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Gan L, Deng Z, Wei Y, Li H, Zhao L. Decreased expression of GEM in osteoarthritis cartilage regulates chondrogenic differentiation via Wnt/β-catenin signaling. J Orthop Surg Res 2023; 18:751. [PMID: 37794464 PMCID: PMC10548561 DOI: 10.1186/s13018-023-04236-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
BACKGROUND GEM (GTP-binding protein overexpressed in skeletal muscle) is one of the atypical small GTPase subfamily members recently identified as a regulator of cell differentiation. Abnormal chondrogenesis coupled with an imbalance in the turnover of cartilaginous matrix formation is highly relevant to the onset and progression of osteoarthritis (OA). However, how GEM regulates chondrogenic differentiation remains unexplored. METHODS Cartilage tissues were obtained from OA patients and graded according to the ORASI and ICRS grading systems. The expression alteration of GEM was detected in the Grade 4 cartilage compared to Grade 0 and verified in OA mimic culture systems. Next, to investigate the specific function of GEM during these processes, we generated a Gem knockdown (Gem-Kd) system by transfecting siRNA targeting Gem into ATDC5 cells. Acan, Col2a1, Sox9, and Wnt target genes of Gem-Kd ATDC5 cells were detected during induction. The transcriptomic sequencing analysis was performed to investigate the mechanism of GEM regulation. Wnt signaling pathways were verified by real-time PCR and immunoblot analysis. Finally, a rescue model generated by treating Gem-KD ATDC5 cells with a Wnt signaling agonist was established to validate the mechanism identified by RNA sequencing analysis. RESULTS A decreased expression of GEM in OA patients' cartilage tissues and OA mimic chondrocytes was observed. While during chondrogenesis differentiation and cartilage matrix formation, the expression of GEM was increased. Gem silencing suppressed chondrogenic differentiation and the expressions of Acan, Col2a1, and Sox9. RNA sequencing analysis revealed that Wnt signaling was downregulated in Gem-Kd cells. Decreased expression of Wnt signaling associated genes and the total β-CATENIN in the nucleus and cytoplasm were observed. The exogenous Wnt activation exhibited reversed effect on Gem loss-of-function cells. CONCLUSION These findings collectively validated that GEM functions as a novel regulator mediating chondrogenic differentiation and cartilage matrix formation through Wnt/β-catenin signaling.
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Affiliation(s)
- Lu Gan
- Department of Orthopaedic Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Zhonghao Deng
- Department of Orthopaedic Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Yiran Wei
- Department of Orthopaedic Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | | | - Liang Zhao
- Department of Orthopaedic Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, Guangdong, China.
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Southern Medical University, Guangzhou, 510515, Guangdong, China.
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Sun Z, Li Y, Tan X, Liu W, He X, Pan D, Li E, Xu L, Long L. Friend or Foe: Regulation, Downstream Effectors of RRAD in Cancer. Biomolecules 2023; 13:biom13030477. [PMID: 36979412 PMCID: PMC10046484 DOI: 10.3390/biom13030477] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/28/2023] [Accepted: 03/01/2023] [Indexed: 03/08/2023] Open
Abstract
Ras-related associated with diabetes (RRAD), a member of the Ras-related GTPase superfamily, is primarily a cytosolic protein that actives in the plasma membrane. RRAD is highly expressed in type 2 diabetes patients and as a biomarker of congestive heart failure. Mounting evidence showed that RRAD is important for the progression and metastasis of tumor cells, which play opposite roles as an oncogene or tumor suppressor gene depending on cancer and cell type. These findings are of great significance, especially given that relevant molecular mechanisms are being discovered. Being regulated in various pathways, RRAD plays wide spectrum cellular activity including tumor cell division, motility, apoptosis, and energy metabolism by modulating tumor-related gene expression and interacting with multiple downstream effectors. Additionally, RRAD in senescence may contribute to its role in cancer. Despite the twofold characters of RRAD, targeted therapies are becoming a potential therapeutic strategy to combat cancers. This review will discuss the dual identity of RRAD in specific cancer type, provides an overview of the regulation and downstream effectors of RRAD to offer valuable insights for readers, explore the intracellular role of RRAD in cancer, and give a reference for future mechanistic studies.
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Affiliation(s)
- Zhangyue Sun
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
| | - Yongkang Li
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
| | - Xiaolu Tan
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
| | - Wanyi Liu
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
| | - Xinglin He
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
| | - Deyuan Pan
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, Shantou 515041, China
| | - Enmin Li
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, Shantou 515041, China
| | - Liyan Xu
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, Shantou 515041, China
| | - Lin Long
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 515041, China
- Cancer Research Center, Institute of Basic Medical Science, Shantou University Medical College, Shantou 515041, China
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
- The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, Shantou 515041, China
- Correspondence: ; Tel.: +86-754-88900460; Fax: +86-754-88900847
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3
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Del Rivero Morfin PJ, Marx SO, Ben-Johny M. Sympathetic Nervous System Regulation of Cardiac Calcium Channels. Handb Exp Pharmacol 2023. [PMID: 36592229 DOI: 10.1007/164_2022_632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Calcium influx through voltage-gated calcium channels, Cav1.2, in cardiomyocytes initiates excitation-contraction coupling in the heart. The force and rate of cardiac contraction are modulated by the sympathetic nervous system, mediated substantially by changes in intracellular calcium. Norepinephrine released from sympathetic neurons innervating the heart and epinephrine secreted by the adrenal chromaffin cells bind to β-adrenergic receptors on the sarcolemma of cardiomyocytes initiating a signaling cascade that generates cAMP and activates protein kinase A, the targets of which control calcium influx. For decades, the mechanisms by which PKA regulated calcium channels in the heart were not known. Recently, these mechanisms have been elucidated. In this chapter, we will review the history of the field and the studies that led to the identification of the evolutionarily conserved process.
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Affiliation(s)
- Pedro J Del Rivero Morfin
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Steven O Marx
- Division of Cardiology, Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA. .,Department of Pharmacology and Molecular Signaling, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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4
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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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5
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Buraei Z, Lumen E, Kaur S, Yang J. RGK regulation of voltage-gated calcium channels. SCIENCE CHINA-LIFE SCIENCES 2015; 58:28-38. [PMID: 25576452 PMCID: PMC9074095 DOI: 10.1007/s11427-014-4788-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 09/02/2014] [Indexed: 01/01/2023]
Abstract
Voltage-gated calcium channels (VGCCs) play critical roles in cardiac and skeletal muscle contractions, hormone and neurotransmitter release, as well as slower processes such as cell proliferation, differentiation, migration and death. Mutations in VGCCs lead to numerous cardiac, muscle and neurological disease, and their physiological function is tightly regulated by kinases, phosphatases, G-proteins, calmodulin and many other proteins. Fifteen years ago, RGK proteins were discovered as the most potent endogenous regulators of VGCCs. They are a family of monomeric GTPases (Rad, Rem, Rem2, and Gem/Kir), in the superfamily of Ras GTPases, and they have two known functions: regulation of cytoskeletal dynamics including dendritic arborization and inhibition of VGCCs. Here we review the mechanisms and molecular determinants of RGK-mediated VGCC inhibition, the physiological impact of this inhibition, and recent evidence linking the two known RGK functions.
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Affiliation(s)
- Zafir Buraei
- Department of Biology, Pace University, New York, NY, 10038, USA,
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6
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Abstract
The Ras superfamily G-proteins are monomeric proteins of approximately 21kDa that act as a molecular switch to regulate a variety of cellular processes. The structure of the Ras superfamily G-proteins, their regulators as well as posttranslational modification of these proteins leading to their membrane association have been elucidated. The Ras superfamily G-proteins interact at their effector domains with their downstream effectors via protein-protein interactions. Mutational activation or overexpression of the Ras superfamily G-proteins has been observed in a number of human cancer cases. Over the years, a variety of approaches to inhibit the Ras superfamily G-proteins have been developed. These different approaches are discussed in this volume.
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Affiliation(s)
- Ashley L Tetlow
- Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, California, USA
| | - Fuyuhiko Tamanoi
- Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, California, USA.
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7
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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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8
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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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9
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Fan M, Zhang WK, Buraei Z, Yang J. Molecular determinants of Gem protein inhibition of P/Q-type Ca2+ channels. J Biol Chem 2012; 287:22749-58. [PMID: 22589533 DOI: 10.1074/jbc.m111.291872] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The RGK family of monomeric GTP-binding proteins potently inhibits high voltage-activated Ca(2+) channels. The molecular mechanisms of this inhibition are largely unclear. In Xenopus oocytes, Gem suppresses the activity of P/Q-type Ca(2+) channels on the plasma membrane. This is presumed to occur through direct interactions of one or more Gem inhibitory sites and the pore-forming Ca(v)2.1 subunit in a manner dependent on the Ca(2+) channel subunit β (Ca(v)β). In this study we investigated the molecular determinants in Gem that are critical for this inhibition. Like other RGK proteins, Gem contains a conserved Ras-like core and extended N and C termini. A 12-amino acid fragment in the C terminus was found to be crucial for and sufficient to produce Ca(v)β-dependent inhibition, suggesting that this region forms an inhibitory site. A three-amino acid motif in the core was also found to be critical, possibly forming another inhibitory site. Mutating either site individually did not hamper Gem inhibition, but mutating both sites together completely abolished Gem inhibition without affecting Gem protein expression level or disrupting Gem interaction with Ca(v)2.1 or Ca(v)β. Mutating Gem residues that are crucial for interactions with previously demonstrated RGK modulators such as calmodulin, 14-3-3, and phosphatidylinositol lipids did not significantly affect Gem inhibition. These results suggest that Gem contains two candidate inhibitory sites, each capable of producing full inhibition of P/Q-type Ca(2+) channels.
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Affiliation(s)
- Mingming Fan
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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10
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Wittinghofer A, Vetter IR. Structure-function relationships of the G domain, a canonical switch motif. Annu Rev Biochem 2011; 80:943-71. [PMID: 21675921 DOI: 10.1146/annurev-biochem-062708-134043] [Citation(s) in RCA: 333] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
GTP-binding (G) proteins constitute a class of P-loop (phosphate-binding loop) proteins that work as molecular switches between the GDP-bound OFF and the GTP-bound ON state. The common principle is the 160-180-residue G domain with an α,β topology that is responsible for nucleotide-dependent conformational changes and drives many biological functions. Although the G domain uses a universally conserved switching mechanism, its structure, function, and GTPase reaction are modified for many different pathways and processes.
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11
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Sasson Y, Navon-Perry L, Huppert D, Hirsch JA. RGK family G-domain:GTP analog complex structures and nucleotide-binding properties. J Mol Biol 2011; 413:372-89. [PMID: 21903096 DOI: 10.1016/j.jmb.2011.08.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 08/08/2011] [Accepted: 08/09/2011] [Indexed: 11/26/2022]
Abstract
The RGK family of small G-proteins, including Rad, Gem, Rem1, and Rem2, is inducibly expressed in various mammalian tissues and interacts with voltage-dependent calcium channels and Rho kinase. Many questions remain regarding their physiological roles and molecular mechanism. Previous crystallographic studies reported RGK G-domain:guanosine di-phosphate structures. To test whether RGK proteins undergo a nucleotide-induced conformational change, we determined the crystallographic structures of Rad:GppNHp and Rem2:GppNHp to 1.7 and 1.8 Å resolutions, respectively. Also, we characterized the nucleotide-binding properties and conformations for Gem, Rad, and several structure-based mutants using fluorescence spectroscopy. The results suggest that RGK G-proteins may not behave as Ras-like canonical nucleotide-induced molecular switches. Further, the RGK proteins have differing structures and nucleotide-binding properties, which may have implications for their varied action on effectors.
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Affiliation(s)
- Yehezkel Sasson
- Department of Biochemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
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12
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Minor DL, Findeisen F. Progress in the structural understanding of voltage-gated calcium channel (CaV) function and modulation. Channels (Austin) 2011; 4:459-74. [PMID: 21139419 DOI: 10.4161/chan.4.6.12867] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Voltage-gated calcium channels (CaVs) are large, transmembrane multiprotein complexes that couple membrane depolarization to cellular calcium entry. These channels are central to cardiac action potential propagation, neurotransmitter and hormone release, muscle contraction, and calcium-dependent gene transcription. Over the past six years, the advent of high-resolution structural studies of CaV components from different isoforms and CaV modulators has begun to reveal the architecture that underlies the exceptionally rich feedback modulation that controls CaV action. These descriptions of CaV molecular anatomy have provided new, structure-based insights into the mechanisms by which particular channel elements affect voltage-dependent inactivation (VDI), calcium‑dependent inactivation (CDI), and calcium‑dependent facilitation (CDF). The initial successes have been achieved through structural studies of soluble channel domains and modulator proteins and have proven most powerful when paired with biochemical and functional studies that validate ideas inspired by the structures. Here, we review the progress in this growing area and highlight some key open challenges for future efforts.
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Affiliation(s)
- Daniel L Minor
- Cardiovascular Research Institute, University of California-San Francisco, CA, USA.
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13
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Abstract
Calcium regulates a wide spectrum of physiological processes such as heartbeat, muscle contraction, neuronal communication, hormone release, cell division, and gene transcription. Major entryways for Ca(2+) in excitable cells are high-voltage activated (HVA) Ca(2+) channels. These are plasma membrane proteins composed of several subunits, including α(1), α(2)δ, β, and γ. Although the principal α(1) subunit (Ca(v)α(1)) contains the channel pore, gating machinery and most drug binding sites, the cytosolic auxiliary β subunit (Ca(v)β) plays an essential role in regulating the surface expression and gating properties of HVA Ca(2+) channels. Ca(v)β is also crucial for the modulation of HVA Ca(2+) channels by G proteins, kinases, and the Ras-related RGK GTPases. New proteins have emerged in recent years that modulate HVA Ca(2+) channels by binding to Ca(v)β. There are also indications that Ca(v)β may carry out Ca(2+) channel-independent functions, including directly regulating gene transcription. All four subtypes of Ca(v)β, encoded by different genes, have a modular organization, consisting of three variable regions, a conserved guanylate kinase (GK) domain, and a conserved Src-homology 3 (SH3) domain, placing them into the membrane-associated guanylate kinase (MAGUK) protein family. Crystal structures of Ca(v)βs reveal how they interact with Ca(v)α(1), open new research avenues, and prompt new inquiries. In this article, we review the structure and various biological functions of Ca(v)β, with both a historical perspective as well as an emphasis on recent advances.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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14
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Correll RN, Pang C, Niedowicz DM, Finlin BS, Andres DA. The RGK family of GTP-binding proteins: regulators of voltage-dependent calcium channels and cytoskeleton remodeling. Cell Signal 2008; 20:292-300. [PMID: 18042346 PMCID: PMC2254326 DOI: 10.1016/j.cellsig.2007.10.028] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 10/30/2007] [Indexed: 02/05/2023]
Abstract
RGK proteins constitute a novel subfamily of small Ras-related proteins that function as potent inhibitors of voltage-dependent (VDCC) Ca(2+) channels and regulators of actin cytoskeletal dynamics. Within the larger Ras superfamily, RGK proteins have distinct regulatory and structural characteristics, including nonconservative amino acid substitutions within regions known to participate in nucleotide binding and hydrolysis and a C-terminal extension that contains conserved regulatory sites which control both subcellular localization and function. RGK GTPases interact with the VDCC beta-subunit (Ca(V)beta) and inhibit Rho/Rho kinase signaling to regulate VDCC activity and the cytoskeleton respectively. Binding of both calmodulin and 14-3-3 to RGK proteins, and regulation by phosphorylation controls cellular trafficking and the downstream signaling of RGK proteins, suggesting that a complex interplay between interacting protein factors and trafficking contribute to their regulation.
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Affiliation(s)
- Robert N Correll
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, United States
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15
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Béguin P, Ng YJA, Krause C, Mahalakshmi RN, Ng MY, Hunziker W. RGK small GTP-binding proteins interact with the nucleotide kinase domain of Ca2+-channel beta-subunits via an uncommon effector binding domain. J Biol Chem 2007; 282:11509-20. [PMID: 17303572 DOI: 10.1074/jbc.m606423200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RGK proteins (Kir/Gem, Rad, Rem, and Rem2) form a small subfamily of the Ras superfamily. Despite a conserved GTP binding core domain, several differences suggest that structure, mechanism of action, and functional regulation differ from Ras. RGK proteins down-regulate voltage-gated calcium channel activity by binding in a GTP-dependent fashion to the Cavbeta subunits. Mutational analysis combined with homology modeling reveal a novel effector binding mechanism distinct from that of other Ras GTPases. In this model the Switch 1 region acts as an allosteric activator that facilitates electrostatic interactions between Arg-196 in Kir/Gem and Asp-194, -270, and -272 in the nucleotide-kinase (NK) domain of Cavbeta3 and wedging Val-223 and His-225 of Kir/Gem into a hydrophobic pocket in the NK domain. Kir/Gem interacts with a surface on the NK domain that is distinct from the groove where the voltage-gated calcium channel Cavalpha1 subunit binds. A complex composed of the RGK protein and the Cavbeta3 and Cav1.2 subunits could be revealed in vivo using coimmunoprecipitation experiments. Intriguingly, docking of the RGK protein to the NK domain of the Cavbeta subunit is reminiscent of the binding of GMP to guanylate kinase.
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Affiliation(s)
- Pascal Béguin
- Epithelial Cell Biology Laboratory, Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Republic of Singapore
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Opatowsky Y, Sasson Y, Shaked I, Ward Y, Chomsky-Hecht O, Litvak Y, Selinger Z, Kelly K, Hirsch JA. Structure-function studies of the G-domain from human gem, a novel small G-protein. FEBS Lett 2006; 580:5959-64. [PMID: 17052716 PMCID: PMC1934412 DOI: 10.1016/j.febslet.2006.09.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 09/14/2006] [Accepted: 09/28/2006] [Indexed: 10/24/2022]
Abstract
Gem, a member of the Rad,Gem/Kir subfamily of small G-proteins, has unique sequence features. We report here the crystallographic structure determination of the Gem G-domain in complex with nucleotide to 2.4 A resolution. Although the basic Ras protein fold is maintained, the Gem switch regions emphatically differ from the Ras paradigm. Our ensuing biochemical characterization indicates that Gem G-domain markedly prefers GDP over GTP. Two known functions of Gem are distinctly affected by spatially separated clusters of mutations.
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Affiliation(s)
- Yarden Opatowsky
- Department of Biochemistry, Faculty of Life Sciences, Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Yehezkel Sasson
- Department of Biochemistry, Faculty of Life Sciences, Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Isabella Shaked
- Department of Biochemistry, Faculty of Life Sciences, Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Yvona Ward
- Cell and Cancer Biology Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Orna Chomsky-Hecht
- Department of Biochemistry, Faculty of Life Sciences, Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Yael Litvak
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Zvi Selinger
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Kathleen Kelly
- Cell and Cancer Biology Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Joel A. Hirsch
- Department of Biochemistry, Faculty of Life Sciences, Daniella Rich Institute for Structural Biology, Tel Aviv University, Ramat Aviv 69978, Israel
- *Corresponding author. Fax: +972 3 6407931., E-mail address: (J.A. Hirsch)
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