1
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Schröper T, Mehrkens D, Leiss V, Tellkamp F, Engelhardt S, Herzig S, Birnbaumer L, Nürnberg B, Matthes J. Protective effects of Gα i3 deficiency in a murine heart-failure model of β 1-adrenoceptor overexpression. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024; 397:2401-2420. [PMID: 37843590 PMCID: PMC10933181 DOI: 10.1007/s00210-023-02751-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 09/26/2023] [Indexed: 10/17/2023]
Abstract
We have shown that in murine cardiomyopathy caused by overexpression of the β1-adrenoceptor, Gαi2-deficiency is detrimental. Given the growing evidence for isoform-specific Gαi-functions, we now examined the consequences of Gαi3 deficiency in the same heart-failure model. Mice overexpressing cardiac β1-adrenoceptors with (β1-tg) or without Gαi3-expression (β1-tg/Gαi3-/-) were compared to C57BL/6 wildtypes and global Gαi3-knockouts (Gαi3-/-). The life span of β1-tg mice was significantly shortened but improved when Gαi3 was lacking (95% CI: 592-655 vs. 644-747 days). At 300 days of age, left-ventricular function and survival rate were similar in all groups. At 550 days of age, β1-tg but not β1-tg/Gαi3-/- mice displayed impaired ejection fraction (35 ± 18% vs. 52 ± 16%) compared to wildtype (59 ± 4%) and Gαi3-/- mice (60 ± 5%). Diastolic dysfunction of β1-tg mice was prevented by Gαi3 deficiency, too. The increase of ANP mRNA levels and ventricular fibrosis observed in β1-tg hearts was significantly attenuated in β1-tg/Gαi3-/- mice. Transcript levels of phospholamban, ryanodine receptor 2, and cardiac troponin I were similar in all groups. However, Western blots and phospho-proteomic analyses showed that in β1-tg, but not β1-tg/Gαi3-/- ventricles, phospholamban protein was reduced while its phosphorylation increased. Here, we show that in mice overexpressing the cardiac β1-adrenoceptor, Gαi3 deficiency slows or even prevents cardiomyopathy and increases shortened life span. Previously, we found Gαi2 deficiency to aggravate cardiac dysfunction and mortality in the same heart-failure model. Our findings indicate isoform-specific interventions into Gi-dependent signaling to be promising cardio-protective strategies.
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Affiliation(s)
- Tobias Schröper
- Center of Pharmacology, Department II, University of Cologne and University Hospital Cologne, Cologne, Germany
- Department of Internal Medicine III, University Hospital of Cologne, Cologne, Germany and Centre for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Dennis Mehrkens
- Department of Internal Medicine III, University Hospital of Cologne, Cologne, Germany and Centre for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
- Centre for Molecular Medicine Cologne, CMMC, University of Cologne, Cologne, Germany
| | - Veronika Leiss
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute for Experimental and Clinical Pharmacology and Pharmacogenomics, and Interfaculty Centre for Pharmacogenomics and Drug Research, Eberhard Karls Universität, Tübingen, Germany
| | - Frederik Tellkamp
- CECAD Research Centre Institute for Genetics, University of Cologne, Cologne, Germany
| | - Stefan Engelhardt
- Institute of Pharmacology and Toxicology, Technische Universität München, Munich, Germany
| | - Stefan Herzig
- Center of Pharmacology, Department II, University of Cologne and University Hospital Cologne, Cologne, Germany
- TH Köln-University of Applied Sciences, Cologne, Germany
| | - Lutz Birnbaumer
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, North Carolina, USA
- Institute of Biomedical Research, School of Medical Sciences, Catholic University of Buenos Aires, Buenos Aires, Argentina
| | - Bernd Nürnberg
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute for Experimental and Clinical Pharmacology and Pharmacogenomics, and Interfaculty Centre for Pharmacogenomics and Drug Research, Eberhard Karls Universität, Tübingen, Germany
| | - Jan Matthes
- Center of Pharmacology, Department II, University of Cologne and University Hospital Cologne, Cologne, Germany.
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2
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Haase J, Jones AKC, Mc Veigh CJ, Brown E, Clarke G, Ahnert-Hilger G. Sex and brain region-specific regulation of serotonin transporter activity in synaptosomes in guanine nucleotide-binding protein G(q) alpha knockout mice. J Neurochem 2021; 159:156-171. [PMID: 34309872 DOI: 10.1111/jnc.15482] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 07/15/2021] [Accepted: 07/21/2021] [Indexed: 10/20/2022]
Abstract
The regulation of the serotonin transporter (SERT) by guanine nucleotide-binding protein alpha (Gα) q was investigated using Gαq knockout mice. In the absence of Gαq, SERT-mediated uptake of 5-hydroxytryptamine (5HT) was enhanced in midbrain and frontal cortex synaptosomes, but only in female mice. The mechanisms underlying this sexual dimorphism were investigated using quantitative western blot analysis revealing brain region-specific differences. In the frontal cortex, SERT protein expression was decreased in male knockout mice, seemingly explaining the sex-dependent variation in SERT activity. The differential expression of Gαi1 in female mice contributes to the sex differences in the midbrain. In fact, Gαi1 levels inversely correlate with 5HT uptake rates across both sexes and genotypes. Likely due to differential SERT regulation as well as sex differences in the expression of tryptophan hydroxylase 2, Gαq knockout mice also displayed sex- and genotype-dependent alterations in total 5HT tissue levels as determined by high-performance liquid chromatography. Gαq inhibitors, YM-254890 and BIM-46187, differentially affected SERT activity in both, synaptosomes and cultured cells. YM-254890 treatment mimicked the effect of Gαq knockout in the frontal cortex. BIM-46187, which promotes the nucleotide-free form of Gα proteins, substantially inhibited 5HT uptake, prompting us to hypothesise that Gαq interacts with SERT similarly as with G-protein-coupled receptors and inhibits SERT activity by modulating transport-associated conformational changes. Taken together, our findings reveal a novel mechanism of SERT regulation and impact our understanding of sex differences in diseases associated with dysregulation of serotonin transmission, such as depression and anxiety.
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Affiliation(s)
- Jana Haase
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Aimée K C Jones
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Conor J Mc Veigh
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Eric Brown
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Gerard Clarke
- APC Microbiome Ireland and Department of Psychiatry and Neurobehavioural Science, University College Cork, Cork, Ireland
| | - Gudrun Ahnert-Hilger
- Institute of Integrative Neuroanatomy, Charité University Medicine Berlin and Max-Planck-Institute for Biophysical Chemistry Göttingen, Göttingen, Germany
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3
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Zou QY, Zhao YJ, Zhou C, Liu AX, Zhong XQ, Yan Q, Li Y, Yi FX, Bird IM, Zheng J. G Protein α Subunit 14 Mediates Fibroblast Growth Factor 2-Induced Cellular Responses in Human Endothelial Cells. J Cell Physiol 2018; 234:10184-10195. [PMID: 30387149 DOI: 10.1002/jcp.27688] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 10/09/2018] [Indexed: 12/20/2022]
Abstract
During pregnancy, a tremendous increase in fetoplacental angiogenesis is associated with elevated blood flow. Aberrant fetoplacental vascular function may lead to pregnancy complications including pre-eclampsia. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental endothelial function. G protein α subunit 14 (GNA14), a member of Gαq/11 subfamily is involved in mediating hypertensive diseases and tumor vascularization. However, little is known about roles of GNA14 in mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using human umbilical vein endothelial cells (HUVECs) cultured under physiological chronic low oxygen (3% O2 ) as a cell model, we show that transfecting cells with adenovirus carrying GNA14 complementary DNA (cDNA; Ad-GNA14) increases (p < 0.05) protein expression of GNA14. GNA14 overexpression blocks (p < 0.05) FGF2-stimulated endothelial migration, whereas it enhances (p < 0.05) endothelial monolayer integrity (maximum increase of ~35% over the control at 24 hr) in response to FGF2. In contrast, GNA14 overexpression does not significantly alter VEGFA-stimulated cell migration, VEGFA-weakened cell monolayer integrity, and intracellular Ca++ mobilization in response to adenosine triphosphate (ATP), FGF2, and VEGFA. GNA14 overexpression does not alter either FGF2- or VEGFA-induced phosphorylation of ERK1/2. However, GNA14 overexpression time-dependently elevates (p < 0.05) phosphorylation of phospholipase C-β3 (PLCβ3) at S1105 in response to FGF2, but not VEGFA. These data suggest that GNA14 distinctively mediates fetoplacental endothelial cell migration and permeability in response to FGF2 and VEGFA, possibly in part by altering activation of PLCβ3 under physiological chronic low oxygen.
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Affiliation(s)
- Qing-Yun Zou
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Ying-Jie Zhao
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Rheumatology, Qilu Hospital, Shandong University, Jinan, Shandong, China
| | - Chi Zhou
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Ai-Xia Liu
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Reproductive Endocrinology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xin-Qi Zhong
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Pediatrics, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Qin Yan
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Gynecology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yan Li
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Fu-Xian Yi
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Ian M Bird
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
| | - Jing Zheng
- Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin.,Cardiovascular Medicine Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong, China
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4
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Zou Q, Zhao Y, Li H, Wang X, Liu A, Zhong X, Yan Q, Li Y, Zhou C, Zheng J. GNA11 differentially mediates fibroblast growth factor 2- and vascular endothelial growth factor A-induced cellular responses in human fetoplacental endothelial cells. J Physiol 2018; 596:2333-2344. [PMID: 29659033 PMCID: PMC6002203 DOI: 10.1113/jp275677] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 04/09/2018] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS Fetoplacental vascular growth is critical to fetal growth. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are two major regulators of fetoplacental vascular growth. G protein α subunit 11 (GNA11) transmits signals from many external stimuli to the cellular interior and may mediate endothelial function. It is not known whether GNA11 mediates FGF2- and VEGFA-induced endothelial cell responses under physiological chronic low O2 . In the present study, we show that knockdown of GNA11 significantly decreases FGF2- and VEGFA-induced fetoplacental endothelial cell migration but not proliferation and permeability. Such decreases in endothelial migration are associated with increased phosphorylation of phospholipase C-β3. The results of the present study suggest differential roles of GNA11 with respect to mediating FGF2- and VEGFA-induced fetoplacental endothelial function. ABSTRACT During pregnancy, fetoplacental angiogenesis is dramatically increased in association with rapidly elevated blood flow. Any disruption of fetoplacental angiogenesis may lead to pregnancy complications such as intrauterine growth restriction. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental angiogenesis. G protein α subunits q (GNAq) and 11 (GNA11) are two members of the Gαq/11 subfamily involved in mediating vascular growth and basal blood pressure. However, little is known about the roles of GNA11 alone with respect to mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using a cell model of human umbilical cord vein endothelial cells cultured under physiological chronic low O2 (3% O2 ), we showed that GNA11 small interfering RNA (siRNA) dramatically inhibited (P < 0.05) FGF2- and VEGFA-stimulated fetoplacental endothelial migration (by ∼36% and ∼50%, respectively) but not proliferation and permeability. GNA11 siRNA also elevated (P < 0.05) FGF2- and VEGFA-induced phosphorylation of phospholipase C-β3 (PLCβ3) at S537 in a time-dependent fashion but not mitogen-activated protein kinase 3/1 (ERK1/2) and v-akt murine thymoma viral oncogene homologue 1 (AKT1). These data suggest that GNA11 mediates FGF2- and VEGFA-stimulated fetoplacental endothelial cell migration partially via altering the activation of PLCβ3.
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Affiliation(s)
- Qing‐yun Zou
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Ying‐jie Zhao
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Rheumatology, Qilu HospitalShandong UniversityJinanShandongChina
| | - Hua Li
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Rheumatology and ImmunologyAffiliated Hospital of Qingdao UniversityQingdaoShandongChina
| | - Xiang‐zhen Wang
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Obstetrics and GynecologyNanshan District Maternal and Child Healthcare HospitalShenzhenGuangdongChina
| | - Ai‐xia Liu
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Reproductive EndocrinologyZhejiang UniversityHangzhouZhejiangChina
| | - Xin‐qi Zhong
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Pediatrics3rd Affiliated Hospital of Guangzhou Medical UniversityGuangzhouGuangdongChina
| | - Qin Yan
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Gynecology, Shanghai First Maternity and Infant HospitalTongji University School of MedicineShanghaiChina
| | - Yan Li
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Chi Zhou
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Jing Zheng
- Department of Obstetrics and GynecologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Cardiovascular Medicine CenterAffiliated Hospital of Guangdong Medical UniversityZhanjiangGuangdongChina
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5
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Wang Q, Yue WWS, Jiang Z, Xue T, Kang SH, Bergles DE, Mikoshiba K, Offermanns S, Yau KW. Synergistic Signaling by Light and Acetylcholine in Mouse Iris Sphincter Muscle. Curr Biol 2017; 27:1791-1800.e5. [PMID: 28578927 PMCID: PMC8577559 DOI: 10.1016/j.cub.2017.05.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 04/04/2017] [Accepted: 05/05/2017] [Indexed: 01/29/2023]
Abstract
The mammalian pupillary light reflex (PLR) involves a bilateral brain circuit whereby afferent light signals in the optic nerve ultimately drive iris-sphincter-muscle contraction via excitatory cholinergic parasympathetic innervation [1, 2]. Additionally, the PLR in nocturnal and crepuscular sub-primate mammals has a "local" component in the isolated sphincter muscle [3-5], as in amphibians, fish, and bird [6-10]. In mouse, this local PLR requires the pigment melanopsin [5], originally found in intrinsically photosensitive retinal ganglion cells (ipRGCs) [11-19]. However, melanopsin's presence and effector pathway locally in the iris remain uncertain. The sphincter muscle itself may express melanopsin [5], or its cholinergic parasympathetic innervation may be modulated by suggested intraocular axonal collaterals of ipRGCs traveling to the eye's ciliary body or even to the iris [20-22]. Here, we show that the muscarinic receptor antagonist, atropine, eliminated the effect of acetylcholine (ACh), but not of light, on isolated mouse sphincter muscle. Conversely, selective genetic deletion of melanopsin in smooth muscle mostly removed the light-induced, but not the ACh-triggered, increase in isolated sphincter muscle's tension and largely suppressed the local PLR in vivo. Thus, sphincter muscle cells are bona fide, albeit unconventional, photoreceptors. We found melanopsin expression in a small subset of mouse iris sphincter muscle cells, with the light-induced contractile signal apparently spreading through gap junctions into neighboring muscle cells. Light and ACh share a common signaling pathway in sphincter muscle. In summary, our experiments have provided details of a photosignaling process in the eye occurring entirely outside the retina.
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Affiliation(s)
- Qian Wang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Biochemistry, Cellular, and Molecular Biology Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Wendy Wing Sze Yue
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Biochemistry, Cellular, and Molecular Biology Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Zheng Jiang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Tian Xue
- Chinese Academy of Science Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, Anhui, PRC
| | - Shin H Kang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Dwight E Bergles
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Saitama 351-0198, Japan
| | - Stefan Offermanns
- Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - King-Wai Yau
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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6
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Xie AX, Petravicz J, McCarthy KD. Molecular approaches for manipulating astrocytic signaling in vivo. Front Cell Neurosci 2015; 9:144. [PMID: 25941472 PMCID: PMC4403552 DOI: 10.3389/fncel.2015.00144] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 03/27/2015] [Indexed: 12/26/2022] Open
Abstract
Astrocytes are the predominant glial type in the central nervous system and play important roles in assisting neuronal function and network activity. Astrocytes exhibit complex signaling systems that are essential for their normal function and the homeostasis of the neural network. Altered signaling in astrocytes is closely associated with neurological and psychiatric diseases, suggesting tremendous therapeutic potential of these cells. To further understand astrocyte function in health and disease, it is important to study astrocytic signaling in vivo. In this review, we discuss molecular tools that enable the selective manipulation of astrocytic signaling, including the tools to selectively activate and inactivate astrocyte signaling in vivo. Lastly, we highlight a few tools in development that present strong potential for advancing our understanding of the role of astrocytes in physiology, behavior, and pathology.
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Affiliation(s)
- Alison X Xie
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Jeremy Petravicz
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology Cambridge, MA, USA
| | - Ken D McCarthy
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
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Woodard GE, Jardín I, Berna-Erro A, Salido GM, Rosado JA. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:97-183. [PMID: 26008785 DOI: 10.1016/bs.ircmb.2015.02.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.
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Affiliation(s)
- Geoffrey E Woodard
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - A Berna-Erro
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Gines M Salido
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Caceres, Spain
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8
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Chew KS, Schmidt TM, Rupp AC, Kofuji P, Trimarchi JM. Loss of gq/11 genes does not abolish melanopsin phototransduction. PLoS One 2014; 9:e98356. [PMID: 24870805 PMCID: PMC4037210 DOI: 10.1371/journal.pone.0098356] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 05/01/2014] [Indexed: 11/29/2022] Open
Abstract
In mammals, a subset of retinal ganglion cells (RGCs) expresses the photopigment melanopsin, which renders them intrinsically photosensitive (ipRGCs). These ipRGCs mediate various non-image-forming visual functions such as circadian photoentrainment and the pupillary light reflex (PLR). Melanopsin phototransduction begins with activation of a heterotrimeric G protein of unknown identity. Several studies of melanopsin phototransduction have implicated a G-protein of the Gq/11 family, which consists of Gna11, Gna14, Gnaq and Gna15, in melanopsin-evoked depolarization. However, the exact identity of the Gq/11 gene involved in this process has remained elusive. Additionally, whether Gq/11 G-proteins are necessary for melanopsin phototransduction in vivo has not yet been examined. We show here that the majority of ipRGCs express both Gna11 and Gna14, but neither Gnaq nor Gna15. Animals lacking the melanopsin protein have well-characterized deficits in the PLR and circadian behaviors, and we therefore examined these non-imaging forming visual functions in a variety of single and double mutants for Gq/11 family members. All Gq/11 mutant animals exhibited PLR and circadian behaviors indistinguishable from WT. In addition, we show persistence of ipRGC light-evoked responses in Gna11−/−; Gna14−/− retinas using multielectrode array recordings. These results demonstrate that Gq, G11, G14, or G15 alone or in combination are not necessary for melanopsin-based phototransduction, and suggest that ipRGCs may be able to utilize a Gq/11-independent phototransduction cascade in vivo.
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Affiliation(s)
- Kylie S. Chew
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
| | - Tiffany M. Schmidt
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Alan C. Rupp
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Jeffrey M. Trimarchi
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa, United States of America
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Siehler S. G12/13-dependent signaling of G-protein-coupled receptors: disease context and impact on drug discovery. Expert Opin Drug Discov 2013; 2:1591-604. [PMID: 23488903 DOI: 10.1517/17460441.2.12.1591] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
G-protein-coupled receptors (GPCRs) transmit extracellular signals across the plasma membrane via intracellular activation of heterotrimeric G proteins. The signal transduction pathways of Gs, Gi and Gq protein families are widely studied, whereas signaling properties of G12 proteins are only emerging. Many GPCRs were found to couple to G12/13 proteins in addition to coupling to one or more other types of G proteins. G12/13 proteins couple GPCRs to activation of the small monomeric GTPase RhoA. Activation of RhoA modulates various downstream effector systems relevant to diseases such as hypertension, artherosclerosis, asthma and cancer. GPCR screening assays exist for Gs-, Gi- and Gq-linked pathways, whereas a drug-screening assay for the G12-Rho pathway was developed only recently. The review gives an overview of the present understanding of the G12/13-related biology of GPCRs.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, WSJ-88.2.05, 4002 Basel, Switzerland +41 61 324 8946 ; +41 61 324 2870 ;
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10
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Expression of Gαz in C2C12 cells restrains myogenic differentiation. Cell Signal 2011; 23:389-97. [DOI: 10.1016/j.cellsig.2010.10.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 09/16/2010] [Accepted: 10/01/2010] [Indexed: 10/19/2022]
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11
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Coulon P, Kanyshkova T, Broicher T, Munsch T, Wettschureck N, Seidenbecher T, Meuth SG, Offermanns S, Pape HC, Budde T. Activity Modes in Thalamocortical Relay Neurons are Modulated by G(q)/G(11) Family G-proteins - Serotonergic and Glutamatergic Signaling. Front Cell Neurosci 2010; 4:132. [PMID: 21267426 PMCID: PMC3024565 DOI: 10.3389/fncel.2010.00132] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 09/28/2010] [Indexed: 11/13/2022] Open
Abstract
In thalamocortical relay (TC) neurons, G-protein-coupled receptors play an important part in the control of activity modes. A conditional Gα(q) knockout on the background of a constitutive Gα(11) knockout (Gα(q)/Gα(11) (-/-)) was used to determine the contribution of Gq/G11 family G-proteins to metabotropic serotonin (5-HT) and glutamate (Glu) function in the dorsal part of the lateral geniculate nucleus (dLGN). In control mice, current clamp recordings showed that α-m-5-HT induced a depolarization of V(rest) which was sufficient to suppress burst firing. This depolarization was concentration-dependent (100 μM: +6 ± 1 mV, n = 10; 200 μM: +10 ± 1 mV, n = 7) and had a conditioning effect on the activation of other Gα(q)-mediated pathways. The depolarization was significantly reduced in Gα(q)/Gα(11) (-/-) (100 μM: 3 ± 1 mV, n = 11; 200 μM: 5 ± 1 mV, n = 6) and was apparently insufficient to suppress burst firing. Activating Gα(q)-coupled muscarinic receptors affected the magnitude of α-m-5-HT-induced effects in a reciprocal manner. Furthermore, the depolarizing effect of mGluR1 agonists was significantly reduced in Gα(q)/Gα(11) (-/-) mice. Immunohistochemical stainings revealed binding of 5-HT(2C)R- and mGluR1α-, but not of 5-HT(2A)R-specific antibodies in the dLGN of Gα(q)/Gα(11) (-/-) mice. In conclusion, these findings demonstrate that transmitters of ascending brainstem fibers and corticofugal fibers both signal via a central element in the form of Gq/G11-mediated pathways to control activity modes in the TC system.
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Affiliation(s)
- Philippe Coulon
- Institut für Physiologie I, Westfälische Wilhelms-Universität Münster Münster, Germany
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12
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Abstract
G protein-coupled receptors (GPCRs) represent a large family of seven transmembrane receptors, which communicate extracellular signals into the cellular lumen. The human genome contains 720-800 GPCRs, and their diverse signal characteristics are determined by their specific tissue and subcellular expression profiles, as well as their coupling profile to the various G protein families (G(s), G(i), G(q), G(12)). The G protein coupling pattern links GPCR activation to the specific downstream effector pathways. G(12/13) signalling of GPCRs has been studied only recently in more detail, and involves activation of RhoGTPase nucleotide exchange factors (RhoGEFs). Four mammalian RhoGEFs regulated by G(12/13) proteins are known: p115-RhoGEF, PSD-95/Disc-large/ZO-1 homology-RhoGEF, leukemia-associated RhoGEF and lymphoid blast crisis-RhoGEF. These link GPCRs to activation of the small monomeric GTPase RhoA, and other downstream effectors. Misregulated G(12/13) signalling is involved in multiple pathophysiological conditions such as cancer, cardiovascular diseases, arterial and pulmonary hypertension, and bronchial asthma. Specific targeting of G(12/13) signalling-related diseases of GPCRs hence provides novel therapeutic approaches. Assays to quantitatively measure GPCR-mediated activation of G(12/13) are only emerging, and are required to understand the G(12/13)-linked pharmacology. The review gives an overview of G(12/13) signalling of GPCRs with a focus on RhoGEF proteins as the immediate mediators of G(12/13) activation.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, Basel, Switzerland.
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13
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Zuberi Z, Birnbaumer L, Tinker A. The role of inhibitory heterotrimeric G proteins in the control of in vivo heart rate dynamics. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1822-30. [PMID: 18832081 DOI: 10.1152/ajpregu.90625.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple isoforms of inhibitory Galpha-subunits (Galphai1,2,3, as well as Galphao) are present within the heart, and their role in modulating pacemaker function remains unresolved. Do inhibitory Galpha-subunits selectively modulate parasympathetic heart rate responses? Published findings using a variety of experimental approaches have implicated roles for Galphai2, Galphai3, and Galphao in parasympathetic signal transduction. We have compared in vivo different groups of mice with global genetic deletion of Gialpha1/Galphai3, Galphai2, and Galphao against littermate controls using implanted ECG telemetry. Significant resting tachycardia was observed in Galphai2(-/-) and Galphao(-/-) mice compared with control and Galphai1(-/-)/Galphai3(-/-) mice (P < 0.05). Loss of diurnal heart rate variation was seen exclusively in Galphao(-/-) mice. Using heart rate variability (HRV) analysis, compared with littermate controls (4.02 ms2 +/- 1.17; n = 6, Galphai2(-/-)) mice have a selective attenuation of high-frequency (HF) power (0.73 ms2 +/- 0.31; n = 5, P < 0.05). Galphai1(-/-)/Galphai3(-/-) and Galphao(-/-) cohorts have nonsignificant changes in HF power. Galphao(-/-) mice have a different basal HRV signature. The observed HRV phenotype in Galphai2(-/-) mice was qualitatively similar to atropine (1 mg/kg)-treated controls [and mice treated with the GIRK channel blocker tertiapinQ (0.05 mg/kg)]. Maximal cardioinhibitory response to the M(2)-receptor agonist carbachol (0.5 mg/kg) compared with basal heart rate was attenuated in Galphai2(-/-) mice (0.08 +/- 0.04; n = 6) compared to control (0.27 +/- 0.04; n = 7 P < 0.05). Our data suggest a selective defect of parasympathetic heart rate modulation in mice with Galphai2 deletion. Mice with Galphao deletion also have a defect in short-term heart rate dynamics, but this is qualitatively different to the effects of atropine, tertiapinQ, and Galphai2 deletion. In contrast, Galphai1 and Galphai3 do not appear to be essential for parasympathetic responses in vivo.
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Affiliation(s)
- Zia Zuberi
- British Heart Foundation, Laboratories and Department of Medicine, University College London, 5 University St., London, WC1E 6JJ, UK
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14
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Reduced troponin I phosphorylation and increased Ca(2+)-dependent ATP-consumption in triton X-skinned fiber preparations from Galphaq overexpressor mice. Mol Cell Biochem 2008; 314:133-41. [PMID: 18473122 DOI: 10.1007/s11010-008-9774-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 04/22/2008] [Indexed: 01/08/2023]
Abstract
Overexpression of the Galphaq-protein has been shown to result in hypertrophic and dilated cardiomyopathy. This study investigated Ca(2+ )sensitivity of tension and myosin-ATPase activity in skinned fiber preparations of male and female wildtype (WT; n = 12) and transgenic mice with a cardiac specific overexpression of the Galphaq-protein (Galphaq-OE; n = 11). In addition, the phosphorylation status of troponin I was measured. Ca(2+) sensitivity of tension was increased in Galphaq-OE with a significant reduction in the half-maximum Ca(2+) concentration (EC(50)) compared to WT. Similarly, Ca(2+) sensitivity of myosin ATPase activity was increased in Galphaq-OE when comparing Galphaq-OE to WT. Maximum Ca(2+)-dependent tension and ATPase activity were both enhanced in Galphaq-OE compared to WT littermates. Phosphorylation of troponin I was significantly reduced in Galphaq-OE compared to WT. In the above experiments, no gender specific differences were observed in either Gaq-OE or in WT. We conclude that, in mice, increased expression of the Galphaq-protein induces alterations of myofibrillar function and energy consumption, which are also characteristics of human heart failure. This may result from a decreased phosphorylation of troponin I in Galphaq-OE.
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15
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Muscarinic ACh receptor-mediated control of thalamic activity via G(q)/G (11)-family G-proteins. Pflugers Arch 2008; 456:1049-60. [PMID: 18350314 DOI: 10.1007/s00424-008-0473-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Revised: 01/16/2008] [Accepted: 02/07/2008] [Indexed: 12/25/2022]
Abstract
A genetic knock out was used to determine the specific contribution of G(q)/G(11)-family G-proteins to the function of thalamocortical relay (TC) neurons. Disruption of Galpha(q) function in a conditional forebrain-specific Galpha(q)/Galpha(11)-double-deficient mouse line (Galpha(q)/Galpha(11)(-/-) had no effects on the resting membrane potential (V (rest)) and the amplitude of the standing outward current (I (SO)). Stimulation of muscarinic acetylcholine (ACh) receptors (mAChR; muscarine, 50 microM) induced a decrease in I (SO) amplitude in wild-type mice (36 +/- 4%, n = 5), a constitutive Galpha(11)-deficient mouse line (Galpha(11)(-/-; 36 +/- 3%, n = 8), and Galpha(q)/Galpha(11)(-/-) (11 +/- 2%, n = 16). Current-clamp recordings revealed a muscarine-induced positive shift in V (rest) of 23 +/- 2 mV (n = 6), 18 +/- 5 mV (n = 5), and 2 +/- 1 mV (n = 9) in wild type, Galpha(11)(-/-), and Galpha(q)/Galpha(11)(-/-), respectively. This depolarization was associated with a change in TC neuron activity from burst to tonic firing in wild type and Galpha(11)(-/-), but not in Galpha(q)/Galpha(11)(-/-). The use of specific antibodies and of pharmacological agents with preferred affinity points to the contribution of m(1)AChR and m(3)AChR. In conclusion, we present two novel aspects of the physiology of the thalamocortical system by demonstrating that the depolarization of TC neurons, which is induced by the action of transmitters of ascending brainstem fibers, is governed roughly equally by both m(1)AChR and m(3)AChR and is transduced by Galpha(q) but not by Galpha(11).
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16
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Brunk I, Höltje M, von Jagow B, Winter S, Sternberg J, Blex C, Pahner I, Ahnert-Hilger G. Regulation of vesicular monoamine and glutamate transporters by vesicle-associated trimeric G proteins: new jobs for long-known signal transduction molecules. Handb Exp Pharmacol 2007:305-25. [PMID: 16722242 DOI: 10.1007/3-540-29784-7_15] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters of neurons and neuroendocrine cells are concentrated first in the cytosol and then in either small synaptic vesicles ofpresynaptic terminals or in secretory vesicles by the activity of specific transporters of the plasma and the vesicular membrane, respectively. In the central nervous system the postsynaptic response depends--amongst other parameters-on the amount of neurotransmitter stored in a given vesicle. Neurotransmitter packets (quanta) vary over a wide range which may be also due to a regulation of vesicular neurotransmitter filling. Vesicular filling is regulated by the availability of transmitter molecules in the cytoplasm, the amount of transporter molecules and an electrochemical proton-mediated gradient over the vesicular membrane. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq. Galphao2 and Galphaq regulate vesicular monoamine transporter (VMAT) activities in brain and platelets, respectively. Galphao2 also regulates vesicular glutamate transporter (VGLUT) activity by changing its chloride dependence. It appears that the vesicular content activates the G protein, suggesting a signal transduction from the luminal site which might be mediated by a vesicular G protein-coupled receptor or as an alternative possibility by the transporter itself. Thus, G proteins control transmitter storage and thereby probablylink the regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- I Brunk
- AG Funktionelle Zellbiologie, Institut für Integrative Neuroanatomie, Centrum für Anatomie, Charité, Universitätsmedizin Berlin, Berlin, Germany
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17
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Dwyer DS, Dickson A. Neuroprotection and Enhancement of Neurite Outgrowth With Small Molecular Weight Compounds From Screens of Chemical Libraries. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 77:247-89. [PMID: 17178477 DOI: 10.1016/s0074-7742(06)77008-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Donard S Dwyer
- Department of Psychiatry, Louisiana State University Health Sciences Center Shreveport, Louisiana 71130, USA
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18
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Ahnert-Hilger G, Höltje M, Pahner I, Winter S, Brunk I. Regulation of vesicular neurotransmitter transporters. Rev Physiol Biochem Pharmacol 2004; 150:140-60. [PMID: 14517724 DOI: 10.1007/s10254-003-0020-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters are key molecules of neurotransmission. They are concentrated first in the cytosol and then in small synaptic vesicles of presynaptic terminals by the activity of specific neurotransmitter transporters of the plasma and the vesicular membrane, respectively. It has been shown that postsynaptic responses to single neurotransmitter packets vary over a wide range, which may be due to a regulation of vesicular neurotransmitter filling. Vesicular filling depends on the availability of transmitter molecules in the cytoplasm and the active transport into secretory vesicles relying on a proton gradient. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq, which regulate VMAT activities in brain and platelets, respectively, and may also be involved in the regulation of VGLUTs. It appears that the vesicular content activates the G protein, suggesting a signal transduction form the luminal site which might be mediated by a vesicular G-protein coupled receptor or, as an alternative, possibly by the transporter itself. These novel functions of G proteins in the control of transmitter storage may link regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- G Ahnert-Hilger
- Institut für Anatomie und Neurowissenschaftliches Zentrum der Charité, Humboldt-Universität zu Berlin, Philippstr. 12, 10115 Berlin, Germany.
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19
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Foerster K, Groner F, Matthes J, Koch WJ, Birnbaumer L, Herzig S. Cardioprotection specific for the G protein Gi2 in chronic adrenergic signaling through beta 2-adrenoceptors. Proc Natl Acad Sci U S A 2003; 100:14475-80. [PMID: 14612574 PMCID: PMC283616 DOI: 10.1073/pnas.1936026100] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two subtypes of beta-adrenoceptors, beta 1 and beta 2, mediate cardiac catecholamine effects. These two types differ qualitatively, e.g., regarding G protein coupling and calcium channel stimulation. Transgenic mice overexpressing human beta 2-adrenoceptors survive high-expression levels, unlike mice overexpressing beta 1-adrenoceptors. We examined the role of inhibitory Gi proteins, known to be activated by beta 2- but not beta 1-adrenoceptors, on the chronic effects of human beta 2-adrenoreceptor overexpression in transgenic mice. These mice were crossbred with mice where G alpha i2, a functionally important cardiac Gi alpha-subunit, was inactivated by targeted gene deletion. Survival of beta 2-adrenoreceptor transgenic mice was reduced by heterozygous inactivation of G alpha i2. Homozygous knockout/beta 2-adrenoreceptor transgenic mice died within 4 days after birth. Heterozygous knockout/beta 2-adrenoreceptor transgenic mice developed more pronounced cardiac hypertrophy and earlier heart failure compared with beta 2-adrenoreceptor transgenic mice. Single calcium-channel activity was strongly suppressed in heterozygous knockout/beta 2-adrenoreceptor transgenic mice. In cardiomyocytes from these mice, pertussis toxin treatment in vitro fully restored channel activity and enhanced channel activity in cells from homozygous G alpha i2 knockout animals. Cardiac G alpha i3 protein was increased in all G alpha i2 knockout mouse strains. Our results demonstrate that G alpha i2 takes an essential protective part in chronic signaling of overexpressed beta 2-adrenoceptors, leading to prolonged survival and delayed cardiac pathology. However, reduction of calcium-channel activity by beta 2-adrenoreceptor overexpression is due to a different pertussis-toxin-sensitive pathway, most likely by G alpha i3. This result indicates that subtype-specific signaling of beta 2-adrenoreceptor functionally bifurcates at the level of Gi, leading to different effects depending on the G alpha isoform.
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MESH Headings
- Animals
- Base Sequence
- Calcium Channels/metabolism
- DNA/genetics
- GTP-Binding Protein alpha Subunit, Gi2
- GTP-Binding Protein alpha Subunits, Gi-Go/deficiency
- GTP-Binding Protein alpha Subunits, Gi-Go/genetics
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Proteins/genetics
- GTP-Binding Proteins/metabolism
- Gene Expression
- Humans
- Ion Channel Gating/drug effects
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Pertussis Toxin/toxicity
- Proto-Oncogene Proteins/deficiency
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Signal Transduction
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Affiliation(s)
- Katharina Foerster
- Department of Pharmacology, University of Cologne, Gleueler Strasse 24, 50931 Cologne, Germany
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20
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Abstract
At sites of vascular injury, platelets come into contact with subendothelial collagen, which triggers their activation and the formation of a hemostatic plug. Besides glycoprotein Ib (GPIb) and alphaIIbbeta3 integrin, which indirectly interact with collagen via von Willebrand factor (VWF), several collagen receptors have been identified on platelets, most notably alpha2beta1 integrin and the immunoglobulin (Ig) superfamily member GPVI. Within the last few years, major advances have been made in understanding platelet-collagen interactions including the molecular cloning of GPVI, the generation of mouse strains lacking individual collagen receptors, and the development of collagen receptor-specific antibodies and synthetic peptides. It is now recognized that platelet adhesion to collagen requires prior activation of integrins through "inside-out" signals generated by GPVI and reinforced by released second-wave mediators adenosine diphosphate (ADP) and thromboxane A2. These developments have led to revision of the original "2-site, 2-step" model, which now places GPVI in a central position in the complex processes of platelet tethering, activation, adhesion, aggregation, degranulation, and procoagulant activity on collagen. This review discusses these recent developments and proposes possible mechanisms for how GPVI acts in concert with other receptors and signaling pathways to initiate hemostasis and arterial thrombosis.
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Affiliation(s)
- Bernhard Nieswandt
- Department of Vascular Biology, Rudolf Virchow Center for Experimental Biomedicine Versbacher, Würzburg, Germany.
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21
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Pahner I, Höltje M, Winter S, Takamori S, Bellocchio EE, Spicher K, Laake P, Nürnberg B, Ottersen OP, Ahnert-Hilger G, Nümberg B. Functional G-protein heterotrimers are associated with vesicles of putative glutamatergic terminals: implications for regulation of transmitter uptake. Mol Cell Neurosci 2003; 23:398-413. [PMID: 12837624 DOI: 10.1016/s1044-7431(03)00059-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Changes in the vesicular transmitter content modulate synaptic strength and may contribute to synaptic plasticity. Several transporters mediating transmitter uptake into small synaptic vesicles (SSVs) have been identified but their regulation is largely unknown. Here we show by quantitative immunoelectron microscopy that the heterotrimeric G-protein subunits Galphao(2), Galpha(q/11), Gbeta(2), and Ggamma(7) are associated with vesicle-containing areas in terminals of cerebellar parallel fibers. These terminals also contain the vesicular glutamate transporter 1 (VGLUT1). In contrast, SSVs of climbing fiber terminals that contain VGLUT2 express one of the Gbeta-subunits Gbeta(1), Gbeta(3), or Gbeta(4), Ggamma(7), and one Galpha-subunit, probably Galphao(2). Glutamate uptake into cerebellar SSVs was inhibited by more than 50% by GMppNp, an activator of G proteins. Thus, vesicle populations with different subtypes of vesicular glutamate transporters contain functional G proteins with distinct subunit profiles. Heterotrimeric G proteins may play an important role in the control of vesicular filling.
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Affiliation(s)
- Ingrid Pahner
- Institut für Anatomie/Neurowissenschaftliches Zentrum der Charité, Humboldt-Universität zu Berlin, Philippstrasse 12, D-10115 Berlin, Germany
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22
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Redd KJ, Oberdick J, McCoy J, Denker BM, Luo Y. Association and colocalization of G protein alpha subunits and Purkinje cell protein 2 (Pcp2) in mammalian cerebellum. J Neurosci Res 2002; 70:631-7. [PMID: 12424730 DOI: 10.1002/jnr.10460] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Previously, we have demonstrated a novel interaction between Galpha(o) protein and Purkinje cell protein-2 (Pcp2, also known as L7) in vitro and in transfected cells (Luo and Denker [1999] J. Biol. Chem. 274:10685-10688). Pcp2 is uniquely expressed in cerebellar Purkinje cells and in retinal bipolar neurons, and it may function as a cell-type specific modulator for G protein-mediated cell signaling. This interaction has been further evaluated in the present studies. Coimmunoprecipitation experiments reveal that Pcp2 associates with Galpha(o) in vivo in mouse cerebellum and eye extract. Pcp2 also associate with Galpha(i2) in the cerebellum. No detectable associations of Pcp2 with Galpha(z) and Galpha(q) subunits are observed. The association of Galpha(o) and Pcp2 is detected at postnatal day 1 (P1), and the association remains stable from day 3 (P3) until adulthood. Further, immunofluorescent double labeling and confocal microscopy suggest that Pcp2 and Galpha(o) are colocalized in the distal processes of cerebellar Purkinje cells including axonal endings and dendritic spines. Taken together, these findings indicate colocalization and association of Galpha(o) and Pcp2 in cerebellum and suggest a functional role in regions of synaptic activity.
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Affiliation(s)
- Kacy J Redd
- Department of Biological Sciences, University of Southern Mississippi, 2609 W. 4th Street, Hattiesburg, MS 39406-5018, USA
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23
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Functional specificity of G alpha q and G alpha 11 in the cholinergic and glutamatergic modulation of potassium currents and excitability in hippocampal neurons. J Neurosci 2002. [PMID: 11826096 DOI: 10.1523/jneurosci.22-03-00666.2002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In hippocampal and other cortical neurons, action potentials are followed by a slow afterhyperpolarization (sAHP) generated by the activation of small-conductance Ca(2+)-activated K(+) channels and controlling spike frequency adaptation. The corresponding current, the apamin-insensitive sI(AHP), is a well known target of modulation by different neurotransmitters, including acetylcholine (via M(3) receptors) and glutamate (via metabotropic glutamate receptor 5, mGluR(5)), in CA1 pyramidal neurons. The actions of muscarinic and mGluR agonists on sI(AHP) involve the activation of pertussis toxin-insensitive G-proteins. However, the pharmacological tools available so far did not permit the identification of the specific G-protein subtypes transducing the effects of M(3) and mGluR(5) on sI(AHP). In the present study, we used mice deficient in the Galpha(q) and Galpha(11) genes to investigate the specific role of these G-protein alpha subunits in the cholinergic and glutamatergic modulation of sI(AHP) in CA1 neurons. In mice lacking Galpha(q), the effects of muscarinic and glutamatergic agonists on sI(AHP) were nearly abolished, whereas beta-adrenergic agonists acting via Galpha(s) were still fully effective. Modulation of sI(AHP) by any of these agonists was instead unchanged in mice lacking Galpha(11). The additional depolarizing effects of muscarinic and glutamatergic agonists on CA1 neurons were preserved in mice lacking Galpha(q) or Galpha(11). Thus, Galpha(q), but not Galpha(11), mediates specifically the action of cholinergic and glutamatergic agonists on sI(AHP), without affecting the modulation of other currents. These results provide to our knowledge one of the first examples of the functional specificity of Galpha(q) and Galpha(11) in central neurons.
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24
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Nieswandt B, Bergmeier W, Eckly A, Schulte V, Ohlmann P, Cazenave JP, Zirngibl H, Offermanns S, Gachet C. Evidence for cross-talk between glycoprotein VI and Gi-coupled receptors during collagen-induced platelet aggregation. Blood 2001; 97:3829-35. [PMID: 11389023 DOI: 10.1182/blood.v97.12.3829] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Collagen-induced platelet aggregation is a complex process and involves synergistic action of integrins, immunoglobulin (Ig)-like receptors, G-protein-coupled receptors and their ligands, most importantly collagen itself, thromboxane A(2) (TXA(2)), and adenosine diphosphate (ADP). The precise role of each of these receptor systems in the overall processes of activation and aggregation, however, is still poorly defined. Among the collagen receptors expressed on platelets, glycoprotein (GP) VI has been identified to play a crucial role in collagen-induced activation. GPVI is associated with the FcRgamma chain, which serves as the signal transducing unit of the receptor complex. It is well known that clustering of GPVI by highly specific agonists results in platelet activation and irreversible aggregation, but it is unclear whether collagen has the same effect on the receptor. This study shows that platelets from Galphaq-deficient mice, despite their severely impaired response to collagen, normally aggregate on clustering of GPVI, suggesting this not to be the principal mechanism by which collagen activates platelets. On the other hand, dimerization of GPVI by a monoclonal antibody (JAQ1), which by itself did not induce aggregation, provided a sufficient stimulus to potentiate platelet responses to Gi-coupled, but not Gq-coupled, agonists. The combination of JAQ1 and adrenaline or ADP, but not serotonin, resulted in alpha(IIb)beta(3)-dependent aggregation that occurred without intracellular calcium mobilization and shape change in the absence of Galphaq or the P2Y(1) receptor. Together, these results provide evidence for a cross-talk between (dimerized) GPVI and Gi-coupled receptors during collagen-induced platelet aggregation. (Blood. 2001;97:3829-3835)
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Affiliation(s)
- B Nieswandt
- Department of Molecular Oncology, General Surgery, Witten/Herdecke University, Arrenbergerstrasse 20, 42117 Wuppertal, Germany.
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25
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Fukuhara S, Chikumi H, Gutkind JS. RGS-containing RhoGEFs: the missing link between transforming G proteins and Rho? Oncogene 2001; 20:1661-8. [PMID: 11313914 DOI: 10.1038/sj.onc.1204182] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- S Fukuhara
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-4340, USA
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26
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27
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Cowan CW, He W, Wensel TG. RGS proteins: lessons from the RGS9 subfamily. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2000; 65:341-59. [PMID: 11008492 DOI: 10.1016/s0079-6603(00)65009-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
RGS proteins enhance the time resolution of G protein signaling cascades by accelerating GTP hydrolysis of G alpha subunits of heterotrimeric G proteins. RGS9-1, a photoreceptor-specific RGS protein, is the first vertebrate member of this sizeable family whose physiological function in a well-defined G protein pathway has been identified. It is essential for normal subsecond recovery kinetics of the light responses in retinal photoreceptors. Understanding this role allows RGS9-1 to serve as a useful model for understanding how specificity and regulation of RGS function are achieved. In addition to the catalytic RGS domain, shared among all members of this family, RGS9-1 contains several other domains, which are also found in a closely related subset of RGS proteins, the RGS9 subfamily. One of these domains, the G gamma-like (GGL) domain, has been identified as the attachment site for G beta 5 proteins, which act as obligate subunits for this subfamily. Results from RGS9-1 and other subfamily members suggest that specificity is achieved by cell type-specific transcription, RNA processing, and G beta 5-dependent protein stabilization. In addition, membrane localization via specific targeting domains likely plays an important role.
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Affiliation(s)
- C W Cowan
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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ADP induces partial platelet aggregation without shape change and potentiates collagen-induced aggregation in the absence of Gαq. Blood 2000. [DOI: 10.1182/blood.v96.6.2134] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Platelets from Gαq knockout mice are unable to aggregate in response to physiological agonists like adenosine 5′-diphosphate (ADP), thromboxane A2, thrombin, or collagen, although shape change still occurs in response to all of these agonists except ADP. ADP-induced platelet aggregation results from simultaneous activation of the purinergic P2Y1receptor coupled to calcium mobilization and shape change and of a distinct P2 receptor, P2cyc, coupled through Gi to adenylyl cyclase inhibition, which is responsible for completion and amplification of the response. P2cyc could be the molecular target of the antithrombotic drug clopidogrel and the adenosine triphosphate (ATP) analogs AR-C69931MX, AR-C67085, and AR-C66096. The aim of the present study was to determine whether externally added ADP could still act through the Gi pathway in Gαq-deficient mouse platelets and thereby amplify the residual responses to agonists such as thrombin or collagen. It was found that (1) ADP and adrenaline still inhibited cyclic AMP accumulation in Gαq-deficient platelets; (2) both agonists restored collagen- but not thrombin-induced aggregation in these platelets; (3) the effects of ADP were selectively inhibited in vitro by the ATP analog AR-C69931MX and ex vivo by clopidogrel and hence were apparently mediated by the P2cyc receptor; and (4) high concentrations of ADP (100 μmol/L) induced aggregation without shape change in Gαq-deficient platelets through activation of P2cyc. Since adrenaline was not able to induce platelet aggregation even at high concentrations, we conclude that the effects of ADP mediated by P2cyc are not restricted to the inhibition of adenylyl cyclase through Gi2.
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ADP induces partial platelet aggregation without shape change and potentiates collagen-induced aggregation in the absence of Gαq. Blood 2000. [DOI: 10.1182/blood.v96.6.2134.h8002134_2134_2139] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Platelets from Gαq knockout mice are unable to aggregate in response to physiological agonists like adenosine 5′-diphosphate (ADP), thromboxane A2, thrombin, or collagen, although shape change still occurs in response to all of these agonists except ADP. ADP-induced platelet aggregation results from simultaneous activation of the purinergic P2Y1receptor coupled to calcium mobilization and shape change and of a distinct P2 receptor, P2cyc, coupled through Gi to adenylyl cyclase inhibition, which is responsible for completion and amplification of the response. P2cyc could be the molecular target of the antithrombotic drug clopidogrel and the adenosine triphosphate (ATP) analogs AR-C69931MX, AR-C67085, and AR-C66096. The aim of the present study was to determine whether externally added ADP could still act through the Gi pathway in Gαq-deficient mouse platelets and thereby amplify the residual responses to agonists such as thrombin or collagen. It was found that (1) ADP and adrenaline still inhibited cyclic AMP accumulation in Gαq-deficient platelets; (2) both agonists restored collagen- but not thrombin-induced aggregation in these platelets; (3) the effects of ADP were selectively inhibited in vitro by the ATP analog AR-C69931MX and ex vivo by clopidogrel and hence were apparently mediated by the P2cyc receptor; and (4) high concentrations of ADP (100 μmol/L) induced aggregation without shape change in Gαq-deficient platelets through activation of P2cyc. Since adrenaline was not able to induce platelet aggregation even at high concentrations, we conclude that the effects of ADP mediated by P2cyc are not restricted to the inhibition of adenylyl cyclase through Gi2.
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