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Panda A, Brown C, Gupta K. Studying Membrane Protein-Lipid Specificity through Direct Native Mass Spectrometric Analysis from Tunable Proteoliposomes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1917-1927. [PMID: 37432128 PMCID: PMC10932607 DOI: 10.1021/jasms.3c00110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Native mass spectrometry (nMS) has emerged as a key analytical tool to study the organizational states of proteins and their complexes with both endogenous and exogenous ligands. Specifically, for membrane proteins, it provides a key analytical dimension to determine the identity of bound lipids and to decipher their effects on the observed structural assembly. We recently developed an approach to study membrane proteins directly from intact and tunable lipid membranes where both the biophysical properties of the membrane and its lipid compositions can be customized. Extending this, we use our liposome-nMS platform to decipher the lipid specificity of membrane proteins through their multiorganelle trafficking pathways. To demonstrate this, we used VAMP2 and reconstituted it in the endoplasmic reticulum (ER), Golgi, synaptic vesicle (SV), and plasma membrane (PM) mimicking liposomes. By directly studying VAMP2 from these customized liposomes, we show how the same transmembrane protein can bind to different sets of lipids in different organellar-mimicking membranes. Considering that the cellular trafficking pathway of most eukaryotic integral membrane proteins involves residence in multiple organellar membranes, this study highlights how the lipid-specificity of the same integral membrane protein may change depending on the membrane context. Further, leveraging the capability of the platform to study membrane proteins from liposomes with curated biophysical properties, we show how we can disentangle chemical versus biophysical properties, of individual lipids in regulating membrane protein assembly.
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Affiliation(s)
- Aniruddha Panda
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Caroline Brown
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Kallol Gupta
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
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Yamahashi Y, Tsuboi D, Funahashi Y, Kaibuchi K. Neuroproteomic mapping of kinases and their substrates downstream of acetylcholine: finding and implications. Expert Rev Proteomics 2023; 20:291-298. [PMID: 37787112 DOI: 10.1080/14789450.2023.2265067] [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: 03/08/2023] [Accepted: 08/09/2023] [Indexed: 10/04/2023]
Abstract
INTRODUCTION Since the emergence of the cholinergic hypothesis of Alzheimer's disease (AD), acetylcholine has been viewed as a mediator of learning and memory. Donepezil improves AD-associated learning deficits and memory loss by recovering brain acetylcholine levels. However, it is associated with side effects due to global activation of acetylcholine receptors. Muscarinic acetylcholine receptor M1 (M1R), a key mediator of learning and memory, has been an alternative target. The importance of targeting a specific pathway downstream of M1R has recently been recognized. Elucidating signaling pathways beyond M1R that lead to learning and memory holds important clues for AD therapeutic strategies. AREAS COVERED This review first summarizes the role of acetylcholine in aversive learning, one of the outputs used for preliminary AD drug screening. It then describes the phosphoproteomic approach focused on identifying acetylcholine intracellular signaling pathways leading to aversive learning. Finally, the intracellular mechanism of donepezil and its effect on learning and memory is discussed. EXPERT OPINION The elucidation of signaling pathways beyond M1R by phosphoproteomic approach offers a platform for understanding the intracellular mechanism of AD drugs and for developing AD therapeutic strategies. Clarifying the molecular mechanism that links the identified acetylcholine signaling to AD pathophysiology will advance the development of AD therapeutic strategies.
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Affiliation(s)
- Yukie Yamahashi
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, Toyoake, Aichi, Japan
| | - Daisuke Tsuboi
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, Toyoake, Aichi, Japan
| | - Yasuhiro Funahashi
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, Toyoake, Aichi, Japan
| | - Kozo Kaibuchi
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, Toyoake, Aichi, Japan
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Phosphoproteomic of the acetylcholine pathway enables discovery of the PKC-β-PIX-Rac1-PAK cascade as a stimulatory signal for aversive learning. Mol Psychiatry 2022; 27:3479-3492. [PMID: 35665767 PMCID: PMC9708603 DOI: 10.1038/s41380-022-01643-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 05/13/2022] [Accepted: 05/23/2022] [Indexed: 11/08/2022]
Abstract
Acetylcholine is a neuromodulator critical for learning and memory. The cholinesterase inhibitor donepezil increases brain acetylcholine levels and improves Alzheimer's disease (AD)-associated learning disabilities. Acetylcholine activates striatal/nucleus accumbens dopamine receptor D2-expressing medium spiny neurons (D2R-MSNs), which regulate aversive learning through muscarinic receptor M1 (M1R). However, how acetylcholine stimulates learning beyond M1Rs remains unresolved. Here, we found that acetylcholine stimulated protein kinase C (PKC) in mouse striatal/nucleus accumbens. Our original kinase-oriented phosphoproteomic analysis revealed 116 PKC substrate candidates, including Rac1 activator β-PIX. Acetylcholine induced β-PIX phosphorylation and activation, thereby stimulating Rac1 effector p21-activated kinase (PAK). Aversive stimulus activated the M1R-PKC-PAK pathway in mouse D2R-MSNs. D2R-MSN-specific expression of PAK mutants by the Cre-Flex system regulated dendritic spine structural plasticity and aversive learning. Donepezil induced PAK activation in both accumbal D2R-MSNs and in the CA1 region of the hippocampus and enhanced D2R-MSN-mediated aversive learning. These findings demonstrate that acetylcholine stimulates M1R-PKC-β-PIX-Rac1-PAK signaling in D2R-MSNs for aversive learning and imply the cascade's therapeutic potential for AD as aversive learning is used to preliminarily screen AD drugs.
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Jones AJY, Gabriel F, Tandale A, Nietlispach D. Structure and Dynamics of GPCRs in Lipid Membranes: Physical Principles and Experimental Approaches. Molecules 2020; 25:E4729. [PMID: 33076366 PMCID: PMC7587580 DOI: 10.3390/molecules25204729] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/11/2020] [Accepted: 10/12/2020] [Indexed: 02/06/2023] Open
Abstract
Over the past decade, the vast amount of information generated through structural and biophysical studies of GPCRs has provided unprecedented mechanistic insight into the complex signalling behaviour of these receptors. With this recent information surge, it has also become increasingly apparent that in order to reproduce the various effects that lipids and membranes exert on the biological function for these allosteric receptors, in vitro studies of GPCRs need to be conducted under conditions that adequately approximate the native lipid bilayer environment. In the first part of this review, we assess some of the more general effects that a membrane environment exerts on lipid bilayer-embedded proteins such as GPCRs. This is then followed by the consideration of more specific effects, including stoichiometric interactions with specific lipid subtypes. In the final section, we survey a range of different membrane mimetics that are currently used for in vitro studies, with a focus on NMR applications.
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Affiliation(s)
| | | | | | - Daniel Nietlispach
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK; (A.J.Y.J.); (F.G.); (A.T.)
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Gao Y, Hu H, Ramachandran S, Erickson JW, Cerione RA, Skiniotis G. Structures of the Rhodopsin-Transducin Complex: Insights into G-Protein Activation. Mol Cell 2019; 75:781-790.e3. [PMID: 31300275 DOI: 10.1016/j.molcel.2019.06.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/16/2019] [Accepted: 06/04/2019] [Indexed: 12/31/2022]
Abstract
Rhodopsin (Rho), a prototypical G-protein-coupled receptor (GPCR) in vertebrate vision, activates the G-protein transducin (GT) by catalyzing GDP-GTP exchange on its α subunit (GαT). To elucidate the determinants of GT coupling and activation, we obtained cryo-EM structures of a fully functional, light-activated Rho-GT complex in the presence and absence of a G-protein-stabilizing nanobody. The structures illustrate how GT overcomes its low basal activity by engaging activated Rho in a conformation distinct from other GPCR-G-protein complexes. Moreover, the nanobody-free structures reveal native conformations of G-protein components and capture three distinct conformers showing the GαT helical domain (αHD) contacting the Gβγ subunits. These findings uncover the molecular underpinnings of G-protein activation by visual rhodopsin and shed new light on the role played by Gβγ during receptor-catalyzed nucleotide exchange.
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Affiliation(s)
- Yang Gao
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Hongli Hu
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sekar Ramachandran
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jon W Erickson
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA.
| | - Georgios Skiniotis
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Onken MD, Makepeace CM, Kaltenbronn KM, Kanai SM, Todd TD, Wang S, Broekelmann TJ, Rao PK, Cooper JA, Blumer KJ. Targeting nucleotide exchange to inhibit constitutively active G protein α subunits in cancer cells. Sci Signal 2018; 11:eaao6852. [PMID: 30181242 PMCID: PMC6279241 DOI: 10.1126/scisignal.aao6852] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Constitutively active G protein α subunits cause cancer, cholera, Sturge-Weber syndrome, and other disorders. Therapeutic intervention by targeted inhibition of constitutively active Gα subunits in these disorders has yet to be achieved. We found that constitutively active Gαq in uveal melanoma (UM) cells was inhibited by the cyclic depsipeptide FR900359 (FR). FR allosterically inhibited guanosine diphosphate-for-guanosine triphosphate (GDP/GTP) exchange to trap constitutively active Gαq in inactive, GDP-bound Gαβγ heterotrimers. Allosteric inhibition of other Gα subunits was achieved by the introduction of an FR-binding site. In UM cells driven by constitutively active Gαq, FR inhibited second messenger signaling, arrested cell proliferation, reinstated melanocytic differentiation, and stimulated apoptosis. In contrast, FR had no effect on BRAF-driven UM cells. FR promoted UM cell differentiation by reactivating polycomb repressive complex 2 (PRC2)-mediated gene silencing, a heretofore unrecognized effector system of constitutively active Gαq in UM. Constitutively active Gαq and PRC2 therefore provide therapeutic targets for UM. The development of FR analogs specific for other Gα subunit subtypes may provide novel therapeutic approaches for diseases driven by constitutively active Gα subunits or multiple G protein-coupled receptors (GPCRs) where targeting a single receptor is ineffective.
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Affiliation(s)
- Michael D Onken
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Carol M Makepeace
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Kevin M Kaltenbronn
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stanley M Kanai
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tyson D Todd
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Shiqi Wang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas J Broekelmann
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Prabakar Kumar Rao
- Department of Ophthalmology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Kendall J Blumer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Ilyaskina OS, Lemoine H, Bünemann M. Lifetime of muscarinic receptor-G-protein complexes determines coupling efficiency and G-protein subtype selectivity. Proc Natl Acad Sci U S A 2018; 115:5016-5021. [PMID: 29686069 PMCID: PMC5948956 DOI: 10.1073/pnas.1715751115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are essential for the detection of extracellular stimuli by cells and transfer the encoded information via the activation of functionally distinct subsets of heterotrimeric G proteins into intracellular signals. Despite enormous achievements toward understanding GPCR structures, major aspects of the GPCR-G-protein selectivity mechanism remain unresolved. As this can be attributed to the lack of suitable and broadly applicable assays, we set out to develop a quantitative FRET-based assay to study kinetics and affinities of G protein binding to activated GPCRs in membranes of permeabilized cells in the absence of nucleotides. We measured the association and dissociation kinetics of agonist-induced binding of Gi/o, Gq/11, Gs, and G12/13 proteins to muscarinic M1, M2, and M3 receptors in the absence of nucleotides between fluorescently labeled G proteins and receptors expressed in mammalian cells. Our results show a strong quantitative correlation between not the on-rates of G-protein-M3-R interactions but rather the affinities of Gq and Go proteins to M3-Rs, their GPCR-G-protein lifetime and their coupling efficiencies determined in intact cells, suggesting that the G-protein subtype-specific affinity to the activated receptor in the absence of nucleotides is, in fact, a major determinant of the coupling efficiency. Our broadly applicable FRET-based assay represents a fast and reliable method to quantify the intrinsic affinity and relative coupling selectivity of GPCRs toward all G-protein subtypes.
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Affiliation(s)
- Olga S Ilyaskina
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, University of Marburg, 35032 Marburg, Germany
| | - Horst Lemoine
- Department of Laser Medicine, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Moritz Bünemann
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, University of Marburg, 35032 Marburg, Germany;
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8
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Khatoon SS, Rehman M, Rahman A. The Role of Natural Products in Alzheimer's and Parkinson's Disease. STUDIES IN NATURAL PRODUCTS CHEMISTRY 2018. [DOI: 10.1016/b978-0-444-64058-1.00003-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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9
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Navaratnarajah P, Gershenson A, Ross EM. The binding of activated Gα q to phospholipase C-β exhibits anomalous affinity. J Biol Chem 2017; 292:16787-16801. [PMID: 28842497 DOI: 10.1074/jbc.m117.809673] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/22/2017] [Indexed: 01/01/2023] Open
Abstract
Upon activation by the Gq family of Gα subunits, Gβγ subunits, and some Rho family GTPases, phospholipase C-β (PLC-β) isoforms hydrolyze phosphatidylinositol 4,5-bisphosphate to the second messengers inositol 1,4,5-trisphosphate and diacylglycerol. PLC-β isoforms also function as GTPase-activating proteins, potentiating Gq deactivation. To elucidate the mechanism of this mutual regulation, we measured the thermodynamics and kinetics of PLC-β3 binding to Gαq FRET and fluorescence correlation spectroscopy, two physically distinct methods, both yielded Kd values of about 200 nm for PLC-β3-Gαq binding. This Kd is 50-100 times greater than the EC50 for Gαq-mediated PLC-β3 activation and for the Gαq GTPase-activating protein activity of PLC-β. The measured Kd was not altered either by the presence of phospholipid vesicles, phosphatidylinositol 4,5-bisphosphate and Ca2+, or by the identity of the fluorescent labels. FRET-based kinetic measurements were also consistent with a Kd of 200 nm We determined that PLC-β3 hysteresis, whereby PLC-β3 remains active for some time following either Gαq-PLC-β3 dissociation or PLC-β3-potentiated Gαq deactivation, is not sufficient to explain the observed discrepancy between EC50 and Kd These results indicate that the mechanism by which Gαq and PLC-β3 mutually regulate each other is far more complex than a simple, two-state allosteric model and instead is probably kinetically determined.
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Affiliation(s)
- Punya Navaratnarajah
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
| | - Anne Gershenson
- the Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003-9292
| | - Elliott M Ross
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
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Goto K, Doi M, Wang T, Kunisue S, Murai I, Okamura H. G-protein-coupled receptor signaling through Gpr176, Gz, and RGS16 tunes time in the center of the circadian clock [Review]. Endocr J 2017; 64:571-579. [PMID: 28502923 DOI: 10.1507/endocrj.ej17-0130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute an immensely important class of drug targets with diverse clinical applications. There are still more than 120 orphan GPCRs whose cognate ligands and physiological functions are not known. A set of circadian pacemaker neurons that governs daily rhythms in behavior and physiology resides in the suprachiasmatic nucleus (SCN) in the brain. Malfunction of the circadian clock has been linked to a multitude of diseases, such as sleeping disorders, obesity, diabetes, cardiovascular diseases, and cancer, which makes the clock an attractive target for drug development. Here, we review a recently identified role of Gpr176 in the SCN. Gpr176 is an SCN-enriched orphan GPCR that sets the pace of the circadian clock in the SCN. Even without known ligand, this orphan receptor has an agonist-independent basal activity to reduce cAMP signaling. A unique cAMP-repressing G-protein subclass Gz is required for the activity of Gpr176. We also provide an overview on the circadian regulation of G-protein signaling, with an emphasis on a role for the regulator of G-protein signaling 16 (RGS16). RGS16 is indispensable for the circadian regulation of cAMP in the SCN. Developing drugs that target the SCN remains an unfulfilled opportunity for the circadian pharmacology. This review argues for the potential impact of focusing on GPCRs in the SCN for the purpose of tuning the body clock.
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Affiliation(s)
- Kaoru Goto
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Masao Doi
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Tianyu Wang
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Sumihiro Kunisue
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Iori Murai
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hitoshi Okamura
- Department of Systems Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
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Tateyama M, Kubo Y. Stabilizing effects of G protein on the active conformation of adenosine A 1 receptor differ depending on G protein type. Eur J Pharmacol 2016; 788:122-131. [DOI: 10.1016/j.ejphar.2016.06.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/15/2016] [Accepted: 06/15/2016] [Indexed: 01/07/2023]
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Yoo JH, Shi DS, Grossmann AH, Sorensen LK, Tong Z, Mleynek TM, Rogers A, Zhu W, Richards JR, Winter JM, Zhu J, Dunn C, Bajji A, Shenderovich M, Mueller AL, Woodman SE, Harbour JW, Thomas KR, Odelberg SJ, Ostanin K, Li DY. ARF6 Is an Actionable Node that Orchestrates Oncogenic GNAQ Signaling in Uveal Melanoma. Cancer Cell 2016; 29:889-904. [PMID: 27265506 PMCID: PMC5027844 DOI: 10.1016/j.ccell.2016.04.015] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Revised: 10/16/2015] [Accepted: 04/29/2016] [Indexed: 12/12/2022]
Abstract
Activating mutations in Gαq proteins, which form the α subunit of certain heterotrimeric G proteins, drive uveal melanoma oncogenesis by triggering multiple downstream signaling pathways, including PLC/PKC, Rho/Rac, and YAP. Here we show that the small GTPase ARF6 acts as a proximal node of oncogenic Gαq signaling to induce all of these downstream pathways as well as β-catenin signaling. ARF6 activates these diverse pathways through a common mechanism: the trafficking of GNAQ and β-catenin from the plasma membrane to cytoplasmic vesicles and the nucleus, respectively. Blocking ARF6 with a small-molecule inhibitor reduces uveal melanoma cell proliferation and tumorigenesis in a mouse model, confirming the functional relevance of this pathway and suggesting a therapeutic strategy for Gα-mediated diseases.
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Affiliation(s)
- Jae Hyuk Yoo
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Dallas S Shi
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Allie H Grossmann
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA; ARUP Laboratories, University of Utah, Salt Lake City, UT 84112, USA
| | - Lise K Sorensen
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA
| | - ZongZhong Tong
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA; Key Laboratory for Human Disease Gene Study, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu 610072, China
| | - Tara M Mleynek
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA
| | - Aaron Rogers
- Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
| | - Weiquan Zhu
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Division of Cardiovascular Medicine, Department of Medicine, University of Utah, Salt Lake City, UT 84112, USA
| | - Jackson R Richards
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Jacob M Winter
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA
| | - Jie Zhu
- Department of Ophthalmology and Shiley Eye Institute, University of California, San Diego, La Jolla, CA 92093, USA
| | - Christine Dunn
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA
| | - Ashok Bajji
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA; VioGen Biosciences LLC, Salt Lake City, UT 84119, USA
| | - Mark Shenderovich
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA; Mol3D Research LLC, Salt Lake City, UT 84124, USA
| | - Alan L Mueller
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA
| | - Scott E Woodman
- Department of Melanoma Medical Oncology, Department of Systems Biology, University of Texas, MD Anderson Cancer Center, Houston, TX 77054, USA
| | - J William Harbour
- Ocular Oncology Service, Bascom Palmer Eye Institute and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Kirk R Thomas
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Division of Hematology, Department of Medicine, University of Utah, Salt Lake City, UT 84112, USA
| | - Shannon J Odelberg
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Division of Cardiovascular Medicine, Department of Medicine, University of Utah, Salt Lake City, UT 84112, USA; Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT 84112, USA
| | - Kirill Ostanin
- Navigen Inc., 383 Colorow Drive, Salt Lake City, UT 84108, USA.
| | - Dean Y Li
- Department of Medicine, Program in Molecular Medicine, University of Utah, 15 North 2030 East, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112, USA; Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA; ARUP Laboratories, University of Utah, Salt Lake City, UT 84112, USA; Key Laboratory for Human Disease Gene Study, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu 610072, China; Division of Cardiovascular Medicine, Department of Medicine, University of Utah, Salt Lake City, UT 84112, USA; Department of Cardiology, VA Salt Lake City Health Care System, Salt Lake City, UT 84112, USA.
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Puente EI, De la Cruz L, Arenas I, Elias-Viñas D, Garcia DE. Voltage-Independent Inhibition of the Tetrodotoxin-Sensitive Sodium Currents by Oxotremorine and Angiotensin II in Rat Sympathetic Neurons. Mol Pharmacol 2016; 89:476-83. [DOI: 10.1124/mol.115.101931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 02/10/2016] [Indexed: 01/16/2023] Open
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14
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Kubo T, Ding WG, Toyoda F, Fujii Y, Omatsu-Kanbe M, Matsuura H. Phosphatidylinositol4-phosphate 5-kinase prevents the decrease in the HERG potassium current induced by Gq protein-coupled receptor stimulation. J Pharmacol Sci 2015; 127:127-34. [PMID: 25704028 DOI: 10.1016/j.jphs.2014.11.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 11/19/2014] [Accepted: 11/20/2014] [Indexed: 10/24/2022] Open
Abstract
The human ether-a-go-go-related gene (HERG) potassium current (IHERG) has been shown to decrease in amplitude following stimulation with Gq protein-coupled receptors (GqRs), such as α1-adrenergic and M1-muscarinic receptors (α1R and M1R, respectively), at least partly via the reduction of membrane phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). The present study was designed to investigate the modulation of HERG channels by PI(4,5)P2 and phosphatidylinositol4-phosphate 5-kinase (PI(4)P5-K), a synthetic enzyme of PI(4,5)P2. Whole-cell patch-clamp recordings were used to examine the activity of HERG channels expressed heterologously in Chinese Hamster Ovary cells. The stimulation of α1R with phenylephrine or M1R with acetylcholine decreased the amplitude of IHERG accompanied by a significant acceleration of deactivation kinetics and the effects on IHERG were significantly attenuated in cells expressing PI(4)P5-K. The density of IHERG in cells expressing GqRs alone was significantly increased by the coexpression of PI(4)P5-K without significant differences in the voltage dependence of activation and deactivation kinetics. The kinase-deficient substitution mutant, PI(4)P5-K-K138A did not have these counteracting effects on the change in IHERG by M1R stimulation. These results suggest that the current density of IHERG is closely dependent on the membrane PI(4,5)P2 level, which is regulated by PI(4)P5-K and GqRs and that replenishing PI(4,5)P2 by PI(4)P5-K recovers IHERG.
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Affiliation(s)
- Taeko Kubo
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan; Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan; Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd, Osaka 554-0022, Japan
| | - Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan
| | - Futoshi Toyoda
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan
| | - Yusuke Fujii
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan; Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan
| | - Mariko Omatsu-Kanbe
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan
| | - Hiroshi Matsuura
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan.
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Hille B, Dickson E, Kruse M, Falkenburger B. Dynamic metabolic control of an ion channel. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:219-47. [PMID: 24560147 DOI: 10.1016/b978-0-12-397897-4.00008-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G-protein-coupled receptors mediate responses to external stimuli in various cell types. We are interested in the modulation of KCNQ2/3 potassium channels by the Gq-coupled M1 muscarinic (acetylcholine) receptor (M1R). Here, we describe development of a mathematical model that incorporates all known steps along the M1R signaling cascade and accurately reproduces the macroscopic behavior we observe when KCNQ2/3 currents are inhibited following M1R activation. Gq protein-coupled receptors of the plasma membrane activate phospholipase C (PLC) which cleaves the minor plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into the second messengers diacylgycerol and inositol 1,4,5-trisphosphate, leading to calcium release, protein kinase C (PKC) activation, and PI(4,5)P2 depletion. Combining optical and electrical techniques with knowledge of relative abundance of each signaling component has allowed us to develop a kinetic model and determine that (i) M1R activation and M1R/Gβ interaction are fast; (ii) Gαq/Gβ separation and Gαq/PLC interaction have intermediate time constants; (iii) the amount of activated PLC limits the rate of KCNQ2/3 suppression; (iv) weak PLC activation can elicit robust calcium signals without net PI(4,5)P2 depletion or KCNQ2/3 channel inhibition; and (v) depletion of PI(4,5)P2, and not calcium/CaM or PKC-mediated phosphorylation, closes KCNQ2/3 potassium channels, thereby increasing neuronal excitability.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Eamonn Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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Wirotanseng LN, Kuner R, Tappe-Theodor A. Gq rather than G11 preferentially mediates nociceptor sensitization. Mol Pain 2013; 9:54. [PMID: 24156378 PMCID: PMC4016015 DOI: 10.1186/1744-8069-9-54] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 10/20/2013] [Indexed: 01/05/2023] Open
Abstract
Background The Gq/11-protein signaling mechanism is essential throughout the nervous system, but little is known about the contribution of the individual G-protein GPCR signaling branches towards nociceptor activation and their specific role on nociceptor sensitization. We aimed to unravel the contribution of the Gq/11-signaling pathway towards nociceptor activation via a variety of classical inflammatory mediators signalling via different G-protein GPCRs and investigated the specific contribution of the individual Gq and G11 G-Proteins in nociceptors. Findings Using different transgenic mouse lines, lacking Gαq, Gα11 or both α-subunit of the G-proteins in primary nociceptive neurons, we analyzed the mechanical- and heat-sensitivity upon application of different GPCR-agonists that are known to play an important role under inflammatory conditions (e.g. ATP, Glutamate, Serotonin etc.). We found that the Gq/11-GPCR signaling branch constitutes a primary role in the manifestation of mechanical allodynia and a minor role in the development of thermal hyperalgesia. Moreover, with respect to the mediators used here, the Gq-protein is the principle G-protein among the Gq/11-protein family in nociceptive neurons leading to nociceptor sensitization. Conclusions Our results demonstrate that the Gq/11 signaling branch plays a primary role in nociceptor sensitization upon stimulation with classical GPCR ligands, contributing primarily towards the development of mechanically allodynia. Moreover, the deletion of the individual G-proteins led to the finding that the Gq-protein dominates the signalling machinery of the Gq/11 family of G-proteins in nociceptive neurons.
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Affiliation(s)
| | | | - Anke Tappe-Theodor
- Pharmacology Institut, University of Heidelberg, Im Neuenheimer Feld 366, Heidelberg, D-69120, Germany.
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Abstract
The dorsal striatum, with its functional microcircuits galore, serves as the primary gateway of the basal ganglia and is known to play a key role in implicit learning. Initially, excitatory inputs from the cortex and thalamus arrive on the direct and indirect pathways, where the precise flow of information is then regulated by local GABAergic interneurons. The balance of excitatory and inhibitory transmission in the dorsal striatum is modulated by neuromodulators such as dopamine and acetylcholine. Under pathophysiological states in the dorsal striatum, an alteration in excitatory and inhibitory transmission may underlie dysfunctional motor control. Here, we review the cellular connections and modulation of striatal microcircuits and propose that modulating the excitatory and inhibitory balance in synaptic transmission of the dorsal striatum is important for regulating locomotion.
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Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Gα proteins. Proc Natl Acad Sci U S A 2012; 109:7275-9. [PMID: 22529365 DOI: 10.1073/pnas.1202943109] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteins with similar crystal structures can have dissimilar rates of substrate binding and catalysis. Here we used molecular dynamics simulations and biochemical analysis to determine the role of intradomain and interdomain motions in conferring distinct activation rates to two Gα proteins, Gα(i1) and GPA1. Despite high structural similarity, GPA1 can activate itself without a receptor, whereas Gα(i1) cannot. We found that motions in these proteins vary greatly in type and frequency. Whereas motion is greatest in the Ras domain of Gα(i1), it is greatest in helices αA and αB from the helical domain of GPA1. Using protein chimeras, we show that helix αA from GPA1 is sufficient to confer rapid activation to Gα(i1). Gα(i1) has less intradomain motion than GPA1 and instead displays interdomain displacement resembling that observed in a receptor-heterotrimer crystal complex. Thus, structurally similar proteins can have distinct atomic motions that confer distinct activation mechanisms.
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Pohanka M. Alpha7 nicotinic acetylcholine receptor is a target in pharmacology and toxicology. Int J Mol Sci 2012; 13:2219-2238. [PMID: 22408449 PMCID: PMC3292018 DOI: 10.3390/ijms13022219] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 01/26/2012] [Accepted: 02/14/2012] [Indexed: 01/18/2023] Open
Abstract
Alpha7 nicotinic acetylcholine receptor (α7 nAChR) is an important part of the cholinergic nerve system in the brain. Moreover, it is associated with a cholinergic anti-inflammatory pathway in the termination of the parasympathetic nervous system. Antagonists of α7 nAChR are a wide group represented by conotoxin and bungarotoxin. Even Alzheimer's disease drug memantine acting as an antagonist in its side pathway belongs in this group. Agonists of α7 nAChR are suitable for treatment of multiple cognitive dysfunctions such as Alzheimer's disease or schizophrenia. Inflammation or even sepsis can be ameliorated by the agonistic acting compounds. Preparations RG3487, SEN34625/WYE-103914, SEN12333, ABT-107, Clozapine, GTS-21, CNI-1493, and AR-R17779 are representative examples of the novel compounds with affinity toward the α7 nAChR. Pharmacological, toxicological, and medicinal significance of α7 nAChR are discussed throughout this paper.
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Affiliation(s)
- Miroslav Pohanka
- Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 50001 Hradec Kralove, Czech Republic; E-Mail: ; Tel.: +420-973253091; Fax: +420-973253091
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Harden TK, Waldo GL, Hicks SN, Sondek J. Mechanism of activation and inactivation of Gq/phospholipase C-β signaling nodes. Chem Rev 2011; 111:6120-9. [PMID: 21988240 PMCID: PMC3626114 DOI: 10.1021/cr200209p] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T Kendall Harden
- Department of Pharmacology and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
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Artificial membrane-like environments for in vitro studies of purified G-protein coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:225-33. [PMID: 21851807 DOI: 10.1016/j.bbamem.2011.07.047] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/28/2011] [Accepted: 07/29/2011] [Indexed: 12/31/2022]
Abstract
Functional reconstitution of transmembrane proteins remains a significant barrier to their biochemical, biophysical, and structural characterization. Studies of seven-transmembrane G-protein coupled receptors (GPCRs) in vitro are particularly challenging because, ideally, they require access to the receptor on both sides of the membrane as well as within the plane of the membrane. However, understanding the structure and function of these receptors at the molecular level within a native-like environment will have a large impact both on basic knowledge of cell signaling and on pharmacological research. The goal of this article is to review the main classes of membrane mimics that have been, or could be, used for functional reconstitution of GPCRs. These include the use of micelles, bicelles, lipid vesicles, nanodiscs, lipidic cubic phases, and planar lipid membranes. Each of these approaches is evaluated with respect to its fundamental advantages and limitations and its applications in the field of GPCR research. This article is part of a Special Issue entitled: Membrane protein structure and function.
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Wanjerkhede SM, Bapi RS. Role of CAMKII in reinforcement learning: a computational model of glutamate and dopamine signaling pathways. BIOLOGICAL CYBERNETICS 2011; 104:397-424. [PMID: 21701878 DOI: 10.1007/s00422-011-0439-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2011] [Accepted: 05/30/2011] [Indexed: 05/31/2023]
Abstract
Timely release of dopamine (DA) at the striatum seems to be important for reinforcement learning (RL) mediated by the basal ganglia. Houk et al. (in: Houk et al (eds) Models of information processing in the basal ganglia, (1995) proposed a cellular signaling pathway model to characterize the interaction between DA and glutamate pathways that have a role in RL. The model simulation results, using GENESIS KINETIKIT simulator, point out that there is not only prolongation of duration as proposed by Houk et al. (1995), but also an enhancement in the amplitude of autophosphorylation of CaMKII. Further, the autophosphorylated form of CaMKII may form a basis for the "eligibility trace" condition required in RL. This simulation study is the first of its kind to support the comprehensive theoretical proposal of Houk et al. (1995).
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Affiliation(s)
- Shesharao M Wanjerkhede
- Department of Computer Science, Guru Nanak Dev Engineering College, Bidar, Karanataka, India.
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Phospholipase C-η1 is activated by intracellular Ca(2+) mobilization and enhances GPCRs/PLC/Ca(2+) signaling. Cell Signal 2011; 23:1022-9. [PMID: 21262355 DOI: 10.1016/j.cellsig.2011.01.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 01/14/2011] [Indexed: 11/20/2022]
Abstract
Phospholipase C-η1 (PLC-η1) is the most recently identified PLC isotype and is primarily expressed in nerve tissue. However, its functional role is unclear. In the present study, we report for the first time that PLC-η1 acts as a signal amplifier in G protein-coupled receptor (GPCR)-mediated PLC and Ca(2+) signaling. Short-hairpin RNA (shRNA)-mediated knockdown of endogenous PLC-η1 reduced lysophosphatidic acid (LPA)-, bradykinin (BK)-, and PACAP-induced PLC activity in mouse neuroblastoma Neuro2A (N2A) cells, indicating that PLC-η1 participates in GPCR-mediated PLC activation. Interestingly, ionomycin-induced PLC activity was significantly decreased by PLC-η1, but not PLC-η2, knockdown. In addition, we found that intracellular Ca(2+) source is enough for PLC-η1 activation. Furthermore, the IP(3) receptor inhibitor, 2-APB, inhibited LPA-induced PLC activity in control N2A cells, whereas this effect was not observed in PLC-η1 knockdown N2A cells, suggesting a pivotal role of intracellular Ca(2+) mobilization in PLC-η1 activation. Finally, we found that LPA-induced ERK1/2 phosphorylation and expression of the downstream target gene, krox-24, were significantly decreased by PLC-η1 knockdown, and these knockdown effects were abolished by 2-APB. Taken together, our results strongly suggest that PLC-η1 is activated via intracellular Ca(2+) mobilization from the ER, and therefore amplifies GPCR-mediated signaling.
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Dickinson BA, Jo J, Seok H, Son GH, Whitcomb DJ, Davies CH, Sheng M, Collingridge GL, Cho K. A novel mechanism of hippocampal LTD involving muscarinic receptor-triggered interactions between AMPARs, GRIP and liprin-alpha. Mol Brain 2009; 2:18. [PMID: 19534762 PMCID: PMC2701934 DOI: 10.1186/1756-6606-2-18] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Accepted: 06/17/2009] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Long-term depression (LTD) in the hippocampus can be induced by activation of different types of G-protein coupled receptors, in particular metabotropic glutamate receptors (mGluRs) and muscarinic acetylcholine receptors (mAChRs). Since mGluRs and mAChRs activate the same G-proteins and isoforms of phospholipase C (PLC), it would be expected that these two forms of LTD utilise the same molecular mechanisms. However, we find a distinct mechanism of LTD involving GRIP and liprin-alpha. RESULTS Whilst both forms of LTD require activation of tyrosine phosphatases and involve internalisation of AMPARs, they use different molecular interactions. Specifically, mAChR-LTD, but not mGluR-LTD, is blocked by peptides that inhibit the binding of GRIP to the AMPA receptor subunit GluA2 and the binding of GRIP to liprin-alpha. Thus, different receptors that utilise the same G-proteins can regulate AMPAR trafficking and synaptic efficacy via distinct molecular mechanisms. CONCLUSION Our results suggest that mAChR-LTD selectively involves interactions between GRIP and liprin-alpha. These data indicate a novel mechanism of synaptic plasticity in which activation of M1 receptors results in AMPAR endocytosis, via a mechanism involving interactions between GluA2, GRIP and liprin-alpha.
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Affiliation(s)
- Bryony A Dickinson
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology (LINE), Faculty of Medicine and Dentistry, University of Bristol, Whitson Street, Bristol BS1 3NY, UK.
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Song KS, Lee TJ, Kim K, Chung KC, Yoon JH. cAMP-responding element-binding protein and c-Ets1 interact in the regulation of ATP-dependent MUC5AC gene expression. J Biol Chem 2008; 283:26869-78. [PMID: 18676374 DOI: 10.1074/jbc.m802507200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Exogenous ATP activates purinoreceptors on the cell surface that regulate diverse cellular functions, including mucous cell secretion in the respiratory epithelium. In this study, ATP increased MUC5AC mRNA in primary human nasal epithelial cells and in NCI-H292 pulmonary adenocarcinoma cells in vitro. ATP-induced MUC5AC mRNA was mediated by phospholipase Cbeta3. A dominant-negative mutation in the PDZ binding domain of PLCbeta3 inhibited ATP-induced MUC5AC gene expression. ATP sequentially activated the phosphorylation of Akt, ERK1/2, p38, RSK1, and cAMP-responding element-binding protein (CREB) in a protein kinase C-independent manner. ATP-induced MUC5AC mRNA levels were regulated by CREB via direct interaction with c-Ets1 on the MUC5AC gene promoter (located -938 to -930). Effects of CREB and c-Ets1 were additive. Inhibition of either CREB or c-Ets1 inhibited ATP-induced MUC5AC gene expression. Stimulation with ATP caused the direct binding of CREB and c-Ets1 to the MUC5AC promoter, increasing the phosphorylation of c-Ets1. Chromatin immunoprecipitation assays demonstrated that in the presence of ATP, both c-Ets1 and CREB bound to the MUC5AC promoter. The effects of exogenous ATP on MUC5AC gene expression are mediated by a complex regulatory cascade controlling interactions between CREB and c-Ets1 that bind to a promoter element in the MUC5AC gene enhancing MUC5AC gene transcription. ATP-dependent activation of MUC5AC gene expression via CREB-c-Ets1 may contribute to mucous cell hypersecretion associated with common respiratory disorders.
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Affiliation(s)
- Kyoung Seob Song
- Airway Mucus Institute, Yonsei University College of Medicine, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-752, Korea
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Makita N, Sato J, Rondard P, Fukamachi H, Yuasa Y, Aldred MA, Hashimoto M, Fujita T, Iiri T. Human G(salpha) mutant causes pseudohypoparathyroidism type Ia/neonatal diarrhea, a potential cell-specific role of the palmitoylation cycle. Proc Natl Acad Sci U S A 2007; 104:17424-9. [PMID: 17962410 PMCID: PMC2077272 DOI: 10.1073/pnas.0708561104] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Indexed: 01/08/2023] Open
Abstract
Pseudohypoparathyroidism type Ia (PHP-Ia) results from the loss of one allele of G(salpha), causing resistance to parathyroid hormone and other hormones that transduce signals via G(s). Most G(salpha)mutations cause the complete loss of protein expression, but some cause loss of function only, and these have provided valuable insights into the normal function of G proteins. Here we have analyzed a mutant G(salpha) (alphas-AVDT) harboring AVDT amino acid repeats within its GDP/GTP binding site, which was identified in unique patients with PHP-Ia accompanied by neonatal diarrhea. Biochemical and intact cell analyses showed that alphas-AVDT is unstable but constitutively active as a result of rapid GDP release and reduced GTP hydrolysis. This instability underlies the PHP-Ia phenotype. alphas-AVDT is predominantly localized in the cytosol, but in rat and mouse small intestine epithelial cells (IEC-6 and DIF-12 cells) alphas-AVDT was found to be localized predominantly in the membrane where adenylyl cyclase is present and constitutive increases in cAMP accumulation occur in parallel. The likely cause of this membrane localization is the inhibition of an activation-dependent decrease in alphas palmitoylation. Upon the overexpression of acyl-protein thioesterase 1, however, alphas-AVDT translocates from the membrane to the cytosol, and the constitutive accumulation of cAMP becomes attenuated. These results suggest that PHP-Ia results from the instability of alphas-AVDT and that the accompanying neonatal diarrhea may result from its enhanced constitutive activity in the intestine. Hence, palmitoylation may control the activity and localization of G(salpha) in a cell-specific manner.
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Affiliation(s)
- Noriko Makita
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Junichiro Sato
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, 141 Rue de la Cardonille, 34094 Montpellier Cedex 5, France
| | - Hiroshi Fukamachi
- Department of Molecular Oncology, Graduate School of Medicine and Dentistry, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan; and
| | - Yasuhito Yuasa
- Department of Molecular Oncology, Graduate School of Medicine and Dentistry, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan; and
| | - Micheala A. Aldred
- Division of Medical Genetics, University of Leicester and Leicestershire Genetics Service, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
| | - Makiko Hashimoto
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Toshiro Fujita
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Taroh Iiri
- *Department of Endocrinology and Nephrology, University of Tokyo School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
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Sternweis PC, Smrcka AV. G proteins in signal transduction: the regulation of phospholipase C. CIBA FOUNDATION SYMPOSIUM 2007; 176:96-106; discussion 106-11. [PMID: 8299429 DOI: 10.1002/9780470514450.ch7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The hydrolysis of phosphatidylinositol 4,5-bisphosphate by specific phospholipase C (PLC) enzymes produces two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol. Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) of the Gq subfamily activate the PLC beta 1 isoform of PLC. We have purified three isozymes of PLC beta: PLC beta 1 and PLC beta 3 from rat brain and PLC beta 2 from HL-60 cells. Whereas the beta 1 and beta 2 isozymes appear restricted to a few cell types, beta 3 is broadly distributed. Gq alpha (the alpha subunit of the Gq subfamily) can activate all three isoforms but PLC beta 2 is much less sensitive. Thus all three enzymes are potential effectors for pertussis toxin-insensitive regulation by hormones. The three beta isozymes can also be activated by purified beta gamma subunits. The PLC beta 3 isoform gives the greatest activation with beta gamma; PLC beta 1 is least responsive. The results indicate that all the known isoforms of mammalian PLC beta can be regulated at unique sites by both Gq alpha and beta gamma subunits. The effect of beta gamma subunits may provide a pathway for the regulation of PLC beta isozymes by pertussis toxin-sensitive G proteins or may indicate that the alpha subunit of Gq and its associated beta gamma both participate in regulation of the same phospholipase molecule.
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Affiliation(s)
- P C Sternweis
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041
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Citro S, Malik S, Oestreich EA, Radeff-Huang J, Kelley GG, Smrcka AV, Brown JH. Phospholipase Cepsilon is a nexus for Rho and Rap-mediated G protein-coupled receptor-induced astrocyte proliferation. Proc Natl Acad Sci U S A 2007; 104:15543-8. [PMID: 17878312 PMCID: PMC2000505 DOI: 10.1073/pnas.0702943104] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phospholipase Cepsilon (PLCepsilon) has been suggested to transduce signals from small GTPases, but its biological function has not yet been clarified. Using astrocytes from PLCepsilon-deficient mice, we demonstrate that endogenous G protein-coupled receptors (GPCRs) for lysophosphatidic acid, sphingosine 1-phosphate, and thrombin regulate phosphoinositide hydrolysis primarily through PLCepsilon. Stimulation by lysophospholipids occurs through G(i), whereas thrombin activates PLC through Rho. Further studies reveal that PLCepsilon is required for thrombin- but not LPA-induced sustained ERK activation and DNA synthesis, providing a novel mechanism for GPCR and Rho signaling to cell proliferation. The requirement for PLCepsilon in this pathway can be explained by its role as a guanine nucleotide exchange factor for Rap1. Thus, PLCepsilon serves to transduce mitogenic signals through a mechanism distinct from its role in generation of PLC-derived second messengers.
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Affiliation(s)
- Simona Citro
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Emily A. Oestreich
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Julie Radeff-Huang
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
| | - Grant G. Kelley
- Departments of Medicine and Pharmacology, State University of New York Upstate Medical University, Syracuse, NY 13210; and
| | - Alan V. Smrcka
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Joan Heller Brown
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
- To whom correspondence should be addressed. E-mail:
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Suga H, Haga T. Ligand screening system using fusion proteins of G protein-coupled receptors with G protein alpha subunits. Neurochem Int 2007; 51:140-64. [PMID: 17659814 DOI: 10.1016/j.neuint.2007.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/07/2007] [Accepted: 06/08/2007] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) constitute one of the largest families of genes in the human genome, and are the largest targets for drug development. Although a large number of GPCR genes have recently been identified, ligands have not yet been identified for many of them. Various assay systems have been employed to identify ligands for orphan GPCRs, but there is still no simple and general method to screen for ligands of such GPCRs, particularly of G(i)-coupled receptors. We have examined whether fusion proteins of GPCRs with G protein alpha subunit (Galpha) could be utilized for ligand screening and showed that the fusion proteins provide an effective method for the purpose. This article focuses on the followings: (1) characterization of GPCR genes and GPCRs, (2) identification of ligands for orphan GPCRs, (3) characterization of GPCR-Galpha fusion proteins, and (4) identification of ligands for orphan GPCRs using GPCR-Galpha fusion proteins.
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Affiliation(s)
- Hinako Suga
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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32
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Sawyer GW, Ehlert FJ, Shults CA. Cysteine Pairs in the Third Intracellular Loop of the Muscarinic M1Acetylcholine Receptor Play a Role in Agonist-Induced Internalization. J Pharmacol Exp Ther 2007; 324:196-205. [PMID: 17540859 DOI: 10.1124/jpet.107.123695] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We determined the functional role of a small domain in the third intracellular loop of the human muscarinic M(1) (hM(1)) receptor. Using site-directed mutagenesis, several mutant hM(1) receptors were made possessing either a deletion or point mutations within the third intracellular loop domain (252)PETPPGRCCRCC(263). Wild-type and mutant hM(1) receptors were transiently expressed in Chinese hamster ovary cells, and the effects of each mutation on radioligand binding, agonist-mediated phosphoinositide hydrolysis, and agonist-induced internalization were determined. The mutant receptors exhibited a modest reduction in affinity for [(3)H]N-methylscopolamine (pK(D) = approximately 9.0) and a moderately increased binding capacity relative to the wild-type receptor. This moderate increase in binding capacity was associated with small increases in the maximal response and potency of carbachol for eliciting phosphoinositide hydrolysis through the mutant receptors (pEC(50) = approximately 5.5) relative to wild-type (pEC(50) = 5.35 +/- 0.05). In contrast, carbachol-induced internalization of mutant hM(1) receptors possessing either C259A/C260A or C262A/C263A or both double point mutations was significantly reduced compared to the wild-type hM(1) receptor. Of the hM(1) receptor mutants tested, those possessing a C262D/C263D double point mutation had the least carbachol-induced internalization. The desensitization and down-regulation of receptors possessing either Cys/Ala or Cys/Asp double point mutations were similar to those observed for the wild-type hM(1) receptor. Collectively, these observations suggest that Cys pairs Cys259/Cys260 and Cys262/Cys263 play an important role in the agonist-induced internalization of hM(1) receptors.
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Affiliation(s)
- Gregory W Sawyer
- Department of Biochemistry and Microbiology, Center for Health Sciences, Oklahoma State University, 1111 W. 17th Street, Tulsa, OK 74107-1898, USA.
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33
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Quirk K, Roberts DJ, Strange PG. Mechanisms of G protein activation via the D2 dopamine receptor: evidence for persistent receptor/G protein interaction after agonist stimulation. Br J Pharmacol 2007; 151:144-52. [PMID: 17351658 PMCID: PMC2012977 DOI: 10.1038/sj.bjp.0707197] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this report is to study mechanisms of G protein activation by agonists. EXPERIMENTAL APPROACH The association and dissociation of guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding at G proteins in membranes of CHO cells stably transfected with the human dopamine D(2short) receptor was studied in the presence of a range of agonists. KEY RESULTS Binding of [(35)S]GTPgammaS was dissociable in the absence of agonist and dissociation was accelerated both in rate and extent by dopamine, an effect which was blocked by the dopamine D(2) receptor antagonist raclopride and by suramin, which inhibits receptor/G protein interaction. A range of agonists of varying efficacy increased the rate of dissociation of [(35)S]GTPgammaS binding, with the more efficacious agonists resulting in faster dissociation. Agonists were able to dissociate about 70% of the pre-bound [(35)S]GTPgammaS, leaving a component which may not be accessible to the agonist-bound receptor. The dissociable component of the [(35)S]GTPgammaS binding was reduced with longer association times and increased [(35)S]GTPgammaS concentrations. CONCLUSIONS AND IMPLICATIONS These data are consistent with [(35)S]GTPgammaS binding being initially to receptor-linked G proteins and then to G proteins which have separated from the agonist bound receptor. Under the conditions used typically for [(35)S]GTPgammaS binding assays, therefore, much of the agonist-receptor complex remains in proximity to G proteins after they have been activated by agonist.
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Affiliation(s)
- K Quirk
- School of Pharmacy, University of Reading Whiteknights, Reading, UK
| | - D J Roberts
- School of Pharmacy, University of Reading Whiteknights, Reading, UK
| | - P G Strange
- School of Pharmacy, University of Reading Whiteknights, Reading, UK
- Author for correspondence:
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Parallel inactivation of Y2 receptor and G-proteins in CHO cells by pertussis toxin. ACTA ACUST UNITED AC 2006; 139:128-35. [PMID: 17175038 DOI: 10.1016/j.regpep.2006.10.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 10/22/2006] [Indexed: 02/04/2023]
Abstract
The Y(2) receptor for neuropeptide Y (NPY) interacts with pertussis toxin (PTX)-sensitive G-proteins, but little is known about interdependence of their levels and functions. We found that PTX reduces Y(2) receptors expressed in CHO cells in parallel to inactivation of Gi G-proteins, to loss of inhibition by Y(2) agonists of forskolin-stimulated adenylyl cyclase, and to decrease in the binding of GTP-gamma-S. These losses were attenuated by the endosome alkalinizer ammonium chloride. Affinity of the Y(2) receptor was not changed by PTX treatment. Prolonged treatment induced a large decrease of Y(2) receptor immunoreactivity (more than 70% in 48 h). The Gi(3) alpha-subunit immunoreactivity decreased slowly (about 46% in 48 h). There was a significant increase in Gq alpha immunoreactivity and in fraction of Y(2) binding sensitive to a Gq-selective antagonist. Possibly linked to that, the surface Y(2) sites and the internalization of the Y(2) receptor were less than 40% reduced. However, the abundant masked Y(2) sites were eliminated by the toxin, and could be mainly coupled to PTX-sensitive G-proteins.
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35
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Tang W, Tu Y, Nayak SK, Woodson J, Jehl M, Ross EM. Gbetagamma inhibits Galpha GTPase-activating proteins by inhibition of Galpha-GTP binding during stimulation by receptor. J Biol Chem 2005; 281:4746-53. [PMID: 16407201 DOI: 10.1074/jbc.m510573200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gbetagamma subunits modulate several distinct molecular events involved with G protein signaling. In addition to regulating several effector proteins, Gbetagamma subunits help anchor Galpha subunits to the plasma membrane, promote interaction of Galpha with receptors, stabilize the binding of GDP to Galpha to suppress spurious activation, and provide membrane contact points for G protein-coupled receptor kinases. Gbetagamma subunits have also been shown to inhibit the activities of GTPase-activating proteins (GAPs), both phospholipase C (PLC)-betas and RGS proteins, when assayed in solution under single turnover conditions. We show here that Gbetagamma subunits inhibit G protein GAP activity during receptor-stimulated, steady-state GTPase turnover. GDP/GTP exchange catalyzed by receptor requires Gbetagamma in amounts approximately equimolar to Galpha, but GAP inhibition was observed with superstoichiometric Gbetagamma. The potency of inhibition varied with the GAP and the Galpha subunit, but half-maximal inhibition of the GAP activity of PLC-beta1 was observed with 5-10 nM Gbetagamma, which is at or below the concentrations of Gbetagamma needed for regulation of physiologically relevant effector proteins. The kinetics of GAP inhibition of both receptor-stimulated GTPase activity and single turnover, solution-based GAP assays suggested a competitive mechanism in which Gbetagamma competes with GAPs for binding to the activated, GTP-bound Galpha subunit. An N-terminal truncation mutant of PLC-beta1 that cannot be directly regulated by Gbetagamma remained sensitive to inhibition of its GAP activity, suggesting that the Gbetagamma binding site relevant for GAP inhibition is on the Galpha subunit rather than on the GAP. Using fluorescence resonance energy transfer between cyan or yellow fluorescent protein-labeled G protein subunits and Alexa532-labeled RGS4, we found that Gbetagamma directly competes with RGS4 for high-affinity binding to Galpha(i)-GDP-AlF4.
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Affiliation(s)
- Wei Tang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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36
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Quintero JL, Arenas MI, García DE. The antidepressant imipramine inhibits M current by activating a phosphatidylinositol 4,5-bisphosphate (PIP2)-dependent pathway in rat sympathetic neurones. Br J Pharmacol 2005; 145:837-43. [PMID: 15852030 PMCID: PMC1576193 DOI: 10.1038/sj.bjp.0706239] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Little is known about the intracellular actions of imipramine (IMI) in the regulation of ion channels. We tested the action of IMI on the intracellular cascade that regulates M current (I(M)) in superior cervical ganglion neurones (SCGs). Dialysis of the cells with GDPbetaS, a G protein signaling blocker, did not disrupt the inhibition of I(M). When we incubated the cells with the phospholipase C (PLC) inhibitor U73122, it prevented the I(M) inhibition by IMI. Also, when we dialyzed the cells with an intracellular Ca2+ chelator, it did not disrupt I(M) inhibition by IMI, as occurs in the M1 cascade. When we incubated the cells with the generic kinase inhibitor wortmannin, it prevented the recovery of I(M) from the inhibition by IMI. Also, when we applied phosphatidylinositol 4,5-bisphosphate (PIP2) intracellularly, it diminished the inhibition of I(M) by IMI. Our findings suggest that PLC is the target for IMI, that recovery of I(M) needs lipid phosphorylation for PIP2 resynthesis, and that IMI inhibits I(M) by activating a PLC-dependent pathway, likely by decreasing the concentration of PIP2.
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Affiliation(s)
- Jania L Quintero
- Department of Physiology, Faculty of Medicine, UNAM, Apdo. Post. 70250, CP 04510 México, DF, México
| | - Maria Isabel Arenas
- Department of Physiology, Faculty of Medicine, UNAM, Apdo. Post. 70250, CP 04510 México, DF, México
| | - David E García
- Department of Physiology, Faculty of Medicine, UNAM, Apdo. Post. 70250, CP 04510 México, DF, México
- Author for correspondence:
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37
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Panchalingam S, Undie AS. Physicochemical modulation of agonist-induced [35s]GTPgammaS binding: implications for coexistence of multiple functional conformations of dopamine D1-like receptors. J Recept Signal Transduct Res 2005; 25:125-46. [PMID: 16149770 DOI: 10.1080/10799890500184948] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Dopamine agonist-stimulated [35S]GTPgammaS binding to membrane G proteins was studied in select brain regions under experimental conditions that permit the activation of receptor coupling to the G proteins Gi, Gs, or Gq. Agents studied were agonists known to be effective at various dopamine receptor/effector systems and included quinelorane (D2-like/Gi), SKF38393 (D1-like/Gq, D1-like/Gs), SKF85174 (D1-like/Gs), and SKF83959 (D1-like/Gq). Dopamine and SKF38393 significantly stimulated [35S]GTPgammaS binding to normal striatal membranes by 161% and 67% above controls. Deoxycholate, which enhances agonist-induced phospholipase C (PLC) stimulation, markedly enhanced the agonistic effects of dopamine and SKF38393 to 530% and 637% above controls, respectively. The enhancing effects of deoxycholate were reversed if it was washed off the membranes before agonist addition. The thiol-reducing agent, dithiothreitol, completely abolished the effects of SKF38393 and SKF83959, whereas SKF85174 effects were augmented. Agonist responses were concentration-related, and highest efficacies were obtained in the hippocampus, thus paralleling both the brain regional distribution and agonist efficacies previously observed in phosphoinositide hydrolysis assays. These findings suggest that D1-like receptor conformations that mediate agonist stimulation of Gs/adenylylcyclase may be structurally different from those that mediate Gq/PLC activation. Although the exact mechanism of deoxycholate's effect awaits elucidation, the results are consistent with the emerging concept of functional selectivity whereby deoxycholate could create a membrane environment that facilitates the transformation of the receptor from a conformation that activates Gs/adenylylcyclase to one that favors Gq/PLC signaling.
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Affiliation(s)
- Sandra Panchalingam
- Neuropharmacology Laboratory, Department of Pharmaceutical Sciences, School of Pharmacy and The Program in Neuroscience, University of Maryland, Baltimore, Maryland 21201-1075, USA
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38
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Bornheimer SJ, Maurya MR, Farquhar MG, Subramaniam S. Computational modeling reveals how interplay between components of a GTPase-cycle module regulates signal transduction. Proc Natl Acad Sci U S A 2004; 101:15899-904. [PMID: 15520372 PMCID: PMC524695 DOI: 10.1073/pnas.0407009101] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Heterotrimeric G protein signaling is regulated by signaling modules composed of heterotrimeric G proteins, active G protein-coupled receptors (Rs), which activate G proteins, and GTPase-activating proteins (GAPs), which deactivate G proteins. We term these modules GTPase-cycle modules. The local concentrations of these proteins are spatially regulated between plasma membrane microdomains and between the plasma membrane and cytosol, but no data or models are available that quantitatively explain the effect of such regulation on signaling. We present a computational model of the GTPase-cycle module that predicts that the interplay of local G protein, R, and GAP concentrations gives rise to 16 distinct signaling regimes and numerous intermediate signaling phenomena. The regimes suggest alternative modes of the GTPase-cycle module that occur based on defined local concentrations of the component proteins. In one mode, signaling occurs while G protein and receptor are unclustered and GAP eliminates signaling; in another, G protein and receptor are clustered and GAP can rapidly modulate signaling but does not eliminate it. Experimental data from multiple GTPase-cycle modules is interpreted in light of these predictions. The latter mode explains previously paradoxical data in which GAP does not alter maximal current amplitude of G protein-activated ion channels, but hastens signaling. The predictions indicate how variations in local concentrations of the component proteins create GTPase-cycle modules with distinctive phenotypes. They provide a quantitative framework for investigating how regulation of local concentrations of components of the GTPase-cycle module affects signaling.
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Affiliation(s)
- Scott J Bornheimer
- Departments of Chemistry and Biochemistry, Cellular and Molecular Medicine, and Bioengineering and San Diego Supercomputer Center, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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39
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Abstract
We studied modulation of current in human embryonic kidney tsA-201 cells coexpressing rat erg1 channels with M(1) muscarinic receptors. Maximal current was inhibited 30% during muscarinic receptor stimulation, with a small positive shift of the midpoint of activation. Inhibition was attenuated by coexpression of the regulator of G-protein signalling RGS2 or of a dominant-negative protein, G(q), but not by N-ethylmaleimide or C3 toxin. Overexpression of a constitutively active form of G(q) (but not of G(13) or of G(s)) abolished the erg current. Hence it is likely that G(q/11), and not G(i/o) or G(13), mediates muscarinic inhibition. Muscarinic suppression of erg was attenuated by chelating intracellular Ca(2+) to < 1 nm free Ca(2+) with 20 mm BAPTA in the pipette, but suppression was normal if internal Ca(2+) was strongly clamped to a 129 nm free Ca(2+) level with a BAPTA buffer and this was combined with numerous other measures to prevent intracellular Ca(2+) transients (pentosan polysulphate, preincubation with thapsigargin, and removal of extracellular Ca(2+)). Hence a minimum amount of Ca(2+) was necessary for the inhibition, but a Ca(2+) elevation was not. The ATP analogue AMP-PCP did not prevent inhibition. The protein kinase C (PKC) blockers staurosporine and bisindolylmaleimide I did not prevent inhibition, and the PKC-activating phorbol ester PMA did not mimic it. Neither the tyrosine kinase inhibitor genistein nor the tyrosine phosphatase inhibitor dephostatin prevented inhibition by oxotremorine-M. Hence protein kinases are not needed. Experiments with a high concentration of wortmannin were consistent with recovery being partially dependent on PIP(2) resynthesis. Wortmannin did not prevent muscarinic inhibition. Our studies of muscarinic inhibition of erg current suggest a role for phospholipase C, but not the classical downstream messengers, such as PKC or a calcium transient.
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Affiliation(s)
- Wiebke Hirdes
- Department of Physiology and Biophysics, University of Washington School of Medicine, G-424 Health Sciences Building, Box 357290, Seattle, WA 98195-7290, USA
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40
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Fukuda K. Application of mesenchymal stem cells for the regeneration of cardiomyocyte and its use for cell transplantation therapy. Hum Cell 2004; 16:83-94. [PMID: 15005238 DOI: 10.1111/j.1749-0774.2003.tb00138.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We have isolated a cardiomyogenic cell line (CMG cell) from murine bone marrow mesenchymal stem cells. The cells showed a fibroblast-like morphology, but the morphology changed after 5-azacytidine exposure. They began spontaneous beating after 2 weeks, and expressed ANP and BNP. Electron microscopy revealed a cardiomyocyte-like ultrastructure. These cells had several types of action potentials; sinus node-like and ventricular cell-like action potentials. The isoform of contractile protein genes indicated that their muscle phenotype was similar to fetal ventricular cardiomyocytes. They expressed alpha1A, alpha1B, alpha1D, beta1, and beta2 adrenergic and M1 and M2 muscarinic receptors. Stimulation with phenylephrine, isoproterenol and carbachol increased ERK phosphorylation and second messengers. Isoproterenol increased the beating rate, which was blocked with CGP20712A (beta1-selective blocker). These findings indicated that cell transplantation therapy for the patients with heart failure might possibly be achieved using the regenerated cardiomyocytes from autologous bone marrow cells in the near future.
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Affiliation(s)
- Keiichi Fukuda
- Institute for Advanced Cardiac Therapeutics, Keio University School of Medicine, Tokyo, Japan.
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41
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Wilson BA, Ho M. Pasteurella multocida toxin as a tool for studying Gq signal transduction. Rev Physiol Biochem Pharmacol 2004; 152:93-109. [PMID: 15455260 PMCID: PMC1761692 DOI: 10.1007/s10254-004-0032-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Pasteurella multocida toxin (PMT) stimulates and subsequently uncouples phospholipase C (PLC) signal transduction through its selective action on the Galphaq subunit. This review summarizes what is currently known about the molecular action of PMT on Gq and the resulting cellular effects. Examples are presented illustrating the use of PMT as a powerful tool for dissecting the molecular mechanisms involving pertussis toxin (PT)-insensitive heterotrimeric G proteins.
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Affiliation(s)
- B A Wilson
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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42
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Tall GG, Gilman AG. Purification and functional analysis of Ric-8A: a guanine nucleotide exchange factor for G-protein alpha subunits. Methods Enzymol 2004; 390:377-88. [PMID: 15488189 DOI: 10.1016/s0076-6879(04)90023-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ric-8A (synembryn) has been shown to accelerate the in vitro guanine nucleotide exchange activities of most G-protein alpha subunits (with the exception of Galphas). Methods are presented in this article for the purification of Ric-8A and functional analysis of the effects Ric-8A has on G-protein alpha subunit guanine nucleotide-binding activities. The use of Ric-8A to prepare GTPgammaS-Galpha and nucleotide-free Galpha (in complex with Ric-8A) is described.
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Affiliation(s)
- Gregory G Tall
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75390, USA
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43
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Woodard GE, Rosado JA. G-Protein Coupled Receptors and Calcium Signaling in Development. Curr Top Dev Biol 2004; 65:189-210. [PMID: 15642384 DOI: 10.1016/s0070-2153(04)65007-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Affiliation(s)
- Geoffrey E Woodard
- Metabolic Diseases Branch, National Institute of Diabetes Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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44
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Tosetti P, Parente V, Taglietti V, Dunlap K, Toselli M. Chick RGS2L demonstrates concentration-dependent selectivity for pertussis toxin-sensitive and -insensitive pathways that inhibit L-type Ca2+ channels. J Physiol 2003; 549:157-69. [PMID: 12651916 PMCID: PMC2342929 DOI: 10.1113/jphysiol.2002.034439] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In neuronal cells, the influx of Ca2+ ions through voltage-dependent L-type calcium (L) channels couples excitation to multiple cellular functions. In addition to voltage, several neurotransmitters, hormones and cytokines regulate L channel gating via binding to G-protein-coupled receptors. Intracellular molecules that modify G-protein activity - such as regulator of G-protein-signalling (RGS) proteins - are therefore potential candidates for regulating Ca2+ influx through L channels. Here we show that a novel RGS2 splice variant from chick dorsal root ganglion (DRG) neurons, RGS2L, reduces bradykinin (BK)-mediated inhibition of neuronal L channels and accelerates recovery from inhibition. Chick RGS2 reduces the inhibition mediated by both the pertussis toxin (PTX)-sensitive (Gi/o-coupled) and the PTX-insensitive (presumably Gq/11-coupled) pathways. However, we demonstrate for the first time in a living cell that the extent of coupling to each pathway varies with RGS2L concentration. A low concentration of recombinant chick RGS2L (10 nM) preferentially reduces the inhibition mediated by the PTX-insensitive pathway, whereas a 100-fold higher concentration attenuates both PTX-sensitive- and PTX-insensitive-mediated components equally. Our data suggest that factors promoting RGS2L gene induction may regulate Ca2+ influx through L channels by recruiting low-affinity interactions with Gi/o that are absent at basal RGS2L levels.
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Affiliation(s)
- Patrizia Tosetti
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
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45
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Liu L, Rittenhouse AR. Arachidonic acid mediates muscarinic inhibition and enhancement of N-type Ca2+ current in sympathetic neurons. Proc Natl Acad Sci U S A 2003; 100:295-300. [PMID: 12496347 PMCID: PMC140955 DOI: 10.1073/pnas.0136826100] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
N-type Ca(2+) channels participate in acute activity-dependent processes such as regulation of Ca(2+)-activated K(+) channels and in more prolonged events such as gene transcription and long-term depression. A slow postsynaptic M(1) muscarinic receptor-mediated modulation of N-type current in superior cervical ganglion neurons may be important in regulating these processes. This slow pathway inhibits N-type current by using a diffusible second messenger that has remained unidentified for more than a decade. Using whole-cell patch-clamp techniques, which isolate the slow pathway, we found that the muscarinic agonist oxotremorine methiodide not only inhibits currents at positive potentials but enhances N-type current at negative potentials. Enhancement was also observed in cell-attached patches. These findings provide evidence for N-type Ca(2+)-current enhancement by a classical neurotransmitter. Moreover, enhancement and inhibition of current by oxotremorine methiodide mimics modulation observed with direct application of a low concentration of arachidonic acid (AA). Although no transmitter has been reported to use AA as a second messenger to modulate any Ca(2+) current in either neuronal or nonneuronal cells, we nevertheless tested whether a fatty acid signaling cascade was involved. Blocking phospholipase C, phospholipase A(2), or AA but not AA metabolism minimized muscarinic modulation of N-type current, supporting the participation of these molecules in the slow pathway. A role for the G protein G(q) was also confirmed by blocking muscarinic modulation of Ca(2+) currents with anti-G(qalpha) antibody. Our finding that AA participates in the slow pathway strongly suggests that it may be the previously unknown diffusible second messenger.
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Affiliation(s)
- Liwang Liu
- Program in Neuroscience, Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester 01655, USA
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46
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Abstract
We have isolated a cardiomyogenic cell line (CMG cell) from murine bone marrow mesenchymal stem cells. The cells showed a fibroblast-like morphology, but the morphology changed after 5-azacytidine exposure. They began spontaneous beating after 2 weeks, and expressed ANP and BNP. Electron microscopy revealed a cardiomyocyte-like ultrastructure. These cells had several types of action potentials: sinus-node-like and ventricular-cell-like action potentials. The isoform of contractile protein genes indicated that their muscle phenotype was similar to fetal ventricular cardiomyocytes. They expressed alpha 1A, alpha 1B, alpha 1D, beta 1, and beta 2 adrenergic and M1 and M2 muscarinic receptors. Stimulation with phenylephrine, isoproterenol and carbachol increased ERK phosphorylation and second messengers. Isoproterenol increased the beating rate, which was blocked with CGP20712A (beta 1-selective blocker). These findings indicated that cell transplantation therapy for the patients with heart failure might possibly be achieved using the regenerated cardiomyocytes from autologous bone marrow cells in the near future.
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Affiliation(s)
- Keiichi Fukuda
- Institute for Advanced Cardiac Therapeutics, Institute of Integrated Medical Research 7S1/7S2, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
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47
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McClatchy DB, Knudsen CR, Clark BF, Kahn RA, Hall RA, Levey AI. Novel interaction between the M4 muscarinic acetylcholine receptor and elongation factor 1A2. J Biol Chem 2002; 277:29268-74. [PMID: 12048193 DOI: 10.1074/jbc.m203081200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of the muscarinic acetylcholine receptor (mAChR) family, consisting of five subtypes (M1-M5), produces a variety of physiological effects throughout the central nervous system. However, the role of each individual subtype remains poorly understood. To further elucidate signal transduction pathways for specific subtypes, we used the most divergent portion of the subtypes, the intracellular third (i3) loop, as bait to identify interacting proteins. Using a brain pull-down assay, we identify elongation factor 1A2 (eEF1A2) as a specific binding partner to the i3 loop of M4, and not to M1 or M2. In addition, we demonstrate a direct interaction between these proteins. In the rat striatum, the M4 mAChR colocalizes with eEF1A2 in the soma and neuropil. In PC12 cells, endogenous eEF1A2 co-immunoprecipitates with the endogenous M4 mAChR, but not with the endogenous M1 mAChR. In our in vitro model, M4 dramatically accelerates nucleotide exchange of eEF1A2, a GTP-binding protein. This indicates the M4 mAChR is a guanine exchange factor for eEF1A2. eEF1A2 is an essential GTP-binding protein for protein synthesis. Thus, our data suggest a novel role for M4 in the regulation of protein synthesis through its interaction with eEF1A2.
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Affiliation(s)
- Daniel B McClatchy
- Center for Neurodegenerative Diseases, Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Mukhopadhyay S, Ross EM. Quench-flow kinetic measurement of individual reactions of G-protein-catalyzed GTPase cycle. Methods Enzymol 2002; 344:350-69. [PMID: 11771396 DOI: 10.1016/s0076-6879(02)44727-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- Suchetana Mukhopadhyay
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Ferroni S, Marchini C, Ogata T, Schubert P. Recovery of deficient cholinergic calcium signaling by adenosine in cultured rat cortical astrocytes. J Neurosci Res 2002; 68:615-21. [PMID: 12111851 DOI: 10.1002/jnr.10248] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The regulation of the cholinergic calcium signaling in astroglial cells is thought to play a crucial role in the pathogenesis of Alzheimer's disease. We investigated the action of the cell modulator adenosine on acetylcholine (Ach)-mediated intracellular calcium ([Ca(2+)](i)) transients in cultured rat cortical astrocytes using the Ca(2+) imaging technique. The stable adenosine analog 2-chloroadenosine (2ClA) potentiated the [Ca(2+)](i) rise induced by activation of muscarinic Ach receptors by shifting approximately 30-fold the half-effective Ach concentration. This 2ClA effect was maintained upon removal of extracellular Ca(2+), indicating that Ach-induced [Ca(2+)](i) elevation was due mainly to Ca(2+) mobilization from intracellular stores. Pharmacological studies demonstrated that the 2ClA action was mediated by A1 receptors. Incubation with pertussis toxin abrogated the 2ClA effect but left unchanged the [Ca(2+)](i) rise produced by Ach alone. The [Ca(2+)](i) response elicited by Ach alone was abolished upon blockade of muscarinic receptor subtypes that stimulate phospholipase C, whereas the [Ca(2+)](i) elevation generated by the combined action of subthreshold Ach and 2ClA was not affected. Collectively, these results suggest that the impaired cholinergic signaling, the cardinal symptom of Alzheimer's disease, can be reinforced at the second messenger level by an alternative intracellular Ca(2+) mobilizing path, which can be brought into play by the concomitant activation of A1 purinoceptors and muscarinic receptors negatively coupled to adenylyl cyclase.
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Affiliation(s)
- Stefano Ferroni
- Department of Human and General Physiology, University of Bologna, Bologna, Italy.
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Chuang SC, Zhao W, Young SR, Conquet F, Bianchi R, Wong RKS. Activation of group I mGluRs elicits different responses in murine CA1 and CA3 pyramidal cells. J Physiol 2002; 541:113-21. [PMID: 12015424 PMCID: PMC2290298 DOI: 10.1113/jphysiol.2001.013309] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The group I metabotropic glutamate receptor agonist DHPG has been shown to produce two major effects on CA3 pyramidal cells at rest: a reduction in the background conductance and an activation of a voltage-gated inward current (I(mGluR(V))). Both effects contribute to depolarising CA3 pyramidal cells and the latter has been implicated in eliciting prolonged epileptiform population bursts. We observed that DHPG-induced depolarisation was smaller in CA1 pyramidal cells than in CA3 cells. Voltage clamp studies revealed that while DHPG elicited I(mGluR(V)) in CA3 pyramidal cells, such a response was absent in CA1 pyramidal cells. Both mGluR1 and mGluR5 have been localised in CA3 pyramidal cells, whereas only mGluR5 has been detected in CA1 pyramidal cells. Using mGluR1 knockout mice, we evaluated whether the absence of an I(mGluR(V)) response can be correlated with the absence of mGluR1. In these experiments, DHPG failed to elicit I(mGluR(V)) in CA3 pyramidal cells. This suggests that the smaller depolarising effects of DHPG on wild-type CA1 pyramidal cells is caused, at least in part, by the absence of I(mGluR(V)) in these cells and that the difference in the responses of CA1 and CA3 cells may be attributable to the lack of mGluR1 in CA1 pyramidal cells.
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Affiliation(s)
- Shih-Chieh Chuang
- Department of Physiology and Pharmacology, SUNY Health Science Center at Brooklyn, Brooklyn, NY 11203, USA
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