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Dallatana A, Cremonesi L, Trombetta M, Fracasso G, Nocini R, Giacomello L, Innamorati G. G Protein-Coupled Receptors and the Rise of Type 2 Diabetes in Children. Biomedicines 2023; 11:1576. [PMID: 37371671 DOI: 10.3390/biomedicines11061576] [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: 05/11/2023] [Revised: 05/26/2023] [Accepted: 05/27/2023] [Indexed: 06/29/2023] Open
Abstract
The human genome counts hundreds of GPCRs specialized to sense thousands of different extracellular cues, including light, odorants and nutrients in addition to hormones. Primordial GPCRs were likely glucose transporters that became sensors to monitor the abundance of nutrients and direct the cell to switch from aerobic metabolism to fermentation. Human β cells express multiple GPCRs that contribute to regulate glucose homeostasis, cooperating with many others expressed by a variety of cell types and tissues. These GPCRs are intensely studied as pharmacological targets to treat type 2 diabetes in adults. The dramatic rise of type 2 diabetes incidence in pediatric age is likely correlated to the rapidly evolving lifestyle of children and adolescents of the new century. Current pharmacological treatments are based on therapies designed for adults, while youth and puberty are characterized by a different hormonal balance related to glucose metabolism. This review focuses on GPCRs functional traits that are relevant for β cells function, with an emphasis on aspects that could help to differentiate new treatments specifically addressed to young type 2 diabetes patients.
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Affiliation(s)
- Alessia Dallatana
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37134 Verona, Italy
| | - Linda Cremonesi
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37134 Verona, Italy
| | - Maddalena Trombetta
- Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Verona, 37124 Verona, Italy
| | - Giulio Fracasso
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Riccardo Nocini
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37134 Verona, Italy
| | - Luca Giacomello
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37134 Verona, Italy
| | - Giulio Innamorati
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37134 Verona, Italy
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Bous J, Fouillen A, Orcel H, Trapani S, Cong X, Fontanel S, Saint-Paul J, Lai-Kee-Him J, Urbach S, Sibille N, Sounier R, Granier S, Mouillac B, Bron P. Structure of the vasopressin hormone-V2 receptor-β-arrestin1 ternary complex. SCIENCE ADVANCES 2022; 8:eabo7761. [PMID: 36054364 PMCID: PMC10866553 DOI: 10.1126/sciadv.abo7761] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Arrestins interact with G protein-coupled receptors (GPCRs) to stop G protein activation and to initiate key signaling pathways. Recent structural studies shed light on the molecular mechanisms involved in GPCR-arrestin coupling, but whether this process is conserved among GPCRs is poorly understood. Here, we report the cryo-electron microscopy active structure of the wild-type arginine-vasopressin V2 receptor (V2R) in complex with β-arrestin1. It reveals an atypical position of β-arrestin1 compared to previously described GPCR-arrestin assemblies, associated with an original V2R/β-arrestin1 interface involving all receptor intracellular loops. Phosphorylated sites of the V2R carboxyl terminus are clearly identified and interact extensively with the β-arrestin1 N-lobe, in agreement with structural data obtained with chimeric or synthetic systems. Overall, these findings highlight a notable structural variability among GPCR-arrestin signaling complexes.
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Affiliation(s)
- Julien Bous
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Aurélien Fouillen
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Hélène Orcel
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Stefano Trapani
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Xiaojing Cong
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Simon Fontanel
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Julie Saint-Paul
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Joséphine Lai-Kee-Him
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Serge Urbach
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Nathalie Sibille
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Rémy Sounier
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Sébastien Granier
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Bernard Mouillac
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, 34094 Montpellier Cedex 5, France
| | - Patrick Bron
- CBS (Centre de Biologie Structurale), Université de Montpellier, CNRS, INSERM, Montpellier, France
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3
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Yeung ML, Teng JLL, Jia L, Zhang C, Huang C, Cai JP, Zhou R, Chan KH, Zhao H, Zhu L, Siu KL, Fung SY, Yung S, Chan TM, To KKW, Chan JFW, Cai Z, Lau SKP, Chen Z, Jin DY, Woo PCY, Yuen KY. Soluble ACE2-mediated cell entry of SARS-CoV-2 via interaction with proteins related to the renin-angiotensin system. Cell 2021; 184:2212-2228.e12. [PMID: 33713620 PMCID: PMC7923941 DOI: 10.1016/j.cell.2021.02.053] [Citation(s) in RCA: 192] [Impact Index Per Article: 64.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/04/2021] [Accepted: 02/25/2021] [Indexed: 01/08/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause acute respiratory disease and multiorgan failure. Finding human host factors that are essential for SARS-CoV-2 infection could facilitate the formulation of treatment strategies. Using a human kidney cell line-HK-2-that is highly susceptible to SARS-CoV-2, we performed a genome-wide RNAi screen and identified virus dependency factors (VDFs), which play regulatory roles in biological pathways linked to clinical manifestations of SARS-CoV-2 infection. We found a role for a secretory form of SARS-CoV-2 receptor, soluble angiotensin converting enzyme 2 (sACE2), in SARS-CoV-2 infection. Further investigation revealed that SARS-CoV-2 exploits receptor-mediated endocytosis through interaction between its spike with sACE2 or sACE2-vasopressin via AT1 or AVPR1B, respectively. Our identification of VDFs and the regulatory effect of sACE2 on SARS-CoV-2 infection shed insight into pathogenesis and cell entry mechanisms of SARS-CoV-2 as well as potential treatment strategies for COVID-19.
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Affiliation(s)
- Man Lung Yeung
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
| | - Jade Lee Lee Teng
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Lilong Jia
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Chaoyu Zhang
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Chengxi Huang
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Jian-Piao Cai
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Runhong Zhou
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; AIDS Institute, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Kwok-Hung Chan
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Hanjun Zhao
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Lin Zhu
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong Special Administrative Region, China
| | - Kam-Leung Siu
- Department of Biochemistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Sin-Yee Fung
- Department of Biochemistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Susan Yung
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Tak Mao Chan
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Kelvin Kai-Wang To
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Jasper Fuk-Woo Chan
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Zongwei Cai
- State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong Special Administrative Region, China
| | - Susanna Kar Pui Lau
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Zhiwei Chen
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; AIDS Institute, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Dong-Yan Jin
- Department of Biochemistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Patrick Chiu Yat Woo
- State Key Laboratory of Emerging Infectious Diseases, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
| | - Kwok-Yung Yuen
- Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong Province, China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China; Carol Yu Centre for Infection, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
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Le TP, Chung S. Regulation of apical constriction via microtubule- and Rab11-dependent apical transport during tissue invagination. Mol Biol Cell 2021; 32:1033-1047. [PMID: 33788621 PMCID: PMC8101490 DOI: 10.1091/mbc.e21-01-0021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The formation of an epithelial tube is a fundamental process for organogenesis. During Drosophila embryonic salivary gland (SG) invagination, Folded gastrulation (Fog)-dependent Rho-associated kinase (Rok) promotes contractile apical myosin formation to drive apical constriction. Microtubules (MTs) are also crucial for this process and are required for forming and maintaining apicomedial myosin. However, the underlying mechanism that coordinates actomyosin and MT networks still remains elusive. Here, we show that MT-dependent intracellular trafficking regulates apical constriction during SG invagination. Key components involved in protein trafficking, such as Rab11 and Nuclear fallout (Nuf), are apically enriched near the SG invagination pit in a MT-dependent manner. Disruption of the MT networks or knockdown of Rab11 impairs apicomedial myosin formation and apical constriction. We show that MTs and Rab11 are required for apical enrichment of the Fog ligand and the continuous distribution of the apical determinant protein Crumbs (Crb) and the key adherens junction protein E-Cadherin (E-Cad) along junctions. Targeted knockdown of crb or E-Cad in the SG disrupts apical myosin networks and results in apical constriction defects. Our data suggest a role of MT- and Rab11-dependent intracellular trafficking in regulating actomyosin networks and cell junctions to coordinate cell behaviors during tubular organ formation.
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Affiliation(s)
- Thao Phuong Le
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803
| | - SeYeon Chung
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803
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5
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Sparapani S, Millet-Boureima C, Oliver J, Mu K, Hadavi P, Kalostian T, Ali N, Avelar CM, Bardies M, Barrow B, Benedikt M, Biancardi G, Bindra R, Bui L, Chihab Z, Cossitt A, Costa J, Daigneault T, Dault J, Davidson I, Dias J, Dufour E, El-Khoury S, Farhangdoost N, Forget A, Fox A, Gebrael M, Gentile MC, Geraci O, Gnanapragasam A, Gomah E, Haber E, Hamel C, Iyanker T, Kalantzis C, Kamali S, Kassardjian E, Kontos HK, Le TBU, LoScerbo D, Low YF, Mac Rae D, Maurer F, Mazhar S, Nguyen A, Nguyen-Duong K, Osborne-Laroche C, Park HW, Parolin E, Paul-Cole K, Peer LS, Philippon M, Plaisir CA, Porras Marroquin J, Prasad S, Ramsarun R, Razzaq S, Rhainds S, Robin D, Scartozzi R, Singh D, Fard SS, Soroko M, Soroori Motlagh N, Stern K, Toro L, Toure MW, Tran-Huynh S, Trépanier-Chicoine S, Waddingham C, Weekes AJ, Wisniewski A, Gamberi C. The Biology of Vasopressin. Biomedicines 2021; 9:89. [PMID: 33477721 PMCID: PMC7832310 DOI: 10.3390/biomedicines9010089] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 12/29/2020] [Accepted: 01/06/2021] [Indexed: 02/07/2023] Open
Abstract
Vasopressins are evolutionarily conserved peptide hormones. Mammalian vasopressin functions systemically as an antidiuretic and regulator of blood and cardiac flow essential for adapting to terrestrial environments. Moreover, vasopressin acts centrally as a neurohormone involved in social and parental behavior and stress response. Vasopressin synthesis in several cell types, storage in intracellular vesicles, and release in response to physiological stimuli are highly regulated and mediated by three distinct G protein coupled receptors. Other receptors may bind or cross-bind vasopressin. Vasopressin is regulated spatially and temporally through transcriptional and post-transcriptional mechanisms, sex, tissue, and cell-specific receptor expression. Anomalies of vasopressin signaling have been observed in polycystic kidney disease, chronic heart failure, and neuropsychiatric conditions. Growing knowledge of the central biological roles of vasopressin has enabled pharmacological advances to treat these conditions by targeting defective systemic or central pathways utilizing specific agonists and antagonists.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Chiara Gamberi
- Biology Department, Concordia University, Montreal, QC H4B 1R6, Canada; (S.S.); (C.M.-B.); (J.O.); (K.M.); (P.H.); (T.K.); (N.A.); (C.M.A.); (M.B.); (B.B.); (M.B.); (G.B.); (R.B.); (L.B.); (Z.C.); (A.C.); (J.C.); (T.D.); (J.D.); (I.D.); (J.D.); (E.D.); (S.E.-K.); (N.F.); (A.F.); (A.F.); (M.G.); (M.C.G.); (O.G.); (A.G.); (E.G.); (E.H.); (C.H.); (T.I.); (C.K.); (S.K.); (E.K.); (H.K.K.); (T.B.U.L.); (D.L.); (Y.F.L.); (D.M.R.); (F.M.); (S.M.); (A.N.); (K.N.-D.); (C.O.-L.); (H.W.P.); (E.P.); (K.P.-C.); (L.S.P.); (M.P.); (C.-A.P.); (J.P.M.); (S.P.); (R.R.); (S.R.); (S.R.); (D.R.); (R.S.); (D.S.); (S.S.F.); (M.S.); (N.S.M.); (K.S.); (L.T.); (M.W.T.); (S.T.-H.); (S.T.-C.); (C.W.); (A.J.W.); (A.W.)
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6
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Control of Cytoskeletal Dynamics by β-Arrestin1/Myosin Vb Signaling Regulates Endosomal Sorting and Scavenging Activity of the Atypical Chemokine Receptor ACKR2. Vaccines (Basel) 2020; 8:vaccines8030542. [PMID: 32957704 PMCID: PMC7565953 DOI: 10.3390/vaccines8030542] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/11/2020] [Accepted: 09/15/2020] [Indexed: 12/14/2022] Open
Abstract
The atypical chemokine receptor ACKR2, formerly named D6, is a scavenger chemokine receptor with a non-redundant role in the control of inflammation and immunity. The scavenging activity of ACKR2 depends on its trafficking properties, which require actin cytoskeleton rearrangements downstream of a β-arrestin1-Rac1-PAK1-LIMK1-cofilin-dependent signaling pathway. We here demonstrate that in basal conditions, ACKR2 trafficking properties require intact actin and microtubules networks. The dynamic turnover of actin filaments is required to sustain ACKR2 constitutive endocytosis, while both actin and microtubule networks are involved in processes regulating ACKR2 constitutive sorting to rapid, Rab4-dependent and slow, Rab11-dependent recycling pathways, respectively. After chemokine engagement, ACKR2 requires myosin Vb activity to promote its trafficking from Rab11-positive recycling endosomes to the plasma membrane, which sustains its scavenging activity. Other than cofilin phosphorylation, induction of the β-arrestin1-dependent signaling pathway by ACKR2 agonists also leads to the rearrangement of microtubules, which is required to support the myosin Vb-dependent ACKR2 upregulation and its scavenging properties. Disruption of the actin-based cytoskeleton by the apoptosis-inducing agent staurosporine results in impaired ACKR2 internalization and chemokine degradation that is consistent with the emerging scavenging-independent activity of the receptor in apoptotic neutrophils instrumental for promoting efficient efferocytosis during the resolution of inflammation. In conclusion, we provide evidence that ACKR2 activates a β-arrestin1-dependent signaling pathway, triggering both the actin and the microtubule cytoskeletal networks, which control its trafficking and scavenger properties.
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Zenko D, Thompson D, Hislop JN. Endocytic sorting and downregulation of the M2 acetylcholine receptor is regulated by ubiquitin and the ESCRT complex. Neuropharmacology 2020; 162:107828. [PMID: 31654703 DOI: 10.1016/j.neuropharm.2019.107828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 10/16/2019] [Accepted: 10/21/2019] [Indexed: 01/14/2023]
Abstract
Cholinergic dysfunction plays a critical role in a number of disease states, and the loss of functional muscarinic acetylcholine receptors plays a key role in disease pathogenesis. Therefore, preventing receptor downregulation would maintain functional receptor number, and be predicted to alleviate symptoms. However, the molecular mechanism(s) underlying muscarinic receptor downregulation are currently unknown. Here we demonstrate that the M2 muscarinic receptor undergoes rapid lysosomal proteolysis, and this lysosomal trafficking is facilitated by ubiquitination of the receptor. Importantly, we show that this trafficking is driven specifically by ESCRT mediated involution. Critically, we provide evidence that disruption of this process leads to a re-routing of the trafficking of the M2 receptor away from the lysosome and into recycling pathway, and eventually back to the plasma membrane. This study is the first to identify the process by which the M2 muscarinic acetylcholine receptor undergoes endocytic sorting, and critically reveals a regulatory checkpoint that represents a target to pharmacologically increase the number of functional muscarinic receptors within the central nervous system.
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Affiliation(s)
- Dmitry Zenko
- Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, AB25 2ZD, UK
| | - Dawn Thompson
- Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, AB25 2ZD, UK
| | - James N Hislop
- Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, AB25 2ZD, UK.
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8
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Khegay II. Noncanonical effects of vasopressin in angiogenesis. Vavilovskii Zhurnal Genet Selektsii 2019. [DOI: 10.18699/vj19.527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022] Open
Abstract
The molecular action of vasopressin depends on the localization of hormonal receptors. The basic physiological effects of vasopressin are manifested in the blood vasculature, renal inner medulla and brain. To date, new information concerning the tissue-specific spreading of vasopressin receptors has been accumulated, and it needs to be summarized. Platelets and endotheliocytes expressing V1a and V2 receptor types, respectively, are related to less investigated targets of the hormone. Vasopressin induces the initial reversible stage of platelet activation, required for interaction with intercellular matrix proteins. Platelet adhesion on endothelium activates cellular secretion of growth factors and enzymes for intercellular matrix glucosamine metabolism. Platelet hyaluronidase HYAL2 hydrolyses high-molecular hyaluronic acid to shorter fragments. Unlike intact hyaluronic acid with a molecular weight of several megadaltons, generally showing distinctive antiangiogenic properties, intermediate fractions of hyaluronan hydrolysis in a range from 2.5 to 200 kilodaltons have a stimulating effect on angiogenesis. Intercellular contacts between platelets and endotheliocytes are stabilized due to adhesive transmembrane glycoprotein PECAM-1 interaction. Resulting PECAM-1 heterodimers acquire conformation with high affinity to integrins αvβ3. Integrin activation forms contact links between endothelium and fibrillar proteins. Activated endotheliocytes secrete von Willebrand factor and P-selectin. These proteins are accumulated in Weibel–Palade bodies. Vasopressin stimulates cAMP-dependent ACAP-regulated exocytosis of Weibel–Palade bodies. von Willebrand factor possesses adhesive properties and additionally accelerates interaction of cells with the intercellular matrix. Adhesion on fibrillar collagen and membrane glycoproteins in cooperation with effects of PECAM-1–αvβ3 integrin complexes fixes cell aggregates in the surrounding interstitium and promotes proliferating endotheliocyte migration in according to the direction of local growth factor gradients during angiogenesis. Neurohormonal regulation of platelet and endotheliocyte secretory activity functionally link proliferation and migration of endotheliocytes during angiogenesis and integrate it according to the adaptive capacity of the entire organism.
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Giesecke T, Himmerkus N, Leipziger J, Bleich M, Koshimizu TA, Fähling M, Smorodchenko A, Shpak J, Knappe C, Isermann J, Ayasse N, Kawahara K, Schmoranzer J, Gimber N, Paliege A, Bachmann S, Mutig K. Vasopressin Increases Urinary Acidification via V1a Receptors in Collecting Duct Intercalated Cells. J Am Soc Nephrol 2019; 30:946-961. [PMID: 31097611 DOI: 10.1681/asn.2018080816] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 03/11/2019] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Antagonists of the V1a vasopressin receptor (V1aR) are emerging as a strategy for slowing progression of CKD. Physiologically, V1aR signaling has been linked with acid-base homeostasis, but more detailed information is needed about renal V1aR distribution and function. METHODS We used a new anti-V1aR antibody and high-resolution microscopy to investigate Va1R distribution in rodent and human kidneys. To investigate whether V1aR activation promotes urinary H+ secretion, we used a V1aR agonist or antagonist to evaluate V1aR function in vasopressin-deficient Brattleboro rats, bladder-catheterized mice, isolated collecting ducts, and cultured inner medullary collecting duct (IMCD) cells. RESULTS Localization of V1aR in rodent and human kidneys produced a basolateral signal in type A intercalated cells (A-ICs) and a perinuclear to subapical signal in type B intercalated cells of connecting tubules and collecting ducts. Treating vasopressin-deficient Brattleboro rats with a V1aR agonist decreased urinary pH and tripled net acid excretion; we observed a similar response in C57BL/6J mice. In contrast, V1aR antagonist did not affect urinary pH in normal or acid-loaded mice. In ex vivo settings, basolateral treatment of isolated perfused medullary collecting ducts with the V1aR agonist or vasopressin increased intracellular calcium levels in ICs and decreased luminal pH, suggesting V1aR-dependent calcium release and stimulation of proton-secreting proteins. Basolateral treatment of IMCD cells with the V1aR agonist increased apical abundance of vacuolar H+-ATPase in A-ICs. CONCLUSIONS Our results show that activation of V1aR contributes to urinary acidification via H+ secretion by A-ICs, which may have clinical implications for pharmacologic targeting of V1aR.
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Affiliation(s)
- Torsten Giesecke
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; .,Berlin Institute of Health (BIH), Berlin, Germany
| | - Nina Himmerkus
- Institute of Physiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Markus Bleich
- Institute of Physiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Taka-Aki Koshimizu
- Division of Molecular Pharmacology, Department of Pharmacology, Jichi Medical University, Shimotsuke-shi, Tochigi-ken, Japan
| | - Michael Fähling
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Alina Smorodchenko
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Julia Shpak
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Carolin Knappe
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Julian Isermann
- Institute of Physiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Niklas Ayasse
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Katsumasa Kawahara
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
| | - Jan Schmoranzer
- Advanced Medical BioImaging Core Facility, Charite-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Niclas Gimber
- Advanced Medical BioImaging Core Facility, Charite-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Alexander Paliege
- Division of Nephrology, Department of Internal Medicine III, University Hospital Carl Gustav Carus at the Technische Universität Dresden, Dresden, Germany; and
| | - Sebastian Bachmann
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Kerim Mutig
- Institute of Vegetative Anatomy, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; .,Department of Pharmacology, I.M. Sechenov First Moscow State Medical University of the Ministry of Healthcare of the Russian Federation (Sechenovskiy University), Moscow, Russian Federation
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10
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Gurevich VV, Gurevich EV. The structural basis of the arrestin binding to GPCRs. Mol Cell Endocrinol 2019; 484:34-41. [PMID: 30703488 PMCID: PMC6377262 DOI: 10.1016/j.mce.2019.01.019] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/04/2019] [Accepted: 01/17/2019] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of signaling proteins targeted by more clinically used drugs than any other protein family. GPCR signaling via G proteins is quenched (desensitized) by the phosphorylation of the active receptor by specific GPCR kinases (GRKs) followed by tight binding of arrestins to active phosphorylated receptors. Thus, arrestins engage two types of receptor elements: those that contain GRK-added phosphates and those that change conformation upon activation. GRKs attach phosphates to serines and threonines in the GPCR C-terminus or any one of the cytoplasmic loops. In addition to these phosphates, arrestins engage the cavity that appears between trans-membrane helices upon receptor activation and several other non-phosphorylated elements. The residues that bind GPCRs are localized on the concave side of both arrestin domains. Arrestins undergo a global conformational change upon receptor binding (become activated). Arrestins serve as important hubs of cellular signaling, emanating from activated GPCRs and receptor-independent.
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Affiliation(s)
- Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN, 37232, USA.
| | - Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN, 37232, USA
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11
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Perkovska S, Méjean C, Ayoub MA, Li J, Hemery F, Corbani M, Laguette N, Ventura MA, Orcel H, Durroux T, Mouillac B, Mendre C. V 1b vasopressin receptor trafficking and signaling: Role of arrestins, G proteins and Src kinase. Traffic 2018; 19:58-82. [PMID: 29044966 DOI: 10.1111/tra.12535] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/13/2017] [Accepted: 10/13/2017] [Indexed: 11/29/2022]
Abstract
The signaling pathway of G protein-coupled receptors is strongly linked to their trafficking profile. Little is known about the molecular mechanisms involved in the vasopressin receptor V1b subtype (V1b R) trafficking and its impact on receptor signaling and regulation. For this purpose, we investigated the role of β-arrestins in receptor desensitization, internalization and recycling and attempted to dissect the V1b R-mediated MAP kinase pathway. Using MEF cells Knocked-out for β-arrestins 1 and 2, we demonstrated that both β-arrestins 1 and 2 play a fundamental role in internalization and recycling of V1b R with a rapid and transient V1b R-β-arrestin interaction in contrast to a slow and long-lasting β-arrestin recruitment of the V2 vasopressin receptor subtype (V2 R). Using V1b R-V2 R chimeras and V1b R C-terminus truncations, we demonstrated the critical role of the V1b R C-terminus in its interaction with β-arrestins thereby regulating the receptor internalization and recycling kinetics in a phosphorylation-independent manner. In parallel, V1b R MAP kinase activation was dependent on arrestins and Src-kinase but independent on G proteins. Interestingly, Src interacted with hV1b R at basal state and dissociated when receptor internalization occurred. Altogether, our data describe for the first time the trafficking profile and MAP kinase pathway of V1b R involving both arrestins and Src kinase family.
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Affiliation(s)
- Sanja Perkovska
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Catherine Méjean
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Mohammed Akli Ayoub
- Biology Department, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Juan Li
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Floriane Hemery
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Maithé Corbani
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Nadine Laguette
- INSERM, U1016, Institut Cochin, Paris, France.,CNRS, UMR 8104, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Maria-Angeles Ventura
- INSERM, U1016, Institut Cochin, Paris, France.,CNRS, UMR 8104, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Hélène Orcel
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Thierry Durroux
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Bernard Mouillac
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
| | - Christiane Mendre
- Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5203, Institut de Génomique Fonctionnelle (IGF), Montpellier, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1191, Montpellier, France.,Université de Montpellier, Montpellier, France
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12
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Bayerl DS, Bosch OJ. Brain vasopressin signaling modulates aspects of maternal behavior in lactating rats. GENES BRAIN AND BEHAVIOR 2018; 18:e12517. [DOI: 10.1111/gbb.12517] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 08/22/2018] [Accepted: 09/11/2018] [Indexed: 12/22/2022]
Affiliation(s)
- Doris S. Bayerl
- Department of Behavioural and Molecular Neurobiology; Regensburg Center of Neuroscience, University of Regensburg; Regensburg Germany
| | - Oliver J. Bosch
- Department of Behavioural and Molecular Neurobiology; Regensburg Center of Neuroscience, University of Regensburg; Regensburg Germany
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13
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Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors. Sci Rep 2016; 6:25327. [PMID: 27138239 PMCID: PMC4853784 DOI: 10.1038/srep25327] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 04/15/2016] [Indexed: 12/11/2022] Open
Abstract
Reducing Na+ in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na+-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na+ sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na+ increased cell surface [3H]AVP binding and decreased receptor internalization. Substitution of Na+ by Cs+ or NH4+ inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na+ over Cs+. Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations.
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14
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Gaudet HM, Cheng SB, Christensen EM, Filardo EJ. The G-protein coupled estrogen receptor, GPER: The inside and inside-out story. Mol Cell Endocrinol 2015; 418 Pt 3:207-19. [PMID: 26190834 DOI: 10.1016/j.mce.2015.07.016] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 07/15/2015] [Accepted: 07/15/2015] [Indexed: 02/06/2023]
Abstract
GPER possesses structural and functional characteristics shared by members of the G-protein-coupled receptor (GPCR) superfamily, the largest class of plasma membrane receptors. This newly appreciated estrogen receptor is localized predominately within intracellular membranes in most, but not all, cell types and its surface expression is modulated by steroid hormones and during tissue injury. An intracellular staining pattern is not unique among GPCRs, which employ a diverse array of molecular mechanisms that restrict cell surface expression and effectively regulating receptor binding and activation. The finding that GPER displays an intracellular predisposition has created some confusion as the estrogen-inducible transcription factors, ERα and ERβ, also reside intracellularly, and has led to complex suggestions of receptor interaction. GPER undergoes constitutive retrograde trafficking from the plasma membrane to the endoplasmic reticulum and recent studies indicate its interaction with PDZ binding proteins that sort transmembrane receptors to synaptosomes and endosomes. Genetic targeting and selective ligand approaches as well as cell models that express GPER in the absence of ERs clearly supports GPER as a bonafide "stand alone" receptor. Here, the molecular details that regulate GPER action, its cell biological activities and its implicated roles in physiological and pathological processes are reviewed.
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Affiliation(s)
- H M Gaudet
- Wheaton College, Department of Chemistry, Norton, MA, 02766, USA
| | - S B Cheng
- Women & Infants Hospital, Brown University, Providence, RI, 02903, USA
| | - E M Christensen
- Wheaton College, Department of Chemistry, Norton, MA, 02766, USA
| | - E J Filardo
- Rhode Island Hospital, Brown University, Providence, RI, 02903, USA.
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15
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Kashiwazaki A, Fujiwara Y, Tsuchiya H, Sakai N, Shibata K, Koshimizu TA. Subcellular localization and internalization of the vasopressin V1B receptor. Eur J Pharmacol 2015; 765:291-9. [PMID: 26318147 DOI: 10.1016/j.ejphar.2015.08.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 08/20/2015] [Accepted: 08/25/2015] [Indexed: 01/14/2023]
Abstract
Only limited information is available on agonist-dependent changes in the subcellular localization of vasopressin V1B receptors. Our radioligand binding study of membrane preparations and intact cells revealed that a large fraction of the V1B receptor is located in the cytoplasm in unstimulated CHO cells, which is in contrast to the plasma membrane localization of the V1A and V2 receptors. Moreover, when the affinity of radiolabeled arginine-vasopressin ([3H]AVP) was compared between membrane preparations and intact cells, the affinity of [3H]AVP to the cell surface V1B receptors, but not the V1A receptors, was significantly reduced. Although the number and affinity of cell surface V1B receptors decreased, they became extensively internalized upon binding with [3H]AVP. Approximately 87% of cell surface-bound [3H]AVP was internalized and became resistant to acid wash during incubation with 1 nM [3H]AVP. By contrast, less ligand (35%) was internalized in the cells expressing the V1A receptor. Extensive internalization of the V1B receptors was partially attenuated by inhibitors of cytoskeletal proteins, siRNA against β-arrestin 2, or the removal of sodium chloride from the extracellular buffer, indicating that this internalization involves clathrin-coated pits. Together, these results indicate that the mechanism that regulates the number and affinity of V1B receptors in the plasma membrane is markedly distinct from the corresponding mechanisms for the V1A and V2 receptors and plays a critical role under stress conditions, when vasopressin release is augmented.
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Affiliation(s)
- Aki Kashiwazaki
- Division of Molecular Pharmacology, Department of Pharmacology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Yoko Fujiwara
- Division of Molecular Pharmacology, Department of Pharmacology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Hiroyoshi Tsuchiya
- Division of Molecular Pharmacology, Department of Pharmacology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Nobuya Sakai
- Department of Functional Genomics, Graduate School of Pharmaceutical Sciences, Himeji Dokkyo University, Hyogo 670-8524, Japan
| | - Katsushi Shibata
- Department of Functional Genomics, Graduate School of Pharmaceutical Sciences, Himeji Dokkyo University, Hyogo 670-8524, Japan
| | - Taka-aki Koshimizu
- Division of Molecular Pharmacology, Department of Pharmacology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan.
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16
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Levoye A, Zwier JM, Jaracz-Ros A, Klipfel L, Cottet M, Maurel D, Bdioui S, Balabanian K, Prézeau L, Trinquet E, Durroux T, Bachelerie F. A Broad G Protein-Coupled Receptor Internalization Assay that Combines SNAP-Tag Labeling, Diffusion-Enhanced Resonance Energy Transfer, and a Highly Emissive Terbium Cryptate. Front Endocrinol (Lausanne) 2015; 6:167. [PMID: 26617570 PMCID: PMC4638144 DOI: 10.3389/fendo.2015.00167] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 10/19/2015] [Indexed: 12/15/2022] Open
Abstract
Although G protein-coupled receptor (GPCR) internalization has long been considered as a major aspect of the desensitization process that tunes ligand responsiveness, internalization is also involved in receptor resensitization and signaling, as well as the ligand scavenging function of some atypical receptors. Internalization thus contributes to the diversity of GPCR-dependent signaling, and its dynamics and quantification in living cells has generated considerable interest. We developed a robust and sensitive assay to follow and quantify ligand-induced and constitutive-induced GPCR internalization but also receptor recycling in living cells. This assay is based on diffusion-enhanced resonance energy transfer (DERET) between cell surface GPCRs labeled with a luminescent terbium cryptate donor and a fluorescein acceptor present in the culture medium. GPCR internalization results in a quantifiable reduction of energy transfer. This method yields a high signal-to-noise ratio due to time-resolved measurements. For various GPCRs belonging to different classes, we demonstrated that constitutive and ligand-induced internalization could be monitored as a function of time and ligand concentration, thus allowing accurate quantitative determination of kinetics of receptor internalization but also half-maximal effective or inhibitory concentrations of compounds. In addition to its selectivity and sensitivity, we provided evidence that DERET-based internalization assay is particularly suitable for characterizing biased ligands. Furthermore, the determination of a Z'-factor value of 0.45 indicates the quality and suitability of DERET-based internalization assay for high-throughput screening (HTS) of compounds that may modulate GPCRs internalization.
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Affiliation(s)
- Angélique Levoye
- INSERM U1148, Laboratory of Vascular Translational Science, Université Paris 13, Sorbonne Paris Cité, Paris, France
- *Correspondence: Angélique Levoye,
| | | | - Agnieszka Jaracz-Ros
- INSERM UMR996, Inflammation, Chemokines and Immunopathology, Université Paris-Sud, Université Paris-Saclay, Clamart, France
| | - Laurence Klipfel
- INSERM UMR996, Inflammation, Chemokines and Immunopathology, Université Paris-Sud, Université Paris-Saclay, Clamart, France
| | - Martin Cottet
- CNRS UMR 5203, INSERM U1191, Institut de Génomique Fonctionnelle, Université Montpellier 1 & 2, Montpellier, France
| | - Damien Maurel
- CNRS UMR 5203, INSERM U1191, Institut de Génomique Fonctionnelle, Université Montpellier 1 & 2, Montpellier, France
| | | | - Karl Balabanian
- INSERM UMR996, Inflammation, Chemokines and Immunopathology, Université Paris-Sud, Université Paris-Saclay, Clamart, France
| | - Laurent Prézeau
- CNRS UMR 5203, INSERM U1191, Institut de Génomique Fonctionnelle, Université Montpellier 1 & 2, Montpellier, France
| | | | - Thierry Durroux
- CNRS UMR 5203, INSERM U1191, Institut de Génomique Fonctionnelle, Université Montpellier 1 & 2, Montpellier, France
| | - Françoise Bachelerie
- INSERM UMR996, Inflammation, Chemokines and Immunopathology, Université Paris-Sud, Université Paris-Saclay, Clamart, France
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17
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Brignone MS, Lanciotti A, Visentin S, De Nuccio C, Molinari P, Camerini S, Diociaiuti M, Petrini S, Minnone G, Crescenzi M, Laudiero LB, Bertini E, Petrucci TC, Ambrosini E. Megalencephalic leukoencephalopathy with subcortical cysts protein-1 modulates endosomal pH and protein trafficking in astrocytes: relevance to MLC disease pathogenesis. Neurobiol Dis 2014; 66:1-18. [PMID: 24561067 PMCID: PMC4003525 DOI: 10.1016/j.nbd.2014.02.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 01/20/2014] [Accepted: 02/10/2014] [Indexed: 11/28/2022] Open
Abstract
Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare leukodystrophy caused by mutations in the gene encoding MLC1, a membrane protein mainly expressed in astrocytes in the central nervous system. Although MLC1 function is unknown, evidence is emerging that it may regulate ion fluxes. Using biochemical and proteomic approaches to identify MLC1 interactors and elucidate MLC1 function we found that MLC1 interacts with the vacuolar ATPase (V-ATPase), the proton pump that regulates endosomal acidity. Because we previously showed that in intracellular organelles MLC1 directly binds Na, K-ATPase, which controls endosomal pH, we studied MLC1 endosomal localization and trafficking and MLC1 effects on endosomal acidity and function using human astrocytoma cells overexpressing wild-type (WT) MLC1 or MLC1 carrying pathological mutations. We found that WT MLC1 is abundantly expressed in early (EEA1(+), Rab5(+)) and recycling (Rab11(+)) endosomes and uses the latter compartment to traffic to the plasma membrane during hyposmotic stress. We also showed that WT MLC1 limits early endosomal acidification and influences protein trafficking in astrocytoma cells by stimulating protein recycling, as revealed by FITC-dextran measurement of endosomal pH and transferrin protein recycling assay, respectively. WT MLC1 also favors recycling to the plasma-membrane of the TRPV4 cation channel which cooperates with MLC1 to activate calcium influx in astrocytes during hyposmotic stress. Although MLC disease-causing mutations differentially affect MLC1 localization and trafficking, all the mutated proteins fail to influence endosomal pH and protein recycling. This study demonstrates that MLC1 modulates endosomal pH and protein trafficking suggesting that alteration of these processes contributes to MLC pathogenesis.
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Affiliation(s)
- Maria S Brignone
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Angela Lanciotti
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Sergio Visentin
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Chiara De Nuccio
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Paola Molinari
- Department of Pharmacology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Serena Camerini
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Marco Diociaiuti
- Department of Technology and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Stefania Petrini
- Unit of Neurodegenerative Disorders, Laboratory of Molecular Medicine, Bambino Gesù Pediatric Research Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy.
| | - Gaetana Minnone
- Unit of Neurodegenerative Disorders, Laboratory of Molecular Medicine, Bambino Gesù Pediatric Research Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy.
| | - Marco Crescenzi
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Luisa Bracci Laudiero
- Unit of Neurodegenerative Disorders, Laboratory of Molecular Medicine, Bambino Gesù Pediatric Research Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy; Institute of Translational Pharmacology, CNR, Via del Fosso Cavaliere 100, 00133 Rome, Italy.
| | - Enrico Bertini
- Unit of Neurodegenerative Disorders, Laboratory of Molecular Medicine, Bambino Gesù Pediatric Research Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy.
| | - Tamara C Petrucci
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
| | - Elena Ambrosini
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
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Dimers of G-protein coupled receptors as versatile storage and response units. Int J Mol Sci 2014; 15:4856-77. [PMID: 24651459 PMCID: PMC3975428 DOI: 10.3390/ijms15034856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 02/28/2014] [Accepted: 03/04/2014] [Indexed: 11/17/2022] Open
Abstract
The status and use of transmembrane, extracellular and intracellular domains in oligomerization of heptahelical G-protein coupled receptors (GPCRs) are reviewed and for transmembrane assemblies also supplemented by new experimental evidence. The transmembrane-linked GPCR oligomers typically have as the minimal unit an asymmetric ~180 kDa pentamer consisting of receptor homodimer or heterodimer and a G-protein αβγ subunit heterotrimer. With neuropeptide Y (NPY) receptors, this assembly is converted to ~90 kDa receptor monomer-Gα complex by receptor and Gα agonists, and dimers/heteropentamers are depleted by neutralization of Gαi subunits by pertussis toxin. Employing gradient centrifugation, quantification and other characterization of GPCR dimers at the level of physically isolated and identified heteropentamers is feasible with labeled agonists that do not dissociate upon solubilization. This is demonstrated with three neuropeptide Y (NPY) receptors and could apply to many receptors that use large peptidic agonists.
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Jean-Alphonse F, Bowersox S, Chen S, Beard G, Puthenveedu MA, Hanyaloglu AC. Spatially restricted G protein-coupled receptor activity via divergent endocytic compartments. J Biol Chem 2013; 289:3960-77. [PMID: 24375413 PMCID: PMC3924264 DOI: 10.1074/jbc.m113.526350] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Postendocytic sorting of G protein-coupled receptors (GPCRs) is driven by their interactions between highly diverse receptor sequence motifs with their interacting proteins, such as postsynaptic density protein (PSD95), Drosophila disc large tumor suppressor (Dlg1), zonula occludens-1 protein (zo-1) (PDZ) domain proteins. However, whether these diverse interactions provide an underlying functional specificity, in addition to driving sorting, is unknown. Here we identify GPCRs that recycle via distinct PDZ ligand/PDZ protein pairs that exploit their recycling machinery primarily for targeted endosomal localization and signaling specificity. The luteinizing hormone receptor (LHR) and β2-adrenergic receptor (B2AR), two GPCRs sorted to the regulated recycling pathway, underwent divergent trafficking to distinct endosomal compartments. Unlike B2AR, which traffics to early endosomes (EE), LHR internalizes to distinct pre-early endosomes (pre-EEs) for its recycling. Pre-EE localization required interactions of the LHR C-terminal tail with the PDZ protein GAIP-interacting protein C terminus, inhibiting its traffic to EEs. Rerouting the LHR to EEs, or EE-localized GPCRs to pre-EEs, spatially reprograms MAPK signaling. Furthermore, LHR-mediated activation of MAPK signaling requires internalization and is maintained upon loss of the EE compartment. We propose that combinatorial specificity between GPCR sorting sequences and interacting proteins dictates an unprecedented spatiotemporal control in GPCR signal activity.
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Affiliation(s)
- Frederic Jean-Alphonse
- From the Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, London W12 0NN, United Kingdom and
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20
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Brønd L, Müllertz KM, Torp M, Nielsen J, Graebe M, Hadrup N, Nielsen S, Christensen S, Jonassen TEN. Congestive heart failure in rats is associated with increased collecting duct vasopressin sensitivity and vasopressin type 2 receptor reexternalization. Am J Physiol Renal Physiol 2013; 305:F1547-54. [PMID: 24089411 DOI: 10.1152/ajprenal.00461.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A number of studies have shown that rats with congestive heart failure (CHF) have increased protein levels of the vasopressin (AVP)-regulated water channel aquaporin-2 (AQP2) even during conditions with unchanged circulating levels of AVP, suggesting an increase in the sensitivity of the AVP type 2 (V2) receptor in experimental CHF. The present study was aimed at investigating AVP signaling in rats with moderate CHF (left ventricular end diastolic pressure >10 mmHg; normal plasma AVP levels) induced by ligation of the left anterior descending coronary artery. Sham-operated rats were used as controls. Western blotting analyses revealed an increased abundance of AQP2 in renal cortex (+33 ± 9% of sham; P < 0.05) and in inner medulla (IM) (+54 ± 15% of sham; P < 0.05) in CHF rats compared with sham-operated controls. Dose-response studies on isolated collecting ducts (CDs) showed an increased accumulation of cAMP in response to AVP in CHF rats compared with controls. V2 receptor surface-binding studies in isolated IMCDs showed a marked and comparable AVP-induced V2 receptor internalization in response to AVP in both CHF and control rats. As expected V2 receptor surface binding remained low after AVP challenge in control rats. In contrast to this, V2 receptor surface binding returned to pre-AVP levels within 30 min in the CHF rats, indicating an obtained recycling ability of the V2 receptor in CHF. Together the results indicate the presence of an increased AVP sensitivity in the CDs from CHF rats, associated with an acquired recycling ability of the V2 receptor.
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Affiliation(s)
- Lone Brønd
- Dept. of Biomedical Sciences, Univ. of Copenhagen, 3 Blegdamsvej, Bldg. 10.5, DK-2200 Copenhagen N, Denmark.
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21
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Japundžić-Žigon N. Vasopressin and oxytocin in control of the cardiovascular system. Curr Neuropharmacol 2013; 11:218-30. [PMID: 23997756 PMCID: PMC3637675 DOI: 10.2174/1570159x11311020008] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 11/01/2012] [Accepted: 12/03/2012] [Indexed: 12/31/2022] Open
Abstract
Vasopressin (VP) and oxytocin (OT) are mainly synthesized in the magnocellular neurons of the paraventricular (PVN) and supraoptic nucleus (SON) of the hypothalamus. Axons from the magnocellular part of the PVN and SON project to neurohypophysis where VP and OT are released in blood to act like hormones. Axons from the parvocellular part of PVN project to extra-hypothalamic brain areas (median eminence, limbic system, brainstem and spinal cord) where VP and OT act like neurotransmitters/modulators. VP and OT act in complementary manner in cardiovascular control, both as hormones and neurotransmitters. While VP conserves water and increases circulating blood volume, OT eliminates sodium. Hyperactivity of VP neurons and quiescence of OT neurons in PVN underlie osmotic adjustment to pregnancy. In most vascular beds VP is a potent vasoconstrictor, more potent than OT, except in the umbilical artery at term. The vasoconstriction by VP and OT is mediated via V1aR. In some vascular beds, i.e. the lungs and the brain, VP and OT produce NO dependent vasodilatation. Peripherally, VP has been found to enhance the sensitivity of the baro-receptor while centrally, VP and OT increase sympathetic outflow, suppresse baro-receptor reflex and enhance respiration. Whilst VP is an important mediator of stress that triggers ACTH release, OT exhibits anti-stress properties. Moreover, VP has been found to contribute considerably to progression of hypertension and heart failure while OT has been found to decrease blood pressure and promote cardiac healing.
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Affiliation(s)
- Nina Japundžić-Žigon
- Professor of Basic and Clinical Pharmacology and Toxicology, University of Belgrade School of Medicine, Institute of Pharmacology, Clinical Pharmacology and Toxicology, Dr Subotica 1, Belgrade, Republic of Serbia
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22
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Abstract
Comprising over 60 members, Rab proteins constitute the largest branch of the Ras superfamily of low-molecular-mass G-proteins. This protein family have been primarily implicated in various aspects of intracellular membrane trafficking processes. On the basis of distinct subfamily-specific sequence motifs, many Rabs have been grouped into subfamilies. The Rab11 GTPase subfamily comprises three members: Rab11a, Rab11b and Rab25/Rab11c, which, between them, have been demonstrated to bind more than 30 proteins. In the present paper, we review the function of the Rab11 subfamily. We describe their localization and primary functional roles within the cell and their implication, to date, in disease processes. We also summarize the protein machinery currently known to regulate or mediate their functions and the cargo molecules which they have been shown to transport.
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Effects of the β-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of β2-adrenergic receptors with N-terminal polymorphisms. Cell Biol Int 2013; 36:1171-83. [PMID: 22938397 DOI: 10.1042/cbi20120134] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The β2-AR (β2-adrenergic receptor) is an important target for respiratory and CVD (cardiovascular disease) medications. Clinical studies suggest that N-terminal polymorphisms of β2-AR may act as disease modifiers. We hypothesized that polymorphisms at amino acids 16 and 27 result in differential trafficking and down-regulation of β2-AR variants following β-agonist exposure. The functional consequences of the four possible combinations of these polymorphisms in the human β2-AR (designated β2-AR-RE, β2-AR-GE, β2-AR-RQ and β2-AR-GQ) were studied using site-directed mutagenesis and recombinant expression in HEK-293 cells (human embryonic kidney cells). Ligand-binding assays demonstrated that after 24 h exposure to 1 μM isoprenaline, isoforms with Arg16 (β2-AR-RE and β2-AR-RQ) underwent increased down-regulation compared with isoforms with Gly16 (β2-AR-GE and β2-AR-GQ). Consistent with these differences in down-regulation between isoforms, prolonged isoprenaline treatment resulted in diminished cAMP response to subsequent isoprenaline challenge in β2-AR-RE relative to β2-AR-GE. Confocal microscopy revealed that the receptor isoforms had similar co-localization with the early endosomal marker EEA1 following isoprenaline treatment, suggesting that they had similar patterns of internalization. None of the isoforms exhibited significant co-localization with the recycling endosome marker Rab11 in response to isoprenaline treatment. Furthermore, we found that prolonged isoprenaline treatment led to a higher degree of co-localization of β2-AR-RE with the lysosomal marker LAMP1 (lysosome-associated membrane protein 1) compared with that of β2-AR-GE. Taken together, these results indicate that a mechanism responsible for differential responses of these receptor isoforms to the β-agonist involves differences in the efficiency with which agonist-activated receptors are trafficked to the lysosomes for degradation, or differences in degradation in the lysosomes.
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Charest-Morin X, Fortin S, Lodge R, Roy C, Gera L, Gaudreault RC, Marceau F. Inhibitory effects of cytoskeleton disrupting drugs and GDP-locked Rab mutants on bradykinin B₂ receptor cycling. Pharmacol Res 2013; 71:44-52. [PMID: 23454239 DOI: 10.1016/j.phrs.2013.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 02/18/2013] [Accepted: 02/19/2013] [Indexed: 12/25/2022]
Abstract
The bradykinin (BK) B₂ receptor (B₂R) is G protein coupled and phosphorylated upon agonist stimulation; its endocytosis and recycling are documented. We assessed the effect of drugs that affect the cytoskeleton on B2R cycling. These drugs were targeted to tubulin (paclitaxel, or the novel combretastatin A-4 mimetic 3,4,5-trimethoxyphenyl-4-(2-oxoimidazolidin-1-yl)benzenesulfonate [IMZ-602]) and actin (cytochalasin D). Tubulin ligands did not alter agonist-induced receptor endocytosis, as shown using antibodies reactive with myc-tagged B₂Rs (microscopy, cytofluorometry), but rather reduced the progression of the ligand-receptor-β-arrestin complex from the cell periphery to the interior. The 3 fluorescent probes of this complex (B2R-green fluorescent protein [B2R-GFP], the fluorescent agonist fluorescein-5-thiocarbamoyl-D-Arg-[Hyp³, Igl⁵, Oic⁷, Igl⁸]-BK and β-arrestin2-GFP) were condensed in punctuate structures that remained close to the cell surface in the presence of IMZ-602. Cytochalasin D selectively inhibited the recycling of endocytosed B₂R-GFP (B₂R-GFP imaging, [³H]BK binding). Dominant negative (GDP-locked)-Rab5 and -Rab11 reproduced the effects of inhibitors of tubulin and actin, respectively, on the cycling of B₂R-GFP. GDP-locked-Rab4 also inhibited B₂R-GFP recycling to the cell surface. Consistent with the displacement of cargo along specific cytoskeletal elements, Rab5-associated progression of the endocytosed BK B₂R follows microtubules toward their (-) end, while its recycling progresses along actin fibers to the cell surface. However, tubulin ligands do not suppress the tested desensitization or resensitization mechanisms of the B₂R.
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Affiliation(s)
- Xavier Charest-Morin
- Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, Québec, QC G1V 4G2, Canada
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25
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Walther C, Ferguson SSG. Arrestins: role in the desensitization, sequestration, and vesicular trafficking of G protein-coupled receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:93-113. [PMID: 23764051 DOI: 10.1016/b978-0-12-394440-5.00004-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Over the years, β-arrestins have emerged as multifunctional molecular scaffolding proteins regulating almost every imaginable G protein-coupled receptor (GPCR) function. Originally discovered as GPCR-desensitizing molecules, they have been shown to also serve as important regulators of GPCR signaling, sequestration, and vesicular trafficking. This broad functional role implicates β-arrestins as key regulatory proteins for cellular function. Hence, this chapter summarizes the current understanding of the β-arrestin family's unique ability to control the kinetics as well as the extent of GPCR activity at the level of desensitization, sequestration, and subsequent intracellular trafficking.
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Affiliation(s)
- Cornelia Walther
- J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute, Western University Canada, London, Ontario, Canada
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26
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Tracing the endocytic pathways and trafficking kinetics of cell signaling receptors using single QD nanoparticles. Methods Mol Biol 2013; 991:237-47. [PMID: 23546674 DOI: 10.1007/978-1-62703-336-7_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cellular signaling is the fundamental process through which cells communicate with each other and respond to their environment. Regulation of this cellular signaling is crucial for healthy cellular function. Malfunctions in signaling are the cause for many diseases and disorders and therefore are under heavy investigation. The molecular mechanisms that underlie cellular signaling rely upon complex and dynamic processes of receptor intracellular trafficking. The specific endosomal pathways and kinetics through which receptors are intracellularly transported regulate the strength and duration of cellular signaling. In even more subtle and complex aspects, the cell orchestrates the individual motions of many receptors, through multiple different pathways, simultaneously. Despite the fundamental role of endosomal trafficking in signal regulation, it has been technically challenging to study since intracellular trafficking is complex and dynamic, with millions of individual receptors simultaneously undergoing trafficking in different endocytic stages. Here, we describe the use of single nanoparticle quantum dot (QD) probes to quantitatively investigate the endocytic trafficking pathways that receptors undergo following ligand activation. This new capability to directly visualize and quantitate cellular signaling at the level of individual receptors inside the cell has broad and important value for understanding fundamental cell signaling processes and the action and effect of therapeutics upon signaling.
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27
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Bouley R, Nunes P, Andriopoulos B, McLaughlin M, Webber MJ, Lin HY, Babitt JL, Gardella TJ, Ausiello DA, Brown D. Heterologous downregulation of vasopressin type 2 receptor is induced by transferrin. Am J Physiol Renal Physiol 2012; 304:F553-64. [PMID: 23235478 DOI: 10.1152/ajprenal.00438.2011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vasopressin (VP) binds to the vasopressin type 2 receptor (V2R) to trigger physiological effects including body fluid homeostasis and blood pressure regulation. Signaling is terminated by receptor downregulation involving clathrin-mediated endocytosis and V2R degradation. We report here that both native and epitope-tagged V2R are internalized from the plasma membrane of LLC-PK1 kidney epithelial cells in the presence of another ligand, transferrin (Tf). The presence of iron-saturated Tf (holo-Tf; 4 h) reduced V2R binding sites at the cell surface by up to 33% while iron-free (apo-Tf) had no effect. However, no change in green fluorescent protein-tagged V2R distribution was observed in the presence of bovine serum albumin, atrial natriuretic peptide, or ANG II. Conversely, holo-Tf did not induce the internalization of another G protein-coupled receptor, the parathyroid hormone receptor. In contrast to the effect of VP, Tf did not increase intracellular cAMP or modify aquaporin-2 distribution in these cells, although addition of VP and Tf together augmented VP-induced V2R internalization. Tf receptor coimmunoprecipitated with V2R, suggesting that they interact closely, which may explain the additive effect of VP and Tf on V2R endocytosis. Furthermore, Tf-induced V2R internalization was abolished in cells expressing a dominant negative dynamin (K44A) mutant, indicating the involvement of clathrin-coated pits. We conclude that Tf can induce heterologous downregulation of the V2R and this might desensitize VP target cells without activating downstream V2R signaling events. It also provides new insights into urine-concentrating defects observed in rat models of hemochromatosis.
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Affiliation(s)
- Richard Bouley
- 1Nephrology Division, MGH Center for Systems Biology, Program in Membrane Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
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28
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Koshimizu TA, Nakamura K, Egashira N, Hiroyama M, Nonoguchi H, Tanoue A. Vasopressin V1a and V1b Receptors: From Molecules to Physiological Systems. Physiol Rev 2012; 92:1813-64. [DOI: 10.1152/physrev.00035.2011] [Citation(s) in RCA: 250] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The neurohypophysial hormone arginine vasopressin (AVP) is essential for a wide range of physiological functions, including water reabsorption, cardiovascular homeostasis, hormone secretion, and social behavior. These and other actions of AVP are mediated by at least three distinct receptor subtypes: V1a, V1b, and V2. Although the antidiuretic action of AVP and V2 receptor in renal distal tubules and collecting ducts is relatively well understood, recent years have seen an increasing understanding of the physiological roles of V1a and V1b receptors. The V1a receptor is originally found in the vascular smooth muscle and the V1b receptor in the anterior pituitary. Deletion of V1a or V1b receptor genes in mice revealed that the contributions of these receptors extend far beyond cardiovascular or hormone-secreting functions. Together with extensively developed pharmacological tools, genetically altered rodent models have advanced the understanding of a variety of AVP systems. Our report reviews the findings in this important field by covering a wide range of research, from the molecular physiology of V1a and V1b receptors to studies on whole animals, including gene knockout/knockdown studies.
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Affiliation(s)
- Taka-aki Koshimizu
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
| | - Kazuaki Nakamura
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
| | - Nobuaki Egashira
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
| | - Masami Hiroyama
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
| | - Hiroshi Nonoguchi
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
| | - Akito Tanoue
- Department of Pharmacology, Division of Molecular Pharmacology, Jichi Medical University, Tochigi, Japan; Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan; Department of Pharmacy, Kyushu University Hospital, Fukuoka, Japan; and Department of Internal Medicine, Kitasato University, Kitasato Institute Medical Center Hospital, Saitama, Japan
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Cheng SB, Filardo EJ. Trans-Golgi Network (TGN) as a regulatory node for β1-adrenergic receptor (β1AR) down-modulation and recycling. J Biol Chem 2012; 287:14178-91. [PMID: 22378779 DOI: 10.1074/jbc.m111.323782] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Receptor down-modulation is the key mechanism by which G protein-coupled receptors (GPCRs) prevent excessive receptor signaling in response to agonist stimulation. Recently, the trans-Golgi network (TGN) has been implicated as a key checkpoint for receptor endocytosis and degradation. Here, we investigated the involvement of the TGN in down-modulation of β1-adrenergic receptor in response to persistent isoprotenerol stimulation. Immunofluorescent staining showed that ~50% of endocytosed β1AR colocalized with TGN-46 at 5 h. Disruption of the TGN by brefeldin A (BFA) led to the robust accumulation of endocytosed β1AR in Rab11(+) recycling endosomes, inhibited β1AR entry into LAMP1(+) lysosomes, and as a result enhanced β1AR recycling to the plasma membrane. The lysosomotropic agent, chloroquine, arrested the majority of endocytosed β1AR in the TGN by 4 h. Immunoblot analysis showed that either disruption of the TGN or blockage of the lysosome prevented β1AR degradation. Co-expression of GFP-arrestin-3 in β1AR cells increased the endocytosis of β1AR and facilitated its entry to the TGN but inhibited recycling to the plasma membrane. Arrestin-3-induced inhibition of β1AR recycling was reversed by BFA treatment, whereas chloroquine induced the accumulation of arrestin-3 with β1AR in the TGN. These results demonstrate for the first time that the TGN acts as a checkpoint for both the recycling and down-regulation of β1AR and that arrestin-3 not only mediates β1AR endocytosis but also its recycling through the TGN.
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Affiliation(s)
- Shi-Bin Cheng
- Division of Hematology and Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903, USA
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30
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Carmosino M, Procino G, Tamma G, Mannucci R, Svelto M, Valenti G. Trafficking and phosphorylation dynamics of AQP4 in histamine-treated human gastric cells. Biol Cell 2012; 99:25-36. [PMID: 16895520 DOI: 10.1042/bc20060068] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION AQP4 (aquaporin 4) internalization and a concomitant decrease in the osmotic water permeability coefficient (Pf) after histamine exposure has been reported in AQP4-transfected gastric HGT1 cells. RESULTS In the present study we report that AQP4 internalization is followed by an increase in AQP4 phosphorylation. Histamine treatment for 30 min resulted in an approx. 10-fold increase in AQP4 phosphorylation that was inhibited by 1 microM H89, a specific PKA (protein kinase A) inhibitor, but not by PKC (protein kinase C) and CK2 inhibitors. Moreover, measurement of PKA activity after 30 min of histamine treatment showed that PKA activity was approx. 3-fold higher compared with basal conditions. AQP4 phosphorylation was prevented in cells treated with histamine for 30 min after pre-incubation with PAO (phenylarsine oxide), an inhibitor of protein endocytosis. Using an endo-exocytosis assay we showed that, after histamine washed out, internalized AQP4 recycled back to the cell surface, even in cells in which de novo protein synthesis was inhibited by cycloheximide. CONCLUSIONS Phosphorylation experiments, combined with immunolocalization studies, indicated that AQP4 phosphorylation is mediated by PKA and occurs subsequently to its internalization in late endosomes. We suggest that phosphorylation might be a mechanism involved in retaining AQP4 in a vesicle-recycling compartment.
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Affiliation(s)
- Monica Carmosino
- Department of General and Environmental Physiology, University of Bari, Via Amendola 165/A, 70126 Bari, Italy
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31
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Cook JL, Re RN. Lessons from in vitro studies and a related intracellular angiotensin II transgenic mouse model. Am J Physiol Regul Integr Comp Physiol 2011; 302:R482-93. [PMID: 22170617 DOI: 10.1152/ajpregu.00493.2011] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the classical renin-angiotensin system, circulating ANG II mediates growth stimulatory and hemodynamic effects through the plasma membrane ANG II type I receptor, AT1. ANG II also exists in the intracellular space in some native cells, and tissues and can be upregulated in diseases, including hypertension and diabetes. Moreover, intracellular AT1 receptors can be found associated with endosomes, nuclei, and mitochondria. Intracellular ANG II can function in a canonical fashion through the native receptor and also in a noncanonical fashion through interaction with alternative proteins. Likewise, the receptor and proteolytic fragments of the receptor can function independently of ANG II. Participation of the receptor and ligand in alternative intracellular pathways may serve to amplify events that are initiated at the plasma membrane. We review historical and current literature relevant to ANG II, compared with other intracrines, in tissue culture and transgenic models. In particular, we describe a new transgenic mouse model, which demonstrates that intracellular ANG II is linked to high blood pressure. Appreciation of the diverse, pleiotropic intracellular effects of components of the renin-angiotensin system should lead to alternative disease treatment targets and new therapies.
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Affiliation(s)
- Julia L Cook
- Laboratory of Molecular Genetics, Department of Research, New Orleans, LA 70121, USA.
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32
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Rosenfeld JL, Knoll BJ, Moore RH. Regulation of G-Protein-Coupled Receptor Activity by Rab GTPases. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820212398] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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33
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Krilov L, Nguyen A, Miyazaki T, Unson CG, Williams R, Lee NH, Ceryak S, Bouscarel B. Dual mode of glucagon receptor internalization: role of PKCα, GRKs and β-arrestins. Exp Cell Res 2011; 317:2981-94. [PMID: 22001118 DOI: 10.1016/j.yexcr.2011.10.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/29/2011] [Accepted: 10/01/2011] [Indexed: 10/17/2022]
Abstract
Glucagon levels are elevated in diabetes and some liver diseases. Increased glucagon secretion leads to abnormal stimulation of glucagon receptors (GRs) and consequent elevated glucose production in the liver. Blocking glucagon receptor signaling has been proposed as a potential treatment option for diabetes and other conditions associated with hyperglycemia. Elucidating mechanisms of GR desensitization and downregulation may help identify new drug targets besides GR itself. The present study explores the mechanisms of GR internalization and the role of PKCα, GPCR kinases (GRKs) and β-arrestins therein. We have reported previously that PKCα mediates GR phosphorylation and desensitization. While the PKC agonist, PMA, did not affect GR internalization when tested alone, it increased glucagon-mediated GR internalization by 25-40% in GR-expressing HEK-293 cells (HEK-GR cells). In both primary hepatocytes and HEK-GR cells, glucagon treatment recruited PKCα to the plasma membrane where it colocalized with GR. We also observed that overexpression of GRK2, GRK3, or GRK5 enhanced GR internalization. In addition, we found that GR utilizes both clathrin- and caveolin-mediated endocytosis in HEK-GR cells. Glucagon triggered translocation of both β-arrestin1 and β-arrestin2 from the cytosol to the perimembrane region, and overexpression of β-arrestin1 and β-arrestin2 increased GR internalization. Furthermore, both β-arrestin1 and β-arrestin2 colocalized with GR and with Cav-1, suggesting the possible involvement of these arrestins in GR internalization.
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Affiliation(s)
- Lada Krilov
- Gastroenterology Research Laboratory, Digestive Diseases Center, Department of Biochemistry and Molecular Biology, The George Washington University, Washington, DC, USA
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Chen S, Webber MJ, Vilardaga JP, Khatri A, Brown D, Ausiello DA, Lin HY, Bouley R. Visualizing microtubule-dependent vasopressin type 2 receptor trafficking using a new high-affinity fluorescent vasopressin ligand. Endocrinology 2011; 152:3893-904. [PMID: 21828182 PMCID: PMC3176653 DOI: 10.1210/en.2011-1049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The vasopressin receptor type 2 (V2R) is the major target of vasopressin (VP) in renal epithelial cells. Although it is known that VP induces V2R internalization, accumulation in the perinuclear area, and degradation, the V2R intracellular trafficking pathways remain elusive. We visualized this process by developing a new fluorescent VP analog tagged by tetramethylrhodamine (TMR)-[Lys-(PEG)(2)-Suc-TMR(8)]VP or (VP(TMR)). This ligand is fully functional as revealed by its high binding affinity toward V2R [(K(d)) =157 ± 52 nM] and ability to increase intracellular cAMP 32-fold. VP(TMR) induced V2R internalization in LLC-PK1 cells expressing either a FLAG-tagged receptor (FLAG-V2R) or V2R C-terminally tagged with green fluorescent protein (GFP) (V2R-GFP). After internalization, VP(TMR) and V2R-GFP colocalized in the perinuclear area, suggesting that the hormone and receptor traffic along the same pathway. VP(TMR) and V2R colocalized initially with the early endosome markers EEA1 and Rab5, and later with the recycling and late endosome markers Rab11 and Rab25. Epifluorescence microscopy of LLC-PK1 cells expressing GFP-tagged microtubules (MT) showed that VP(TMR)-containing vesicles travel along the MT network, and even remain attached to MT during the metaphase and anaphase of mitosis. Colchicine, a MT-depolymerizing agent, abolished perinuclear accumulation of VP(TMR), and Western blot analysis showed that VP-induced V2R-GFP degradation is markedly retarded, but not abolished, by colchicine (10 μM). We conclude that the new VP(TMR) ligand is suitable for dissecting V2R and VP internalization and trafficking in cells, and that V2R trafficking and down-regulation is an MT-dependent mechanism.
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Affiliation(s)
- Sylvia Chen
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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Endosomal trafficking of the G protein-coupled receptor somatostatin receptor 3. Biochem Biophys Res Commun 2011; 413:555-60. [PMID: 21925142 DOI: 10.1016/j.bbrc.2011.08.137] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 08/31/2011] [Indexed: 12/15/2022]
Abstract
Intracellular trafficking of G protein-coupled receptors (GPCRs) regulates their surface availability and determines cellular response to agonists. Rab GTPases regulate membrane trafficking and identifying Rab networks controlling GPCR trafficking is essential for understanding GPCR signaling. We used real time imaging to show that somatostatin receptor 3 (SSTR3) traffics through Rab4-, Rab21-, and Rab11-containing endosomes, but largely bypasses Rab5 and Rab7 endosomes. We show that SSTR3 rapidly traffics through Rab4 endosomes but moves slower through Rab21 and Rab11 endosomes. SSTR3 passage through each endosomal compartment is regulated by the cognate Rab since expression of the inactive Rab4/S22N, Rab21/T33N, and Rab11/S25N inhibits SSTR3 trafficking. Thus, Rab4, Rab21, and Rab11 may represent therapeutic targets to modulate surface availability of SSTR3 for agonist binding. Our novel finding that Rab21 regulates SSTR3 trafficking suggests that Rab21 may play a role in trafficking of other GPCRs.
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Huang H, Deng X, He X, Yang W, Li G, Shi Y, Shi L, Mei L, Gao J, Zhou N. Identification of distinct c-terminal domains of the Bombyx adipokinetic hormone receptor that are essential for receptor export, phosphorylation and internalization. Cell Signal 2011; 23:1455-65. [DOI: 10.1016/j.cellsig.2011.04.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 04/12/2011] [Indexed: 10/18/2022]
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Paavola KJ, Stephenson JR, Ritter SL, Alter SP, Hall RA. The N terminus of the adhesion G protein-coupled receptor GPR56 controls receptor signaling activity. J Biol Chem 2011; 286:28914-28921. [PMID: 21708946 PMCID: PMC3190698 DOI: 10.1074/jbc.m111.247973] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/16/2011] [Indexed: 12/18/2022] Open
Abstract
GPR56 is an adhesion G protein-coupled receptor that plays a key role in cortical development. Mutations to GPR56 in humans cause malformations of the cerebral cortex, but little is known about the normal function of the receptor. We found that the large N terminus (NT) of GPR56 is cleaved from the rest of the receptor during processing but remains non-covalently associated with the seven-transmembrane region of the receptor, as indicated by coimmunoprecipitation of the two GPR56 fragments from both transfected cells and native tissue. We also found that truncation of the GPR56 NT results in constitutive activation of receptor signaling, as revealed by increased GPR56-stimulated signaling upon transfection of HEK-293 cells with truncated GPR56, greatly enhanced binding of β-arrestins by truncated GPR56 relative to the full-length receptor, extensive ubiquitination of truncated GPR56, and cytotoxicity induced by truncated GPR56 that could be rescued by cotransfection of cells with β-arrestin 2. Furthermore, we found that the GPR56 NT is capable of homophilic trans-trans interactions that enhance receptor signaling activity. On the basis of these findings, we suggest a model of receptor activation in which the large N terminus of GPR56 constrains receptor activity but N-terminal interactions (GPR56 NT with an extracellular ligand and/or GPR56 NT homophilic trans-trans associations) can remove this inhibitory influence of the N terminus to activate receptor signaling.
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Affiliation(s)
- Kevin J Paavola
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
| | - Jason R Stephenson
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
| | - Stefanie L Ritter
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
| | - Shawn P Alter
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
| | - Randy A Hall
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia.
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Cheng SB, Graeber CT, Quinn JA, Filardo EJ. Retrograde transport of the transmembrane estrogen receptor, G-protein-coupled-receptor-30 (GPR30/GPER) from the plasma membrane towards the nucleus. Steroids 2011; 76:892-6. [PMID: 21354433 DOI: 10.1016/j.steroids.2011.02.018] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 01/25/2011] [Accepted: 02/16/2011] [Indexed: 01/05/2023]
Abstract
G-protein-coupled receptor 30 (GPR30/GPER) belongs to the seven transmembrane receptor (7TMR) superfamily, the most common class of surface receptor with approximately 800 known members. GPER promotes estrogen binding and rapid signaling via membrane-associated enzymes resulting in increased cAMP and release of heparan bound epidermal growth factor (proHB-EGF) from breast cancer cells. However, GPER is predominately localized intracellularly in breast cancer cells with minor amounts of receptor on the cell surface, an observation that has caused some controversy regarding its potential role as a plasma membrane estrogen receptor. Using the widely employed approach of tracking recombinant 7TMRs by surface labeling live cells, we have begun to characterize and compare the endocytic fate of GPER to other similarly labeled 7TMRs. Upon ectopic expression in human embryonic kidney HEK-293 cells, functional GPER is generated as these cells acquire the capacity to stimulate cAMP and activate cyclic AMP responsive binding protein in response to estradiol-17 beta stimulation. GPER is detectable on the cell surface by immunofluorescent analysis using HA-specific antibodies, albeit the bulk of the receptor is located intracellularly. Like β1AR (beta 1 adrenergic receptor) and CXCR4 (C-X-C chemokine receptor 4), GPER exits the plasma membrane via clathrin-coated pits and enters early endosomes. Interestingly, GPER has a destination that is uncommon among 7TMRs, as it accumulates in a perinuclear compartment. Like many 7TMRs (approximately one-third), GPER trafficking from the plasma membrane is constitutive (occurs in the absence of agonist). However, its route of intracellular trafficking is highly unusual, as 7TMRs typically recycle to the plasma membrane (e.g. β1AR) or are degraded in lysosomes (e.g. CXCR4). The accumulation of GPER in the perinuclear space and its possible significance for attenuating estrogen action via this newly recognized membrane estrogen receptor is discussed herein.
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Affiliation(s)
- Shi-Bin Cheng
- Division of Hematology & Oncology Rhode Island Hospital and Brown University School of Medicine Providence, RI 02903, USA
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Cheng SB, Quinn JA, Graeber CT, Filardo EJ. Down-modulation of the G-protein-coupled estrogen receptor, GPER, from the cell surface occurs via a trans-Golgi-proteasome pathway. J Biol Chem 2011; 286:22441-55. [PMID: 21540189 PMCID: PMC3121390 DOI: 10.1074/jbc.m111.224071] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/26/2011] [Indexed: 11/06/2022] Open
Abstract
GPER is a G(s)-coupled seven-transmembrane receptor that has been linked to specific estrogen binding and signaling activities that are manifested by plasma membrane-associated enzymes. However, in many cell types, GPER is predominately localized to the endoplasmic reticulum (ER), and only minor amounts of receptor are detectable at the cell surface, an observation that has caused controversy regarding its role as a plasma membrane estrogen receptor. Here, we show that GPER constitutively buds intracellularly into EEA-1+ endosomes from clathrin-coated pits. Nonvisual arrestins-2/-3 do not co-localize with GPER, and expression of arrestin-2 dominant-negative mutants lacking clathrin- or β-adaptin interaction sites fails to block GPER internalization suggesting that arrestins are not involved in GPER endocytosis. Like β1AR, which recycles to the plasma membrane, GPER co-traffics with transferrin+, Rab11+ recycling endosomes. However, endocytosed GPER does not recycle to the cell surface, but instead returns to the trans-Golgi network (TGN) and does not re-enter the ER. GPER is ubiquitinated at the cell surface, exhibits a short half-life (t½;) <1 h), and is protected from degradation by the proteasome inhibitor, MG132. Disruption of the TGN by brefeldin A induces the accumulation of endocytosed GPER in Rab11+ perinuclear endosomes and prevents GPER degradation. Our results provide an explanation as to why GPER is not readily detected on the cell surface in some cell types and further suggest that TGN serves as the checkpoint for degradation of endocytosed GPER.
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Affiliation(s)
- Shi-Bin Cheng
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Jeffrey A. Quinn
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Carl T. Graeber
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
| | - Edward J. Filardo
- From the Division of Hematology & Oncology, Rhode Island Hospital and Brown University, Providence, Rhode Island 02903
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Rab11 function in Trypanosoma brucei: identification of conserved and novel interaction partners. EUKARYOTIC CELL 2011; 10:1082-94. [PMID: 21642507 DOI: 10.1128/ec.05098-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Ras-like GTPase Rab11 is implicated in multiple aspects of intracellular transport, including maintenance of plasma membrane composition and cytokinesis. In metazoans, these functions are mediated in part via coiled-coil Rab11-interacting proteins (FIPs) acting as Rab11 effectors. Additional interaction between Rab11 and the exocyst subunit Sec15 connects Rab11 with exocytosis. We find that FIPs are metazoan specific, suggesting that other factors mediate Rab11 functions in nonmetazoans. We examined Rab11 interactions in Trypanosoma brucei, where endocytosis is well studied and the role of Rab11 in recycling well documented. TbSec15 and TbRab11 interact, demonstrating evolutionary conservation. By yeast two-hybrid screening, we identified additional Rab11 interaction partners. Tb927.5.1640 (designated RBP74) interacted with both Rab11 and Rab5. RBP74 shares a coiled-coil architecture with metazoan FIPs but is unrelated by sequence and appears to play a role in coordinating endocytosis and recycling. A second coiled-coil protein, Tb09.211.4830 (TbAZI1), orthologous to AZI1 in Homo sapiens, interacts exclusively with Rab11. AZI1 is restricted to taxa with motile cilia/flagella. These data suggest that Rab11 functions are mediated by evolutionarily conserved (i.e., AZI1 and Sec15) and potentially lineage-specific (RBP74) interactions essential for the integration of the endomembrane system.
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Abstract
Hundreds of G protein coupled receptor (GPCR) isotypes integrate and coordinate the function of individual cells mediating signaling between different organs in our bodies. As an aberration of the normal relationships that organize cells' coexistence, cancer has to deceive cell-cell communication in order to grow and spread. GPCRs play a critical role in this process. Despite the fact that GPCRs represent one of the most common drug targets, current medical practice includes only a few anticancer compounds directly acting on their signaling. Many approaches can be envisaged to target GPCRs involved in oncology. Beyond interfering with GPCRs signaling by using agonists or antagonists to prevent cell proliferation, favor apoptosis, induce maturation, prevent migration, etc., the high specificity of the interaction between the receptors and their ligands can be exploited to deliver toxins, antineoplastic drugs or isotopes to transformed cells. In this review we describe the strategies that are in use, or appear promising, to act directly on GPCRs in the fight against neoplastic transformation and tumor progression.
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Esseltine JL, Dale LB, Ferguson SSG. Rab GTPases bind at a common site within the angiotensin II type I receptor carboxyl-terminal tail: evidence that Rab4 regulates receptor phosphorylation, desensitization, and resensitization. Mol Pharmacol 2010; 79:175-84. [PMID: 20943774 DOI: 10.1124/mol.110.068379] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The human angiotensin II type 1 receptor (AT₁R) is a member of the G protein-coupled receptor (GPCR) superfamily and represents an important target for cardiovascular therapeutic intervention. Agonist-activation of the AT₁R induces β-arrestin-dependent endocytosis to early endosomes in which the receptor resides as a protein complex with the Rab GTPase Rab5. In the present study, we examined whether other Rab GTPases that regulate receptor trafficking through endosomal compartments also bind to the AT₁R. We find that Rab4, Rab7, and Rab11 all bind to the last 10 amino acid residues of the AT₁R carboxyl-terminal tail. Rab11 binds AT₁R more effectively than Rab5, whereas Rab4 binds less effectively than Rab5. Alanine scanning mutagenesis reveals that proline 354 and cysteine 355 contribute to Rab protein binding, and mutation of these residues does not affect G protein coupling. We find that the Rab GTPases each compete with one another for receptor binding and that although Rab4 interacts poorly with the AT₁R, it effectively displaces Rab11 from the receptor. In contrast, Rab11 overexpression does not prevent Rab4 binding to the AT₁R. Overexpression of wild-type Rab4, but not Rab11, facilitates AT₁R dephosphorylation, and a constitutively active Rab4-Q67L mutant reduces AT₁R desensitization and promotes AT₁R resensitization. Taken together, our data indicate that multiple Rab GTPases bind to a motif localized to the distal end of the AT₁R tail and that increased Rab4 activity may contribute to the regulation AT₁R desensitization and dephosphorylation.
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Affiliation(s)
- Jessica L Esseltine
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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43
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Gardner LA, Hajjhussein H, Frederick-Dyer KC, Bahouth SW. Rab11a and its binding partners regulate the recycling of the ß1-adrenergic receptor. Cell Signal 2010; 23:46-57. [PMID: 20727405 DOI: 10.1016/j.cellsig.2010.07.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 07/27/2010] [Accepted: 07/30/2010] [Indexed: 01/12/2023]
Abstract
ß1-adrenergic receptors (ß1-AR) are internalized in response to agonists and then recycle back for another round of signaling. The serine 312 to alanine mutant of the ß1-AR (S312A) is internalized but does not recycle. We determined that WT ß1-AR and S312A were internalized initially to an early sorting compartment because they colocalized by >70% with the early endosomal markers rab5a and early endosomal antigen-1 (EEA1). Subsequently, the WT ß1-AR trafficked via rab4a-expressing sorting endosomes to recycling endosomes. In recycling endosomes WT ß1-AR were colocalized by >70% with the rab11 GTPase. S312A did not colocalize with either rab4a or rab11, instead they exited from early endosomes to late endosomes/lysosomes in which they were degraded. Rab11a played a prominent role in recycling of the WT ß1-AR because dominant negative rab11a inhibited, while constitutively active rab11a accelerated the recycling of the ß1-AR. Next, we determined the effect of each of the rab11-interacting proteins on trafficking of the WT ß1-AR. The recycling of the ß1-AR was markedly inhibited when myosin Vb, FIP2, FIP3 and rabphillin were knocked down. These data indicate that rab11a and a select group of its binding partners play a prominent role in recycling of the human ß1-AR.
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Affiliation(s)
- Lidia A Gardner
- Department of Neurology, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA
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Nisar S, Kelly E, Cullen PJ, Mundell SJ. Regulation of P2Y1 receptor traffic by sorting Nexin 1 is retromer independent. Traffic 2010; 11:508-19. [PMID: 20070609 DOI: 10.1111/j.1600-0854.2010.01035.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The activity and traffic of G-protein coupled receptors (GPCRs) is tightly controlled. Recent work from our laboratory has shown that P2Y(1) and P2Y(12) responsiveness is rapidly and reversibly modulated in human platelets and that the underlying mechanism requires receptor trafficking as an essential part of this process. However, little is known about the molecular mechanisms underlying P2Y receptor traffic. Sorting nexin 1 (SNX1) has been shown to regulate the endosomal sorting of cell surface receptors either to lysosomes where they are downregulated or back to the cell surface. These functions may in part be due to interactions of SNX1 with the mammalian retromer complex. In this study, we investigated the role of SNX1 in P2Y receptor trafficking. We show that P2Y(1) receptors recycle via a slow recycling pathway that is regulated by SNX1, whereas P2Y(12) receptors return to the cell surface via a rapid route that is SNX1 independent. SNX1 inhibition caused a dramatic increase in the rate of P2Y(1) receptor recycling, whereas inhibition of Vps26 and Vps35 known to be present in retromer had no effect, indicating that SNX1 regulation of P2Y(1) receptor recycling is retromer independent. In addition, inhibition of SNX4, 6 and 17 proteins did not affect P2Y(1) receptor recycling. SNX1 has also been implicated in GPCR degradation; however, we provide evidence that P2Y receptor degradation is SNX1 independent. These data describe a novel function of SNX1 in the regulation of P2Y(1) receptor recycling and suggest that SNX1 plays multiple roles in endocytic trafficking of GPCRs.
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Affiliation(s)
- Shaista Nisar
- Department of Physiology and Pharmacology, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, UK
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45
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Hubbard CS, Dolence EK, Shires JA, Rose JD. Identification of brain target neurons using a fluorescent conjugate of corticotropin-releasing factor. J Chem Neuroanat 2009; 37:245-53. [PMID: 19481009 PMCID: PMC2732013 DOI: 10.1016/j.jchemneu.2009.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 01/18/2009] [Accepted: 01/24/2009] [Indexed: 11/23/2022]
Abstract
Corticotropin-releasing factor (CRF) is a peptide well known for its role in coordinating various neuroendocrine, autonomic, and behavioral components of the vertebrate stress response, including rapid enhancement of locomotor activity. Although CRF's locomotor enhancing properties are well documented, the neuronal mechanisms and specific target neurons that underlie the peptide's effect on locomotor behavior remain poorly understood. In the present study, we describe the synthesis and functional characteristics of a CRF rhodamine analogue TAMRA-X conjugate mixture (CRF-TAMRA 1), to be used for tracking this peptide's internalization into target neurons in the brainstem of an amphibian, the roughskin newt (Taricha granulosa). CRF-TAMRA 1 conjugate administration into the lateral cerebral ventricle resulted in a rapid, endosomal-like internalization of fluorescence into brainstem medullary neurons. In addition, central CRF-TAMRA 1 administration produced neurobehavioral effects comparable to the native peptide, effects that were blocked by pre-treatment with the CRF receptor antagonist, alpha-helical CRF. Taken together, our results show the efficacy of CRF-TAMRA 1 as a novel tool for tracking CRF internalization into targets neurons in vivo and ultimately, aiding in elucidating the neuronal mechanisms and circuitry underlying CRF's influence on behavioral and physiological responses to stress.
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Affiliation(s)
- Catherine S Hubbard
- Neuroscience Program, University of Wyoming, Laramie, WY 82071-3166, United States.
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46
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Jones BW, Hinkle PM. Subcellular trafficking of the TRH receptor: effect of phosphorylation. Mol Endocrinol 2009; 23:1466-78. [PMID: 19541745 DOI: 10.1210/me.2009-0119] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Activation of the G protein-coupled TRH receptor leads to its phosphorylation and internalization. These studies addressed the fundamental question of whether phosphorylation regulates receptor trafficking or endosomal localization regulates the phosphorylation state of the receptor. Trafficking of phosphorylated and dephosphorylated TRH receptors was characterized using phosphosite-specific antibody after labeling surface receptors with antibody to an extracellular epitope tag. Rab5 and phosphoreceptor did not colocalize at the plasma membrane immediately after TRH addition but overlapped extensively by 15 min. Dominant-negative Rab5-S34N inhibited receptor internalization. Later, phosphoreceptor was in endosomes containing Rab5 and Rab4. Dephosphorylated receptor colocalized with Rab4 but not with Rab5. Dominant-negative Rab4, -5, or -11 did not affect receptor phosphorylation or dephosphorylation, showing that phosphorylation determines localization in Rab4(+)/Rab5(-) vesicles and not vice versa. No receptor colocalized with Rab7; a small amount of phosphoreceptor colocalized with Rab11. To characterize recycling, surface receptors were tagged with antibody, or surface receptors containing an N-terminal biotin ligase acceptor sequence were labeled with biotin. Most recycling receptors did not return to the plasma membrane for more than 2 h after TRH was removed, whereas the total cell surface receptor density was largely restored in less than 1 h, indicating that recruited receptors contribute heavily to early repopulation of the plasma membrane.
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Affiliation(s)
- Brian W Jones
- Department of Pharmacology, University of Rochester Medical Center, Box 711, Rochester, New York 14642, USA
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Wagener BM, Marjon NA, Revankar CM, Prossnitz ER. Adaptor protein-2 interaction with arrestin regulates GPCR recycling and apoptosis. Traffic 2009; 10:1286-300. [PMID: 19602204 DOI: 10.1111/j.1600-0854.2009.00957.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
G protein-coupled receptors (GPCRs) are integral to cellular function in nearly all physiologic and many pathologic processes. GPCR signaling represents an intricate balance between receptor activation, inactivation (desensitization, internalization and degradation) and resensitization (recycling and de novo synthesis). Complex formation between phosphorylated GPCRs, arrestins and an ever-increasing number of effector molecules is known to regulate cellular function. Previous studies have demonstrated that, although N-formyl peptide receptor (FPR) internalization occurs in the absence of arrestins, FPR recycling is arrestin-dependent. Furthermore, FPR stimulation in the absence of arrestins leads to receptor accumulation in perinuclear endosomes and apoptosis. In this study, we show that the interaction of GPCR-bound arrestin with adaptor protein-2 (AP-2) is a critical anti-apoptotic event. In addition, AP-2 associates with the receptor-arrestin complex in perinuclear endosomes and is required for proper post-endocytic GPCR trafficking. Finally, we observed that depletion of endogenous AP-2 results in the initiation of apoptosis upon stimulation of multiple GPCRs, including P2Y purinergic receptors and CXCR2, but not CXCR4. We propose a model in which the abnormal accumulation of internalized GPCR-arrestin complexes in recycling endosomes, resulting from defective arrestin-AP-2 interactions, leads to the specific initiation of aberrant signaling pathways and apoptosis.
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Affiliation(s)
- Brant M Wagener
- Department of Cell Biology and Physiology and UNM Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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Tournaviti S, Pietro ES, Terjung S, Schafmeier T, Wegehingel S, Ritzerfeld J, Schulz J, Smith DF, Pepperkok R, Nickel W. Reversible phosphorylation as a molecular switch to regulate plasma membrane targeting of acylated SH4 domain proteins. Traffic 2009; 10:1047-60. [PMID: 19453972 DOI: 10.1111/j.1600-0854.2009.00921.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Acylated SH4 domains represent N-terminal targeting signals that anchor peripheral membrane proteins such as Src kinases in the inner leaflet of plasma membranes. Here we provide evidence for a novel regulatory mechanism that may control the levels of SH4 proteins being associated with plasma membranes. Using a fusion protein of the SH4 domain of Leishmania HASPB and GFP as a model system, we demonstrate that threonine 6 is a substrate for phosphorylation. Substitution of threonine 6 by glutamate (to mimic a phosphothreonine residue) resulted in a dramatic redistribution from plasma membranes to intracellular sites with a particular accumulation in a perinuclear region. As shown by both pharmacological inhibition and RNAi-mediated down-regulation of the threonine/ serine-specific phosphatases PP1 and PP2A, recycling back to the plasma membrane required dephosphorylation of threonine 6. We provide evidence that a cycle of phosphorylation and dephosphorylation may also be involved in intracellular targeting of other SH4 proteins such as the Src kinase Yes.
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Innamorati G, Giannone F, Guzzi F, Rovati GE, Accomazzo MR, Chini B, Bianchi E, Schiaffino MV, Tridente G, Parenti M. Heterotrimeric G proteins demonstrate differential sensitivity to beta-arrestin dependent desensitization. Cell Signal 2009; 21:1135-42. [PMID: 19275934 DOI: 10.1016/j.cellsig.2009.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 02/19/2009] [Accepted: 03/02/2009] [Indexed: 11/15/2022]
Abstract
G15 is a heterotrimeric G protein of the Gq/11 family. In this study, we describe its exceptional poor sensitivity to the general regulatory mechanism of G protein-coupled receptor (GPCR) desensitization. Enhancing beta2 adrenergic receptor desensitization by arrestin overexpression, did not affect signalling to G15. Similarly, increased levels of arrestin did not affect G15 signalling triggered by the activation of V2 vasopressin and delta opioid receptors. Furthermore, co-immunoprecipitation experiments showed that G15 alpha subunit (as opposed to Galphaq and Galphas) is recruited to a V2 vasopressin receptor mutant that is constitutively desensitized by beta-arrestin. Interestingly, co-expression of Galpha15 partially rescued cell surface localization and signalling capabilities of the same mutant receptor and reduced beta2 adrenergic receptor internalization. Taken together, these findings provide evidence for a novel mechanism whereby GPCR desensitization can be bypassed and G15 can support sustained signalling in cells chronically exposed to hormones or neurotransmitters.
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Affiliation(s)
- Giulio Innamorati
- Department of Pathology, Immunology Unit, University of Verona, c/o Policlinico G.B. Rossi, Piazzale L.A. Scuro 10, Verona, Italy.
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Conti F, Sertic S, Reversi A, Chini B. Intracellular trafficking of the human oxytocin receptor: evidence of receptor recycling via a Rab4/Rab5 "short cycle". Am J Physiol Endocrinol Metab 2009; 296:E532-42. [PMID: 19126785 DOI: 10.1152/ajpendo.90590.2008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
As in the case of most G protein-coupled receptors, agonist stimulation of human oxytocin receptors (OTRs) leads to desensitization and internalization; however, little is known about the subsequent intracellular OTR trafficking, which is crucial for reestablishing agonist responsiveness. We examined receptor resensitization by first using HEK293T cells stably expressing human OTRs. Upon agonist activation, the receptors were almost completely sequestered inside intracellular compartments that were not labeled by lysosomal markers, thus indicating that the internalized receptors were not sorted to these degrading organelles. Binding and fluorescence assays showed that almost 85% of the receptors had returned to the cell surface after 4 h, by which time cell responsiveness to the agonist was also completely restored, as shown by measuring phospholipase C activation. Similar results were also obtained in the presence of cycloheximide, thus indicating that receptor recycling and not de novo receptor synthesis was responsible for the resensitization. Notably, very similar internalization and recycling kinetics were observed in endogenous OTRs expressed on myometrial cells. We also investigated the role of beta-arrestin2 in OTR recycling as these receptors have been previously classified as slowly or nonrecycling receptors on the basis of their stable association with this interacting protein. Our data suggest that the stable OTR/beta-arrestin2 interaction plays an important role in determining the rate of recycling of human OTRs, but does not determine the fate of endocytosed receptors. Subsequent investigations of receptor recycling pathways showed that OTRs localize in vesicles containing the Rab5 and Rab4 small GTPases (markers of the "short cycle"), whereas there was no colocalization with Rab11 (a marker of the "long cycle") or Rab7 (a marker of vesicles directed to endosomal/lysosomal compartments). Taken together, these data indicate that OTRs are capable of very efficient and complete resensitization due to receptor recycling via the short cycle.
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Affiliation(s)
- Francesca Conti
- CNR Institute of Neuroscience, Via Vanvitelli 32, 20129 Milan, Italy
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