1
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Lei S, Meng Q, Liu Y, Liu Q, Dai A, Cai X, Wang MW, Zhou Q, Zhou H, Yang D. Distinct roles of the extracellular surface residues of glucagon-like peptide-1 receptor in β-arrestin 1/2 signaling. Eur J Pharmacol 2024; 968:176419. [PMID: 38360293 DOI: 10.1016/j.ejphar.2024.176419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 02/06/2024] [Accepted: 02/12/2024] [Indexed: 02/17/2024]
Abstract
Glucagon-like peptide-1 receptor (GLP-1R) is a prime drug target for type 2 diabetes and obesity. The ligand initiated GLP-1R interaction with G protein has been well studied, but not with β-arrestin 1/2. Therefore, bioluminescence resonance energy transfer (BRET), mutagenesis and an operational model were used to evaluate the roles of 85 extracellular surface residues on GLP-1R in β-arrestin 1/2 recruitment triggered by three representative GLP-1R agonists (GLP-1, exendin-4 and oxyntomodulin). Residues selectively regulated β-arrestin 1/2 recruitment for diverse ligands, and β-arrestin isoforms were identified. Mutation of residues K130-S136, L142 and Y145 on the transmembrane helix 1 (TM1)-extracellular domain (ECD) linker decreased β-arrestin 1 recruitment but increased β-arrestin 2 recruitment. Other extracellular loop (ECL) mutations, including P137A, Q211A, D222A and M303A selectively affected β-arrestin 1 recruitment while D215A, L217A, Q221A, S223A, Y289A, S301A, F381A and I382A involved more in β-arrestin 2 recruitment for the ligands. Oxyntomodulin engaged more broadly with GLP-1R extracellular surface to drive β-arrestin 1/2 recruitment than GLP-1 and exendin-4; I147, W214 and L218 involved in β-arrestin 1 recruitment, while L141, D215, L218, D293 and F381 in β-arrestin 2 recruitment for oxyntomodulin particularly. Additionally, the non-conserved residues on β-arrestin 1/2 C-domains contributed to interaction with GLP-1R. Further proteomic profiling of GLP-1R stably expressed cell line upon ligand stimulation with or without β-arrestin 1/2 overexpression demonstrated both commonly and biasedly regulated proteins and pathways associated with cognate ligands and β-arrestins. Our study offers valuable information about ligand induced β-arrestin recruitment mediated by GLP-1R and consequent intracellular signaling events.
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Affiliation(s)
- Saifei Lei
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China; School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
| | - Qian Meng
- State Key Laboratory of Chemical Biology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yanyun Liu
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Qiaofeng Liu
- School of Pharmacy, Fudan University, Shanghai, 201203, China
| | - Antao Dai
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Xiaoqing Cai
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Ming-Wei Wang
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, China; Research Center for Deepsea Bioresources, Sanya, Hainan, 572025, China; Department of Chemistry, School of Science, The University of Tokyo, Tokyo, 113-0033, Japan; School of Pharmacy, Hainan Medical University, Haikou, 570228, China
| | - Qingtong Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, China; Research Center for Deepsea Bioresources, Sanya, Hainan, 572025, China.
| | - Hu Zhou
- State Key Laboratory of Chemical Biology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
| | - Dehua Yang
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China; State Key Laboratory of Chemical Biology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China; School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210023, China; Research Center for Deepsea Bioresources, Sanya, Hainan, 572025, China.
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2
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McNeill SM, Lu J, Marion C Carino C, Inoue A, Zhao P, Sexton PM, Wootten D. The role of G protein-coupled receptor kinases in GLP-1R β-arrestin recruitment and internalisation. Biochem Pharmacol 2024; 222:116119. [PMID: 38461904 DOI: 10.1016/j.bcp.2024.116119] [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: 10/28/2023] [Revised: 01/11/2024] [Accepted: 03/07/2024] [Indexed: 03/12/2024]
Abstract
The glucagon-like peptide 1 receptor (GLP-1R) is a validated clinical target for the treatment of type 2 diabetes and obesity. Unlike most G protein-coupled receptors (GPCRs), the GLP-1R undergoes an atypical mode of internalisation that does not require β-arrestins. While differences in GLP-1R trafficking and β-arrestin recruitment have been observed between clinically used GLP-1R agonists, the role of G protein-coupled receptor kinases (GRKs) in affecting these pathways has not been comprehensively assessed. In this study, we quantified the contribution of GRKs to agonist-mediated GLP-1R internalisation and β-arrestin recruitment profiles using cells where endogenous β-arrestins, or non-visual GRKs were knocked out using CRISPR/Cas9 genome editing. Our results confirm the previously established atypical β-arrestin-independent mode of GLP-1R internalisation and revealed that GLP-1R internalisation is dependent on the expression of GRKs. Interestingly, agonist-mediated GLP-1R β-arrestin 1 and β-arrestin 2 recruitment were differentially affected by endogenous GRK knockout with β-arrestin 1 recruitment more sensitive to GRK knockout than β-arrestin 2 recruitment. Moreover, individual overexpression of GRK2, GRK3, GRK5 or GRK6 in a newly generated GRK2/3/4/5/6 HEK293 cells, rescued agonist-mediated β-arrestin 1 recruitment and internalisation profiles to similar levels, suggesting that there is no specific GRK isoform that drives these pathways. This study advances mechanistic understanding of agonist-mediated GLP-1R internalisation and provides novel insights into how GRKs may fine-tune GLP-1R signalling.
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Affiliation(s)
- Samantha M McNeill
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Victoria 3052, Australia
| | - Jessica Lu
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Victoria 3052, Australia; ARC Centre for Cryo-Electron Microscopy of Membrane Proteins (CCeMMP), Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Australia
| | - Carlo Marion C Carino
- Graduate School of Pharmaceutical Sciences, Tokohu University, Sendai, Miyagi 980-8578, Japan
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tokohu University, Sendai, Miyagi 980-8578, Japan
| | - Peishen Zhao
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Victoria 3052, Australia; ARC Centre for Cryo-Electron Microscopy of Membrane Proteins (CCeMMP), Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Australia
| | - Patrick M Sexton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Victoria 3052, Australia; ARC Centre for Cryo-Electron Microscopy of Membrane Proteins (CCeMMP), Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Australia.
| | - Denise Wootten
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Victoria 3052, Australia; ARC Centre for Cryo-Electron Microscopy of Membrane Proteins (CCeMMP), Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Australia.
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3
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Ghosh A, Peyot ML, Leung YH, Ravenelle F, Madiraju SRM, Prentki M. A peripherally restricted cannabinoid-1 receptor inverse agonist promotes insulin secretion and protects from cytokine toxicity in human pancreatic islets. Eur J Pharmacol 2023; 944:175589. [PMID: 36773683 DOI: 10.1016/j.ejphar.2023.175589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 01/30/2023] [Accepted: 02/08/2023] [Indexed: 02/11/2023]
Abstract
The cannabinoid receptor CB1R is expressed in pancreatic β-cells; CB1R increased activity is associated with diabetes, obesity, cardiovascular disorders as well as decreased insulin secretion and insulin resistance. CB1R was shown to signal through G-protein coupling as well as β-arrestins in β-cells. Peripherally restricted CB1R inverse agonists purportedly have beneficial effects on insulin secretion in β-cells, without the unwanted effects in the central nervous system. Here we show that a peripherally restricted CB1R inverse agonist, MRI-1891, augments glucose stimulated insulin secretion in isolated human pancreatic islets and mouse islets. The insulin secretion enhancing effect of MRI-1891 is comparable to exendin-4, an analogue of the glucagon like peptide-1 (GLP1). Moreover, MRI-1891 treatment protects isolated human islet cells against cytokine-induced apoptosis, similar to exendin-4. Thus, MRI-1891, a new class of CB1R inverse agonist, may be considered a potential therapeutic for both type 1 and type 2 diabetes because of its ability to protect pancreatic β-cells from cytokine toxicity and to promote insulin secretion.
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Affiliation(s)
- Anindya Ghosh
- Departments of Nutrition, Biochemistry and Molecular Medicine, Université de Montréal, Montreal Diabetes Research Center, CRCHUM, 900 Saint Denis Street, Montréal, QC, H2X 0A9, Canada
| | - Marie-Line Peyot
- Departments of Nutrition, Biochemistry and Molecular Medicine, Université de Montréal, Montreal Diabetes Research Center, CRCHUM, 900 Saint Denis Street, Montréal, QC, H2X 0A9, Canada
| | - Yat Hei Leung
- Departments of Nutrition, Biochemistry and Molecular Medicine, Université de Montréal, Montreal Diabetes Research Center, CRCHUM, 900 Saint Denis Street, Montréal, QC, H2X 0A9, Canada
| | - François Ravenelle
- Inversago Pharma Inc., 1100 Rene-Levesque West, Suite 1110, Montreal, QC, H3B 4N4, Canada
| | - S R Murthy Madiraju
- Departments of Nutrition, Biochemistry and Molecular Medicine, Université de Montréal, Montreal Diabetes Research Center, CRCHUM, 900 Saint Denis Street, Montréal, QC, H2X 0A9, Canada
| | - Marc Prentki
- Departments of Nutrition, Biochemistry and Molecular Medicine, Université de Montréal, Montreal Diabetes Research Center, CRCHUM, 900 Saint Denis Street, Montréal, QC, H2X 0A9, Canada.
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4
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El Eid L, Reynolds CA, Tomas A, Ben Jones. Biased Agonism and Polymorphic Variation at the GLP-1 Receptor: Implications for the Development of Personalised Therapeutics. Pharmacol Res 2022; 184:106411. [PMID: 36007775 DOI: 10.1016/j.phrs.2022.106411] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 08/16/2022] [Accepted: 08/18/2022] [Indexed: 10/15/2022]
Abstract
Glucagon-like peptide-1 receptor (GLP-1R) is a well-studied incretin hormone receptor and target of several therapeutic drugs for type 2 diabetes (T2D), obesity and, more recently, cardiovascular disease. Some signalling pathways downstream of GLP-1R may be responsible for drug adverse effects such as nausea, while others mediate therapeutic outcomes of incretin-based T2D therapeutics. Understanding the interplay between different factors that alter signalling, trafficking, and receptor activity, including biased agonism, single nucleotide polymorphisms and structural modifications is key to develop the next-generation of personalised GLP-1R agonists. However, these interactions remain poorly described, especially for novel therapeutics such as dual and tri-agonists that target more than one incretin receptor. Comparison of GLP-1R structures in complex with G proteins and different peptide and non-peptide agonists has revealed novel insights into important agonist-residue interactions and networks crucial for receptor activation, recruitment of G proteins and engagement of specific signalling pathways. Here, we review the latest knowledge on GLP-1R structure and activation, providing structural evidence for biased agonism and delineating important networks associated with this phenomenon. We survey current biased agonists and multi-agonists at different stages of development, highlighting possible challenges in their translational potential. Lastly, we discuss findings related to non-synonymous genomic variants of GLP1R and the functional importance of specific residues involved in GLP-1R function. We propose that studies of GLP-1R polymorphisms, and specifically their effect on receptor dynamics and pharmacology in response to biased agonists, could have a significant impact in delineating precision medicine approaches and development of novel therapeutics.
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Affiliation(s)
- Liliane El Eid
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Christopher A Reynolds
- Centre for Sport, Exercise and Life Sciences, Faculty of Health and Life Sciences, Coventry University, Alison Gingell Building, United Kingdom; School of Life Sciences, University of Essex, Colchester, United Kingdom
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom.
| | - Ben Jones
- Section of Endocrinology and Investigative Medicine, Imperial College London, London, United Kingdom.
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5
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Mechanisms of Beta-Cell Apoptosis in Type 2 Diabetes-Prone Situations and Potential Protection by GLP-1-Based Therapies. Int J Mol Sci 2021; 22:ijms22105303. [PMID: 34069914 PMCID: PMC8157542 DOI: 10.3390/ijms22105303] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/07/2021] [Accepted: 05/13/2021] [Indexed: 12/22/2022] Open
Abstract
Type 2 diabetes (T2D) is characterized by chronic hyperglycemia secondary to the decline of functional beta-cells and is usually accompanied by a reduced sensitivity to insulin. Whereas altered beta-cell function plays a key role in T2D onset, a decreased beta-cell mass was also reported to contribute to the pathophysiology of this metabolic disease. The decreased beta-cell mass in T2D is, at least in part, attributed to beta-cell apoptosis that is triggered by diabetogenic situations such as amyloid deposits, lipotoxicity and glucotoxicity. In this review, we discussed the molecular mechanisms involved in pancreatic beta-cell apoptosis under such diabetes-prone situations. Finally, we considered the molecular signaling pathways recruited by glucagon-like peptide-1-based therapies to potentially protect beta-cells from death under diabetogenic situations.
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6
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Methods to Study Roles of β-Arrestins in the Regulation of Pancreatic β-Cell Function. Methods Mol Biol 2019. [PMID: 30919365 DOI: 10.1007/978-1-4939-9158-7_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Novel findings reveal important functional roles for β-arrestin 1 and β-arrestin 2 in the regulation of insulin secretion, β-cell survival, and β-cell mass plasticity not only by glucose but also by G-protein-coupled receptors, such as the glucagon-like peptide-1 (GLP-1) and the pituitary adenylate cyclase-activating polypeptide (PACAP) receptors or GPR40, or tyrosine kinase receptors, such as the insulin receptor. Here, we describe experimental protocols to knock down β-arrestins by small interference RNA, to follow subcellular localization of β-arrestins in the cytosol and nucleus of the insulinoma INS-1E rat pancreatic β-cell line, and to analyze β-arrestin protein expression by Western blot using INS-1E cells and isolated mouse or human pancreatic islets. We also provide details on how to genotype β-arrestin 2 knockout (Arrb2-/-) mice and to evaluate β-arrestin-mediated roles in β-cell mass plasticity and β-cell signaling using immunocytochemistry on pancreatic sections or on primary dispersed β-cells from wild-type mice and Arrb2-/- mice.
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7
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Endothelin-converting enzyme-1 regulates glucagon-like peptide-1 receptor signalling and resensitisation. Biochem J 2019; 476:513-533. [PMID: 30626614 DOI: 10.1042/bcj20180853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 02/08/2023]
Abstract
Following nutrient ingestion, glucagon-like peptide 1 (GLP-1) is secreted from intestinal L-cells and mediates anti-diabetic effects, most notably stimulating glucose-dependent insulin release from pancreatic β-cells but also inhibiting glucagon release, promoting satiety and weight reduction and potentially enhancing or preserving β-cell mass. These effects are mediated by the GLP-1 receptor (GLP-1R), which is a therapeutic target in type 2 diabetes. Although agonism at the GLP-1R has been well studied, desensitisation and resensitisation are perhaps less well explored. An understanding of these events is important, particularly in the design and use of novel receptor ligands. Here, using either HEK293 cells expressing the recombinant human GLP-1R or the pancreatic β-cell line, INS-1E with endogenous expressesion of the GLP-1R, we demonstrate GLP-1R desensitisation and subsequent resensitisation following removal of extracellular GLP-1 7-36 amide. Resensitisation is dependent on receptor internalisation, endosomal acidification and receptor recycling. Resensitisation is also regulated by endothelin-converting enzyme-1 (ECE-1) activity, most likely through proteolysis of GLP-1 in endosomes and the facilitation of GLP-1R dephosphorylation and recycling. Inhibition of ECE-1 activity also increases GLP-1-induced activation of extracellular signal-regulated kinase and generation of cAMP, suggesting processes dependent upon the lifetime of the internalised ligand-receptor complex.
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8
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Buenaventura T, Kanda N, Douzenis PC, Jones B, Bloom SR, Chabosseau P, Corrêa IR, Bosco D, Piemonti L, Marchetti P, Johnson PR, Shapiro AMJ, Rutter GA, Tomas A. A Targeted RNAi Screen Identifies Endocytic Trafficking Factors That Control GLP-1 Receptor Signaling in Pancreatic β-Cells. Diabetes 2018; 67:385-399. [PMID: 29284659 DOI: 10.2337/db17-0639] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2017] [Accepted: 12/19/2017] [Indexed: 11/13/2022]
Abstract
The glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) is a key target for type 2 diabetes (T2D) treatment. Because endocytic trafficking of agonist-bound receptors is one of the most important routes for regulation of receptor signaling, a better understanding of this process may facilitate the development of new T2D therapeutic strategies. Here, we screened 29 proteins with known functions in G protein-coupled receptor trafficking for their role in GLP-1R potentiation of insulin secretion in pancreatic β-cells. We identify five (clathrin, dynamin1, AP2, sorting nexins [SNX] SNX27, and SNX1) that increase and four (huntingtin-interacting protein 1 [HIP1], HIP14, GASP-1, and Nedd4) that decrease insulin secretion from murine insulinoma MIN6B1 cells in response to the GLP-1 analog exendin-4. The roles of HIP1 and the endosomal SNX1 and SNX27 were further characterized in mouse and human β-cell lines and human islets. While HIP1 was required for the coupling of cell surface GLP-1R activation with clathrin-dependent endocytosis, the SNXs were found to control the balance between GLP-1R plasma membrane recycling and lysosomal degradation and, in doing so, determine the overall β-cell incretin responses. We thus identify key modulators of GLP-1R trafficking and signaling that might provide novel targets to enhance insulin secretion in T2D.
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Affiliation(s)
- Teresa Buenaventura
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K
| | - Nisha Kanda
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K
| | - Phoebe C Douzenis
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K
| | - Ben Jones
- Section of Investigative Medicine, Imperial College London, London, U.K
| | - Stephen R Bloom
- Section of Investigative Medicine, Imperial College London, London, U.K
| | - Pauline Chabosseau
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K
| | | | - Domenico Bosco
- Department of Surgery, University of Geneva, Geneva, Switzerland
| | - Lorenzo Piemonti
- Diabetes Research Institute, San Raffaele Scientific Institute, Milan, Italy
- Vita-Salute San Raffaele University, Milan, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | - Paul R Johnson
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, U.K
| | - A M James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics and Pancreatic Islet Biology and Diabetes Consortium, Imperial College London, London, U.K.
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9
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Reiter E, Ayoub MA, Pellissier LP, Landomiel F, Musnier A, Tréfier A, Gandia J, De Pascali F, Tahir S, Yvinec R, Bruneau G, Poupon A, Crépieux P. β-arrestin signalling and bias in hormone-responsive GPCRs. Mol Cell Endocrinol 2017; 449:28-41. [PMID: 28174117 DOI: 10.1016/j.mce.2017.01.052] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Revised: 01/31/2017] [Accepted: 01/31/2017] [Indexed: 12/14/2022]
Abstract
G protein-coupled receptors (GPCRs) play crucial roles in the ability of target organs to respond to hormonal cues. GPCRs' activation mechanisms have long been considered as a two-state process connecting the agonist-bound receptor to heterotrimeric G proteins. This view is now challenged as mounting evidence point to GPCRs being connected to large arrays of transduction mechanisms involving heterotrimeric G proteins as well as other players. Amongst the G protein-independent transduction mechanisms, those elicited by β-arrestins upon their recruitment to the active receptors are by far the best characterized and apply to most GPCRs. These concepts, in conjunction with remarkable advances made in the field of GPCR structural biology and biophysics, have supported the notion of ligand-selective signalling also known as pharmacological bias. Interestingly, recent reports have opened intriguing prospects to the way β-arrestins control GPCR-mediated signalling in space and time within the cells. In the present paper, we review the existing evidence linking endocrine-related GPCRs to β-arrestin recruitement, signalling, pathophysiological implications and selective activation by biased ligands and/or receptor modifications. Emerging concepts surrounding β-arrestin-mediated transduction are discussed in the light of the peculiarities of endocrine systems.
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Affiliation(s)
- Eric Reiter
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France.
| | - Mohammed Akli Ayoub
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France; LE STUDIUM(®) Loire Valley Institute for Advanced Studies, 45000, Orléans, France; Biology Department, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | | | - Flavie Landomiel
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Astrid Musnier
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Aurélie Tréfier
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Jorge Gandia
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | | | - Shifa Tahir
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Romain Yvinec
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Gilles Bruneau
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Anne Poupon
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Pascale Crépieux
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
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10
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Zhang YX, Li XF, Yuan GQ, Hu H, Song XY, Li JY, Miao XK, Zhou TX, Yang WL, Zhang XW, Mou LY, Wang R. β-Arrestin 1 has an essential role in neurokinin-1 receptor-mediated glioblastoma cell proliferation and G 2/M phase transition. J Biol Chem 2017; 292:8933-8947. [PMID: 28341744 DOI: 10.1074/jbc.m116.770420] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 03/22/2017] [Indexed: 11/06/2022] Open
Abstract
Glioblastoma is the most common malignant brain tumor and has a poor prognosis. Tachykinin receptor neurokinin-1 (NK1R) is a promising target in glioblastoma therapy because of its overexpression in human glioblastoma. NK1R agonists promote glioblastoma cell growth, whereas NK1R antagonists efficiently inhibit cell growth both in vitro and in vivo However, the molecular mechanisms involved in these effects are incompletely understood. β-Arrestins (ARRBs) serve as scaffold proteins and adapters to mediate intracellular signal transduction. Here we show that the ARRB1-mediated signaling pathway is essential for NK1-mediated glioblastoma cell proliferation. ARRB1 knockdown significantly inhibited NK1-mediated glioblastoma cell proliferation and induced G2/M phase cell cycle arrest. ARRB1 knockdown cells showed remarkable down-regulation of CDC25C/CDK1/cyclin B1 activity. We also demonstrated that ARRB1 mediated prolonged phosphorylation of ERK1/2 and Akt in glioblastoma cells induced by NK1R activation. ERK1/2 and Akt phosphorylation are involved in regulating CDC25C/CDK1/cyclin B1 activity. The lack of long-term ERK1/2 and Akt activation in ARRB1 knockdown cells was at least partly responsible for the delayed cell cycle progression and proliferation. Moreover, we found that ARRB1-mediated ERK1/2 and Akt phosphorylation regulated the transcriptional activity of both NF-κB and AP-1, which were involved in cyclin B1 expression. ARRB1 deficiency increased the sensitivity of glioblastoma cells to the treatment of NK1R antagonists. Taken together, our results suggest that ARRB1 plays an essential role in NK1R-mediated cell proliferation and G2/M transition in glioblastoma cells. Interference with ARRB1-mediated signaling via NK1R may have potential significance for therapeutic strategies targeting glioblastoma.
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Affiliation(s)
- Yi-Xin Zhang
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Xiao-Fang Li
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Guo-Qiang Yuan
- the Department of Neurosurgery, Second Affiliated Hospital of Lanzhou University, Lanzhou 730000, China
| | - Hui Hu
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Xiao-Yun Song
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Jing-Yi Li
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Xiao-Kang Miao
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Tian-Xiong Zhou
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Wen-Le Yang
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Xiao-Wei Zhang
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Ling-Yun Mou
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
| | - Rui Wang
- From the Institute of Biochemistry and Molecular Biology, School of Life Sciences and Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China and
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Cahill TJ, Thomsen ARB, Tarrasch JT, Plouffe B, Nguyen AH, Yang F, Huang LY, Kahsai AW, Bassoni DL, Gavino BJ, Lamerdin JE, Triest S, Shukla AK, Berger B, Little J, Antar A, Blanc A, Qu CX, Chen X, Kawakami K, Inoue A, Aoki J, Steyaert J, Sun JP, Bouvier M, Skiniotis G, Lefkowitz RJ. Distinct conformations of GPCR-β-arrestin complexes mediate desensitization, signaling, and endocytosis. Proc Natl Acad Sci U S A 2017; 114:2562-2567. [PMID: 28223524 PMCID: PMC5347553 DOI: 10.1073/pnas.1701529114] [Citation(s) in RCA: 245] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
β-Arrestins (βarrs) interact with G protein-coupled receptors (GPCRs) to desensitize G protein signaling, to initiate signaling on their own, and to mediate receptor endocytosis. Prior structural studies have revealed two unique conformations of GPCR-βarr complexes: the "tail" conformation, with βarr primarily coupled to the phosphorylated GPCR C-terminal tail, and the "core" conformation, where, in addition to the phosphorylated C-terminal tail, βarr is further engaged with the receptor transmembrane core. However, the relationship of these distinct conformations to the various functions of βarrs is unknown. Here, we created a mutant form of βarr lacking the "finger-loop" region, which is unable to form the core conformation but retains the ability to form the tail conformation. We find that the tail conformation preserves the ability to mediate receptor internalization and βarr signaling but not desensitization of G protein signaling. Thus, the two GPCR-βarr conformations can carry out distinct functions.
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Affiliation(s)
- Thomas J Cahill
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
| | - Alex R B Thomsen
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
| | - Jeffrey T Tarrasch
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Bianca Plouffe
- Department of Biochemistry, Institute for Research in Immunology and Cancer, University of Montreal, Montreal, QC H3C 3J7, Canada
| | - Anthony H Nguyen
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710
| | - Fan Yang
- Department of Molecular Biology and Biochemistry, Shandong University School of Medicine, Jinan, Shandong 250012, China
| | - Li-Yin Huang
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
| | - Alem W Kahsai
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
| | | | | | | | - Sarah Triest
- Structural Biology Brussels, Vrije Universiteit Brussels, B-1050 Brussels, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, B-1050 Brussels, Belgium
| | - Arun K Shukla
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
| | - Benjamin Berger
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
| | - John Little
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
| | - Albert Antar
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
| | - Adi Blanc
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
| | - Chang-Xiu Qu
- Department of Molecular Biology and Biochemistry, Shandong University School of Medicine, Jinan, Shandong 250012, China
| | - Xin Chen
- School of Pharmaceutical Engineering and Life Sciences, Changzhou University, Changzhou, Jiangsu 213164, China
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Asuka Inoue
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
- Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), Kawaguchi, Saitama 332-0012, Japan
| | - Junken Aoki
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
- Core Research for Evolutionary Science and Technology (AMED-CREST), Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussels, B-1050 Brussels, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, B-1050 Brussels, Belgium
| | - Jin-Peng Sun
- Department of Molecular Biology and Biochemistry, Shandong University School of Medicine, Jinan, Shandong 250012, China
| | - Michel Bouvier
- Department of Biochemistry, Institute for Research in Immunology and Cancer, University of Montreal, Montreal, QC H3C 3J7, Canada
| | - Georgios Skiniotis
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Robert J Lefkowitz
- Department of Medicine, Duke University Medical Center, Durham, NC 27710;
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710
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12
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Hager MV, Johnson LM, Wootten D, Sexton PM, Gellman SH. β-Arrestin-Biased Agonists of the GLP-1 Receptor from β-Amino Acid Residue Incorporation into GLP-1 Analogues. J Am Chem Soc 2016; 138:14970-14979. [PMID: 27813409 PMCID: PMC5207657 DOI: 10.1021/jacs.6b08323] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Activation of a G protein-coupled receptor (GPCR) causes recruitment of multiple intracellular proteins, each of which can activate distinct signaling pathways. This complexity has engendered interest in agonists that preferentially stimulate subsets among the natural signaling pathways ("biased agonists"). We have examined analogues of glucagon-like peptide-1 (GLP-1) containing β-amino acid residues in place of native α residues at selected sites and found that some analogues differ from GLP-1 in terms of their relative abilities to promote G protein activation (as monitored via cAMP production) versus β-arrestin recruitment (as monitored via BRET assays). The α → β replacements generally cause modest declines in stimulation of cAMP production and β-arrestin recruitment, but for some replacement sets cAMP production is more strongly affected than is β-arrestin recruitment. The central portion of GLP-1 appears to be critical for achieving bias toward β-arrestin recruitment. These results suggest that backbone modification via α → β residue replacement may be a versatile source of agonists with biased GLP-1R activation profiles.
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Affiliation(s)
- Marlies V Hager
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706 United States
| | - Lisa M Johnson
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706 United States
| | - Denise Wootten
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University , Parkville, VIC 3052, Australia
| | - Patrick M Sexton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University , Parkville, VIC 3052, Australia
| | - Samuel H Gellman
- Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53706 United States
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Abstract
The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are important regulators of insulin and glucagon secretion as well as lipid metabolism and appetite. These biological functions make their respective receptors (GIPR and GLP-1R) attractive targets in the treatment of both type 2 diabetes mellitus (T2DM) and obesity. The use of these native peptides in the treatment of these conditions is limited by their short half-lives. However, long-acting GLP-1R agonists and inhibitors of the enzyme that rapidly inactivates GIP and GLP-1 (dipeptidyl peptidase IV) are in clinical use. Although there is a loss of response to both hormones in T2DM, this effect appears to be more pronounced for GIP. This has made targeting GIPR less successful than GLP-1R. Furthermore, results demonstrating that GIPR knockout mice were resistant to diet-induced obesity suggested that GIPR antagonists may prove to be useful therapeutics. More recently, molecules that activate both receptors have shown promise in terms of glycemic and body weight control. This review focused on recent advances in the understanding of the signaling mechanisms and regulation of these two clinically important receptors.
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Affiliation(s)
- Suleiman Al-Sabah
- *Dr. Suleiman Al-Sabah, Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110 (Kuwait), E-Mail
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14
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Phospho-selective mechanisms of arrestin conformations and functions revealed by unnatural amino acid incorporation and (19)F-NMR. Nat Commun 2015; 6:8202. [PMID: 26347956 PMCID: PMC4569848 DOI: 10.1038/ncomms9202] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/28/2015] [Indexed: 12/25/2022] Open
Abstract
Specific arrestin conformations are coupled to distinct downstream effectors, which underlie the functions of many G-protein-coupled receptors (GPCRs). Here, using unnatural amino acid incorporation and fluorine-19 nuclear magnetic resonance (19F-NMR) spectroscopy, we demonstrate that distinct receptor phospho-barcodes are translated to specific β-arrestin-1 conformations and direct selective signalling. With its phosphate-binding concave surface, β-arrestin-1 ‘reads' the message in the receptor phospho-C-tails and distinct phospho-interaction patterns are revealed by 19F-NMR. Whereas all functional phosphopeptides interact with a common phosphate binding site and induce the movements of finger and middle loops, different phospho-interaction patterns induce distinct structural states of β-arrestin-1 that are coupled to distinct arrestin functions. Only clathrin recognizes and stabilizes GRK2-specific β-arrestin-1 conformations. The identified receptor-phospho-selective mechanism for arrestin conformation and the spacing of the multiple phosphate-binding sites in the arrestin enable arrestin to recognize plethora phosphorylation states of numerous GPCRs, contributing to the functional diversity of receptors. G-protein-coupled receptors (GPCRs) signal via G proteins or arrestin-mediated pathways; the plasticity of arrestin proteins is thought to underlie their function. Here, the authors use NMR to examine how β-arrestin-1 recognizes different GPCR phospho-barcodes, and how this triggers structural rearrangements to fulfill selective functions.
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15
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Dai FF, Bhattacharjee A, Liu Y, Batchuluun B, Zhang M, Wang XS, Huang X, Luu L, Zhu D, Gaisano H, Wheeler MB. A Novel GLP1 Receptor Interacting Protein ATP6ap2 Regulates Insulin Secretion in Pancreatic Beta Cells. J Biol Chem 2015; 290:25045-61. [PMID: 26272612 DOI: 10.1074/jbc.m115.648592] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 11/06/2022] Open
Abstract
GLP1 activates its receptor, GLP1R, to enhance insulin secretion. The activation and transduction of GLP1R requires complex interactions with a host of accessory proteins, most of which remain largely unknown. In this study, we used membrane-based split ubiquitin yeast two-hybrid assays to identify novel GLP1R interactors in both mouse and human islets. Among these, ATP6ap2 (ATPase H(+)-transporting lysosomal accessory protein 2) was identified in both mouse and human islet screens. ATP6ap2 was shown to be abundant in islets including both alpha and beta cells. When GLP1R and ATP6ap2 were co-expressed in beta cells, GLP1R was shown to directly interact with ATP6ap2, as assessed by co-immunoprecipitation. In INS-1 cells, overexpression of ATP6ap2 did not affect insulin secretion; however, siRNA knockdown decreased both glucose-stimulated and GLP1-induced insulin secretion. Decreases in GLP1-induced insulin secretion were accompanied by attenuated GLP1 stimulated cAMP accumulation. Because ATP6ap2 is a subunit required for V-ATPase assembly of insulin granules, it has been reported to be involved in granule acidification. In accordance with this, we observed impaired insulin granule acidification upon ATP6ap2 knockdown but paradoxically increased proinsulin secretion. Importantly, as a GLP1R interactor, ATP6ap2 was required for GLP1-induced Ca(2+) influx, in part explaining decreased insulin secretion in ATP6ap2 knockdown cells. Taken together, our findings identify a group of proteins that interact with the GLP1R. We further show that one interactor, ATP6ap2, plays a novel dual role in beta cells, modulating both GLP1R signaling and insulin processing to affect insulin secretion.
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Affiliation(s)
- Feihan F Dai
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Alpana Bhattacharjee
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Ying Liu
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Battsetseg Batchuluun
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Ming Zhang
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Xinye Serena Wang
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Xinyi Huang
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Lemieux Luu
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Dan Zhu
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Herbert Gaisano
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Michael B Wheeler
- From the Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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16
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Stewart AF, Hussain MA, García-Ocaña A, Vasavada RC, Bhushan A, Bernal-Mizrachi E, Kulkarni RN. Human β-cell proliferation and intracellular signaling: part 3. Diabetes 2015; 64:1872-85. [PMID: 25999530 PMCID: PMC4439562 DOI: 10.2337/db14-1843] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This is the third in a series of Perspectives on intracellular signaling pathways coupled to proliferation in pancreatic β-cells. We contrast the large knowledge base in rodent β-cells with the more limited human database. With the increasing incidence of type 1 diabetes and the recognition that type 2 diabetes is also due in part to a deficiency of functioning β-cells, there is great urgency to identify therapeutic approaches to expand human β-cell numbers. Therapeutic approaches might include stem cell differentiation, transdifferentiation, or expansion of cadaver islets or residual endogenous β-cells. In these Perspectives, we focus on β-cell proliferation. Past Perspectives reviewed fundamental cell cycle regulation and its upstream regulation by insulin/IGF signaling via phosphatidylinositol-3 kinase/mammalian target of rapamycin signaling, glucose, glycogen synthase kinase-3 and liver kinase B1, protein kinase Cζ, calcium-calcineurin-nuclear factor of activated T cells, epidermal growth factor/platelet-derived growth factor family members, Wnt/β-catenin, leptin, and estrogen and progesterone. Here, we emphasize Janus kinase/signal transducers and activators of transcription, Ras/Raf/extracellular signal-related kinase, cadherins and integrins, G-protein-coupled receptors, and transforming growth factor β signaling. We hope these three Perspectives will serve to introduce these pathways to new researchers and will encourage additional investigators to focus on understanding how to harness key intracellular signaling pathways for therapeutic human β-cell regeneration for diabetes.
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Affiliation(s)
- Andrew F Stewart
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Mehboob A Hussain
- Departments of Medicine and Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD
| | - Adolfo García-Ocaña
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Rupangi C Vasavada
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Anil Bhushan
- Diabetes Center, University of California, San Francisco, San Francisco, CA
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, and VA Ann Arbor Healthcare System, Ann Arbor, MI
| | - Rohit N Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Medical School, Boston, MA
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17
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Maffei A, Segal AM, Alvarez-Perez JC, Garcia-Ocaña A, Harris PE. Anti-incretin, Anti-proliferative Action of Dopamine on β-Cells. Mol Endocrinol 2015; 29:542-57. [PMID: 25751312 DOI: 10.1210/me.2014-1273] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Human islet β-cells exploit an autocrine dopamine (DA)-mediated inhibitory circuit to regulate insulin secretion. β-Cells also express the DA active transporter and the large neutral amino acid transporter heterodimer enabling them to import circulating DA or its biosynthetic precursor, L-3,4-dihydroxyphenylalanine (L-DOPA). The capacity to import DA or L-DOPA from the extracellular space possibly indicates that DA may be an endocrine signal as well. In humans, a mixed meal stimulus is accompanied by contemporary serum excursions of incretins, DA and L-DOPA, suggesting that DA may act as an anti-incretin as postulated by the foregut hypothesis proposed to explain the early effects of bariatric surgery on type 2 diabetes. In this report, we take a translational step backwards and characterize the kinetics of plasma DA and incretin production after a mixed meal challenge in a rat model and study the integration of incretin and DA signaling at the biochemical level in a rodent β-cell line and islets. We found that there are similar excursions of incretins and DA in rats, as those reported in humans, after a mixed meal challenge and that DA counters incretin enhanced glucose-stimulated insulin secretion and intracellular signaling at multiple points from dampening calcium fluxes to inhibiting proliferation as well as apoptosis. Our data suggest that DA is an important regulator of insulin secretion and may represent 1 axis of a gut level circuit of glucose and β-cell mass homeostasis.
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Affiliation(s)
- Antonella Maffei
- Division of Endocrinology (A.M., P.H.), Department of Medicine, and Department of Surgery (A.M.S.), Columbia University Medical College, New York, New York 10032; Institute of Genetics and Biophysics (A.M.), Adriano Buzzati-Traverso, Consiglio Nazionale delle Ricerche, 80131 Naples, Italy; and Division of Endocrinology, Diabetes and Bone Diseases (J.C.A.-P., A.G.-O.), Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai and The Mindich Child Health and Development Institute, New York, New York 10029
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18
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Modi H, Cornu M, Thorens B. Glutamine stimulates biosynthesis and secretion of insulin-like growth factor 2 (IGF2), an autocrine regulator of beta cell mass and function. J Biol Chem 2014; 289:31972-31982. [PMID: 25271169 DOI: 10.1074/jbc.m114.587733] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
IGF2 is an autocrine ligand for the beta cell IGF1R receptor and GLP-1 increases the activity of this autocrine loop by enhancing IGF1R expression, a mechanism that mediates the trophic effects of GLP-1 on beta cell mass and function. Here, we investigated the regulation of IGF2 biosynthesis and secretion. We showed that glutamine rapidly and strongly induced IGF2 mRNA translation using reporter constructs transduced in MIN6 cells and primary islet cells. This was followed by rapid secretion of IGF2 via the regulated pathway, as revealed by the presence of mature IGF2 in insulin granule fractions and by inhibition of secretion by nimodipine and diazoxide. When maximally stimulated by glutamine, the amount of secreted IGF2 rapidly exceeded its initial intracellular pool and tolbutamide, and high K(+) increased IGF2 secretion only marginally. This indicates that the intracellular pool of IGF2 is small and that sustained secretion requires de novo synthesis. The stimulatory effect of glutamine necessitates its metabolism but not mTOR activation. Finally, exposure of insulinomas or beta cells to glutamine induced Akt phosphorylation, an effect that was dependent on IGF2 secretion, and reduced cytokine-induced apoptosis. Thus, glutamine controls the activity of the beta cell IGF2/IGF1R autocrine loop by increasing the biosynthesis and secretion of IGF2. This autocrine loop can thus integrate changes in feeding and metabolic state to adapt beta cell mass and function.
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Affiliation(s)
- Honey Modi
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Marion Cornu
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland.
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Al-Sabah S, Al-Fulaij M, Shaaban G, Ahmed HA, Mann RJ, Donnelly D, Bünemann M, Krasel C. The GIP receptor displays higher basal activity than the GLP-1 receptor but does not recruit GRK2 or arrestin3 effectively. PLoS One 2014; 9:e106890. [PMID: 25191754 PMCID: PMC4156404 DOI: 10.1371/journal.pone.0106890] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 08/03/2014] [Indexed: 12/25/2022] Open
Abstract
Background and Objectives Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are important regulators of insulin secretion, and their functional loss is an early characteristic of type 2 diabetes mellitus (T2DM). Pharmacological levels of GLP-1, but not GIP, can overcome this loss. GLP-1 and GIP exert their insulinotropic effects through their respective receptors expressed on pancreatic β-cells. Both the GLP-1 receptor (GLP-1R) and the GIP receptor (GIPR) are members of the secretin family of G protein-coupled receptors (GPCRs) and couple positively to adenylate cyclase. We compared the signalling properties of these two receptors to gain further insight into why GLP-1, but not GIP, remains insulinotropic in T2DM patients. Methods GLP-1R and GIPR were transiently expressed in HEK-293 cells, and basal and ligand-induced cAMP production were investigated using a cAMP-responsive luciferase reporter gene assay. Arrestin3 (Arr3) recruitment to the two receptors was investigated using enzyme fragment complementation, confocal microscopy and fluorescence resonance energy transfer (FRET). Results GIPR displayed significantly higher (P<0.05) ligand-independent activity than GLP-1R. Arr3 displayed a robust translocation to agonist-stimulated GLP-1R but not to GIPR. These observations were confirmed in FRET experiments, in which GLP-1 stimulated the recruitment of both GPCR kinase 2 (GRK2) and Arr3 to GLP-1R. These interactions were not reversed upon agonist washout. In contrast, GIP did not stimulate recruitment of either GRK2 or Arr3 to its receptor. Interestingly, arrestin remained at the plasma membrane even after prolonged (30 min) stimulation with GLP-1. Although the GLP-1R/arrestin interaction could not be reversed by agonist washout, GLP-1R and arrestin did not co-internalise, suggesting that GLP-1R is a class A receptor with regard to arrestin binding. Conclusions GIPR displays higher basal activity than GLP-1R but does not effectively recruit GRK2 or Arr3.
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Affiliation(s)
- Suleiman Al-Sabah
- Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait
- * E-mail:
| | - Munya Al-Fulaij
- Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Ghina Shaaban
- Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Hanadi A. Ahmed
- Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Rosalind J. Mann
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Dan Donnelly
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Moritz Bünemann
- School of Pharmacy, Institute for Pharmacology and Toxicology, The Philipps University of Marburg, Marburg, Germany
| | - Cornelius Krasel
- School of Pharmacy, Institute for Pharmacology and Toxicology, The Philipps University of Marburg, Marburg, Germany
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20
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Xie J, El Sayed NM, Qi C, Zhao X, Moore CE, Herbert TP. Exendin-4 stimulates islet cell replication via the IGF1 receptor activation of mTORC1/S6K1. J Mol Endocrinol 2014; 53:105-15. [PMID: 24994913 DOI: 10.1530/jme-13-0200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Glucagon-like peptide 1 receptor (GLP1R) agonists, such as exendin-4, potentiate glucose-stimulated insulin secretion and are currently used in the management of type 2 diabetes. Interestingly, GLP1R agonists also have the ability to augment β-cell mass. In this report, we provide evidence that in the presence of glucose, exendin-4 stimulates rodent islet cell DNA replication via the activation of ribosomal protein S6 kinase 1 (S6K1) and that this is mediated by the protein kinase B (PKB)-dependent activation of mTOR complex 1 (mTORC1). We show that activation of this pathway is caused by the autocrine or paracrine activation of the IGF1 receptor (IGF1R), as siRNA-mediated knockdown of the IGF1R effectively blocked exendin-4-stimulated PKB and mTORC1 activation. In contrast, pharmacological inactivation of the epidermal growth factor receptor has no discernible effect on exendin-4-stimulated PKB or mTORC1 activation. Therefore, we conclude that GLP1R agonists stimulate β-cell proliferation via the PKB-dependent stimulation of mTORC1/S6K1 whose activation is mediated through the autocrine/paracrine activation of the IGF1R. This work provides a better understanding of the molecular basis of GLP1 agonist-induced β-cell proliferation which could potentially be exploited in the identification of novel drug targets that increase β-cell mass.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Norhan M El Sayed
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Cheng Qi
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Xuechan Zhao
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Claire E Moore
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Terence P Herbert
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
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Vallois D, Niederhäuser G, Ibberson M, Nagaray V, Marselli L, Marchetti P, Chatton JY, Thorens B. Gluco-incretins regulate beta-cell glucose competence by epigenetic silencing of Fxyd3 expression. PLoS One 2014; 9:e103277. [PMID: 25058609 PMCID: PMC4110016 DOI: 10.1371/journal.pone.0103277] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 06/28/2014] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND/AIMS Gluco-incretin hormones increase the glucose competence of pancreatic beta-cells by incompletely characterized mechanisms. METHODS We searched for genes that were differentially expressed in islets from control and Glp1r-/-; Gipr-/- (dKO) mice, which show reduced glucose competence. Overexpression and knockdown studies; insulin secretion analysis; analysis of gene expression in islets from control and diabetic mice and humans as well as gene methylation and transcriptional analysis were performed. RESULTS Fxyd3 was the most up-regulated gene in glucose incompetent islets from dKO mice. When overexpressed in beta-cells Fxyd3 reduced glucose-induced insulin secretion by acting downstream of plasma membrane depolarization and Ca++ influx. Fxyd3 expression was not acutely regulated by cAMP raising agents in either control or dKO adult islets. Instead, expression of Fxyd3 was controlled by methylation of CpGs present in its proximal promoter region. Increased promoter methylation reduced Fxyd3 transcription as assessed by lower abundance of H3K4me3 at the transcriptional start site and in transcription reporter assays. This epigenetic imprinting was initiated perinatally and fully established in adult islets. Glucose incompetent islets from diabetic mice and humans showed increased expression of Fxyd3 and reduced promoter methylation. CONCLUSIONS/INTERPRETATION Because gluco-incretin secretion depends on feeding the epigenetic regulation of Fxyd3 expression may link nutrition in early life to establishment of adult beta-cell glucose competence; this epigenetic control is, however, lost in diabetes possibly as a result of gluco-incretin resistance and/or de-differentiation of beta-cells that are associated with the development of type 2 diabetes.
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Affiliation(s)
- David Vallois
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Guy Niederhäuser
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Mark Ibberson
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
- Vital-IT group, SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | | | - Lorella Marselli
- Department of Endocrinology and Metabolism, Ospedale di Cisanello, Pisa, Italy
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, Ospedale di Cisanello, Pisa, Italy
| | - Jean-Yves Chatton
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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Ravier MA, Leduc M, Richard J, Linck N, Varrault A, Pirot N, Roussel MM, Bockaert J, Dalle S, Bertrand G. β-Arrestin2 plays a key role in the modulation of the pancreatic beta cell mass in mice. Diabetologia 2014; 57:532-41. [PMID: 24317793 DOI: 10.1007/s00125-013-3130-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 11/13/2013] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Beta cell failure due to progressive secretory dysfunction and limited expansion of beta cell mass is a key feature of type 2 diabetes. Beta cell function and mass are controlled by glucose and hormones/neurotransmitters that activate G protein-coupled receptors or receptor tyrosine kinases. We have investigated the role of β-arrestin (ARRB)2, a scaffold protein known to modulate such receptor signalling, in the modulation of beta cell function and mass, with a specific interest in glucagon-like peptide-1 (GLP-1), muscarinic and insulin receptors. METHODS β-arrestin2-knockout mice and their wild-type littermates were fed a normal or a high-fat diet (HFD). Glucose tolerance, insulin sensitivity and insulin secretion were assessed in vivo. Beta cell mass was evaluated in pancreatic sections. Free cytosolic [Ca(2+)] and insulin secretion were determined using perifused islets. The insulin signalling pathway was evaluated by western blotting. RESULTS Arrb2-knockout mice exhibited impaired glucose tolerance and insulin secretion in vivo, but normal insulin sensitivity compared with wild type. Surprisingly, the absence of ARRB2 did not affect glucose-stimulated insulin secretion or GLP-1- and acetylcholine-mediated amplifications from perifused islets, but it decreased the islet insulin content and beta cell mass. Additionally, there was no compensatory beta cell mass expansion through proliferation in response to the HFD. Furthermore, Arrb2 deletion altered the islet insulin signalling pathway. CONCLUSIONS/INTERPRETATION ARRB2 is unlikely to be involved in the regulation of insulin secretion, but it is required for beta cell mass plasticity. Additionally, we provide new insights into the mechanisms involved in insulin signalling in beta cells.
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Affiliation(s)
- Magalie A Ravier
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, 141 Rue de la Cardonille, 34094, Montpellier, France
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23
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Nadkarni P, Chepurny OG, Holz GG. Regulation of glucose homeostasis by GLP-1. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014. [PMID: 24373234 DOI: 10.1016/b978-0-12-800101-1.00002-8.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/01/2022]
Abstract
Glucagon-like peptide-1(7-36)amide (GLP-1) is a secreted peptide that acts as a key determinant of blood glucose homeostasis by virtue of its abilities to slow gastric emptying, to enhance pancreatic insulin secretion, and to suppress pancreatic glucagon secretion. GLP-1 is secreted from L cells of the gastrointestinal mucosa in response to a meal, and the blood glucose-lowering action of GLP-1 is terminated due to its enzymatic degradation by dipeptidyl-peptidase-IV (DPP-IV). Released GLP-1 activates enteric and autonomic reflexes while also circulating as an incretin hormone to control endocrine pancreas function. The GLP-1 receptor (GLP-1R) is a G protein-coupled receptor that is activated directly or indirectly by blood glucose-lowering agents currently in use for the treatment of type 2 diabetes mellitus (T2DM). These therapeutic agents include GLP-1R agonists (exenatide, liraglutide, lixisenatide, albiglutide, dulaglutide, and langlenatide) and DPP-IV inhibitors (sitagliptin, vildagliptin, saxagliptin, linagliptin, and alogliptin). Investigational agents for use in the treatment of T2DM include GPR119 and GPR40 receptor agonists that stimulate the release of GLP-1 from L cells. Summarized here is the role of GLP-1 to control blood glucose homeostasis, with special emphasis on the advantages and limitations of GLP-1-based therapeutics.
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Affiliation(s)
- Prashant Nadkarni
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Joslin Diabetes Center, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - Oleg G Chepurny
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - George G Holz
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Department of Pharmacology, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA.
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Abstract
The four members of the mammalian arrestin family, two visual and two nonvisual, share the property of stimulus-dependent docking to G protein-coupled receptors. This conformational selectivity permits them to function in receptor desensitization, as arrestin binding sterically inhibits G protein coupling. The two nonvisual arrestins further act as adapter proteins, linking receptors to the clathrin-dependent endocytic machinery and regulating receptor sequestration, intracellular trafficking, recycling, and degradation. Arrestins also function as ligand-regulated scaffolds, recruiting catalytically active proteins into receptor-based multiprotein "signalsome" complexes. Arrestin binding thus marks the transition from a transient G protein-coupled state on the plasma membrane to a persistent arrestin-coupled state that continues to signal as the receptor internalizes. Two of the earliest discovered and most studied arrestin-dependent signaling pathways involve regulation of Src family nonreceptor tyrosine kinases and the ERK1/2 mitogen-activated kinase cascade. In each case, arrestin scaffolding imposes constraints on kinase activity that dictate signal duration and substrate specificity. Evidence suggests that arrestin-bound ERK1/2 and Src not only play regulatory roles in receptor desensitization and trafficking but also mediate longer term effects on cell growth, migration, proliferation, and survival.
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Affiliation(s)
- Erik G Strungs
- Department of Medicine, Medical University of South Carolina, Charleston, SC, 29425, USA
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25
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Nadkarni P, Chepurny OG, Holz GG. Regulation of glucose homeostasis by GLP-1. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:23-65. [PMID: 24373234 DOI: 10.1016/b978-0-12-800101-1.00002-8] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Glucagon-like peptide-1(7-36)amide (GLP-1) is a secreted peptide that acts as a key determinant of blood glucose homeostasis by virtue of its abilities to slow gastric emptying, to enhance pancreatic insulin secretion, and to suppress pancreatic glucagon secretion. GLP-1 is secreted from L cells of the gastrointestinal mucosa in response to a meal, and the blood glucose-lowering action of GLP-1 is terminated due to its enzymatic degradation by dipeptidyl-peptidase-IV (DPP-IV). Released GLP-1 activates enteric and autonomic reflexes while also circulating as an incretin hormone to control endocrine pancreas function. The GLP-1 receptor (GLP-1R) is a G protein-coupled receptor that is activated directly or indirectly by blood glucose-lowering agents currently in use for the treatment of type 2 diabetes mellitus (T2DM). These therapeutic agents include GLP-1R agonists (exenatide, liraglutide, lixisenatide, albiglutide, dulaglutide, and langlenatide) and DPP-IV inhibitors (sitagliptin, vildagliptin, saxagliptin, linagliptin, and alogliptin). Investigational agents for use in the treatment of T2DM include GPR119 and GPR40 receptor agonists that stimulate the release of GLP-1 from L cells. Summarized here is the role of GLP-1 to control blood glucose homeostasis, with special emphasis on the advantages and limitations of GLP-1-based therapeutics.
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Affiliation(s)
- Prashant Nadkarni
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Joslin Diabetes Center, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - Oleg G Chepurny
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - George G Holz
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Department of Pharmacology, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA.
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Abstract
Oxyntomodulin (OXM) is a peptide secreted from the L cells of the gut following nutrient ingestion. OXM is a dual agonist of the glucagon-like peptide-1 receptor (GLP1R) and the glucagon receptor (GCGR) combining the effects of GLP1 and glucagon to act as a potentially more effective treatment for obesity than GLP1R agonists. Injections of OXM in humans cause a significant reduction in weight and appetite, as well as an increase in energy expenditure. Activation of GCGR is classically associated with an elevation in glucose levels, which would be deleterious in patients with T2DM, but the antidiabetic properties of GLP1R agonism would be expected to counteract this effect. Indeed, OXM administration improved glucose tolerance in diet-induced obese mice. Thus, dual agonists of the GCGR and GLP1R represent a new therapeutic approach for diabetes and obesity with the potential for enhanced weight loss and improvement in glycemic control beyond those of GLP1R agonists.
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Affiliation(s)
- Alessandro Pocai
- Diabetes and Endocrinology, Merck Research Laboratories, Merck Sharp and Dohme Corp., Rahway, New Jersey 07065, USA.
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Clardy-James S, Chepurny OG, Leech CA, Holz GG, Doyle RP. Synthesis, characterization and pharmacodynamics of vitamin-B(12)-conjugated glucagon-like peptide-1. ChemMedChem 2012. [PMID: 23203941 DOI: 10.1002/cmdc.201200461] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Clearing the way: Glucagon-like peptide-1 (GLP-1) receptor agonists are proving a potent weapon in the treatment of type II diabetes. A new vitamin B(12)-GLP-1 conjugate is investigated and shown to have insulinotropic properties similar to the unmodified peptide. These results are critical to the exploitation of the vitamin B(12) oral uptake pathway for peptide delivery.
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Affiliation(s)
- Susan Clardy-James
- Department of Chemistry, Syracuse University, 111 College Place Syracuse, NY 13244, USA
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