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Montañez-Miranda C, Perszyk RE, Harbin NH, Okalova J, Ramineni S, Traynelis SF, Hepler JR. Functional Assessment of Cancer-Linked Mutations in Sensitive Regions of Regulators of G Protein Signaling Predicted by Three-Dimensional Missense Tolerance Ratio Analysis. Mol Pharmacol 2023; 103:21-37. [PMID: 36384958 PMCID: PMC10955721 DOI: 10.1124/molpharm.122.000614] [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: 08/16/2022] [Revised: 10/04/2022] [Accepted: 10/18/2022] [Indexed: 11/18/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling by acting as negative regulators of G proteins. Genetic variants in RGS proteins are associated with many diseases, including cancers, although the impact of these mutations on protein function is uncertain. Here we analyze the RGS domains of 15 RGS protein family members using a novel bioinformatic tool that measures the missense tolerance ratio (MTR) using a three-dimensional (3D) structure (3DMTR). Subsequent permutation analysis can define the protein regions that are most significantly intolerant (P < 0.05) in each dataset. We further focused on RGS14, RGS10, and RGS4. RGS14 exhibited seven significantly tolerant and seven significantly intolerant residues, RGS10 had six intolerant residues, and RGS4 had eight tolerant and six intolerant residues. Intolerant and tolerant-control residues that overlap with pathogenic cancer mutations reported in the COSMIC cancer database were selected to define the functional phenotype. Using complimentary cellular and biochemical approaches, proteins were tested for effects on GPCR-Gα activation, Gα binding properties, and downstream cAMP levels. Identified intolerant residues with reported cancer-linked mutations RGS14-R173C/H and RGS4-K125Q/E126K, and tolerant RGS14-S127P and RGS10-S64T resulted in a loss-of-function phenotype in GPCR-G protein signaling activity. In downstream cAMP measurement, tolerant RGS14-D137Y and RGS10-S64T and intolerant RGS10-K89M resulted in change of function phenotypes. These findings show that 3DMTR identified intolerant residues that overlap with cancer-linked mutations cause phenotypic changes that negatively impact GPCR-G protein signaling and suggests that 3DMTR is a potentially useful bioinformatics tool for predicting functionally important protein residues. SIGNIFICANCE STATEMENT: Human genetic variant/mutation information has expanded rapidly in recent years, including cancer-linked mutations in regulator of G protein signaling (RGS) proteins. However, experimental testing of the impact of this vast catalogue of mutations on protein function is not feasible. We used the novel bioinformatics tool three-dimensional missense tolerance ratio (3DMTR) to define regions of genetic intolerance in RGS proteins and prioritize which cancer-linked mutants to test. We found that 3DMTR more accurately classifies loss-of-function mutations in RGS proteins than other databases thereby offering a valuable new research tool.
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Affiliation(s)
- Carolina Montañez-Miranda
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Riley E Perszyk
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Nicholas H Harbin
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Jennifer Okalova
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Suneela Ramineni
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Stephen F Traynelis
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
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Wang D, Dao M, Muntean BS, Giles AC, Martemyanov KA, Grill B. Genetic modeling of GNAO1 disorder delineates mechanisms of Gαo dysfunction. Hum Mol Genet 2021; 31:510-522. [PMID: 34508586 PMCID: PMC8863422 DOI: 10.1093/hmg/ddab235] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/30/2021] [Accepted: 08/09/2021] [Indexed: 12/26/2022] Open
Abstract
GNAO1 encephalopathy is a neurodevelopmental disorder with a spectrum of symptoms that include dystonic movements, seizures and developmental delay. While numerous GNAO1 mutations are associated with this disorder, the functional consequences of pathological variants are not completely understood. Here, we deployed the invertebrate C. elegans as a whole-animal behavioral model to study the functional effects of GNAO1 disorder-associated mutations. We tested several pathological GNAO1 mutations for effects on locomotor behaviors using a combination of CRISPR/Cas9 gene editing and transgenic overexpression in vivo. We report that all three mutations tested (G42R, G203R and R209C) result in strong loss of function defects when evaluated as homozygous CRISPR alleles. In addition, mutations produced dominant negative effects assessed using both heterozygous CRISPR alleles and transgenic overexpression. Experiments in mice confirmed dominant negative effects of GNAO1 G42R, which impaired numerous motor behaviors. Thus, GNAO1 pathological mutations result in conserved functional outcomes across animal models. Our study further establishes the molecular genetic basis of GNAO1 encephalopathy, and develops a CRISPR-based pipeline for functionally evaluating mutations associated with neurodevelopmental disorders.
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Affiliation(s)
- Dandan Wang
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Maria Dao
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Brian S Muntean
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Andrew C Giles
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA.,Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA.,Department of Pharmacology, University of Washington School of Medicine, Seattle, WA, USA
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Bouchet CA, McPherson KB, Li MH, Traynor JR, Ingram SL. Mice Expressing Regulators of G protein Signaling-insensitive Gαo Define Roles of μ Opioid Receptor G αo and G αi Subunit Coupling in Inhibition of Presynaptic GABA Release. Mol Pharmacol 2021; 100:217-223. [PMID: 34135098 DOI: 10.1124/molpharm.121.000249] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 06/04/2021] [Indexed: 11/22/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate signaling by G protein-coupled receptors. Using a knock-in transgenic mouse model with a mutation in Gαo that does not bind RGS proteins (RGS-insensitive), we determined the effect of RGS proteins on presynaptic μ opioid receptor (MOR)-mediated inhibition of GABA release in the ventrolateral periaqueductal gray (vlPAG). The MOR agonists [d-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) and met-enkephalin (ME) inhibited evoked inhibitory postsynaptic currents (eIPSCs) in the RGS-insensitive mice compared with wild-type (WT) littermates, respectively. Fentanyl inhibited eIPSCs similarly in both WT and RGS-insensitive mice. There were no differences in opioid agonist inhibition of spontaneous GABA release between the genotypes. To further probe the mechanism underlying these differences between opioid inhibition of evoked and spontaneous GABA release, specific myristoylated Gα peptide inhibitors for Gαo1 and Gαi1-3 that block receptor-G protein interactions were used to test the preference of agonists for MOR-Gα complexes. The Gαo1 inhibitor reduced DAMGO inhibition of eIPSCs, but Gαi1-3 inhibitors had no effect. Both Gαo1 and Gαi1-3 inhibitors separately reduced fentanyl inhibition of eIPSCs but had no effects on ME inhibition. Gαi1-3 inhibitors blocked the inhibitory effects of ME and fentanyl on miniature postsynaptic current (mIPSC) frequency, but both Gαo1 and Gαi1-3 inhibitors were needed to block the effects of DAMGO. Finally, baclofen-mediated inhibition of GABA release is unaffected in the RGS-insensitive mice and in the presence of Gαo1 and Gαi1-3 inhibitor peptides, suggesting that GABAB receptor coupling to G proteins in vlPAG presynaptic terminals is different than MOR coupling. SIGNIFICANCE STATEMENT: Presynaptic μ opioid receptors (MORs) in the ventrolateral periaqueductal gray are critical for opioid analgesia and are negatively regulated by RGS proteins. These data in RGS-insensitive mice provide evidence that MOR agonists differ in preference for Gαo versus Gαi and regulation by RGS proteins in presynaptic terminals, providing a mechanism for functional selectivity between agonists. The results further define important differences in MOR and GABAB receptor coupling to G proteins that could be exploited for new pain therapies.
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Affiliation(s)
- Courtney A Bouchet
- Department of Neurologic Surgery, Oregon Health & Science University, Portland, Oregon (C.A.B., K.B.M., M.L., S.L.I.); and Department of Pharmacology and Edward F. Domino Research Center, Medical School, Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan (J.R.T.)
| | - Kylie B McPherson
- Department of Neurologic Surgery, Oregon Health & Science University, Portland, Oregon (C.A.B., K.B.M., M.L., S.L.I.); and Department of Pharmacology and Edward F. Domino Research Center, Medical School, Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan (J.R.T.)
| | - Ming-Hua Li
- Department of Neurologic Surgery, Oregon Health & Science University, Portland, Oregon (C.A.B., K.B.M., M.L., S.L.I.); and Department of Pharmacology and Edward F. Domino Research Center, Medical School, Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan (J.R.T.)
| | - John R Traynor
- Department of Neurologic Surgery, Oregon Health & Science University, Portland, Oregon (C.A.B., K.B.M., M.L., S.L.I.); and Department of Pharmacology and Edward F. Domino Research Center, Medical School, Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan (J.R.T.)
| | - Susan L Ingram
- Department of Neurologic Surgery, Oregon Health & Science University, Portland, Oregon (C.A.B., K.B.M., M.L., S.L.I.); and Department of Pharmacology and Edward F. Domino Research Center, Medical School, Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan (J.R.T.)
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Constantinof A, Boureau L, Moisiadis VG, Kostaki A, Szyf M, Matthews SG. Prenatal Glucocorticoid Exposure Results in Changes in Gene Transcription and DNA Methylation in the Female Juvenile Guinea Pig Hippocampus Across Three Generations. Sci Rep 2019; 9:18211. [PMID: 31796763 PMCID: PMC6890750 DOI: 10.1038/s41598-019-54456-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 11/13/2019] [Indexed: 01/01/2023] Open
Abstract
Synthetic glucocorticoids (sGC) are administered to women at risk for pre-term delivery, to mature the fetal lung and decrease neonatal morbidity. sGC also profoundly affect the fetal brain. The hippocampus expresses high levels of glucocorticoid (GR) and mineralocorticoid receptor (MR), and its development is affected by elevated fetal glucocorticoid levels. Antenatal sGC results in neuroendocrine and behavioral changes that persist in three generations of female guinea pig offspring of the paternal lineage. We hypothesized that antenatal sGC results in transgenerational changes in gene expression that correlate with changes in DNA methylation. We used RNASeq and capture probe bisulfite sequencing to investigate the transcriptomic and epigenomic effects of antenatal sGC exposure in the hippocampus of three generations of juvenile female offspring from the paternal lineage. Antenatal sGC exposure (F0 pregnancy) resulted in generation-specific changes in hippocampal gene transcription and DNA methylation. Significant changes in individual CpG methylation occurred in RNApol II binding regions of small non-coding RNA (snRNA) genes, which implicates alternative splicing as a mechanism involved in transgenerational transmission of the effects of antenatal sGC. This study provides novel perspectives on the mechanisms involved in transgenerational transmission and highlights the importance of human studies to determine the longer-term effects of antenatal sGC on hippocampal-related function.
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Affiliation(s)
- Andrea Constantinof
- Department of Physiology, University of Toronto, Toronto, ON, M5S1A8, Canada
| | - Lisa Boureau
- Department of Pharmacology & Therapeutics, Sackler Program for Epigenetics & Psychobiology, McGill University, Montreal, QC, H3G1Y6, Canada
| | - Vasilis G Moisiadis
- Department of Physiology, University of Toronto, Toronto, ON, M5S1A8, Canada
| | - Alisa Kostaki
- Department of Physiology, University of Toronto, Toronto, ON, M5S1A8, Canada
| | - Moshe Szyf
- Department of Pharmacology & Therapeutics, Sackler Program for Epigenetics & Psychobiology, McGill University, Montreal, QC, H3G1Y6, Canada
| | - Stephen G Matthews
- Department of Physiology, University of Toronto, Toronto, ON, M5S1A8, Canada.
- Department of Obstetrics and Gynecology, Toronto, Canada.
- Department of Medicine, University of Toronto, Toronto, ON, M5S1A8, Canada.
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, M5G1X5, Canada.
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Feng H, Larrivee CL, Demireva EY, Xie H, Leipprandt JR, Neubig RR. Mouse models of GNAO1-associated movement disorder: Allele- and sex-specific differences in phenotypes. PLoS One 2019; 14:e0211066. [PMID: 30682176 PMCID: PMC6347370 DOI: 10.1371/journal.pone.0211066] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 01/07/2019] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Infants and children with dominant de novo mutations in GNAO1 exhibit movement disorders, epilepsy, or both. Children with loss-of-function (LOF) mutations exhibit Epileptiform Encephalopathy 17 (EIEE17). Gain-of-function (GOF) mutations or those with normal function are found in patients with Neurodevelopmental Disorder with Involuntary Movements (NEDIM). There is no animal model with a human mutant GNAO1 allele. OBJECTIVES Here we develop a mouse model carrying a human GNAO1 mutation (G203R) and determine whether the clinical features of patients with this GNAO1 mutation, which includes both epilepsy and movement disorder, would be evident in the mouse model. METHODS A mouse Gnao1 knock-in GOF mutation (G203R) was created by CRISPR/Cas9 methods. The resulting offspring and littermate controls were subjected to a battery of behavioral tests. A previously reported GOF mutant mouse knock-in (Gnao1+/G184S), which has not been found in patients, was also studied for comparison. RESULTS Gnao1+/G203R mutant mice are viable and gain weight comparably to controls. Homozygotes are non-viable. Grip strength was decreased in both males and females. Male Gnao1+/G203R mice were strongly affected in movement assays (RotaRod and DigiGait) while females were not. Male Gnao1+/G203R mice also showed enhanced seizure propensity in the pentylenetetrazole kindling test. Mice with a G184S GOF knock-in also showed movement-related behavioral phenotypes but females were more strongly affected than males. CONCLUSIONS Gnao1+/G203R mice phenocopy children with heterozygous GNAO1 G203R mutations, showing both movement disorder and a relatively mild epilepsy pattern. This mouse model should be useful in mechanistic and preclinical studies of GNAO1-related movement disorders.
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Affiliation(s)
- Huijie Feng
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, United States of America
| | - Casandra L. Larrivee
- College of Veterinary Medicine, Michigan State University, East Lansing, MI, United States of America
| | - Elena Y. Demireva
- Transgenic and Genome Editing Facility, Michigan State University, East Lansing, MI, United States of America
| | - Huirong Xie
- Transgenic and Genome Editing Facility, Michigan State University, East Lansing, MI, United States of America
| | - Jeff R. Leipprandt
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, United States of America
| | - Richard R. Neubig
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, United States of America
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Role of hippocampal 5-HT1A receptors in the antidepressant-like phenotype of mice expressing RGS-insensitive Gαi2 protein. Neuropharmacology 2018; 141:296-304. [PMID: 30189184 DOI: 10.1016/j.neuropharm.2018.09.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/31/2018] [Accepted: 09/02/2018] [Indexed: 12/11/2022]
Abstract
A single base mutation in the Gαi2 protein (G184S) renders this Gα subunit insensitive to the negative modulatory effects of Regulator of G-protein Signaling (RGS) proteins. Mice expressing this RGS insensitive (RGSi) variant of Gαi2 (RGSi Gαi2) display a spontaneous antidepressant-like phenotype that is reversible by treatment with the 5-HT1A receptor (5-HT1AR) antagonist WAY100635. Here we test the hypothesis that increased activity of 5-HT1ARs in the hippocampus of RGSi Gαi2 knock-in mice is responsible for the expression of the observed antidepressant-like behavior. We administered the 5-HT1AR antagonist WAY100635 or the agonist 8-OH-DPAT via bilateral intra-hippocampal infusion cannulae and evaluated antidepressant-like behavior using the tail suspension test (TST). WAY100635 reversed the antidepressant-like phenotype of the RGSi Gαi2 knock-in mice and 8-OH-DPAT produced an antidepressant-like response in wild type mice that was blocked by systemic WAY100635. Furthermore, intra-hippocampal infusion of the RGS19/4 inhibitor CCG-203769 produced an antidepressant-like effect in female mice. Ex-vivo slice recording confirmed the 5-HT1AR-mediated decrease in hippocampal CA1 pyramidal neuron excitability was enhanced in the RGSi Gαi2 knock-in mice. There was no change in hippocampal 5-HT1AR expression as measured by ligand binding but there was a compensatory reduction in Gαi proteins. The findings demonstrate that RGS protein control of hippocampal 5-HT1AR signaling is necessary and sufficient to account for the antidepressant-like phenotype in the RGSi Gαi2 knock-in mice and that RGS proteins highly expressed in the hippocampus should be investigated as targets for novel antidepressant therapies.
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Regulators of G-Protein Signaling (RGS) Proteins Promote Receptor Coupling to G-Protein-Coupled Inwardly Rectifying Potassium (GIRK) Channels. J Neurosci 2018; 38:8737-8744. [PMID: 30150362 DOI: 10.1523/jneurosci.0516-18.2018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/31/2018] [Accepted: 08/20/2018] [Indexed: 01/01/2023] Open
Abstract
Regulators of G-protein signaling (RGS) proteins negatively modulate presynaptic μ-opioid receptor inhibition of GABA release in the ventrolateral periaqueductal gray (vlPAG). Paradoxically, we find that G-protein-coupled receptor (GPCR) activation of G-protein-gated inwardly rectifying K+ channels (GIRKs) in the vlPAG is reduced in an agonist- and receptor-dependent manner in transgenic knock-in mice of either sex expressing mutant RGS-insensitive Gαo proteins. μ-Opioid receptor agonist activation of GIRK currents was reduced for DAMGO and fentanyl but not for [Met5]-enkephalin acetate salt hydrate (ME) in the RGS-insensitive heterozygous (Het) mice compared with wild-type mice. The GABAB agonist baclofen-induced GIRK currents were also reduced in the Het mice. We confirmed the role of Gαo proteins in μ-opioid receptor and GABAB receptor signaling pathways in wild-type mice using myristoylated peptide inhibitors of Gαo1 and Gαi1-3 The results using these inhibitors indicate that receptor activation of GIRK channels is dependent on the preference of the agonist-stimulated receptor for Gαo versus that for Gαi. DAMGO and fentanyl-mediated GIRK currents were reduced in the presence of the Gαo1 inhibitor, but not the Gαi1-3 inhibitors. In contrast, the Gαo1 peptide inhibitor did not affect ME activation of GIRK currents, which is consistent with results in the Het mice, but the Gαi1-3 inhibitors significantly reduced ME-mediated GIRK currents. Finally, the reduction in GIRK activation in the Het mice plays a role in opioid- and baclofen-mediated spinal antinociception, but not supraspinal antinociception. Thus, our studies indicate that RGS proteins have multiple mechanisms of modulating GPCR signaling that produce negative and positive regulation of signaling depending on the effector.SIGNIFICANCE STATEMENT Regulators of G-protein signaling (RGS) proteins positively modulate GPCR coupling to GIRKs, and this coupling is critical for opioid- and baclofen-mediated spinal antinociception, whereas μ-opioid receptor-mediated supraspinal antinociception depends on presynaptic inhibition that is negatively regulated by RGS proteins. The identification of these opposite roles for RGS proteins has implications for signaling via other GPCRs.
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Dripps IJ, Boyer BT, Neubig RR, Rice KC, Traynor JR, Jutkiewicz EM. Role of signalling molecules in behaviours mediated by the δ opioid receptor agonist SNC80. Br J Pharmacol 2018; 175:891-901. [PMID: 29278419 DOI: 10.1111/bph.14131] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 11/08/2017] [Accepted: 11/30/2017] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE GPCRs exist in multiple conformations that can engage distinct signalling mechanisms which in turn may lead to diverse behavioural outputs. In rodent models, activation of the δ opioid receptor (δ-receptor) has been shown to elicit antihyperalgesia, antidepressant-like effects and convulsions. We recently showed that these δ-receptor-mediated behaviours are differentially regulated by the GTPase-activating protein regulator of G protein signalling 4 (RGS4), which facilitates termination of G protein signalling. To further evaluate the signalling mechanisms underlying δ-receptor-mediated antihyperalgesia, antidepressant-like effects and convulsions, we observed how changes in Gαo or arrestin proteins in vivo affected behaviours elicited by the δ-receptor agonist SNC80 in mice. EXPERIMENTAL APPROACH Transgenic mice with altered expression of various signalling molecules were used in the current studies. Antihyperalgesia was measured in a nitroglycerin-induced thermal hyperalgesia assay. Antidepressant-like effects were evaluated in the forced swim test. Mice were also observed for convulsive activity following SNC80 treatment. KEY RESULTS In Gαo RGS-insensitive heterozygous knock-in mice, the potency of SNC80 to produce antihyperalgesia and antidepressant-like effects was enhanced with no change in SNC80-induced convulsions. Conversely, in Gαo heterozygous knockout mice, SNC80-induced antihyperalgesia was abolished while antidepressant-like effects and convulsions were unaltered. No changes in SNC80-induced behaviours were observed in arrestin 3 knockout mice. SNC80-induced convulsions were potentiated in arrestin 2 knockout mice. CONCLUSIONS AND IMPLICATIONS Taken together, these findings suggest that different signalling molecules may underlie the convulsive effects of the δ-receptor relative to its antihyperalgesic and antidepressant-like effects.
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Affiliation(s)
- Isaac J Dripps
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Brett T Boyer
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Richard R Neubig
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
| | - Kenner C Rice
- Drug Design and Synthesis Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, North Bethesda, MD, USA
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Emily M Jutkiewicz
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
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Feng H, Sjögren B, Karaj B, Shaw V, Gezer A, Neubig RR. Movement disorder in GNAO1 encephalopathy associated with gain-of-function mutations. Neurology 2017; 89:762-770. [PMID: 28747448 DOI: 10.1212/wnl.0000000000004262] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 04/17/2017] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To define molecular mechanisms underlying the clinical spectrum of epilepsy and movement disorder in individuals with de novo mutations in the GNAO1 gene. METHODS We identified all GNAO1 mutations reported in individuals with epilepsy (early infantile epileptiform encephalopathy 17) or movement disorders through April 2016; 15 de novo mutant alleles from 25 individuals were introduced into the Gαo subunit by site-directed mutagenesis in a mammalian expression plasmid. We assessed protein expression and function in vitro in HEK-293T cells by Western blot and determined functional Gαo-dependent cyclic adenosine monophosphate (cAMP) inhibition with a coexpressed α2A adrenergic receptor. RESULTS Of the 15 clinical GNAO1 mutations studied, 9 show reduced expression and loss of function (LOF; <90% maximal inhibition). Six other mutations show variable levels of expression but exhibit normal or even gain-of-function (GOF) behavior, as demonstrated by significantly lower EC50 values for α2A adrenergic receptor-mediated inhibition of cAMP. The GNAO1 LOF mutations are associated with epileptic encephalopathy while GOF mutants (such as G42R, G203R, and E246K) or normally functioning mutants (R209) were found in patients with movement disorders with or without seizures. CONCLUSIONS Both LOF and GOF mutations in Gαo (encoded by GNAO1) are associated with neurologic pathophysiology. There appears to be a strong predictive correlation between the in vitro biochemical phenotype and the clinical pattern of epilepsy vs movement disorder.
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Affiliation(s)
- Huijie Feng
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing
| | - Benita Sjögren
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing
| | - Behirda Karaj
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing
| | - Vincent Shaw
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing
| | - Aysegul Gezer
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing
| | - Richard R Neubig
- From the Department of Pharmacology & Toxicology, Michigan State University, East Lansing.
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Sakamoto S, Monden Y, Fukai R, Miyake N, Saito H, Miyauchi A, Matsumoto A, Nagashima M, Osaka H, Matsumoto N, Yamagata T. A case of severe movement disorder with GNAO1 mutation responsive to topiramate. Brain Dev 2017; 39:439-443. [PMID: 27916449 DOI: 10.1016/j.braindev.2016.11.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 11/15/2016] [Accepted: 11/16/2016] [Indexed: 11/15/2022]
Abstract
We report the case of a 19-year-old female patient who had progressive chorea associated with a GNAO1 mutation. Chorea was refractory to multiple anticonvulsants, and the patient suffered from tiapride-induced neuroleptic malignant syndrome. After identification of a GNAO1 missense mutation at the age of 18years, topiramate treatment was initiated and the frequency of chorea decreased dramatically. The efficacy of topiramate may have been related to the inhibitory modulation of voltage-activated Ca2+ channels. Given the side effects and complications associated with neuroleptics and deep brain stimulation, respectively, topiramate is recommended for the first-line management of severe chorea associated with a GNAO1 mutation.
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Affiliation(s)
- Saori Sakamoto
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Yukifumi Monden
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan; Department of Pediatrics, International University of Health and Welfare, 537-3 Iguchi, Shiobara, Tochigi 329-2763, Japan.
| | - Ryoko Fukai
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Neurology and Stroke Medicine, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Hiroshi Saito
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Akihiko Miyauchi
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Ayumi Matsumoto
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Masako Nagashima
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Hitoshi Osaka
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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11
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Abstract
Itch is a protective sensation producing a desire to scratch. Pathologic itch can be a chronic symptom of illnesses such as uremia, cholestatic liver disease, neuropathies and dermatitis, however current therapeutic options are limited. Many types of cell surface receptors, including those present on cells in the skin, on sensory neurons and on neurons in the spinal cord, have been implicated in itch signaling. The role of G protein signaling in the regulation of pruriception is poorly understood. We identify here 2 G protein signaling components whose mutation impairs itch sensation. R7bp (a.k.a. Rgs7bp) is a palmitoylated membrane anchoring protein expressed in neurons that facilitates Gαi/o -directed GTPase activating protein activity mediated by the Gβ5/R7-RGS complex. Knockout of R7bp diminishes scratching responses to multiple cutaneously applied and intrathecally-administered pruritogens in mice. Knock-in to mice of a GTPase activating protein-insensitive mutant of Gαo (Gnao1 G184S/+) produces a similar pruriceptive phenotype. The pruriceptive defect in R7bp knockout mice was rescued in double knockout mice also lacking Oprk1, encoding the G protein-coupled kappa-opioid receptor whose activation is known to inhibit itch sensation. In a model of atopic dermatitis (eczema), R7bp knockout mice showed diminished scratching behavior and enhanced sensitivity to kappa opioid agonists. Taken together, our results indicate that R7bp is a key regulator of itch sensation and suggest the potential targeting of R7bp-dependent GTPase activating protein activity as a novel therapeutic strategy for pathological itch.
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12
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Gerber KJ, Squires KE, Hepler JR. Roles for Regulator of G Protein Signaling Proteins in Synaptic Signaling and Plasticity. Mol Pharmacol 2015; 89:273-86. [PMID: 26655302 DOI: 10.1124/mol.115.102210] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/10/2015] [Indexed: 11/22/2022] Open
Abstract
The regulator of G protein signaling (RGS) family of proteins serves critical roles in G protein-coupled receptor (GPCR) and heterotrimeric G protein signal transduction. RGS proteins are best understood as negative regulators of GPCR/G protein signaling. They achieve this by acting as GTPase activating proteins (GAPs) for Gα subunits and accelerating the turnoff of G protein signaling. Many RGS proteins also bind additional signaling partners that either regulate their functions or enable them to regulate other important signaling events. At neuronal synapses, GPCRs, G proteins, and RGS proteins work in coordination to regulate key aspects of neurotransmitter release, synaptic transmission, and synaptic plasticity, which are necessary for central nervous system physiology and behavior. Accumulating evidence has revealed key roles for specific RGS proteins in multiple signaling pathways at neuronal synapses, regulating both pre- and postsynaptic signaling events and synaptic plasticity. Here, we review and highlight the current knowledge of specific RGS proteins (RGS2, RGS4, RGS7, RGS9-2, and RGS14) that have been clearly demonstrated to serve critical roles in modulating synaptic signaling and plasticity throughout the brain, and we consider their potential as future therapeutic targets.
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Affiliation(s)
- Kyle J Gerber
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - Katherine E Squires
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
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13
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Neubig RR. RGS-Insensitive G Proteins as In Vivo Probes of RGS Function. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:13-30. [PMID: 26123300 DOI: 10.1016/bs.pmbts.2015.04.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Guanine nucleotide-binding proteins of the inhibitory (Gi/o) class play critical physiological roles and the receptors that activate them are important therapeutic targets (e.g., mu opioid, serotonin 5HT1a, etc.). Gi/o proteins are negatively regulated by regulator of G protein signaling (RGS) proteins. The redundant actions of the 20 different RGS family members have made it difficult to establish their overall physiological role. A unique G protein mutation (G184S in Gαi/o) prevents RGS binding to the Gα subunit and blocks all RGS action at that particular Gα subunit. The robust phenotypes of mice expressing these RGS-insensitive (RGSi) mutant G proteins illustrate the profound action of RGS proteins in cardiovascular, metabolic, and central nervous system functions. Specifically, the enhanced Gαi2 signaling through the RGSi Gαi2(G184S) mutant knock-in mice shows protection against cardiac ischemia/reperfusion injury and potentiation of serotonin-mediated antidepressant actions. In contrast, the RGSi Gαo mutant knock-in produces enhanced mu-opioid receptor-mediated analgesia but also a seizure phenotype. These genetic models provide novel insights into potential therapeutic strategies related to RGS protein inhibitors and/or G protein subtype-biased agonists at particular GPCRs.
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Affiliation(s)
- Richard R Neubig
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan, USA.
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14
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Saitsu H, Fukai R, Ben-Zeev B, Sakai Y, Mimaki M, Okamoto N, Suzuki Y, Monden Y, Saito H, Tziperman B, Torio M, Akamine S, Takahashi N, Osaka H, Yamagata T, Nakamura K, Tsurusaki Y, Nakashima M, Miyake N, Shiina M, Ogata K, Matsumoto N. Phenotypic spectrum of GNAO1 variants: epileptic encephalopathy to involuntary movements with severe developmental delay. Eur J Hum Genet 2015; 24:129-34. [PMID: 25966631 DOI: 10.1038/ejhg.2015.92] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/24/2015] [Accepted: 04/14/2015] [Indexed: 12/11/2022] Open
Abstract
De novo GNAO1 variants have been found in four patients including three patients with Ohtahara syndrome and one patient with childhood epilepsy. In addition, two patients showed involuntary movements, suggesting that GNAO1 variants can cause various neurological phenotypes. Here we report an additional four patients with de novo missense GNAO1 variants, one of which was identical to that of the previously reported. All the three novel variants were predicted to impair Gαo function by structural evaluation. Two patients showed early-onset epileptic encephalopathy, presenting with migrating or multifocal partial seizures in their clinical course, but the remaining two patients showed no or a few seizures. All the four patients showed severe intellectual disability, motor developmental delay, and involuntary movements. Progressive cerebral atrophy and thin corpus callosum were common features in brain images. Our study demonstrated that GNAO1 variants can cause involuntary movements and severe developmental delay with/without seizures, including various types of early-onset epileptic encephalopathy.
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Affiliation(s)
- Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Ryoko Fukai
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.,Department of Neurology and Stroke Medicine, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Bruria Ben-Zeev
- The Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Ramat Gan, Israel.,Sackler School of Medicine, Tel Aviv University, Tel aviv, Israel
| | - Yasunari Sakai
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | - Nobuhiko Okamoto
- Department of Medical Genetics, Osaka Medical Center and Research Institute for Maternal and Child Health, Osaka, Japan
| | - Yasuhiro Suzuki
- Department of Pediatric Neurology, Osaka Medical Center and Research Institute for Maternal and Child Health, Osaka, Japan
| | - Yukifumi Monden
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Hiroshi Saito
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Barak Tziperman
- The Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Ramat Gan, Israel
| | - Michiko Torio
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Satoshi Akamine
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | - Hitoshi Osaka
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | | | - Kazuyuki Nakamura
- Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Mitsuko Nakashima
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Masaaki Shiina
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Kazuhiro Ogata
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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15
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Stewart A, Fisher RA. Introduction: G Protein-coupled Receptors and RGS Proteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:1-11. [PMID: 26123299 DOI: 10.1016/bs.pmbts.2015.03.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Here, we provide an overview of the role of regulator of G protein-signaling (RGS) proteins in signaling by G protein-coupled receptors (GPCRs), the latter of which represent the largest class of cell surface receptors in humans responsible for transducing diverse extracellular signals into the intracellular environment. Given that GPCRs regulate virtually every known physiological process, it is unsurprising that their dysregulation plays a causative role in many human diseases and they are targets of 40-50% of currently marketed pharmaceuticals. Activated GPCRs function as GTPase exchange factors for Gα subunits of heterotrimeric G proteins, promoting the formation of Gα-GTP and dissociated Gβγ subunits that regulate diverse effectors including enzymes, ion channels, and protein kinases. Termination of signaling is mediated by the intrinsic GTPase activity of Gα subunits leading to reformation of the inactive Gαβγ heterotrimer. RGS proteins determine the magnitude and duration of cellular responses initiated by many GPCRs by functioning as GTPase-accelerating proteins (GAPs) for specific Gα subunits. Twenty canonical mammalian RGS proteins, divided into four subfamilies, act as functional GAPs while almost 20 additional proteins contain nonfunctional RGS homology domains that often mediate interaction with GPCRs or Gα subunits. RGS protein biochemistry has been well elucidated in vitro, but the physiological functions of each RGS family member remain largely unexplored. This book summarizes recent advances employing modified model organisms that reveal RGS protein functions in vivo, providing evidence that RGS protein modulation of G protein signaling and GPCRs can be as important as initiation of signaling by GPCRs.
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Affiliation(s)
- Adele Stewart
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Rory A Fisher
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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16
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Kehrl JM, Sahaya K, Dalton HM, Charbeneau RA, Kohut KT, Gilbert K, Pelz MC, Parent J, Neubig RR. Gain-of-function mutation in Gnao1: a murine model of epileptiform encephalopathy (EIEE17)? Mamm Genome 2014; 25:202-10. [PMID: 24700286 PMCID: PMC4042023 DOI: 10.1007/s00335-014-9509-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Accepted: 03/11/2014] [Indexed: 12/13/2022]
Abstract
G protein-coupled receptors strongly modulate neuronal excitability but there has been little evidence for G protein mechanisms in genetic epilepsies. Recently, four patients with epileptic encephalopathy (EIEE17) were found to have mutations in GNAO1, the most abundant G protein in brain, but the mechanism of this effect is not known. The GNAO1 gene product, Gαo, negatively regulates neurotransmitter release. Here, we report a dominant murine model of Gnao1-related seizures and sudden death. We introduced a genomic gain-of-function knock-in mutation (Gnao1 (+/G184S)) that prevents Go turnoff by Regulators of G protein signaling proteins. This results in rare seizures, strain-dependent death between 15 and 40 weeks of age, and a markedly increased frequency of interictal epileptiform discharges. Mutants on a C57BL/6J background also have faster sensitization to pentylenetetrazol (PTZ) kindling. Both premature lethality and PTZ kindling effects are suppressed in the 129SvJ mouse strain. We have mapped a 129S-derived modifier locus on Chromosome 17 (within the region 41-70 MB) as a Modifer of G protein Seizures (Mogs1). Our mouse model suggests a novel gain-of-function mechanism for the newly defined subset of epileptic encephalopathy (EIEE17). Furthermore, it reveals a new epilepsy susceptibility modifier Mogs1 with implications for the complex genetics of human epilepsy as well as sudden death in epilepsy.
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Affiliation(s)
- Jason M. Kehrl
- />Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Kinshuk Sahaya
- />Department of Neurology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Hans M. Dalton
- />Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109 USA
| | | | - Kevin T. Kohut
- />Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Kristen Gilbert
- />Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Madeline C. Pelz
- />Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Jack Parent
- />Department of Neurology, University of Michigan, Ann Arbor, MI 48109 USA
- />Ann Arbor Veterans Administration Healthcare System, Ann Arbor, MI 48105 USA
| | - Richard R. Neubig
- />Department of Pharmacology & Toxicology, Michigan State University, B440 Life Sciences, 1355 Bogue St, East Lansing, MI 48824 USA
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17
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Nakamura K, Kodera H, Akita T, Shiina M, Kato M, Hoshino H, Terashima H, Osaka H, Nakamura S, Tohyama J, Kumada T, Furukawa T, Iwata S, Shiihara T, Kubota M, Miyatake S, Koshimizu E, Nishiyama K, Nakashima M, Tsurusaki Y, Miyake N, Hayasaka K, Ogata K, Fukuda A, Matsumoto N, Saitsu H. De Novo mutations in GNAO1, encoding a Gαo subunit of heterotrimeric G proteins, cause epileptic encephalopathy. Am J Hum Genet 2013; 93:496-505. [PMID: 23993195 DOI: 10.1016/j.ajhg.2013.07.014] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 07/09/2013] [Accepted: 07/17/2013] [Indexed: 12/21/2022] Open
Abstract
Heterotrimeric G proteins, composed of α, β, and γ subunits, can transduce a variety of signals from seven-transmembrane-type receptors to intracellular effectors. By whole-exome sequencing and subsequent mutation screening, we identified de novo heterozygous mutations in GNAO1, which encodes a Gαo subunit of heterotrimeric G proteins, in four individuals with epileptic encephalopathy. Two of the affected individuals also showed involuntary movements. Somatic mosaicism (approximately 35% to 50% of cells, distributed across multiple cell types, harbored the mutation) was shown in one individual. By mapping the mutation onto three-dimensional models of the Gα subunit in three different complexed states, we found that the three mutants (c.521A>G [p.Asp174Gly], c.836T>A [p.Ile279Asn], and c.572_592del [p.Thr191_Phe197del]) are predicted to destabilize the Gα subunit fold. A fourth mutant (c.607G>A), in which the Gly203 residue located within the highly conserved switch II region is substituted to Arg, is predicted to impair GTP binding and/or activation of downstream effectors, although the p.Gly203Arg substitution might not interfere with Gα binding to G-protein-coupled receptors. Transient-expression experiments suggested that localization to the plasma membrane was variably impaired in the three putatively destabilized mutants. Electrophysiological analysis showed that Gαo-mediated inhibition of calcium currents by norepinephrine tended to be lower in three of the four Gαo mutants. These data suggest that aberrant Gαo signaling can cause multiple neurodevelopmental phenotypes, including epileptic encephalopathy and involuntary movements.
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Affiliation(s)
- Kazuyuki Nakamura
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, Japan
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18
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Differential control of opioid antinociception to thermal stimuli in a knock-in mouse expressing regulator of G-protein signaling-insensitive Gαo protein. J Neurosci 2013; 33:4369-77. [PMID: 23467353 DOI: 10.1523/jneurosci.5470-12.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Regulator of G-protein signaling (RGS) proteins classically function as negative modulators of G-protein-coupled receptor signaling. In vitro, RGS proteins have been shown to inhibit signaling by agonists at the μ-opioid receptor, including morphine. The goal of the present study was to evaluate the contribution of endogenous RGS proteins to the antinociceptive effects of morphine and other opioid agonists. To do this, a knock-in mouse that expresses an RGS-insensitive (RGSi) mutant Gαo protein, Gαo(G184S) (Gαo RGSi), was evaluated for morphine or methadone antinociception in response to noxious thermal stimuli. Mice expressing Gαo RGSi subunits exhibited a naltrexone-sensitive enhancement of baseline latency in both the hot-plate and warm-water tail-withdrawal tests. In the hot-plate test, a measure of supraspinal nociception, morphine antinociception was increased, and this was associated with an increased ability of opioids to inhibit presynaptic GABA neurotransmission in the periaqueductal gray. In contrast, antinociception produced by either morphine or methadone was reduced in the tail-withdrawal test, a measure of spinal nociception. In whole-brain and spinal cord homogenates from mice expressing Gαo RGSi subunits, there was a small loss of Gαo expression and an accompanying decrease in basal G-protein activity. Our results strongly support a role for RGS proteins as negative regulators of opioid supraspinal antinociception and also reveal a potential novel function of RGS proteins as positive regulators of opioid spinal antinociceptive pathways.
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19
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Manavalan A, Feng L, Sze SK, Hu JM, Heese K. New insights into the brain protein metabolism of Gastrodia elata-treated rats by quantitative proteomics. J Proteomics 2012; 75:2468-79. [PMID: 22402058 DOI: 10.1016/j.jprot.2012.02.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 02/13/2012] [Accepted: 02/20/2012] [Indexed: 01/05/2023]
Abstract
Gastrodia elata (tianma) is a traditional Chinese herbal medicine (TCM) often used for the treatment of cerebrovascular diseases. In this study, we investigated the effects of tianma on the brain protein metabolism by quantitative proteomics to gain evidence for a direct relationship between tianma treatment and brain functions. One-year-old rats were treated with tianma (~2.5 g/kg/day) for 3months and the brain tissue proteome was analyzed by using the iTRAQ (isobaric tag for relative and absolute quantification) technology. According to our results, the long-term treatment with tianma could modulate the brain protein metabolism at the proteome level by down-regulating the expressions of various proteins, such as Gnao1 and Dctn2, which are related to neuronal growth cone control and synaptic activities. In addition, tianma treatment also induced the up-regulation of molecular chaperons and proteins related to the misfolded protein response, like Anxa5, and also other proteins involved in Huntington's disease (HD) (e.g. Pacsin1 and Arf3). Concluding, tianma could eventually contribute to activities related to synaptic plasticity and neuro-restorative processes and thus might be a novel candidate agent for the treatment of neurodegenerative diseases by regulating the brain proteome.
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Affiliation(s)
- Arulmani Manavalan
- School of Biological Sciences, College of Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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20
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Kimple AJ, Bosch DE, Giguère PM, Siderovski DP. Regulators of G-protein signaling and their Gα substrates: promises and challenges in their use as drug discovery targets. Pharmacol Rev 2011; 63:728-49. [PMID: 21737532 DOI: 10.1124/pr.110.003038] [Citation(s) in RCA: 184] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Because G-protein coupled receptors (GPCRs) continue to represent excellent targets for the discovery and development of small-molecule therapeutics, it is posited that additional protein components of the signal transduction pathways emanating from activated GPCRs themselves are attractive as drug discovery targets. This review considers the drug discovery potential of two such components: members of the "regulators of G-protein signaling" (RGS protein) superfamily, as well as their substrates, the heterotrimeric G-protein α subunits. Highlighted are recent advances, stemming from mouse knockout studies and the use of "RGS-insensitivity" and fast-hydrolysis mutations to Gα, in our understanding of how RGS proteins selectively act in (patho)physiologic conditions controlled by GPCR signaling and how they act on the nucleotide cycling of heterotrimeric G-proteins in shaping the kinetics and sensitivity of GPCR signaling. Progress is documented regarding recent activities along the path to devising screening assays and chemical probes for the RGS protein target, not only in pursuits of inhibitors of RGS domain-mediated acceleration of Gα GTP hydrolysis but also to embrace the potential of finding allosteric activators of this RGS protein action. The review concludes in considering the Gα subunit itself as a drug target, as brought to focus by recent reports of activating mutations to GNAQ and GNA11 in ocular (uveal) melanoma. We consider the likelihood of several strategies for antagonizing the function of these oncogene alleles and their gene products, including the use of RGS proteins with Gα(q) selectivity.
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Affiliation(s)
- Adam J Kimple
- Department of Pharmacology, UNC Neuroscience Center, UNC School of Medicine, University of North Carolina at Chapel Hill, 120 Mason Farm Road, Suite 4010, Chapel Hill, NC 27599-7365, USA
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21
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Sjögren B. Regulator of G protein signaling proteins as drug targets: current state and future possibilities. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 62:315-47. [PMID: 21907914 DOI: 10.1016/b978-0-12-385952-5.00002-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Regulators of G protein signaling (RGS) proteins have emerged in the past two decades as novel drug targets in many areas of research. Their importance in regulating signaling via G protein-coupled receptors has become evident as numerous studies have been published on the structure and function of RGS proteins. A number of genetic models have also been developed, demonstrating the potential clinical importance of RGS proteins in various disease states, including central nervous system disorders, cardiovascular disease, diabetes, and several types of cancer. Apart from their classical mechanism of action as GTPase-activating proteins (GAPs), RGS proteins can also serve other noncanonical functions. This opens up a new approach to targeting RGS proteins in drug discovery as the view on the function of these proteins is constantly evolving. This chapter summarizes the latest development in RGS protein drug discovery with special emphasis on noncanonical functions and regulatory mechanisms of RGS protein expression. As more reports are being published on this group of proteins, it is becoming clear that modulation of GAP activity might not be the only way to therapeutically target RGS proteins.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
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22
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Kaur K, Kehrl JM, Charbeneau RA, Neubig RR. RGS-insensitive Gα subunits: probes of Gα subtype-selective signaling and physiological functions of RGS proteins. Methods Mol Biol 2011; 756:75-98. [PMID: 21870221 DOI: 10.1007/978-1-61779-160-4_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The Regulator of G protein Signaling (RGS) proteins were identified as a family in 1996 and humans have more than 30 such proteins. Their best known function is to suppress G Protein-Coupled Receptors (GPCR) signaling by increasing the rate of Gα turnoff through stimulation of GTPase activity (i.e., GTPase acceleration protein or GAP activity). The GAP activity of RGS proteins on the Gαi and Gαq family of G proteins can terminate signals initiated by both α and βγ subunits. RGS proteins also serve as scaffolds, assembling signal-regulating modules. Understanding the physiological roles of RGS proteins is of great importance, as GPCRs are major targets for drug development. The traditional method of using RGS knockout mice has provided some information about the role of RGS proteins but in many cases effects are modest, perhaps because of redundancy in RGS protein function. As an alternative approach, we have utilized a glycine-to-serine mutation in the switch 1 region of Gα subunits that prevents RGS binding. The mutation has no known effects on Gα binding to receptor, Gβγ, or effectors. Alterations in function resulting from the G>S mutation imply a role for both the specific mutated Gα subunit and its regulation by RGS protein activity. Mutant rodents expressing these G>S mutant Gα subunits have strong phenotypes and provide important information about specific physiological functions of Gαi2 and Gαo and their control by RGS. The conceptual framework behind this approach and a summary of recent results is presented in this chapter.
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Affiliation(s)
- Kuljeet Kaur
- Department of Pharmacology, The University of Michigan Medical School, Ann Arbor, MI, USA
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23
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Regulators of G Protein Signaling Proteins as Targets for Drug Discovery. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2010; 91:81-119. [DOI: 10.1016/s1877-1173(10)91004-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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24
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Icaza EE, Huang X, Fu Y, Neubig RR, Baghdoyan HA, Lydic R. Isoflurane-induced changes in righting response and breathing are modulated by RGS proteins. Anesth Analg 2009; 109:1500-5. [PMID: 19843788 DOI: 10.1213/ane.0b013e3181ba7815] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Recent evidence suggests that G protein-coupled receptors, especially those linked to G(alpha)(i), contribute to the mechanisms of anesthetic action. Regulator of G protein signaling (RGS) proteins bind to activated G(alpha)(i) and inhibit signal transduction. Genomic knock-in mice with an RGS-insensitive G(alpha)(i2) G184S (G(alpha)(i2) GS) allele exhibit enhanced G(alpha)(i2) signaling and provide a novel approach for investigating the role of G(alpha)(i2) signaling and RGS proteins in general anesthesia. METHODS We anesthetized homozygous G(alpha)(i2) GS/GS and wild-type (WT) mice with isoflurane and quantified time (in seconds) to loss and resumption of righting response. During recovery from isoflurane anesthesia, breathing was quantified in a plethysmography chamber for both lines of mice. RESULTS G(alpha)(i2) GS/GS mice required significantly less time for loss of righting and significantly more time for resumption of righting than WT mice. During recovery from isoflurane anesthesia, G(alpha)(i2) GS/GS mice exhibited significantly greater respiratory depression. Poincaré analyses show that GS/GS mice have diminished respiratory variability compared with WT mice. CONCLUSION Modulation of G(alpha)(i2) signaling by RGS proteins alters loss and resumption of wakefulness and state-dependent changes in breathing.
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Affiliation(s)
- Eduardo E Icaza
- Departments of Anesthesiology, University of Michigan, Ann Arbor, Michigan 48109-5615, USA
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