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Gao Y, Ryu H, Lee H, Kim YJ, Lee JH, Lee J. ER stress and unfolded protein response (UPR) signaling modulate GLP-1 receptor signaling in the pancreatic islets. Mol Cells 2024; 47:100004. [PMID: 38376482 PMCID: PMC10880082 DOI: 10.1016/j.mocell.2023.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 10/04/2023] [Accepted: 10/26/2023] [Indexed: 02/21/2024] Open
Abstract
Insulin is essential for maintaining normoglycemia and is predominantly secreted in response to glucose stimulation by β-cells. Incretin hormones, such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide, also stimulate insulin secretion. However, as obesity and type 2 diabetes worsen, glucose-dependent insulinotropic polypeptide loses its insulinotropic efficacy, whereas GLP-1 receptor (GLP-1R) agonists continue to be effective owing to its signaling switch from Gs to Gq. Herein, we demonstrated that endoplasmic reticulum (ER) stress induced a transition from Gs to Gq in GLP-1R signaling in mouse islets. Intriguingly, chemical chaperones known to alleviate ER stress, such as 4-PBA and TUDCA, enforced GLP-1R's Gq utilization rather than reversing GLP-1R's signaling switch induced by ER stress or obese and diabetic conditions. In addition, the activation of X-box binding protein 1 (XBP1) or activating transcription factor 6 (ATF6), 2 key ER stress-associated signaling (unfolded protein response) factors, promoted Gs utilization in GLP-1R signaling, whereas Gq employment by ER stress was unaffected by XBP1 or ATF6 activation. Our study revealed that ER stress and its associated signaling events alter GLP-1R's signaling, which can be used in type 2 diabetes treatment.
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Affiliation(s)
- Yurong Gao
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
| | - Hanguk Ryu
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
| | - Hyejin Lee
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
| | - Young-Joon Kim
- Department of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
| | - Ji-Hye Lee
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
| | - Jaemin Lee
- Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Republic of Korea
- New Biology Research Center, DGIST, Daegu 42988, Republic of Korea
- Well Aging Research Center, DGIST, Daegu 42988, Republic of Korea
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Gu Q, Wu J, Tian Y, Cheng S, Zhang ZC, Han J. Gαq splice variants mediate phototransduction, rhodopsin synthesis, and retinal integrity in Drosophila. J Biol Chem 2020; 295:5554-5563. [PMID: 32198182 PMCID: PMC7186184 DOI: 10.1074/jbc.ra120.012764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/19/2020] [Indexed: 11/06/2022] Open
Abstract
Heterotrimeric G proteins mediate a variety of signaling processes by coupling G protein-coupled receptors to intracellular effector molecules. In Drosophila, the Gαq gene encodes several Gαq splice variants, with the Gαq1 isoform protein playing a major role in fly phototransduction. However, Gαq1 null mutant flies still exhibit a residual light response, indicating that other Gαq splice variants or additional Gq α subunits are involved in phototransduction. Here, we isolated a mutant fly with no detectable light responses, decreased rhodopsin (Rh) levels, and rapid retinal degeneration. Using electrophysiological and genetic studies, biochemical assays, immunoblotting, real-time RT-PCR, and EM analysis, we found that mutations in the Gαq gene disrupt light responses and demonstrate that the Gαq3 isoform protein is responsible for the residual light response in Gαq1 null mutants. Moreover, we report that Gαq3 mediates rhodopsin synthesis. Depletion of all Gαq splice variants led to rapid light-dependent retinal degeneration, due to the formation stable Rh1-arrestin 2 (Arr2) complexes. Our findings clarify essential roles of several different Gαq splice variants in phototransduction and retinal integrity in Drosophila and reveal that Gαq3 functions in rhodopsin synthesis.
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Affiliation(s)
- Qiuxiang Gu
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Jinglin Wu
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yao Tian
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Shanshan Cheng
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Zi Chao Zhang
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China.
| | - Junhai Han
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China.
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Raghavan S, Singh NK, Gali S, Mani AM, Rao GN. Protein Kinase Cθ Via Activating Transcription Factor 2-Mediated CD36 Expression and Foam Cell Formation of Ly6C hi Cells Contributes to Atherosclerosis. Circulation 2019; 138:2395-2412. [PMID: 29991487 DOI: 10.1161/circulationaha.118.034083] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Although the role of thrombin in atherothrombosis is well studied, its role in the pathogenesis of diet-induced atherosclerosis is not known. METHODS Using a mouse model of diet-induced atherosclerosis and molecular biological approaches, here we have explored the role of thrombin and its G protein-coupled receptor signaling in diet-induced atherosclerosis. RESULTS In exploring the role of G protein-coupled receptor signaling in atherogenesis, we found that thrombin triggers foam cell formation via inducing CD36 expression, and these events require Par1-mediated Gα12-Pyk2-Gab1-protein kinase C (PKC)θ-dependent ATF2 activation. Genetic deletion of PKCθ in apolipoprotein E (ApoE)-/- mice reduced Western diet-induced plaque formation. Furthermore, thrombin induced Pyk2, Gab1, PKCθ, and ATF2 phosphorylation, CD36 expression, and foam cell formation in peritoneal macrophages of ApoE-/- mice. In contrast, thrombin only stimulated Pyk2 and Gab1 but not ATF2 phosphorylation or its target gene CD36 expression in the peritoneal macrophages of ApoE-/-:PKCθ-/- mice, and it had no effect on foam cell formation. In addition, the aortic root cross-sections of Western diet-fed ApoE-/- mice showed increased Pyk2, Gab1, PKCθ, and ATF2 phosphorylation and CD36 expression as compared with ApoE-/-:PKCθ-/- mice. Furthermore, although the monocytes from peripheral blood and the aorta of Western diet-fed ApoE-/- mice were found to contain more of Ly6Chi cells than Ly6Clo cells, the monocytes from Western diet-fed ApoE-/-:PKCθ-/- mice were found to contain more Ly6Clo cells than Ly6Chi cells. It is interesting to note that the Ly6Chi cells showed higher CD36 expression with enhanced capacity to form foam cells as compared with Ly6Clo cells. CONCLUSIONS These findings reveal for the first time that thrombin-mediated Par1-Gα12 signaling via targeting Pyk2-Gab1-PKCθ-ATF2-dependent CD36 expression might be playing a crucial role in diet-induced atherogenesis.
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Affiliation(s)
| | - Nikhlesh K Singh
- Department of Physiology, University of Tennessee Health Science Center, Memphis
| | - Sivaiah Gali
- Department of Physiology, University of Tennessee Health Science Center, Memphis
| | - Arul M Mani
- Department of Physiology, University of Tennessee Health Science Center, Memphis
| | - Gadiparthi N Rao
- Department of Physiology, University of Tennessee Health Science Center, Memphis
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Runegaard AH, Dencker D, Wörtwein G, Gether U. G protein-coupled receptor signaling in VTA dopaminergic neurons bidirectionally regulates the acute locomotor response to amphetamine but does not affect behavioral sensitization. Neuropharmacology 2019; 161:107663. [PMID: 31173760 DOI: 10.1016/j.neuropharm.2019.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/31/2019] [Accepted: 06/03/2019] [Indexed: 11/20/2022]
Abstract
Amphetamine (AMPH) acts as a substrate of the dopamine transporter (DAT) and causes a dramatic increase in extracellular dopamine (DA). Upon entering DA neurons, AMPH promotes DA efflux via DAT through a mechanism implicating depletion of DA from vesicular stores, activation of kinase pathways and transporter phosphorylation. Despite the role of intracellular signaling for AMPH action, it remains elusive how the response to AMPH is affected in vivo by metabotropic regulation via G protein coupled receptor signaling pathways. Here, we show by employment of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) that the acute hyperlocomotor response to AMPH is bidirectionally regulated by metabotropic input to VTA DA neurons with a markedly enhanced response upon activation of a Gs-coupled pathway and a markedly decreased locomotor response upon activation of a Gi-coupled pathway. The unique mechanism of action for AMPH was underlined by the absence of an effect of Gs activation on the locomotor response to the DAT inhibitor cocaine. Regardless of the profound effect on the acute AMPH response, repeated Gs activation or Gi activation did not affect development of AMPH sensitization. Furthermore, activation of a Gs-pathway or activation of a Gi-pathway in DA neurons did not have any effect on the AMPH-induced locomotor response in the AMPH sensitized mice. This suggests induction of alterations in DA neuronal functions that overrule the stimulatory or inhibitory effect of metabotropic input seen in drug-naïve mice. The data thereby underline the remarkable strength of maladaptive changes that occur upon intake of strong psychostimulants. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Abstract
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Photoacoustic
(optoacoustic) imaging can extract molecular information
with deeper tissue penetration than possible by fluorescence microscopy
techniques. However, there is currently still a lack of robust genetically
controlled contrast agents and molecular sensors that can dynamically
detect biological analytes of interest with photoacoustics. In a biomimetic
approach, we took inspiration from cuttlefish who can change their
color by relocalizing pigment-filled organelles in so-called chromatophore
cells under neurohumoral control. Analogously, we tested the use of
melanophore cells from Xenopus laevis, containing compartments (melanosomes) filled with strongly absorbing
melanin, as whole-cell sensors for optoacoustic imaging. Our results
show that pigment relocalization in these cells, which is dependent
on binding of a ligand of interest to a specific G protein-coupled
receptor (GPCR), can be monitored in vitro and in vivo using photoacoustic
mesoscopy. In addition to changes in the photoacoustic signal amplitudes,
we could furthermore detect the melanosome aggregation process by
a change in the frequency content of the photoacoustic signals. Using
bioinspired engineering, we thus introduce a photoacoustic pigment
relocalization sensor (PaPiReS) for molecular photoacoustic imaging
of GPCR-mediated signaling molecules.
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Affiliation(s)
- Antonella Lauri
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
- Institute of Developmental Genetics (IDG), Helmholtz Zentrum München, Neuherberg D-85764, Germany
| | - Dominik Soliman
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
| | - Murad Omar
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
| | - Anja Stelzl
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
- Institute of Developmental Genetics (IDG), Helmholtz Zentrum München, Neuherberg D-85764, Germany
| | - Vasilis Ntziachristos
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
| | - Gil G. Westmeyer
- Institute of Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg D-85764, Germany
- Institute of Developmental Genetics (IDG), Helmholtz Zentrum München, Neuherberg D-85764, Germany
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Piali L, Birker-Robaczewska M, Lescop C, Froidevaux S, Schmitz N, Morrison K, Kohl C, Rey M, Studer R, Vezzali E, Hess P, Clozel M, Steiner B, Bolli MH, Nayler O. Cenerimod, a novel selective S1P 1 receptor modulator with unique signaling properties. Pharmacol Res Perspect 2018; 5. [PMID: 29226621 PMCID: PMC5723703 DOI: 10.1002/prp2.370] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 09/27/2017] [Accepted: 10/06/2017] [Indexed: 11/08/2022] Open
Abstract
Sphingosine-1-phosphate receptor 1 (S1P1 ) modulators sequester circulating lymphocytes within lymph nodes, thereby preventing potentially pathogenic autoimmune cells from exiting into the blood stream and reaching inflamed tissues. S1P1 receptor modulation may thus offer potential to treat various autoimmune diseases. The first nonselective S1P1-5 receptor modulator FTY720/fingolimod/Gilenya® has successfully demonstrated clinical efficacy in relapsing forms of multiple sclerosis. However, cardiovascular, hepatic, and respiratory side-effects were reported and there is a need for novel S1P1 receptor modulators with better safety profiles. Here, we describe the discovery of cenerimod, a novel, potent and selective S1P1 receptor modulator with unique S1P1 receptor signaling properties and absence of broncho- and vasoconstrictor effects ex vivo and in vivo. Cenerimod dose-dependently lowered circulating lymphocyte counts in rats and mice after oral administration and effectively attenuated disease parameters in a mouse experimental autoimmune encephalitis (EAE) model. Cenerimod has potential as novel therapy with improved safety profile for autoimmune diseases with high unmet medical need.
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Affiliation(s)
- Luca Piali
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | | | | | | | | | | | - Markus Rey
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Rolf Studer
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - Patrick Hess
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - Beat Steiner
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
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Abstract
It has been nearly a century since Otto Loewi discovered that acetylcholine (ACh) release from the vagus produces bradycardia and reduced cardiac contractility. It is now known that parasympathetic control of the heart is mediated by ACh stimulation of G(i/o)-coupled muscarinic M2 receptors, which directly activate G protein-coupled inwardly rectifying potassium (GIRK) channels via Gβγ resulting in membrane hyperpolarization and inhibition of action potential (AP) firing. However, expression of M2R-GIRK signaling components in heterologous systems failed to recapitulate native channel gating kinetics. The missing link was identified with the discovery of regulator of G protein signaling (RGS) proteins, which act as GTPase-activating proteins to accelerate the intrinsic GTPase activity of Gα resulting in termination of Gα- and Gβγ-mediated signaling to downstream effectors. Studies in mice expressing an RGS-insensitive Gα(i2) mutant (G184S) implicated endogenous RGS proteins as key regulators of parasympathetic signaling in heart. Recently, two RGS proteins have been identified as critical regulators of M2R signaling in heart. RGS6 exhibits a uniquely robust expression in heart, especially in sinoatrial (SAN) and atrioventricular nodal regions. Mice lacking RGS6 exhibit increased bradycardia and inhibition of SAN AP firing in response to CCh as well as a loss of rapid activation and deactivation kinetics and current desensitization for ACh-induced GIRK current (I(KACh)). Similar findings were observed in mice lacking RGS4. Thus, dysregulation in RGS protein expression or function may contribute to pathologies involving aberrant electrical activity in cardiac pacemaker cells. Moreover, RGS6 expression was found to be up-regulated in heart under certain pathological conditions, including doxorubicin treatment, which is known to cause life-threatening cardiotoxicity and atrial fibrillation in cancer patients. On the other hand, increased vagal tone may be cardioprotective in heart failure where acetylcholinesterase inhibitors and vagal stimulation have been proposed as potential therapeutics. Together, these studies identify RGS proteins, especially RGS6, as new therapeutic targets for diseases such as sick sinus syndrome or other maladies involving abnormal autonomic control of the heart.
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Affiliation(s)
- Adele Stewart
- Department of Pharmacology, Carver College of Medicine, University of Iowa Iowa City, IA, USA
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