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Xiao H, Wang G, Zhao M, Shuai W, Ouyang L, Sun Q. Ras superfamily GTPase activating proteins in cancer: Potential therapeutic targets? Eur J Med Chem 2023; 248:115104. [PMID: 36641861 DOI: 10.1016/j.ejmech.2023.115104] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/06/2023] [Accepted: 01/07/2023] [Indexed: 01/11/2023]
Abstract
To search more therapeutic strategies for Ras-mutant tumors, regulators of the Ras superfamily involved in the GTP/GDP (guanosine triphosphate/guanosine diphosphate) cycle have been well concerned for their anti-tumor potentials. GTPase activating proteins (GAPs) provide the catalytic group necessary for the hydrolysis of GTPs, which accelerate the switch by cycling between GTP-bound active and GDP-bound inactive forms. Inactivated GAPs lose their function in activating GTPase, leading to the continuous activation of downstream signaling pathways, uncontrolled cell proliferation, and eventually carcinogenesis. A growing number of evidence has shown the close link between GAPs and human tumors, and as a result, GAPs are believed as potential anti-tumor targets. The present review mainly summarizes the critically important role of GAPs in human tumors by introducing the classification, function and regulatory mechanism. Moreover, we comprehensively describe the relationship between dysregulated GAPs and the certain type of tumor. Finally, the current status, research progress, and clinical value of GAPs as therapeutic targets are also discussed, as well as the challenges and future direction in the cancer therapy.
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Affiliation(s)
- Huan Xiao
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China
| | - Guan Wang
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China
| | - Min Zhao
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China
| | - Wen Shuai
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China
| | - Liang Ouyang
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China
| | - Qiu Sun
- State Key Laboratory of Biotherapy and Cancer Center, Innovation Center of Nursing Research, Nursing Key Laboratory of Sichuan Province, National Clinical Research Center for Geriatrics, West China Hospital, Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, 610041, China.
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2
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Chouinard FC, Davis L, Gilbert C, Bourgoin SG. Functional Role of AGAP2/PIKE-A in Fcγ Receptor-Mediated Phagocytosis. Cells 2022; 12:cells12010072. [PMID: 36611866 PMCID: PMC9818964 DOI: 10.3390/cells12010072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
In phagocytes, cytoskeletal and membrane remodeling is finely regulated at the phagocytic cup. Various smaFll G proteins, including those of the Arf family, control these dynamic processes. Human neutrophils express AGAP2, an Arf GTPase activating protein (ArfGAP) that regulates endosomal trafficking and focal adhesion remodeling. We first examined the impact of AGAP2 on phagocytosis in CHO cells stably expressing the FcγRIIA receptor (CHO-IIA). In unstimulated CHO-IIA cells, AGAP2 only partially co-localized with cytoskeletal elements and intracellular compartments. In CHO-IIA cells, AGAP2 transiently accumulated at actin-rich phagocytic cups and increased Fcγ receptor-mediated phagocytosis. Enhanced phagocytosis was not dependent on the N-terminal GTP-binding protein-like (GLD) domain of AGAP2. AGAP2 deleted of its GTPase-activating protein (GAP) domain was not recruited to phagocytic cups and did not enhance the engulfment of IgG-opsonized beads. However, the GAP-deficient [R618K]AGAP2 transiently localized at the phagocytic cups and enhanced phagocytosis. In PLB-985 cells differentiated towards a neutrophil-like phenotype, silencing of AGAP2 reduced phagocytosis of opsonized zymosan. In human neutrophils, opsonized zymosan or monosodium urate crystals induced AGAP2 phosphorylation. The data indicate that particulate agonists induce AGAP2 phosphorylation in neutrophils. This study highlights the role of AGAP2 and its GAP domain but not GAP activity in FcγR-dependent uptake of opsonized particles.
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Affiliation(s)
- François C. Chouinard
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
| | - Lynn Davis
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
| | - Caroline Gilbert
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
- Département de Microbiologie-Infectiologie et D’immunologie, Université Laval, Québec City, QC G1V 0A6, Canada
| | - Sylvain G. Bourgoin
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
- Département de Microbiologie-Infectiologie et D’immunologie, Université Laval, Québec City, QC G1V 0A6, Canada
- Centre ARThrite de L’université Laval, Québec City, QC G1V 4G2, Canada
- Correspondence:
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Stiegler AL, Boggon TJ. The pseudoGTPase group of pseudoenzymes. FEBS J 2020; 287:4232-4245. [PMID: 32893973 PMCID: PMC7544640 DOI: 10.1111/febs.15554] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/21/2020] [Accepted: 09/01/2020] [Indexed: 12/14/2022]
Abstract
Pseudoenzymes are emerging as significant mediators and regulators of signal transduction. These proteins maintain enzyme folds and topologies, but are disrupted in the conserved motifs required for enzymatic activity. Among the pseudoenzymes, the pseudoGTPase group of atypical GTPases has recently expanded and includes the Rnd and RGK groups, RhoH and the RhoBTB proteins, mitochondrial RhoGTPase and centaurin-γ groups, CENP-M, dynein LIC, Entamoeba histolytica RabX3, leucine-rich repeat kinase 2, and the p190RhoGAP proteins. The wide range of cellular functions associated with pseudoGTPases includes cell migration and adhesion, membrane trafficking and cargo transport, mitosis, mitochondrial activity, transcriptional control, and autophagy, placing the group in an expanding portfolio of signaling pathways. In this review, we examine how the pseudoGTPases differ from canonical GTPases and consider their mechanistic and functional roles in signal transduction. We review the amino acid differences between the pseudoGTPases and discuss how these proteins can be classified based on their ability to bind nucleotide and their enzymatic activity. We discuss the molecular and structural consequences of amino acid divergence from canonical GTPases and use comparison with the well-studied pseudokinases to illustrate the classifications. PseudoGTPases are fast becoming recognized as important mechanistic components in a range of cellular roles, and we provide a concise discussion of the currently identified members of this group. ENZYMES: small GTPases; EC number: EC 3.6.5.2.
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Affiliation(s)
- Amy L. Stiegler
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
| | - Titus J. Boggon
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
- Departments of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
- Yale Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
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4
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AGAP1 regulates subcellular localization of FilGAP and control cancer cell invasion. Biochem Biophys Res Commun 2020; 522:676-683. [DOI: 10.1016/j.bbrc.2019.11.147] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 11/22/2019] [Indexed: 12/12/2022]
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Parker SS, Krantz J, Kwak EA, Barker NK, Deer CG, Lee NY, Mouneimne G, Langlais PR. Insulin Induces Microtubule Stabilization and Regulates the Microtubule Plus-end Tracking Protein Network in Adipocytes. Mol Cell Proteomics 2019; 18:1363-1381. [PMID: 31018989 PMCID: PMC6601206 DOI: 10.1074/mcp.ra119.001450] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Indexed: 12/21/2022] Open
Abstract
Insulin-stimulated glucose uptake is known to involve microtubules, although the function of microtubules and the microtubule-regulating proteins involved in insulin action are poorly understood. CLASP2, a plus-end tracking microtubule-associated protein (+TIP) that controls microtubule dynamics, was recently implicated as the first +TIP associated with insulin-regulated glucose uptake. Here, using protein-specific targeted quantitative phosphoproteomics within 3T3-L1 adipocytes, we discovered that insulin regulates phosphorylation of the CLASP2 network members G2L1, MARK2, CLIP2, AGAP3, and CKAP5 as well as EB1, revealing the existence of a previously unknown microtubule-associated protein system that responds to insulin. To further investigate, G2L1 interactome studies within 3T3-L1 adipocytes revealed that G2L1 coimmunoprecipitates CLASP2 and CLIP2 as well as the master integrators of +TIP assembly, the end binding (EB) proteins. Live-cell total internal reflection fluorescence microscopy in adipocytes revealed G2L1 and CLASP2 colocalize on microtubule plus-ends. We found that although insulin increases the number of CLASP2-containing plus-ends, insulin treatment simultaneously decreases CLASP2-containing plus-end velocity. In addition, we discovered that insulin stimulates redistribution of CLASP2 and G2L1 from exclusive plus-end tracking to "trailing" behind the growing tip of the microtubule. Insulin treatment increases α-tubulin Lysine 40 acetylation, a mechanism that was observed to be regulated by a counterbalance between GSK3 and mTOR, and led to microtubule stabilization. Our studies introduce insulin-stimulated microtubule stabilization and plus-end trailing of +TIPs as new modes of insulin action and reveal the likelihood that a network of microtubule-associated proteins synergize to coordinate insulin-regulated microtubule dynamics.
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Affiliation(s)
- Sara S Parker
- From the ‡Department of Cellular & Molecular Medicine
| | - James Krantz
- §Department of Medicine, Division of Endocrinology
| | | | | | - Chris G Deer
- University of Arizona Research Computing, University of Arizona, Tucson, Arizona 85721
| | - Nam Y Lee
- ¶Department of Pharmacology,; ‖Department of Chemistry & Biochemistry, University of Arizona College of Medicine, Tucson, Arizona 85721
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Pacault M, Nizon M, Pichon O, Vincent M, Le Caignec C, Isidor B. A de novo 2q37.2 deletion encompassing AGAP1 and SH3BP4 in a patient with autism and intellectual disability. Eur J Med Genet 2018; 62:103586. [PMID: 30472483 DOI: 10.1016/j.ejmg.2018.11.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 10/19/2018] [Accepted: 11/22/2018] [Indexed: 11/27/2022]
Abstract
Autism spectrum disorders are complex neurodevelopmental syndromes characterized by phenotypic and genetic heterogeneity. Further identification of causal genes may help in better understanding the underlying mechanisms of the disorder, thus improving the patients' management. To date, abnormal synaptogenesis is thought to be one of the major underlying causes of autism spectrum disorders. Here, using oligoarray-based comparative genomic hybridization, we identified a de novo deletion at 2q37.2 locus spanning 1 Mb and encompassing AGAP1 and SH3BP4, in a boy with autism and intellectual disability. Both genes have been described as being involved in endosomal trafficking, and AGAP1 in particular has been shown to be expressed in the developing brain and to play a role in dendritic spine formation and synapse function, making it a potential causative gene to our patient's phenotype.
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Affiliation(s)
| | - Mathilde Nizon
- CHU Nantes, Service de Génétique Médicale, Nantes, France
| | - Olivier Pichon
- CHU Nantes, Service de Génétique Médicale, Nantes, France
| | - Marie Vincent
- CHU Nantes, Service de Génétique Médicale, Nantes, France
| | - Cédric Le Caignec
- CHU Nantes, Service de Génétique Médicale, Nantes, France; INSERM, UMR 1238, Bone Sarcoma and Remodeling of Calcified Tissue, Nantes, France
| | - Bertrand Isidor
- CHU Nantes, Service de Génétique Médicale, Nantes, France; INSERM, UMR 1238, Bone Sarcoma and Remodeling of Calcified Tissue, Nantes, France
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Kruse R, Krantz J, Barker N, Coletta RL, Rafikov R, Luo M, Højlund K, Mandarino LJ, Langlais PR. Characterization of the CLASP2 Protein Interaction Network Identifies SOGA1 as a Microtubule-Associated Protein. Mol Cell Proteomics 2017; 16:1718-1735. [PMID: 28550165 DOI: 10.1074/mcp.ra117.000011] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Indexed: 12/26/2022] Open
Abstract
CLASP2 is a microtubule-associated protein that undergoes insulin-stimulated phosphorylation and co-localization with reorganized actin and GLUT4 at the plasma membrane. To gain insight to the role of CLASP2 in this system, we developed and successfully executed a streamlined interactome approach and built a CLASP2 protein network in 3T3-L1 adipocytes. Using two different commercially available antibodies for CLASP2 and an antibody for epitope-tagged, overexpressed CLASP2, we performed multiple affinity purification coupled with mass spectrometry (AP-MS) experiments in combination with label-free quantitative proteomics and analyzed the data with the bioinformatics tool Significance Analysis of Interactome (SAINT). We discovered that CLASP2 coimmunoprecipitates (co-IPs) the novel protein SOGA1, the microtubule-associated protein kinase MARK2, and the microtubule/actin-regulating protein G2L1. The GTPase-activating proteins AGAP1 and AGAP3 were also enriched in the CLASP2 interactome, although subsequent AGAP3 and CLIP2 interactome analysis suggests a preference of AGAP3 for CLIP2. Follow-up MARK2 interactome analysis confirmed reciprocal co-IP of CLASP2 and revealed MARK2 can co-IP SOGA1, glycogen synthase, and glycogenin. Investigating the SOGA1 interactome confirmed SOGA1 can reciprocal co-IP both CLASP2 and MARK2 as well as glycogen synthase and glycogenin. SOGA1 was confirmed to colocalize with CLASP2 and with tubulin, which identifies SOGA1 as a new microtubule-associated protein. These results introduce the metabolic function of these proposed novel protein networks and their relationship with microtubules as new fields of cytoskeleton-associated protein biology.
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Affiliation(s)
- Rikke Kruse
- From the ‡The Section of Molecular Diabetes & Metabolism, Department of Clinical Research and Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense, Denmark.,§Department of Endocrinology, Odense University Hospital, DK-5000 Odense, Denmark
| | - James Krantz
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721
| | - Natalie Barker
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721
| | - Richard L Coletta
- ‖School of Life Sciences, Arizona State University, Tempe, Arizona 85787
| | - Ruslan Rafikov
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721
| | - Moulun Luo
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721
| | - Kurt Højlund
- From the ‡The Section of Molecular Diabetes & Metabolism, Department of Clinical Research and Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense, Denmark.,§Department of Endocrinology, Odense University Hospital, DK-5000 Odense, Denmark
| | - Lawrence J Mandarino
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721
| | - Paul R Langlais
- ¶Department of Medicine, Division of Endocrinology, University of Arizona College of Medicine, Tucson, Arizona 85721;
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Luo R, Chen PW, Wagenbach M, Jian X, Jenkins L, Wordeman L, Randazzo PA. Direct Functional Interaction of the Kinesin-13 Family Member Kinesin-like Protein 2A (Kif2A) and Arf GAP with GTP-binding Protein-like, Ankyrin Repeats and PH Domains1 (AGAP1). J Biol Chem 2016; 291:21350-21362. [PMID: 27531749 DOI: 10.1074/jbc.m116.732479] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/09/2016] [Indexed: 11/06/2022] Open
Abstract
The molecular basis for control of the cytoskeleton by the Arf GTPase-activating protein AGAP1 has not been characterized. AGAP1 is composed of G-protein-like (GLD), pleckstrin homology (PH), Arf GAP, and ankyrin repeat domains. Kif2A was identified in screens for proteins that bind to AGAP1. The GLD and PH domains of AGAP1 bound the motor domain of Kif2A. Kif2A increased GAP activity of AGAP1, and a protein composed of the GLD and PH domains of AGAP1 increased ATPase activity of Kif2A. Knockdown (KD) of Kif2A or AGAP1 slowed cell migration and accelerated cell spreading. The effect of Kif2A KD on spreading could be rescued by expression of Kif2A-GFP or FLAG-AGAP1, but not by Kif2C-GFP. The effect of AGAP1 KD could be rescued by FLAG-AGAP1, but not by an AGAP1 mutant that did not bind Kif2A efficiently, ArfGAP1-HA or Kif2A-GFP. Taken together, the results support the hypothesis that the Kif2A·AGAP1 complex contributes to control of cytoskeleton remodeling involved in cell movement.
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Affiliation(s)
- Ruibai Luo
- From the Laboratory of Cellular and Molecular Biology and
| | - Pei-Wen Chen
- From the Laboratory of Cellular and Molecular Biology and.,the Department of Biology, Grinnell College, Grinnell, Iowa 50112, and
| | - Michael Wagenbach
- the Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195
| | - Xiaoying Jian
- From the Laboratory of Cellular and Molecular Biology and
| | - Lisa Jenkins
- Laboratory of Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Linda Wordeman
- the Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195
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Roy NS, Yohe ME, Randazzo PA, Gruschus JM. Allosteric properties of PH domains in Arf regulatory proteins. CELLULAR LOGISTICS 2016; 6:e1181700. [PMID: 27294009 DOI: 10.1080/21592799.2016.1181700] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 10/21/2022]
Abstract
Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains.
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Affiliation(s)
- Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Marielle E Yohe
- Genetics Branch, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - James M Gruschus
- Laboratory of Structural Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health , Bethesda, MD, USA
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Abstract
During NMDA receptor-mediated long-term potentiation (LTP), synapses are strengthened by trafficking AMPA receptors to the synapse through a calcium-dependent kinase cascade following activation of NMDA receptors. This process results in a long-lasting increase in synaptic strength that is thought to be a cellular mechanism for learning and memory. Over the past 20 years, many signaling pathways have been shown to be involved in the induction and maintenance of LTP including the MAPK cascade. However, the crucial link between NMDA receptors and the signaling cascades involved in AMPA receptor trafficking during LTP remains elusive. In this study, we aimed to identify and characterize NMDA receptor signaling proteins that link NMDA receptor activation to downstream signaling pathways that lead to trafficking of AMPA receptors. We have identified a novel NMDA receptor interacting signaling protein, AGAP3. AGAP3 contains multiple signaling domains, a GTPase-like domain, a pleckstrin homology domain, and an ArfGAP domain, and exists as a component of the NMDA receptor complex. In addition, we found that AGAP3 regulates NMDA receptor-mediated Ras/ERK and Arf6 signaling pathways during chemically induced LTP in rat primary neuronal cultures. Finally, knocking down AGAP3 expression leads to occlusion of AMPA receptor trafficking during chemically induced LTP. Together, AGAP3 is an essential signaling component of the NMDA receptor complex that links NMDA receptor activation to AMPA receptor trafficking.
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The Arf GAP AGAP2 interacts with β-arrestin2 and regulates β2-adrenergic receptor recycling and ERK activation. Biochem J 2013; 452:411-21. [PMID: 23527545 DOI: 10.1042/bj20121004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
AGAP2 [Arf (ADP-ribosylation factor) GAP (GTPase-activating protein) with GTP-binding-protein-like, ankyrin repeat and PH (pleckstrin homology) domains] is a multidomain Arf GAP that was shown to promote the fast recycling of transferrin receptors. In the present study we tested the hypothesis that AGAP2 regulates the trafficking of β2-adrenergic receptors. We found that AGAP2 formed a complex with β-arrestin1 and β-arrestin2, proteins that are known to regulate β2-adrenergic receptor signalling and trafficking. AGAP2 co-localized with β-arrestin2 on the plasma membrane, and knockdown of AGAP2 expression reduced plasma membrane association of β-arrestin2 upon β2-adrenergic receptor activation. AGAP2 also co-localized with internalized β2-adrenergic receptors on endosomes, and overexpression of AGAP2 slowed accumulation of β2-adrenergic receptor in the perinuclear recycling endosomes. In contrast, knockdown of AGAP2 expression prevented the recycling of the β2-adrenergic receptor back to the plasma membrane. In addition, AGAP2 formed a complex with endogenous ERK (extracellular-signal-regulated kinase) and overexpression of AGAP2 potentiated ERK phosphorylation induced by β2-adrenergic receptors. Taken together, these results support the hypothesis that AGAP2 plays a role in the signalling and recycling of β2-adrenergic receptors.
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Gorynia S, Lorenz TC, Costaguta G, Daboussi L, Cascio D, Payne GS. Yeast Irc6p is a novel type of conserved clathrin coat accessory factor related to small G proteins. Mol Biol Cell 2012; 23:4416-29. [PMID: 22993212 PMCID: PMC3496615 DOI: 10.1091/mbc.e12-07-0507] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Yeast Irc6p is a novel type of conserved clathrin coat accessory protein that functions in clathrin-mediated traffic between the trans-Golgi network and endosomes, linking clathrin adaptor complex AP-1 and the Rab GTPase Ypt31p. Irc6p and the mammalian homologue p34 are founding members of a new G protein–like family. Clathrin coat accessory proteins play key roles in transport mediated by clathrin-coated vesicles. Yeast Irc6p and the related mammalian p34 are putative clathrin accessory proteins that interact with clathrin adaptor complexes. We present evidence that Irc6p functions in clathrin-mediated traffic between the trans-Golgi network and endosomes, linking clathrin adaptor complex AP-1 and the Rab GTPase Ypt31p. The crystal structure of the Irc6p N-terminal domain revealed a G-protein fold most related to small G proteins of the Rab and Arf families. However, Irc6p lacks G-protein signature motifs and high-affinity GTP binding. Also, mutant Irc6p lacking candidate GTP-binding residues retained function. Mammalian p34 rescued growth defects in irc6∆ cells, indicating functional conservation, and modeling predicted a similar N-terminal fold in p34. Irc6p and p34 also contain functionally conserved C-terminal regions. Irc6p/p34-related proteins with the same two-part architecture are encoded in genomes of species as diverse as plants and humans. Together these results define Irc6p/p34 as a novel type of conserved clathrin accessory protein and founding members of a new G protein–like family.
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Affiliation(s)
- Sabine Gorynia
- Department of Biological Chemistry, School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
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13
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Northup JK, Jian X, Randazzo PA. Nucleotide exchange factors: Kinetic analyses and the rationale for studying kinetics of GEFs. CELLULAR LOGISTICS 2012. [PMID: 23181196 PMCID: PMC3498072 DOI: 10.4161/cl.21627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Exchange factors are enzymes that catalyze the exchange of GTP for GDP on guanine nucleotide binding proteins. Progress in understanding the molecular basis of action and the cellular functions of these enzymes has largely come from structural determinations (e.g., crystal structures) and studying effects on cells when expression levels of the exchange factors are perturbed or mutated exchange factors are expressed. Proportionally little effort has been expended on studying the kinetics of exchange; however, reaction rates are central to understanding enzymes. Here, we discuss the importance of kinetic analysis of exchange factors for guanine nucleotide binding proteins, with a focus on ADP-ribosylation factor (Arf) and heterotrimeric G proteins, for providing unique insights into molecular mechanisms and regulation as well as how kinetic analyses are used to complement other approaches.
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Affiliation(s)
- John K Northup
- Laboratory of Cellular Biology; National Institute of Deafness and Other Communication Disorders; Rockville, MD USA
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