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Chan KYY, Chung PY, Zhang C, Poon ENY, Leung AWK, Leung KT. R4 RGS proteins as fine tuners of immature and mature hematopoietic cell trafficking. J Leukoc Biol 2022; 112:785-797. [PMID: 35694792 DOI: 10.1002/jlb.1mr0422-475r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 04/28/2022] [Indexed: 11/08/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are the largest and most diverse group of membrane receptors. They are involved in almost every physiologic process and consequently have a pivotal role in an extensive number of pathologies, including genetic, neurologic, and immune system disorders. Indeed, the vast array of GPCRs mechanisms have led to the development of a tremendous number of drug therapies and already account for about a third of marketed drugs. These receptors mediate their downstream signals primarily via G proteins. The regulators of G-protein signaling (RGS) proteins are now in the spotlight as the critical modulatory factors of active GTP-bound Gα subunits of heterotrimeric G proteins to fine-tune the biologic responses driven by the GPCRs. Also, they possess noncanonical functions by multiple mechanisms, such as protein-protein interactions. Essential roles and impacts of these RGS proteins have been revealed in physiology, including hematopoiesis and immunity, and pathologies, including asthma, cancers, and neurologic disorders. This review focuses on the largest subfamily of R4 RGS proteins and provides a brief overview of their structures and G-proteins selectivity. With particular interest, we explore and highlight, their expression in the hematopoietic system and the regulation in the engraftment of hematopoietic stem/progenitor cells (HSPCs). Distinct expression patterns of R4 RGS proteins in the hematopoietic system and their pivotal roles in stem cell trafficking pave the way for realizing new strategies for enhancing the clinical performance of hematopoietic stem cell transplantation. Finally, we discuss the exciting future trends in drug development by targeting RGS activity and expression with small molecules inhibitors and miRNA approaches.
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Affiliation(s)
- Kathy Yuen Yee Chan
- Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Po Yee Chung
- Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Chi Zhang
- Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Ellen Ngar Yun Poon
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Alex Wing Kwan Leung
- Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, China.,Department of Paediatrics & Adolescent Medicine, Hong Kong Children's Hospital, Hong Kong SAR, China
| | - Kam Tong Leung
- Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, China.,Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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Sebastian S, Nobles M, Tsisanova E, Ludwig A, Munroe PB, Tinker A. The role of resistance to inhibitors of cholinesterase 8b in the control of heart rate. Physiol Genomics 2021; 53:150-159. [PMID: 33719582 DOI: 10.1152/physiolgenomics.00157.2020] [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: 11/22/2022] Open
Abstract
We have assessed the role of ric-b8 in the control of heart rate after the gene was implicated in a recent genome-wide association study of resting heart rate. We developed a novel murine model in which it was possible to conditionally delete ric-8b in the sinoatrial (SA) node after the addition of tamoxifen. Despite this, we were unable to obtain homozygotes and thus studied heterozygotes. Haploinsufficiency of ric-8b in the sinoatrial node induced by the addition of tamoxifen in adult animals leads to mice with a reduced heart rate. However, other electrocardiographic intervals (e.g., PR and QRS) were normal, and there was no apparent arrhythmia such as heart block. The positive chronotropic response to isoprenaline was abrogated, whereas the response to carbachol was unchanged. The pacemaker current If (funny current) has an important role in regulating heart rate, and its function is modulated by both isoprenaline and carbachol. Using a heterologous system expressing HCN4, we show that ric-8b can modulate the HCN4 current. Overexpression of ric-8b led to larger HCN4 currents, whereas silencing ric-8b led to smaller currents. Ric-8b modulates heart rate responses in vivo likely via its actions on the stimulatory G-protein.
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Affiliation(s)
- Sonia Sebastian
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Muriel Nobles
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Elena Tsisanova
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Andreas Ludwig
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Patricia B Munroe
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Andrew Tinker
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
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Tinker A, Finlay M, Nobles M, Opel A. The contribution of pathways initiated via the Gq\11 G-protein family to atrial fibrillation. Pharmacol Res 2016; 105:54-61. [DOI: 10.1016/j.phrs.2015.11.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 11/19/2015] [Indexed: 01/28/2023]
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Opel A, Nobles M, Montaigne D, Finlay M, Anderson N, Breckenridge R, Tinker A. Absence of the Regulator of G-protein Signaling, RGS4, Predisposes to Atrial Fibrillation and Is Associated with Abnormal Calcium Handling. J Biol Chem 2015; 290:19233-44. [PMID: 26088132 PMCID: PMC4521044 DOI: 10.1074/jbc.m115.666719] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 06/15/2015] [Indexed: 01/11/2023] Open
Abstract
The description of potential molecular substrates for predisposition to atrial fibrillation (AF) is incomplete, and it is unknown what role regulators of G-protein signaling might play. We address whether the attenuation of RGS4 function may promote AF and the mechanism through which this occurs. For this purpose, we studied a mouse with global genetic deletion of RGS4 (RGS4(-/-)) and the normal littermate controls (RGS4(+/+)). In vivo electrophysiology using atrial burst pacing revealed that mice with global RGS4 deletion developed AF more frequently than control littermates. Isolated atrial cells from RGS4(-/-) mice show an increase in Ca(2+) spark frequency under basal conditions and after the addition of endothelin-1 and abnormal spontaneous Ca(2+) release events after field stimulation. Isolated left atria studied on a multielectrode array revealed modest changes in path length for re-entry but abnormal electrical events after a pacing train in RGS4(-/-) mice. RGS4 deletion results in a predisposition to atrial fibrillation from enhanced activity in the Gαq/11-IP3 pathway, resulting in abnormal Ca(2+) release and corresponding electrical events.
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Affiliation(s)
- Aaisha Opel
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Muriel Nobles
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - David Montaigne
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Malcolm Finlay
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Naomi Anderson
- the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
| | - Ross Breckenridge
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and
| | - Andrew Tinker
- From the British Heart Foundation Laboratories, Department of Medicine, University College London, Rayne Institute, London WC1E 6JJ, United Kingdom and the William Harvey Heart Centre, Barts & The London School of Medicine & Dentistry, London EC1M 6BQ, United Kingdom
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Zylbergold P, Ramakrishnan N, Hebert T. The role of G proteins in assembly and function of Kir3 inwardly rectifying potassium channels. Channels (Austin) 2010; 4:411-21. [PMID: 20855978 DOI: 10.4161/chan.4.5.13327] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Kir3 channels (also known as GIRK channels) are important regulators of electrical excitability in both cardiomyocytes and neurons. Much is known regarding the assembly and function of these channels and the roles that their interacting proteins play in controlling these events. Further, they are one of the best studied effectors of heterotrimeric G proteins in general and Gβγ subunits in particular. However, our understanding of the roles of multiple Gβγ binding sites on Kir3 channels is still rudimentary. We discuss potential roles for Gβγ in channel assembly and trafficking in addition to their known role in cellular signaling.
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Affiliation(s)
- Peter Zylbergold
- Department of Pharmacology and Therapeutics, McGill University, Québec, Canada
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McCoy KL, Hepler JR. Regulators of G protein signaling proteins as central components of G protein-coupled receptor signaling complexes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:49-74. [PMID: 20374713 DOI: 10.1016/s1877-1173(09)86003-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The regulators of G protein signaling (RGS) proteins bind directly to G protein alpha (Gα) subunits to regulate the signaling functions of Gα and their linked G protein-coupled receptors (GPCRs). Recent studies indicate that RGS proteins also interact with GPCRs, not just G proteins, to form preferred functional pairs. Interactions between GPCRs and RGS proteins may be direct or indirect (via a linker protein) and are dictated by the receptors, rather than the linked G proteins. Emerging models suggest that GPCRs serve as platforms for assembling an overlapping and distinct constellation of signaling proteins that perform receptor-specific signaling tasks. Compelling evidence now indicates that RGS proteins are central components of these GPCR signaling complexes. This review will outline recent discoveries of GPCR/RGS pairs as well as new data in support of the idea that GPCRs serve as platforms for the formation of multiprotein signaling complexes.
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Affiliation(s)
- Kelly L McCoy
- Department of Pharmacology, G205 Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Ladds G, Zervou S, Vatish M, Thornton S, Davey J. Regulators of G protein signalling proteins in the human myometrium. Eur J Pharmacol 2009; 610:23-8. [PMID: 19318093 DOI: 10.1016/j.ejphar.2009.03.042] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 02/26/2009] [Accepted: 03/10/2009] [Indexed: 10/21/2022]
Abstract
The contractile state of the human myometrium is controlled by extracellular signals that promote relaxation or contraction. Many of these signals function through G protein-coupled receptors at the cell surface, stimulating heterotrimeric G proteins and leading to changes in the activity of effector proteins responsible for bringing about the response. G proteins can interact with multiple receptors and many different effectors and are key players in the response. Regulators of G protein signalling (RGS) proteins are GTPase activating proteins for heterotrimeric G proteins and help terminate the signal. Little is known about the function of RGS proteins in human myometrium and we have therefore analysed transcript levels for RGS proteins at various stages of pregnancy (non-pregnant, preterm, term non-labouring, term labouring). RGS2 and RGS5 were the most abundantly expressed isolates in each of the patient groups. The levels of RGS4 and RGS16 (and to a lesser extent RGS2 and RGS14) increased in term labouring samples relative to the other groups. Yeast two-hybrid analysis and co-immunoprecipitation in myometrial cells revealed that both RGS2 and RGS5 interact directly with the cytoplasmic tail of the oxytocin receptor, suggesting they might help regulate signalling through this receptor.
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Affiliation(s)
- Graham Ladds
- Clinical Sciences Research Institute, University of Warwick Medical School, UHCW Campus, Clifford Bridge Road, Coventry CV2 2DX, UK
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Smith B, Hill C, Godfrey EL, Rand D, van den Berg H, Thornton S, Hodgkin M, Davey J, Ladds G. Dual positive and negative regulation of GPCR signaling by GTP hydrolysis. Cell Signal 2009; 21:1151-60. [PMID: 19285552 DOI: 10.1016/j.cellsig.2009.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Accepted: 03/04/2009] [Indexed: 10/21/2022]
Abstract
G protein-coupled receptors (GPCRs) regulate a variety of intracellular pathways through their ability to promote the binding of GTP to heterotrimeric G proteins. Regulator of G protein signaling (RGS) proteins increases the intrinsic GTPase activity of Galpha-subunits and are widely regarded as negative regulators of G protein signaling. Using yeast we demonstrate that GTP hydrolysis is not only required for desensitization, but is essential for achieving a high maximal (saturated level) response. Thus RGS-mediated GTP hydrolysis acts as both a negative (low stimulation) and positive (high stimulation) regulator of signaling. To account for this we generated a new kinetic model of the G protein cycle where Galpha(GTP) enters an inactive GTP-bound state following effector activation. Furthermore, in vivo and in silico experimentation demonstrates that maximum signaling output first increases and then decreases with RGS concentration. This unimodal, non-monotone dependence on RGS concentration is novel. Analysis of the kinetic model has revealed a dynamic network motif that shows precisely how inclusion of the inactive GTP-bound state for the Galpha produces this unimodal relationship.
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Affiliation(s)
- Benjamin Smith
- Molecular Organization and Assembly of Cells Centre, University of Warwick, Coventry, UK
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Gilchrist A. A perspective on more effective GPCR-targeted drug discovery efforts. Expert Opin Drug Discov 2008; 3:375-89. [DOI: 10.1517/17460441.3.4.375] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
G-proteins (guanine nucleotide-binding proteins) are membrane-attached proteins composed of three subunits, alpha, beta, and gamma. They transduce signals from G-protein coupled receptors (GPCRs) to target effector proteins. The agonistactivated receptor induces a conformational change in the G-protein trimer so that the alpha-subunit binds GTP in exchange for GDP and alpha-GTP, and betagamma-subunits separate to interact with the target effector. Effector-interaction is terminated by the alpha-subunit GTPase activity, whereby bound GTP is hydrolyzed to GDP. This is accelerated in situ by RGS proteins, acting as GTPase-activating proteins (GAPs). Galpha-GDP and Gbetagamma then reassociate to form the Galphabetagamma trimer. G-proteins primarily involved in the modulation of neurotransmitter release are G(o), G(q) and G(s). G(o) mediates the widespread presynaptic auto-inhibitory effect of many neurotransmitters (e.g., via M2/M4 muscarinic receptors, alpha(2) adrenoreceptors, micro/delta opioid receptors, GABAB receptors). The G(o) betagamma-subunit acts in two ways: first, and most ubiquitously, by direct binding to CaV2 Ca(2+) channels, resulting in a reduced sensitivity to membrane depolarization and reduced Ca(2+) influx during the terminal action potential; and second, through a direct inhibitory effect on the transmitter release machinery, by binding to proteins of the SNARE complex. G(s) and G(q) are mainly responsible for receptor-mediated facilitatory effects, through activation of target enzymes (adenylate cyclase, AC and phospholipase-C, PLC respectively) by the GTP-bound alpha-subunits.
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Affiliation(s)
- David A Brown
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Bansal G, Druey KM, Xie Z. R4 RGS proteins: regulation of G-protein signaling and beyond. Pharmacol Ther 2007; 116:473-95. [PMID: 18006065 DOI: 10.1016/j.pharmthera.2007.09.005] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 09/18/2007] [Indexed: 12/21/2022]
Abstract
The regulators of G-protein signaling (RGS) proteins were initially characterized as inhibitors of signal transduction cascades initiated by G-protein-coupled receptors (GPCR) because of their ability to increase the intrinsic GTPase activity of heterotrimeric G proteins. This GTPase accelerating protein (GAP) activity enhances G protein deactivation and promotes desensitization. However, in addition to this signature trait, emerging data have revealed an expanding network of proteins, lipids, and ions that interact with RGS proteins and confer additional regulatory functions. This review highlights recent advances in our understanding of the physiological functions of one subfamily of RGS proteins with a high degree of homology (B/R4) gleaned from recent studies of knockout mice or cells with reduced RGS expression. We also discuss some of the newly appreciated interactions of RGS proteins with cellular factors that suggest RGS control of several components of G-protein-mediated pathways, as well as a diverse array of non-GPCR-mediated biological responses.
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Affiliation(s)
- Geetanjali Bansal
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, United States
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