1
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Anjum R, Clarke VRJ, Nagasawa Y, Murakoshi H, Paradis S. Rem2 interacts with CaMKII at synapses and restricts long-term potentiation in hippocampus. PLoS One 2024; 19:e0301063. [PMID: 38995900 PMCID: PMC11244776 DOI: 10.1371/journal.pone.0301063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Accepted: 06/11/2024] [Indexed: 07/14/2024] Open
Abstract
Synaptic plasticity, the process whereby neuronal connections are either strengthened or weakened in response to stereotyped forms of stimulation, is widely believed to represent the molecular mechanism that underlies learning and memory. The holoenzyme calcium/calmodulin-dependent protein kinase II (CaMKII) plays a well-established and critical role in the induction of a variety of forms of synaptic plasticity such as long-term potentiation (LTP), long-term depression (LTD) and depotentiation. Previously, we identified the GTPase Rem2 as a potent, endogenous inhibitor of CaMKII. Here, we report that knock out of Rem2 enhances LTP at the Schaffer collateral to CA1 synapse in hippocampus, consistent with an inhibitory action of Rem2 on CaMKII in vivo. Further, re-expression of WT Rem2 rescues the enhanced LTP observed in slices obtained from Rem2 conditional knock out (cKO) mice, while expression of a mutant Rem2 construct that is unable to inhibit CaMKII in vitro fails to rescue increased LTP. In addition, we demonstrate that CaMKII and Rem2 interact in dendritic spines using a 2pFLIM-FRET approach. Taken together, our data lead us to propose that Rem2 serves as a brake on synaptic potentiation via inhibition of CaMKII activity. Further, the enhanced LTP phenotype we observe in Rem2 cKO slices reveals a previously unknown role for Rem2 in the negative regulation of CaMKII function.
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Affiliation(s)
- Rabia Anjum
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts, United States of America
| | - Vernon R. J. Clarke
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Yutaro Nagasawa
- Department of Physiological Sciences, The Graduate University for Advanced Studies; Hayama, Kanagawa, Japan
- Supportive Center for Brain Research, National Institute for Physiological Sciences; Okazaki, Aichi, Japan
| | - Hideji Murakoshi
- Department of Physiological Sciences, The Graduate University for Advanced Studies; Hayama, Kanagawa, Japan
- Supportive Center for Brain Research, National Institute for Physiological Sciences; Okazaki, Aichi, Japan
| | - Suzanne Paradis
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts, United States of America
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2
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Anjum R, Clarke VRJ, Nagasawa Y, Murakoshi H, Paradis S. Rem2 interacts with CaMKII at synapses and restricts long-term potentiation in hippocampus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.11.584540. [PMID: 38558974 PMCID: PMC10979978 DOI: 10.1101/2024.03.11.584540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Synaptic plasticity, the process whereby neuronal connections are either strengthened or weakened in response to stereotyped forms of stimulation, is widely believed to represent the molecular mechanism that underlies learning and memory. The holoenzyme CaMKII plays a well-established and critical role in the induction of a variety of forms of synaptic plasticity such as long-term potentiation (LTP), long-term depression (LTD) and depotentiation. Previously, we identified the GTPase Rem2 as a potent, endogenous inhibitor of CaMKII. Here, we report that knock out of Rem2 enhances LTP at the Schaffer collateral to CA1 synapse in hippocampus, consistent with an inhibitory action of Rem2 on CaMKII in vivo. Further, re-expression of WT Rem2 rescues the enhanced LTP observed in slices obtained from Rem2 conditional knock out (cKO) mice, while expression of a mutant Rem2 construct that is unable to inhibit CaMKII in vitro fails to rescue increased LTP. In addition, we demonstrate that CaMKII and Rem2 interact in dendritic spines using a 2pFLIM-FRET approach. Taken together, our data lead us to propose that Rem2 serves as a brake on runaway synaptic potentiation via inhibition of CaMKII activity. Further, the enhanced LTP phenotype we observe in Rem2 cKO slices reveals a previously unknown role for Rem2 in the negative regulation of CaMKII function.
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Affiliation(s)
- Rabia Anjum
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, United States of America
| | - Vernon R J Clarke
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Yutaro Nagasawa
- Department of Physiological Sciences, The Graduate University for Advanced Studies; Hayama, Kanagawa 240-0193, Japan
- Supportive Center for Brain Research, National Institute for Physiological Sciences; Okazaki, Aichi 444-8585, Japan
| | - Hideji Murakoshi
- Department of Physiological Sciences, The Graduate University for Advanced Studies; Hayama, Kanagawa 240-0193, Japan
- Supportive Center for Brain Research, National Institute for Physiological Sciences; Okazaki, Aichi 444-8585, Japan
| | - Suzanne Paradis
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, United States of America
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3
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Bao HY, Wang W, Sun HB, Chen JZ. Binding modes of GDP, GTP and GNP to NRAS deciphered by using Gaussian accelerated molecular dynamics simulations. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2023; 34:65-89. [PMID: 36762439 DOI: 10.1080/1062936x.2023.2165542] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 12/31/2022] [Indexed: 06/18/2023]
Abstract
Probing binding modes of GDP, GTP and GNP to NRAS are of significance for understanding the regulation mechanism on the activity of RAS proteins. Four separate Gaussian accelerated molecular dynamics (GaMD) simulations were performed on the apo, GDP-, GTP- and GNP-bound NRAS. Dynamics analyses suggest that binding of three ligands highly affects conformational states of the switch domains from NRAS, which disturbs binding of NRAS to its effectors. The analyses of free energy landscapes (FELs) indicate that binding of GDP, GTP and GNP induces more energetic states of NRAS compared to the apo NRAS but the presence of GNP makes the switch domains more ordered than binding of GDP and GNP. The information of interaction networks of ligands with NRAS reveals that the π-π interaction of residue F28 and the salt bridge interactions of K16 and D119 with ligands stabilize binding of GDP, GTP and GNP to NRAS. Meanwhile magnesium ion plays a bridge role in interactions of ligands with NRAS, which is favourable for associations of GDP, GTP and GNP with NRAS. This work is expected to provide useful information for deeply understanding the function and activity of NRAS.
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Affiliation(s)
- H Y Bao
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - W Wang
- School of Science, Shandong Jiaotong University, Jinan, China
| | - H B Sun
- School of Science, Shandong Jiaotong University, Jinan, China
| | - J Z Chen
- School of Science, Shandong Jiaotong University, Jinan, China
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4
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Langousis G, Cavadini S, Boegholm N, Lorentzen E, Kempf G, Matthias P. Structure of the ciliogenesis-associated CPLANE complex. SCIENCE ADVANCES 2022; 8:eabn0832. [PMID: 35427153 PMCID: PMC9012472 DOI: 10.1126/sciadv.abn0832] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/25/2022] [Indexed: 06/14/2023]
Abstract
Dysfunctional cilia cause pleiotropic human diseases termed ciliopathies. These hereditary maladies are often caused by defects in cilia assembly, a complex event that is regulated by the ciliogenesis and planar polarity effector (CPLANE) proteins Wdpcp, Inturned, and Fuzzy. CPLANE proteins are essential for building the cilium and are mutated in multiple ciliopathies, yet their structure and molecular functions remain elusive. Here, we show that mammalian CPLANE proteins comprise a bona fide complex and report the near-atomic resolution structures of the human Wdpcp-Inturned-Fuzzy complex and of the mouse Wdpcp-Inturned-Fuzzy complex bound to the small guanosine triphosphatase Rsg1. Notably, the crescent-shaped CPLANE complex binds phospholipids such as phosphatidylinositol 3-phosphate via multiple modules and a CPLANE ciliopathy mutant exhibits aberrant lipid binding. Our study provides critical structural and functional insights into an enigmatic ciliogenesis-associated complex as well as unexpected molecular rationales for ciliopathies.
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Affiliation(s)
- Gerasimos Langousis
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Simone Cavadini
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Niels Boegholm
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
| | - Esben Lorentzen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
| | - Georg Kempf
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Patrick Matthias
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
- Faculty of Sciences, University of Basel, 4031 Basel, Switzerland
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5
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Functional diversity in the RAS subfamily of small GTPases. Biochem Soc Trans 2022; 50:921-933. [PMID: 35356965 DOI: 10.1042/bst20211166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/15/2022] [Accepted: 03/21/2022] [Indexed: 12/12/2022]
Abstract
RAS small GTPases regulate important signalling pathways and are notorious drivers of cancer development and progression. While most research to date has focused on understanding and addressing the oncogenic potential of three RAS oncogenes: HRAS, KRAS, and NRAS; the full RAS subfamily is composed of 35 related GTPases with diverse cellular functions. Most remain deeply understudied despite strong evolutionary conservation. Here, we highlight a group of 17 poorly characterized RAS GTPases that are frequently down-regulated in cancer and evidence suggests may function not as oncogenes, but as tumour suppressors. These GTPases remain largely enigmatic in terms of their cellular function, regulation, and interaction with effector proteins. They cluster within two families we designate as 'distal-RAS' (D-RAS; comprised of DIRAS, RASD, and RASL10) and 'CaaX-Less RAS' (CL-RAS; comprised of RGK, NKIRAS, RERG, and RASL11/12 GTPases). Evidence of a tumour suppressive role for many of these GTPases supports the premise that RAS subfamily proteins may collectively regulate cellular proliferation.
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6
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Reconstitution of β-adrenergic regulation of Ca V1.2: Rad-dependent and Rad-independent protein kinase A mechanisms. Proc Natl Acad Sci U S A 2021; 118:2100021118. [PMID: 34001616 DOI: 10.1073/pnas.2100021118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
L-type voltage-gated CaV1.2 channels crucially regulate cardiac muscle contraction. Activation of β-adrenergic receptors (β-AR) augments contraction via protein kinase A (PKA)-induced increase of calcium influx through CaV1.2 channels. To date, the full β-AR cascade has never been heterologously reconstituted. A recent study identified Rad, a CaV1.2 inhibitory protein, as essential for PKA regulation of CaV1.2. We corroborated this finding and reconstituted the complete pathway with agonist activation of β1-AR or β2-AR in Xenopus oocytes. We found, and distinguished between, two distinct pathways of PKA modulation of CaV1.2: Rad dependent (∼80% of total) and Rad independent. The reconstituted system reproduces the known features of β-AR regulation in cardiomyocytes and reveals several aspects: the differential regulation of posttranslationally modified CaV1.2 variants and the distinct features of β1-AR versus β2-AR activity. This system allows for the addressing of central unresolved issues in the β-AR-CaV1.2 cascade and will facilitate the development of therapies for catecholamine-induced cardiac pathologies.
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7
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Dhanaraman T, Singh S, Killoran RC, Singh A, Xu X, Shifman JM, Smith MJ. RASSF effectors couple diverse RAS subfamily GTPases to the Hippo pathway. Sci Signal 2020; 13:13/653/eabb4778. [PMID: 33051258 DOI: 10.1126/scisignal.abb4778] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Small guanosine triphosphatases (GTPases) of the RAS superfamily signal by directly binding to multiple downstream effector proteins. Effectors are defined by a folded RAS-association (RA) domain that binds exclusively to GTP-loaded (activated) RAS, but the binding specificities of most RA domains toward more than 160 RAS superfamily GTPases have not been characterized. Ten RA domain family (RASSF) proteins comprise the largest group of related effectors and are proposed to couple RAS to the proapoptotic Hippo pathway. Here, we showed that RASSF1-6 formed complexes with the Hippo kinase ortholog MST1, whereas RASSF7-10 formed oligomers with the p53-regulating effectors ASPP1 and ASPP2. Moreover, only RASSF5 bound directly to activated HRAS and KRAS, and RASSFs did not augment apoptotic induction downstream of RAS oncoproteins. Structural modeling revealed that expansion of the RASSF effector family in vertebrates included amino acid substitutions to key residues that direct GTPase-binding specificity. We demonstrated that the tumor suppressor RASSF1A formed complexes with the RAS-related GTPases GEM, REM1, REM2, and the enigmatic RASL12. Furthermore, interactions between RASSFs and RAS GTPases blocked YAP1 nuclear localization. Thus, these simple scaffolds link the activation of diverse RAS family small G proteins to Hippo or p53 regulation.
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Affiliation(s)
- Thillaivillalan Dhanaraman
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Swati Singh
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Ryan C Killoran
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Anamika Singh
- Hebrew University of Jerusalem, Department of Biological Chemistry, Jerusalem 9190401, Israel
| | - Xingjian Xu
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Julia M Shifman
- Hebrew University of Jerusalem, Department of Biological Chemistry, Jerusalem 9190401, Israel
| | - Matthew J Smith
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec H3T 1J4, Canada. .,Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, Québec H3T 1J4, Canada
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8
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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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9
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Law ECY, Leung DTM, Tam FCH, Cheung KKT, Cheng NHY, Lim PL. IgM Antibodies Can Access Cryptic Antigens Denied to IgG: Hypothesis on Novel Binding Mechanism. Front Immunol 2019; 10:1820. [PMID: 31428101 PMCID: PMC6688401 DOI: 10.3389/fimmu.2019.01820] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/18/2019] [Indexed: 11/13/2022] Open
Abstract
Antibodies are well-known protein mediators of immunity. IgM is the primordial member and the neglected sibling of the later-evolved and more proficient IgG in regard to their therapeutic and diagnostic use. Serendipitously, however, we found a paradox: While murine IgM antibodies specific for guanosine triphosphate (GTP) were able to recognize native guanylyl antigens found in primate or rat muscle tissues by immunofluorescence assays (which mimicked the auto-antibodies from autoimmune patients to skeletal or smooth muscle), the murine and human IgG counterparts failed. The results were replicated in cell-free direct binding assays using small latex microspheres decorated densely with GTP. The IgG antibodies could bind, however, if GTP was presented more spaciously on larger particles or as a univalent hapten. Accordingly, oligomerization of GTP (30-mer) destroyed the binding of the IgG antibodies but enhanced that of the IgMs in inhibition ELISA. We reason that, contrary to current belief, IgM does not bind in a lock-and-key manner like IgG. We hypothesize that whereas the intact and rigid antigen-binding site of IgG hinders the antibody from docking with antigens that are obstructed, in IgM, the two component polypeptides of the antigen-binding site can dissociate from each other and navigate individually through obstacles like the ancestral single-polypeptide antibodies found in sharks and camelids, both components eventually re-grouping around the antigen. We further speculate that polyreactive IgMs, which enigmatically bind to more than one type of antigen, use the same modus operandi. These findings call for a re-look at the clinical potential of IgM antibodies particularly in specific areas of cancer therapy, tissue pathology and vaccine design, where IgG antibodies have failed due to target inaccessibility.
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Affiliation(s)
- Eric Chun Yiu Law
- Clinical Immunology Unit, The Chinese University of Hong Kong, Hong Kong, China
| | | | - Frankie Chi Hang Tam
- Clinical Immunology Unit, The Chinese University of Hong Kong, Hong Kong, China.,IgGENE, FoTan, Hong Kong, China
| | | | - Naomi Hua Yin Cheng
- Clinical Immunology Unit, The Chinese University of Hong Kong, Hong Kong, China
| | - Pak Leong Lim
- Clinical Immunology Unit, The Chinese University of Hong Kong, Hong Kong, China.,IgGENE, FoTan, Hong Kong, China
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10
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Xu Q, Wang Y, Zhu J, Zhao Y, Lin Y. Molecular characterization of GTP binding protein overexpressed in skeletal muscle (GEM) and its role in promoting adipogenesis in goat intramuscular preadipocytes. Anim Biotechnol 2018; 31:17-24. [PMID: 30570352 DOI: 10.1080/10495398.2018.1523796] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
GTP binding protein overexpressed in skeletal muscle (GEM) is an important gene with many functions, such as regulating the rearrangement of cytoskeleton and the activity of voltage-dependent calcium channel, and GEM was regarded as a candidate gene for obesity. However, little investigation has been carried out to explore whether GEM affected the intramuscular fat (IMF) deposition of goat. To explore the role of GEM gene in goat, this gene was cloned and its tissue and temporal expression profile were detected. Effect of GEM on adipogenesis was examined by losing function of GEM in vitro. Thereafter, several lipid metabolism-related genes were examined, including CCAAT/enhancing-binding protein α (C/EBPα), CCAAT/enhancing-binding protein β (C/EBPβ), lipoprotein lipase (LPL), preadipocyte factor 1 (Pref-1), peroxisome proliferator activated receptor γ (PPARγ) and sterol regulatory element binding protein 1 (SREBP1). We found that the goat GEM gene consisted of 936 bp, which encoded a protein of 311 amino acids. The expression of GEM was higher in spleen, lung and large intestine and it appeared sharp in the interim stage of differentiation. Furthermore, GEM knockdown blocked adipogenesis and the expression of C/EBPα, C/EBPβ, LPL, PPARγ and SREBP1. These results indicated that GEM might promote lipid accumulation and adipogenesis.
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Affiliation(s)
- Qing Xu
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
| | - Yong Wang
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China.,Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Exploitation, Chengdu, Sichuan, P.R. China
| | - Jiangjiang Zhu
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China.,Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Exploitation, Chengdu, Sichuan, P.R. China
| | - Yanying Zhao
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
| | - Yaqiu Lin
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
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11
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Royer L, Herzog JJ, Kenny K, Tzvetkova B, Cochrane JC, Marr MT, Paradis S. The Ras-like GTPase Rem2 is a potent inhibitor of calcium/calmodulin-dependent kinase II activity. J Biol Chem 2018; 293:14798-14811. [PMID: 30072381 DOI: 10.1074/jbc.ra118.003560] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 07/20/2018] [Indexed: 02/05/2023] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a well-characterized, abundant protein kinase that regulates a diverse set of functions in a tissue-specific manner. For example, in heart muscle, CaMKII regulates Ca2+ homeostasis, whereas in neurons, CaMKII regulates activity-dependent dendritic remodeling and long-term potentiation (LTP), a neurobiological correlate of learning and memory. Previously, we identified the GTPase Rem2 as a critical regulator of dendrite branching and homeostatic plasticity in the vertebrate nervous system. Here, we report that Rem2 directly interacts with CaMKII and potently inhibits the activity of the intact holoenzyme, a previously unknown Rem2 function. Our results suggest that Rem2 inhibition involves interaction with both the CaMKII hub domain and substrate recognition domain. Moreover, we found that Rem2-mediated inhibition of CaMKII regulates dendritic branching in cultured hippocampal neurons. Lastly, we report that substitution of two key amino acid residues in the Rem2 N terminus (Arg-79 and Arg-80) completely abolishes its ability to inhibit CaMKII. We propose that our biochemical findings will enable further studies unraveling the functional significance of Rem2 inhibition of CaMKII in cells.
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Affiliation(s)
| | | | | | | | - Jesse C Cochrane
- Department of Molecular Biology and Genetics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Michael T Marr
- From the Department of Biology, .,Rosenstiel Basic Medical Sciences Research Center
| | - Suzanne Paradis
- From the Department of Biology, .,Volen Center for Complex Systems, and.,National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454 and
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12
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Gireesh KK, Shine A, Lakshmi RB, Vijayan V, Manna TK. GTP-binding facilitates EB1 recruitment onto microtubules by relieving its auto-inhibition. Sci Rep 2018; 8:9792. [PMID: 29955158 PMCID: PMC6023887 DOI: 10.1038/s41598-018-28056-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 06/14/2018] [Indexed: 12/23/2022] Open
Abstract
Microtubule plus end-binding protein, EB1 is a key regulator of microtubule dynamics. Auto-inhibitory interaction in EB1 has previously been shown to inhibit its ability to bind to microtubules and regulate microtubule dynamics. However, the factors that promote its microtubule regulatory activity by over-coming the auto-inhibition are less known. Here, we show that GTP plays a critical role in promoting the microtubule-targeting activity of EB1 by suppressing its auto-inhibition. Our biophysical data demonstrate that GTP binds to EB1 at a distinct site in its conserved N-terminal domain. Detailed analyses reveal that GTP-binding suppresses the intra-molecular inhibitory interaction between the globular N-terminus and the C-terminal coiled-coil domain. We further show that mutation of the GTP-binding site residues in N-terminus weakens the affinity for GTP, but also for the C-terminus, indicating overlapping binding sites. Confocal imaging and biochemical analysis reveal that EB1 localization on the microtubules is significantly increased upon mutations of the GTP-binding site residues. The results demonstrate a unique role of GTP in facilitating EB1 interaction with the microtubules by relieving its intra-molecular inhibition. They also implicate that GTP-binding may regulate the functions of EB1 on the cellular microtubules.
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Affiliation(s)
- K K Gireesh
- School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Thiruvananthapuram, 695016, Kerala, India
| | - A Shine
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Thiruvananthapuram, 695016, Kerala, India
| | - R Bhagya Lakshmi
- School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Thiruvananthapuram, 695016, Kerala, India
| | - Vinesh Vijayan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Thiruvananthapuram, 695016, Kerala, India.
| | - Tapas K Manna
- School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Thiruvananthapuram, 695016, Kerala, India.
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13
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Kenny K, Royer L, Moore AR, Chen X, Marr MT, Paradis S. Rem2 signaling affects neuronal structure and function in part by regulation of gene expression. Mol Cell Neurosci 2017; 85:190-201. [PMID: 29066292 DOI: 10.1016/j.mcn.2017.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 09/27/2017] [Accepted: 10/11/2017] [Indexed: 12/12/2022] Open
Abstract
The central nervous system has the remarkable ability to convert changes in the environment in the form of sensory experience into long-term alterations in synaptic connections and dendritic arborization, in part through changes in gene expression. Surprisingly, the molecular mechanisms that translate neuronal activity into changes in neuronal connectivity and morphology remain elusive. Rem2, a member of the Rad/Rem/Rem2/Gem/Kir (RGK) subfamily of small Ras-like GTPases, is a positive regulator of synapse formation and negative regulator of dendritic arborization. Here we identify that one output of Rem2 signaling is the regulation of gene expression. Specifically, we demonstrate that Rem2 signaling modulates the expression of genes required for a variety of cellular processes from neurite extension to synapse formation and synaptic function. Our results highlight Rem2 as a unique molecule that transduces changes in neuronal activity detected at the cell membrane to morphologically relevant changes in gene expression in the nucleus.
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Affiliation(s)
- Katelyn Kenny
- Department of Biology, Brandeis University, Waltham, MA 02454, United States
| | - Leandro Royer
- Department of Biology, Brandeis University, Waltham, MA 02454, United States
| | - Anna R Moore
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States
| | - Xiao Chen
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States
| | - Michael T Marr
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, United States
| | - Suzanne Paradis
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States.
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14
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Acquired expression of CblQ367P in mice induces dysplastic myelopoiesis mimicking chronic myelomonocytic leukemia. Blood 2017; 129:2148-2160. [PMID: 28209720 DOI: 10.1182/blood-2016-06-724658] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 02/07/2017] [Indexed: 12/20/2022] Open
Abstract
Chronic myelomonocytic leukemia (CMML) is a hematological malignancy characterized by uncontrolled proliferation of dysplastic myelomonocytes and frequent progression to acute myeloid leukemia (AML). We identified mutations in the Cbl gene, which encodes a negative regulator of cytokine signaling, in a subset of CMML patients. To investigate the contribution of mutant Cbl in CMML pathogenesis, we generated conditional knockin mice for Cbl that express wild-type Cbl in a steady state and inducibly express CblQ367P , a CMML-associated Cbl mutant. CblQ367P mice exhibited sustained proliferation of myelomonocytes, multilineage dysplasia, and splenomegaly, which are the hallmarks of CMML. The phosphatidylinositol 3-kinase (PI3K)-AKT and JAK-STAT pathways were constitutively activated in CblQ367P hematopoietic stem cells, which promoted cell cycle progression and enhanced chemokine-chemokine receptor activity. Gem, a gene encoding a GTPase that is upregulated by CblQ367P , enhanced hematopoietic stem cell activity and induced myeloid cell proliferation. In addition, Evi1, a gene encoding a transcription factor, was found to cooperate with CblQ367P and progress CMML to AML. Furthermore, targeted inhibition for the PI3K-AKT and JAK-STAT pathways efficiently suppressed the proliferative activity of CblQ367P -bearing CMML cells. Our findings provide insights into the molecular mechanisms underlying mutant Cbl-induced CMML and propose a possible molecular targeting therapy for mutant Cbl-carrying CMML patients.
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15
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Chang DD, Colecraft HM. Rad and Rem are non-canonical G-proteins with respect to the regulatory role of guanine nucleotide binding in Ca(V)1.2 channel regulation. J Physiol 2016; 593:5075-90. [PMID: 26426338 DOI: 10.1113/jp270889] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 09/27/2015] [Indexed: 12/15/2022] Open
Abstract
Rad and Rem are Ras-like G-proteins linked to diverse cardiovascular functions and pathophysiology. Understanding how Rad and Rem are regulated is important for deepened insights into their pathophysiological roles. As in other Ras-like G-proteins, Rad and Rem contain a conserved guanine-nucleotide binding domain (G-domain). Canonically, G-domains are key control modules, functioning as nucleotide-regulated switches of G-protein activity. Whether Rad and Rem G-domains conform to this canonical paradigm is ambiguous. Here, we used multiple functional measurements in HEK293 cells and cardiomyocytes (Ca(V)1.2 currents, Ca(2+) transients, Ca(V)β binding) as biosensors to probe the role of the G-domain in regulation of Rad and Rem function. We utilized Rad(S105N) and Rem(T94N), which are the cognate mutants to Ras(S17N), a dominant-negative variant of Ras that displays decreased nucleotide binding affinity. In HEK293 cells, over-expression of either Rad(S105N) or Rem(T94N) strongly inhibited reconstituted Ca(V)1.2 currents to the same extent as their wild-type (wt) counterparts, contrasting with reports that Rad(S105N) is functionally inert in HEK293 cells. Adenovirus-mediated expression of either wt Rad or Rad(S105N) in cardiomyocytes dramatically blocked L-type calcium current (I(Ca,L)) and inhibited Ca(2+)-induced Ca(2+) release, contradicting reports that Rad(S105N) acts as a dominant negative in heart. By contrast, Rem(T94N) was significantly less effective than wt Rem at inhibiting I(Ca,L) and Ca(2+) transients in cardiomyocytes. FRET analyses in cardiomyocytes revealed that both Rad(S105N) and Rem(T94N) had moderately reduced binding affinity for Ca(V)βs relative to their wt counterparts. The results indicate Rad and Rem are non-canonical G-proteins with respect to the regulatory role of their G-domain in Ca(V)1.2 regulation.
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Affiliation(s)
- Donald D Chang
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
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16
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Liput DJ, Lu VB, Davis MI, Puhl HL, Ikeda SR. Rem2, a member of the RGK family of small GTPases, is enriched in nuclei of the basal ganglia. Sci Rep 2016; 6:25137. [PMID: 27118437 PMCID: PMC4846870 DOI: 10.1038/srep25137] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 11/09/2022] Open
Abstract
Rem2 is a member of the RGK subfamily of RAS small GTPases. Rem2 inhibits high voltage activated calcium channels, is involved in synaptogenesis, and regulates dendritic morphology. Rem2 is the primary RGK protein expressed in the nervous system, but to date, the precise expression patterns of this protein are unknown. In this study, we characterized Rem2 expression in the mouse nervous system. In the CNS, Rem2 mRNA was detected in all regions examined, but was enriched in the striatum. An antibody specific for Rem2 was validated using a Rem2 knockout mouse model and used to show abundant expression in striatonigral and striatopallidal medium spiny neurons but not in several interneuron populations. In the PNS, Rem2 was abundant in a subpopulation of neurons in the trigeminal and dorsal root ganglia, but was absent in sympathetic neurons of superior cervical ganglia. Under basal conditions, Rem2 was subject to post-translational phosphorylation, likely at multiple residues. Further, Rem2 mRNA and protein expression peaked at postnatal week two, which corresponds to the period of robust neuronal maturation in rodents. This study will be useful for elucidating the functions of Rem2 in basal ganglia physiology.
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Affiliation(s)
- Daniel J. Liput
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Van B. Lu
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Margaret I. Davis
- Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Henry L. Puhl
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Stephen R. Ikeda
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
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17
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Puckerin AA, Chang DD, Subramanyam P, Colecraft HM. Similar molecular determinants on Rem mediate two distinct modes of inhibition of Ca V1.2 channels. Channels (Austin) 2016; 10:379-394. [PMID: 27115600 PMCID: PMC4988437 DOI: 10.1080/19336950.2016.1180489] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Rad/Rem/Rem2/Gem (RGK) proteins are Ras-like GTPases that potently inhibit all high-voltage-gated calcium (CaV1/CaV2) channels and are, thus, well-positioned to tune diverse physiological processes. Understanding how RGK proteins inhibit CaV channels is important for perspectives on their (patho)physiological roles and could advance their development and use as genetically-encoded CaV channel blockers. We previously reported that Rem can block surface CaV1.2 channels in 2 independent ways that engage distinct components of the channel complex: (1) by binding auxiliary β subunits (β-binding-dependent inhibition, or BBD); and (2) by binding the pore-forming α1C subunit N-terminus (α1C-binding-dependent inhibition, or ABD). By contrast, Gem uses only the BBD mechanism to block CaV1.2. Rem molecular determinants required for BBD CaV1.2 inhibition are the distal C-terminus and the guanine nucleotide binding G-domain which interact with the plasma membrane and CaVβ, respectively. However, Rem determinants for ABD CaV1.2 inhibition are unknown. Here, combining fluorescence resonance energy transfer, electrophysiology, systematic truncations, and Rem/Gem chimeras we found that the same Rem distal C-terminus and G-domain also mediate ABD CaV1.2 inhibition, but with different interaction partners. Rem distal C-terminus interacts with α1C N-terminus to anchor the G-domain which likely interacts with an as-yet-unidentified site. In contrast to some previous studies, neither the C-terminus of Rem nor Gem was sufficient to inhibit CaV1/CaV2 channels. The results reveal that similar molecular determinants on Rem are repurposed to initiate 2 independent mechanisms of CaV1.2 inhibition.
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Affiliation(s)
- Akil A Puckerin
- a Department of Pharmacology & Molecular Signaling , Columbia University , New York , NY , USA
| | - Donald D Chang
- b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
| | - Prakash Subramanyam
- b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
| | - Henry M Colecraft
- a Department of Pharmacology & Molecular Signaling , Columbia University , New York , NY , USA.,b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
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Puhl HL, Lu VB, Won YJ, Sasson Y, Hirsch JA, Ono F, Ikeda SR. Ancient origins of RGK protein function: modulation of voltage-gated calcium channels preceded the protostome and deuterostome split. PLoS One 2014; 9:e100694. [PMID: 24992013 PMCID: PMC4081519 DOI: 10.1371/journal.pone.0100694] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 05/23/2014] [Indexed: 11/21/2022] Open
Abstract
RGK proteins, Gem, Rad, Rem1, and Rem2, are members of the Ras superfamily of small GTP-binding proteins that interact with Ca2+ channel β subunits to modify voltage-gated Ca2+ channel function. In addition, RGK proteins affect several cellular processes such as cytoskeletal rearrangement, neuronal dendritic complexity, and synapse formation. To probe the phylogenetic origins of RGK protein–Ca2+ channel interactions, we identified potential RGK-like protein homologs in genomes for genetically diverse organisms from both the deuterostome and protostome animal superphyla. RGK-like protein homologs cloned from Danio rerio (zebrafish) and Drosophila melanogaster (fruit flies) expressed in mammalian sympathetic neurons decreased Ca2+ current density as reported for expression of mammalian RGK proteins. Sequence alignments from evolutionarily diverse organisms spanning the protostome/deuterostome divide revealed conservation of residues within the RGK G-domain involved in RGK protein – Cavβ subunit interaction. In addition, the C-terminal eleven residues were highly conserved and constituted a signature sequence unique to RGK proteins but of unknown function. Taken together, these data suggest that RGK proteins, and the ability to modify Ca2+ channel function, arose from an ancestor predating the protostomes split from deuterostomes approximately 550 million years ago.
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Affiliation(s)
- Henry L. Puhl
- Laboratory of Molecular Physiology, Section on Transmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Van B. Lu
- Laboratory of Molecular Physiology, Section on Transmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Yu-Jin Won
- Laboratory of Molecular Physiology, Section on Transmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Yehezkel Sasson
- Department of Biochemistry & Molecular Biology, Faculty of Life Sciences, Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Joel A. Hirsch
- Department of Biochemistry & Molecular Biology, Faculty of Life Sciences, Institute for Structural Biology, Tel Aviv University, Ramat Aviv, Israel
| | - Fumihito Ono
- Laboratory of Molecular Physiology, Section on Model Synaptic Systems, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Stephen R. Ikeda
- Laboratory of Molecular Physiology, Section on Transmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
- * E-mail:
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Ghiretti AE, Paradis S. Molecular mechanisms of activity-dependent changes in dendritic morphology: role of RGK proteins. Trends Neurosci 2014; 37:399-407. [PMID: 24910262 PMCID: PMC4113564 DOI: 10.1016/j.tins.2014.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 05/09/2014] [Accepted: 05/13/2014] [Indexed: 01/10/2023]
Abstract
The nervous system has the amazing capacity to transform sensory experience from the environment into changes in neuronal activity that, in turn, cause long-lasting alterations in neuronal morphology. Recent findings indicate that, surprisingly, sensory experience concurrently activates molecular signaling pathways that both promote and inhibit dendritic complexity. Historically, a number of positive regulators of activity-dependent dendritic complexity have been described, whereas the list of identified negative regulators of this process is much shorter. In recent years, there has been an emerging appreciation of the importance of the Rad/Rem/Rem2/Gem/Kir (RGK) GTPases as mediators of activity-dependent structural plasticity. In the following review, we discuss the traditional view of RGK proteins, as well as our evolving understanding of the role of these proteins in instructing structural plasticity.
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Affiliation(s)
- Amy E Ghiretti
- Department of Biology, National Center for Behavioral Genomics, and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA
| | - Suzanne Paradis
- Department of Biology, National Center for Behavioral Genomics, and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA.
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20
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Abstract
A key feature of the CNS is structural plasticity, the ability of neurons to alter their morphology and connectivity in response to sensory experience and other changes in the environment. How this structural plasticity is achieved at the molecular level is not well understood. We provide evidence that changes in sensory experience simultaneously trigger multiple signaling pathways that either promote or restrict growth of the dendritic arbor; structural plasticity is achieved through a balance of these opposing signals. Specifically, we have uncovered a novel, activity-dependent signaling pathway that restricts dendritic arborization. We demonstrate that the GTPase Rem2 is regulated at the transcriptional level by calcium influx through L-VGCCs and inhibits dendritic arborization in cultured rat cortical neurons and in the Xenopus laevis tadpole visual system. Thus, our results demonstrate that changes in neuronal activity initiate competing signaling pathways that positively and negatively regulate the growth of the dendritic arbor. It is the balance of these opposing signals that leads to proper dendritic morphology.
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21
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Chandra M, Mukherjee M, Srivastava VK, Saito-Nakano Y, Nozaki T, Datta S. Insights into the GTP/GDP cycle of RabX3, a novel GTPase from Entamoeba histolytica with tandem G-domains. Biochemistry 2014; 53:1191-205. [PMID: 24471929 DOI: 10.1021/bi401428f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Members of the small GTPase Ras superfamily regulate a host of systems through their ability to catalyze the GTP/GDP cycle. All family members reported thus far possess a single GTPase domain with a P-loop containing a nucleoside triphosphate hydrolase fold. Here for the first time we report a novel member from Entamoeba histolytica, EhRabX3, which harbors two GTPase domains in tandem and exhibits unique biochemical properties. A combination of biochemical and microcalorimetric studies revealed that EhRabX3 binds to a single guanine nucleotide through its N-terminal domain. Unlike most of the members of the Ras superfamily, the dissociation of the nucleotide from EhRabX3 is independent of Mg(2+), perhaps indicating a novel mechanism of nucleotide exchange by this protein. We found that EhRabX3 is extremely sluggish in hydrolyzing GTP, and that could be attributed to its atypical nucleotide binding pocket. It harbors substitutions at two positions that confer oncogenicity to Ras because of impaired GTP hydrolysis. Engineering these residues into the conserved counterparts enhanced their GTPase activity by at least 20-fold. In contrast to most of the members of the Ras superfamily, EhRabX3 lacks the prenylation motif. Using indirect immunofluorescence and biochemical fractionation, we demonstrated that the protein is distributed all over the cytosol in amoebic trophozoites. Collectively, this unique ancient GTPase exhibits a striking evolutionary divergence from the other members of the superfamily.
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Affiliation(s)
- Mintu Chandra
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal , Bhopal 462023, India
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22
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CaMKII-dependent phosphorylation of the GTPase Rem2 is required to restrict dendritic complexity. J Neurosci 2013; 33:6504-15. [PMID: 23575848 DOI: 10.1523/jneurosci.3861-12.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The morphogenesis of the dendritic arbor is a critical aspect of neuronal development, ensuring that proper neural networks are formed. However, the molecular mechanisms that underlie this dendritic remodeling remain obscure. We previously established the activity-regulated GTPase Rem2 as a negative regulator of dendritic complexity. In this study, we identify a signaling pathway whereby Rem2 regulates dendritic arborization through interactions with Ca(2+)/calmodulin-dependent kinases (CaMKs) in rat hippocampal neurons. Specifically, we demonstrate that Rem2 functions downstream of CaMKII but upstream of CaMKIV in a pathway that restricts dendritic complexity. Furthermore, we show that Rem2 is a novel substrate of CaMKII and that phosphorylation of Rem2 by CaMKII regulates Rem2 function and subcellular localization. Overall, our results describe a unique signal transduction network through which Rem2 and CaMKs function to restrict dendritic complexity.
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Yang T, Colecraft HM. Regulation of voltage-dependent calcium channels by RGK proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1644-54. [PMID: 23063948 DOI: 10.1016/j.bbamem.2012.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 10/04/2012] [Accepted: 10/05/2012] [Indexed: 12/28/2022]
Abstract
RGK proteins belong to the Ras superfamily of monomeric G-proteins, and currently include four members - Rad, Rem, Rem2, and Gem/Kir. RGK proteins are broadly expressed, and are the most potent known intracellular inhibitors of high-voltage-activated Ca²⁺ (Ca(V)1 and Ca(V)2) channels. Here, we review and discuss the evidence in the literature regarding the functional mechanisms, structural determinants, physiological role, and potential practical applications of RGK-mediated inhibition of Ca(V)1/Ca(V)2 channels. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Tingting Yang
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, 1150 St. Nicholas Avenue, New York, NY 10032, USA
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24
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Gunton JE, Sisavanh M, Stokes RA, Satin J, Satin LS, Zhang M, Liu SM, Cai W, Cheng K, Cooney GJ, Laybutt DR, So T, Molero JC, Grey ST, Andres DA, Rolph MS, Mackay CR. Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling. PLoS One 2012; 7:e39462. [PMID: 22761801 PMCID: PMC3386271 DOI: 10.1371/journal.pone.0039462] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/21/2012] [Indexed: 11/29/2022] Open
Abstract
Aims and Hypothesis Glucose-stimulated insulin secretion from beta-cells is a tightly regulated process that requires calcium flux to trigger exocytosis of insulin-containing vesicles. Regulation of calcium handling in beta-cells remains incompletely understood. Gem, a member of the RGK (Rad/Gem/Kir) family regulates calcium channel handling in other cell types, and Gem over-expression inhibits insulin release in insulin-secreting Min6 cells. The aim of this study was to explore the role of Gem in insulin secretion. We hypothesised that Gem may regulate insulin secretion and thus affect glucose tolerance in vivo. Methods Gem-deficient mice were generated and their metabolic phenotype characterised by in vivo testing of glucose tolerance, insulin tolerance and insulin secretion. Calcium flux was measured in isolated islets. Results Gem-deficient mice were glucose intolerant and had impaired glucose stimulated insulin secretion. Furthermore, the islets of Gem-deficient mice exhibited decreased free calcium responses to glucose and the calcium oscillations seen upon glucose stimulation were smaller in amplitude and had a reduced frequency. Conclusions These results suggest that Gem plays an important role in normal beta-cell function by regulation of calcium signalling.
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Affiliation(s)
- Jenny E Gunton
- Diabetes and Transcription Factors Group, Garvan Institute of Medical Research, Sydney, Australia.
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Reymond P, Coquard A, Chenon M, Zeghouf M, El Marjou A, Thompson A, Ménétrey J. Structure of the GDP-bound G domain of the RGK protein Rem2. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:626-31. [PMID: 22684057 PMCID: PMC3370897 DOI: 10.1107/s1744309112013541] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 03/28/2012] [Indexed: 11/10/2022]
Abstract
RGK proteins are atypical small GTP-binding proteins that are involved in the regulation of voltage-dependent calcium channels and actin cytoskeleton remodelling. The structure of the Rem2 G domain bound to GDP is reported here in a monoclinic crystal form at 2.66 Å resolution. It is very similar to the structure determined previously from an orthorhombic crystal form. However, differences in the crystal-packing environment revealed that the switch I and switch II regions are flexible and not ordered as previously reported. Comparison of the available RGK protein structures along with those of other small GTP-binding proteins highlights two structural features characteristic of this atypical family and suggests that the conserved tryptophan residue in the DXWEX motif may be a structural determinant of the nucleotide-binding affinity.
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Affiliation(s)
- Philippe Reymond
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre de Recherche de Gif, CNRS, 91198 Gif-sur-Yvette, France
- ED 387 iViv, Université Pierre et Marie Curie, 75005 Paris, France
| | - Aline Coquard
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre de Recherche de Gif, CNRS, 91198 Gif-sur-Yvette, France
| | - Mélanie Chenon
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre de Recherche de Gif, CNRS, 91198 Gif-sur-Yvette, France
| | - Mahel Zeghouf
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre de Recherche de Gif, CNRS, 91198 Gif-sur-Yvette, France
| | - Ahmed El Marjou
- Institut Curie, Centre de Recherche, 75248 Paris, France
- CNRS UMR144, 26 Rue d’Ulm, 75248 Paris, France
| | - Andrew Thompson
- Synchrotron SOLEIL, L’Orme des Merisiers, BP 48 St Aubin, 91192 Gif-sur-Yvette, France
| | - Julie Ménétrey
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre de Recherche de Gif, CNRS, 91198 Gif-sur-Yvette, France
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