma, and thus provides further evidence for an important role of ezrin in tumor progression.

    Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 2006;19;4;581-7

  • Ezrin promotes ovarian carcinoma cell invasion and its retained expression predicts poor prognosis in ovarian carcinoma.

    Köbel M, Gradhand E, Zeng K, Schmitt WD, Kriese K, Lantzsch T, Wolters M, Dittmer J, Strauss HG, Thomssen C and Hauptmann S

    Department of Pathology, Martin Luther University Halle-Wittenberg, and Department of Gynecology, St. Elisabeth Hospital, Halle, Germany. martin.koebel@medizin.uni-halle.de

    The majority of patients diagnosed with ovarian carcinoma are classified as being in advanced stage of disease. In a situation of cancer spread throughout the abdominal cavity, a successful curative treatment is difficult to achieve. Therefore, preventing binding of tumor cells to the mesothelium is crucial for patients' outcome. One important mechanism is the interaction between hyaluronic acid and the CD44 receptor with its submembrane linking complex. This consists of ezrin, radixin, and moesin and connects the CD44 receptor with the cytoskeleton. To assess the role of ezrin and moesinfor ovarian carcinoma progression, we analyzed ovarian carcinoma samples from 105 patients for expression of ezrin and moesin by immunohistochemistry and correlated these data with several clinicopathological parameters. To elucidate the functional importance of ezrin and moesin, their expression was inhibited in SKOV-3 cells by RNA interference. Ezrin and moesin were strongly expressed in 49 and 48% of ovarian carcinoma samples, respectively, and their presence correlated with reduced overall survival in univariate analysis (ezrin, p=0.0189; moesin, p=0.0351). In multivariate analysis (including FIGO stage, residual tumor, histological type, and Silverberg grading), ezrin still remained significant as an independent risk factor (relative risk, 2.39; p=0.012). In SKOV-3 cells, siRNA against ezrin but not moesin inhibited in vitro invasion. These data imply that ezrin is necessary for tumor cell invasion, and the better prognosis of ovarian carcinomas lacking ezrin is probably related to their impaired invasion.

    International journal of gynecological pathology : official journal of the International Society of Gynecological Pathologists 2006;25;2;121-30

  • PKA-mediated protein phosphorylation regulates ezrin-WWOX interaction.

    Jin C, Ge L, Ding X, Chen Y, Zhu H, Ward T, Wu F, Cao X, Wang Q and Yao X

    Laboratory of Cellular Dynamics, University of Science and Technology of China, Heifei National Laboratory for Physical Sciences at the Microscale, Hefei 230027, China.

    The ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton, and also participate in signal-transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the cAMP-dependent protein kinase activation cascade to the regulated HCl secretion in gastric parietal cells. Our recent studies have mapped the PKA-mediated phosphorylation site to Ser(66) and established its functional role in parietal cell activation [R. Zhou et al., Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation, J. Biol. Chem. 278 (2003) 35651-35659], but the underlying basis for this regulation is not known. Here, we provide the first evidence that PKA-mediated phosphorylation of Ser(66)regulates the interaction of ezrin with WWOX, a WW domain-containing protein. Our biochemical study reveals that ezrin directly binds to the first WW domain of WWOX via its C-terminal tyrosine-containing polyproline sequence (470)PPPPPPVY(477). Mutational analyses further demonstrate that tyrosine(477) is essential for the ezrin-WWOX interaction. In addition, our study shows that PKA-mediated phosphorylation of ezrin is essential and sufficient for the apical localization of WWOX protein as disruption of ezrin-WWOX interaction eliminated the apical localization of WWOX. Finally, our study demonstrates the essential role of ezrin-WWOX interaction in the apical membrane remodeling associated with H,K-ATPase recruitment. Taken together, these results define a novel molecular mechanism underlying phospho-regulation of ezrin function by PKA in parietal cell activation.

    Biochemical and biophysical research communications 2006;341;3;784-91

  • Ezrin directly interacts with the alpha1b-adrenergic receptor and plays a role in receptor recycling.

    Stanasila L, Abuin L, Diviani D and Cotecchia S

    Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Lausanne, Switzerland.

    Using the yeast two-hybrid system, we identified ezrin as a protein interacting with the C-tail of the alpha1b-adrenergic receptor (AR). The interaction was shown to occur in vitro between the receptor C-tail and the N-terminal portion of ezrin, or Four-point-one ERM (FERM) domain. The alpha1b-AR/ezrin interaction occurred inside the cells as shown by the finding that the transfected alpha1b-AR and FERM domain or ezrin could be coimmunoprecipitated from human embryonic kidney 293 cell extracts. Mutational analysis of the alpha1b-AR revealed that the binding site for ezrin involves a stretch of at least four arginines on the receptor C-tail. The results from both receptor biotinylation and immunofluorescence experiments indicated that the FERM domain impaired alpha1b-AR recycling to the plasma membrane without affecting receptor internalization. The dominant negative effect of the FERM domain, which relies on its ability to mask the ezrin binding site for actin, was mimicked by treatment of cells with cytochalasin D, an actin depolymerizing agent. A receptor mutant (DeltaR8) lacking its binding site in the C-tail for ezrin displayed delayed receptor recycling. These findings identify ezrin as a new protein directly interacting with a G protein-coupled receptor and demonstrate the direct implication of ezrin in GPCR trafficking via an actin-dependent mechanism.

    The Journal of biological chemistry 2006;281;7;4354-63

  • Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.

    Kimura K, Wakamatsu A, Suzuki Y, Ota T, Nishikawa T, Yamashita R, Yamamoto J, Sekine M, Tsuritani K, Wakaguri H, Ishii S, Sugiyama T, Saito K, Isono Y, Irie R, Kushida N, Yoneyama T, Otsuka R, Kanda K, Yokoi T, Kondo H, Wagatsuma M, Murakawa K, Ishida S, Ishibashi T, Takahashi-Fujii A, Tanase T, Nagai K, Kikuchi H, Nakai K, Isogai T and Sugano S

    Life Science Research Laboratory, Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, 185-8601, Japan.

    By analyzing 1,780,295 5'-end sequences of human full-length cDNAs derived from 164 kinds of oligo-cap cDNA libraries, we identified 269,774 independent positions of transcriptional start sites (TSSs) for 14,628 human RefSeq genes. These TSSs were clustered into 30,964 clusters that were separated from each other by more than 500 bp and thus are very likely to constitute mutually distinct alternative promoters. To our surprise, at least 7674 (52%) human RefSeq genes were subject to regulation by putative alternative promoters (PAPs). On average, there were 3.1 PAPs per gene, with the composition of one CpG-island-containing promoter per 2.6 CpG-less promoters. In 17% of the PAP-containing loci, tissue-specific use of the PAPs was observed. The richest tissue sources of the tissue-specific PAPs were testis and brain. It was also intriguing that the PAP-containing promoters were enriched in the genes encoding signal transduction-related proteins and were rarer in the genes encoding extracellular proteins, possibly reflecting the varied functional requirement for and the restricted expression of those categories of genes, respectively. The patterns of the first exons were highly diverse as well. On average, there were 7.7 different splicing types of first exons per locus partly produced by the PAPs, suggesting that a wide variety of transcripts can be achieved by this mechanism. Our findings suggest that use of alternate promoters and consequent alternative use of first exons should play a pivotal role in generating the complexity required for the highly elaborated molecular systems in humans.

    Genome research 2006;16;1;55-65

  • Ezrin in osteosarcoma: comparison between conventional high-grade and central low-grade osteosarcoma.

    Park HR, Jung WW, Bacchini P, Bertoni F, Kim YW and Park YK

    Department of Pathology, College of Medicine, Hallym University, Anyang, Republic of Korea.

    Ezrin is a cytoskeleton linker protein that is actively involved in the regulation of growth and metastatic capacity of cancer cells. Recently, it has been demonstrated that a significant correlation exists between high ezrin expression levels and the poor outcome of pediatric osteosarcoma patients. The expression of ezrin was compared in conventional high-grade and central low-grade osteosarcoma lesions to investigate the role of ezrin overexpression in the metastasis of osteosarcoma. We compared the expression levels of the ezrin protein in 32 cases of high-grade osteosarcomas and 21 cases of low-grade osteosarcomas using immunohistochemistry. Ezrin protein expression levels were examined in three different human osteosarcoma cell lines by Western blotting. In addition, the mRNA expression levels of ezrin in these osteosarcoma cell lines and control fibroblasts were evaluated by real-time quantitative PCR. Ezrin immunoreactivity was present in 43.7% of high-grade osteosarcoma specimens. All low-grade osteosarcomas were negative for ezrin. The expression of ezrin was detected by Western blotting in all three osteosarcoma cell lines. The tested osteosarcoma cell lines showed marked amplification of ezrin mRNA compared to control cells. Taken together, ezrin appears to play a role in the progression of tumors, such as the metastasis of osteosarcoma. However, further data are needed before ezrin can be considered in clinical decision-making about osteosarcoma patients.

    Pathology, research and practice 2006;202;7;509-15

  • Ezrin mediates growth and survival in Ewing's sarcoma through the AKT/mTOR, but not the MAPK, signaling pathway.

    Krishnan K, Bruce B, Hewitt S, Thomas D, Khanna C and Helman LJ

    Molecular Oncology Section, Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Building 10, Room 1-3816, 10 Center Drive, Bethesda, MD 20892, USA. krishhka@mail.nih.gov

    Recent reports on the role of the membrane-cytoskeleton linker protein ezrin in sarcomas showed an effect on the formation of metastases, dependent on the level of ezrin expression. In this study, we explore the role of ezrin in Ewing's sarcoma, a frequently fatal mesenchymal neoplasm of children and young adults. Through both immunohistochemistry and Western immunoblot studies we find ubiquitous, high-level expression of ezrin in Ewing's sarcoma. In contrast to the observations in osteosarcoma and rhabdomyosarcoma, we demonstrate that inhibition of ezrin-mediated signal transduction, through the expression of a non-phosphorylatable T567A mutant, slows primary growth of Ewing's sarcoma cells in vitro. This reduction in growth is a result of increased apoptosis in the mutant expressing cells. We further show that expression of this mutant reduces the ability of Ewing's sarcoma cells to form experimental metastases in vivo. Molecular examination reveals that the action of ezrin in Ewing's sarcoma is dependent on the AKT/mTOR signal transduction cascade, but not MAP Kinase. These results, therefore, demonstrate that, in Ewing's sarcoma, the biology of ezrin is distinct from that described in other sarcomas. This study further validates ezrin as a potential therapeutic target.

    Clinical & experimental metastasis 2006;23;3-4;227-36

  • Ezrin controls the macromolecular complexes formed between an adapter protein Na+/H+ exchanger regulatory factor and the cystic fibrosis transmembrane conductance regulator.

    Li J, Dai Z, Jana D, Callaway DJ and Bu Z

    Fox Chase Cancer Center, Philadelphia, PA 19111, USA.

    Na(+)/H(+) exchanger regulatory factor (NHERF) is an adapter protein that is responsible for organizing a number of cell receptors and channels. NHERF contains two amino-terminal PDZ (postsynaptic density 95/disk-large/zonula occluden-1) domains that bind to the cytoplasmic domains of a number of membrane channels or receptors. The carboxyl terminus of NHERF interacts with the FERM domain (a domain shared by protein 4.1, ezrin, radixin, and moesin) of a family of actin-binding proteins, ezrin-radixin-moesin. NHERF was shown previously to be capable of enhancing the channel activities of cystic fibrosis transmembrane conductance regulator (CFTR). Here we show that binding of the FERM domain of ezrin to NHERF regulates the cooperative binding of NHERF to bring two cytoplasmic tails of CFTR into spatial proximity to each other. We find that ezrin binding activates the second PDZ domain of NHERF to interact with the cytoplasmic tails of CFTR (C-CFTR), so as to form a specific 2:1:1 (C-CFTR)(2).NHERF.ezrin ternary complex. Without ezrin binding, the cytoplasmic tail of CFTR only interacts strongly with the first amino-terminal PDZ domain to form a 1:1 C-CFTR.NHERF complex. Immunoprecipitation and immunoblotting confirm the specific interactions of NHERF with the full-length CFTR and with ezrin in vivo. Because of the concentrated distribution of ezrin and NHERF in the apical membrane regions of epithelial cells and the diverse binding partners for the NHERF PDZ domains, the regulation of NHERF by ezrin may be employed as a general mechanism to assemble channels and receptors in the membrane cytoskeleton.

    Funded by: NCI NIH HHS: CA06927

    The Journal of biological chemistry 2005;280;45;37634-43

  • Ezrin expression in prostate cancer and benign prostatic tissue.

    Valdman A, Fang X, Pang ST, Nilsson B, Ekman P and Egevad L

    Department of Surgical Science, Section of Urology, Karolinska Institute, Stockholm, Sweden.

    Background: The membrane-linking protein ezrin is highly expressed in several types of human cancers and correlations between its immunoreactivity and histopathological data as well as patient outcome have previously been shown. However, such studies have not yet been done on human prostate cancer. This study assesses ezrin protein expression in a series of clinical specimens.

    Methods: Immunohistochemical analysis was used to characterize patterns of ezrin expression in prostatic carcinoma and benign epithelium in 103 radical prostatectomy specimens. Ezrin immunoreactivity (IR) was scored 0 to 3 (absent, weak, moderate or strong staining). Agreement between three independent observers was calculated.

    Results: Ezrin IR in prostate cancers was moderate or strong in 70% of specimens while negative or only weakly positive in benign epithelium. Interobserver agreement of IR score was substantial (mean weighted kappa 0.70, range 0.67-0.73). Ezrin expression correlated with Gleason score (p=0.016) and seminal vesicle invasion (p=0.006) but not with extraprostatic extension or margin status. No correlation with biochemical recurrence after prostatectomy was found (p=0.19). Urothelial and squamous metaplasia invariably showed moderate or strong ezrin expression. Epithelium of seminal vesicles and ejaculatory ducts was always intensely positive.

    Conclusion: Ezrin was expressed in the majority of prostate cancers and correlated with adverse prognostic factors. Interestingly, high levels of ezrin IR were observed in benign metaplastic epithelium and in seminal vesicles.

    European urology 2005;48;5;852-7

  • Towards a proteome-scale map of the human protein-protein interaction network.

    Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP and Vidal M

    Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.

    Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.

    Funded by: NCI NIH HHS: R33 CA132073; NHGRI NIH HHS: P50 HG004233, R01 HG001715, RC4 HG006066, U01 HG001715; NHLBI NIH HHS: U01 HL098166

    Nature 2005;437;7062;1173-8

  • Prognostic impact of immunohistochemical expression of ezrin in highly malignant soft tissue sarcomas.

    Weng WH, Ahlén J, Aström K, Lui WO and Larsson C

    Department of Molecular Medicine, Karolinska University Hospital-Solna, Stockholm, Sweden. Wendy.Weng@cmm.ki.se

    Purpose: Ezrin is a cytoskeleton linker protein that is actively involved in regulating the growth and metastatic capacity of cancer cells. It has recently been reported to be involved in dissemination of pediatric soft tissue sarcoma (STS).

    To further evaluate the prognostic value of ezrin in STS progression, we screened 50 primary STSs of high malignancy grade using immunohistochemistry. At the initial surgery, all patients were without local or distant metastasis. The expression was then compared with the outcome during follow-up for at least 4 years or until the patients' death.

    Results: Twenty-five of the 50 STSs analyzed (50%) showed ezrin immunoreactivity in the membrane and cytoplasm of the tumor cells. A significant association was shown between positive expressions of ezrin and death in disease as well as overall survival (P = 0.014 and 0.007, respectively). Similarly, ezrin expression was significantly associated with development of distant metastasis during follow-up (P = 0.031), also excluding locally recurrent disease (P = 0.049). The relative abundance of metastasis in ezrin-positive cases was observed both over time and irrespective of time. In comparison with clinical, histopathologic, and genetic characteristics of the STSs, ezrin expression was found to correlate significantly with an infiltrative growth pattern outside the tumor capsule as well as with copy number gain of chromosomal region 9cen-q22.

    Conclusion: Our findings suggest that ezrin immunoreactivity could be valuable as an additional prognostic marker in highly malignant STSs and support a causative role of ezrin in STS tumor dissemination.

    Clinical cancer research : an official journal of the American Association for Cancer Research 2005;11;17;6198-204

  • Human immunodeficiency virus (HIV)-1 proteins and cytoskeleton: partners in viral life and host cell death.

    Matarrese P and Malorni W

    Section of Cell Aging and Degeneration, Department of Drug Research and Evaluation, Istituto Superiore di Sanitá, Viale Regina Elena 299, Rome, Italy.

    Cytoskeletal components play a major role in the human immunodeficiency virus-1 (HIV-1) infection. A wide variety of molecules belonging to the microfilament system, including actin filaments and actin binding proteins, as well as microtubules have a key role in regulating both cell life and death. Cell shape maintenance, cell polarity and cell movements as well as cytoplasmic trafficking of molecules determining cell fate, including apoptosis, are in fact instructed by the cytoskeleton components. HIV infection and viral particle production seem to be controlled by cytoskeleton as well. Furthermore, HIV-associated apoptosis failure can also be regulated by the actin network function. In fact, HIV protein gp120 is able to induce cytoskeleton-driven polarization, thus sensitizing T cells to CD95/Fas-mediated apoptosis. The microfilament system seems thus to be a sort of cytoplasmic supervisor of the viral particle, the host cell and the bystander cell's very fate.

    Cell death and differentiation 2005;12 Suppl 1;932-41

  • G protein-coupled receptor kinase 2-mediated phosphorylation of ezrin is required for G protein-coupled receptor-dependent reorganization of the actin cytoskeleton.

    Cant SH and Pitcher JA

    MRC Laboratory for Molecular and Cellular Biology and Department of Pharmacology, University College London, London, WC1E 6BT United Kingdom.

    G protein-coupled receptor kinase 2 (GRK2) phosphorylates and desensitizes activated G protein-coupled receptors (GPCRs). Here, we identify ezrin as a novel non-GPCR substrate of GRK2. GRK2 phosphorylates glutathione S-transferase (GST)-ezrin, but not an ezrin fusion protein lacking threonine 567 (T567), in vitro. These results suggest that T567, the regulatory phosphorylation site responsible for maintaining ezrin in its active conformation, represents the principle site of GRK2-mediated phosphorylation. Two lines of evidence indicate that GRK2-mediated ezrin-radixinmoesin (ERM) phosphorylation serves to link GPCR activation to cytoskeletal reorganization. First, in Hep2 cells muscarinic M1 receptor (M1MR) activation causes membrane ruffling. This ruffling response is ERM dependent and is accompanied by ERM phosphorylation. Inhibition of GRK2, but not rho kinase or protein kinase C, prevents ERM phosphorylation and membrane ruffling. Second, agonist-induced internalization of the beta2-adrenergic receptor (beta2AR) and M1MR is accompanied by ERM phosphorylation and localization of phosphorylated ERM to receptor-containing endocytic vesicles. The colocalization of internalized beta2AR and phosphorylated ERM is not dependent on Na+/H+ exchanger regulatory factor binding to the beta2AR. Inhibition of ezrin function impedes beta2AR internalization, further linking GPCR activation, GRK activity, and ezrin function. Overall, our results suggest that GRK2 serves not only to attenuate but also to transduce GPCR-mediated signals.

    Funded by: Wellcome Trust

    Molecular biology of the cell 2005;16;7;3088-99

  • PALS1 specifies the localization of ezrin to the apical membrane of gastric parietal cells.

    Cao X, Ding X, Guo Z, Zhou R, Wang F, Long F, Wu F, Bi F, Wang Q, Fan D, Forte JG, Teng M and Yao X

    School of Life Science, University of Science and Technology of China, Hefei 230027, Peoples Republic of China.

    The ERM (ezrin/radixin/moesin) proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and also participate in signal transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the protein kinase A activation cascade to regulated HCl secretion in gastric parietal cells. Here, we show that the integrity of ezrin is essential for parietal cell activation and provide the first evidence that ezrin interacts with PALS1, an evolutionarily conserved PDZ and SH3 domain-containing protein. Our biochemical study verifies that ezrin binds to PALS1 via its N terminus and is co-localized with PALS1 to the apical membrane of gastric parietal cells. Furthermore, our study shows that PALS1 is essential for the apical localization of ezrin, as either suppression of PALS1 protein accumulation or deletion of the PALS1-binding domain of ezrin eliminated the apical localization of ezrin. Finally, our study demonstrates the essential role of ezrin-PALS1 interaction in the apical membrane remodeling associated with parietal cell secretion. Taken together, these results define a novel molecular mechanism linking ezrin to the conserved apical polarity complexes and their roles in polarized epithelial secretion of gastric parietal cells.

    Funded by: NIDDK NIH HHS: DK-56292

    The Journal of biological chemistry 2005;280;14;13584-92

  • Characterization of the NF2 protein merlin and the ERM protein ezrin in human, rat, and mouse central nervous system.

    Grönholm M, Teesalu T, Tyynelä J, Piltti K, Böhling T, Wartiovaara K, Vaheri A and Carpén O

    Neuroscience Program, Biomedicum Helsinki, University of Helsinki and Helsinki University Central Hospital, PB 63, Haartmaninkatu 8, 00014 Helsinki, Finland. mikaela.gronholm@helsinki.fi

    The neurofibromatosis 2 (NF2) protein, merlin, is structurally related to the ERM (ezrin-radixin-moesin) protein family of membrane-cytoskeleton linkers and is mutated in nervous system tumors. Apart from tumor suppressor activity, merlin's functions are poorly understood. We compared the localization and expression of merlin and ezrin in developing and adult brain and in brain-derived progenitor cells. Both proteins were widely but differentially expressed in human, rat, and mouse brain. In brain tissue and neuronal progenitor cell cultures merlin was predominantly found in neurons while ezrin was expressed in astrocytes. Merlin expression was seen from E11 in mouse embryos, whereas ezrin was present earlier. Both proteins were expressed in embryonic mouse neurospheres, where ezrin was specifically localized in filopodia of adherent neuronal progenitor cells. Subcellular analysis demonstrated ezrin in fine filopodial structures in astrocytes, while merlin was detected in neuronal synaptic junctions. The widespread expression of merlin in brain and its association with protein kinase A suggest a role for merlin in brain biology.

    Molecular and cellular neurosciences 2005;28;4;683-93

  • Cytoskeleton-mediated death receptor and ligand concentration in lipid rafts forms apoptosis-promoting clusters in cancer chemotherapy.

    Gajate C and Mollinedo F

    Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas-Universidad de Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain.

    While investigating the mechanism of action of the novel antitumor drug Aplidin, we have discovered a potent and novel cell-killing mechanism that involves the formation of Fas/CD95-driven scaffolds in membrane raft clusters housing death receptors and apoptosis-related molecules. Fas, tumor necrosis factor-receptor 1, and tumor necrosis factor-related apoptosis-inducing ligand receptor 2/death receptor 5 were clustered into lipid rafts in leukemic Jurkat cells following Aplidin treatment, the presence of Fas being essential for apoptosis. Preformed membrane-bound Fas ligand (FasL) as well as downstream signaling molecules, including Fas-associated death domain-containing protein, procaspase-8, procaspase-10, c-Jun amino-terminal kinase, and Bid, were also translocated into lipid rafts, connecting death receptor extrinsic and mitochondrial intrinsic apoptotic pathways. Blocking Fas/FasL interaction partially inhibited Aplidin-induced apoptosis. Aplidin was rapidly incorporated into membrane rafts, and drug uptake was inhibited by lipid raft disruption. Actin-linking proteins ezrin, moesin, RhoA, and RhoGDI were conveyed into Fas-enriched rafts in drug-treated leukemic cells. Disruption of lipid rafts and interference with actin cytoskeleton prevented Fas clustering and apoptosis. Thus, Aplidin-induced apoptosis involves Fas activation in both a FasL-independent way and, following Fas/FasL interaction, an autocrine way through the concentration of Fas, membrane-bound FasL, and signaling molecules in membrane rafts. These data indicate a major role of actin cytoskeleton in the formation of Fas caps and highlight the crucial role of the clusters of apoptotic signaling molecule-enriched rafts in apoptosis, acting as concentrators of death receptors and downstream signaling molecules and as the linchpin from which a potent death signal is launched.

    The Journal of biological chemistry 2005;280;12;11641-7

  • Listeria monocytogenes exploits ERM protein functions to efficiently spread from cell to cell.

    Pust S, Morrison H, Wehland J, Sechi AS and Herrlich P

    Department of Cell Biology, Gesellschaft für Biotechnologische Forschung (GBF), Braunschweig, Germany.

    Cell-to-cell spread is a fundamental step in the infection cycle of Listeria monocytogenes that strictly depends on the formation of bacteria-induced protrusions. Since Listeria actin tails in the protrusions are tightly associated with the plasma membrane, we hypothesised that membrane-cytoskeleton linkers would be required for initiating and sustaining their formation and the subsequent cell-to-cell spread. We have found that ezrin, a member of the ezrin, radixin and moesin (ERM) family that functions as a key membrane-cytoskeleton linker, accumulates at Listeria protrusions. The ability of Listeria to induce protrusions and effectively spread between adjacent cells depends on the interaction of ERM proteins with both a membrane component such as CD44 and actin filaments. Interfering with either of these interactions or with ERM proteins phosphorylation not only reduces the number of protrusions but also alters their morphology, resulting in the formation of short and collapsed protrusions. As a consequence, Listeria cell-to-cell spread is severely impaired. Thus, ERM proteins are exploited by Listeria to escape the host immune response and to succeed in the development of the infection.

    The EMBO journal 2005;24;6;1287-300

  • Src phosphorylates ezrin at tyrosine 477 and induces a phosphospecific association between ezrin and a kelch-repeat protein family member.

    Heiska L and Carpén O

    Department of Pathology, Neuroscience Program, Biomedicum Helsinki, University of Helsinki and Helsinki University Hospital, FIN-00014 Helsinki, Finland.

    Ezrin, a linker between plasma membrane and actin cytoskeleton possesses morphogenic properties and can promote dissemination of tumor cells. Ezrin is phosphorylated on tyrosine, but a detailed picture of the signaling pathways involved in this modification is lacking. The transforming tyrosine kinase Src has various cytoskeletal substrates and is involved in regulation of cellular adhesion. We studied the role of Src in tyrosine phosphorylation of ezrin in adherent cells. We show that ezrin is phosphorylated in human embryonic kidney 293 cells in a Src family-dependent way. In SYF cells lacking Src, Yes, and Fyn, ezrin was not tyrosine-phosphorylated but reintroduction of wild-type Src followed by Src activation or introduction of active Src restored phosphorylation. Mapping of the Src-catalyzed tyrosine in vitro and in vivo by site-directed mutagenesis demonstrated Tyr(477) as the primary target residue. We generated a pTyr(477)-phosphospecific antibody, which confirmed that Tyr(477) becomes phosphorylated in cells in a Src-dependent manner. Tyr(477) phosphorylation did not affect ezrin head-to-tail association or phosphorylation of ezrin on threonine 566, indicating that the function of Tyr(477) phosphorylation is not related to the intramolecular regulation of ezrin. A modified yeast two-hybrid screen in which ezrin bait was phosphorylated by Src identified a novel interaction with a kelch-repeat protein family member, KBTBD2 (Kelch-repeat and BTB/POZ domain containing 2). The Src dependence of the interaction was further verified by affinity precipitation assays. Identification of a functional interplay with Src opens novel avenues for further characterization of the biological activities of ezrin.

    The Journal of biological chemistry 2005;280;11;10244-52

  • Ezrin mutants affecting dimerization and activation.

    Chambers DN and Bretscher A

    Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, New York 14853, USA.

    ERM (ezrin/radixin/moesin) proteins provide a regulated linkage between membrane-associated proteins and the actin cytoskeleton. Previous work has shown that ezrin can exist in a dormant monomeric state in which the N-terminal FERM domain is tightly associated with the C-ERMAD (carboxyl-terminal ERM association domain), masking binding sites for at least some ligands, including F-actin and the scaffolding protein EBP50. Activation of ezrin requires relief of the intramolecular association, and this is believed to involve phosphorylation of threonine 567. Studies have therefore employed the T567D phosphomimetic mutant to explore the consequences of ezrin activation in vivo. Ezrin also exists as a stable dimer, in which the orientation of the two subunits is unknown, but might involve the central alpha-helical region predicted to form a coiled-coil. By characterization of ezrin mutants, we show that relief of the intramolecular association in the monomer results in unmasking of ligand binding sites and a significant conformational change, that the T567D mutation has a small effect on the biochemical activation of ezrin, and that the predicted coiled-coil region does not drive dimer formation. These results provide strong support for the conformational activation model of ezrin, elucidate the basis for dimer formation, and reveal that a mutant generally considered to be fully activated is not.

    Funded by: NIGMS NIH HHS: GM36652

    Biochemistry 2005;44;10;3926-32

  • Src-dependent ezrin phosphorylation in adhesion-mediated signaling.

    Srivastava J, Elliott BE, Louvard D and Arpin M

    Morphogenèse et Signalisation Cellulaires, UMR144 CNRS-Institut Curie, 75248 Paris Cedex 05, France.

    In addition to providing a regulated linkage between the membrane and the actin cytoskeleton, ezrin participates in signal transduction pathways. Here we describe that expression of the ezrin Y145F mutant delays epithelial cell spreading on fibronectin by inhibiting events leading to FAK activation. The defect in spreading was rescued by the overexpression of catalytically functional Src. We demonstrate that ezrin Y145 is phosphorylated in A431 cells stimulated with epidermal growth factor (EGF) and in v-Src-transformed cells. Moreover in cells devoid of Src, SYF-/- fibroblasts, ezrin Y145 phosphorylation could only be detected upon the introduction of an active form of Src. The phosphorylation of ezrin at Y145 required prior binding of the Src SH2 domain to ezrin. Our results further show that Src activity influences its binding to ezrin and a positive feedback mechanism for Src-mediated Y145 phosphorylation is implied. Interestingly, cells expressing ezrin Y145F did not proliferate when cultured in a 3D collagen gel. Collectively, our results demonstrate a key signaling input of Src-dependent ezrin phosphorylation in adhesion-mediated events in epithelial cells.

    Molecular biology of the cell 2005;16;3;1481-90

  • Role of a novel EGF-like domain-containing gene NGX6 in cell adhesion modulation in nasopharyngeal carcinoma cells.

    Ma J, Zhou J, Fan S, Wang L, Li X, Yan Q, Zhou M, Liu H, Zhang Q, Zhou H, Gan K, Li Z, Peng C, Xiong W, Tan C, Shen S, Yang J, Li J and Li G

    Cancer Research Institute, Xiang-Ya School of Medicine, 110 Xiang-Ya Road, Changsha, Hunan 410078, China.

    The epidermal growth factor (EGF)-like domain is involved in receptor-ligand interactions, extracellular matrix formation, cell adhesion and chemotaxis. Nasopharyngeal carcinoma associated gene 6 (NGX6) is a novel EGF-like domain-containing gene located at the high frequent loss of heterozygosity (LOH) region 9p21-22 associated with nasopharyngeal carcinoma (NPC). It is down-regulated in NPC and its over-expression can delay the cell cycle G(0)-G(1) progression in NPC cells. In the present study, in situ hybridization analysis, using NPC tissue microarrays, showed that loss of NGX6 expression was associated with NPC lymph node metastasis. The Tet-on gene expression system and cDNA array techniques were used to profile the potential targets of NGX6. We found that NGX6 can influence the expression of some cell adhesion molecules in NPC cells. NGX6 can associate with ezrin, a linkage between the cell membrane and cytoskeleton. The NGX6 protein was expressed on the cell surface as a glycoprotein. Ectopic induction of NGX6 can impair NPC cell migration and invasive ability as well as improve cell adhesion and gap junctional intercellular communication, and can suppress tumor formation in vivo. The data revealed that NGX6 plays a role in cell adhesion modulation in NPC cells.

    Carcinogenesis 2005;26;2;281-91

  • Akt2 phosphorylates ezrin to trigger NHE3 translocation and activation.

    Shiue H, Musch MW, Wang Y, Chang EB and Turner JR

    Department of Pathology, The University of Chicago, Chicago, Illinois 60637, USA.

    Initiation of Na(+)-glucose cotransport in intestinal absorptive epithelia causes NHE3 to be translocated to the apical plasma membrane, leading to cytoplasmic alkalinization. We reported recently that this NHE3 translocation requires ezrin phosphorylation. However, the kinase that phosphorylates ezrin in this process has not been identified. Because Akt has also been implicated in NHE3 translocation, we investigated the hypothesis that Akt phosphorylates ezrin. After initiation of Na(+)-glucose cotransport, Akt is activated with kinetics that parallel those of ezrin phosphorylation. Inhibition of p38 MAP kinase, which blocks ezrin phosphorylation, also prevents Akt activation. Purified Akt directly phosphorylates recombinant ezrin at threonine 567 in vitro in an ATP-dependent manner. This in vitro phosphorylation can be prevented by Akt inhibitors. In intact cells, inhibition of either phosphoinositide 3-kinase, an upstream regulator of Akt, or inhibition of Akt itself using inhibitors validated in vitro prevents ezrin phosphorylation after initiation of Na(+)-glucose cotransport. Specific small interfering RNA knockdown of Akt2 prevented ezrin phosphorylation in intact cells. Pharmacological Akt inhibition or Akt2 knockdown also prevented NHE3 translocation and activation after initiation of Na(+)-glucose cotransport, confirming the functional role of Akt2. These studies therefore identify Akt2 as a critical kinase that regulates ezrin phosphorylation and activation. This Akt2-dependent ezrin phosphorylation leads to NHE3 translocation and activation.

    Funded by: NCI NIH HHS: P30-CA14599; NIDDK NIH HHS: P30-DK42086, R01 DK061931-04, R01-DK038510, R01-DK61931

    The Journal of biological chemistry 2005;280;2;1688-95

  • 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

  • Ezrin/radixin/moesin proteins are high affinity targets for ADP-ribosylation by Pseudomonas aeruginosa ExoS.

    Maresso AW, Baldwin MR and Barbieri JT

    Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.

    Pseudomonas aeruginosa ExoS is a bifunctional type III-secreted cytotoxin. The N terminus (amino acids 96-233) encodes a GTPase-activating protein activity, whereas the C terminus (amino acids 234-453) encodes a factor-activating ExoS-dependent ADP-ribosyltransferase activity. The GTPase-activating protein activity inactivates the Rho GTPases Rho, Rac, and Cdc42 in cultured cells and in vitro, whereas the ADP-ribosylation by ExoS is poly-substrate-specific and includes Ras as an early target for ADP-ribosylation. Infection of HeLa cells with P. aeruginosa producing a GTPase-activating protein-deficient form of ExoS rounded cells, indicating the ADP-ribosyltransferase domain alone is sufficient to elicit cytoskeletal changes. Examination of substrates modified by type III-delivered ExoS identified a 70-kDa protein as an early and predominant target for ADP-ribosylation. Matrix-assisted laser desorption ionization mass spectroscopy identified this protein as moesin, a member of the ezrin/radixin/moesin (ERM) family of proteins. ExoS ADP-ribosylated recombinant moesin at a linear velocity that was 5-fold faster and with a K(m) that was 2 orders of magnitude lower than Ras. Moesin homologs ezrin and radixin were also ADP-ribosylated, indicating the ERMs collectively represent high affinity targets of ExoS. Type III delivered ExoS ADP-ribosylated moesin and ezrin (and/or radixin) in cultured HeLa cells. The ERM proteins contribute to cytoskeleton dynamics, and the ability of ExoS to ADP-ribosylate the ERM proteins links ADP-ribosylation with the cytoskeletal changes associated with ExoS intoxication.

    Funded by: NHLBI NIH HHS: HL68912; NIAID NIH HHS: AI30162

    The Journal of biological chemistry 2004;279;37;38402-8

  • Mutagenesis of the ezrin-radixin-moesin binding domain of L-selectin tail affects shedding, microvillar positioning, and leukocyte tethering.

    Ivetic A, Florey O, Deka J, Haskard DO, Ager A and Ridley AJ

    Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, 91 Riding House Street, London W1W 7BS United Kingdom. aleks@ludwig.ucl.ac.uk

    L-selectin is a cell adhesion molecule that mediates the initial capture (tethering) and subsequent rolling of leukocytes along ligands expressed on endothelial cells. We have previously identified ezrin and moesin as novel binding partners of the 17-amino acid L-selectin tail, but the biological role of this interaction is not known. Here we identify two basic amino acid residues within the L-selectin tail that are required for binding to ezrin-radixinmoesin (ERM) proteins: arginine 357 and lysine 362. L-selectin mutants defective for ERM binding show reduced localization to microvilli and decreased phorbol 12-myristate 13-acetate-induced shedding of the L-selectin ectodomain. Cells expressing these L-selectin mutants have reduced tethering to the L-selectin ligand P-selectin glycoprotein ligand-1, but rolling velocity on P-selectin glycoprotein ligand-1 is not affected. These results suggest that ERM proteins are required for microvillar positioning of L-selectin and that this is important both for leukocyte tethering and L-selectin shedding.

    The Journal of biological chemistry 2004;279;32;33263-72

  • The NHE1 Na+/H+ exchanger recruits ezrin/radixin/moesin proteins to regulate Akt-dependent cell survival.

    Wu KL, Khan S, Lakhe-Reddy S, Jarad G, Mukherjee A, Obejero-Paz CA, Konieczkowski M, Sedor JR and Schelling JR

    Department of Medicine, Rammelkamp Center for Research, MetroHealth Medical Center Campus, Case Western Reserve University, Cleveland, Ohio 44109-1998, USA.

    Apoptosis results in cell shrinkage and intracellular acidification, processes opposed by the ubiquitously expressed NHE1 Na(+)/H(+) exchanger. In addition to mediating Na(+)/H(+) transport, NHE1 interacts with ezrin/radixin/moesin (ERM), which tethers NHE1 to cortical actin cytoskeleton to regulate cell shape, adhesion, motility, and resistance to apoptosis. We hypothesize that apoptotic stress activates NHE1-dependent Na(+)/H(+) exchange, and NHE1-ERM interaction is required for cell survival signaling. Apoptotic stimuli induced NHE1-regulated Na(+)/H(+) transport, as demonstrated by ethyl-N-isopropyl-amiloride-inhibitable, intracellular alkalinization. Ectopic NHE1, but not NHE3, expression rescued NHE1-null cells from apoptosis induced by staurosporine or N-ethylmaleimide-stimulated KCl efflux. When cells were subjected to apoptotic stress, NHE1 and phosphorylated ERM physically associated within the cytoskeleton-enriched fraction, resulting in activation of the pro-survival kinase, Akt. NHE1-associated Akt activity and cell survival were inhibited in cells expressing ERM binding-deficient NHE1, dominant negative ezrin constructs, or ezrin mutants with defective binding to phosphoinositide 3-kinase, an upstream regulator of Akt. We conclude that NHE1 promotes cell survival by dual mechanisms: by defending cell volume and pH(i) through Na(+)/H(+) exchange and by functioning as a scaffold for recruitment of a signalplex that includes ERM, phosphoinositide 3-kinase, and Akt.

    Funded by: NIDDK NIH HHS: DK054178, DK38558, DK64719

    The Journal of biological chemistry 2004;279;25;26280-6

  • Nuclear ERM (ezrin, radixin, moesin) proteins: regulation by cell density and nuclear import.

    Batchelor CL, Woodward AM and Crouch DH

    Biomedical Research Centre, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.

    The highly conserved ERM (ezrin-radixin-moesin) family of proteins function as molecular linkers between the actin cytoskeleton and transmembrane receptors. We now provide unequivocal evidence that full-length endogenous ezrin and moesin also localise to the nucleus in two independent mammalian cell lines. All three ERM family members can localise to the nucleus upon exogenous expression of their GFP-tagged counterparts, suggesting a common family trend. Furthermore, Dmoesin, the Drosophila ERM homologue, is present in the nucleus of an insect cell line and can localise to the nucleus when exogenously expressed in MDCK cells. The nuclear localisation of endogenous ezrin and moesin is regulated by cell density and is resistant to detergent extraction, suggesting tight association with nuclear structures. Furthermore, phosphorylation in the actin-binding domain is not a prerequisite for nuclear localisation. We have identified a specific nuclear localisation sequence, which is conserved and functional in all ERM family members, implying specific regulated nuclear import. Although the precise nuclear function of the ERM proteins is unknown, these data provide further evidence that an increasing number of cytoskeletal components directly link the plasma membrane with nuclear events.

    Experimental cell research 2004;296;2;208-22

  • CD95/phosphorylated ezrin association underlies HIV-1 GP120/IL-2-induced susceptibility to CD95(APO-1/Fas)-mediated apoptosis of human resting CD4(+)T lymphocytes.

    Luciani F, Matarrese P, Giammarioli AM, Lugini L, Lozupone F, Federici C, Iessi E, Malorni W and Fais S

    Laboratories of Immunology, Istituto Superiore di Sanità, 00161 Rome, Italy.

    CD95(APO-1/Fas)-mediated apoptosis of bystander uninfected T cells exerts a major role in the HIV-1-mediated CD4+ T-cell depletion. HIV-1 gp120 has a key role in the induction of sensitivity of human lymphocytes to CD95-mediated apoptosis through its interaction with the CD4 receptor. Recently, we have shown the importance of CD95/ezrin/actin association in CD95-mediated apoptosis. In this study, we explored the hypothesis that the gp120-mediated CD4 engagement could be involved in the induction of susceptibility of primary human T lymphocytes to CD95-mediated apoptosis through ezrin phosphorylation and ezrin-to-CD95 association. Here, we show that gp120/IL-2 combined stimuli, as well as the direct CD4 triggering, on human primary CD4(+)T lymphocytes induced an early and stable ezrin activation through phosphorylation, consistent with the induction of ezrin/CD95 association and susceptibility to CD95-mediated apoptosis. Our results provide a new mechanism through which HIV-1-gp120 may predispose resting CD4(+)T cell to bystander CD95-mediated apoptosis and support the key role of ezrin/CD95 linkage in regulating susceptibility to CD95-mediated apoptosis.

    Cell death and differentiation 2004;11;5;574-82

  • Cyclic AMP-dependent protein kinase phosphorylates merlin at serine 518 independently of p21-activated kinase and promotes merlin-ezrin heterodimerization.

    Alfthan K, Heiska L, Grönholm M, Renkema GH and Carpén O

    Biomedicum Helsinki, Department of Anatomy and Pathology, Neuroscience Program, University of Helsinki and Helsinki University Hospital, FIN-00014 Helsinki, Finland.

    Mutations in the NF2 tumor suppressor gene encoding merlin induce the development of tumors of the nervous system. Merlin is highly homologous to the ERM (ezrin-radixin-moesin) family of membrane/cytoskeleton linker proteins. However, the mechanism for the tumor suppressing activity of merlin is not well understood. Previously, we characterized a novel role for merlin as a protein kinase A (PKA)-anchoring protein, which links merlin to the cAMP/PKA signaling pathway. In this study we show that merlin is also a target for PKA-induced phosphorylation. In vitro [gamma-(33)P]ATP labeling revealed that both the merlin N and C termini are phosphorylated by PKA. Furthermore, both in vitro and in vivo phosphorylation studies of the wild-type and mutated C termini demonstrated that PKA can phosphorylate merlin at serine 518, a site that is phosphorylated also by p21-activated kinases (PAKs). Merlin was phosphorylated by PKA in cells in which PAK activity was suppressed, indicating that the two kinases function independently. Both in vitro and in vivo interaction studies indicated that phosphorylation of serine 518 promotes heterodimerization between merlin and ezrin, an event suggested to convert merlin from a growth-suppressive to a growth-permissive state. This study provides further evidence on the connection between merlin and cAMP/PKA signaling and suggests a role for merlin in the cAMP/PKA transduction pathway.

    The Journal of biological chemistry 2004;279;18;18559-66

  • The EBP50-moesin interaction involves a binding site regulated by direct masking on the FERM domain.

    Finnerty CM, Chambers D, Ingraffea J, Faber HR, Karplus PA and Bretscher A

    Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.

    Members of the ezrin-radixin-moesin (ERM) protein family serve as regulated microfilament-membrane crosslinking proteins that, upon activation, bind the scaffolding protein ERM-phosphoprotein of 50 kDa (EBP50). Here we report a 3.5 A resolution diffraction analysis of a complex between the active moesin N-terminal FERM domain and a 38 residue peptide from the C terminus of EBP50. This crystallographic result, combined with sequence and structural comparisons, suggests that the C-terminal 11 residues of EBP50 binds as an alpha-helix at the same site occupied in the dormant monomer by the last 11 residues of the inhibitory moesin C-terminal tail. Biochemical support for this interpretation derives from in vitro studies showing that appropriate mutations in both the EBP50 tail peptide and the FERM domain reduce binding, and that a peptide representing just the C-terminal 14 residues of EBP50 also binds to moesin. Combined with the recent identification of the I-CAM-2 binding site on the ERM FERM domain (Hamada, K., Shimizu, T., Yonemura, S., Tsukita, S., and Hakoshima, T. (2003) EMBO J. 22, 502-514), this study reveals that the FERM domain contains two distinct binding sites for membrane-associated proteins. The contribution of each ligand to ERM function can now be dissected by making structure-based mutations that specifically affect the binding of each ligand.

    Funded by: PHS HHS: DMR 9713424

    Journal of cell science 2004;117;Pt 8;1547-52

  • Identification and relevance of the CD95-binding domain in the N-terminal region of ezrin.

    Lozupone F, Lugini L, Matarrese P, Luciani F, Federici C, Iessi E, Margutti P, Stassi G, Malorni W and Fais S

    Laboratory of Immunology and Ultrastructures, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome 00161, Italy.

    The CD95 (Fas/APO-1) linkage to the actin cytoskeleton through ezrin is an essential requirement for susceptibility to the CD95-mediated apoptosis in CD4+ T cells. We have previously shown that moesin was not involved in the binding to CD95. Here we further support the specificity of the ezrin/CD95 binding, showing that radixin did not bind CD95. The ezrin region specifically and directly involved in the binding to CD95 was located in the middle lobe of the ezrin FERM domain, between amino acids 149 and 168. In this region, ezrin, radixin, and moesin show 60-65% identity, as compared with the 86% identity in the whole FERM domain. Transfection of two different human cell lines with a green fluorescent protein-tagged ezrin mutated in the CD95-binding epitope, induced a marked inhibition of CD95-mediated apoptosis. In these cells, the mutated ezrin did not co-localize or co-immunoprecipitate with CD95. Further analysis showed that the mutated ezrin, while unable to bind CD95, was fully able to bind actin, thus preventing the actin linkage to CD95. Altogether, our results support the specificity of ezrin in the association to CD95 and the importance of the ezrin-to-CD95 linkage in CD95-mediated apoptosis. Moreover, this study suggests that a major role of ezrin is to connect CD95 to actin, thus allowing the CD95 polarization on the cells and the occurrence of the following multiple cascades of the CD95 pathway.

    The Journal of biological chemistry 2004;279;10;9199-207

  • The membrane-cytoskeleton linker ezrin is necessary for osteosarcoma metastasis.

    Khanna C, Wan X, Bose S, Cassaday R, Olomu O, Mendoza A, Yeung C, Gorlick R, Hewitt SM and Helman LJ

    Pediatric Oncology Branch and Tissue Array Project Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA. khannac@mail.nih.gov

    Metastatic cancers, once established, are the primary cause of mortality associated with cancer. Previously, we used a genomic approach to identify metastasis-associated genes in cancer. From this genomic data, we selected ezrin for further study based on its role in physically and functionally connecting the actin cytoskeleton to the cell membrane. In a mouse model of osteosarcoma, a highly metastatic pediatric cancer, we found ezrin to be necessary for metastasis. By imaging metastatic cells in the lungs of mice, we showed that ezrin expression provided an early survival advantage for cancer cells that reached the lung. AKT and MAPK phosphorylation and activity were reduced when ezrin protein was suppressed. Ezrin-mediated early metastatic survival was partially dependent on activation of MAPK, but not AKT. To define the relevance of ezrin in the biology of metastasis, beyond the founding mouse model, we examined ezrin expression in dogs that naturally developed osteosarcoma. High ezrin expression in dog tumors was associated with early development of metastases. Consistent with this data, we found a significant association between high ezrin expression and poor outcome in pediatric osteosarcoma patients.

    Nature medicine 2004;10;2;182-6

  • Expression profiling identifies the cytoskeletal organizer ezrin and the developmental homeoprotein Six-1 as key metastatic regulators.

    Yu Y, Khan J, Khanna C, Helman L, Meltzer PS and Merlino G

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

    Patients presenting with metastatic rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children, have a very poor clinical prognosis. This is due, in large part, to our rudimentary knowledge of the molecular events that dictate metastatic potential. We used cDNA microarray analysis of RMS cell lines, derived from Ink4a/Arf-deficient mice transgenic for hepatocyte growth factor/scatter factor (HGF/SF), to identify a set of genes whose expression was significantly different between highly and poorly metastatic cells. Subsequent in vivo functional studies revealed that the actin filament-plasma membrane linker ezrin (encoded by Vil2) and the homeodomain-containing transcription factor Six-1 (sine oculis-related homeobox-1 homolog) had essential roles in determining the metastatic fate of RMS cells. VIL2 and SIX1 expression was enhanced in human RMS tissue, significantly correlating with clinical stage. The identification of ezrin and Six-1 as critical regulators of metastasis in RMS provides new mechanistic and therapeutic insights into this pediatric cancer.

    Nature medicine 2004;10;2;175-81

  • A novel cell-cell junction system: the cortex adhaerens mosaic of lens fiber cells.

    Straub BK, Boda J, Kuhn C, Schnoelzer M, Korf U, Kempf T, Spring H, Hatzfeld M and Franke WW

    Division of Cell Biology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.

    The anucleate prismoid fiber cells of the eye lens are densely packed to form a tissue in which the plasma membranes and their associated cytoplasmic coat form a single giant cell-cell adhesive complex, the cortex adhaerens. Using biochemical and immunoprecipitation methods in various species (cow, pig, rat), in combination with immunolocalization microscopy, we have identified two different major kinds of cortical complex. In one, the transmembrane glycoproteins N-cadherin and cadherin-11 [which also occur in heterotypic ('mixed') complexes] are associated with alpha- and beta-catenin, plakoglobin (proportions variable among species), p120ctn and vinculin. The other complex contains ezrin, periplakin, periaxin and desmoyokin (and so is called the EPPD complex), usually together with moesin, spectrin(s) and plectin. In sections through lens fiber tissue, the short sides of the lens fiber hexagons appear to be enriched in the cadherin-based complexes, whereas the EPPD complexes also occur on the long sides. Moreover, high resolution double-label fluorescence microscopy has revealed, on the short sides, a finer, almost regular mosaicism of blocks comprising the cadherin-based, catenin-containing complexes, alternating with patches formed by the EPPD complexes. The latter, a new type of junctional plaque ensemble of proteins hitherto known only from certain other cell types, must be added to the list of major lens cortex proteins. We here discuss its possible functional importance for the maintenance of lens structure and functions, notably clear and sharp vision.

    Journal of cell science 2003;116;Pt 24;4985-95

  • The DNA sequence and analysis of human chromosome 6.

    Mungall AJ, Palmer SA, Sims SK, Edwards CA, Ashurst JL, Wilming L, Jones MC, Horton R, Hunt SE, Scott CE, Gilbert JG, Clamp ME, Bethel G, Milne S, Ainscough R, Almeida JP, Ambrose KD, Andrews TD, Ashwell RI, Babbage AK, Bagguley CL, Bailey J, Banerjee R, Barker DJ, Barlow KF, Bates K, Beare DM, Beasley H, Beasley O, Bird CP, Blakey S, Bray-Allen S, Brook J, Brown AJ, Brown JY, Burford DC, Burrill W, Burton J, Carder C, Carter NP, Chapman JC, Clark SY, Clark G, Clee CM, Clegg S, Cobley V, Collier RE, Collins JE, Colman LK, Corby NR, Coville GJ, Culley KM, Dhami P, Davies J, Dunn M, Earthrowl ME, Ellington AE, Evans KA, Faulkner L, Francis MD, Frankish A, Frankland J, French L, Garner P, Garnett J, Ghori MJ, Gilby LM, Gillson CJ, Glithero RJ, Grafham DV, Grant M, Gribble S, Griffiths C, Griffiths M, Hall R, Halls KS, Hammond S, Harley JL, Hart EA, Heath PD, Heathcott R, Holmes SJ, Howden PJ, Howe KL, Howell GR, Huckle E, Humphray SJ, Humphries MD, Hunt AR, Johnson CM, Joy AA, Kay M, Keenan SJ, Kimberley AM, King A, Laird GK, Langford C, Lawlor S, Leongamornlert DA, Leversha M, Lloyd CR, Lloyd DM, Loveland JE, Lovell J, Martin S, Mashreghi-Mohammadi M, Maslen GL, Matthews L, McCann OT, McLaren SJ, McLay K, McMurray A, Moore MJ, Mullikin JC, Niblett D, Nickerson T, Novik KL, Oliver K, Overton-Larty EK, Parker A, Patel R, Pearce AV, Peck AI, Phillimore B, Phillips S, Plumb RW, Porter KM, Ramsey Y, Ranby SA, Rice CM, Ross MT, Searle SM, Sehra HK, Sheridan E, Skuce CD, Smith S, Smith M, Spraggon L, Squares SL, Steward CA, Sycamore N, Tamlyn-Hall G, Tester J, Theaker AJ, Thomas DW, Thorpe A, Tracey A, Tromans A, Tubby B, Wall M, Wallis JM, West AP, White SS, Whitehead SL, Whittaker H, Wild A, Willey DJ, Wilmer TE, Wood JM, Wray PW, Wyatt JC, Young L, Younger RM, Bentley DR, Coulson A, Durbin R, Hubbard T, Sulston JE, Dunham I, Rogers J and Beck S

    The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK. ajm@sanger.ac.uk

    Chromosome 6 is a metacentric chromosome that constitutes about 6% of the human genome. The finished sequence comprises 166,880,988 base pairs, representing the largest chromosome sequenced so far. The entire sequence has been subjected to high-quality manual annotation, resulting in the evidence-supported identification of 1,557 genes and 633 pseudogenes. Here we report that at least 96% of the protein-coding genes have been identified, as assessed by multi-species comparative sequence analysis, and provide evidence for the presence of further, otherwise unsupported exons/genes. Among these are genes directly implicated in cancer, schizophrenia, autoimmunity and many other diseases. Chromosome 6 harbours the largest transfer RNA gene cluster in the genome; we show that this cluster co-localizes with a region of high transcriptional activity. Within the essential immune loci of the major histocompatibility complex, we find HLA-B to be the most polymorphic gene on chromosome 6 and in the human genome.

    Nature 2003;425;6960;805-11

  • Identification of a novel Ezrin-binding site in syndecan-2 cytoplasmic domain.

    Granés F, Berndt C, Roy C, Mangeat P, Reina M and Vilaró S

    Department of Cellular Biology, Faculty of Biology, University of Barcelona, Barcelona, Spain.

    ERM (Ezrin/Radixin/Moesin) proteins are crosslinkers between plasma membrane proteins and the actin cytoskeleton, thereby involved in the formation of cell adhesion sites. Earlier work showed that Ezrin links syndecan-2 to the actin cytoskeleton. Here we provide evidence that the Ezrin N-terminal domain binds to the syndecan-2 cytoplasmic domain with an estimated K(D) of 0.71 microM and without the requirement of other proteins. We also studied the regions in the syndecan-2 cytoplasmic domain implicated in the binding to Ezrin. By truncating the syndecan-2 cytoplasmic domain and by oligopeptide competition assays we show that the Ezrin-binding sequence is not located in the positively charged juxtamembrane region (RMRKK), but in the neighboring sequence DEGSYD. We therefore conclude that the consensus sequence for Ezrin binding is unique among membrane proteins, suggesting a distinct regulation.

    FEBS letters 2003;547;1-3;212-6

  • The amino-terminal domains of the ezrin, radixin, and moesin (ERM) proteins bind advanced glycation end products, an interaction that may play a role in the development of diabetic complications.

    McRobert EA, Gallicchio M, Jerums G, Cooper ME and Bach LA

    Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg, 3084 Victoria, Australia.

    The presence of advanced glycation end products (AGEs) formed because of hyperglycemia in diabetic patients has been strongly linked to the development of diabetic complications and disturbances in cellular function. In this report, we describe the isolation and identification of novel AGE-binding proteins from diabetic rat kidneys. The proteins were purified by cation exchange and AGE-modified bovine serum albumin (AGE-BSA) affinity chromatography. NH2-terminal and internal sequencing identified the proteins as the NH2-terminal domains of ezrin, radixin, and moesin (ERM proteins). Using BIAcore biosensor analysis, human N-ezrin-(1-324) bound to immobilized AGE-BSA with a KD of 5.3 +/- 2.1 x 10 -7 m, whereas full-length ezrin-(1-586) and C-ezrin-(323-586) did not bind. Other glycated proteins such as AGE-RNase, N in -carboxymethyllysine (CML)-BSA, and glycated human serum albumin isolated from hyperglycemic diabetic sera competed with the immobilized AGE-BSA for binding to N-ezrin, but non-glycated BSA and RNase did not. Thus N-ezrin binds to AGEs in a glycation- and concentration-dependent manner. Phosphorylated ezrin plays a crucial role in cell shape changes, cell attachment, and cell adhesion. The effect of AGE-BSA on ezrin function was studied in a tubulogenesis model in which LLC-PK1 cell tubule formation is dependent on phosphorylated ezrin. Addition of AGE-BSA completely inhibited the ability of the cells to produce tubules. Furthermore, in vitro tyrosine phosphorylation of N-ezrin and ezrin was also inhibited by AGE-BSA. These proteins represent a novel family of intracellular binding molecules for glycated proteins and provide a potential new target for therapeutic intervention in the prevention or treatment of diabetic complications.

    The Journal of biological chemistry 2003;278;28;25783-9

  • Ca2+-dependent binding and activation of dormant ezrin by dimeric S100P.

    Koltzscher M, Neumann C, König S and Gerke V

    Institute for Medical Biochemistry, University of Muenster, Germany.

    S100 proteins are EF hand type Ca2+ binding proteins thought to function in stimulus-response coupling by binding to and thereby regulating cellular targets in a Ca2+-dependent manner. To isolate such target(s) of the S100P protein we devised an affinity chromatography approach that selects for S100 protein ligands requiring the biologically active S100 dimer for interaction. Hereby we identify ezrin, a membrane/F-actin cross-linking protein, as a dimer-specific S100P ligand. S100P-ezrin complex formation is Ca2+ dependent and most likely occurs within cells because both proteins colocalize at the plasma membrane after growth factor or Ca2+ ionophore stimulation. The S100P binding site is located in the N-terminal domain of ezrin and is accessible for interaction in dormant ezrin, in which binding sites for F-actin and transmembrane proteins are masked through an association between the N- and C-terminal domains. Interestingly, S100P binding unmasks the F-actin binding site, thereby at least partially activating the ezrin molecule. This identifies S100P as a novel activator of ezrin and indicates that activation of ezrin's cross-linking function can occur directly in response to Ca2+ transients.

    Molecular biology of the cell 2003;14;6;2372-84

  • Upregulated expression of Ezrin and invasive phenotype in malignantly transformed esophageal epithelial cells.

    Shen ZY, Xu LY, Chen MH, Li EM, Li JT, Wu XY and Zeng Y

    Department of Pathology, Medical College of Shantou University, Shantou 515031, Guangdong Province, China. zhongyingshen@yahoo.com

    Aim: To investigate the correlation between ezrin expression and invasive phenotype formation in malignantly transformed esophageal epithelial cells.

    Methods: The experimental cell line employed in the present study was originated form the progressive induction of a human embryonic esophageal epithelial cell line (SHEE) by the E6E7 genes of human papillomavirus (HPV) type 18. The cells at the 35(th) passage after induction called SHEEIMM were in a state of immortalized phase and used as the control, while that of the 85(th) passage denominated as SHEEMT represented the status of cells that were malignantly transformed. The expression changes of ezrin and its mRNA in both cell passages were respectively analyzed by RT-PCR and Western blot. Invasive phenotype was assessed in vivo by inoculating these cells into the severe combined immunodeficient (SCID) mice via subcutaneous and intraperitoneal injection, and in vitro by inoculating them on the surface of the amnion membranes, which then was determined by light microscopy and scanning electron microscopy.

    Results: Upregulated expression of ezrin protein and its mRNA was observed in SHEEMT compared with that in SHEEIMM cells. The SHEEMT cells inoculated in SCID mice were observed forming tumor masses in both visceral organs and soft tissues in a period of 40 days with a special propensity to invading mesentery and pancreas, but did not exhibit hepatic metastases. Pathologically, these tumor cells harboring larger nucleus, nucleolus and less cytoplasm could infiltrate and destroy adjacent tissues. In the in vitro study, the inoculated SHEEMT cells could grow in cluster on the amniotic epithelial surface and intrude into the amniotic stroma. In contrast, unrestricted growth and invasiveness were not found in SHEEIMM cells in both in vivo and in vitro experiment.

    Conclusion: The upregulated ezrin expression is one of the important factors that are possibly associated with the invasive phenotype formation in malignantly transformed esophageal epithelial cells.

    World journal of gastroenterology 2003;9;6;1182-6

  • The role of the CD44/ezrin complex in cancer metastasis.

    Martin TA, Harrison G, Mansel RE and Jiang WG

    Metastasis Research Group, University Department of Surgery, University of Wales College of Medicine, Heath Park, Cardiff, S. Wales CF14 4XN, UK. martinta1@cf.ac.uk

    CD44 is a cell adhesion molecule that was traditionally known as 'homing receptor'. This molecule is known to interact with the ezrin family (ERM family) members and form a complex that plays diverse roles within both normal and abnormal cells, particularly cancer cells. CD44 and ezrin and their respective complex have properties suggesting that they may be important in the process of tumour-endothelium interactions, cell migrations, cell adhesion, tumour progression and metastasis. This article reviews the role of CD44, ezrin family and the CD44/ezrin complex in cancer cells and their clinical impact in patients with cancer.

    Critical reviews in oncology/hematology 2003;46;2;165-86

  • Increased ezrin expression and activation by CDK5 coincident with acquisition of the senescent phenotype.

    Yang HS and Hinds PW

    Department of Pathology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.

    Passage of normal cells in culture leads to senescence, an irreversible cell cycle exit characterized by biochemical changes and a distinctive morphology. Cellular stresses, including oncogene activation, can also lead to senescence. Consistent with an anti-oncogenic role for this process, the tumor suppressor pRb plays a critical role in senescence. Reexpression of pRb in human tumor cells results in senescence-like changes including cell cycle exit and shape changes. Here we show that senescence is accompanied by increased expression and altered localization of ezrin, an actin binding protein involved in membrane-cytoskeletal signaling. pRb expression results in the stimulation of CDK5-mediated phosphorylation of ezrin with subsequent membrane association and induction of cell shape changes, linking pRb activity to cytoskeletal regulation in senescent cells.

    Funded by: NIA NIH HHS: AG20208

    Molecular cell 2003;11;5;1163-76

  • PACE-1, a novel protein that interacts with the C-terminal domain of ezrin.

    Sullivan A, Uff CR, Isacke CM and Thorne RF

    Ludwig Institute for Cancer Research, Imperial College Faculty of Medicine, St Mary's Campus, Norfolk Place, London, W2 1PG, UK.

    The ERM proteins (ezrin, radixin, moesin) together with merlin comprise a subgroup of the band 4.1 superfamily. These proteins act as membrane cytoskeletal linker proteins mediating interactions between the cytoplasmic domains of transmembrane proteins and actin. To better understand how the ERM proteins function to regulate these junctional complexes, a yeast 2-hybrid screen was undertaken using ezrin as a bait. We describe here the identification and cloning of a novel protein, PACE-1, which binds to the C-terminal domain of ezrin. Characterization of PACE-1 in human breast cancer cell lines demonstrates it to have two distinct intracellular localizations. A proportion of the protein is associated with the cytoplasmic face of the Golgi apparatus. This distribution is dependent upon the presence of the PACE-1 N-terminal myristoylation consensus sequence but is not dependent on an association with ezrin. In contrast, PACE-1 colocalises with ezrin in the lamellipodia, where ezrin has a role in cell spreading and motility. A notable feature of PACE-1 is the presence of a putative N-terminal kinase domain; however, in biochemical assays PACE-1 was shown to have associated rather than intrinsic kinase activity. Together these data suggest that PACE-1 may play a role in regulating cell adhesion/migration complexes in migrating cells.

    Experimental cell research 2003;284;2;224-38

  • The size of the synaptic cleft and distinct distributions of filamentous actin, ezrin, CD43, and CD45 at activating and inhibitory human NK cell immune synapses.

    McCann FE, Vanherberghen B, Eleme K, Carlin LM, Newsam RJ, Goulding D and Davis DM

    Department of Biological Sciences, Imperial College, London, United Kingdom.

    In this study, we report the organization of cytoskeletal and large transmembrane proteins at the inhibitory and activating NK cell immunological or immune synapse (IS). Filamentous actin accumulates at the activating, but not the inhibitory, NK cell IS. However, surprisingly, ezrin and the associated protein CD43 are excluded from the inhibitory, but not the activating, NK cell IS. This distribution of ezrin and CD43 at the inhibitory NK cell IS is similar to that previously seen at the activating T cell IS. CD45 is also excluded from the inhibitory, but not activating, NK cell IS. In addition, electron microscopy reveals wide and narrow domains across the synaptic cleft. Target cell HLA-C, located by immunogold labeling, clusters where the synaptic cleft spans the size of HLA-C bound to the inhibitory killer Ig-like receptor. These data are consistent with assembly of the NK cell IS involving a combination of cytoskeletal-driven mechanisms and thermodynamics favoring the organization of receptor/ligand pairs according to the size of their extracellular domains.

    Journal of immunology (Baltimore, Md. : 1950) 2003;170;6;2862-70

  • Structure of the active N-terminal domain of Ezrin. Conformational and mobility changes identify keystone interactions.

    Smith WJ, Nassar N, Bretscher A, Cerione RA and Karplus PA

    Department of Chemistry, Cornell University, Ithaca, New York 14853, USA.

    Ezrin is a member of the ERM (ezrin, radixin, moesin) family of proteins that cross-link the actin cytoskeleton to the plasma membrane and also may function in signaling cascades that regulate the assembly of actin stress fibers. Here, we report a crystal structure for the free (activated) FERM domain (residues 2-297) of recombinant human ezrin at 2.3 A resolution. Structural comparison among the dormant moesin FERM domain structure and the three known active FERM domain structures (radixin, moesin, and now ezrin) allows the clear definition of regions that undergo structural changes during activation. The key regions affected are residues 135-150 and 155-180 in lobe F2 and residues 210-214 and 235-267 in lobe F3. Furthermore, we show that a large increase in the mobilities of lobes F2 and F3 accompanies activation, suggesting that their integrity is compromised. This leads us to propose a new concept that we refer to as keystone interactions. Keystone interactions occur when one protein (or protein part) contributes residues that allow another protein to complete folding, meaning that it becomes an integral part of the structure and would rarely dissociate. Such interactions are well suited for long-lived cytoskeletal protein interactions. The keystone interactions concept leads us to predict two specific docking sites within lobes F2 and F3 that are likely to bind target proteins.

    Funded by: NIGMS NIH HHS: 2 R01 GM40654, GM07273, GM36652

    The Journal of biological chemistry 2003;278;7;4949-56

  • Ezrin is a substrate for Lck in T cells.

    Autero M, Heiska L, Rönnstrand L, Vaheri A, Gahmberg CG and Carpén O

    Department of Biosciences, Division of Biochemistry, University of Helsinki, Helsinki, Finland.

    We evaluated the role of Lck tyrosine kinase, an early effector of T cell activation, in regulation of the membrane-cytoskeleton linker protein ezrin. Ezrin was constitutively tyrosine phosphorylated in wild-type and CD45-deficient Jurkat T cells, but not in Lck-deficient cells. However, phosphorylation was evident in cells, in which Lck activity had been restored by transfection. Phosphorylation was reduced by the Src family kinase inhibitor PP2 and increased by the tyrosine phosphatase inhibitor pervanadate, implying continuous tyrosine phosphorylation and dephosphorylation. Lck phosphorylated ezrin in vitro, and the major phosphotyrosine was identified as Y145. These results identify ezrin as the first cytoskeletal substrate for Lck.

    FEBS letters 2003;535;1-3;82-6

  • Differential expression and distribution of ezrin, radixin and moesin in human natural killer cells.

    Ramoni C, Luciani F, Spadaro F, Lugini L, Lozupone F and Fais S

    Laboratory of Immunology, Istituto Superiore di Sanità, Rome, Italy.

    Cytoskeleton plays a crucial role in natural killer cell function. In this study the expression and subcellular distribution of ezrin, radixin and moesin, a family of proteins that connect actin filaments to many membrane structures, were evaluated in human NK cells. The results showed that NK cells expressed all these proteins, while NK cell-deprived peripheral blood leukocytes and purified T lymphocytes did not express radixin. Only ezrin changed its distribution following IL-2 activation and all three ezrin, moesin and radixin were polarized on uropods of adherent natural killer cells. Ezrin and radixin co-localized with the perforin granules at the intimate sites of contact between NK and the target cells, while moesin remains uniformly distributed on the membrane of NK cells. Ezrin, radixin and perforin co-localization was undetected in non-lytic conjugates and inhibited by treatment with actin depolymerizing agents. These results suggest that ezrin and radixin may exert a role in NK activity, particularly in the trafficking of perforin granules to the NK/target cells contact site. Moreover, our data suggest that radixin may represent an additional biological marker of human NK cells and that this protein may hold a specific role in NK cell function.

    European journal of immunology 2002;32;11;3059-65

  • Distribution and expression of CD44 isoforms and Ezrin during prostate cancer-endothelium interaction.

    Harrison GM, Davies G, Martin TA, Jiang WG and Mason MD

    Metastasis Research Group, Department of Surgery, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, Wales, UK. harrisonGM@cf.ac.uk

    CD44 is a multifunctional cell surface adhesion molecule that has been implicated in tumour cell invasion and metastasis. Many cancer cell types as well as their metastases express high levels of CD44. Furthermore, the expression of certain CD44 variants has been linked with metastasis and tumour progression. It is known that ezrin, a member of the ERM family of proteins, can bind to CD44 and thus raises the possibility that it is involved in cell migration and metastasis. Therefore we examined the expression and distribution of CD44, its co-localisation and translocation with ezrin in prostate cancer cell lines as they interact with endothelial cells. Experimental results indicate prostate cancer cells express multiple CD44 isoforms that co-localise with ezrin in DU-145 and PC-3 prostate cancer cells. Treatment with hepatocyte growth factor (HGF/SF) resulted in up-regulation of CD44 and its co-translocation with ezrin during tumour-endothelial cell interactions. In addition, tumour cell adhesion to endothelial cells and their invasiveness was increased after exposure to HGF/SF, and can be blocked by the presence of anti-CD44 antibodies. It is concluded that CD44 and ezrin interact in endothelial cells and that they co-localise in the areas of tumour-endothelial contact. The CD44/ezrin complex plays a pivotal role in the capture and invasion of endothelial cells by prostate cancer cells.

    International journal of oncology 2002;21;5;935-40

  • Molecular analysis of microscopic ezrin dynamics by two-photon FRAP.

    Coscoy S, Waharte F, Gautreau A, Martin M, Louvard D, Mangeat P, Arpin M and Amblard F

    Laboratoires de Physico-Chimie,Unité Mixte de Recherche 168 and Morphogenèse et Signalisation Cellulaires, Unité Mixte de Recherche 144, Centre National de la Recherche Scientifique/Institut Curie, 26, Rue d'Ulm, 75248 Paris Cedex 05, France.

    Ezrin plays a key role in coupling signal transduction to cortical cell organization. This actin-membrane linker undergoes a series of conformational changes that modulate its interactions with various partners and its localization in membrane or cytosolic pools. Its mobility and exchange rates within and between these two pools were assessed by two-photon fluorescence recovery after photobleaching in epithelial cell microvilli. Analysis of ezrin mutants with an altered actin-binding site revealed three ezrin membrane states of different mobilities and exchange properties, reflecting sequential association with membrane components and F-actin in the context of a fast overall turnover.

    Proceedings of the National Academy of Sciences of the United States of America 2002;99;20;12813-8

  • Dmoesin controls actin-based cell shape and polarity during Drosophila melanogaster oogenesis.

    Polesello C, Delon I, Valenti P, Ferrer P and Payre F

    Centre de Biologie du Dévelopement, UMR 5547 CNRS, Bat4R3, 118 route de Narbonne, Toulouse, 31062 CEDEX4, France.

    Ezrin, Radixin and Moesin (ERM) proteins are thought to constitute a bridge between the actin cytoskeleton and the plasma membrane (PM). Here we report a genetic analysis of Dmoesin, the sole member of the ERM family in Drosophila. We show that Dmoesin is required during oogenesis for anchoring microfilaments to the oocyte cortex. Alteration of the actin cytoskeleton resulting from Dmoesin mutations impairs the localization of maternal determinants, thus disrupting antero-posterior polarity. This study also demonstrates the requirement of Dmoesin for the specific organization of cortical microfilaments in nurse cells and, consequently, mutations in Dmoesin produce severe defects in cell shape.

    Nature cell biology 2002;4;10;782-9

  • ITAM-based interaction of ERM proteins with Syk mediates signaling by the leukocyte adhesion receptor PSGL-1.

    Urzainqui A, Serrador JM, Viedma F, Yáñez-Mó M, Rodríguez A, Corbí AL, Alonso-Lebrero JL, Luque A, Deckert M, Vázquez J and Sánchez-Madrid F

    Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain.

    P-selectin glycoprotein ligand 1 (PSGL-1) is a leukocyte adhesion molecule involved in cell tether and rolling on activated endothelium. Our work shows that PSGL-1 associates with Syk. This association is mediated by the actin-linking proteins moesin and ezrin, which directly interact with Syk in an ITAM-dependent manner. PSGL-1 engagement induces tyrosine phosphorylation of Syk and SRE-dependent transcriptional activity. Treatment of cells with the Syk inhibitor piceatannol and overexpression of either a Syk dead kinase mutant or an ITAM-mutated moesin abrogated PSGL-1-induced transcriptional activation. These data unveil a new functional role for the ERMs (ezrin/radixin/moesin) as adaptor molecules in the interactions of adhesion receptors and intracellular tyrosine kinases and show that PSGL-1 is a signaling molecule in leukocytes.

    Immunity 2002;17;4;401-12

  • The adenosine 2b receptor is recruited to the plasma membrane and associates with E3KARP and Ezrin upon agonist stimulation.

    Sitaraman SV, Wang L, Wong M, Bruewer M, Hobert M, Yun CH, Merlin D and Madara JL

    Division of Digestive Diseases, Department of Medicine, Emory University, Atlanta, Georgia 30322, USA. ssitar2@emory.edu

    We have previously shown that adenosine is formed in the intestinal lumen during active inflammation from neutrophil-derived 5'-AMP. Acting through the adenosine A2b receptor (A2bR), the luminally derived adenosine induces vectorial chloride secretion and a polarized secretion of interleukin-6 to the intestinal lumen. Although some G protein-coupled receptors interact with anchoring or signaling molecules, not much is known in this critical area for the A2bR. We used the model intestinal epithelial cell line, T84, and Caco2-BBE cells stably transfected with GFP-A2b receptor to study the intestinal A2bR. The A2bR is present in both the apical and basolateral membranes of intestinal epithelia. Apical or basolateral stimulation of the A2bR induces recruitment of the receptor to the plasma membrane and caveolar fractions. The A2bR co-immunoprecipitates with E3KARP and ezrin upon agonist stimulation. Ezrin interacts with E3KARP and PKA and the interaction between ezrin and E3KARP is enhanced by agonist stimulation. Our data suggest that the A2bR is recruited to the plasma membrane upon apical or basolateral agonist stimulation and interacts with E3KARP and ezrin. We speculate that such an interaction may not only anchor the A2bR to the plasma membrane but may also function to stabilize the receptor in a signaling complex in the plasma membrane.

    Funded by: NIDDK NIH HHS: DK 35932, DK 47662, K01 DK 02831, K08 DK02802

    The Journal of biological chemistry 2002;277;36;33188-95

  • Ezrin and moesin expression within the developing human cerebrum and tuberous sclerosis-associated cortical tubers.

    Johnson MW, Miyata H and Vinters HV

    Section of Neuropathology, Department of Pathology and Laboratory Medicine (Neuropathology), UCLA Medical Center, Los Angeles, CA 90095-1732, USA.

    The ERM (ezrin, radixin, and moesin) proteins belong to the band-4.1 superfamily of membrane-cytoskeleton-linking proteins which bind to the actin cytoskeleton via their C-terminal sequences and bind ERM binding membrane proteins (ERMBMPs). We investigated the immunohistochemical expression of two of the ERM proteins (ezrin and moesin) in developing human cerebral cortex and in cortical tubers from patients with tuberous sclerosis (TSC), to assess possible consequences of TSC gene product malfunction or inactivation in the developing brain in relation to ERM protein expression. Ezrin is abundantly expressed within radial glia and migrating cells in the intermediate zone in the prenatal human cerebrum, while moesin is primarily expressed in vascular endothelial cells in developing and adult human brain and scattered microglia in adult brain. In addition, both ezrin and moesin are abundantly co-expressed with hamartin and tuberin within a population of abnormal cells in TSC-associated cortical tubers. The expression of these two proteins--primarily ezrin--suggests that they are developmentally regulated and abundantly expressed in germinal matrix and/or migrating cells during cerebral cortical development. In TSC-associated cortical tubers, both proteins appeared to be up-regulated and are co-localized within a population of abnormal neuroglial cells typical of those seen in tubers. Expression of these proteins and their co-localization with tuberin and hamartin in these cells may suggest a compensatory up-regulation in response to TSC gene mutation.

    Acta neuropathologica 2002;104;2;188-96

  • Dynamic interaction of VCAM-1 and ICAM-1 with moesin and ezrin in a novel endothelial docking structure for adherent leukocytes.

    Barreiro O, Yanez-Mo M, Serrador JM, Montoya MC, Vicente-Manzanares M, Tejedor R, Furthmayr H and Sanchez-Madrid F

    Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.

    Ezrin, radixin, and moesin (ERM) regulate cortical morphogenesis and cell adhesion by connecting membrane adhesion receptors to the actin-based cytoskeleton. We have studied the interaction of moesin and ezrin with the vascular cell adhesion molecule (VCAM)-1 during leukocyte adhesion and transendothelial migration (TEM). VCAM-1 interacted directly with moesin and ezrin in vitro, and all of these molecules colocalized at the apical surface of endothelium. Dynamic assessment of this interaction in living cells showed that both VCAM-1 and moesin were involved in lymphoblast adhesion and spreading on the endothelium, whereas only moesin participated in TEM, following the same distribution pattern as ICAM-1. During leukocyte adhesion in static or under flow conditions, VCAM-1, ICAM-1, and activated moesin and ezrin clustered in an endothelial actin-rich docking structure that anchored and partially embraced the leukocyte containing other cytoskeletal components such as alpha-actinin, vinculin, and VASP. Phosphoinositides and the Rho/p160 ROCK pathway, which participate in the activation of ERM proteins, were involved in the generation and maintenance of the anchoring structure. These results provide the first characterization of an endothelial docking structure that plays a key role in the firm adhesion of leukocytes to the endothelium during inflammation.

    The Journal of cell biology 2002;157;7;1233-45

  • Functional binding interaction identified between the axonal CAM L1 and members of the ERM family.

    Dickson TC, Mintz CD, Benson DL and Salton SR

    Fishberg Research Center for Neurobiology, The Mount Sinai School of Medicine, New York, NY 10029, USA.

    A yeast two-hybrid library was screened using the cytoplasmic domain of the axonal cell adhesion molecule L1 to identify binding partners that may be involved in the regulation of L1 function. The intracellular domain of L1 bound to ezrin, a member of the ezrin, radixin, and moesin (ERM) family of membrane-cytoskeleton linking proteins, at a site overlapping that for AP2, a clathrin adaptor. Binding of bacterial fusion proteins confirmed this interaction. To determine whether ERM proteins interact with L1 in vivo, extracellular antibodies to L1 were used to force cluster the protein on cultured hippocampal neurons and PC12 cells, which were then immunolabeled for ERM proteins. Confocal analysis revealed a precise pattern of codistribution between ERMs and L1 clusters in axons and PC12 neurites, whereas ERMs in dendrites and spectrin labeling remained evenly distributed. Transfection of hippocampal neurons grown on an L1 substrate with a dominant negative ERM construct resulted in extensive and abnormal elaboration of membrane protrusions and an increase in axon branching, highlighting the importance of the ERM-actin interaction in axon development. Together, our data indicate that L1 binds directly to members of the ERM family and suggest this association may coordinate aspects of axonal morphogenesis.

    Funded by: NCRR NIH HHS: S10 RR0 9145; NIAAA NIH HHS: AA12971, R01 AA014898, R21 AA012971, R21 AA012971-01, R21 AA012971-02, R21 AA012971-03

    The Journal of cell biology 2002;157;7;1105-12

  • A novel PKC-regulated mechanism controls CD44 ezrin association and directional cell motility.

    Legg JW, Lewis CA, Parsons M, Ng T and Isacke CM

    Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK.

    The dynamic assembly and disassembly of membrane cytoskeleton junctional complexes is critical in cell migration. Here we describe a novel phosphorylation mechanism that regulates the hyaluronan receptor CD44. In resting cells, CD44 is constitutively phosphorylated at a single serine residue, Ser325. After protein kinase C is activated, a switch in phosphorylation results in CD44 being phosphorylated solely at an alternative residue, Ser291. Using fluorescence resonance energy transfer (FRET) monitored by fluorescence lifetime imaging microscopy (FLIM) and chemotaxis assays we show that phosphorylation of Ser291 modulates the interaction between CD44 and the cytoskeletal linker protein ezrin in vivo, and that this phosphorylation is critical for CD44-dependent directional cell motility.

    Nature cell biology 2002;4;6;399-407

  • A novel serine-rich motif in the intercellular adhesion molecule 3 is critical for its ezrin/radixin/moesin-directed subcellular targeting.

    Serrador JM, Vicente-Manzanares M, Calvo J, Barreiro O, Montoya MC, Schwartz-Albiez R, Furthmayr H, Lozano F and Sánchez-Madrid F

    Servicio de Inmunologia, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid 28006, Spain.

    Intercellular adhesion molecule 3 (ICAM-3) is a leukocyte-specific receptor involved in primary immune responses. We have investigated the interaction between ICAM-3 and ezrin/radixin/moesin (ERM) proteins and its role in LFA-1-induced cell-cell interactions and membrane positioning of ICAM-3 in polarized migrating lymphocytes. Protein-protein binding assays demonstrated a phosphatidylinositol 4,5-bisphosphate-induced association between ICAM-3 and the amino-terminal domain of ERM proteins. This interaction was not essential for the binding of ICAM-3 to LFA-1. Dynamic fluorescence videomicroscopy studies of cells demonstrated that moesin and ICAM-3 coordinately redistribute on the plasma membrane during lymphocyte migration. Furthermore, overexpression of the amino-terminal domain of moesin, which lacks the consensus moesin actin-binding site, caused the subcellular mislocalization of ICAM-3. A CD4 chimerical protein containing the cytoplasmic tail of ICAM-3 was targeted to the trailing edge. Point mutation of Ser(487), Ser(489), and Ser(496) to alanine in the juxtamembrane region of ICAM-3 significantly impaired both ERM binding and polarization of ICAM-3. ERM-directed polarization of ICAM-3 was also impaired by phosphorylation-like mutation of Ser(487) and Ser(489), but not of Ser(496). Our results underscore the key role of specific serine residues within the cytoplasmic region of ICAM-3 for its ERM-directed positioning at the trailing edge of motile lymphocytes.

    The Journal of biological chemistry 2002;277;12;10400-9

  • The cytoplasmic tail of L-selectin interacts with members of the Ezrin-Radixin-Moesin (ERM) family of proteins: cell activation-dependent binding of Moesin but not Ezrin.

    Ivetic A, Deka J, Ridley A and Ager A

    Divisions of Cellular Immunology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom.

    L-selectin regulates the recruitment of naive lymphocytes from the bloodstream to secondary lymphoid organs, mediating their initial capture and subsequent rolling along high endothelial cell surface-expressed ligands in peripheral lymph nodes. In vivo, distribution of L-selectin and cell surface levels determine the tethering efficiency and rolling velocity of leukocytes, respectively. Treatment of naive lymphocytes with phorbol myristate acetate (PMA) induces rapid ectodomain proteolytic down-regulation (shedding) of surface L-selectin via a protein kinase C (PKC)-dependent pathway. In an attempt to isolate proteins that are involved in regulating L-selectin expression, an affinity column was constructed using the 17-amino acid cytoplasmic tail of L-selectin. Affinity purification of extracts from lymphocytes, pre-treated with or without PMA, allowed identification of proteins that interact with the affinity column under one condition but not the other. By using this approach, members of the Ezrin-Radixin-Moesin family of proteins were found to interact specifically with the cytoplasmic tail of L-selectin. Moesin from PMA-stimulated lymphocytes, but not from unstimulated lymphocytes, bound to L-selectin tail. In contrast, ezrin from unstimulated or PMA-stimulated lymphocytes associated with L-selectin tail with equal affinity. Furthermore, the PKC inhibitor Ro 31-8220 significantly reduced the interaction of moesin, but not ezrin, with L-selectin. Alanine mutations of membrane-proximal basic amino acid residues in the cytoplasmic domain of L-selectin identified arginine 357 as a critical residue for both ezrin and moesin interaction. Finally, BIAcore affinity analysis confirmed that N-terminal moesin interacts specifically with L-selectin cytoplasmic tail, with relatively high affinity (K(d) approximately 40 nm). Based on these findings, although moesin and ezrin bind to a similar region of the cytoplasmic tail of L-selectin, moesin binding is dependent on PKC activation, which suggests that ezrin and moesin are regulated differently in lymphocytes.

    The Journal of biological chemistry 2002;277;3;2321-9

  • Polarity and developmental regulation of two PDZ proteins in the retinal pigment epithelium.

    Bonilha VL and Rodriguez-Boulan E

    Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.

    Purpose: Identification of binding partners for ezrin, an actin-binding protein crucial for morphogenesis of apical microvilli and basolateral infoldings in RPE cells.

    Methods: Rat eyes, rat primary RPE, the rat RPE-J cell line, and a clonal line of RPE-J cells transfected with human ezrin cDNA were analyzed by immunofluorescence microscopy and immunoblot. Immunofluorescence localization of two ezrin-binding proteins was performed in cryosections of rat eyes of various ages and in monolayers extracted with the detergent Triton X-100 and fixed in paraformaldehyde. The interaction of both proteins with ezrin and gluthathione-S-transferase (GST)-ezrin fusion proteins was analyzed by SDS-PAGE and immunoblot.

    Results: Immunofluorescence microscopy of adult rat eyes detected a polarized distribution of ERM (ezrin, radixin, and moesin)-binding phosphoprotein of 50 kDa (EBP50) at the apical microvilli and synaptic-associated protein of 97 kDa (SAP97) at the basolateral surface of RPE cells, which overlapped with ezrin. These two PDZ (postsynaptic density protein [PSD-95]/disc large [DLG]-A/ZO-1) domain proteins had a similar polarized distribution and high resistance to detergent extractability, indicative of cytoskeletal association, both in primary cultures of rat RPE and in a clonal RPE-J cell line expressing high levels of transfected ezrin. RPE cell lysates from rat retinas of various postnatal ages revealed increasing levels of EBP50 and SAP97 compared with alphav integrin, a protein expressed at constant adult levels from birth. GST pull-down and immunoprecipitation experiments demonstrated a direct interaction between EBP50 and SAP97 and ezrin.

    Conclusions: The data indicate that EBP50 localizes at the apical microvilli, whereas SAP97 localizes at the basolateral surface of RPE cells, probably through a direct interaction with ezrin.

    Funded by: NEI NIH HHS: EY 08538, R01 EY008538

    Investigative ophthalmology & visual science 2001;42;13;3274-82

  • Interaction between two adapter proteins, PAG and EBP50: a possible link between membrane rafts and actin cytoskeleton.

    Brdicková N, Brdicka T, Andera L, Spicka J, Angelisová P, Milgram SL and Horejsí V

    Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague. nada@leuko.biomed.cas.cz

    Phosphoprotein associated with GEMs (PAG), also known as Csk-binding protein (Cbp), is a broadly expressed palmitoylated transmembrane adapter protein found in membrane rafts, also called GEMs (glycosphingolipid-enriched membrane microdomains). PAG is known to bind and activate the essential regulator of Src-family kinases, cytoplasmic protein tyrosine kinase Csk. In the present study we used the yeast 2-hybrid system to search for additional proteins which might bind to PAG. We have identified the abundant cytoplasmic adapter protein EBP50 (ezrin/radixin/moesin (ERM)-binding phosphoprotein of 50 kDa), also known as NHERF (Na(+)/H(+) exchanger regulatory factor), as a specific PAG-binding partner. The interaction involves the C-terminal sequence (TRL) of PAG and N-terminal PDZ domain(s) of EBP50. As EBP50 is known to interact via its C-terminal domain with the ERM-family proteins, which in turn bind to actin cytoskeleton, the PAG-EBP50 interaction may be important for connecting membrane rafts to the actin cytoskeleton.

    Funded by: NHLBI NIH HHS: HL63755

    FEBS letters 2001;507;2;133-6

  • Ezrin interacts with focal adhesion kinase and induces its activation independently of cell-matrix adhesion.

    Poullet P, Gautreau A, Kadaré G, Girault JA, Louvard D and Arpin M

    Laboratoire de Morphogenèse et Signalisation Cellulaires, UMR 144 CNRS/Institut Curie, 26 rue d'Ulm, Paris 75248, cedex 05, France.

    Ezrin, a membrane-cytoskeleton linker, is required for cell morphogenesis, motility, and survival through molecular mechanisms that remain to be elucidated. Using the N-terminal domain of ezrin as a bait, we found that p125 focal adhesion kinase (FAK) interacts with ezrin. We show that the two proteins coimmunoprecipitate from cultured cell lysates. However, FAK does not interact with full-length ezrin in vitro, indicating that the FAK binding site on ezrin is cryptic. Mapping experiments showed that the entire N-terminal domain of FAK (amino acids 1-376) is required for optimal ezrin binding. While investigating the role of the ezrin-FAK interaction, we observed that, in suspended kidney-derived epithelial LLC-PK1 cells, overproduction of ezrin promoted phosphorylation of FAK Tyr-397, the major autophosphorylation site, creating a docking site for FAK signaling partners. Treatment of the cells with a Src family kinase inhibitor reduced the phosphorylation of Tyr-577 but not that of Tyr-397, indicating that ezrin-mediated FAK activation does not require the activity of Src kinases. Altogether, these observations indicate that ezrin is able to trigger FAK activation in signaling events that are not elicited by cell-matrix adhesion.

    The Journal of biological chemistry 2001;276;40;37686-91

  • Characterization of human palladin, a microfilament-associated protein.

    Mykkänen OM, Grönholm M, Rönty M, Lalowski M, Salmikangas P, Suila H and Carpén O

    Department of Pathology, Helsinki University Hospital University of Helsinki, FIN-00014 Helsinki, Finland.

    Actin-containing microfilaments control cell shape, adhesion, and contraction. In striated muscle, alpha-actinin and other Z-disk proteins coordinate the organization and functions of actin filaments. In smooth muscle and nonmuscle cells, periodic structures termed dense bodies and dense regions, respectively, are thought to serve functions analogous to Z-discs. We describe here identification and characterization of human palladin, a protein expressed mainly in smooth muscle and nonmuscle and distributed along microfilaments in a periodic manner consistent with dense regions/bodies. Palladin contains three Ig-domains most homologous to the sarcomeric Z-disk protein myotilin. The N terminus includes an FPPPP motif recognized by the Ena-Vasp homology domain 1 domain in Ena/vasodilatator-stimulated phosphoprotein (VASP)/Wiscott-Aldrich syndrome protein (WASP) protein family. Cytoskeletal proteins with FPPPP motif target Ena/VASP/WASP proteins to sites of actin modulation. We identified palladin in a yeast two-hybrid search as an ezrin-associated protein. An interaction between palladin and ezrin was further verified by affinity precipitation and blot overlay assays. The interaction was mediated by the alpha-helical domain of ezrin and by Ig-domains 2-3 of palladin. Ezrin is typically a component of the cortical cytoskeleton, but in smooth muscle cells it is localized along microfilaments. These cells express palladin abundantly and thus palladin may be involved in the microfilament localization of ezrin. Palladin expression was up-regulated in differentiating dendritic cells (DCs), coinciding with major cytoskeletal and morphological alterations. In immature DCs, palladin localized in actin-containing podosomes and in mature DCs along actin filaments. The regulated expression and localization suggest a role for palladin in the assembly of DC cytoskeleton.

    Molecular biology of the cell 2001;12;10;3060-73

  • Ezrin, radixin, and moesin are components of Schwann cell microvilli.

    Scherer SS, Xu T, Crino P, Arroyo EJ and Gutmann DH

    Department of Neurology, The University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104-6077, USA. sscherer@mail.med.upenn.edu

    Ezrin, radixin, and moesin (ERM proteins), as well as the neurofibromatosis 2 (NF2) tumor suppressor merlin/schwannomin, all belong to the protein 4.1 family, yet only merlin is a tumor suppressor in Schwann cells. To gain insight into the possible functions of ERM proteins in Schwann cells, we examined their localization in peripheral nerve, because we have previously shown that merlin is found in paranodes and in Schmidt-Lanterman incisures. All three ERM proteins were highly expressed in the microvilli of myelinating Schwann cells that surround the nodal axolemma as well as in incisures and cytoplasmic puncta in the vicinity of the node. In all of these locations, ERM proteins were colocalized with actin filaments. In contrast, ERM proteins did not surround nodes in the CNS. The colocalization of ERM proteins with actin indicates that they have functions different from those of merlin in myelinating Schwann cells.

    Funded by: NINDS NIH HHS: NS08075, NS34528, NS35848, NS37100

    Journal of neuroscience research 2001;65;2;150-64

  • Ezrin is a downstream effector of trafficking PKC-integrin complexes involved in the control of cell motility.

    Ng T, Parsons M, Hughes WE, Monypenny J, Zicha D, Gautreau A, Arpin M, Gschmeissner S, Verveer PJ, Bastiaens PI and Parker PJ

    Richard Dimbleby Department of Cancer Research, St Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK. T.Ng@icrf.icnet.uk

    Protein kinase C (PKC) alpha has been implicated in beta1 integrin-mediated cell migration. Stable expression of PKCalpha is shown here to enhance wound closure. This PKC-driven migratory response directly correlates with increased C-terminal threonine phosphorylation of ezrin/moesin/radixin (ERM) at the wound edge. Both the wound migratory response and ERM phosphorylation are dependent upon the catalytic function of PKC and are susceptible to inhibition by phosphatidylinositol 3-kinase blockade. Upon phorbol 12,13-dibutyrate stimulation, green fluorescent protein-PKCalpha and beta1 integrins co-sediment with ERM proteins in low-density sucrose gradient fractions that are enriched in transferrin receptors. Using fluorescence lifetime imaging microscopy, PKCalpha is shown to form a molecular complex with ezrin, and the PKC-co-precipitated endogenous ERM is hyperphosphorylated at the C-terminal threonine residue, i.e. activated. Electron microscopy showed an enrichment of both proteins in plasma membrane protrusions. Finally, overexpression of the C-terminal threonine phosphorylation site mutant of ezrin has a dominant inhibitory effect on PKCalpha-induced cell migration. We provide the first evidence that PKCalpha or a PKCalpha-associated serine/threonine kinase can phosphorylate the ERM C-terminal threonine residue within a kinase-ezrin molecular complex in vivo.

    The EMBO journal 2001;20;11;2723-41

  • Identification of EPI64, a TBC/rabGAP domain-containing microvillar protein that binds to the first PDZ domain of EBP50 and E3KARP.

    Reczek D and Bretscher A

    Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.

    The cortical scaffolding proteins EBP50 (ERM-binding phosphoprotein-50) and E3KARP (NHE3 kinase A regulatory protein) contain two PDZ (PSD-95/DlgA/ZO-1-like) domains followed by a COOH-terminal sequence that binds to active ERM family members. Using affinity chromatography, we identified polypeptides from placental microvilli that bind the PDZ domains of EBP50. Among these are 64- and/or 65-kD differentially phosphorylated polypeptides that bind preferentially to the first PDZ domain of EBP50, as well as to E3KARP, and that we call EPI64 (EBP50-PDZ interactor of 64 kD). The gene for human EPI64 lies on chromosome 22 where nine exons specify a protein of 508 residues that contains a Tre/Bub2/Cdc16 (TBC)/rab GTPase-activating protein (GAP) domain. EPI64 terminates in DTYL, which is necessary for binding to the PDZ domains of EBP50, as a mutant ending in DTYLA no longer interacts. EPI64 colocalizes with EBP50 and ezrin in syncytiotrophoblast and cultured cell microvilli, and this localization in cultured cells is abolished by introduction of the DTYLA mutation. In addition to EPI64, immobilized EBP50 PDZ domains retain several polypeptides from placental microvilli, including an isoform of nadrin, a rhoGAP domain-containing protein implicated in regulating vesicular transport. Nadrin binds EBP50 directly, probably through its COOH-terminal STAL sequence. Thus, EBP50 appears to bind membrane proteins as well as factors potentially involved in regulating membrane traffic.

    Funded by: NIGMS NIH HHS: GM36652

    The Journal of cell biology 2001;153;1;191-206

  • CD95 (APO-1/Fas) linkage to the actin cytoskeleton through ezrin in human T lymphocytes: a novel regulatory mechanism of the CD95 apoptotic pathway.

    Parlato S, Giammarioli AM, Logozzi M, Lozupone F, Matarrese P, Luciani F, Falchi M, Malorni W and Fais S

    Laboratories of Virology, Istituto Superiore di Sanità Viale Regina Elena 299, 00161 Rome, Italy.

    CD95 (APO-1/Fas) is a member of the tumor necrosis factor receptor family, which can trigger apoptosis in a variety of cell types. However, little is known of the mechanisms underlying cell susceptibility to CD95-mediated apoptosis. Here we show that human T cells that are susceptible to CD95-mediated apoptosis, exhibit a constitutive polarized morphology, and that CD95 colocalizes with ezrin at the site of cellular polarization. In fact, CD95 co-immunoprecipitates with ezrin exclusively in lymphoblastoid CD4(+) T cells and primary long-term activated T lymphocytes, which are prone to CD95-mediated apoptosis, but not in short-term activated T lymphocytes, which are refractory to the same stimuli, even expressing equal levels of CD95 on the cell membrane. Pre-treatment with ezrin antisense oligonucleotides specifically protected from the CD95-mediated apoptosis. Moreover, we show that the actin cytoskeleton integrity is essential for this function. These findings strongly suggest that the CD95 cell membrane polarization, through an ezrin-mediated association with the actin cytoskeleton, is a key intracellular mechanism in rendering human T lymphocytes susceptible to the CD95-mediated apoptosis.

    The EMBO journal 2000;19;19;5123-34

  • E3KARP mediates the association of ezrin and protein kinase A with the cystic fibrosis transmembrane conductance regulator in airway cells.

    Sun F, Hug MJ, Lewarchik CM, Yun CH, Bradbury NA and Frizzell RA

    Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.

    Although it is generally recognized that cystic fibrosis transmembrane conductance regulator (CFTR) contains a PSD-95/Disc-large/ZO-1 (PDZ)-binding motif at its COOH terminus, the identity of the PDZ domain protein(s) that interact with CFTR is uncertain, and the functional impact of this interaction is not fully understood. By using human airway epithelial cells, we show that CFTR associates with Na(+)/H(+) exchanger (NHE) type 3 kinase A regulatory protein (E3KARP), an EBP50/NHE regulatory factor (NHERF)-related PDZ domain protein. The PDZ binding motif located at the COOH terminus of CFTR interacts preferentially with the second PDZ domain of E3KARP, with nanomolar affinity. In contrast to EBP50/NHERF, E3KARP is predominantly localized (>95%) in the membrane fractions of Calu-3 and T84 cells, where CFTR is located. Moreover, confocal immunofluorescence microscopy of polarized Calu-3 monolayers shows that E3KARP and CFTR are co-localized at the apical membrane domain. We also found that ezrin associates with E3KARP in vivo. Co-expression of CFTR with E3KARP and ezrin in Xenopus oocytes potentiated cAMP-stimulated CFTR Cl(-) currents. These results support the concept that E3KARP functions as a scaffold protein that links CFTR to ezrin. Since ezrin has been shown previously to function as a protein kinase A anchoring protein, we suggest that one function served by the interaction of E3KARP with both ezrin and CFTR is to localize protein kinase A in the vicinity of the R-domain of CFTR. Since ezrin is also an actin-binding protein, the formation of a CFTR.E3KARP.ezrin complex may be important also in stabilizing CFTR at the apical membrane domain of airway cells.

    Funded by: NIDDK NIH HHS: DK44484, DK56490

    The Journal of biological chemistry 2000;275;38;29539-46

  • Ezrin function is required for ROCK-mediated fibroblast transformation by the Net and Dbl oncogenes.

    Tran Quang C, Gautreau A, Arpin M and Treisman R

    Transcription Laboratory, Room 528, Imperial Cancer Research Fund Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.

    The small G protein RhoA and its GDP/GTP exchange factors (GEFs) Net and Dbl can transform NIH 3T3 fibroblasts, dependent on the activity of the RhoA effector kinase ROCK. We investigated the role of the cytoskeletal linker protein ezrin in this process. RhoA effector loop mutants which can bind ROCK induce relocalization of ezrin to dorsal actin-containing cell surface protrusions, as do Net and Dbl. Both processes are inhibited by the ROCK inhibitor Y27632, which also inhibits association of ezrin with the cytoskeleton, and phosphorylation of T567, conserved between ezrin and its relatives radixin and moesin. ROCK can phosphorylate the ezrin C-terminus in vitro. The ezrin mutant T567A cannot be relocalized by activated RhoA, Net or Dbl or by ROCK itself, and also inhibits RhoA-mediated contractility and focal adhesion formation. Moreover, ezrin T567A, but not wild-type ezrin, restores contact inhibition to Net- and Dbl-transformed cells, and inhibits the activity of Net and Ras in focus formation assays. These results implicate ROCK-mediated ezrin C-terminal phosphorylation in transformation by RhoGEFs.

    The EMBO journal 2000;19;17;4565-76

  • Ezrin, a membrane-organizing protein, as a polarization marker of the retinal pigment epithelium in vertebrates.

    Kivelä T, Jääskeläinen J, Vaheri A and Carpén O

    Department of Ophthalmology, Helsinki University Central Hospital, Finland. tero.kivela@helsinki.fi

    Immunoreactivity for ezrin, a membrane-organizing phosphoprotein that tethers actin microfilaments to cell membrane proteins, was evaluated as a polarization marker in the intraocular neuroepithelial cells of vertebrates, especially in the retinal pigment epithelium (RPE). Six fetal human eyes representing the 14th-28th gestational weeks, 9 normal adult eyes, 12 eyes with intraocular tumors, and 26 eyes from 15 other vertebrate species were analyzed by immunohistochemistry using the avidin-biotinylated peroxidase complex (ABC) method and monoclonal antibody (mAb) 3C12 to ezrin. The apical cytoplasm and microvilli of the human RPE always reacted with mAb 3C12, but the basal cytoplasm was labeled in reactive RPE only. In autopsy eyes and if fixation was delayed, ezrin immunoreactivity in RPE was more diffuse. Developing RPE became gradually immunoreactive from the 14th week of gestation onward. The microvilli of the baboon, pig, raccoon dog, cow, and rat RPE cells were likewise labeled, and their basal cytoplasm was variably immunoreactive as well, but the microvilli of the avian RPE did not react with the antibody used. In all six mammals mentioned, both layers of the ciliary epithelium and the anterior iris epithelium reacted for ezrin, and the posterior epithelium was weakly labeled in pig, cow, and rat eyes. Normal peripheral and reactive human retina, and normal baboon, pig, raccoon dog, cow, rat, black grouse, and jay eyes, showed immunoreaction for ezrin in Muller cells, usually in their microvilli. Ezrin is widely found in RPE and anterior segment neuroepithelia of the mammalian eye, in which it may segregate membrane proteins to specific membrane surfaces, especially to the apical microvilli of the RPE, which intimately interact with outer segments of photoreceptor cells. The ezrin gene on human chromosome 6q25-26 is consequently a candidate gene for causing retinal degenerations.

    Cell and tissue research 2000;301;2;217-23

  • Protein kinase A associates with cystic fibrosis transmembrane conductance regulator via an interaction with ezrin.

    Sun F, Hug MJ, Bradbury NA and Frizzell RA

    Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.

    The cystic fibrosis transmembrane conductance regulator (CFTR) is an epithelial Cl(-) channel whose activity is controlled by cAMP-dependent protein kinase (PKA)-mediated phosphorylation. We found that CFTR immunoprecipitates from Calu-3 airway cells contain endogenous PKA, which is capable of phosphorylating CFTR. This phosphorylation is stimulated by cAMP and inhibited by the PKA inhibitory peptide. The endogenous PKA that co-precipitates with CFTR could also phosphorylate the PKA substrate peptide, Leu-Arg-Arg-Ala-Ser-Leu-Gly (kemptide). Both the catalytic and type II regulatory subunits of PKA are identified by immunoblotting CFTR immunoprecipitates, demonstrating that the endogenous kinase associated with CFTR is PKA, type II (PKA II). Phosphorylation reactions mediated by CFTR-associated PKA II are inhibited by Ht31 peptide but not by the control peptide Ht31P, indicating that a protein kinase A anchoring protein (AKAP) is responsible for the association between PKA and CFTR. Ezrin may function as this AKAP, since it is expressed in Calu-3 and T84 epithelia, ezrin binds RII in overlay assays, and RII is immunoprecipitated with ezrin from Calu-3 cells. Whole-cell patch clamp of Calu-3 cells shows that Ht31 peptide reduces cAMP-stimulated CFTR Cl(-) current, but Ht31P does not. Taken together, these data demonstrate that PKA II is linked physically and functionally to CFTR by an AKAP interaction, and they suggest that ezrin serves as an AKAP for PKA-mediated phosphorylation of CFTR.

    Funded by: NIDDK NIH HHS: DK56490

    The Journal of biological chemistry 2000;275;19;14360-6

  • The TSC1 tumour suppressor hamartin regulates cell adhesion through ERM proteins and the GTPase Rho.

    Lamb RF, Roy C, Diefenbach TJ, Vinters HV, Johnson MW, Jay DG and Hall A

    MRC Laboratory for Molecular Cell Biology and Department of Biochemistry, University College London, UK. r.lamb@ucl.ac.uk

    Loss of the tumour-suppressor gene TSC1 is responsible for hamartoma development in tuberous sclerosis complex (TSC), which renders several organs susceptible to benign tumours. Hamartin, the protein encoded by TSC1, contains a coiled-coil domain and is expressed in most adult tissues, although its function is unknown. Here we show that hamartin interacts with the ezrin-radixin-moesin (ERM) family of actin-binding proteins. Inhibition of hamartin function in cells containing focal adhesions results in loss of adhesion to the cell substrate, whereas overexpression of hamartin in cells lacking focal adhesions results in activation of the small GTP-binding protein Rho, assembly of actin stress fibres and formation of focal adhesions. Interaction of endogenous hamartin with ERM-family proteins is required for activation of Rho by serum or by lysophosphatidic acid (LPA). Our data indicate that disruption of adhesion to the cell matrix through loss of hamartin may initiate the development of TSC hamartomas and that a Rho-mediated signalling pathway regulating cell adhesion may constitute a rate-limiting step in tumour formation.

    Nature cell biology 2000;2;5;281-7

  • Identification of a novel member of the chloride intracellular channel gene family (CLIC5) that associates with the actin cytoskeleton of placental microvilli.

    Berryman M and Bretscher A

    Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens, Ohio 45701, USA. berryman@ohiou.edu

    The chloride intracellular channel (CLIC) gene family has been implicated in chloride ion transport within various subcellular compartments. We report here the molecular, biochemical, and cellular characterization of a new member of this gene family termed CLIC5. CLIC5 was isolated from extracts of placental microvilli as a component of a multimeric complex consisting of several known cytoskeletal proteins, including actin, ezrin, alpha-actinin, gelsolin, and IQGAP1. We cloned human cDNAs and generated antibodies specific for CLIC5, CLIC1/NCC27, and CLIC4/huH1/p64H1. CLIC5 shares 52-76% overall identity with human CLIC1, CLIC2, CLIC3, and CLIC4. Northern blot analysis showed that CLIC5 has a distinct pattern of expression compared with CLIC1 and CLIC4. Immunoblot analysis of extracts from placental tissues demonstrated that CLIC4 and CLIC5 are enriched in isolated placental microvilli, whereas CLIC1 is not. Moreover, in contrast to CLIC1 and CLIC4, CLIC5 is associated with the detergent-insoluble cytoskeletal fraction of microvilli. Indirect immunofluorescence microscopy revealed that CLIC4 and CLIC5 are concentrated within the apical region of the trophoblast, whereas CLIC1 is distributed throughout the cytoplasm. These studies suggest that CLIC1, CLIC4, and CLIC5 play distinct roles in chloride transport and that CLIC5 interacts with the cortical actin cytoskeleton in polarized epithelial cells.

    Funded by: NIGMS NIH HHS: GM14352, GM36652, R01 GM036652

    Molecular biology of the cell 2000;11;5;1509-21

  • Polarization and interaction of adhesion molecules P-selectin glycoprotein ligand 1 and intercellular adhesion molecule 3 with moesin and ezrin in myeloid cells.

    Alonso-Lebrero JL, Serrador JM, Domínguez-Jiménez C, Barreiro O, Luque A, del Pozo MA, Snapp K, Kansas G, Schwartz-Albiez R, Furthmayr H, Lozano F and Sánchez-Madrid F

    Servicio de Inmunología, Hospital de la Princesa, Madrid, Spain; Northwestern University Medical School, Chicago, IL, USA.

    In response to the chemoattractants interleukin 8, C5a, N-formyl-methionyl-leucyl-phenylalanine, and interleukin 15, adhesion molecules P-selectin glycoprotein ligand 1 (PSGL-1), intercellular adhesion molecule 3 (ICAM-3), CD43, and CD44 are redistributed to a newly formed uropod in human neutrophils. The adhesion molecules PSGL-1 and ICAM-3 were found to colocalize with the cytoskeletal protein moesin in the uropod of stimulated neutrophils. Interaction of PSGL-1 with moesin was shown in HL-60 cell lysates by isolating a complex with glutathione S-transferase fusions of the cytoplasmic domain of PSGL-1. Bands of 78- and 81-kd were identified as moesin and ezrin by Western blot analysis. ICAM-3 and moesin also coeluted from neutrophil lysates with an anti-ICAM-3 immunoaffinity assay. Direct interaction of the cytoplasmic domains of ICAM-3 and PSGL-1 with the amino-terminal domain of recombinant moesin was demonstrated by protein-protein binding assays. These results suggest that the redistribution of PSGL-1 and its association with intracellular molecules, including the ezrin-radixin-moesin actin-binding proteins, regulate functions mediated by PSGL-1 in leukocytes stimulated by chemoattractants.

    Blood 2000;95;7;2413-9

  • Ezrin links syndecan-2 to the cytoskeleton.

    Granés F, Urena JM, Rocamora N and Vilaró S

    Department of Cellular Biology, Faculty of Biology, University of Barcelona, Avenue Diagonal 645, Spain.

    The syndecan family of heparan sulfate proteoglycans is known to associate with the actin cytoskeleton, possibly transducing signals from the extracellular matrix. In the search for proteins that could mediate the association of syndecan-2 with the actin cytoskeleton we found that ezrin, a protein which links membrane receptors to the cytoskeleton, coimmunoprecipitated with syndecan-2 in COS-1 cells. In vitro assays indicated a direct association between the amino-terminal domain of ezrin and the cytoplasmic domain of syndecan-2. Confocal microscopy showed colocalization of ezrin and syndecan-2 in actin-rich microspikes in COS-1 cells. The syndecan-2/ezrin protein complex was resistant to 0.2% Triton X-100 extraction but the syndecan-2/amino-terminal domain of ezrin complex was not, which indicated that carboxi-terminal domain of ezrin is involved in the cytoskeleton anchorage of this protein complex. Additionally we observed that the activation of rhoA GTPase increased syndecan-2 insolubility in 0.2% Triton X-100 and syndecan-2/ezrin association. Taken together, these results indicate that ezrin connects syndecan-2 to the actin cytoskeleton.

    Journal of cell science 2000;113 ( Pt 7);1267-76

  • The HIV-1 vpr protein induces anoikis-resistance by modulating cell adhesion process and microfilament system assembly.

    Matarrese P, Conti L, Varano B, Gauzzi MC, Belardelli F, Gessani S and Malorni W

    Department of Ultrastructures, Instituto Superiore di Sanità, Viale Regina Elena, 299-00161 Rome, Italy.

    We have previously shown that CD4+ T Jurkat cells constitutively expressing low levels of the human immunodeficiency virus 1 (HIV-1) vpr protein were less susceptible to undergo apoptosis than control cells.1 In this study we have investigated the role of vpr in affecting mechanisms of importance in the control of apoptosis. Vpr-expressing clones consistently aggregated in clusters with time in culture, whereas mock-transfected cells grew as dispersed cultures. The analysis of adhesion molecules involved in cell-to-cell as well as in cell-substrate interactions showed a higher expression of cadherin and integrins alpha5 and alpha6 in vpr-transfected clones with respect to mock-transfected cells. This up-modulation was specifically blocked by cell exposure to antisense oligonucleotides targeted at the vpr. In addition, F-actin microfilament cytoskeletal organization, known to be involved in cell-cell interaction pathways and in the modulation of cell surface molecule expression, was significantly improved in vpr-expressing clones, in which filament polymerization was increased. We thus envisage that vpr viral protein can maintain cell survival via a specific activity on cytoskeleton-dependent cell adhesion pathways, i.e. by inducing anoikis-resistance. These particular effects of vpr might enhance the homing, spreading and survival of the infected lymphocytes, thus contributing to virus persistence in the course of acute HIV-1 infection.

    Cell death and differentiation 2000;7;1;25-36

  • Ezrin regulates cell-cell and cell-matrix adhesion, a possible role with E-cadherin/beta-catenin.

    Hiscox S and Jiang WG

    Metastasis Research Group, University Department of Surgery, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. jiangw@cf.ac.uk

    Ezrin, radixin, moesin and merlin form a subfamily of conserved proteins in the band 4.1 superfamily. The function of these proteins is to link the plasma membrane to the actin cytoskeleton. Merlin is defective or absent in schwannomas and meningiomas and has been suggested to function as a tumour suppressor. In this study, we have examined the role of ezrin as a potential regulator of the adhesive and invasive behaviour of tumour cells. We have shown that following inhibition of ezrin expression in colo-rectal cancer cells using antisense oligonucleotides, these cells displayed a reduced cell-cell adhesiveness together with a gain in their motile and invasive behaviour. These cells also displayed increased spreading over matrix-coated surfaces. Immunofluorescence studies revealed that antisense-treated cells also displayed an increased staining of paxillin in areas representing focal adhesions. Furthermore, coprecipitation studies revealed an association of ezrin with E-cadherin and beta-catenin. Induction of the phosphorylation of ezrin by orthovanadate and hepatocyte growth factor/scatter factor resulted in changes similar to those seen with antisense treatment, together with a marked decrease in the association of ezrin with both beta-catenin and E-cadherin. It is concluded that ezrin regulates cell-cell and cell-matrix adhesion, by interacting with cell adhesion molecules E-cadherin and beta-catenin, and may thus play an important role in the control of adhesion and invasiveness of cancer cells.

    Journal of cell science 1999;112 Pt 18;3081-90

  • Ezrin, a plasma membrane-microfilament linker, signals cell survival through the phosphatidylinositol 3-kinase/Akt pathway.

    Gautreau A, Poullet P, Louvard D and Arpin M

    Laboratoire de Morphogenèse et Signalisation Cellulaires, Unité Mixte de Recherche, 144 Centre National de la Recherche Scientifique/Institut Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France.

    ERM (Ezrin-Radixin-Moesin) proteins function as plasma membrane-actin cytoskeleton linkers and participate in the formation of specialized domains of the plasma membrane. We have investigated ezrin function in tubulogenesis of a kidney-derived epithelial cell line, LLC-PK1. Here we show that cells overproducing a mutant form of ezrin in which Tyr-353 was changed to a phenylalanine (Y353F) undergo apoptosis when assayed for tubulogenesis. While investigating the mechanism responsible for this apoptosis, we found that ezrin interacts with p85, the regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase). Two distinct sites of ezrin are involved in this interaction, the amino-terminal domain containing the first 309 aa and the phosphorylated Tyr-353 residue, which binds to the carboxyl-terminal SH2 domain of p85. Cells producing Y353F ezrin are defective in activation of the protein kinase Akt, a downstream target of PI 3-kinase that protects cells against apoptosis. Furthermore, the apoptotic phenotype of these cells is rescued by production of a constitutively activated form of PI 3-kinase. Taken together, these results establish a novel function for ezrin in determining survival of epithelial cells by activating the PI 3-kinase/Akt pathway.

    Proceedings of the National Academy of Sciences of the United States of America 1999;96;13;7300-5

  • Homotypic and heterotypic interaction of the neurofibromatosis 2 tumor suppressor protein merlin and the ERM protein ezrin.

    Grönholm M, Sainio M, Zhao F, Heiska L, Vaheri A and Carpén O

    Departments of Pathology and Virology, University of Helsinki, Haartman Institute, PO Box 21 (Haartmaninkatu 3), FIN-00014 Helsinki. mikaela.gronholm@helsinki.fi

    Ezrin, radixin and moesin (ERM) are homologous proteins, which are linkers between plasma membrane components and the actin-containing cytoskeleton. The ERM protein family members associate with each other in a homotypic and heterotypic manner. The neurofibromatosis 2 (NF2) tumor suppressor protein merlin (schwannomin) is structurally related to ERM members. Merlin is involved in tumorigenesis of NF2-associated and sporadic schwannomas and meningiomas, but the tumor suppressor mechanism is poorly understood. We have studied the ability of merlin to self-associate and bind ezrin. Ezrin was coimmunoprecipitated with merlin from lysates of human U251 glioma cells and from COS-1 cells transfected with cDNA encoding for merlin isoform I. The interaction was further studied and the association domains were mapped with the yeast two-hybrid system and with blot overlay and affinity precipitation experiments. The heterotypic binding of merlin and ezrin and the homotypic association of merlin involves interaction between the amino- and carboxy-termini. The amino-terminal association domain of merlin involves residues 1-339 and has similar features with the amino-terminal association domain of ezrin. The carboxy-terminal association domain cannot be mapped as precisely as in ezrin, but it requires residues 585-595 and a more amino-terminal segment. Unlike ezrin, merlin does not require activation for self-association but native merlin molecules can interact with each other. Heterodimerization between merlin and ezrin, however, occurs only following conformational alterations in both proteins. These results biochemically connect merlin to the cortical cytoskeleton and indicate differential regulation of merlin from ERM proteins.

    Journal of cell science 1999;112 ( Pt 6);895-904

  • Moesin, the major ERM protein of lymphocytes and platelets, differs from ezrin in its insensitivity to calpain.

    Shcherbina A, Bretscher A, Kenney DM and Remold-O'Donnell E

    The Center for Blood Research, Harvard Medical School, Boston, MA 02115, USA.

    The ERM proteins, ezrin, radixin and moesin, provide regulated linkage of the cytoskeleton with the plasma membrane, particularly in cell surface projections. Ezrin and moesin were found co-expressed, and radixin was not detected, in human blood lymphocytes, monocytes and neutrophils. Moesin is the quantitatively dominant ERM protein in these cells and the only one in platelets. Because Ca signaling pathways involving calpain cleavages are important in blood cells, we examined ERM protein sensitivity to this protease. A striking difference was discovered: sensitivity of ezrin and resistance of moesin (and radixin) to calpain. In intact stimulated lymphocytes, ezrin was cleaved, while moesin was not, strongly suggesting that differential sensitivity to calpain contributes to specialized functions of these proteins.

    Funded by: NIAID NIH HHS: AI39574; NIGMS NIH HHS: GM36652

    FEBS letters 1999;443;1;31-6

  • The localization of myosin VI at the golgi complex and leading edge of fibroblasts and its phosphorylation and recruitment into membrane ruffles of A431 cells after growth factor stimulation.

    Buss F, Kendrick-Jones J, Lionne C, Knight AE, Côté GP and Paul Luzio J

    Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 2QR, United Kingdom. fb1@mole.bio.cam.ac.uk

    Myosin VI is an unconventional myosin that may play a role in vesicular membrane traffic through actin rich regions of the cytoplasm in eukaryotic cells. In this study we have cloned and sequenced a cDNA encoding a chicken intestinal brush border myosin VI. Polyclonal antisera were raised to bacterially expressed fragments of this myosin VI. The affinity purified antibodies were highly specific for myosin VI by immunoblotting and immunoprecipitation and were used to study the localization of the protein by immunofluorescence and immunoelectron microscopy. It was found that in NRK and A431 cells, myosin VI was associated with both the Golgi complex and the leading, ruffling edge of the cell as well as being present in a cytosolic pool. In A431 cells in which cell surface ruffling was stimulated by EGF, myosin VI was phosphorylated and recruited into the newly formed ruffles along with ezrin and myosin V. In vitro experiments suggested that a p21-activated kinase (PAK) might be the kinase responsible for phosphorylation in the motor domain. These results strongly support a role for myosin VI in membrane traffic on secretory and endocytic pathways.

    The Journal of cell biology 1998;143;6;1535-45

  • Genomic structure of the human ezrin gene.

    Majander-Nordenswan P, Sainio M, Turunen O, Jääskeläinen J, Carpén O, Kere J and Vaheri A

    Department of Virology, Haartman Institute, University of Helsinki, Finland. paivi.majander-nordenswan@helsinki.fi

    The ERM proteins, ezrin, radixin, and moesin, act as linkers between the plasma membrane and actin cytoskeleton. They are involved in a variety of cellular functions, such as cell adhesion, migration, and the organization of cell surface structures, and are highly homologous, both in protein sequence and in functional activity, with merlin/schwannomin, a neurofibromatosis-2-associated tumor-suppressor protein. We report here the genomic structure and intron junction sequences of the human ezrin gene. Ezrin consists of 13 exons and spans approximately 24 kb genomic DNA. The coding parts of the exons range in size from 12 bp to 275 bp and the introns from 182 bp to 7 kb. The genomic structures of ezrin and moesin are highly conserved, suggesting their recent divergence. Radiation hybrid mapping has refined the location of ezrin to the interval between D6S442 and D6S281.

    Human genetics 1998;103;6;662-5

  • NHE3 kinase A regulatory protein E3KARP binds the epithelial brush border Na+/H+ exchanger NHE3 and the cytoskeletal protein ezrin.

    Yun CH, Lamprecht G, Forster DV and Sidor A

    Department of Medicine, Gastroenterology Division, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. cyun@welchlink.welch.jhu.edu

    Cyclic AMP is a major second messenger that inhibits the brush border Na+/H+ exchanger NHE3. We have previously shown that either of two related regulatory proteins, E3KARP or NHERF, is necessary for the cAMP-dependent inhibition of NHE3. In the present study, we characterized the interaction between NHE3 and E3KARP using in vitro binding assays. We found that NHE3 directly binds to E3KARP and that the entirety of the second PSD-95/Dlg/ZO-1 (PDZ) domain plus the carboxyl-terminal domain of E3KARP are required to bind NHE3. E3KARP binds an internal region within the NHE3 C-terminal cytoplasmic tail, defining a new mode of PDZ domain interaction. Analyses of cellular distribution of NHE3 and E3KARP expressed in PS120 fibroblasts show that NHE3 and E3KARP are co-localized on the plasma membrane, but not in a distinct juxtanuclear compartment in which NHE3 is predominantly expressed. The distributions of NHE3 and E3KARP were not affected by treatment with 8-bromo-cAMP. As shown earlier for the human homolog of NHERF, we also found that the cytoskeletal protein ezrin binds to the carboxyl-terminal domain of E3KARP. These results are consistent with the possibility that E3KARP and NHERF may function as scaffold proteins that bind to both NHE3 and ezrin. Since ezrin is a protein kinase A anchoring protein, we suggest that the scaffolding function of E3KARP binding to both ezrin and NHE3 localizes cAMP-dependent protein kinase in the vicinity of the cytoplasmic domain of NHE3, which is phosphorylated by elevated cAMP.

    Funded by: NIDDK NIH HHS: DK-44484

    The Journal of biological chemistry 1998;273;40;25856-63

  • Association of ezrin with intercellular adhesion molecule-1 and -2 (ICAM-1 and ICAM-2). Regulation by phosphatidylinositol 4, 5-bisphosphate.

    Heiska L, Alfthan K, Grönholm M, Vilja P, Vaheri A and Carpén O

    Department of Pathology, University of Helsinki, Haartman Institute, 00014 Helsinki, Finland.

    Ezrin is a cytoplasmic linker molecule between plasma membrane components and the actin-containing cytoskeleton. We studied whether ezrin is associated with intercellular adhesion molecule (ICAM)-1, -2, and -3. In transfected cells, ICAM-1 and ICAM-2 colocalized with ezrin in microvillar projections, whereas an ICAM-1 construct attached to cell membrane via a glycophosphatidylinositol anchor was uniformly distributed on the cell surface. An interaction of ICAM-2 and ezrin was seen by affinity precipitation, microtiter binding assay, coimmunoprecipitation, and surface plasmon resonance methods. The calculated KD value was 3.3 x 10(-7) M. Phosphatidylinositol 4, 5-bisphosphate (PtdIns(4,5)P2) induced an interaction of ezrin and ICAM-1 and enhanced the interaction of ezrin and ICAM-2, but ICAM-3 did not bind ezrin even in the presence of PtdIns(4,5)P2. PtdIns(4, 5)P2 was shown to bind to cytoplasmic tails of ICAM-1 and ICAM-2, which are the first adhesion proteins demonstrated to interact with PtdIns(4,5)P2. The results indicate an interaction of ezrin with ICAM-1 and ICAM-2 and suggest a regulatory role of phosphoinositide signaling pathways in regulation of ICAM-ezrin interaction.

    The Journal of biological chemistry 1998;273;34;21893-900

  • CD43 interacts with moesin and ezrin and regulates its redistribution to the uropods of T lymphocytes at the cell-cell contacts.

    Serrador JM, Nieto M, Alonso-Lebrero JL, del Pozo MA, Calvo J, Furthmayr H, Schwartz-Albiez R, Lozano F, González-Amaro R, Sánchez-Mateos P and Sánchez-Madrid F

    Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain.

    Chemokines as well as the signaling through the adhesion molecules intercellular adhesion molecule (ICAM)-3 and CD43 are able to induce in T lymphocytes their switching from a spherical to a polarized motile morphology, with the formation of a uropod at the rear of the cell. We investigated here the role of CD43 in the regulation of T-cell polarity, CD43-cytoskeletal interactions, and lymphocyte aggregation. Pro-activatory anti-CD43 monoclonal antibody (MoAb) induced polarization of T lymphocytes with redistribution of CD43 to the uropod and the CCR2 chemokine receptor to the leading edge of the cell. Immunofluorescence analysis showed that all three ezrin-radixin-moesin (ERM) actin-binding proteins localized in the uropod of both human T lymphoblasts stimulated with anti-CD43 MoAb and tumor-infiltrating T lymphocytes. Radixin localized at the uropod neck, whereas ezrin and moesin colocalized with CD43 in the uropod. Biochemical analyses showed that ezrin and moesin coimmunoprecipitated with CD43 in T lymphoblasts. Furthermore, in these cells, the CD43-associated moesin increased after stimulation through CD43. The interaction of moesin and ezrin with CD43 was specifically mediated by the cytoplasmic domain of CD43, as shown by precipitation of both ERM proteins with a GST-fusion protein containing the CD43 cytoplasmic tail. Videomicroscopy analysis of homotypic cell aggregation induced through CD43 showed that cellular uropods mediate cell-cell contacts and lymphocyte recruitment. Immunofluorescence microscopy performed in parallel showed that uropods enriched in CD43 and moesin localized at the cell-cell contact areas of cell aggregates. The polarization and homotypic cell aggregation induced through CD43 was prevented by butanedione monoxime, indicating the involvement of myosin cytoskeleton in these phenomena. Altogether, these data indicate that CD43 plays an important regulatory role in remodeling T-cell morphology, likely through its interaction with actin-binding proteins ezrin and moesin. In addition, the redistribution of CD43 to the uropod region of migrating lymphocytes and during the formation of cell aggregates together with the enhancing effect of anti-CD43 antibodies on lymphocyte cell recruitment suggest that CD43 plays a key role in the regulation of cell-cell interactions during lymphocyte traffic.

    Funded by: NIAMS NIH HHS: AR41045

    Blood 1998;91;12;4632-44

  • Mapping of ezrin dimerization using yeast two-hybrid screening.

    Bhartur SG and Goldenring JR

    Department of Medicine, Medical College of Georgia, Augusta, USA.

    Ezrin, a membrane-cytoskeleton linker protein, is involved in the recruitment of H+/K(+)-ATPase-containing tubulovesicles to the canalicular membrane during acid secretion in the parietal cell. Ezrin exists as monomers and head-to-tail dimers in vivo, and oligomerization is presumably important for activation. In this study, we mapped regions of ezrin-ezrin interaction using the yeast two-hybrid assay. We observed that the N-terminal 283 amino acids are sufficient for interaction with the carboxyl terminal 140 amino acids. The region 333.446 inhibits this association. However, the inclusion of amino acids 283-310 appears to release the inhibition. These specific interactions may play a critical role in the formation of dimerization-competent ezrin molecules.

    Funded by: NIDDK NIH HHS: DK43405, DK48370

    Biochemical and biophysical research communications 1998;243;3;874-7

  • Identification of EBP50: A PDZ-containing phosphoprotein that associates with members of the ezrin-radixin-moesin family.

    Reczek D, Berryman M and Bretscher A

    Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.

    Members of the ezrin-radixin-moesin (ERM) family of membrane-cytoskeletal linking proteins have NH2- and COOH-terminal domains that associate with the plasma membrane and the actin cytoskeleton, respectively. To search for ERM binding partners potentially involved in membrane association, tissue lysates were subjected to affinity chromatography on the immobilized NH2-terminal domains of ezrin and moesin, which comprise the ezrin-radixin-moesin-association domain (N-ERMAD). A collection of polypeptides at 50-53 kD from human placenta and at 58-59 kD from bovine brain bound directly to both N-ERMADs. The 50-53-kD placental proteins migrated as a major 50-kD species after phosphatase treatment, indicating that the heterogeneity is due to different phosphorylation states. We refer to these polypeptides as ERM-binding phosphoprotein 50 (EBP50). Sequence analysis of human EBP50 was used to identify an approximately 2-kb human cDNA that encodes a 357-residue polypeptide. Recombinant EBP50 binds tightly to the N-ERMADs of ezrin and moesin. Peptide sequences from the brain candidate indicated that it is closely related to EBP50. EBP50 has two PSD-95/DlgA/ZO-1-like (PDZ) domains and is most likely a homologue of rabbit protein cofactor, which is involved in the protein kinase A regulation of the renal brush border Na+/H+ exchanger. EBP50 is widely distributed in tissues, and is particularly enriched in those containing polarized epithelia. Immunofluorescence microscopy of cultured cells and tissues revealed that EBP50 colocalizes with actin and ezrin in the apical microvilli of epithelial cells, and immunoelectron microscopy demonstrated that it is specifically associated with the microvilli of the placental syncytiotrophoblast. Moreover, EBP50 and ezrin can be coimmunoprecipitated as a complex from isolated human placental microvilli. These findings show that EBP50 is a physiologically relevant ezrin binding protein. Since PDZ domains are known to mediate associations with integral membrane proteins, one mode of membrane attachment of ezrin is likely to be mediated through EBP50.

    Funded by: NIGMS NIH HHS: GM36652, R01 GM036652

    The Journal of cell biology 1997;139;1;169-79

  • Direct interaction of the Rho GDP dissociation inhibitor with ezrin/radixin/moesin initiates the activation of the Rho small G protein.

    Takahashi K, Sasaki T, Mammoto A, Takaishi K, Kameyama T, Tsukita S and Takai Y

    Department of Molecular Biology and Biochemistry, Osaka University Medical School, Suita 565, Japan.

    The Rho GDP dissociation inhibitor (GDI) forms a complex with the GDP-bound form of the Rho family small G proteins and inhibits their activation. The GDP-bound form complexed with Rho GDI is not activated by the GDP/GTP exchange factor for the Rho family members, suggesting the presence of another factor necessary for this activation. We have reported that the Rho subfamily members regulate the ezrin/radixin/moesin (ERM)-CD44 system, implicated in reorganization of actin filaments. Here we report that Rho GDI directly interacts with ERM, initiating the activation of the Rho subfamily members by reducing the Rho GDI activity. These results suggest that ERM as well as Rho GDI and the Rho GDP/GTP exchange factor are involved in the activation of the Rho subfamily members, which then regulate reorganization of actin filaments through the ERM system.

    The Journal of biological chemistry 1997;272;37;23371-5

  • Specific binding of HIV-1 envelope protein gp120 to the structural membrane proteins ezrin and moesin.

    Hecker C, Weise C, Schneider-Schaulies J, Holmes HC and ter Meulen V

    Institut für Virologie und Immunbiologie, Würzburg, Germany.

    The observation that HIV in vitro can infect CD4- and Gal-C-negative brain cell lines has stimulated this study to identify alternative gp120-binding proteins on brain cells. HIV-1 gp120 binding proteins of the CD4-negative and Gal-C-negative, non-productively infectable human glioblastoma cell line D54 were purified by affinity chromatography over a gp120-conjugated sepharose column and identified by peptide microsequencing. The binding capacity and specificity of this column was controlled using extracts of CD4-positive cells. Two of seven prominent proteins eluted from the gp120 affinity column specifically bound gp120 in Western blot overlay experiments and were identified by subsequent immunoblotting and microsequencing as ezrin and moesin, members of the ERM (ezrin, radixin, moesin) family of cellular structural membrane proteins. Antibodies to ezrin and moesin specifically recognized the eluted gp120 binding proteins confirming their identification. Ezrin and moesin are structural proteins binding to the cellular membrane and to several cytoskeletal and transmembrane proteins. Our results suggest that ezrin and moesin might play a role as gp160/gp120 binding proteins during the uptake, the assembly or the budding of HIV.

    Virus research 1997;49;2;215-23

  • Ezrin is a cyclic AMP-dependent protein kinase anchoring protein.

    Dransfield DT, Bradford AJ, Smith J, Martin M, Roy C, Mangeat PH and Goldenring JR

    Institute of Molecular Medicine and Genetics, Medical College of Georgia and the Augusta Veterans Affairs Medical Center, 30912, USA.

    cAMP-dependent protein kinase (A-kinase) anchoring proteins (AKAPs) are responsible for the subcellular sequestration of the type II A-kinase. Previously, we identified a 78 kDa AKAP which was enriched in gastric parietal cells. We have now purified the 78 kDa AKAP to homogeneity from gastric fundic mucosal supernates using type II A-kinase regulatory subunit (RII) affinity chromatography. The purified 78 kDa AKAP was recognized by monoclonal antibodies against ezrin, the canalicular actin-associated protein. Recombinant ezrin produced in either Sf9 cells or bacteria also bound RII. Recombinant radixin and moesin, ezrin-related proteins, also bound RII in blot overlay. Analysis of recombinant truncations of ezrin mapped the RII binding site to a region between amino acids 373 and 439. This region contained a 14-amino-acid amphipathic alpha-helical putative RII binding region. A synthetic peptide containing the amphipathic helical region (ezrin409-438) blocked RII binding to ezrin, but a peptide with a leucine to proline substitution at amino acid 421 failed to inhibit RII binding. In mouse fundic mucosa, RII immunoreactivity redistributed from a predominantly cytosolic location in resting parietal cells, to a canalicular pattern in mucosa from animals stimulated with gastrin. These results demonstrate that ezrin is a major AKAP in gastric parietal cells and may function to tether type II A-kinase to a region near the secretory canaliculus.

    Funded by: NIDDK NIH HHS: DK-009026, DK43405

    The EMBO journal 1997;16;1;35-43

  • Cytoskeletal proteins inside human immunodeficiency virus type 1 virions.

    Ott DE, Coren LV, Kane BP, Busch LK, Johnson DG, Sowder RC, Chertova EN, Arthur LO and Henderson LE

    AIDS Vaccine Program, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702-1201, USA. ott@avpvx1.ncifcrf.gov.

    We have identified three types of cytoskeletal proteins inside human immunodeficiency virus type 1 (HIV-1) virions by analyzing subtilisin-digested particles. HIV-1 virions were digested with protease, and the treated particles were isolated by sucrose density centrifugation. This method removes both exterior viral proteins and proteins associated with microvesicles that contaminate virion preparations. Since the proteins inside the virion are protected from digestion by the viral lipid envelope, they can be isolated and analyzed after treatment. Experiments presented here demonstrated that this procedure removed more than 95% of the protein associated with microvesicles. Proteins in digested HIV-1(MN) particles from infected H9 and CEM(ss) cell lines were analyzed by high-pressure liquid chromatography, protein sequencing, and immunoblotting. The data revealed that three types of cytoskeletal proteins are present in virions at different concentrations relative to the molar level of Gag: actin (approximately 10 to 15%), ezrin and moesin (approximately 2%), and cofilin (approximately 2 to 10%). Our analysis of proteins within virus particles detected proteolytic fragments of alpha-smooth muscle actin and moesin that were cleaved at sites which might be recognized by HIV-1 protease. These cleavage products are not present in microvesicles from uninfected cells. Therefore, these processed proteins are most probably produced by HIV-1 protease digestion. The presence of these fragments, as well as the incorporation of a few specific cytoskeletal proteins into virions, suggests an active interaction between cytoskeletal and viral proteins.

    Journal of virology 1996;70;11;7734-43

  • Identification of the 70kD heat shock cognate protein (Hsc70) and alpha-actinin-1 as novel phosphotyrosine-containing proteins in T lymphocytes.

    Egerton M, Moritz RL, Druker B, Kelso A and Simpson RJ

    Transplantation Biology Unit, Queensland Institute for Medical Research, Brisbane, Australia. markE@qimr.edu.au

    T cell antigen receptor (TCR) ligation results in the tyrosine phosphorylation of numerous intracellular protein substrates, and the identification of these substrates has been a major undertaking by several groups. We have used pervanadate treatment to artificially increase cellular phosphotyrosine levels and immobilized anti-phosphotyrosine monoclonal antibodies to partially purify tyrosine phosphorylated proteins in quantities suitable for amino acid sequencing. This strategy was used to identify three phosphotyrosine containing proteins, with relative molecular masses of 105, 81, and 76 kD by amino acid sequencing. Here we report the identification of pp105 as alpha-actinin-1, pp81 as the murine equivalent of the HS1 gene product, and pp76 as Hsc70. This is the first report that alpha-actinin-1 and Hsc70 are targets of activated tyrosine kinases. Furthermore, we show that Hsc70 is tyrosine phosphorylated in response to TCR ligation, which constitutes the first evidence that Hsc70 might be subject to regulation by tyrosine kinase signaling pathways.

    Biochemical and biophysical research communications 1996;224;3;666-74

  • Ezrin self-association involves binding of an N-terminal domain to a normally masked C-terminal domain that includes the F-actin binding site.

    Gary R and Bretscher A

    Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.

    Ezrin is a membrane-cytoskeletal linking protein that is concentrated in actin-rich surface structures. It is closely related to the microvillar proteins radixin and moesin and to the tumor suppressor merlin/schwannomin. Cell extracts contain ezrin dimers and ezrin-moesin heterodimers in addition to monomers. Truncated ezrin fusion proteins were assayed by blot overlay to determine which regions mediate self-association. Here we report that ezrin self-association occurs by head-to-tail joining of distinct N-terminal and C-terminal domains. It is likely that these domains, termed N- and C-ERMADs (ezrin-radixin-moesin association domain), are responsible for homotypic and heterotypic associations among ERM family members. The N-ERMAD of ezrin resided within amino acids 1-296; deletion of 10 additional residues resulted in loss of activity. The C-ERMAD was mapped to the last 107 amino acids of ezrin, residues 479-585. The two residues at the C-terminus were required for activity, and the region from 530-585 was insufficient. The C-ERMAD was masked in the native monomer. Exposure of this domain required unfolding ezrin with sodium dodecyl sulfate or expressing the domain as part of a truncated protein. Intermolecular association could not occur unless the C-ERMAD had been made accessible to its N-terminal partner. It can be inferred that dimerization in vivo requires an activation step that exposes this masked domain. The conformationally inaccessible C-terminal region included the F-actin binding site, suggesting that this activity is likewise regulated by masking.

    Funded by: NIGMS NIH HHS: GM-36652

    Molecular biology of the cell 1995;6;8;1061-75

  • Indirect association of ezrin with F-actin: isoform specificity and calcium sensitivity.

    Shuster CB and Herman IM

    Program in Cell, Molecular, and Developmental Biology, Tufts University Health Science Schools, Boston, Massachusetts 02111.

    Whereas it has been demonstrated that muscle and nonmuscle isoactins are segregated into distinct cytoplasmic domains, the mechanism regulating subcellular sorting is unknown (Herman, 1993a). To reveal whether isoform-specific actin-binding proteins function to coordinate these events, cell extracts derived from motile (Em) versus stationary (Es) cytoplasm were selectively and sequentially fractionated over filamentous isoactin affinity columns prior to elution with a KCl step gradient. A polypeptide of interest, which binds specifically to beta-actin filament columns, but not to muscle actin columns has been conclusively identified as the ERM family member, ezrin. We studied ezrin-beta interactions in vitro by passing extracts (Em) over isoactin affinity matrices in the presence of Ca(2+)-containing versus Ca(2+)-free buffers, with or without cytochalasin D. Ezrin binds and can be released from beta-actin Sepharose-4B in the presence of Mg2+/EGTA and 100 mM NaCl (at 4 degrees C and room temperature), but not when affinity fractionation of Em is carried out in the presence of 0.2 mM CaCl2 or 2 microM cytochalasin D. N-acetyl-(leucyl)2-norleucinal and E64, two specific inhibitors of the calcium-activated protease, calpain I, protect ezrin binding to beta actin in the presence of calcium. Moreover, biochemical analysis of endothelial lysates reveals that a calpain I cleavage product of ezrin emerges when cell locomotion is stimulated in response to monolayer injury. Immunofluorescence analysis of leading lamellae reveals that anti-ezrin and anti-beta-actin IgGs can be simultaneously co-localized, extending the results of isoactin affinity fractionation of Em-derived extracts and suggesting that ezrin and beta-actin interact in vivo. To test the hypothesis that ezrin binds directly to beta-actin, we performed three sets of studies under a wide range of physiological conditions (pH 7.0-8.5) using purified pericyte ezrin and either alpha- or beta-actin. These included co-sedimentation, isoactin affinity fractionation, and co-immunoprecipitation. Results of these experiments reveal that purified ezrin does not directly bind to beta-actin filaments, either in solution or while isoactins are covalently cross-linked to Sepharose-4B. This is in contrast to our finding that ezrin and beta-actin could be co-immunoprecipitated or co-sedimented from Em-derived cell lysates. To explore whether calcium transients occur in cellular domains enriched in ezrin and beta-actin, we mapped cellular free calcium in endothelial monolayers crawling in response to injury.(ABSTRACT TRUNCATED AT 400 WORDS)

    Funded by: NEI NIH HHS: EY 09033; NIGMS NIH HHS: GM 47864

    The Journal of cell biology 1995;128;5;837-48

  • Ezrin has a COOH-terminal actin-binding site that is conserved in the ezrin protein family.

    Turunen O, Wahlström T and Vaheri A

    Haartman Institute, Department of Virology, Helsinki University, Finland.

    Ezrin, previously also known as cytovillin, p81, and 80K, is a cytoplasmic protein enriched in microvilli and other cell surface structures. Ezrin is postulated to have a membrane-cytoskeleton linker role. Recent findings have also revealed that the NH2-terminal domain of ezrin is associated with the plasma membrane and the COOH-terminal domain with the cytoskeleton (Algrain, M., O. Turunen, A. Vaheri, D. Louvard, and M. Arpin. 1993. J. Cell Biol. 120: 129-139). Using bacterially expressed fragments of ezrin we now demonstrate that ezrin has an actin-binding capability. We used glutathione-S-transferase fusion proteins of truncated ezrin in affinity chromatography to bind actin from the cell extract or purified rabbit muscle actin. We detected a binding site for filamentous actin that was localized to the COOH-terminal 34 amino acids of ezrin. No binding of monomeric actin was detected in the assay. The region corresponding to the COOH-terminal actin-binding site in ezrin is highly conserved in moesin, actin-capping protein radixin and EM10 protein of E. multilocularis, but not in merlin/schwannomin. Consequently, this site is a potential actin-binding site also in the other members of the protein family. Furthermore, the actin-binding site in ezrin shows sequence homology to the actin-binding site in the COOH terminus of the beta subunit of the actin-capping protein CapZ and one of the potential actin-binding sites in myosin heavy chain. The actin-binding capability of ezrin supports its proposed role as a membrane-cytoskeleton linker.

    The Journal of cell biology 1994;126;6;1445-53

  • Ezrin has properties to self-associate at the plasma membrane.

    Andréoli C, Martin M, Le Borgne R, Reggio H and Mangeat P

    CNRS URA 1856, Université Montpellier II, Département Biologie-Santé, France.

    Ezrin, a member of a family of proteins involved in the interaction of the microfilament cytoskeleton with the plasma membrane, plays a role in membrane translocation in gastric parietal cells (Hanzel, D., Reggio, H., Bretscher, A., Forte, J. G. and Mangeat, P. (1991). EMBO J. 10, 2363-2373). Human ezrin was expressed in and purified from Escherichia coli. It possesses all the major biophysical, immunological and physiological properties of natural ezrin. Upon microinjection in live gastric HGT-1 cells, ezrin was incorporated into the dorsal microvilli, a site where the endogeneous protein is localized. By coimmunoprecipitation and ezrin-affinity assays, two HGT-1 cell proteins of 77 and 72 kDa behaved as ezrin-binding proteins. In enriched gastric apical membranes, 125I-ezrin labelled proteins of 80, 77 and 72 kDa by overlay assay. The 80 kDa protein was identified as ezrin and the 77 and 72 kDa proteins as gastric forms of proteins structurally related to ezrin, such as radixin and moesin. In insect cells infected with a recombinant baculovirus, one-third of over-expressed ezrin accumulated at the plasma membrane. Ezrin bound a 77 kDa endogenous peripheral membrane protein, behaving as an insect counterpart of the mammalian ezrin family. In addition to the respective role of the amino- and carboxyl-terminal domains of ezrin in linking the membrane and the cytoskeleton (Algrain, M., Turunen, O., Vaheri, A., Louvard, D. and Arpin, M. (1993). J. Cell Biol. 120, 129-139), both domains interacted synergistically in a salt-dependent manner to trigger self-association of ezrin. Ezrin's self-association properties could represent another way of regulating the number of ezrin molecules bound at specific membrane sites.

    Journal of cell science 1994;107 ( Pt 9);2509-21

  • Subregional mapping of 8 single copy loci to chromosome 6 by fluorescence in situ hybridization.

    Rao PH, Murty VV, Gaidano G, Hauptschein R, Dalla-Favera R and Chaganti RS

    Laboratory of Cancer Genetics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.

    We have subregionally mapped 8 independently derived probes which have been assigned to chromosome 6 (D6S61, D6S134, D6S149, D6S155, MACS, VIL2, IGF2R and PLG) by FISH. All the probes were mapped to the long arm of chromosome 6 except D6S61, which was assigned to the short arm at 6p25. The remaining probes were clustered at the 6q25-->q27 region except MACS which was mapped to 6q22.2.

    Funded by: NCI NIH HHS: CA-34775, CA-44029

    Cytogenetics and cell genetics 1994;66;4;272-3

  • Heterotypic and homotypic associations between ezrin and moesin, two putative membrane-cytoskeletal linking proteins.

    Gary R and Bretscher A

    Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853.

    Ezrin and moesin are components of actin-rich cell surface structures that are thought to function as membrane-cytoskeletal linking proteins. Here we show that a stable complex of ezrin and moesin can be isolated from cultured cells by immunoprecipitation with specific antibodies. The capacity of these two proteins to interact directly was confirmed with a blot-overlay procedure in which biotin-tagged proteins in solution were incubated with immobilized binding partners. In addition to the heterotypic association of ezrin and moesin, homotypic binding of ezrin to ezrin and of moesin to moesin was also demonstrated in vitro. These results suggest mechanisms by which ezrin and moesin might participate in dynamic aspects of cortical cytoskeletal structure.

    Funded by: NIGMS NIH HHS: GM07273, GM36652

    Proceedings of the National Academy of Sciences of the United States of America 1993;90;22;10846-50

  • Identification of the two major epidermal growth factor-induced tyrosine phosphorylation sites in the microvillar core protein ezrin.

    Krieg J and Hunter T

    Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92186.

    In response to epidermal growth factor (EGF) the microvillar core protein ezrin is phosphorylated transiently to a high level on tyrosine residues in human epidermoid carcinoma A431 cells. Here we report the identification of the tyrosine phosphorylation sites in ezrin using bacterially expressed protein as a substrate for in vitro phosphorylation with the EGF receptor. The two major phosphotyrosine-containing peptides observed in vivo were also phosphorylated in vitro. By secondary digestions and site-directed mutagenesis tyrosines 145 and 353 were identified as the sites of phosphorylation. One of the sites, Tyr145, lies in the N-terminal region of homology that is common to the band 4.1-talin-ezrin protein family. This tyrosine residue and its vicinal amino acids are conserved throughout the family members, including radixin, moesin, and the two phosphotyrosine phosphatases, PTP H1 and PTP MEG, but not in band 4.1 or talin. Tyr353 is localized within the alpha-helical domain of ezrin and comparison of the protein sequences reveals that this site is unique to ezrin.

    Funded by: NCI NIH HHS: CA-39780

    The Journal of biological chemistry 1992;267;27;19258-65

  • Identification of ezrin as an 81-kDa tyrosine-phosphorylated protein in T cells.

    Egerton M, Burgess WH, Chen D, Druker BJ, Bretscher A and Samelson LE

    Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.

    We have used APT affinity purification to isolate tyrosine-phosphorylated proteins from MRL lpr/lpr (lpr) mouse T cells. One such protein is pp81 ezrin, previously identified as a tyrosine-phosphorylated protein in epidermal growth factor-stimulated A431 carcinoma cells. Biochemical analyses in A431 and gastric parietal cells have revealed ezrin to be a cytoskeleton-associated cytosolic protein. In Jurkat T cells, however, using similar methods we have shown ezrin to be a cytosolic protein with no measurable cytoskeletal association. We also observed no increases in ezrin tyrosine phosphorylation in TCR-stimulated Jurkat T cells, unless the cells were pretreated with protein tyrosine phosphatase inhibitors, suggesting that T cell ezrin tyrosine phosphorylation is tightly controlled by protein tyrosine phosphatases. The fraction of tyrosine phosphorylated ezrin in lpr T cells was 5 to 10 times that observed in Jurkat T cells, which along with constitutive TCR-zeta phosphorylation and pp60fyn overexpression, is a feature of the lpr defect.

    Journal of immunology (Baltimore, Md. : 1950) 1992;149;6;1847-52

  • Moesin: a member of the protein 4.1-talin-ezrin family of proteins.

    Lankes WT and Furthmayr H

    Department of Pathology, Stanford University School of Medicine, CA 94305.

    Moesin (membrane-organizing extension spike protein, pronounced mó ez in) has previously been isolated from bovine uterus and characterized as a possible receptor protein for heparan sulfate. We now have cloned and sequenced its complete cDNA, which represents a single 4.2-kilobase mRNA encoding a protein of 577 amino acids. It contains no apparent signal peptide or transmembrane domain. In addition, the protein shows significant sequence identity (72%) to ezrin (cytovillin, p81), as well as similarity to protein 4.1 and talin. All of the latter proteins have been postulated to serve as structural links between the plasma membrane and the cytoskeleton. A similar role for moesin is implied by structure and domain predictions derived from the cDNA-deduced peptide sequence. Furthermore, our data indicate that moesin is identical to the 77-kDa band that copurifies with ezrin in its isolation from human placenta [Bretscher, A. (1989) J. Cell Biol. 108, 921-930].

    Proceedings of the National Academy of Sciences of the United States of America 1991;88;19;8297-301

  • Cloning and characterisation of an immunodominant major surface antigen of Echinococcus multilocularis.

    Frosch PM, Frosch M, Pfister T, Schaad V and Bitter-Suermann D

    Institut für Medizinische Mikrobiologie, Medizinische Hochschule Hannover, F.R.G.

    A lambda gt11 cDNA expression library from mRNA of Echinococcus multilocularis protoscolices has been constructed in Escherichia coli Y1090. Immunoscreening with pooled sera obtained from patients suffering from E. multilocularis disease revealed 5 reactive clones. By partial DNA sequence comparison all clones proved to encode the same gene. The complete cDNA sequence of the clone pEM10 with the largest insert of 2.2 kb was determined and an open reading frame of 1.7 kb could be described. The derived amino acid sequence shares 42.6% identity with human microvillar cytovillin found in the membranes of placenta and carcinoma tissues. The coding region of the cDNA of pEM10 was amplified by polymerase chain reaction (PCR) and cloned in frame into expression vector pGEX-3X. Immunoblot analysis revealed the expression of a recombinant antigen of 65 kDa and a protein with the same molecular weight was also found in the lysate of E. multilocularis protoscolices. In contrast, the protein was absent from hydatid fluid or larvae of Echinococcus granulosus. By means of immunofluorescence studies this immunodominant antigen could be located in the germinal layer of brood capsules and in the tegument of E. multilocularis protoscolices. The fusion protein was purified and used for diagnostic purposes in immunoblot. The diagnostic value of this antigen is discussed.

    Molecular and biochemical parasitology 1991;48;2;121-30

  • cDNA cloning and sequencing of the protein-tyrosine kinase substrate, ezrin, reveals homology to band 4.1.

    Gould KL, Bretscher A, Esch FS and Hunter T

    Molecular Biology and Virology Laboratory, Salk Institute, San Diego, CA 92138.

    Ezrin is a component of the microvilli of intestinal epithelial cells and serves as a major cytoplasmic substrate for certain protein-tyrosine kinases. We have cloned and sequenced a human ezrin cDNA and report here the entire protein sequence derived from the nucleotide sequence of the cDNA as well as from partial direct protein sequencing. The deduced protein sequence indicates that ezrin is a highly charged protein with an overall pI of 6.1 and a calculated molecular mass of 69,000. The cDNA clone was used to survey the distribution of the ezrin transcript, and the 3.2 kb ezrin mRNA was found to be expressed in the same tissues that are known to express the protein and at the same relative levels. Highest expression was found in intestine, kidney and lung. The cDNA clone hybridized to DNAs from widely divergent organisms indicating that its sequence is highly conserved throughout evolution. The amino acid sequence of ezrin revealed a high degree of similarity within its N-terminal domain to the erythrocyte cytoskeletal protein, band 4.1 and secondary structure predictions indicate that a second region of ezrin contains a long alpha-helix, a feature also common to band 4.1. The structural similarity of ezrin to band 4.1 suggests a mechanism for the observed localization to the membrane, and a role for ezrin in modulating the association of the cortical cytoskeleton with the plasma membrane.

    Funded by: NCI NIH HHS: CA-39785

    The EMBO journal 1989;8;13;4133-42

  • Cytovillin, a microvillar Mr 75,000 protein. cDNA sequence, prokaryotic expression, and chromosomal localization.

    Turunen O, Winqvist R, Pakkanen R, Grzeschik KH, Wahlström T and Vaheri A

    Department of Virology, University of Helsinki, Finland. ff

    Cytovillin is a microvillar cytoplasmic peripheral membrane protein, with prominent expression in vivo in placental syncytiotrophoblasts and certain human tumors. Cytovillin cDNA was cloned from a human placental lambda gt11 library using affinity purified antibodies. The identity of cytovillin cDNA clones was confirmed by expression of cytovillin in Escherichia coli and using antibodies raised against the expressed fusion protein in comparison with antibodies against cytovillin purified from cultured human choriocarcinoma cells. In these cells Northern blotting analysis identified a major 3.5-kilobase cytovillin mRNA. The cDNA encodes a protein of 575 amino acids corresponding to a molecular weight of 68,084. According to secondary structure prediction, cytovillin is a hydrophilic protein with an extensive internal alpha-helical region ending in a sequence of 7 consecutive prolines. The predicted alpha-helical region showed limited homology to alpha-helical regions of cytoskeletal proteins and certain other proteins, but no extensive homologies were found in the cytovillin cDNA or the deduced amino acid sequence to other registered DNA or protein sequences. Southern blot analysis of a DNA panel of human mouse somatic cell hybrids localized the cytovillin gene to the end of the long arm of chromosome 6 (6q22-q27). Our results show that cytovillin is representative of a novel class of microvillar proteins.

    The Journal of biological chemistry 1989;264;28;16727-32

  • Cytovillin and other microvillar proteins of human choriocarcinoma cells.

    Pakkanen R and Vaheri A

    Department of Virology, University of Helsinki, Finland.

    Microvilli were isolated from cultured human JEG-3 choriocarcinoma cells using a gentle shearing method. The protein components of the isolated microvilli were examined by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The major Mr 42,000 and Mr 100,000 polypeptide bands reacted with anti-actin and anti-alpha-actinin antisera, respectively. Extraction of the isolated JEG-3 microvilli with Triton X-100 left an insoluble cytoskeletal residue containing mainly actin, alpha-actin, and polypeptides of Mr 200,000, 55,000 and 35,000. The Mr 35,000 polypeptide remained insoluble only at high concentrations of free Ca2+. Immunoblotting analysis of the JEG-3 microvilli indicated that they were devoid of tropomyosin, although the total JEG-3 protein lysates gave a strong positive reaction with anti-tropomyosin antiserum. The different subcellular localization of cytovillin and tropomyosin was also shown by indirect immunofluorescence microscopy. Cytovillin, an Mr 75,000 microvillus-specific membrane protein of JEG-3 cells, existed in an oligomeric form (dimer or trimer) as shown by gel filtration of Triton X-100 solubilized microvillar proteins and by native polyacrylamide gel electrophoresis of purified cytovillin. Disulfide bridges were not involved in the aggregation, because the mobility of cytovillin was similar under reducing and nonreducing conditions in SDS-PAGE. Cytovillin was shown to be closely related to ezrin, a minor component of chicken intestinal brush border microvilli.

    Journal of cellular biochemistry 1989;41;1;1-12

  • Activation of carcinogenic arylhydroxamic acids by human tissues.

    King CM, Olive CW and Cardona RA

    Incubation of the carcinogenic arylhydroxamic acids N-hydroxy-N-2-fluorenylacetamide or N-hydroxy-N-4-biphenylacetamide and tRNA with 105,000 times g supernatants of homogenates of human small intestine, liver, or colon led to formation of arylamine-substituted nucleic acid adducts. These data indicated that enzymes of human tissues could activate arylhydroxamic acids by N leads to O acyl transfer. The unstable N-acetoxyarylamines formed by these enzymes reacted spontaneously with the tRNA to give covalently linked adducts with the nucleic acid.

    Journal of the National Cancer Institute 1975;55;2;285-7

Gene lists (6)

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
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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