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Dunn HA, Ferguson SSG. PDZ Protein Regulation of G Protein–Coupled Receptor Trafficking and Signaling Pathways. Mol Pharmacol 2015; 88:624-39. [DOI: 10.1124/mol.115.098509] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 03/25/2015] [Indexed: 01/03/2023] Open
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G-protein signaling modulator 1 deficiency accelerates cystic disease in an orthologous mouse model of autosomal dominant polycystic kidney disease. Proc Natl Acad Sci U S A 2012; 109:21462-7. [PMID: 23236168 DOI: 10.1073/pnas.1216830110] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Polycystic kidney diseases are the most common genetic diseases that affect the kidney. There remains a paucity of information regarding mechanisms by which G proteins are regulated in the context of polycystic kidney disease to promote abnormal epithelial cell expansion and cystogenesis. In this study, we describe a functional role for the accessory protein, G-protein signaling modulator 1 (GPSM1), also known as activator of G-protein signaling 3, to act as a modulator of cyst progression in an orthologous mouse model of autosomal dominant polycystic kidney disease (ADPKD). A complete loss of Gpsm1 in the Pkd1(V/V) mouse model of ADPKD, which displays a hypomorphic phenotype of polycystin-1, demonstrated increased cyst progression and reduced renal function compared with age-matched cystic Gpsm1(+/+) and Gpsm1(+/-) mice. Electrophysiological studies identified a role by which GPSM1 increased heteromeric polycystin-1/polycystin-2 ion channel activity via Gβγ subunits. In summary, the present study demonstrates an important role for GPSM1 in controlling the dynamics of cyst progression in an orthologous mouse model of ADPKD and presents a therapeutic target for drug development in the treatment of this costly disease.
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Gillies L, Lee SC, Long JS, Ktistakis N, Pyne NJ, Pyne S. The sphingosine 1-phosphate receptor 5 and sphingosine kinases 1 and 2 are localised in centrosomes: possible role in regulating cell division. Cell Signal 2009; 21:675-84. [PMID: 19211033 DOI: 10.1016/j.cellsig.2009.01.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 01/03/2009] [Accepted: 01/04/2009] [Indexed: 11/16/2022]
Abstract
We show here that the endogenous sphingosine 1-phosphate 5 receptor (S1P(5), a G protein coupled receptor (GPCR) whose natural ligand is sphingosine 1-phosphate (S1P)) and sphingosine kinases 1 and 2 (SK1 and SK2), which catalyse formation of S1P, are co-localised in the centrosome of mammalian cells, where they may participate in regulating mitosis. The centrosome is a site for active GTP-GDP cycling involving the G-protein, G(i) and tubulin, which are required for spindle pole organization and force generation during cell division. Therefore, the presence of S1P(5) (which normally functions as a plasma membrane guanine nucleotide exchange factor, GEF) and sphingosine kinases in the centrosome might suggest that S1P(5) may function as a ligand activated GEF in regulating G-protein-dependent spindle formation and mitosis. The addition of S1P to cells inhibits trafficking of S1P(5) to the centrosome, suggesting a dynamic shuttling endocytic mechanism controlled by ligand occupancy of cell surface receptor. We therefore propose that the centrosomal S1P(5) receptor might function as an intracellular target of S1P linked to regulation of mitosis.
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Affiliation(s)
- Laura Gillies
- Cell Biology Group, SIPBS, University of Strathclyde, 27 Taylor St, Glasgow, G4 0NR, UK
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Retinal ON bipolar cells express a new PCP2 splice variant that accelerates the light response. J Neurosci 2008; 28:8873-84. [PMID: 18768681 DOI: 10.1523/jneurosci.0812-08.2008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
PCP2, a member of the GoLoco domain-containing family, is present exclusively in cerebellar Purkinje cells and retinal ON bipolar cells. Its function in these tissues is unknown. Biochemical and expression system studies suggest that PCP2 is a guanine nucleotide dissociation inhibitor, although a guanine nucleotide exchange factor has also been suggested. Here, we studied the function of PCP2 in ON bipolar cells because their light response depends on Galpha(o1), which is known to interact with PCP2. We identified a new splice variant of PCP2 (Ret-PCP2) and localized it to rod bipolar and ON cone bipolar cells. Electroretinogram recordings from PCP2-null mice showed a normal a-wave but a slower falling phase of the b-wave (generated by the activity of ON bipolar cells) relative to the wild type. Whole-cell recordings from rod bipolar cells showed, both under Ames medium and after blocking GABA(A/C) and glycine receptors, that PCP2-null rod bipolar cells were more depolarized than wild-type cells with greater inward current when clamped to -60 mV. Also under both conditions, the rise time of the response to intense light was slower by 28% (Ames) and 44% (inhibitory blockers) in the null cells. Under Ames medium, we also observed >30% longer decay time in the PCP2-null rod bipolar cells. We conclude that PCP2 facilitates cation channels closure in the dark, shortens the rise time of the light response directly, and accelerates the decay time indirectly via the inhibitory network. These data can most easily be explained if PCP2 serves as a guanine nucleotide exchange factor.
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Millward SW, Fiacco S, Austin RJ, Roberts RW. Design of cyclic peptides that bind protein surfaces with antibody-like affinity. ACS Chem Biol 2007; 2:625-34. [PMID: 17894440 PMCID: PMC3747972 DOI: 10.1021/cb7001126] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There is a pressing need for new molecular tools to target protein surfaces with high affinity and specificity. Here, we describe cyclic messenger RNA display with a trillion-member covalent peptide macrocycle library. Using this library, we have designed a number of high-affinity, redox-insensitive, cyclic peptides that target the signaling protein G alpha i1. In addition to cyclization, our library construction took advantage of an expanded genetic code, utilizing nonsense suppression to insert N-methylphenylalanine as a 21st amino acid. The designed macrocycles exhibit several intriguing features. First, the core motif seen in all of the selected variants is the same and shares an identical context with respect to the macrocyclic scaffold, consistent with the idea that selection simultaneously optimizes both the cyclization chemistry and the structural placement of the binding epitope. Second, detailed characterization of one molecule, cyclic G alpha i binding peptide (cycGiBP), demonstrates substantially enhanced proteolytic stability relative to that of the parent linear molecule. Third and perhaps most important, the cycGiBP peptide binds the target with very high affinity ( K i approximately 2.1 nM), similar to those of many of the best monoclonal antibodies and higher than that of the betagamma heterodimer, an endogenous G alpha i1 ligand. Overall the work provides a general route to design novel, low-molecular-weight, high-affinity ligands that target protein surfaces.
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Affiliation(s)
- Steven W. Millward
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
| | - Stephen Fiacco
- Department of Chemistry, Chemical Engineering, and Biology, University of Southern California, 3710 McClintock Avenue, Los Angeles, California 90089-1211
| | - Ryan J. Austin
- Department of Chemistry, Chemical Engineering, and Biology, University of Southern California, 3710 McClintock Avenue, Los Angeles, California 90089-1211
| | - Richard W. Roberts
- Department of Chemistry, Chemical Engineering, and Biology, University of Southern California, 3710 McClintock Avenue, Los Angeles, California 90089-1211
- Corresponding author,
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Xie GX, Palmer PP. How regulators of G protein signaling achieve selective regulation. J Mol Biol 2006; 366:349-65. [PMID: 17173929 PMCID: PMC1805491 DOI: 10.1016/j.jmb.2006.11.045] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/02/2006] [Accepted: 11/10/2006] [Indexed: 11/30/2022]
Abstract
The regulators of G protein signaling (RGS) are a family of cellular proteins that play an essential regulatory role in G protein-mediated signal transduction. There are multiple RGS subfamilies consisting of over 20 different RGS proteins. They are basically the guanosine triphosphatase (GTPase)-accelerating proteins that specifically interact with G protein alpha subunits. RGS proteins display remarkable selectivity and specificity in their regulation of receptors, ion channels, and other G protein-mediated physiological events. The molecular and cellular mechanisms underlying such selectivity are complex and cooperate at many different levels. Recent research data have provided strong evidence that the spatiotemporal-specific expression of RGS proteins and their target components, as well as the specific protein-protein recognition and interaction through their characteristic structural domains and functional motifs, are determinants for RGS selectivity and specificity. Other molecular mechanisms, such as alternative splicing and scaffold proteins, also significantly contribute to RGS selectivity. To pursue a thorough understanding of the mechanisms of RGS selective regulation will be of great significance for the advancement of our knowledge of molecular and cellular signal transduction.
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Affiliation(s)
| | - Pamela Pierce Palmer
- *Corresponding author: Pamela Pierce Palmer, M.D., Ph.D., University of California, San Francisco, Department of Anesthesia and Perioperative Care, 513 Parnassus Avenue, Box 0464, Room S-455, San Francisco, California 94143, USA, Telephone: (415)476-6783, FAX: (415)502-5375, E-mail:
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Siderovski DP, Willard FS. The GAPs, GEFs, and GDIs of heterotrimeric G-protein alpha subunits. Int J Biol Sci 2005; 1:51-66. [PMID: 15951850 PMCID: PMC1142213 DOI: 10.7150/ijbs.1.51] [Citation(s) in RCA: 317] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 02/01/2005] [Indexed: 12/21/2022] Open
Abstract
The heterotrimeric G-protein alpha subunit has long been considered a bimodal, GTP-hydrolyzing switch controlling the duration of signal transduction by seven-transmembrane domain (7TM) cell-surface receptors. In 1996, we and others identified a superfamily of “regulator of G-protein signaling” (RGS) proteins that accelerate the rate of GTP hydrolysis by Gα subunits (dubbed GTPase-accelerating protein or “GAP” activity). This discovery resolved the paradox between the rapid physiological timing seen for 7TM receptor signal transduction in vivo and the slow rates of GTP hydrolysis exhibited by purified Gα subunits in vitro. Here, we review more recent discoveries that have highlighted newly-appreciated roles for RGS proteins beyond mere negative regulators of 7TM signaling. These new roles include the RGS-box-containing, RhoA-specific guanine nucleotide exchange factors (RGS-RhoGEFs) that serve as Gα effectors to couple 7TM and semaphorin receptor signaling to RhoA activation, the potential for RGS12 to serve as a nexus for signaling from tyrosine kinases and G-proteins of both the Gα and Ras-superfamilies, the potential for R7-subfamily RGS proteins to couple Gα subunits to 7TM receptors in the absence of conventional Gβγ dimers, and the potential for the conjoint 7TM/RGS-box Arabidopsis protein AtRGS1 to serve as a ligand-operated GAP for the plant Gα AtGPA1. Moreover, we review the discovery of novel biochemical activities that also impinge on the guanine nucleotide binding and hydrolysis cycle of Gα subunits: namely, the guanine nucleotide dissociation inhibitor (GDI) activity of the GoLoco motif-containing proteins and the 7TM receptor-independent guanine nucleotide exchange factor (GEF) activity of Ric‑8/synembryn. Discovery of these novel GAP, GDI, and GEF activities have helped to illuminate a new role for Gα subunit GDP/GTP cycling required for microtubule force generation and mitotic spindle function in chromosomal segregation.
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Affiliation(s)
- David P Siderovski
- Department of Pharmacology, UNC Lineberger Comprehensive Cancer Center, and UNC Neuroscience Center, The University of North Carolina at Chapel Hill, CB#7365, 1106 M.E. Jones Building, Chapel Hill, NC 27599-7365 USA.
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Kimple RJ, Willard FS, Siderovski DP. Purification and in vitro functional analyses of RGS12 and RGS14 GoLoco motif peptides. Methods Enzymol 2005; 390:416-36. [PMID: 15488192 DOI: 10.1016/s0076-6879(04)90026-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
The GoLoco motif is a short polypeptide sequence that binds to heterotrimeric G-protein alpha subunits of the adenylyl cyclase-inhibitory (Galpha(i/o)) subclass in a nucleotide-dependent manner (i.e., solely to the GDP-bound ground state). This article describes methods used for the expression, purification, and in vitro evaluation of membrane-permeant tag fusion peptides derived from the GoLoco motif regions of "regulator of G-protein signaling" proteins type 12 (RGS12) and 14 (RGS14) and a consensus GoLoco sequence from the multiple GoLoco motif protein AGS3. Three different fluorescence-based assays are described for evaluating the in vitro function of these GoLoco peptides as guanine nucleotide dissociation inhibitors, including measurements of GTPgammaS binding and Galpha subunit activation by the planar ion aluminum tetrafluoride.
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Affiliation(s)
- Randall J Kimple
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, The University of North Carolina, Chapel Hill 27599, USA
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Mergler S, Strauss O, Strowski M, Prada J, Drost A, Langrehr J, Neuhaus P, Wiedenmann B, Ploeckinger U. Insulin-like growth factor-1 increases intracellular calcium concentration in human primary neuroendocrine pancreatic tumor cells and a pancreatic neuroendocrine tumor cell line (BON-1) via R-type Ca2+ channels and regulates chromogranin a secretion in BON-1 cells. Neuroendocrinology 2005; 82:87-102. [PMID: 16424676 DOI: 10.1159/000091008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Accepted: 10/28/2005] [Indexed: 12/17/2022]
Abstract
Insulin-like growth factor 1 (IGF-1) is a potent mitogenic and secretory factor that acts on voltage operated Ca(2+) channels (VOCCs). VOCCs are categorized into L-type channels (Ca(V)1.1-1.4), P/Q-type channels (Ca(V)2.1), N-type channels (Ca(V)2.2), R-type channels (Ca(V)2.3), and T-type channels (Ca(V)3.1-3.3). Aside from regulating membrane excitability, VOCCs influence chromogranin A (CgA) secretion in neuroendocrine tumor (NET) cells. It is not known, whether VOCCs play a role in the IGF-1-dependent regulation of CgA secretion in NET cells. We therefore studied the effects of IGF-1 on individual VOCC subtypes and characterized their role in mediating IGF-1-dependent regulation of CgA secretion in NET cells. Using specific modulators of VOCC subtypes, we identified the functional expression of L-, N-, P/Q- and R-type channels in primary as well as permanent models of NET. The IGF-1-induced intracellular Ca(2+) increase in NET cells was mainly due to the activation of R-type channel activity. The effects on intracellular calcium, observed in whole-cell patch-clamp recordings and fluorescence imaging, were partially blocked by the specific R-type channel blocker SNX-482 and antisense oligonucleotides against the alpha(1) subunit of this channel. IGF-1 potently induced CgA secretion. The effect of IGF-1 was reduced by both, inhibition of R-type channel activity and a reduction of R-type channel expression using antisense oligonucleotides. Since R-type channels exist in NET cells and couple to both, IGF-1 receptor signaling as well as CgA secretion, pharmacological interference with R-type channels may represent a new therapeutic option by blocking Ca(2+) signaling thereby abrogating IGF-1-dependent hypersecretion in NET disease.
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Affiliation(s)
- Stefan Mergler
- Medizinische Klinik mit Schwerpunkt Hepatologie und Gastroenterologie, Interdisziplinares Stoffwechsel-Centrum: Endokrinologie, Diabetes und Stoffwechsel, Charité-Universitatsmedizin Berlin, Germany.
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Afshar K, Willard FS, Colombo K, Johnston CA, McCudden CR, Siderovski DP, Gönczy P. RIC-8 is required for GPR-1/2-dependent Galpha function during asymmetric division of C. elegans embryos. Cell 2004; 119:219-30. [PMID: 15479639 DOI: 10.1016/j.cell.2004.09.026] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Revised: 09/15/2004] [Accepted: 09/16/2004] [Indexed: 10/26/2022]
Abstract
Heterotrimeric G proteins are crucial for asymmetric cell division, but the mechanisms of signal activation remain poorly understood. Here, we establish that the evolutionarily conserved protein RIC-8 is required for proper asymmetric division of one-cell stage C. elegans embryos. Spindle severing experiments demonstrate that RIC-8 is required for generation of substantial pulling forces on astral microtubules. RIC-8 physically interacts with GOA-1 and GPA-16, two Galpha subunits that act in a partially redundant manner in one-cell stage embryos. RIC-8 preferentially binds to GDP bound GOA-1 and is a guanine nucleotide exchange factor (GEF) for GOA-1. Our analysis suggests that RIC-8 acts before the GoLoco protein GPR-1/2 in the sequence of events leading to Galpha activation. Furthermore, coimmunoprecipitation and in vivo epistasis demonstrate that inactivation of the Gbeta subunit GPB-1 alleviates the need for RIC-8 in one-cell stage embryos. Our findings suggest a mechanism in which RIC-8 favors generation of Galpha free from Gbetagamma and enables GPR-1/2 to mediate asymmetric cell division.
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Affiliation(s)
- Katayoun Afshar
- Swiss Institute for Experimental Cancer Research (ISREC), 1066 Epalinges/Lausanne, Switzerland
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Hains MD, Siderovski DP, Harden TK. Application of RGS box proteins to evaluate G-protein selectivity in receptor-promoted signaling. Methods Enzymol 2004; 389:71-88. [PMID: 15313560 DOI: 10.1016/s0076-6879(04)89005-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Regulator of G-protein signaling (RGS) domains bind directly to GTP-bound Galpha subunits and accelerate their intrinsic GTPase activity by up to several thousandfold. The selectivity of RGS proteins for individual Galpha subunits has been illustrated. Thus, the expression of RGS proteins can be used to inhibit signaling pathways activated by specific G protein-coupled receptors (GPCRs). This article describes the use of specific RGS domain constructs to discriminate among G(i/o), Gq-and G(12/13)-mediated activation of phospholipase C (PLC) isozymes in COS-7 cells. Overexpression of the N terminus of GRK2 (amino acids 45-178) or p115 RhoGEF (amino acids 1-240) elicited selective inhibition of Galphaq- or Galpha(12/13)-mediated signaling to PLC activation, respectively. In contrast, RGS2 overexpression was found to inhibit PLC activation by both G(i/o)- and Gq-coupled GPCRs. RGS4 exhibited dramatic receptor selectivity in its inhibitory actions; of the G(i/o)- and Gq-coupled GPCRs tested (LPA1, LPA2, P2Y1, S1P3), only the Gq-coupled lysophosphatidic acid-activated LPA2 receptor was found to be inhibited by RGS4 overexpression.
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Affiliation(s)
- Melinda D Hains
- Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill 27599, USA
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