The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Morgan Sheng - One of the best experts on this subject based on the ideXlab platform.
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an intramolecular interaction between src homology 3 domain and Guanylate Kinase like domain required for channel clustering by postsynaptic density 95 sap90
The Journal of Neuroscience, 2000Co-Authors: Hyewon Shin, Yi-ping Hsueh, Fu-chia Yang, Eunjoon Kim, Morgan ShengAbstract:Members of the postsynaptic density-95 (PSD-95)/SAP90 family of membrane-associated Guanylate Kinase (MAGUK) proteins function as multimodular scaffolds that organize protein-signaling complexes at neuronal synapses. MAGUK proteins contain PDZ, Src homology 3 (SH3), and Guanylate Kinase (GK)-like domains, all of which can function as sites for specific protein–protein interactions. We report here a direct protein–protein interaction between the SH3 domain and the GK region in the PSD-95 family of MAGUKs. The SH3 domain of the PSD-95 family appears to have an atypical binding specificity, because the classical SH3 binding (-P-X-X-P-) motif is absent from the GK domain. Although SH3–GK binding can occur in either an intramolecular or intermolecular manner, the intramolecular mode is preferred, possibly because of additional tertiary interactions available when the SH3 and GK domains are adjacent in the same polypeptide. Mutations disrupting the intramolecular SH3–GK interaction do not interfere with PSD-95 association with the K+ channel Kv1.4 or with the GK domain-binding protein GKAP. The same mutations, however, inhibit the clustering of Kv1.4 by PSD-95, suggesting that the intramolecular SH3–GK interaction may modulate the clustering activity of PSD-95.
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Nuclear translocation and transcription regulation by the membrane-associated Guanylate Kinase CASK/LIN-2
Nature, 2000Co-Authors: Yi-ping Hsueh, Ting-fang Wang, Fu-chia Yang, Morgan ShengAbstract:Membrane-associated Guanylate Kinases (MAGUKs) contain multiple protein-binding domains that allow them to assemble specific multiprotein complexes in particular regions of the cell1,2. CASK/LIN-2, a MAGUK required for EGF receptor localization and signalling in Caenorhabditis elegans, contains a calmodulin-dependent protein Kinase-like domain followed by PDZ, SH3 and Guanylate Kinase-like domains3,4,5. In adult rat brain, CASK is concentrated at neuronal synapses and binds to the cell-surface proteins neurexin and syndecan6,7,8 and the cytoplasmic proteins Mint/LIN-10 and Veli/LIN-7 (refs 4, 9, 10). Here we report that, through its Guanylate Kinase domain, CASK interacts with Tbr-1, a T-box transcription factor that is involved in forebrain development11,12. CASK enters the nucleus and binds to a specific DNA sequence (the T-element) in a complex with Tbr-1. CASK acts as a coactivator of Tbr-1 to induce transcription of T-element containing genes, including reelin, a gene that is essential for cerebrocortical development. Our findings show that a MAGUK which is usually associated with cell junctions has a transcription regulation function.
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nuclear translocation and transcription regulation by the membrane associated Guanylate Kinase cask lin 2
Nature, 2000Co-Authors: Yi-ping Hsueh, Ting-fang Wang, Fu-chia Yang, Morgan ShengAbstract:Membrane-associated Guanylate Kinases (MAGUKs) contain multiple protein-binding domains that allow them to assemble specific multiprotein complexes in particular regions of the cell. CASK/LIN-2, a MAGUK required for EGF receptor localization and signalling in Caenorhabditis elegans, contains a calmodulin-dependent protein Kinase-like domain followed by PDZ, SH3 and Guanylate Kinase-like domains. In adult rat brain, CASK is concentrated at neuronal synapses and binds to the cell-surface proteins neurexin and syndecan and the cytoplasmic proteins Mint/LIN-10 and Veli/LIN-7. Here we report that, through its Guanylate Kinase domain, CASK interacts with Tbr-1, a T-box transcription factor that is involved in forebrain development. CASK enters the nucleus and binds to a specific DNA sequence (the T-element) in a complex with Tbr-1. CASK acts as a coactivator of Tbr-1 to induce transcription of T-element containing genes, including reelin, a gene that is essential for cerebrocortical development. Our findings show that a MAGUK which is usually associated with cell junctions has a transcription regulation function.
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Nuclear translocation and transcription regulation by the membrane-associated Guanylate Kinase CASK/LIN-2
Nature, 2000Co-Authors: Yi-ping Hsueh, Ting-fang Wang, Fu-chia Yang, Morgan ShengAbstract:Membrane-associated Guanylate Kinases (MAGUKs) contain multiple protein-binding domains that allow them to assemble specific multiprotein complexes in particular regions of the cell. CASK/LIN-2, a MAGUK required for EGF receptor localization and signalling in Caenorhabditis elegans, contains a calmodulin-dependent protein Kinase-like domain followed by PDZ, SH3 and Guanylate Kinase-like domains. In adult rat brain, CASK is concentrated at neuronal synapses and binds to the cell-surface proteins neurexin and syndecan and the cytoplasmic proteins Mint/LIN-10 and Veli/LIN-7. Here we report that, through its Guanylate Kinase domain, CASK interacts with Tbr-1, a T-box transcription factor that is involved in forebrain development. CASK enters the nucleus and binds to a specific DNA sequence (the T-element) in a complex with Tbr-1. CASK acts as a coactivator of Tbr-1 to induce transcription of T-element containing genes, including reelin, a gene that is essential for cerebrocortical development. Our findings show that a MAGUK which is usually associated with cell junctions has a transcription regulation function.
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gkap a novel synaptic protein that interacts with the Guanylate Kinase like domain of the psd 95 sap90 family of channel clustering molecules
Journal of Cell Biology, 1997Co-Authors: Eunjoon Kim, Yi-ping Hsueh, Scott Naisbitt, Anuradha Rao, Adam Rothschild, Ann Marie Craig, Morgan ShengAbstract:The molecular mechanisms underlying the organization of ion channels and signaling molecules at the synaptic junction are largely unknown. Recently, members of the PSD-95/SAP90 family of synaptic MAGUK (membrane-associated Guanylate Kinase) proteins have been shown to interact, via their NH2-terminal PDZ domains, with certain ion channels (NMDA receptors and K+ channels), thereby promoting the clustering of these proteins. Although the function of the NH2-terminal PDZ domains is relatively well characterized, the function of the Src homology 3 (SH3) domain and the Guanylate Kinase-like (GK) domain in the COOH-terminal half of PSD-95 has remained obscure. We now report the isolation of a novel synaptic protein, termed GKAP for Guanylate Kinase-associated protein, that binds directly to the GK domain of the four known members of the mammalian PSD-95 family. GKAP shows a unique domain structure and appears to be a major constituent of the postsynaptic density. GKAP colocalizes and coimmunoprecipitates with PSD-95 in vivo, and coclusters with PSD-95 and K+ channels/ NMDA receptors in heterologous cells. Given their apparent lack of Guanylate Kinase enzymatic activity, the fact that the GK domain can act as a site for protein– protein interaction has implications for the function of diverse GK-containing proteins (such as p55, ZO-1, and LIN-2/CASK).
Manfred Konrad - One of the best experts on this subject based on the ideXlab platform.
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^1H, ^13C and ^15N resonance assignment of human Guanylate Kinase
Biomolecular NMR Assignments, 2018Co-Authors: Nazimuddin Khan, Manfred Konrad, Pablo Trigo-mourino, Marta G. Carneiro, T. Michael SaboAbstract:Human Guanylate Kinase (hGMPK) is a critical enzyme that, in addition to phosphorylating its physiological substrate (d)GMP, catalyzes the second phosphorylation step in the conversion of anti-viral and anti-cancer nucleoside analogs to their corresponding active nucleoside analog triphosphates. Until now, a high-resolution structure of hGMPK is unavailable and thus, we studied free hGMPK by NMR and assigned the chemical shift resonances of backbone and side chain ^1H, ^13C, and ^15N nuclei as a first step towards the enzyme’s structural and mechanistic analysis with atomic resolution.
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Structural requirements for calmodulin binding to membrane-associated Guanylate Kinase homologs.
Protein Science, 2008Co-Authors: Ingo Paarmann, Arnon Lavie, Manfred KonradAbstract:Effector molecules such as calmodulin modulate the interactions of membrane-associated Guanylate Kinase homologs (MAGUKs) and other scaffolding proteins of the membrane cytoskeleton by binding to the Src homology 3 (SH3) domain, the Guanylate Kinase (GK) domain, or the connecting HOOK region of MAGUKs. Using surface plasmon resonance, we studied the interaction of members of all four MAGUK subfamilies—synapse-associated protein 97 (SAP97), calcium/calmodulin-dependent serine protein Kinase (CASK), membrane palmitoylated protein 2 (MPP2), and zona occludens (ZO) 1—and calmodulin to determine interaction affinities and localize the binding site. The SH3-GK domains of the proteins and derivatives thereof were expressed in E. coli and purified. In all four proteins, high-affinity calmodulin binding was identified. CASK was shown to contain a Ca2+-dependent calmodulin binding site within the HOOK region, overlapping with a protein 4.1 binding site. In ZO1, a Ca2+-dependent calmodulin binding site was detected within the GK domain. The equilibrium dissociation constants for MAGUK–calmodulin interaction were found to range from 50 nM to 180 nM. Sequence analyses suggest that binding sites for calmodulin have evolved independently in at least three subfamilies. For ZO1, pulldown of GST-calmodulin was shown to occur in a calcium-dependent manner; moreover, molecular modeling and sequence analyses predict conserved basic residues to be exposed on one side of a helix. Thus, calmodulin binding appears to be a common feature of MAGUKs, and Ca2+-activated calmodulin may serve as a general regulator to affect the interactions of MAGUKs and various components of the cytoskeleton.
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formation of complexes between ca2 calmodulin and the synapse associated protein sap97 requires the sh3 domain Guanylate Kinase domain connecting hook region
Journal of Biological Chemistry, 2002Co-Authors: Ingo Paarmann, Oliver Spangenberg, Arnon Lavie, Manfred KonradAbstract:Abstract Mammalian synapse-associated protein SAP97, a structural and functional homolog of DrosophilaDlg, is a membrane-associated Guanylate Kinase (MAGUK) that is present at pre- and postsynaptic sites as well as in epithelial cell-cell contact sites. It is a multidomain scaffolding protein that shares with other members of the MAGUK protein family a characteristic modular organization composed of three sequential protein interaction motifs known as PDZ domains, followed by an Src homology 3 (SH3) domain, and an enzymatically inactive Guanylate Kinase (GK)-like domain. Specific binding partners are known for each domain, and different modes of intramolecular interactions have been proposed that particularly involve the SH3 and GK domains and the so-called HOOK region located between these two domains. We identified the HOOK region as a specific site for calmodulin binding and studied the dynamics of complex formation of recombinant calmodulin and SAP97 by surface plasmon resonance spectroscopy. Binding of various SAP97 deletion constructs to immobilized calmodulin was strictly calcium-dependent. From the rate constants of association and dissociation we determined an equilibrium dissociation constantK d of 122 nm for the association of calcium-saturated calmodulin and a SAP97 fragment, which encompassed the entire SH3-HOOK-GK module. Comparative structure-based sequence analysis of calmodulin binding regions from various target proteins predicts variable affinities for the interaction of calmodulin with members of the MAGUK protein family. Our findings suggest that calmodulin could regulate the intramolecular interaction between the SH3, HOOK, and GK domains of SAP97.
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Structural Characterization of the Closed Conformation of Mouse Guanylate Kinase
Journal of Biological Chemistry, 2002Co-Authors: Nikolina Sekulic, Luybov Shuvalova, Oliver Spangenberg, Manfred Konrad, Arnon LavieAbstract:Abstract Guanylate Kinase (GMPK) is a nucleoside monophosphate Kinase that catalyzes the reversible phosphoryl transfer from ATP to GMP to yield ADP and GDP. In addition to phosphorylating GMP, antiviral prodrugs such as acyclovir, ganciclovir, and carbovir and anticancer prodrugs such as the thiopurines are dependent on GMPK for their activation. Hence, structural information on mammalian GMPK could play a role in the design of improved antiviral and antineoplastic agents. Here we present the structure of the mouse enzyme in an abortive complex with the nucleotides ADP and GMP, refined at 2.1 A resolution with a final crystallographic R factor of 0.19 (R free = 0.23). Guanylate Kinase is a member of the nucleoside monophosphate (NMP) Kinase family, a family of enzymes that despite having a low primary structure identity share a similar fold, which consists of three structurally distinct regions termed the CORE, LID, and NMP-binding regions. Previous studies on the yeast enzyme have shown that these parts move as rigid bodies upon substrate binding. It has been proposed that consecutive binding of substrates leads to “closing” of the active site bringing the NMP-binding and LID regions closer to each other and to the CORE region. Our structure, which is the first of any Guanylate Kinase with both substrates bound, supports this hypothesis. It also reveals the binding site of ATP and implicates arginines 44, 137, and 148 (in addition to the invariant P-loop lysine) as candidates for catalyzing the chemical step of the phosphoryl transfer.
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Structural basis for nucleotide-dependent regulation of membrane associated Guanylate Kinase-like domains
Journal of Biological Chemistry, 2001Co-Authors: Yuanhe Li, Ingo Paarmann, Oliver Spangenberg, Manfred Konrad, Arnon LavieAbstract:CASK is a member of the membrane-associated Guanylate Kinases (MAGUK) homologs, a family of proteins that scaffold protein complexes at particular regions of the plasma membrane by utilizing multiple protein-binding domains. The GK domain of MAGUKs, which shares high similarity in amino acid sequence with yeast Guanylate Kinase (yGMPK), is the least characterized MAGUK domain both in structure and function. In addition to its scaffolding function, the GK domain of hCASK has been shown to be involved in transcription regulation. Here we report the crystal structure of the GK domain of human CASK (hCASK-GK) at 1.3-A resolution. The structure rationalizes the inability of the GK domain to catalyze phosphoryl transfer and strongly supports its new function as a protein-binding module. Comparison of the hCASK-GK structure with the available crystal structures of yGMPK provides insight into possible conformational changes that occur in hCASK upon GMP binding. These conformational changes may act to regulate hCASK-GK function in a nucleotide-dependent manner.
Henry M Colecraft - One of the best experts on this subject based on the ideXlab platform.
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a cavβ sh3 Guanylate Kinase domain interaction regulates multiple properties of voltage gated ca2 channels
The Journal of General Physiology, 2005Co-Authors: Shoji X. Takahashi, Jayalakshmi Miriyala, Lai Hock Tay, David T. Yue, Henry M ColecraftAbstract:Auxiliary Ca2+ channel β subunits (CaVβ) regulate cellular Ca2+ signaling by trafficking pore-forming α1 subunits to the membrane and normalizing channel gating. These effects are mediated through a characteristic src homology 3/Guanylate Kinase (SH3–GK) structural module, a design feature shared in common with the membrane-associated Guanylate Kinase (MAGUK) family of scaffold proteins. However, the mechanisms by which the CaVβ SH3–GK module regulates multiple Ca2+ channel functions are not well understood. Here, using a split-domain approach, we investigated the role of the interrelationship between CaVβ SH3 and GK domains in defining channel properties. The studies build upon a previously identified split-domain pair that displays a trans SH3–GK interaction, and fully reconstitutes CaVβ effects on channel trafficking, activation gating, and increased open probability (Po). Here, by varying the precise locations used to separate SH3 and GK domains and monitoring subsequent SH3–GK interactions by fluorescence resonance energy transfer (FRET), we identified a particular split-domain pair that displayed a subtly altered configuration of the trans SH3–GK interaction. Remarkably, this pair discriminated between CaVβ trafficking and gating properties: α1C targeting to the membrane was fully reconstituted, whereas shifts in activation gating and increased Po functions were selectively lost. A more extreme case, in which the trans SH3–GK interaction was selectively ablated, yielded a split-domain pair that could reconstitute neither the trafficking nor gating-modulation functions, even though both moieties could independently engage their respective binding sites on the α1C (CaV1.2) subunit. The results reveal that CaVβ SH3 and GK domains function codependently to tune Ca2+ channel trafficking and gating properties, and suggest new paradigms for physiological and therapeutic regulation of Ca2+ channel activity.
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A CaVβ SH3/Guanylate Kinase domain interaction regulates multiple properties of voltage-gated Ca2+ channels
The Journal of general physiology, 2005Co-Authors: Shoji X. Takahashi, Jayalakshmi Miriyala, Lai Hock Tay, David T. Yue, Henry M ColecraftAbstract:Auxiliary Ca2+ channel β subunits (CaVβ) regulate cellular Ca2+ signaling by trafficking pore-forming α1 subunits to the membrane and normalizing channel gating. These effects are mediated through a characteristic src homology 3/Guanylate Kinase (SH3–GK) structural module, a design feature shared in common with the membrane-associated Guanylate Kinase (MAGUK) family of scaffold proteins. However, the mechanisms by which the CaVβ SH3–GK module regulates multiple Ca2+ channel functions are not well understood. Here, using a split-domain approach, we investigated the role of the interrelationship between CaVβ SH3 and GK domains in defining channel properties. The studies build upon a previously identified split-domain pair that displays a trans SH3–GK interaction, and fully reconstitutes CaVβ effects on channel trafficking, activation gating, and increased open probability (Po). Here, by varying the precise locations used to separate SH3 and GK domains and monitoring subsequent SH3–GK interactions by fluorescence resonance energy transfer (FRET), we identified a particular split-domain pair that displayed a subtly altered configuration of the trans SH3–GK interaction. Remarkably, this pair discriminated between CaVβ trafficking and gating properties: α1C targeting to the membrane was fully reconstituted, whereas shifts in activation gating and increased Po functions were selectively lost. A more extreme case, in which the trans SH3–GK interaction was selectively ablated, yielded a split-domain pair that could reconstitute neither the trafficking nor gating-modulation functions, even though both moieties could independently engage their respective binding sites on the α1C (CaV1.2) subunit. The results reveal that CaVβ SH3 and GK domains function codependently to tune Ca2+ channel trafficking and gating properties, and suggest new paradigms for physiological and therapeutic regulation of Ca2+ channel activity.
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Membrane-associated Guanylate Kinase-like properties of β-subunits required for modulation of voltage-dependent Ca2+ channels
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Shoji X. Takahashi, Jayalakshmi Miriyala, Henry M ColecraftAbstract:High-voltage-activated Ca2+ channels regulate diverse functions ranging from muscle contraction to synaptic transmission. Association between auxiliary β- and distinct pore-forming α1-subunits is obligatory for forming functional high-voltage-activated Ca2+ channels, yet the structural determinants underlying this interaction remain poorly understood. Recently, homology modeling of Ca2+-channel β1b-subunit identified src homology 3 (SH3) and Guanylate Kinase (GK) motifs in a tandem arrangement reminiscent of the membrane-associated Guanylate Kinase (MAGUK) class of scaffolding proteins. However, direct evidence for MAGUK-like properties and their functional implications in β-subunits is lacking. Here, we show a functional requirement for both SH3 and GK domains in β2a. Point mutations in either the putative β2a SH3 or GK domains severely blunted modulation of recombinant L-type channels, showing the importance of both motifs for a functional α1–β interaction. Coexpression of these functionally deficient β2a-SH3 and GK mutants rescued WT currents, demonstrating trans complementation similar to that observed in MAGUKs. Truncated “hemi-β2a” subunits, containing either the SH3 or GK domain, were ineffective on their own, but reconstituted WT currents when coexpressed. Moreover, the SH3 and GK domains were found to interact in vitro. These findings reveal MAGUK-like properties in β-subunits that are critical for α1-subunit modulation, revise current models of α1–β association, and predict new physiological dimensions of β-subunit function.
Margaret E. Black - One of the best experts on this subject based on the ideXlab platform.
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Mutations at serine 37 in mouse Guanylate Kinase confer resistance to 6-thioguanine.
Protein Engineering Design & Selection, 2009Co-Authors: Andressa Ardiani, Amanda Goyke, Margaret E. BlackAbstract:Guanylate Kinase (GMK) is an essential nucleoside monophosphate Kinase that catalyzes the phosphorylation of guanine-monophosphate (GMP) and dGMP to yield GDP and dGDP, respectively, important precursors for nucleotide synthesis. GMK is also responsible for the activation of 6-thioguanine (6-TG), a drug widely used as chemotherapeutic agent to treat leukemia. Several mechanisms of resistance to 6-TG have been reported but a subset of drug resistant cells cannot be explained by these mechanisms. We propose that mutations in GMK could result in drug resistance. Because cells require the presence of a functional GMK for viability, mutations that arise that lead to 6-TG resistance must retain activity toward GMP. We report three amino acid substitutions at serine 37 (S37) in mouse GMK that display activity toward GMP by conferring genetic complementation to a conditional GMK-deficient Escherichia coli and in enzyme assays. When 6-TG is included in complementation studies, cells expressing wild-type GMK are sensitive whereas all S37 mutants examined are able to effectively discriminate against 6-TG and display a drug resistance phenotype. Activity of the three S37 mutant enzymes toward clinically relevant concentrations of 6-TGMP is undetectable. Mutations in GMK, therefore, represent a previously undescribed mechanism for 6-TG resistance.
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A Guanylate Kinase/HSV-1 thymidine Kinase fusion protein enhances prodrug-mediated cell killing.
Gene therapy, 2006Co-Authors: Candice Willmon, Elizabeth A. Krabbenhoft, Margaret E. BlackAbstract:A Guanylate Kinase/HSV-1 thymidine Kinase fusion protein enhances prodrug-mediated cell killing
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a Guanylate Kinase hsv 1 thymidine Kinase fusion protein enhances prodrug mediated cell killing
Gene Therapy, 2006Co-Authors: Candice Willmon, Elizabeth Krabbenhoft, Margaret E. BlackAbstract:A Guanylate Kinase/HSV-1 thymidine Kinase fusion protein enhances prodrug-mediated cell killing
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A novel Escherichia coli strain allows functional analysis of Guanylate Kinase drug resistance and sensitivity.
Analytical biochemistry, 2003Co-Authors: Tiffany S. Stolworthy, Elizabeth A. Krabbenhoft, Margaret E. BlackAbstract:Abstract Guanylate Kinase is a critical enzyme in the biosynthesis of guanosine 5 ′ -triphosphate (GTP) and dGTP and is responsible for the phosphorylation of guanosine 5 ′ -monophosphate (GMP) and dGMP to guanosine 5 ′ -diphosphate (GDP) and dGDP, respectively. As with many nucleotide-metabolizing enzymes, Guanylate Kinase is involved in antimicrobial and antineoplastic drug activation. This is due to the structural similarities of such agents with nucleobases or nucleosides that are acted upon by endogenous enzymes. Despite the involvement of Guanylate Kinase in 6-thioguanine, mercaptopurine, and abasic guanosine analog (e.g., ganciclovir) activation, studies have only recently focused on the molecular basis of the structure to function relationship of a mammalian Guanylate Kinase. As a means to evaluate the details of amino acid side chain involvement in substrate interaction, we have constructed a conditional Guanylate-Kinase-deficient Escherichia coli strain that requires the presence of a functional, plasmid-borne Guanylate Kinase for growth under selective conditions. Positive genetic selection provides a rapid mechanism to identify not only functional Guanylate Kinase mutants but also those that result in drug resistance. This novel strain will be beneficial to assess the role of specific amino acids of Guanylate Kinase in structure, function, drug activation, and drug resistance.
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The mouse Guanylate Kinase double mutant E72Q/D103N is a functional adenylate Kinase.
Protein engineering, 2001Co-Authors: Tiffany S. Stolworthy, Margaret E. BlackAbstract:Guanylate Kinase catalyzes the phosphorylation of either GMP to GDP or dGMP to dGDP and is an important enzyme in nucleotide metabolic pathways. Because of its essential intracellular role, Guanylate Kinase is a target for a number of cancer chemotherapeutic agents such as 6-thioguanine and 8-azaguanine and is involved in antiviral drug activation. Guanylate Kinase shares a similarity in function and structure to other nucleoside monophosphate Kinases especially with that of the well-studied adenylate Kinase. Amino acid substitutions were made within the GMP binding site of mouse Guanylate Kinase to alter the polarity of the side chains that interact with GMP as a means of evaluating the role that these residues play on substrate interaction. One of these mutants, E72Q/D103N, was shown by functional complementation and enzyme assays to embody both Guanylate Kinase activity and a novel adenylate Kinase activity.
Laurence A Lasky - One of the best experts on this subject based on the ideXlab platform.
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interaction of the tumor suppressor pten mmac with a pdz domain of magi3 a novel membrane associated Guanylate Kinase
Journal of Biological Chemistry, 2000Co-Authors: Yan Wu, Susan D. Spencer, Richard P. Laura, Qimin Gu, Donald Dowbenko, Laurence A LaskyAbstract:Abstract PTEN/MMAC is a phosphatase that is mutated in multiple human tumors. PTEN/MMAC dephosphorylates 3-phosphorylated phosphatidylinositol phosphates that activate AKT/protein Kinase B (PKB) Kinase activity. AKT/PKB is implicated in the inhibition of apoptosis, and cell lines and tumors with mutated PTEN/MMAC show increased AKT/PKB Kinase activity and resistance to apoptosis. PTEN/MMAC contains a PDZ domain-binding site, and we show here that the phosphatase binds to a PDZ domain ofmembrane-associated Guanylate Kinase with inverted orientation (MAGI) 3, a novel inverted membrane-associated Guanylate Kinase that localizes to epithelial cell tight junctions. Importantly, MAGI3 and PTEN/MMAC cooperate to modulate the Kinase activity of AKT/PKB. These data suggest that MAGI3 allows for the juxtaposition of PTEN/MMAC to phospholipid signaling pathways involved with cell survival.
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Interaction of the Tumor Suppressor PTEN/MMAC with a PDZ Domain of MAGI3, a Novel Membrane-associated Guanylate Kinase
Journal of Biological Chemistry, 2000Co-Authors: Yan Wu, Susan D. Spencer, Richard P. Laura, Qimin Gu, Donald Dowbenko, Laurence A LaskyAbstract:Abstract PTEN/MMAC is a phosphatase that is mutated in multiple human tumors. PTEN/MMAC dephosphorylates 3-phosphorylated phosphatidylinositol phosphates that activate AKT/protein Kinase B (PKB) Kinase activity. AKT/PKB is implicated in the inhibition of apoptosis, and cell lines and tumors with mutated PTEN/MMAC show increased AKT/PKB Kinase activity and resistance to apoptosis. PTEN/MMAC contains a PDZ domain-binding site, and we show here that the phosphatase binds to a PDZ domain ofmembrane-associated Guanylate Kinase with inverted orientation (MAGI) 3, a novel inverted membrane-associated Guanylate Kinase that localizes to epithelial cell tight junctions. Importantly, MAGI3 and PTEN/MMAC cooperate to modulate the Kinase activity of AKT/PKB. These data suggest that MAGI3 allows for the juxtaposition of PTEN/MMAC to phospholipid signaling pathways involved with cell survival.