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Ubeysinghe S, Kankanamge D, Thotamune W, Wijayaratna D, Mohan TM, Karunarathne A. Spatiotemporal Optical Control of Gαq-PLCβ Interactions. ACS Synth Biol 2024; 13:242-258. [PMID: 38092428 DOI: 10.1021/acssynbio.3c00490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2023]
Abstract
Cells experience time-varying and spatially heterogeneous chemokine signals in vivo, activating cell surface proteins including G protein-coupled receptors (GPCRs). The Gαq pathway activation by GPCRs is a major signaling axis with broad physiological and pathological significance. Compared with other Gα members, GαqGTP activates many crucial effectors, including PLCβ (Phospholipase Cβ) and Rho GEFs (Rho guanine nucleotide exchange factors). PLCβ regulates many key processes, such as hematopoiesis, synaptogenesis, and cell cycle, and is therefore implicated in terminal-debilitating diseases, including cancer, epilepsy, Huntington's Disease, and Alzheimer's Disease. However, due to a lack of genetic and pharmacological tools, examining how the dynamic regulation of PLCβ signaling controls cellular physiology has been difficult. Since activated PLCβ induces several abrupt cellular changes, including cell morphology, examining how the other pathways downstream of Gq-GPCRs contribute to the overall signaling has also been difficult. Here we show the engineering, validation, and application of a highly selective and efficient optogenetic inhibitor (Opto-dHTH) to completely disrupt GαqGTP-PLCβ interactions reversibly in user-defined cellular-subcellular regions on optical command. Using this newly gained PLCβ signaling control, our data indicate that the molecular competition between RhoGEFs and PLCβ for GαqGTP determines the potency of Gq-GPCR-governed directional cell migration.
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Affiliation(s)
- Sithurandi Ubeysinghe
- Department of Chemistry, Saint Louis University, St. Louis, Missouri 63103, United States
| | - Dinesh Kankanamge
- Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Waruna Thotamune
- Department of Chemistry, Saint Louis University, St. Louis, Missouri 63103, United States
| | - Dhanushan Wijayaratna
- Department of Chemistry, Saint Louis University, St. Louis, Missouri 63103, United States
| | - Thomas M Mohan
- Department of Chemistry, Saint Louis University, St. Louis, Missouri 63103, United States
| | - Ajith Karunarathne
- Department of Chemistry, Saint Louis University, St. Louis, Missouri 63103, United States
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Rysiewicz B, Błasiak E, Mystek P, Dziedzicka-Wasylewska M, Polit A. Beyond the G protein α subunit: investigating the functional impact of other components of the Gαi 3 heterotrimers. Cell Commun Signal 2023; 21:279. [PMID: 37817242 PMCID: PMC10566112 DOI: 10.1186/s12964-023-01307-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 09/05/2023] [Indexed: 10/12/2023] Open
Abstract
BACKGROUND Specific interactions between G protein-coupled receptors (GPCRs) and G proteins play a key role in mediating signaling events. While there is little doubt regarding receptor preference for Gα subunits, the preferences for specific Gβ and Gγ subunits and the effects of different Gβγ dimer compositions on GPCR signaling are poorly understood. In this study, we aimed to investigate the subcellular localization and functional response of Gαi3-based heterotrimers with different combinations of Gβ and Gγ subunits. METHODS Live-cell imaging microscopy and colocalization analysis were used to investigate the subcellular localization of Gαi3 in combination with Gβ1 or Gβ2 heterotrimers, along with representative Gγ subunits. Furthermore, fluorescence lifetime imaging microscopy (FLIM-FRET) was used to investigate the nanoscale distribution of Gαi3-based heterotrimers in the plasma membrane, specifically with the dopamine D2 receptor (D2R). In addition, the functional response of the system was assessed by monitoring intracellular cAMP levels and conducting bioinformatics analysis to further characterize the heterotrimer complexes. RESULTS Our results show that Gαi3 heterotrimers mainly localize to the plasma membrane, although the degree of colocalization is influenced by the accompanying Gβ and Gγ subunits. Heterotrimers containing Gβ2 showed slightly lower membrane localization compared to those containing Gβ1, but certain combinations, such as Gαi3β2γ8 and Gαi3β2γ10, deviated from this trend. Examination of the spatial arrangement of Gαi3 in relation to D2R and of changes in intracellular cAMP level showed that the strongest functional response is observed for those trimers for which the distance between the receptor and the Gα subunit is smallest, i.e. complexes containing Gβ1 and Gγ8 or Gγ10 subunit. Deprivation of Gαi3 lipid modifications resulted in a significant decrease in the amount of protein present in the cell membrane, but did not always affect intracellular cAMP levels. CONCLUSION Our studies show that the composition of G protein heterotrimers has a significant impact on the strength and specificity of GPCR-mediated signaling. Different heterotrimers may exhibit different conformations, which further affects the interactions of heterotrimers and GPCRs, as well as their interactions with membrane lipids. This study contributes to the understanding of the complex signaling mechanisms underlying GPCR-G-protein interactions and highlights the importance of the diversity of Gβ and Gγ subunits in G-protein signaling pathways. Video Abstract.
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Affiliation(s)
- Beata Rysiewicz
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Ewa Błasiak
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Paweł Mystek
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Marta Dziedzicka-Wasylewska
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland.
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Ubeysinghe S, Kankanamge D, Thotamune W, Wijayaratna D, Mohan TM, Karunarathne A. Spatiotemporal optical control of Gαq-PLCβ interactions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552801. [PMID: 37609229 PMCID: PMC10441412 DOI: 10.1101/2023.08.10.552801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Cells experience time-varying and spatially heterogeneous chemokine signals in vivo, activating cell surface proteins, including G protein-coupled receptors (GPCRs). The Gαq pathway activation by GPCRs is a major signaling axis with a broad physiological and pathological significance. Compared to other Gα members, GαqGTP activates many crucial effectors, including PLCβ (Phospholipase Cβ) and Rho GEFs (Rho guanine nucleotide exchange factors). PLCβ regulates many key processes, such as hematopoiesis, synaptogenesis, and cell cycle, and is therefore implicated in terminal - debilitating diseases, including cancer, epilepsy, Huntington's Disease, and Alzheimer's Disease. However, due to a lack of genetic and pharmacological tools, examining how the dynamic regulation of PLCβ signaling controls cellular physiology has been difficult. Since activated PLCβ induces several abrupt cellular changes, including cell morphology, examining how the other pathways downstream of Gq-GPCRs contribute to the overall signaling has also been difficult. Here we show the engineering, validation, and application of a highly selective and efficient optogenetic inhibitor (Opto-dHTH) to completely disrupt GαqGTP-PLCβ interactions reversibly in user-defined cellular-subcellular regions on optical command. Using this newly gained PLCβ signaling control, our data indicate that the molecular competition between RhoGEFs and PLCβ for GαqGTP determines the potency of Gq-GPCR-governed directional cell migration.
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4
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Su X, Pang YT, Li W, Gumbart JC, Kelley J, Torres M. N-terminal intrinsic disorder is an ancestral feature of Gγ subunits that influences the balance between different Gβγ signaling axes in yeast. J Biol Chem 2023; 299:104947. [PMID: 37354971 PMCID: PMC10393545 DOI: 10.1016/j.jbc.2023.104947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/02/2023] [Accepted: 06/16/2023] [Indexed: 06/26/2023] Open
Abstract
Activated G protein-coupled receptors promote the dissociation of heterotrimeric G proteins into Gα and Gβγ subunits that bind to effector proteins to drive intracellular signaling responses. In yeast, Gβγ subunits coordinate the simultaneous activation of multiple signaling axes in response to mating pheromones, including MAP kinase (MAPK)-dependent transcription, cell polarization, and cell cycle arrest responses. The Gγ subunit in this complex contains an N-terminal intrinsically disordered region that governs Gβγ-dependent signal transduction in yeast and mammals. Here, we demonstrate that N-terminal intrinsic disorder is likely an ancestral feature that has been conserved across different Gγ subtypes and organisms. To understand the functional contribution of structural disorder in this region, we introduced precise point mutations that produce a stepwise disorder-to-order transition in the N-terminal tail of the canonical yeast Gγ subunit, Ste18. Mutant tail structures were confirmed using circular dichroism and molecular dynamics and then substituted for the wildtype gene in yeast. We find that increasing the number of helix-stabilizing mutations, but not isometric mutation controls, has a negative and proteasome-independent effect on Ste18 protein levels as well as a differential effect on pheromone-induced levels of active MAPK/Fus3, but not MAPK/Kss1. When expressed at wildtype levels, we further show that mutants with an alpha-helical N terminus exhibit a counterintuitive shift in Gβγ signaling that reduces active MAPK/Fus3 levels whilst increasing cell polarization and cell cycle arrest. These data reveal a role for Gγ subunit intrinsically disordered regions in governing the balance between multiple Gβγ signaling axes.
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Affiliation(s)
- Xinya Su
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Yui Tik Pang
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Wei Li
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA; Southeast Center for Mathematics and Biology, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - J C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Joshua Kelley
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine, USA
| | - Matthew Torres
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA; Southeast Center for Mathematics and Biology, Georgia Institute of Technology, Atlanta, Georgia, USA.
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Tennakoon M, Thotamune W, Payton JL, Karunarathne A. CaaX-motif adjacent residues control G protein prenylation under suboptimal conditions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.04.547731. [PMID: 37461501 PMCID: PMC10349941 DOI: 10.1101/2023.07.04.547731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
Prenylation is a universal and irreversible post-translational modification that supports membrane interactions of proteins involved in various cellular processes, including migration, proliferation, and survival. Thus, dysregulation of prenylation contributes to multiple disorders, including cancers, vascular diseases, and neurodegenerative diseases. During prenylation, prenyltransferase enzymes tether metabolically produced isoprenoid lipids to proteins via a thioether linkage. Pharmacological inhibition of the lipid synthesis pathway by statins has long been a therapeutic approach to control hyperlipidemia. Building on our previous finding that statins inhibit membrane association of G protein γ (Gγ) in a subtype-dependent manner, we investigated the molecular reasoning for this differential. We examined the prenylation efficacy of carboxy terminus (Ct) mutated Gγ in cells exposed to Fluvastatin and prenyl transferase inhibitors and monitored the subcellular localization of fluorescently tagged Gγ subunits and their mutants using live-cell confocal imaging. Reversible optogenetic unmasking-masking of Ct residues was used to probe their contribution to the prenylation process and membrane interactions of the prenylated proteins. Our findings suggest that specific Ct residues regulate membrane interactions of the Gγ polypeptide statin sensitivity, and prenylation efficacy. Our results also show that a few hydrophobic and charged residues at the Ct are crucial determinants of a protein's prenylation ability, especially under suboptimal conditions. Given the cell and tissue-specific expression of different Gγ subtypes, our findings explain how and why statins differentially perturb heterotrimeric G protein signaling in specific cells and tissues. Our results may provide molecular reasoning for repurposing statins as Ras oncogene inhibitors and the failure of using prenyltransferase inhibitors in cancer treatment.
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Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry, Saint Louis University, Saint Louis, MO 63103, USA
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
- Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, MO 63103, USA
| | - Waruna Thotamune
- Department of Chemistry, Saint Louis University, Saint Louis, MO 63103, USA
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
- Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, MO 63103, USA
| | - John L. Payton
- Department of Chemistry, Kenyon College, Gambier, Ohio 43022, USA
| | - Ajith Karunarathne
- Department of Chemistry, Saint Louis University, Saint Louis, MO 63103, USA
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
- Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, MO 63103, USA
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Kankanamge D, Tennakoon M, Karunarathne A, Gautam N. G protein gamma subunit, a hidden master regulator of GPCR signaling. J Biol Chem 2022; 298:102618. [PMID: 36272647 PMCID: PMC9678972 DOI: 10.1016/j.jbc.2022.102618] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 11/21/2022] Open
Abstract
Heterotrimeric G proteins (αβγ subunits) that are activated by G protein-coupled receptors (GPCRs) mediate the biological responses of eukaryotic cells to extracellular signals. The α subunits and the tightly bound βγ subunit complex of G proteins have been extensively studied and shown to control the activity of effector molecules. In contrast, the potential roles of the large family of γ subunits have been less studied. In this review, we focus on present knowledge about these proteins. Induced loss of individual γ subunit types in animal and plant models result in strikingly distinct phenotypes indicating that γ subtypes play important and specific roles. Consistent with these findings, downregulation or upregulation of particular γ subunit types result in various types of cancers. Clues about the mechanistic basis of γ subunit function have emerged from imaging the dynamic behavior of G protein subunits in living cells. This shows that in the basal state, G proteins are not constrained to the plasma membrane but shuttle between membranes and on receptor activation βγ complexes translocate reversibly to internal membranes. The translocation kinetics of βγ complexes varies widely and is determined by the membrane affinity of the associated γ subtype. On translocating, some βγ complexes act on effectors in internal membranes. The variation in translocation kinetics determines differential sensitivity and adaptation of cells to external signals. Membrane affinity of γ subunits is thus a parsimonious and elegant mechanism that controls information flow to internal cell membranes while modulating signaling responses.
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Affiliation(s)
- Dinesh Kankanamge
- Department of Anesthesiology, Washington University School of Medicine, St Louis, Missouri, USA
| | - Mithila Tennakoon
- Department of Chemistry, St Louis University, St Louis, Missouri, USA
| | | | - N Gautam
- Department of Anesthesiology, Washington University School of Medicine, St Louis, Missouri, USA; Department of Genetics, Washington University School of Medicine, St Louis, Missouri, USA.
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7
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Xu X, Khater M, Wu G. The olfactory receptor OR51E2 activates ERK1/2 through the Golgi-localized Gβγ-PI3Kγ-ARF1 pathway in prostate cancer cells. Front Pharmacol 2022; 13:1009380. [PMID: 36313302 PMCID: PMC9606680 DOI: 10.3389/fphar.2022.1009380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 09/26/2022] [Indexed: 11/23/2022] Open
Abstract
The olfactory receptor OR51E2 is ectopically expressed in prostate tissues and regulates prostate cancer progression, but its function and regulation in oncogenic mitogen-activate protein kinase (MAPK) activation are poorly defined. Here we demonstrate that β-ionone, an OR51E2 agonist, dose-dependently activates extracellular signal-regulated kinases 1 and 2 (ERK1/2) in prostate cancer cells, with an EC50 value of approximate 20 μM and an efficiency comparable to other receptor agonists. We also find that CRISPR-Cas9-mediated knockout of Golgi-translocating Gγ9 subunit, phosphoinositide 3-kinase γ (PI3Kγ) and the small GTPase ADP-ribosylation factor 1 (ARF1), as well as pharmacological inhibition of Gβγ, PI3Kγ and Golgi-localized ARF1, each abolishes ERK1/2 activation by β-ionone. We further show that β-ionone significantly promotes ARF1 translocation to the Golgi and activates ARF1 that can be inhibited by Gγ9 and PI3Kγ depletion. Collectively, our data demonstrate that OR51E2 activates ERK1/2 through the Gβγ-PI3Kγ-ARF1 pathway that occurs spatially at the Golgi, and also provide important insights into MAPK hyper-activation in prostate cancer.
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McIntire WE. A model for how Gβγ couples Gα to GPCR. J Gen Physiol 2022; 154:213096. [PMID: 35333292 PMCID: PMC8961292 DOI: 10.1085/jgp.202112982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 02/28/2022] [Indexed: 11/20/2022] Open
Abstract
Representing ∼5% of the human genome, G-protein-coupled receptors (GPCRs) are a primary target for drug discovery; however, the molecular details of how they couple to heterotrimeric G protein subunits are incompletely understood. Here, I propose a hypothetical initial docking model for the encounter between GPCR and Gβγ that is defined by transient interactions between the cytosolic surface of the GPCR and the prenyl moiety and the tripeptide motif, asparagine-proline-phenylalanine (NPF), in the C-terminus of the Gγ subunit. Analysis of class A GPCRs reveals a conserved NPF binding site formed by the interaction of the TM1 and H8. Functional studies using differentially prenylated proteins and peptides further suggest that the intracellular hydrophobic core of the GPCR is a prenyl binding site. Upon binding TM1 and H8 of GPCRs, the propensity of the C-terminal region of Gγ to convert into an α helix allows it to extend into the hydrophobic core of the GPCR, facilitating the GPCR active state. Conservation of the NPF motif in Gγ isoforms and interacting residues in TM1 and H8 suggest that this is a general mechanism of GPCR-G protein signaling. Analysis of the rhodopsin dimer also suggests that Gγ-rhodopsin interactions may facilitate GPCR dimer transactivation.
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Affiliation(s)
- William E McIntire
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA
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9
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Tennakoon M, Senarath K, Kankanamge D, Chadee DN, Karunarathne A. A short C-terminal peptide in Gγ regulates Gβγ signaling efficacy. Mol Biol Cell 2021; 32:1446-1458. [PMID: 34106735 PMCID: PMC8351738 DOI: 10.1091/mbc.e20-11-0750] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 05/03/2021] [Accepted: 06/04/2021] [Indexed: 01/03/2023] Open
Abstract
G protein beta-gamma (Gβγ) subunits anchor to the plasma membrane (PM) through the carboxy-terminal (CT) prenyl group in Gγ. This interaction is crucial for the PM localization and functioning of Gβγ, allowing GPCR-G protein signaling to proceed. The diverse Gγ family has 12 members, and we have recently shown that the signaling efficacies of major Gβγ effectors are Gγ-type dependent. This dependency is due to the distinct series of membrane-interacting abilities of Gγ. However, the molecular process allowing for Gβγ subunits to exhibit a discrete and diverse range of Gγ-type-dependent membrane affinities is unclear and cannot be explained using only the type of prenylation. The present work explores the unique designs of membrane-interacting CT residues in Gγ as a major source for this Gγ-type-dependent Gβγ signaling. Despite the type of prenylation, the results show signaling efficacy at the PM, and associated cell behaviors of Gβγ are governed by crucially located specific amino acids in the five to six residue preprenylation region of Gγ. The provided molecular picture of Gγ-membrane interactions may explain how cells gain Gγ-type-dependent G protein-GPCR signaling as well as how Gβγ elicits selective signaling at various subcellular compartments.
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Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606
| | - Kanishka Senarath
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606
| | - Deborah N. Chadee
- Department of Biological Sciences, The University of Toledo, Toledo, OH 43606
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606
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10
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Copits BA, Gowrishankar R, O'Neill PR, Li JN, Girven KS, Yoo JJ, Meshik X, Parker KE, Spangler SM, Elerding AJ, Brown BJ, Shirley SE, Ma KKL, Vasquez AM, Stander MC, Kalyanaraman V, Vogt SK, Samineni VK, Patriarchi T, Tian L, Gautam N, Sunahara RK, Gereau RW, Bruchas MR. A photoswitchable GPCR-based opsin for presynaptic inhibition. Neuron 2021; 109:1791-1809.e11. [PMID: 33979635 PMCID: PMC8194251 DOI: 10.1016/j.neuron.2021.04.026] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 04/21/2021] [Accepted: 04/26/2021] [Indexed: 12/12/2022]
Abstract
Optical manipulations of genetically defined cell types have generated significant insights into the dynamics of neural circuits. While optogenetic activation has been relatively straightforward, rapid and reversible synaptic inhibition has proven more elusive. Here, we leveraged the natural ability of inhibitory presynaptic GPCRs to suppress synaptic transmission and characterize parapinopsin (PPO) as a GPCR-based opsin for terminal inhibition. PPO is a photoswitchable opsin that couples to Gi/o signaling cascades and is rapidly activated by pulsed blue light, switched off with amber light, and effective for repeated, prolonged, and reversible inhibition. PPO rapidly and reversibly inhibits glutamate, GABA, and dopamine release at presynaptic terminals. Furthermore, PPO alters reward behaviors in a time-locked and reversible manner in vivo. These results demonstrate that PPO fills a significant gap in the neuroscience toolkit for rapid and reversible synaptic inhibition and has broad utility for spatiotemporal control of inhibitory GPCR signaling cascades.
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Affiliation(s)
- Bryan A Copits
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA.
| | - Raaj Gowrishankar
- Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA
| | - Patrick R O'Neill
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA; Shirley and Stefan Hatos Center for Neuropharmacology, Semel Institute, Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA
| | - Jun-Nan Li
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Kasey S Girven
- Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA
| | - Judy J Yoo
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Xenia Meshik
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Kyle E Parker
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Skylar M Spangler
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Abigail J Elerding
- Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA
| | - Bobbie J Brown
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Sofia E Shirley
- Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA
| | - Kelly K L Ma
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Alexis M Vasquez
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - M Christine Stander
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Vani Kalyanaraman
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Sherri K Vogt
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Vijay K Samineni
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Tommaso Patriarchi
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, USA
| | - N Gautam
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Roger K Sunahara
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - Robert W Gereau
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA
| | - Michael R Bruchas
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA; Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA.
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Tennakoon M, Senarath K, Kankanamge D, Ratnayake K, Wijayaratna D, Olupothage K, Ubeysinghe S, Martins-Cannavino K, Hébert TE, Karunarathne A. Subtype-dependent regulation of Gβγ signalling. Cell Signal 2021; 82:109947. [PMID: 33582184 PMCID: PMC8026654 DOI: 10.1016/j.cellsig.2021.109947] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.
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Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kanishka Senarath
- Genetics and Molecular Biology Unit, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dhanushan Wijayaratna
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Koshala Olupothage
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Sithurandi Ubeysinghe
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | | | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA.
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12
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Khater M, Bryant CN, Wu G. Gβγ translocation to the Golgi apparatus activates ARF1 to spatiotemporally regulate G protein-coupled receptor signaling to MAPK. J Biol Chem 2021; 296:100805. [PMID: 34022220 PMCID: PMC8215300 DOI: 10.1016/j.jbc.2021.100805] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/11/2021] [Accepted: 05/18/2021] [Indexed: 01/01/2023] Open
Abstract
After activation of G protein-coupled receptors, G protein βγ dimers may translocate from the plasma membrane to the Golgi apparatus (GA). We recently report that this translocation activates extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) via PI3Kγ; however, how Gβγ-PI3Kγ activates the ERK1/2 pathway is unclear. Here, we demonstrate that chemokine receptor CXCR4 activates ADP-ribosylation factor 1 (ARF1), a small GTPase important for vesicle-mediated membrane trafficking. This activation is blocked by CRISPR-Cas9-mediated knockout of the GA-translocating Gγ9 subunit. Inducible targeting of different Gβγ dimers to the GA can directly activate ARF1. CXCR4 activation and constitutive Gβγ recruitment to the GA also enhance ARF1 translocation to the GA. We further demonstrate that pharmacological inhibition and CRISPR-Cas9-mediated knockout of PI3Kγ markedly inhibit CXCR4-mediated and Gβγ translocation-mediated ARF1 activation. We also show that depletion of ARF1 by siRNA and CRISPR-Cas9 and inhibition of GA-localized ARF1 activation abolish ERK1/2 activation by CXCR4 and Gβγ translocation to the GA and suppress prostate cancer PC3 cell migration and invasion. Collectively, our data reveal a novel function for Gβγ translocation to the GA to activate ARF1 and identify GA-localized ARF1 as an effector acting downstream of Gβγ-PI3Kγ to spatiotemporally regulate G protein-coupled receptor signaling to mitogen-activated protein kinases.
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Affiliation(s)
- Mostafa Khater
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Christian N Bryant
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Guangyu Wu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA.
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13
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Diversity of the Gβγ complexes defines spatial and temporal bias of GPCR signaling. Cell Syst 2021; 12:324-337.e5. [PMID: 33667409 DOI: 10.1016/j.cels.2021.02.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 12/09/2020] [Accepted: 02/04/2021] [Indexed: 01/04/2023]
Abstract
The signal transduction by G-protein-coupled receptors (GPCRs) is mediated by heterotrimeric G proteins composed from one of the 16 Gα subunits and the inseparable Gβγ complex assembled from a repertoire of 5 Gβ and 12 Gγ subunits. However, the functional role of compositional diversity in Gβγ complexes has been elusive. Using optical biosensors, we examined the function of all Gβγ combinations in living cells and uncovered two major roles of Gβγ diversity. First, we demonstrate that the identity of Gβγ subunits greatly influences the kinetics and efficacy of GPCR responses at the plasma membrane. Second, we show that different Gβγ combinations are selectively dispatched from the plasma membrane to various cellular organelles on a timescale from milliseconds to minutes. We describe the mechanisms regulating these processes and document their implications for GPCR signaling via various Gα subunits, thereby illustrating a role for the compositional diversity of G protein heterotrimers.
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14
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Khater M, Wei Z, Xu X, Huang W, Lokeshwar BL, Lambert NA, Wu G. G protein βγ translocation to the Golgi apparatus activates MAPK via p110γ-p101 heterodimers. J Biol Chem 2021; 296:100325. [PMID: 33493514 PMCID: PMC7949113 DOI: 10.1016/j.jbc.2021.100325] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/11/2021] [Accepted: 01/19/2021] [Indexed: 01/14/2023] Open
Abstract
The Golgi apparatus (GA) is a cellular organelle that plays a critical role in the processing of proteins for secretion. Activation of G protein-coupled receptors at the plasma membrane (PM) induces the translocation of G protein βγ dimers to the GA. However, the functional significance of this translocation is largely unknown. Here, we study PM-GA translocation of all 12 Gγ subunits in response to chemokine receptor CXCR4 activation and demonstrate that Gγ9 is a unique Golgi-translocating Gγ subunit. CRISPR-Cas9-mediated knockout of Gγ9 abolishes activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), two members of the mitogen-activated protein kinase family, by CXCR4. We show that chemically induced recruitment to the GA of Gβγ dimers containing different Gγ subunits activates ERK1/2, whereas recruitment to the PM is ineffective. We also demonstrate that pharmacological inhibition of phosphoinositide 3-kinase γ (PI3Kγ) and depletion of its subunits p110γ and p101 abrogate ERK1/2 activation by CXCR4 and Gβγ recruitment to the GA. Knockout of either Gγ9 or PI3Kγ significantly suppresses prostate cancer PC3 cell migration, invasion, and metastasis. Collectively, our data demonstrate a novel function for Gβγ translocation to the GA, via activating PI3Kγ heterodimers p110γ-p101, to spatiotemporally regulate mitogen-activated protein kinase activation by G protein-coupled receptors and ultimately control tumor progression.
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Affiliation(s)
- Mostafa Khater
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Zhe Wei
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Xin Xu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Wei Huang
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Bal L Lokeshwar
- Georgia Cancer Center, Augusta University, Augusta, Georgia, USA
| | - Nevin A Lambert
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Guangyu Wu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA.
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15
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Blue light-triggered photochemistry and cytotoxicity of retinal. Cell Signal 2020; 69:109547. [PMID: 31982549 DOI: 10.1016/j.cellsig.2020.109547] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 01/14/2020] [Accepted: 01/22/2020] [Indexed: 01/08/2023]
Abstract
The chemical- and photo- toxicity of chromophore retinal on cells have long been debated. Although we recently showed that retinal and blue light exposure interrupt cellular signaling, a comprehensive study examining molecular underpinnings of this perturbation and its consequences to cellular fate is lacking. Here, we report molecular evidence for blue light excited-retinal induced oxidative damage of polyunsaturated lipid anchors in membrane-interacting signaling molecules and DNA damage in cells using live-cell imaging and in vitro experimentation. The incurred molecular damage irreversibly disrupted subcellular localization of these molecules, a crucial criterion for their signaling. We further show retinal accumulation in lipid-bilayers of cell membranes could enhance the lifetime of retinal in cells. Comparative response-signatures suggest that retinal triggers reactions upon photoexcitation similar to photodynamic therapy agents and generate reactive oxygen species in cells. Additionally, data also shows that exposing retinal-containing cells to sunlight induces substantial cytotoxicity. Collectively, our results explain a likely in vivo mechanism and reaction conditions under which bio-available retinal in physiological light conditions damages cells.
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16
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Smrcka AV, Fisher I. G-protein βγ subunits as multi-functional scaffolds and transducers in G-protein-coupled receptor signaling. Cell Mol Life Sci 2019; 76:4447-4459. [PMID: 31435698 PMCID: PMC6842434 DOI: 10.1007/s00018-019-03275-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 08/05/2019] [Accepted: 08/12/2019] [Indexed: 02/08/2023]
Abstract
G-protein βγ subunits are key participants in G-protein signaling. These subunits facilitate interactions between receptors and G proteins that are critical for the G protein activation cycle at the plasma membrane. In addition, they play roles in directly transducing signals to an ever expanding range of downstream targets, including integral membrane and cytosolic proteins. Emerging data indicate that Gβγ may play additional roles at intracellular compartments including endosomes, the Golgi apparatus, and the nucleus. Here, we discuss the molecular and structural basis for their ability to coordinate this wide range of cellular activities.
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Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, 48104, USA.
| | - Isaac Fisher
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, 48104, USA
- Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, NY, 14629, USA
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17
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Mystek P, Rysiewicz B, Gregrowicz J, Dziedzicka-Wasylewska M, Polit A. Gγ and Gα Identity Dictate a G-Protein Heterotrimer Plasma Membrane Targeting. Cells 2019; 8:E1246. [PMID: 31614907 PMCID: PMC6829862 DOI: 10.3390/cells8101246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/10/2019] [Accepted: 10/11/2019] [Indexed: 12/18/2022] Open
Abstract
Heterotrimeric G-proteins along with G-protein-coupled receptors (GPCRs) regulate many biochemical functions by relaying the information from the plasma membrane to the inside of the cell. The lipid modifications of Gα and Gγ subunits, together with the charged regions on the membrane interaction surface, provide a peculiar pattern for various heterotrimeric complexes. In a previous study, we found that Gαs and Gαi3 prefer different types of membrane-anchor and subclass-specific lipid domains. In the present report, we examine the role of distinct Gγ subunits in the membrane localization and spatiotemporal dynamics of Gαs and Gαi3 heterotrimers. We characterized lateral diffusion and G-protein subunit interactions in living cells using fluorescence recovery after photobleaching (FRAP) microscopy and fluorescence resonance energy transfer (FRET) detected by fluorescence lifetime imaging microscopy (FLIM), respectively. The interaction of Gγ subunits with specific lipids was confirmed, and thus the modulation of heterotrimeric G-protein localization. However, the Gα subunit also modulates trimer localization, and so the membrane distribution of heterotrimeric G-proteins is not dependent on Gγ only.
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Affiliation(s)
- Paweł Mystek
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Beata Rysiewicz
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Jan Gregrowicz
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Marta Dziedzicka-Wasylewska
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
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18
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Optical approaches for single-cell and subcellular analysis of GPCR-G protein signaling. Anal Bioanal Chem 2019; 411:4481-4508. [PMID: 30927013 DOI: 10.1007/s00216-019-01774-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 03/05/2019] [Accepted: 03/08/2019] [Indexed: 01/05/2023]
Abstract
G protein-coupled receptors (GPCRs), G proteins, and their signaling associates are major signal transducers that control the majority of cellular signaling and regulate key biological functions including immune, neurological, cardiovascular, and metabolic processes. These pathways are targeted by over one-third of drugs on the market; however, the current understanding of their function is limited and primarily derived from cell-destructive approaches providing an ensemble of static, multi-cell information about the status and composition of molecules. Spatiotemporal behavior of molecules involved is crucial to understanding in vivo cell behaviors both in health and disease, and the advent of genetically encoded fluorescence proteins and small fluorophore-based biosensors has facilitated the mapping of dynamic signaling in cells with subcellular acuity. Since we and others have developed optogenetic methods to regulate GPCR-G protein signaling in single cells and subcellular regions using dedicated wavelengths, the desire to develop and adopt optogenetically amenable assays to measure signaling has motivated us to take a broader look at the available optical tools and approaches compatible with measuring single-cell and subcellular GPCR-G protein signaling. Here we review such key optical approaches enabling the examination of GPCR, G protein, secondary messenger, and downstream molecules such as kinase and lipid signaling in living cells. The methods reviewed employ both fluorescence and bioluminescence detection. We not only further elaborate the underlying principles of these sensors but also discuss the experimental criteria and limitations to be considered during their use in single-cell and subcellular signal mapping.
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19
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Abstract
G protein-coupled receptors (GPCRs) are the largest class of drug targets, largely owing to their druggability, diversity and physiological efficacy. Many drugs selectively target specific subtypes of GPCRs, but high specificity for individual GPCRs may not be desirable in complex multifactorial disease states in which multiple receptors may be involved. One approach is to target G protein subunits rather than the GPCRs directly. This approach has the potential to achieve broad efficacy by blocking pathways shared by multiple GPCRs. Additionally, because many GPCRs couple to multiple G protein signalling pathways, blocking specific G protein subunits can 'bias' GPCR signals by inhibiting only a subset of these signals. Molecules that target G protein α or βγ-subunits have been developed and show strong efficacy in multiple preclinical disease models and biased inhibition of G protein signalling. In this Review, we discuss the development and characterization of G protein α and βγ-subunit ligands and the preclinical evidence that this exciting new approach has potential for therapeutic efficacy in a number of indications, such as pain, thrombosis, asthma and heart failure.
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20
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Samaradivakara S, Kankanamge D, Senarath K, Ratnayake K, Karunarathne A. G protein γ (Gγ) subtype dependent targeting of GRK2 to M3 receptor by Gβγ. Biochem Biophys Res Commun 2018; 503:165-170. [PMID: 29864421 DOI: 10.1016/j.bbrc.2018.05.204] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 05/29/2018] [Indexed: 01/09/2023]
Abstract
Interactions of cytosolic G protein coupled receptor kinase 2 (GRK2) with activated G protein coupled receptors (GPCRs) induce receptor phosphorylation and desensitization. GRK2 is recruited to active M3-muscarinic receptors (M3R) with the participation of the receptor, Gαq and Gβγ. Since we have shown that signaling efficacy of Gβγ is governed by its Gγ subtype identity, the present study examined whether recruitment of GRK2 to M3R is also Gγ subtype dependent. To capture the dynamics of GRK2-recruitment concurrently with GPCR-G protein activation, we employed live cell confocal imaging and a novel assay based on Gβγ translocation. Data show that M3R activation-induced GRK2 recruitment is Gγ subtype dependent in which Gβγ dimers with low PM-affinity Gγ9 exhibited a two-fold higher GRK2-recruitment compared to high PM affinity Gγ3 expressing cells. Since 12-mammalian Gγ types exhibit a cell and tissue specific expressions and the PM-affinity of a Gγ is linked to its subtype identity, our results indicate a mechanism by which Gγ profile of a cell controls GRK2 signaling and GPCR desensitization.
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Affiliation(s)
- Saroopa Samaradivakara
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH, 43606, USA
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH, 43606, USA
| | - Kanishka Senarath
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH, 43606, USA
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH, 43606, USA
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH, 43606, USA.
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21
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Senarath K, Kankanamge D, Samaradivakara S, Ratnayake K, Tennakoon M, Karunarathne A. Regulation of G Protein βγ Signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2018; 339:133-191. [PMID: 29776603 DOI: 10.1016/bs.ircmb.2018.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Heterotrimeric guanine nucleotide-binding proteins (G proteins) deliver external signals to the cell interior, upon activation by the external signal stimulated G protein-coupled receptors (GPCRs).While the activated GPCRs control several pathways independently, activated G proteins control the vast majority of cellular and physiological functions, ranging from vision to cardiovascular homeostasis. Activated GPCRs dissociate GαGDPβγ heterotrimer into GαGTP and free Gβγ. Earlier, GαGTP was recognized as the primary signal transducer of the pathway and Gβγ as a passive signaling modality that facilitates the activity of Gα. However, Gβγ later found to regulate more number of pathways than GαGTP does. Once liberated from the heterotrimer, free Gβγ interacts and activates a diverse range of signaling regulators including kinases, lipases, GTPases, and ion channels, and it does not require any posttranslation modifications. Gβγ family consists of 48 members, which show cell- and tissue-specific expressions, and recent reports show that cells employ the subtype diversity in Gβγ to achieve desired signaling outcomes. In addition to activated GPCRs, which induce free Gβγ generation and the rate of GTP hydrolysis in Gα, which sequester Gβγ in the heterotrimer, terminating Gβγ signaling, additional regulatory mechanisms exist to regulate Gβγ activity. In this chapter, we discuss structure and function, subtype diversity and its significance in signaling regulation, effector activation, regulatory mechanisms as well as the disease relevance of Gβγ in eukaryotes.
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22
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Senarath K, Payton JL, Kankanamge D, Siripurapu P, Tennakoon M, Karunarathne A. Gγ identity dictates efficacy of Gβγ signaling and macrophage migration. J Biol Chem 2018; 293:2974-2989. [PMID: 29317505 DOI: 10.1074/jbc.ra117.000872] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 01/04/2018] [Indexed: 11/06/2022] Open
Abstract
G protein βγ subunit (Gβγ) is a major signal transducer and controls processes ranging from cell migration to gene transcription. Despite having significant subtype heterogeneity and exhibiting diverse cell- and tissue-specific expression levels, Gβγ is often considered a unified signaling entity with a defined functionality. However, the molecular and mechanistic basis of Gβγ's signaling specificity is unknown. Here, we demonstrate that Gγ subunits, bearing the sole plasma membrane (PM)-anchoring motif, control the PM affinity of Gβγ and thereby differentially modulate Gβγ effector signaling in a Gγ-specific manner. Both Gβγ signaling activity and the migration rate of macrophages are strongly dependent on the PM affinity of Gγ. We also found that the type of C-terminal prenylation and five to six pre-CaaX motif residues at the PM-interacting region of Gγ control the PM affinity of Gβγ. We further show that the overall PM affinity of the Gβγ pool of a cell type is a strong predictor of its Gβγ signaling-activation efficacy. A kinetic model encompassing multiple Gγ types and parameterized for empirical Gβγ behaviors not only recapitulated experimentally observed signaling of Gβγ, but also suggested a Gγ-dependent, active-inactive conformational switch for the PM-bound Gβγ, regulating effector signaling. Overall, our results unveil crucial aspects of signaling and cell migration regulation by Gγ type-specific PM affinities of Gβγ.
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Affiliation(s)
- Kanishka Senarath
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606
| | - John L Payton
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606
| | - Praneeth Siripurapu
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606
| | - Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio 43606.
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23
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Senarath K, Ratnayake K, Siripurapu P, Payton JL, Karunarathne A. Reversible G Protein βγ9 Distribution-Based Assay Reveals Molecular Underpinnings in Subcellular, Single-Cell, and Multicellular GPCR and G Protein Activity. Anal Chem 2016; 88:11450-11459. [PMID: 27778511 DOI: 10.1021/acs.analchem.6b02512] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Current assays to measure the activation of G protein coupled receptors (GPCRs) and G proteins are time-consuming, indirect, and expensive. Therefore, an efficient method which directly measures the ability of a ligand to govern GPCR-G protein interactions can help to understand the molecular underpinnings of the associated signaling. A live cell imaging-based approach is presented here to directly measure ligand-induced GPCR and G protein activity in real time. The number of active GPCRs governs G protein heterotrimer (αβγ) dissociation, thereby controlling the concentration of free βγ subunits. The described γ9 assay measures the GPCR activation-induced extent of the reversible βγ9 subunit exchange between the plasma membrane (PM) and internal membranes (IMs). Confocal microscopy-based γ9 assay quantitatively determines the concentration dependency of ligands on GPCR activation. Demonstrating the high-throughput screening (HTS) adaptability, the γ9 assay performed using an imaging plate reader measures the ligand-induced GPCR activation. This suggests that the γ9 assay can be employed to screen libraries of compounds for their ability to activate GPCRs. Together with subcellular optogenetics, the spatiotemporal sensitivity of the γ9 assay permits experimental determination of the limits of spatially restricted activation of GPCRs and G proteins in subcellular regions of single cells. This assay works effectively for GPCRs coupled to αi/o and αs heterotrimers, including light-sensitive GPCRs. In addition, computational modeling of experimental data from the assay is used to decipher intricate molecular details of the GPCR-G protein activation process. Overall, the γ9 assay provides a robust strategy for quantitative as well as qualitative determination of GPCR and G protein function on a single-cell, multicell, and subcellular level. This assay not only provides information about the inner workings of the signaling pathway, but it also strengthens GPCR deorphanization as well as drug discovery efforts.
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Affiliation(s)
- Kanishka Senarath
- Department of Chemistry and Biochemistry, The University of Toledo , Toledo, Ohio 43606, United States
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo , Toledo, Ohio 43606, United States
| | - Praneeth Siripurapu
- Department of Chemistry and Biochemistry, The University of Toledo , Toledo, Ohio 43606, United States
| | - John L Payton
- Department of Chemistry and Biochemistry, The University of Toledo , Toledo, Ohio 43606, United States
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo , Toledo, Ohio 43606, United States
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24
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Martin BR, Lambert NA. Activated G Protein Gαs Samples Multiple Endomembrane Compartments. J Biol Chem 2016; 291:20295-20302. [PMID: 27528603 DOI: 10.1074/jbc.m116.729731] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Indexed: 11/06/2022] Open
Abstract
Heterotrimeric G proteins are localized to the plasma membrane where they transduce extracellular signals to intracellular effectors. G proteins also act at intracellular locations, and can translocate between cellular compartments. For example, Gαs can leave the plasma membrane and move to the cell interior after activation. However, the mechanism of Gαs translocation and its intracellular destination are not known. Here we use bioluminescence resonance energy transfer (BRET) to show that after activation, Gαs rapidly associates with the endoplasmic reticulum, mitochondria, and endosomes, consistent with indiscriminate sampling of intracellular membranes from the cytosol rather than transport via a specific vesicular pathway. The primary source of Gαs for endosomal compartments is constitutive endocytosis rather than activity-dependent internalization. Recycling of Gαs to the plasma membrane is complete 25 min after stimulation is discontinued. We also show that an acylation-deacylation cycle is important for the steady-state localization of Gαs at the plasma membrane, but our results do not support a role for deacylation in activity-dependent Gαs internalization.
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Affiliation(s)
- Brent R Martin
- From the Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
| | - Nevin A Lambert
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
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Zheng M, Zhang X, Guo S, Zhang X, Min C, Cheon SH, Oak MH, Kim YR, Kim KM. Agonist-induced changes in RalA activities allows the prediction of the endocytosis of G protein-coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:77-90. [PMID: 26477566 DOI: 10.1016/j.bbamcr.2015.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 10/10/2015] [Accepted: 10/13/2015] [Indexed: 12/31/2022]
Abstract
GTP binding proteins are classified into two families: heterotrimeric large G proteins which are composed of three subunits, and one subunit of small G proteins. Roles of small G proteins in the intracellular trafficking of G protein-coupled receptors (GPCRs) were studied. Among various small G proteins tested, GTP-bound form (G23V) of RalA inhibited the internalization of dopamine D2 receptor independently of the previously reported downstream effectors of RalA, such as Ral-binding protein 1 and PLD. With high affinity for GRK2, active RalA inhibited the GPCR endocytosis by sequestering the GRK2 from receptors. When it was tested for several GPCRs including an endogenous GPCR, lysophosphatidic acid receptor 1, agonist-induced conversion of GTP-bound to GDP-bound RalA, which presumably releases the sequestered GRK2, was observed selectively with the GPCRs which have tendency to undergo endocytosis. Conversion of RalA from active to inactive state occurred by translocation of RGL, a guanine nucleotide exchange factor, from the plasma membrane to cytosol as a complex with Gβγ. These results suggest that agonist-induced Gβγ-mediated conversion of RalA from the GTP-bound form to the GDP-bound form could be a mechanism to facilitate agonist-induced internalization of GPCRs.
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Affiliation(s)
- Mei Zheng
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaohan Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Shuohan Guo
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaowei Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Chengchun Min
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Seung Hoon Cheon
- Department of Medicinal Chemistry, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Min-Ho Oak
- College of Pharmacy, Mokpo National University, Muan-gun, Jeollanamdo 534-729, Republic of Korea
| | - Young Ran Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea.
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26
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Giri L, Patel AK, Karunarathne WKA, Kalyanaraman V, Venkatesh KV, Gautam N. A G-protein subunit translocation embedded network motif underlies GPCR regulation of calcium oscillations. Biophys J 2015; 107:242-54. [PMID: 24988358 DOI: 10.1016/j.bpj.2014.05.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 05/06/2014] [Accepted: 05/13/2014] [Indexed: 11/24/2022] Open
Abstract
G-protein βγ subunits translocate reversibly from the plasma membrane to internal membranes on receptor activation. Translocation rates differ depending on the γ subunit type. There is limited understanding of the role of the differential rates of Gβγ translocation in modulating signaling dynamics in a cell. Bifurcation analysis of the calcium oscillatory network structure predicts that the translocation rate of a signaling protein can regulate the damping of system oscillation. Here, we examined whether the Gβγ translocation rate regulates calcium oscillations induced by G-protein-coupled receptor activation. Oscillations in HeLa cells expressing γ subunit types with different translocation rates were imaged and quantitated. The results show that differential Gβγ translocation rates can underlie the diversity in damping characteristics of calcium oscillations among cells. Mathematical modeling shows that a translocation embedded motif regulates damping of G-protein-mediated calcium oscillations consistent with experimental data. The current study indicates that such a motif may act as a tuning mechanism to design oscillations with varying damping patterns by using intracellular translocation of a signaling component.
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Affiliation(s)
- Lopamudra Giri
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Anilkumar K Patel
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - W K Ajith Karunarathne
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Vani Kalyanaraman
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - K V Venkatesh
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India.
| | - N Gautam
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Department of Genetics, Washington University School of Medicine, St. Louis, Missouri.
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27
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Malik S, deRubio RG, Trembley M, Irannejad R, Wedegaertner PB, Smrcka AV. G protein βγ subunits regulate cardiomyocyte hypertrophy through a perinuclear Golgi phosphatidylinositol 4-phosphate hydrolysis pathway. Mol Biol Cell 2015; 26:1188-98. [PMID: 25609085 PMCID: PMC4357516 DOI: 10.1091/mbc.e14-10-1476] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Gβγ regulation of the perinuclear Golgi PI4P pathway and a separate pathway at the PM is required for ET-1–stimulated hypertrophy, and the efficacy of Gβγ inhibition in preventing heart failure may be due, in part, to its blocking both of these pathways. We recently identified a novel GPCR-dependent pathway for regulation of cardiac hypertrophy that depends on Golgi phosphatidylinositol 4-phosphate (PI4P) hydrolysis by a specific isoform of phospholipase C (PLC), PLCε, at the nuclear envelope. How stimuli are transmitted from cell surface GPCRs to activation of perinuclear PLCε is not clear. Here we tested the role of G protein βγ subunits. Gβγ inhibition blocked ET-1–stimulated Golgi PI4P depletion in neonatal and adult ventricular myocytes. Blocking Gβγ at the Golgi inhibited ET-1–dependent PI4P depletion and nuclear PKD activation. Translocation of Gβγ to the Golgi stimulated perinuclear Golgi PI4P depletion and nuclear PKD activation. Finally, blocking Gβγ at the Golgi or PM blocked ET-1–dependent cardiomyocyte hypertrophy. These data indicate that Gβγ regulation of the perinuclear Golgi PI4P pathway and a separate pathway at the PM is required for ET-1–stimulated hypertrophy, and the efficacy of Gβγ inhibition in preventing heart failure maybe due in part to its blocking both these pathways.
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Affiliation(s)
- S Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - R G deRubio
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - M Trembley
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - R Irannejad
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158
| | - P B Wedegaertner
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - A V Smrcka
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
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28
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Karunarathne WKA, O'Neill PR, Gautam N. Subcellular optogenetics - controlling signaling and single-cell behavior. J Cell Sci 2014; 128:15-25. [PMID: 25433038 DOI: 10.1242/jcs.154435] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Variation in signaling activity across a cell plays a crucial role in processes such as cell migration. Signaling activity specific to organelles within a cell also likely plays a key role in regulating cellular functions. To understand how such spatially confined signaling within a cell regulates cell behavior, tools that exert experimental control over subcellular signaling activity are required. Here, we discuss the advantages of using optogenetic approaches to achieve this control. We focus on a set of optical triggers that allow subcellular control over signaling through the activation of G-protein-coupled receptors (GPCRs), receptor tyrosine kinases and downstream signaling proteins, as well as those that inhibit endogenous signaling proteins. We also discuss the specific insights with regard to signaling and cell behavior that these subcellular optogenetic approaches can provide.
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Affiliation(s)
- W K Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Patrick R O'Neill
- Department of Anesthesiology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Narasimhan Gautam
- Department of Anesthesiology, Washington University School of Medicine, St Louis, MO 63110, USA Department of Genetics, Washington University School of Medicine, St Louis, MO 63110, USA
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29
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O'Neill PR, Gautam N. Subcellular optogenetic inhibition of G proteins generates signaling gradients and cell migration. Mol Biol Cell 2014; 25:2305-14. [PMID: 24920824 PMCID: PMC4116304 DOI: 10.1091/mbc.e14-04-0870] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cells sense gradients of extracellular cues and generate polarized responses such as cell migration and neurite initiation. There is static information on the intracellular signaling molecules involved in these responses, but how they dynamically orchestrate polarized cell behaviors is not well understood. A limitation has been the lack of methods to exert spatial and temporal control over specific signaling molecules inside a living cell. Here we introduce optogenetic tools that act downstream of native G protein-coupled receptor (GPCRs) and provide direct control over the activity of endogenous heterotrimeric G protein subunits. Light-triggered recruitment of a truncated regulator of G protein signaling (RGS) protein or a Gβγ-sequestering domain to a selected region on the plasma membrane results in localized inhibition of G protein signaling. In immune cells exposed to spatially uniform chemoattractants, these optogenetic tools allow us to create reversible gradients of signaling activity. Migratory responses generated by this approach show that a gradient of active G protein αi and βγ subunits is sufficient to generate directed cell migration. They also provide the most direct evidence so for a global inhibition pathway triggered by Gi signaling in directional sensing and adaptation. These optogenetic tools can be applied to interrogate the mechanistic basis of other GPCR-modulated cellular functions.
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Affiliation(s)
- Patrick R O'Neill
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
| | - N Gautam
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110
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30
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Hille B, Dickson E, Kruse M, Falkenburger B. Dynamic metabolic control of an ion channel. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:219-47. [PMID: 24560147 DOI: 10.1016/b978-0-12-397897-4.00008-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G-protein-coupled receptors mediate responses to external stimuli in various cell types. We are interested in the modulation of KCNQ2/3 potassium channels by the Gq-coupled M1 muscarinic (acetylcholine) receptor (M1R). Here, we describe development of a mathematical model that incorporates all known steps along the M1R signaling cascade and accurately reproduces the macroscopic behavior we observe when KCNQ2/3 currents are inhibited following M1R activation. Gq protein-coupled receptors of the plasma membrane activate phospholipase C (PLC) which cleaves the minor plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into the second messengers diacylgycerol and inositol 1,4,5-trisphosphate, leading to calcium release, protein kinase C (PKC) activation, and PI(4,5)P2 depletion. Combining optical and electrical techniques with knowledge of relative abundance of each signaling component has allowed us to develop a kinetic model and determine that (i) M1R activation and M1R/Gβ interaction are fast; (ii) Gαq/Gβ separation and Gαq/PLC interaction have intermediate time constants; (iii) the amount of activated PLC limits the rate of KCNQ2/3 suppression; (iv) weak PLC activation can elicit robust calcium signals without net PI(4,5)P2 depletion or KCNQ2/3 channel inhibition; and (v) depletion of PI(4,5)P2, and not calcium/CaM or PKC-mediated phosphorylation, closes KCNQ2/3 potassium channels, thereby increasing neuronal excitability.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Eamonn Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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31
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Boto T, Alcorta E. Toward identifying specific roles for G-protein β and γ subunit variants in olfactory reception. Front Cell Neurosci 2013; 7:114. [PMID: 23882185 PMCID: PMC3713392 DOI: 10.3389/fncel.2013.00114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 06/28/2013] [Indexed: 11/25/2022] Open
Affiliation(s)
- Tamara Boto
- Departamento de Biologia Funcional (Genetica), Facultad de Medicina, Universidad de Oviedo Oviedo, Spain ; Department of Neuroscience, The Scripps Research Institute Jupiter, FL, USA
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