G2Cdb::Gene report

Gene id
G00001662
Gene symbol
IMPA1 (HGNC)
Species
Homo sapiens
Description
inositol(myo)-1(or 4)-monophosphatase 1
Orthologue
G00000413 (Mus musculus)

Databases (7)

Gene
ENSG00000133731 (Ensembl human gene)
3612 (Entrez Gene)
758 (G2Cdb plasticity & disease)
IMPA1 (GeneCards)
Literature
602064 (OMIM)
Marker Symbol
HGNC:6050 (HGNC)
Protein Sequence
P29218 (UniProt)

Literature (20)

Pubmed - other

  • Shifted Transversal Design smart-pooling for high coverage interactome mapping.

    Xin X, Rual JF, Hirozane-Kishikawa T, Hill DE, Vidal M, Boone C and Thierry-Mieg N

    Banting and Best Department of Medical Research and Department of Molecular Genetics, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada.

    "Smart-pooling," in which test reagents are multiplexed in a highly redundant manner, is a promising strategy for achieving high efficiency, sensitivity, and specificity in systems-level projects. However, previous applications relied on low redundancy designs that do not leverage the full potential of smart-pooling, and more powerful theoretical constructions, such as the Shifted Transversal Design (STD), lack experimental validation. Here we evaluate STD smart-pooling in yeast two-hybrid (Y2H) interactome mapping. We employed two STD designs and two established methods to perform ORFeome-wide Y2H screens with 12 baits. We found that STD pooling achieves similar levels of sensitivity and specificity as one-on-one array-based Y2H, while the costs and workloads are divided by three. The screening-sequencing approach is the most cost- and labor-efficient, yet STD identifies about twofold more interactions. Screening-sequencing remains an appropriate method for quickly producing low-coverage interactomes, while STD pooling appears as the method of choice for obtaining maps with higher coverage.

    Funded by: NHGRI NIH HHS: R01 HG001715, R01-HG001715

    Genome research 2009;19;7;1262-9

  • Spatial expression patterns and biochemical properties distinguish a second myo-inositol monophosphatase IMPA2 from IMPA1.

    Ohnishi T, Ohba H, Seo KC, Im J, Sato Y, Iwayama Y, Furuichi T, Chung SK and Yoshikawa T

    Laboratory for Molecular Psychiatry, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan. tohnishi@brain.riken.jp

    Lithium is used in the clinical treatment of bipolar disorder, a disease where patients suffer mood swings between mania and depression. Although the mode of action of lithium remains elusive, a putative primary target is thought to be inositol monophosphatase (IMPase) activity. Two IMPase genes have been identified in mammals, the well characterized myo-inositol monophosphatase 1 (IMPA1) and myo-inositol monophosphatase 2 (IMPA2). Several lines of genetic evidence have implicated IMPA2 in the pathogenesis of not only bipolar disorder but also schizophrenia and febrile seizures. However, little is known about the protein, although it is predicted to have lithium-inhibitable IMPase activity based on its homology to IMPA1. Here we present the first biochemical study comparing the enzyme activity of IMPA2 to that of IMPA1. We demonstrate that in vivo, IMPA2 forms homodimers but no heterodimers with IMPA1. Recombinant IMPA2 exhibits IMPase activity, although maximal activity requires higher concentrations of magnesium and a higher pH. IMPA2 shows significantly lower activity toward myo-inositol monophosphate than IMPA1. We therefore screened for additional substrates that could be more efficiently dephosphorylated by IMPA2, but failed to find any. Importantly, when using myo-inositol monophosphate as a substrate, the IMPase activity of IMPA2 was inhibited at high lithium and restricted magnesium concentrations. This kinetics distinguishes it from IMPA1. We also observed a characteristic pattern of differential expression between IMPA1 and IMPA2 in a selection of tissues including the brain, small intestine, and kidney. These data suggest that IMPA2 has a separate function in vivo from that of IMPA1.

    The Journal of biological chemistry 2007;282;1;637-46

  • 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

  • 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

  • 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

  • Sequence comparison of human and mouse genes reveals a homologous block structure in the promoter regions.

    Suzuki Y, Yamashita R, Shirota M, Sakakibara Y, Chiba J, Mizushima-Sugano J, Nakai K and Sugano S

    Human Genome Center, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. ysuzuki@ims.u-tokyo.ac.jp

    Comparative sequence analysis was carried out for the regions adjacent to experimentally validated transcriptional start sites (TSSs), using 3324 pairs of human and mouse genes. We aligned the upstream putative promoter sequences over the 1-kb proximal regions and found that the sequence conservation could not be further extended at, on average, 510 bp upstream positions of the TSSs. This discontinuous manner of the sequence conservation revealed a "block" structure in about one-third of the putative promoter regions. Consistently, we also observed that G+C content and CpG frequency were significantly different inside and outside the blocks. Within the blocks, the sequence identity was uniformly 65% regardless of their length. About 90% of the previously characterized transcription factor binding sites were located within those blocks. In 46% of the blocks, the 5' ends were bounded by interspersed repetitive elements, some of which may have nucleated the genomic rearrangements. The length of the blocks was shortest in the promoters of genes encoding transcription factors and of genes whose expression patterns are brain specific, which suggests that the evolutional diversifications in the transcriptional modulations should be the most marked in these populations of genes.

    Genome research 2004;14;9;1711-8

  • Examination of IMPA1 and IMPA2 genes in manic-depressive patients: association between IMPA2 promoter polymorphisms and bipolar disorder.

    Sjøholt G, Ebstein RP, Lie RT, Berle JØ, Mallet J, Deleuze JF, Levinson DF, Laurent C, Mujahed M, Bannoura I, Murad I, Molven A and Steen VM

    Dr Einar Martens' Research Group for Biological Psychiatry and Locus on Neuroscience, Center for Medical Genetics and Molecular Medicine, University of Bergen, Norway.

    Manic-depressive (bipolar) illness is a serious psychiatric disorder with a strong genetic predisposition. The disorder is likely to be multifactorial and etiologically complex, and the causes of genetic susceptibility have been difficult to unveil. Lithium therapy is a widely used pharmacological treatment of manic-depressive illness, which both stabilizes the ongoing episodes and prevents relapses. A putative target of lithium treatment has been the inhibition of the myo-inositol monophosphatase (IMPase) enzyme, which dephosphorylates myo-inositol monophosphate in the phosphatidylinositol signaling system. Two genes encoding human IMPases have so far been isolated, namely myo-inositol monophosphatase 1 (IMPA1) on chromosome 8q21.13-21.3 and myo-inositol monophosphatase 2 (IMPA2) on chromosome 18p11.2. In the present study, we have scanned for DNA variants in the human IMPA1 and IMPA2 genes in a pilot sample of Norwegian manic-depressive patients, followed by examination of selected polymorphisms and haplotypes in a family-based bipolar sample of Palestinian Arab proband-parent trios. Intriguingly, two frequent single-nucleotide polymorphisms (-461C>T and -207T>C) in the IMPA2 promoter sequence and their corresponding haplotypes showed transmission disequilibrium in the Palestinian Arab trios. No association was found between the IMPA1 polymorphisms and bipolar disorder, neither with respect to disease susceptibility nor with variation in lithium treatment response. The association between manic-depressive illness and IMPA2 variants supports several reports on the linkage of bipolar disorder to chromosome 18p11.2, and sustains the possible role of IMPA2 as a susceptibility gene in bipolar disorder.

    Molecular psychiatry 2004;9;6;621-9

  • Myo-inositol monophosphatase is an activated target of calbindin D28k.

    Berggard T, Szczepankiewicz O, Thulin E and Linse S

    Department of Biophysical Chemistry, Lund University, Chemical Centre, P.O. Box 124, Sweden.

    Calbindin D(28k) (calbindin) is a member of the calmodulin superfamily of Ca(2+)-binding proteins. An intracellular target of calbindin was discovered using bacteriophage display. Human recombinant calbindin was immobilized on magnetic beads and used in affinity purification of phage-displayed peptides from a random 12-mer peptide library. One sequence, SYSSIAKYPSHS, was strongly selected both in the presence of Mg(2+) and in the presence of Ca(2+). Homology search against the protein sequence data base identified a closely similar sequence, ISSIKEKYPSHS, at residues 55-66 in myo-inositol-1(or 4)-monophosphatase (IMPase, EC ), which constitute a strongly conserved and exposed region in the three-dimensional structure. IMPase is a key enzyme in the regulation of the activity of the phosphatidylinositol-signaling pathway. It catalyzes the hydrolysis of myo-inositol-1(or 4)-monophosphate to form free myo-inositol, maintaining a supply that represents the precursor for inositol phospholipid second messenger signaling systems. Fluorescence spectroscopy showed that isolated calbindin and IMPase interact with an apparent equilibrium dissociation constant, K(D), of 0.9 microm. Both apo and Ca(2+)-bound calbindin was found to activate IMPase up to 250-fold, depending on the pH and substrate concentration. The activation is most pronounced at conditions that otherwise lead to a very low activity of IMPase, i.e. at reduced pH and at low substrate concentration.

    The Journal of biological chemistry 2002;277;44;41954-9

  • Inositol monophosphatase activity in normal, Down syndrome and dementia of the Alzheimer type CSF.

    Atack JR and Schapiro MB

    Merck Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex CM20 2QR, United Kingdom. john_atack@merck.com

    Inositol monophosphatase (IMPase), a cytoplasmic enzyme that hydrolyses inositol monophosphates to produce inositol is also found in the cerebrospinal fluid (CSF). Since levels of inositol have been previously reported to be elevated in Down syndrome (DS) CSF, IMPase activity was measured in CSF of DS subjects to establish whether altered inositol levels may be related to changes in IMPase activity. In addition, and to better understand the regulation of IMPase expression in the CSF, enzyme activity was measured in normal aging, patients with Alzheimer-type or multi-infarct dementia (DAT and MID, respectively) and in CSF obtained by repeat lumbar puncture or from sequential aliquots of CSF from along the rostro-caudal axis. IMPase activity was relatively constant in CSF obtained from repeated lumbar puncture and there was no significant rostro-caudal gradient of activity in either normal or DS subjects, indicating that the enzyme originates from both brain and spinal cord. Compared to respective age-matched normal subjects, CSF IMPase activity was unaltered in DS, DAT and MID. However, in normal volunteers there was a significant positive correlation between age and CSF IMPase activity. Furthermore, there were significant correlations between CSF IMPase activity and acetylcholinesterase and butyrylcholinesterase activities and total protein, suggesting co-regulation of these parameters within the CSF.

    Neurobiology of aging 2002;23;3;389-96

  • Production of monoclonal antibodies and immunohistochemical studies of brain myo-inositol monophosphate phosphatase.

    Bahn JH, Kim AY, Jang SH, Lee BR, Ahn JY, Joo HM, Kan TC, Won MH, Kwon HY, Kang JH, Kwon OS, Kim HB, Cho SW, Lee KS, Park J and Choi SY

    Division of Genetic Engineering, Hallym University, Chunchon, Korea.

    Five monoclonal antibodies that recognize porcine brain myo-inositol monophosphate phosphatase (IMPase) have been selected and designated as mAb IMPP 9, IMPP 10, IMPP 11, IMPP 15, and IMPP 17. These antibodies recognize different epitopes of the enzyme and one of these inhibited the enzyme activity. When the total proteins of the porcine brain homogenate separated by SDS-PAGE were probed with monoclonal antibodies, a single reactive protein band of 29 kDa, co-migrating with the purified porcine brain IMPase, was detected. Using the anti-IMPase antibodies as probes, the cross reactivities of the brain IMPase from human and other mammalian tissues, as well as from avian sources, were investigated. Among the human and animal tissues tested, the immunoreactive bands on Western blots appeared to have the same molecular mass of 29 kDa. In addition, there was IMPase immunoreactivity in the various neuronal populations in the rat brain. These results indicate that mammalian brains contain only one major type of immunologically similar IMPase, although some properties of the enzymes that were previously reported differ from each another. The first demonstration of the IMPase localization in the brain may also provide useful data for future investigations on the function of this enzyme in relation to various neurological diseases.

    Molecules and cells 2002;13;1;21-7

  • Effect of bipolar disorder on lymphocyte inositol monophosphatase mRNA levels.

    Nemanov L, Ebstein RP, Belmaker RH, Osher Y and Agam G

    Research Laboratory, S. Herzog Memorial Hospital, Jerusalem, Israel.

    The activity of inositol monophosphatase (IMPase), the lithium (Li)-inhibitable enzyme in the phosphatidylinositol (PI) signal transduction system, has recently been found significantly lower in lymphoblastoid cell lines from bipolar (BP) patients, particularly in Li-responders. To probe for possible quick detection of the disease and prediction of the therapeutic response we repeated our study in fresh lymphocytes. Since IMPase in fresh lymphocytes is inhibited in vivo by ongoing Li treatment and its pre-Li activity cannot be evaluated, IMPase mRNA levels were measured. Relative (to beta-actin) mRNA levels were quantified by reverse transcriptase (RT)-PCR in 5 drug-free and 31 drug-treated BP patients compared with 36 control subjects in fresh lymphocytes. In agreement with our findings with IMPase activity, the small group of drug-free BP patients exhibited approximately 2/3 reduction in IMPase relative mRNA levels compared to control subjects. Approximately 2-fold elevation of these levels toward control values was found for patients treated with Li and other mood stabilizers. The study further suggests the possible importance of IMPase in the aetiology of BP disorder and in the mediation of the therapeutic efficacy of Li. It may be that chronic inhibition of IMPase activity by Li results in up-regulation of its gene at the transcriptional level.

    The international journal of neuropsychopharmacology 1999;2;1;25-29

  • Genomic structure and chromosomal localization of a human myo-inositol monophosphatase gene (IMPA).

    Sjøholt G, Molven A, Løvlie R, Wilcox A, Sikela JM and Steen VM

    Dr. Einar Martens' Research Group for Biological Psychiatry, Center for Molecular Medicine, Haukeland University Hospital, Bergen, Norway.

    Manic-depressive illness is a serious psychiatric disorder that in many, but far from all, patients can be treated with lithium. The main causes for discontinuation of lithium therapy are unpleasant or serious side effects and lack of response. The reason for the striking variation in clinical efficacy of lithium treatment among bipolar patients is not known. The enzyme myo-inositol monophosphatase (IMPase) has been postulated as a target for the mood-stabilizing effects of lithium, but variation in the coding region of the human IMPA gene encoding IMPase activity has not been observed in manic-depressive patients (Steen et al., Pharmacogenetics, 1996, 6, 113-116). It is nevertheless conceivable that polymorphisms or mutations in the noncoding regions of this gene could influence the lithium response in psychiatric patients. As a first step in investigating this possibility, we here report the genomic structure of the human IMPA gene. The gene is composed of at least nine exons and covers more than 20 kb of sequence on chromosome 8q21.13-q21.3. In the 3'-untranslated part of the gene, we observed a polymorphism (a G to A transition) and also two short sequences similar to the inositol/cholin-responsive element consensus. Finally, we postulate that two additional IMPA-like transcripts originate from the human genome, one from a position close to IMPA itself on chromosome 8 and the other from chromosome 18p. Our data may contribute to the identification of genetic factors involved in the pathogenesis and determination of treatment response in manic-depressive illness.

    Genomics 1997;45;1;113-22

  • Molecular characterization of coding and untranslated regions of rat cortex lithium-sensitive myo-inositol monophosphatase cDNA.

    Parthasarathy L, Parthasarathy R and Vadnal R

    Molecular Neuroscience Laboratory, Mental Health and Behavioral Science Service, Department of Veterans Affairs Medical Center, Louisville, KY 40206, USA.

    Lithium sensitive myo-inositol monophosphatase (IMPase) is a pivotal enzyme which controls the levels of brain inositol within the inositol-based signaling system. Its capacity to release free myo-inositol from inositol monophosphates generated from receptor-linked and de novo pathways is crucial to the maintenance of appropriate amounts of intracellular myo-inositol, which is essential for both inositol-based cell signaling and cell volume control. We present here the full length cDNA encompassing the coding and untranslated regions (5'- and 3'-UTRs) of rat brain IMPase. This cDNA was derived from rat cortex mRNA by the RT-PCR technique. Analysis of this cDNA revealed several interesting features which include a short 5'-untranslated region (5'-UTR) of 68 nucleotides followed by coding region of approximately 0.8 kb and a long 3'-untranslated region (3'-UTR) of 1.2 kb. Both 5'-rapid amplification of cDNA ends (5'-RACE) and 3'-RACE techniques were carried out to isolate both UTRs and double stranded sequencing was carried out to its entirety (approximately 2.1 kb) by 'gene walking' using several oligonucleotide primers. All nucleotides were sequenced unambiguously using the sense and antisense strands of DNA. PCR analysis for the coding region and the deduced amino acid sequence demonstrated a DNA fragment of 831 bp and 277 amino acids, respectively, which are strikingly similar to human hippocampal IMPase. The 5'-UTR demonstrated distinct CpG doublets, characteristic of 'housekeeping' genes. The sequence around the initiator methionine, AAGATGG, conforms well to the Kozak consensus sequence for mammalian protein biosynthesis and the 3'-UTR demonstrated three canonical (AATAAT, AATTAA, AATACA) and one unusual polyadenylation signals (ATTAAA) followed by a 31 base poly(A) tail. The presence of a CCTGTG in the 3'-UTR (putative carbohydrate response element) links IMPase mRNA to brain carbohydrate metabolic pathways. Computer analyses demonstrated several unique features of this mRNA, including the potential formation of hairpin loops which might be important in its intracellular regulation and turn-over. In summary, this lithium-sensitive brain IMPase mRNA has the following characteristics: a 5'-CpG-rich short untranslated segment, a highly conserved coding region, and a long 3'-untranslated region with several polyadenylation signals.

    Gene 1997;191;1;81-7

  • The contribution of lysine-36 to catalysis by human myo-inositol monophosphatase.

    Ganzhorn AJ, Lepage P, Pelton PD, Strasser F, Vincendon P and Rondeau JM

    Marion Merrel Research Institute, Strasbourg, France. AxelGanzhorn@mmd.com

    The role of lysine residues in the catalytic mechanism of myo-inositol monophosphatase (EC 3.1.3.25) was investigated. The enzyme was completely inactivated by amidination with ethyl acetimidate or reductive methylation with formaldehyde and cyanoborohydride. Activity was retained when the active site was protected with Mg2+, Li+, and D,L-myo-inositol 1-phosphate. Using radiolabeling, peptide mapping, and sequence analysis, Lys-36 was shown to be the protected residue, which is responsible for inactivation. Replacing Lys-36 with glutamine produced a mutant protein, K36Q, with similar affinities for the substrate and the activator Mg2+, but a 50-fold lower turnover number as compared to the wild-type enzyme. Crystallographic studies did not indicate any gross structural changes in the mutant as compared to the native form. Initial velocity data were best described by a rapid equilibrium ordered mechanism with two Mg2+ binding before and a third one binding after the substrate. Inhibition by calcium was unaffected by the mutation, but inhibition by lithium was greatly reduced and became noncompetitive. The pH dependence of catalysis and the solvent isotope effect on kcat are altered in the mutant enzyme. D,L-myo-Inositol 1-phosphate, 4-nitrophenyl phosphate, and D-glucose 6-phosphate are cleaved at different rates by the wild-type enzyme, but with similar efficiency by K36Q. All data taken together are consistent with the hypothesis that modifying or replacing the lysine residue in position 36 decreases its polarizing effect on one of the catalytic metal ions and prevents the efficient deprotonation of the metal-bound water nucleophile.

    Biochemistry 1996;35;33;10957-66

  • Structural analysis of inositol monophosphatase complexes with substrates.

    Bone R, Frank L, Springer JP, Pollack SJ, Osborne SA, Atack JR, Knowles MR, McAllister G, Ragan CI, Broughton HB et al.

    Department of Biophysical Chemistry, Merck Research Laboratories, Rahway, New Jersey 07065.

    The structures of ternary complexes of human inositol monophosphatase with inhibitory Gd3+ and either D- or L-myo-inositol 1-phosphate have been determined to 2.2-2.3 A resolution using X-ray crystallography. Substrate and metal are bound identically in each active site of the phosphatase dimer. The substrate is present at full occupancy, while the metal is present at only 35% occupancy, suggesting that Li+ from the crystallization solvent partially replaces Gd3+ upon substrate binding. The phosphate groups of both substrates interact with the phosphatase in the same manner with one phosphate oxygen bound to the octahedrally coordinated active site metal and another oxygen forming hydrogen bonds with the amide groups of residues 94 and 95. The active site orientations of the inositol rings of D- and L-myo-inositol 1-phosphate differ by rotation of nearly 60 degrees about the phosphate ester bond. Each substrate utilizes the same key residues (Asp 93, Ala 196, Glu 213, and Asp 220) to form the same number of hydrogen bonds with the enzyme. Mutagenesis experiments confirm the interaction of Glu 213 with the inositol ring and suggest that interactions with Ser 165 may develop during the transition state. The structural data suggest that the active site nucleophile is a metal-bound water that is activated by interaction with Glu 70 and Thr 95. Expulsion of the ester oxygen appears to be promoted by three aspartate residues acting together (90, 93, and 220), either to donate a proton to the leaving group or to form another metal binding site from which a second Mg2+ coordinates the leaving group during the transition state.

    Biochemistry 1994;33;32;9460-7

  • Structural studies of metal binding by inositol monophosphatase: evidence for two-metal ion catalysis.

    Bone R, Frank L, Springer JP and Atack JR

    Department of Biophysical Chemistry, Merck Research Laboratories, Rahway, New Jersey 07065.

    The structure of inositol monophosphatase has been determined to 2.60 A resolution in complexes with Mn2+ and with Mn2+ and phosphate. In the Mn2+ complex, three metal cations and one Cl were bound in the active site on each of the two subunits of the enzyme. Ligands to the three metals include the side chains of Glu 70, Asp 90, Asp 93, and Asp 220, t he carbonyl group of Ile 92, several solvent molecules and the chloride, which is a ligand to each of the cations. When phosphate is soaked into these Mn2+ cocrystals, one of the three Mn2+ ions is expelled from the active site, leaving metal ions with octahedral and tetrahedral coordination geometry. In addition, the structure of apoinositol monophosphatase was determined to 2.5 A resolution. Residues 70-75, a two-turn helical segment which is involved in metal coordination, moves away from the metal binding site by 2-3 A in the absence of cations. Residues 30-40, which wrap around the metal binding site and interact with the metal indirectly through solvent molecules and protein ligands to the metal, become disordered in the absence of metal. In various metal complexes, segmental mobility is also observed in the residues which form the metal binding sites. The results of these studies of the interaction of inositol monophosphatase with cations suggest that the enzyme accomplishes phosphate ester hydrolysis using two metal ions, one with octahedral and one with tetrahedral coordination geometry. Broad metal-binding specificity appears to result from extensive flexibility in several of the protein segments which contribute metal ligands, from the presence of alternate metal ligands and from metal coordination spheres which include water molecules.

    Biochemistry 1994;33;32;9468-76

  • Structure of inositol monophosphatase, the putative target of lithium therapy.

    Bone R, Springer JP and Atack JR

    Department of Biophysical Chemistry, Merck Research Laboratories, Rahway, NJ 07065.

    Inositol monophosphatase (EC 3.1.3.25), the putative molecular site of action of lithium therapy for manic-depressive illness, plays a key role in the phosphatidylinositol signaling pathway by catalyzing the hydrolysis of inositol monophosphates. To provide a structural basis from which to design better therapeutic agents for manic-depressive illness, the structure of human inositol monophosphatase has been determined to 2.1-A resolution by using x-ray crystallography. The enzyme exists as a dimer of identical subunits, each folded into a five-layered sandwich of three pairs of alpha-helices and two beta-sheets. Sulfate and an inhibitory lanthanide cation (Gd3+) are bound at identical sites on each subunit and establish the positions of the active sites. Each site is located in a large hydrophilic cavern that is at the base of the two central helices where several segments of secondary structure intersect. Comparison of the phosphatase aligned sequences of several diverse genes with the phosphatase structure suggests that the products of these genes and the phosphatase form a structural family with a conserved metal binding site.

    Proceedings of the National Academy of Sciences of the United States of America 1992;89;21;10031-5

  • cDNA cloning of human and rat brain myo-inositol monophosphatase. Expression and characterization of the human recombinant enzyme.

    McAllister G, Whiting P, Hammond EA, Knowles MR, Atack JR, Bailey FJ, Maigetter R and Ragan CI

    Merck Sharp and Dohme Research Laboratories, Harlow, Essex, U.K.

    Inositol monophosphatase (EC 3.1.3.25) is a key enzyme in the phosphoinositide cell-signalling system. Its role is to provide inositol required for the resynthesis of phosphatidylinositol and polyphosphoinositides. It is the probable pharmacological target for lithium action in brain. Using probes derived from the bovine inositol monophosphatase cDNA we have isolated cDNA clones encoding the human and rat brain enzymes. The enzyme is highly conserved in all three species (79% identical). The coding region of the human cDNA was inserted into a bacterial expression vector. The expressed recombinant enzyme was purified and its biochemical properties examined. The human enzyme is very similar to the bovine enzyme.

    The Biochemical journal 1992;284 ( Pt 3);749-54

  • The effects of lithium ion and other agents on the activity of myo-inositol-1-phosphatase from bovine brain.

    Hallcher LM and Sherman WR

    myo-Inositol-1-phosphatase has been partially purified from bovine brain. The enzyme has a molecular weight of about 58,000. Both L-myo-inositol 1-phosphate and D-myo-inositol 1-phosphate are hydrolyzed by the enzyme as well as (-)-chiro-inositol 3-phosphate and 2'-AMP. Triphosphoinositide is not a substrate. The phosphatase is completely dependent on Mg2+, which has a Km of 1 mM. Calcium and manganese ions are competitive inhibitors of Mg2+ binding with Ki values of 18 microM and 2 microM, respectively. Lithium chloride inhibits the hydrolysis of both L- and D-myo-inositol 1-phosphate to the extent of 50% at a concentration of 0.8 mM. The phosphatase from testis is similarly inhibited by lithium. Lithium ion is a noncompetitive inhibitor of Mg2+ binding and an uncompetitive inhibitor of myo-inositol 1-phosphate binding. Because lithium chloride administration elicits both an increase in the levels of myo-inositol 1-phosphate and a decrease in the levels of myo-inositol in rat brain (Allison, 1978), and because these actions are blocked by anticholinergic agents, we examined the effects of cholinergic agonists and antagonists on the enzyme and found none. The possibility that the inhibition of this enzyme by lithium ion is related to the pharmacological actions of lithium is discussed.

    Funded by: NIADDK NIH HHS: AM-20579; NINDS NIH HHS: NS-05159, NS-13781

    The Journal of biological chemistry 1980;255;22;10896-901

Gene lists (3)

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
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
© 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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