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Jang W, Senarath K, Feinberg G, Lu S, Lambert NA. Visualization of endogenous G proteins on endosomes and other organelles. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.05.583500. [PMID: 38496652 PMCID: PMC10942389 DOI: 10.1101/2024.03.05.583500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Classical G protein-coupled receptor (GPCR) signaling takes place in response to extracellular stimuli and involves receptors and heterotrimeric G proteins located at the plasma membrane. It has recently been established that GPCR signaling can also take place from intracellular membrane compartments, including endosomes that contain internalized receptors and ligands. While the mechanisms of GPCR endocytosis are well understood, it is not clear how well internalized receptors are supplied with G proteins. To address this gap we use gene editing, confocal microscopy, and bioluminescence resonance energy transfer to study the distribution and trafficking of endogenous G proteins. We show here that constitutive endocytosis is sufficient to supply newly internalized endocytic vesicles with 20-30% of the G protein density found at the plasma membrane. We find that G proteins are present on early, late, and recycling endosomes, are abundant on lysosomes, but are virtually undetectable on the endoplasmic reticulum, mitochondria, and the medial Golgi apparatus. Receptor activation does not change heterotrimer abundance on endosomes. Our findings provide a subcellular map of endogenous G protein distribution, suggest that G proteins may be partially excluded from nascent endocytic vesicles, and are likely to have implications for GPCR signaling from endosomes and other intracellular compartments.
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Liu C, Jiao B, Wang P, Zhang B, Gao J, Li D, Xie X, Yao Y, Yan L, Qin Z, Liu P, Ren R. GOLGA7 is essential for NRAS trafficking from the Golgi to the plasma membrane but not for its palmitoylation. Cell Commun Signal 2024; 22:98. [PMID: 38317235 PMCID: PMC10845536 DOI: 10.1186/s12964-024-01498-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/21/2024] [Indexed: 02/07/2024] Open
Abstract
NRAS mutations are most frequently observed in hematological malignancies and are also common in some solid tumors such as melanoma and colon cancer. Despite its pivotal role in oncogenesis, no effective therapies targeting NRAS has been developed. Targeting NRAS localization to the plasma membrane (PM) is a promising strategy for cancer therapy, as its signaling requires PM localization. However, the process governing NRAS translocation from the Golgi apparatus to the PM after lipid modification remains elusive. This study identifies GOLGA7 as a crucial factor controlling NRAS' PM translocation, demonstrating that its depletion blocks NRAS, but not HRAS, KRAS4A and KRAS4B, translocating to PM. GOLGA7 is known to stabilize the palmitoyltransferase ZDHHC9 for NRAS and HRAS palmitoylation, but we found that GOLGA7 depletion does not affect NRAS' palmitoylation level. Further studies show that loss of GOLGA7 disrupts NRAS anterograde trafficking, leading to its cis-Golgi accumulation. Remarkably, depleting GOLGA7 effectively inhibits cell proliferation in multiple NRAS-mutant cancer cell lines and attenuates NRASG12D-induced oncogenic transformation in vivo. These findings elucidate a specific intracellular trafficking route for NRAS under GOLGA7 regulation, highlighting GOLGA7 as a promising therapeutic target for NRAS-driven cancers.
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Affiliation(s)
- Chenxuan Liu
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Bo Jiao
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peihong Wang
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Baoyuan Zhang
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jiaming Gao
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Donghe Li
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xi Xie
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yunying Yao
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lei Yan
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhenghong Qin
- Laboratory of Aging and Nervous Diseases, Department of Pharmacology, College of Pharmaceutical Science, Soochow University, Suzhou, 215123, China
| | - Ping Liu
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Ruibao Ren
- Shanghai Institute of Hematology, State Key Laboratory for Medical Genomics, Collaborative Innovation Center of Hematology, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
- International Center for Aging and Cancer, Hainan Medical College, Haikou, Hainan Province, China.
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Tennakoon M, Thotamune W, Payton JL, Karunarathne A. CaaX-motif-adjacent residues influence G protein gamma (Gγ) prenylation under suboptimal conditions. J Biol Chem 2023; 299:105269. [PMID: 37739036 PMCID: PMC10590752 DOI: 10.1016/j.jbc.2023.105269] [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: 02/17/2023] [Revised: 09/06/2023] [Accepted: 09/09/2023] [Indexed: 09/24/2023] Open
Abstract
Prenylation is an irreversible post-translational modification that supports membrane interactions of proteins involved in various cellular processes, including migration, proliferation, and survival. Dysregulation of prenylation contributes to multiple disorders, including cancers and vascular and neurodegenerative diseases. Prenyltransferases tether isoprenoid lipids to proteins via a thioether linkage during prenylation. Pharmacological inhibition of the lipid synthesis pathway by statins is 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 inhibition. We examined the prenylation 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 prenylation and membrane interactions of the prenylated proteins. Our findings suggest that specific Ct residues regulate membrane interactions of the Gγ polypeptide, statin sensitivity, and extent of prenylation. Our results also show 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 indicate a plausible mechanism allowing for statins to differentially perturb heterotrimeric G protein signaling in cells depending on their Gγ-subtype composition. Our results may also 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, Missouri, USA; Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio, USA; Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, Missouri, USA
| | - Waruna Thotamune
- Department of Chemistry, Saint Louis University, Saint Louis, Missouri, USA; Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio, USA; Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, Missouri, USA
| | - John L Payton
- Department of Chemistry, Kenyon College, Gambier, Ohio, USA
| | - Ajith Karunarathne
- Department of Chemistry, Saint Louis University, Saint Louis, Missouri, USA; Department of Chemistry and Biochemistry, The University of Toledo, Toledo, Ohio, USA; Institute for Drug and Biotherapeutic Innovation, Saint Louis University, Saint Louis, Missouri, USA.
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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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Wu X, Song W, Cheng C, Liu Z, Li X, Cui Y, Gao Y, Li D. Small molecular inhibitors for KRAS-mutant cancers. Front Immunol 2023; 14:1223433. [PMID: 37662925 PMCID: PMC10470052 DOI: 10.3389/fimmu.2023.1223433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 07/31/2023] [Indexed: 09/05/2023] Open
Abstract
Three rat sarcoma (RAS) gene isoforms, KRAS, NRAS, and HRAS, constitute the most mutated family of small GTPases in cancer. While the development of targeted immunotherapies has led to a substantial improvement in the overall survival of patients with non-KRAS-mutant cancer, patients with RAS-mutant cancers have an overall poorer prognosis owing to the high aggressiveness of RAS-mutant tumors. KRAS mutations are strongly implicated in lung, pancreatic, and colorectal cancers. However, RAS mutations exhibit diverse patterns of isoforms, substitutions, and positions in different types of cancers. Despite being considered "undruggable", recent advances in the use of allele-specific covalent inhibitors against the most common mutant form of RAS in non-small-cell lung cancer have led to the development of effective pharmacological interventions against RAS-mutant cancer. Sotorasib (AMG510) has been approved by the FDA as a second-line treatment for patients with KRAS-G12C mutant NSCLC who have received at least one prior systemic therapy. Other KRAS inhibitors are on the way to block KRAS-mutant cancers. In this review, we summarize the progress and promise of small-molecule inhibitors in clinical trials, including direct inhibitors of KRAS, pan-RAS inhibitors, inhibitors of RAS effector signaling, and immune checkpoint inhibitors or combinations with RAS inhibitors, to improve the prognosis of tumors with RAS mutations.
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Affiliation(s)
- Xuan Wu
- Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
- Academy of Medical Science, Zhengzhou University, Zhengzhou, China
| | - Wenping Song
- Department of Pharmacy, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
- Henan Engineering Research Center for Tumor Precision Medicine and Comprehensive Evaluation, Henan Cancer Hospital, Zhengzhou, China
- Henan Provincial Key Laboratory of Anticancer Drug Research, Henan Cancer Hospital, Zhengzhou, China
| | - Cheng Cheng
- Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
| | - Ziyang Liu
- Academy of Medical Science, Zhengzhou University, Zhengzhou, China
| | - Xiang Li
- Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
| | - Yu Cui
- Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
| | - Yao Gao
- Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
| | - Ding Li
- Department of Pharmacy, The Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, Zhengzhou, China
- Henan Engineering Research Center for Tumor Precision Medicine and Comprehensive Evaluation, Henan Cancer Hospital, Zhengzhou, China
- Henan Provincial Key Laboratory of Anticancer Drug Research, Henan Cancer Hospital, Zhengzhou, China
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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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7
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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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MAGED2 Is Required under Hypoxia for cAMP Signaling by Inhibiting MDM2-Dependent Endocytosis of G-Alpha-S. Cells 2022; 11:cells11162546. [PMID: 36010623 PMCID: PMC9406315 DOI: 10.3390/cells11162546] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 08/14/2022] [Accepted: 08/15/2022] [Indexed: 01/15/2023] Open
Abstract
Mutations in MAGED2 cause transient Bartter syndrome characterized by severe renal salt wasting in fetuses and infants, which leads to massive polyhydramnios causing preterm labor, extreme prematurity and perinatal death. Notably, this condition resolves spontaneously in parallel with developmental increase in renal oxygenation. MAGED2 interacts with G-alpha-S (Gαs). Given the role of Gαs in activating adenylyl cyclase at the plasma membrane and consequently generating cAMP to promote renal salt reabsorption via protein kinase A (PKA), we hypothesized that MAGED2 is required for this signaling pathway under hypoxic conditions such as in fetuses. Consistent with that, under both physical and chemical hypoxia, knockdown of MAGED2 in renal (HEK293) and cancer (HeLa) cell culture models caused internalization of Gαs, which was fully reversible upon reoxygenation. In contrast to Gαs, cell surface expression of the β2-adrenergic receptor, which is coupled to Gαs, was not affected by MAGED2 depletion, demonstrating specific regulation of Gαs by MAGED2. Importantly, the internalization of Gαs due to MAGED2 deficiency significantly reduced cAMP generation and PKA activity. Interestingly, the internalization of Gαs was blocked by preventing its endocytosis with dynasore. Given the role of E3 ubiquitin ligases, which can be regulated by MAGE-proteins, in regulating endocytosis, we assessed the potential role of MDM2-dependent ubiquitination in MAGED2 deficiency-induced internalization of Gαs under hypoxia. Remarkably, MDM2 depletion or its chemical inhibition fully abolished Gαs-endocytosis following MAGED2 knockdown. Moreover, endocytosis of Gαs was also blocked by mutation of ubiquitin acceptor sites in Gαs. Thus, we reveal that MAGED2 is essential for the cAMP/PKA pathway under hypoxia to specifically regulate Gαs endocytosis by blocking MDM2-dependent ubiquitination of Gαs. This may explain, at least in part, the transient nature of Bartter syndrome caused by MAGED2 mutations and opens new avenues for therapy in these patients.
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Kamimura Y, Ueda M. Different Heterotrimeric G Protein Dynamics for Wide-Range Chemotaxis in Eukaryotic Cells. Front Cell Dev Biol 2021; 9:724797. [PMID: 34414196 PMCID: PMC8369479 DOI: 10.3389/fcell.2021.724797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 07/13/2021] [Indexed: 01/14/2023] Open
Abstract
Chemotaxis describes directional motility along ambient chemical gradients and has important roles in human physiology and pathology. Typical chemotactic cells, such as neutrophils and Dictyostelium cells, can detect spatial differences in chemical gradients over a background concentration of a 105 scale. Studies of Dictyostelium cells have elucidated the molecular mechanisms of gradient sensing involving G protein coupled receptor (GPCR) signaling. GPCR transduces spatial information through its cognate heterotrimeric G protein as a guanine nucleotide change factor (GEF). More recently, studies have revealed unconventional regulation of heterotrimeric G protein in the gradient sensing. In this review, we explain how multiple mechanisms of GPCR signaling ensure the broad range sensing of chemical gradients in Dictyostelium cells as a model for eukaryotic chemotaxis.
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Affiliation(s)
- Yoichiro Kamimura
- Laboratory for Cell Signaling Dynamics, RIKEN, Center for Biosystems Dynamics Research (BDR), Suita, Japan.,Laboratory of Single Molecule Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Masahiro Ueda
- Laboratory for Cell Signaling Dynamics, RIKEN, Center for Biosystems Dynamics Research (BDR), Suita, Japan.,Laboratory of Single Molecule Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
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10
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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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11
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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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Vakilian M, Tahamtani Y, Ghaedi K. A review on insulin trafficking and exocytosis. Gene 2019; 706:52-61. [DOI: 10.1016/j.gene.2019.04.063] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/22/2019] [Accepted: 04/23/2019] [Indexed: 12/21/2022]
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Mutual action by Gγ and Gβ for optimal activation of GIRK channels in a channel subunit-specific manner. Sci Rep 2019; 9:508. [PMID: 30679535 PMCID: PMC6346094 DOI: 10.1038/s41598-018-36833-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 11/29/2018] [Indexed: 01/06/2023] Open
Abstract
The tetrameric G protein-gated K+ channels (GIRKs) mediate inhibitory effects of neurotransmitters that activate Gi/o-coupled receptors. GIRKs are activated by binding of the Gβγ dimer, via contacts with Gβ. Gγ underlies membrane targeting of Gβγ, but has not been implicated in channel gating. We observed that, in Xenopus oocytes, expression of Gγ alone activated homotetrameric GIRK1* and heterotetrameric GIRK1/3 channels, without affecting the surface expression of GIRK or Gβ. Gγ and Gβ acted interdependently: the effect of Gγ required the presence of ambient Gβ and was enhanced by low doses of coexpressed Gβ, whereas excess of either Gβ or Gγ imparted suboptimal activation, possibly by sequestering the other subunit “away” from the channel. The unique distal C-terminus of GIRK1, G1-dCT, was important but insufficient for Gγ action. Notably, GIRK2 and GIRK1/2 were not activated by Gγ. Our results suggest that Gγ regulates GIRK1* and GIRK1/3 channel’s gating, aiding Gβ to trigger the channel’s opening. We hypothesize that Gγ helps to relax the inhibitory effect of a gating element (“lock”) encompassed, in part, by the G1-dCT; GIRK2 acts to occlude the effect of Gγ, either by setting in motion the same mechanism as Gγ, or by triggering an opposing gating effect.
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Structural basis of Gip1 for cytosolic sequestration of G protein in wide-range chemotaxis. Nat Commun 2018; 9:4635. [PMID: 30401901 PMCID: PMC6219514 DOI: 10.1038/s41467-018-07035-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 10/10/2018] [Indexed: 12/15/2022] Open
Abstract
G protein interacting protein 1 (Gip1) binds and sequesters heterotrimeric G proteins in the cytosolic pool, thus regulating G protein-coupled receptor (GPCR) signalling for eukaryotic chemotaxis. Here, we report the underlying structural basis of Gip1 function. The crystal structure reveals that the region of Gip1 that binds to the G protein has a cylinder-like fold with a central hydrophobic cavity composed of six α-helices. Mutagenesis and biochemical analyses indicate that the hydrophobic cavity and the hydrogen bond network at the entrance of the cavity are essential for complex formation with the geranylgeranyl modification on the Gγ subunit. Mutations of the cavity impair G protein sequestration and translocation to the membrane from the cytosol upon receptor stimulation, leading to defects in chemotaxis at higher chemoattractant concentrations. These results demonstrate that the Gip1-dependent regulation of G protein shuttling ensures wide-range gradient sensing in eukaryotic chemotaxis. Gip1 sequesters heterotrimeric G proteins in the cytosolic pool which regulates G protein-coupled receptor signalling for eukaryotic chemotaxis. Here the authors provide the crystal structure of Gip1's G protein-binding region and show that mutations in this region lead to G protein sequestration and ultimately chemotaxis defects.
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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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Song JM, Sung YM, Nam JH, Yoon H, Chung A, Moffat E, Jung M, Pak DTS, Kim J, Hoe HS. A Mercaptoacetamide-Based Class II Histone Deacetylase Inhibitor Increases Dendritic Spine Density via RasGRF1/ERK Pathway. J Alzheimers Dis 2016; 51:591-604. [PMID: 26890742 DOI: 10.3233/jad-150717] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The accumulation of amyloid-β (Aβ) leads to the loss of dendritic spines and synapses, which is hypothesized to cause cognitive impairments in Alzheimer's disease (AD) patients. In our previous study, we demonstrated that a novel mercaptoacetamide-based class II histone deacetylase inhibitor (HDACI), known as W2, decreased Aβ levels and improved learning and memory in mice. However, the underlying mechanism of this effect is unknown. OBJECTIVE Because dendritic spine formation is associated with cognitive performance, here we investigated whether HDACI W2 regulates dendritic spine density and its molecular mechanism of action. METHODS To examine the effect of HDACI W2 on dendritic spine density, we conducted morphological analysis of dendritic spines using GFP transfection and Golgi staining. In addition, to determine the molecular mechanism of W2 effects on spines, we measured the levels of mRNAs and proteins involved in the Ras signaling pathway using quantitative real-time PCR, immunocytochemistry, and western analysis. RESULTS We found that HDACI W2 altered dendritic spine density and morphology in vitro and in vivo. Additionally, W2 increased the mRNA or protein levels of Ras GRF1 and phospho-ERK. Moreover, knockdown of RasGRF1 and inhibition of ERK activity prevented the W2-mediated spinogenesis in primary hippocampal neurons. CONCLUSION Our Class II-selective HDACI W2 promotes the formation and growth of dendritic spines in a RasGRF1 and ERK dependent manner in primary hippocampal neurons.
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Affiliation(s)
- Jung Min Song
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
| | - You Me Sung
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
| | - Jin Han Nam
- Department of Neural Development and Disease, Korea Brain Research Institute (KBRI), Dong-gu, Daegu, Korea
| | - Hyejin Yoon
- Department of Neuroscience, Neurobiology of Disease Graduate Program, Mayo Graduate School, Mayo Clinic College of Medicine, Jacksonville, FL, USA
| | - Andrew Chung
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
| | - Emily Moffat
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
| | - Mira Jung
- Department of Radiation Medicine, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, USA
| | - Daniel T S Pak
- Department of Pharmacology, Georgetown University Medical Center, Washington, DC, USA
| | - Jungsu Kim
- Department of Neuroscience, Neurobiology of Disease Graduate Program, Mayo Graduate School, Mayo Clinic College of Medicine, Jacksonville, FL, USA
| | - Hyang-Sook Hoe
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA.,Department of Neural Development and Disease, Korea Brain Research Institute (KBRI), Dong-gu, Daegu, Korea
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Klayman LM, Wedegaertner PB. Inducible Inhibition of Gβγ Reveals Localization-dependent Functions at the Plasma Membrane and Golgi. J Biol Chem 2016; 292:1773-1784. [PMID: 27994056 DOI: 10.1074/jbc.m116.750430] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 12/16/2016] [Indexed: 01/28/2023] Open
Abstract
Heterotrimeric G proteins signal at a variety of endomembrane locations, in addition to their canonical function at the cytoplasmic surface of the plasma membrane (PM), where they are activated by cell surface G protein-coupled receptors. Here we focus on βγ signaling at the Golgi, where βγ activates a signaling cascade, ultimately resulting in vesicle fission from the trans-Golgi network (TGN). To develop a novel molecular tool for inhibiting endogenous βγ in a spatial-temporal manner, we take advantage of a lipid association mutant of the widely used βγ inhibitor GRK2ct (GRK2ct-KERE) and the FRB/FKBP heterodimerization system. We show that GRK2ct-KERE cannot inhibit βγ function when expressed in cells, but recruitment to a specific membrane location recovers the ability of GRK2ct-KERE to inhibit βγ signaling. PM-recruited GRK2ct-KERE inhibits lysophosphatidic acid-induced phosphorylation of Akt, whereas Golgi-recruited GRK2ct-KERE inhibits cargo transport from the TGN to the PM. Moreover, we show that Golgi-recruited GRK2ct-KERE inhibits model basolaterally targeted but not apically targeted cargo delivery, for both PM-destined and secretory cargo, providing the first evidence of selectivity in terms of cargo transport regulated by βγ. Last, we show that Golgi fragmentation induced by ilimaquinone and nocodazole is blocked by βγ inhibition, demonstrating that βγ is a key regulator of multiple pathways that impact Golgi morphology. Thus, we have developed a new molecular tool, recruitable GRK2ct-KERE, to modulate βγ signaling at specific subcellular locations, and we demonstrate novel cargo selectivity for βγ regulation of TGN to PM transport and a novel role for βγ in mediating Golgi fragmentation.
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Affiliation(s)
- Lauren M Klayman
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Philip B Wedegaertner
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
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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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20
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Gβγ subunits-Different spaces, different faces. Pharmacol Res 2016; 111:434-441. [PMID: 27378564 DOI: 10.1016/j.phrs.2016.06.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Revised: 06/27/2016] [Accepted: 06/28/2016] [Indexed: 11/20/2022]
Abstract
Gβγ subunits play key roles in modulation of canonical effectors in G protein-coupled receptor (GPCR)-dependent signalling at the cell surface. However, a number of recent studies of Gβγ function have revealed that they regulate a large number of molecules at distinct subcellular sites. These novel, non-canonical Gβγ roles have reshaped our understanding of how important Gβγ signalling is compared to our original notion of Gβγ subunits as simple negative regulators of Gα subunits. Gβγ dimers have now been identified as regulators of transcription, anterograde and retrograde trafficking and modulators of second messenger molecule generation in intracellular organelles. Here, we review some recent advances in our understanding of these novel non-canonical roles of Gβγ.
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Sarma T, Koutsouris A, Yu JZ, Krbanjevic A, Hope TJ, Rasenick MM. Activation of microtubule dynamics increases neuronal growth via the nerve growth factor (NGF)- and Gαs-mediated signaling pathways. J Biol Chem 2015; 290:10045-56. [PMID: 25691569 DOI: 10.1074/jbc.m114.630632] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Indexed: 01/19/2023] Open
Abstract
Signals that activate the G protein Gαs and promote neuronal differentiation evoke Gαs internalization in rat pheochromocytoma (PC12) cells. These agents also significantly increase Gαs association with microtubules, resulting in an increase in microtubule dynamics because of the activation of tubulin GTPase by Gαs. To determine the function of Gαs/microtubule association in neuronal development, we used real-time trafficking of a GFP-Gαs fusion protein. GFP-Gαs concentrates at the distal end of the neurites in differentiated living PC12 cells as well as in cultured hippocampal neurons. Gαs translocates to specialized membrane compartments at tips of growing neurites. A dominant-negative Gα chimera that interferes with Gαs binding to tubulin and activation of tubulin GTPase attenuates neurite elongation and neurite number both in PC12 cells and primary hippocampal neurons. This effect is greatest on differentiation induced by activated Gαs. Together, these data suggest that activated Gαs translocates from the plasma membrane and, through interaction with tubulin/microtubules in the cytosol, is important for neurite formation, development, and outgrowth. Characterization of neuronal G protein dynamics and their contribution to microtubule dynamics is important for understanding the molecular mechanisms by which G protein-coupled receptor signaling orchestrates neuronal growth and differentiation.
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Affiliation(s)
- Tulika Sarma
- From the Department of Physiology and Biophysics and
| | | | - Jiang Zhu Yu
- From the Department of Physiology and Biophysics and
| | - Aleksandar Krbanjevic
- From the Department of Physiology and Biophysics and Psychiatry, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612
| | - Thomas J Hope
- the Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, and
| | - Mark M Rasenick
- From the Department of Physiology and Biophysics and Psychiatry, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, the Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612
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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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Minchew CL, Didenko VV. Nanoblinker: Brownian motion powered bio-nanomachine for FRET detection of phagocytic phase of apoptosis. PLoS One 2014; 9:e108734. [PMID: 25268504 PMCID: PMC4182547 DOI: 10.1371/journal.pone.0108734] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 09/03/2014] [Indexed: 01/09/2023] Open
Abstract
We describe a new type of bio-nanomachine which runs on thermal noise. The machine is solely powered by the random motion of water molecules in its environment and does not ever require re-fuelling. The construct, which is made of DNA and vaccinia virus topoisomerase protein, can detect DNA damage by employing fluorescence. It uses Brownian motion as a cyclic motor to continually separate and bring together two types of fluorescent hairpins participating in FRET. This bio-molecular oscillator is a fast and specific sensor of 5'OH double-strand DNA breaks present in phagocytic phase of apoptosis. The detection takes 30 s in solution and 3 min in cell suspensions. The phagocytic phase is critical for the effective execution of apoptosis as it ensures complete degradation of the dying cells' DNA, preventing release of pathological, viral and tumor DNA and self-immunization. The construct can be used as a smart FRET probe in studies of cell death and phagocytosis.
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Affiliation(s)
- Candace L. Minchew
- Baylor College of Medicine, Houston, Texas, United States of America
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, United States of America
| | - Vladimir V. Didenko
- Baylor College of Medicine, Houston, Texas, United States of America
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, United States of America
- * E-mail:
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Lütjens R, Perry B, Schelshorn D, Rocher JP. New technologies enabling the industrialization of allosteric modulator discovery. DRUG DISCOVERY TODAY. TECHNOLOGIES 2013; 10:e253-60. [PMID: 24050276 DOI: 10.1016/j.ddtec.2013.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Allosteric modulators (AMs) are a promising avenue towards safe and selective drugs. AMs can interact selectively with unique domains distinct from the endogenous ligand binding site of receptors, up- or downregulating the response to receptor activation. Emphasis is placed in this article on the latest development in high-sensitivity technologies designed to identify AMs of G-protein coupled receptors. In addition to new pharmacological approaches, encouraging results in the crystal resolution of these targets enable use of more rational approaches to identification and optimization of AMs.
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A tetra(ethylene glycol) derivative of benzothiazole aniline enhances Ras-mediated spinogenesis. J Neurosci 2013; 33:9306-18. [PMID: 23719799 DOI: 10.1523/jneurosci.1615-12.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The tetra(ethylene glycol) derivative of benzothiazole aniline, BTA-EG4, is a novel amyloid-binding small molecule that can penetrate the blood-brain barrier and protect cells from Aβ-induced toxicity. However, the effects of Aβ-targeting molecules on other cellular processes, including those that modulate synaptic plasticity, remain unknown. We report here that BTA-EG4 decreases Aβ levels, alters cell surface expression of amyloid precursor protein (APP), and improves memory in wild-type mice. Interestingly, the BTA-EG4-mediated behavioral improvement is not correlated with LTP, but with increased spinogenesis. The higher dendritic spine density reflects an increase in the number of functional synapses as determined by increased miniature EPSC (mEPSC) frequency without changes in presynaptic parameters or postsynaptic mEPSC amplitude. Additionally, BTA-EG4 requires APP to regulate dendritic spine density through a Ras signaling-dependent mechanism. Thus, BTA-EG4 may provide broad therapeutic benefits for improving neuronal and cognitive function, and may have implications in neurodegenerative disease therapy.
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Lau WW, Chan AS, Poon LS, Zhu J, Wong YH. Gβγ-mediated activation of protein kinase D exhibits subunit specificity and requires Gβγ-responsive phospholipase Cβ isoforms. Cell Commun Signal 2013; 11:22. [PMID: 23561540 PMCID: PMC3637504 DOI: 10.1186/1478-811x-11-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 03/22/2013] [Indexed: 11/29/2022] Open
Abstract
Background Protein kinase D (PKD) constitutes a novel family of serine/threonine protein kinases implicated in fundamental biological activities including cell proliferation, survival, migration, and immune responses. Activation of PKD in these cellular activities has been linked to many extracellular signals acting through antigen receptor engagement, receptor tyrosine kinases, as well as G protein-coupled receptors. In the latter case, it is generally believed that the Gα subunits of the Gq family are highly effective in mediating PKD activation, whereas little is known with regard to the ability of Gβγ dimers and other Gα subunits to stimulate PKD. It has been suggested that the interaction between Gβγ and the PH domain of PKD, or the Gβγ-induced PLCβ/PKC activity is critical for the induction of PKD activation. However, the relative contribution of these two apparently independent events to Gβγ-mediated PKD activation has yet to be addressed. Results In this report, we demonstrate that among various members in the four G protein families, only the Gα subunits of the Gq family effectively activate all the three PKD isoforms (PKD1/2/3), while Gα subunits of other G protein families (Gs, Gi, and G12) are ineffective. Though the Gα subunits of Gi family are unable to stimulate PKD, receptors linked to Gi proteins are capable of triggering PKD activation in cell lines endogenously expressing (HeLa cells and Jurkat T-cells) or exogenously transfected with (HEK293 cells) Gβγ-sensitive PLCβ2/3 isoforms. This indicates that the Gi-mediated PKD activation is dependent on the released Gβγ dimers upon stimulation. Further investigation on individual Gβγ combinations (i.e. Gβ1 with Gγ1–13) revealed that, even if they can stimulate the PLCβ activity in a comparable manner, only those Gβ1γ dimers with γ2, γ3, γ4, γ5, γ7, and γ10 can serve as effective activators of PKD. We also demonstrated that Gi-mediated PKD activation is essential for the SDF-1α-induced chemotaxis on Jurkat T-cells. Conclusions Our current report illustrates that Gβγ dimers from the Gi proteins may activate PKD in a PLCβ2/3-dependent manner, and the specific identities of Gγ components within Gβγ dimers may determine this stimulatory action.
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Affiliation(s)
- Winnie Wi Lau
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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Optically triggering spatiotemporally confined GPCR activity in a cell and programming neurite initiation and extension. Proc Natl Acad Sci U S A 2013; 110:E1565-74. [PMID: 23479634 DOI: 10.1073/pnas.1220697110] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G-protein-coupled receptor (GPCR) activity gradients evoke important cell behavior but there is a dearth of methods to induce such asymmetric signaling in a cell. Here we achieved reversible, rapidly switchable patterns of spatiotemporally restricted GPCR activity in a single cell. We recruited properties of nonrhodopsin opsins--rapid deactivation, distinct spectral tuning, and resistance to bleaching--to activate native Gi, Gq, or Gs signaling in selected regions of a cell. Optical inputs were designed to spatiotemporally control levels of second messengers, IP3, phosphatidylinositol (3,4,5)-triphosphate, and cAMP in a cell. Spectrally selective imaging was accomplished to simultaneously monitor optically evoked molecular and cellular response dynamics. We show that localized optical activation of an opsin-based trigger can induce neurite initiation, phosphatidylinositol (3,4,5)-triphosphate increase, and actin remodeling. Serial optical inputs to neurite tips can refashion early neuron differentiation. Methods here can be widely applied to program GPCR-mediated cell behaviors.
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Benes J, Mravec B, Kvetnansky R, Myslivecek J. The restructuring of muscarinic receptor subtype gene transcripts in c-fos knock-out mice. Brain Res Bull 2013; 94:30-9. [PMID: 23395867 DOI: 10.1016/j.brainresbull.2013.01.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 01/17/2013] [Accepted: 01/29/2013] [Indexed: 10/27/2022]
Abstract
Although c-Fos plays a key role in intracellular signalling, the disruption of the c-fos gene has only minor consequences on the central nervous system (CNS) function. As muscarinic receptors (MR) play important roles in many CNS functions (attention, arousal, and cognition), the c-fos knock-out might be compensated through MR changes. The aim of this study was to evaluate changes in the M1-M5 MR mRNA in selected CNS areas: frontal, parietal, temporal and occipital cortex, striatum, hippocampus, hypothalamus and cerebellum (FC, PC, TC, OC, stria, hip, hypo, and crbl, respectively). Knocking out the c-fos gene changed the expression of MR in FC (reduced M1R, M4R and M5R expression), TC (increased M4R expression), OC (decreased M2R and M3R expression) and hippocampus (reduced M3R expression). Moreover, gender differences were observed in WT mice: increased expression of all M1-M5R in the FC in males and M1-M4R in the striatum in females. A detailed analysis of MR transcripts showed pre-existing correlations in the amount of MR-mRNA between specific regions. WT mice showed three major types of cortico-cortical correlations: fronto-occipital, temporo-parietal and parieto-occipital. The cortico-subcortical correlations involved associations between the FC, PC, TC and striatum. In KO mice, a substantial rearrangement of the correlation pattern was observed: only a temporo-parietal correlation and correlations between the FC and striatum remained, and a new correlation between the hypothalamus and cerebellum appeared. Thus, in addition to the previously described dopamine receptor restructuring, the restructuring of MR mRNA correlations reveals an additional mechanism for adaptation to the c-fos gene knockout.
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Affiliation(s)
- Jan Benes
- Institute of Physiology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic.
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Bhatnagar A, Unal H, Jagannathan R, Kaveti S, Duan ZH, Yong S, Vasanji A, Kinter M, Desnoyer R, Karnik SS. Interaction of G-protein βγ complex with chromatin modulates GPCR-dependent gene regulation. PLoS One 2013; 8:e52689. [PMID: 23326349 PMCID: PMC3541368 DOI: 10.1371/journal.pone.0052689] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 11/19/2012] [Indexed: 11/21/2022] Open
Abstract
Heterotrimeric G-protein signal transduction initiated by G-protein-coupled receptors (GPCRs) in the plasma membrane is thought to propagate through protein-protein interactions of subunits, Gα and Gβγ in the cytosol. In this study, we show novel nuclear functions of Gβγ through demonstrating interaction of Gβ2 with integral components of chromatin and effects of Gβ2 depletion on global gene expression. Agonist activation of several GPCRs including the angiotensin II type 1 receptor specifically augmented Gβ2 levels in the nucleus and Gβ2 interacted with specific nucleosome core histones and transcriptional modulators. Depletion of Gβ2 repressed the basal and angiotensin II-dependent transcriptional activities of myocyte enhancer factor 2. Gβ2 interacted with a sequence motif that was present in several transcription factors, whose genome-wide binding accounted for the Gβ2-dependent regulation of approximately 2% genes. These findings suggest a wide-ranging mechanism by which direct interaction of Gβγ with specific chromatin bound transcription factors regulates functional gene networks in response to GPCR activation in cells.
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Affiliation(s)
- Anushree Bhatnagar
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Hamiyet Unal
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Rajaganapathi Jagannathan
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Suma Kaveti
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Zhong-Hui Duan
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Computer Science, University of Akron, Akron, Ohio, United States of America
| | - Sandro Yong
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Amit Vasanji
- Biomedical Imaging and Analysis Core, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Michael Kinter
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Russell Desnoyer
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Sadashiva S. Karnik
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail:
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Alam-Nazki A, Krishnan J. An investigation of spatial signal transduction in cellular networks. BMC SYSTEMS BIOLOGY 2012; 6:83. [PMID: 22765014 PMCID: PMC3537682 DOI: 10.1186/1752-0509-6-83] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 06/12/2012] [Indexed: 12/20/2022]
Abstract
Background Spatial signal transduction plays a vital role in many intracellular processes such as eukaryotic chemotaxis, polarity generation and cell division. Furthermore it is being increasingly realized that the spatial dimension to signalling may play an important role in other apparently purely temporal signal transduction processes. It is increasingly being recognized that a conceptual basis for studying spatial signal transduction in signalling networks is necessary. Results In this work we examine spatial signal transduction in a series of standard motifs/networks. These networks include coherent and incoherent feedforward, positive and negative feedback, cyclic motifs, monostable switches, bistable switches and negative feedback oscillators. In all these cases, the driving signal has spatial variation. For each network we consider two cases, one where all elements are essentially non-diffusible, and the other where one of the network elements may be highly diffusible. A careful analysis of steady state signal transduction provides many insights into the behaviour of all these modules. While in the non-diffusible case for the most part, spatial signalling reflects the temporal signalling behaviour, in the diffusible cases, we see significant differences between spatial and temporal signalling characteristics. Our results demonstrate that the presence of diffusible elements in the networks provides important constraints and capabilities for signalling. Conclusions Our results provide a systematic basis for understanding spatial signalling in networks and the role of diffusible elements therein. This provides many insights into the signal transduction capabilities and constraints in such networks and suggests ways in which cellular signalling and information processing is organized to conform to or bypass those constraints. It also provides a framework for starting to understand the organization and regulation of spatial signal transduction in individual processes.
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Affiliation(s)
- Aiman Alam-Nazki
- Centre for Process Systems Engineering, Department of Chemical Engineering, South Kensington Campus, London, SW7 2AZ, UK
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Ajith Karunarathne WK, O'Neill PR, Martinez-Espinosa PL, Kalyanaraman V, Gautam N. All G protein βγ complexes are capable of translocation on receptor activation. Biochem Biophys Res Commun 2012; 421:605-11. [PMID: 22538369 DOI: 10.1016/j.bbrc.2012.04.054] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/11/2012] [Indexed: 11/18/2022]
Abstract
Heterotrimeric G proteins transduce signals sensed by transmembrane G protein coupled receptors (GPCRs). A subfamily of G protein βγ subunit types has been shown to selectively translocate from the plasma membrane to internal membranes on receptor activation. Using 4D imaging we show here that Gβγ translocation is not restricted to some subunit types but rather all 12 members of the family of mammalian γ subunits are capable of supporting βγ translocation. Translocation kinetics varies widely depending on the specific γ subunit type, with t(1/2) ranging from 10s to many minutes. Using fluorescence complementation, we show that the β and γ subunits translocate as βγ dimers with kinetics determined by the γ subunit type. The expression patterns of endogenous γ subunit types in HeLa cells, hippocampal neurons and cardiomyocytes are distinctly different. Consistent with these differences, the βγ translocation rates vary widely. βγ translocation rates exhibit the same γ subunit dependent trends regardless of the specific receptor type or cell type showing that the translocation rates are intrinsic to the γ subunit types. βγ complexes with widely different rates of translocation had differential effects on muscarinic stimulation of GIRK channel activity. These results show that G protein βγ translocation is a general response to activation of GPCRs and may play a role in regulating signaling activity.
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Affiliation(s)
- W K Ajith Karunarathne
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Hewavitharana T, Wedegaertner PB. Non-canonical signaling and localizations of heterotrimeric G proteins. Cell Signal 2012; 24:25-34. [PMID: 21907280 PMCID: PMC3205251 DOI: 10.1016/j.cellsig.2011.08.014] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 08/20/2011] [Indexed: 10/17/2022]
Abstract
Heterotrimeric G proteins typically transduce signals from G protein-coupled receptors (GPCRs) to effector proteins. In the conventional G protein signaling paradigm, the G protein is located at the cytoplasmic surface of the plasma membrane, where, after activation by an agonist-bound GPCR, the GTP-bound Gα and free Gβγ bind to and regulate a number of well-studied effectors, including adenylyl cyclase, phospholipase Cβ, RhoGEFs and ion channels. However, research over the past decade or more has established that G proteins serve non-canonical roles in the cell, whereby they regulate novel effectors, undergo activation independently of a GPCR, and/or function at subcellular locations other than the plasma membrane. This review will highlight some of these non-canonical aspects of G protein signaling, focusing on direct interactions of G protein subunits with cytoskeletal and cell adhesion proteins, the role of G proteins in cell division, and G protein signaling at diverse organelles.
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Affiliation(s)
- Thamara Hewavitharana
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States
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33
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Abstract
The classical view of heterotrimeric G protein signaling places G -proteins at the cytoplasmic surface of the cell's plasma membrane where they are activated by an appropriate G protein-coupled receptor. Once activated, the GTP-bound Gα and the free Gβγ are able to regulate plasma membrane-localized effectors, such as adenylyl cyclase, phospholipase C-β, RhoGEFs and ion channels. Hydrolysis of GTP by the Gα subunit returns the G protein to the inactive Gαβγ heterotrimer. Although all of these events in the G protein cycle can be restricted to the cytoplasmic surface of the plasma membrane, G protein localization is dynamic. Thus, it has become increasingly clear that G proteins are able to move to diverse subcellular locations where they perform non-canonical signaling functions. This chapter will highlight our current understanding of trafficking pathways that target newly synthesized G proteins to the plasma membrane, activation-induced and reversible translocation of G proteins from the plasma membrane to intracellular locations, and constitutive trafficking of G proteins.
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Protein palmitoylation and subcellular trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2981-94. [DOI: 10.1016/j.bbamem.2011.07.009] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 07/06/2011] [Accepted: 07/12/2011] [Indexed: 02/07/2023]
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Affiliation(s)
| | - Adam D. Linstedt
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15232;
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Tummala H, Fleming S, Hocking PM, Wehner D, Naseem Z, Ali M, Inglehearn CF, Zhelev N, Lester DH. The D153del mutation in GNB3 gene causes tissue specific signalling patterns and an abnormal renal morphology in Rge chickens. PLoS One 2011; 6:e21156. [PMID: 21887213 PMCID: PMC3159573 DOI: 10.1371/journal.pone.0021156] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 05/21/2011] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The GNB3 gene is expressed in cone but not rod photoreceptors of vertebrates, where it acts as the β transducin subunit in the colour visual transduction process. A naturally occurring mutation 'D153del' in the GNB3 gene causes the recessively inherited blinding phenotype retinopathy globe enlarged (rge) disease in chickens. GNB3 is however also expressed in most other vertebrate tissues suggesting that the D153del mutation may exert pathological effects that outlie from eye. PRINCIPAL FINDINGS Recombinant studies in COS-7 cells that were transfected with normal and mutant recombinant GNB3 constructs and subjected to cycloheximide chase showed that the mutant GNB3d protein had a much shorter half life compared to normal GNB3. GNB3 codes for the Gβ3 protein subunit that, together with different Gγ and Gα subunits, activates and regulates phosphorylation cascades in different tissues. As expected, the relative levels of cGMP and cAMP secondary messengers and their activated kinases such as MAPK, AKT and GRK2 were also found to be altered significantly in a tissue specific manner in rge chickens. Histochemical analysis on kidney tissue sections, from rge homozygous affected chickens, showed the chickens had enlargement of the glomerular capsule, causing glomerulomegaly and tubulointerstitial inflammation whereas other tissues (brain, heart, liver, pancreas) were unaffected. SIGNIFICANCE These findings confirm that the D153del mutation in GNB3 gene targets GNB3 protein to early degradation. Lack of GNB3 signalling causes reduced phosphorylation activity of ERK2 and AKT leading to severe pathological phenotypes such as blindness and renal abnormalities in rge chickens.
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Affiliation(s)
- Hemanth Tummala
- School of Contemporary Sciences, University of Abertay Dundee, Dundee, Scotland, United Kingdom
| | - Stewart Fleming
- Division of Medical Sciences, Centre for Oncology and Molecular Medicine, College of Medicine Dentistry and Nursing, Ninewells Hospital and Medical School, Dundee, Scotland, United Kingdom
| | - Paul M. Hocking
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, Scotland, United Kingdom
| | - Daniel Wehner
- School of Contemporary Sciences, University of Abertay Dundee, Dundee, Scotland, United Kingdom
| | - Zahid Naseem
- School of Contemporary Sciences, University of Abertay Dundee, Dundee, Scotland, United Kingdom
| | - Manir Ali
- Section of Ophthalmology and Neuroscience, Leeds Institute of Molecular Medicine, St James's University Hospital, Leeds, United Kingdom
| | - Christopher F. Inglehearn
- Section of Ophthalmology and Neuroscience, Leeds Institute of Molecular Medicine, St James's University Hospital, Leeds, United Kingdom
| | - Nikolai Zhelev
- School of Contemporary Sciences, University of Abertay Dundee, Dundee, Scotland, United Kingdom
| | - Douglas H. Lester
- School of Contemporary Sciences, University of Abertay Dundee, Dundee, Scotland, United Kingdom
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Chan P, Gabay M, Wright FA, Tall GG. Ric-8B is a GTP-dependent G protein alphas guanine nucleotide exchange factor. J Biol Chem 2011; 286:19932-42. [PMID: 21467038 DOI: 10.1074/jbc.m110.163675] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ric-8 (resistance to inhibitors of cholinesterase 8) genes have positive roles in variegated G protein signaling pathways, including Gα(q) and Gα(s) regulation of neurotransmission, Gα(i)-dependent mitotic spindle positioning during (asymmetric) cell division, and Gα(olf)-dependent odorant receptor signaling. Mammalian Ric-8 activities are partitioned between two genes, ric-8A and ric-8B. Ric-8A is a guanine nucleotide exchange factor (GEF) for Gα(i)/α(q)/α(12/13) subunits. Ric-8B potentiated G(s) signaling presumably as a Gα(s)-class GEF activator, but no demonstration has shown Ric-8B GEF activity. Here, two Ric-8B isoforms were purified and found to be Gα subunit GDP release factor/GEFs. In HeLa cells, full-length Ric-8B (Ric-8BFL) bound endogenously expressed Gα(s) and lesser amounts of Gα(q) and Gα(13). Ric-8BFL stimulated guanosine 5'-3-O-(thio)triphosphate (GTPγS) binding to these subunits and Gα(olf), whereas the Ric-8BΔ9 isoform stimulated Gα(s short) GTPγS binding only. Michaelis-Menten experiments showed that Ric-8BFL elevated the V(max) of Gα(s) steady state GTP hydrolysis and the apparent K(m) values of GTP binding to Gα(s) from ∼385 nm to an estimated value of ∼42 μM. Directionality of the Ric-8BFL-catalyzed Gα(s) exchange reaction was GTP-dependent. At sub-K(m) GTP, Ric-BFL was inhibitory to exchange despite being a rapid GDP release accelerator. Ric-8BFL binds nucleotide-free Gα(s) tightly, and near-K(m) GTP levels were required to dissociate the Ric-8B·Gα nucleotide-free intermediate to release free Ric-8B and Gα-GTP. Ric-8BFL-catalyzed nucleotide exchange probably proceeds in the forward direction to produce Gα-GTP in cells.
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Affiliation(s)
- PuiYee Chan
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA
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Kang M, Day CA, DiBenedetto E, Kenworthy AK. A quantitative approach to analyze binding diffusion kinetics by confocal FRAP. Biophys J 2011; 99:2737-47. [PMID: 21044570 DOI: 10.1016/j.bpj.2010.09.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Revised: 09/09/2010] [Accepted: 09/13/2010] [Indexed: 11/15/2022] Open
Abstract
Most of the important types of interactions that occur in cells can be characterized as binding-diffusion type processes, and can be quantified by kinetic rate constants such as diffusion coefficients (D) and binding rate constants (k(on) and k(off)). Confocal FRAP is a potentially important tool for the quantitative analysis of intracellular binding-diffusion kinetics, but how to dependably extract accurate kinetic constants from such analyses is still an open question. To this end, in this study, we developed what we believe is a new analytical model for confocal FRAP-based measurements of intracellular binding-diffusion processes, based on a closed-form equation of the FRAP formula for a spot photobleach geometry. This approach incorporates a binding diffusion model that allows for diffusion of both the unbound and bound species, and also compensates for binding diffusion that occurs during photobleaching, a critical consideration in confocal FRAP analysis. In addition, to address the problem of parametric multiplicity, we propose a scheme to reduce the number of fitting parameters in the effective diffusion subregime when D's for the bound and unbound species are known. We validate this method by measuring kinetic rate constants for the CAAX-mediated binding of Ras to membranes of the endoplasmic reticulum, obtaining binding constants of k(on) ∼ 255/s and k(off) ∼ 31/s.
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Affiliation(s)
- Minchul Kang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Vilardaga JP. Theme and variations on kinetics of GPCR activation/deactivation. J Recept Signal Transduct Res 2011; 30:304-12. [PMID: 20836728 DOI: 10.3109/10799893.2010.509728] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
G protein-coupled receptors (GPCRs) initiate intracellular signaling pathways in response to physiologically and medically important extracellular ligands such as peptide and large glycoprotein hormones, neurotransmitters, sensory stimuli (odorant and taste molecules, light), calcium, l-amino acids, and are the target of many clinical drugs. The conversion of these extracellular stimuli into intracellular signals involves sequential and reversible reactions that initially take place at the plasma membrane. These reactions are mediated not only by dynamic interactions between ligands, receptors and heterotrimeric G proteins, but also by conformational changes associated with the activation/deactivation process of each protein. This review discusses the kinetic characteristics and rate-limiting reactions engaged in signal propagation that are involved in systems as diverse as neurotransmitter and hormonal signaling, and that have been recorded in live cells by Förster resonance energy transfer (FRET) approaches.
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Affiliation(s)
- Jean-Pierre Vilardaga
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261, USA.
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Heterogeneous Prenyl Processing of the Heterotrimeric G protein Gamma Subunits. PROTEIN PRENYLATION PART A 2011. [DOI: 10.1016/b978-0-12-381339-8.00006-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Dias JA, Mahale SD, Nechamen CA, Davydenko O, Thomas RM, Ulloa-Aguirre A. Emerging roles for the FSH receptor adapter protein APPL1 and overlap of a putative 14-3-3τ interaction domain with a canonical G-protein interaction site. Mol Cell Endocrinol 2010; 329:17-25. [PMID: 20600589 PMCID: PMC2946492 DOI: 10.1016/j.mce.2010.05.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Revised: 05/20/2010] [Accepted: 05/20/2010] [Indexed: 12/13/2022]
Abstract
The interaction of cytoplasmic proteins with intracellular domains of membrane receptors can occur at several opportunities, including: during biosynthesis, while in membrane residency and during internalization and recycling following ligand binding. Since the initial discovery that it interacts with the FSH receptor (FSHR) together with additional members of a potential signaling complex, APPL1 has been shown to interact with a variety of membrane receptors. Recent subcellular localizations of APPL1 place it in dynamic and varied venues in the cell, including at the cell membrane, the nucleus and the early endosomes. Another adapter protein family the 14-3-3 proteins, are largely recognized as binding to phosphorylation sites but recent work demonstrated that in the case of FSHR, the 14-3-3 site overlaps with the canonical G-protein binding site. G-proteins appear to sample the environment and exchange between the membrane and intracellular locales and this binding could be mediated by or modulated by receptor interactions at the 14-3-3 binding site. Observations that multiple proteins can interact with cytoplasmic domains of GPCRs leads to the inescapable conclusion that either the interactions occur via orderly replacement or exchange, or that receptors are simultaneously occupied by a variety of adapters and effectors or even that oligomers of dimeric GPCRs provide for platforms that can simultaneously interact with effectors and adaptors.
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Affiliation(s)
- James A Dias
- Wadsworth Center, New York State Dept of Health, Albany, NY, United States.
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Regulation of Golgi structure and secretion by receptor-induced G protein βγ complex translocation. Proc Natl Acad Sci U S A 2010; 107:11417-22. [PMID: 20534534 DOI: 10.1073/pnas.1003042107] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We show that receptor induced G protein betagamma subunit translocation from the plasma membrane to the Golgi allows a receptor to initiate fragmentation and regulate secretion. A lung epithelial cell line, A549, was shown to contain an endogenous translocating G protein gamma subunit and exhibit receptor-induced Golgi fragmentation. Receptor-induced Golgi fragmentation was inhibited by a shRNA specific to the endogenous translocating gamma subunit. A kinase defective protein kinase D and a phospholipase C beta inhibitor blocked receptor-induced Golgi fragmentation, suggesting a role for this process in secretion. Consistent with betagamma translocation dependence, fragmentation induced by receptor activation was inhibited by a dominant negative nontranslocating gamma3. Insulin secretion was shown to be induced by muscarinic receptor activation in a pancreatic beta cell line, NIT-1. Induction of insulin secretion was also inhibited by the dominant negative gamma3 subunit consistent with the Golgi fragmentation induced by betagamma complex translocation playing a role in secretion.
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Chisari M, Saini DK, Cho JH, Kalyanaraman V, Gautam N. G protein subunit dissociation and translocation regulate cellular response to receptor stimulation. PLoS One 2009; 4:e7797. [PMID: 19936219 PMCID: PMC2777387 DOI: 10.1371/journal.pone.0007797] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 10/16/2009] [Indexed: 01/23/2023] Open
Abstract
We examined the role of G proteins in modulating the response of living cells to receptor activation. The response of an effector, phospholipase C-β to M3 muscarinic receptor activation was measured using sensors that detect the generation of inositol triphosphate or diacylglycerol. The recently discovered translocation of Gβγ from plasma membrane to endomembranes on receptor activation attenuated this response. A FRET based G protein sensor suggested that in contrast to translocating Gβγ, non-translocating Gβγ subunits do not dissociate from the αq subunit on receptor activation leading to prolonged retention of the heterotrimer state and an accentuated response. M3 receptors with tethered αq induced differential responses to receptor activation in cells with or without an endogenous translocation capable γ subunit. G protein heterotrimer dissociation and βγ translocation are thus unanticipated modulators of the intensity of a cell's response to an extracellular signal.
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Affiliation(s)
- Mariangela Chisari
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Deepak Kumar Saini
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Joon-Ho Cho
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Vani Kalyanaraman
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - N. Gautam
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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