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Garcia-Marcos M. Complementary biosensors reveal different G-protein signaling modes triggered by GPCRs and non-receptor activators. eLife 2021; 10:65620. [PMID: 33787494 PMCID: PMC8034979 DOI: 10.7554/elife.65620] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 03/30/2021] [Indexed: 01/14/2023] Open
Abstract
It has become evident that activation of heterotrimeric G-proteins by cytoplasmic proteins that are not G-protein-coupled receptors (GPCRs) plays a role in physiology and disease. Despite sharing the same biochemical guanine nucleotide exchange factor (GEF) activity as GPCRs in vitro, the mechanisms by which these cytoplasmic proteins trigger G-protein-dependent signaling in cells have not been elucidated. Heterotrimeric G-proteins can give rise to two active signaling species, Gα-GTP and dissociated Gβγ, with different downstream effectors, but how non-receptor GEFs affect the levels of these two species in cells is not known. Here, a systematic comparison of GPCRs and three unrelated non-receptor proteins with GEF activity in vitro (GIV/Girdin, AGS1/Dexras1, and Ric-8A) revealed high divergence in their contribution to generating Gα-GTP and free Gβγ in cells directly measured with live-cell biosensors. These findings demonstrate fundamental differences in how receptor and non-receptor G-protein activators promote signaling in cells despite sharing similar biochemical activities in vitro.
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Affiliation(s)
- Mikel Garcia-Marcos
- Department of Biochemistry, Boston University School of Medicine, Boston, United States
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Kask K, Tikker L, Ruisu K, Lulla S, Oja EM, Meier R, Raid R, Velling T, Tõnissoo T, Pooga M. Targeted deletion of RIC8A in mouse neural precursor cells interferes with the development of the brain, eyes, and muscles. Dev Neurobiol 2018; 78:374-390. [PMID: 29380551 DOI: 10.1002/dneu.22578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 01/18/2018] [Accepted: 01/18/2018] [Indexed: 11/11/2022]
Abstract
Autosomal recessive disorders such as Fukuyama congenital muscular dystrophy, Walker-Warburg syndrome, and the muscle-eye-brain disease are characterized by defects in the development of patient's brain, eyes, and skeletal muscles. These syndromes are accompanied by brain malformations like type II lissencephaly in the cerebral cortex with characteristic overmigrations of neurons through the breaches of the pial basement membrane. The signaling pathways activated by laminin receptors, dystroglycan and integrins, control the integrity of the basement membrane, and their malfunctioning may underlie the pathologies found in the rise of defects reminiscent of these syndromes. Similar defects in corticogenesis and neuromuscular disorders were found in mice when RIC8A was specifically removed from neural precursor cells. RIC8A regulates a subset of G-protein α subunits and in several model organisms, it has been reported to participate in the control of cell division, signaling, and migration. Here, we studied the role of RIC8A in the development of the brain, muscles, and eyes of the neural precursor-specific conditional Ric8a knockout mice. The absence of RIC8A severely affected the attachment and positioning of radial glial processes, Cajal-Retzius' cells, and the arachnoid trabeculae, and these mice displayed additional defects in the lens, skeletal muscles, and heart development. All the discovered defects might be linked to aberrancies in cell adhesion and migration, suggesting that RIC8A has a crucial role in the regulation of cell-extracellular matrix interactions and that its removal leads to the phenotype characteristic to type II lissencephaly-associated diseases. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 374-390, 2018.
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Affiliation(s)
- Keiu Kask
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Laura Tikker
- Department of Biosciences, University of Helsinki, P.O. Box 56, Viikinkaari 9, FIN-00014, Helsinki, Finland
| | - Katrin Ruisu
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Sirje Lulla
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Eva-Maria Oja
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Riho Meier
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Raivo Raid
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Teet Velling
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Tambet Tõnissoo
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia
| | - Margus Pooga
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St, Tartu, 51010, Estonia.,Institute of Technology, University of Tartu, Nooruse 1, Tartu, 50411, Estonia
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Garcia-Marcos M, Ghosh P, Farquhar MG. GIV/Girdin transmits signals from multiple receptors by triggering trimeric G protein activation. J Biol Chem 2015; 290:6697-704. [PMID: 25605737 DOI: 10.1074/jbc.r114.613414] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of trimeric G proteins has been traditionally viewed as the exclusive job of G protein-coupled receptors (GPCRs). This view has been challenged by the discovery of non-receptor activators of trimeric G proteins. Among them, GIV (a.k.a. Girdin) is the first for which a guanine nucleotide exchange factor (GEF) activity has been unequivocally associated with a well defined motif. Here we discuss how GIV assembles alternative signaling pathways by sensing cues from various classes of surface receptors and relaying them via G protein activation. We also describe the dysregulation of this mechanism in disease and how its targeting holds promise for novel therapeutics.
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Affiliation(s)
- Mikel Garcia-Marcos
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118 and
| | | | - Marilyn G Farquhar
- Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093-0651
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