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Maaliki D, Jaffa AA, Nasser S, Sahebkar A, Eid AH. Adrenoceptor Desensitization: Current Understanding of Mechanisms. Pharmacol Rev 2024; 76:358-387. [PMID: 38697858 DOI: 10.1124/pharmrev.123.000831] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 01/15/2024] [Accepted: 01/18/2024] [Indexed: 05/05/2024] Open
Abstract
G-protein coupled receptors (GPCRs) transduce a wide range of extracellular signals. They are key players in the majority of biologic functions including vision, olfaction, chemotaxis, and immunity. However, as essential as most of them are to body function and homeostasis, overactivation of GPCRs has been implicated in many pathologic diseases such as cancer, asthma, and heart failure (HF). Therefore, an important feature of G protein signaling systems is the ability to control GPCR responsiveness, and one key process to control overstimulation involves initiating receptor desensitization. A number of steps are appreciated in the desensitization process, including cell surface receptor phosphorylation, internalization, and downregulation. Rapid or short-term desensitization occurs within minutes and involves receptor phosphorylation via the action of intracellular protein kinases, the binding of β-arrestins, and the consequent uncoupling of GPCRs from their cognate heterotrimeric G proteins. On the other hand, long-term desensitization occurs over hours to days and involves receptor downregulation or a decrease in cell surface receptor protein level. Of the proteins involved in this biologic phenomenon, β-arrestins play a particularly significant role in both short- and long-term desensitization mechanisms. In addition, β-arrestins are involved in the phenomenon of biased agonism, where the biased ligand preferentially activates one of several downstream signaling pathways, leading to altered cellular responses. In this context, this review discusses the different patterns of desensitization of the α 1-, α 2- and the β adrenoceptors and highlights the role of β-arrestins in regulating physiologic responsiveness through desensitization and biased agonism. SIGNIFICANCE STATEMENT: A sophisticated network of proteins orchestrates the molecular regulation of GPCR activity. Adrenoceptors are GPCRs that play vast roles in many physiological processes. Without tightly controlled desensitization of these receptors, homeostatic imbalance may ensue, thus precipitating various diseases. Here, we critically appraise the mechanisms implicated in adrenoceptor desensitization. A better understanding of these mechanisms helps identify new druggable targets within the GPCR desensitization machinery and opens exciting therapeutic fronts in the treatment of several pathologies.
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Affiliation(s)
- Dina Maaliki
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, Lebanon (D.M.); School of Medicine, University of South Carolina, Columbia, South Carolina (A.A.J.); Keele University, Staffordshire, United Kingdom (S.N.); Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); and Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar (A.H.E.)
| | - Aneese A Jaffa
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, Lebanon (D.M.); School of Medicine, University of South Carolina, Columbia, South Carolina (A.A.J.); Keele University, Staffordshire, United Kingdom (S.N.); Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); and Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar (A.H.E.)
| | - Suzanne Nasser
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, Lebanon (D.M.); School of Medicine, University of South Carolina, Columbia, South Carolina (A.A.J.); Keele University, Staffordshire, United Kingdom (S.N.); Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); and Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar (A.H.E.)
| | - Amirhossein Sahebkar
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, Lebanon (D.M.); School of Medicine, University of South Carolina, Columbia, South Carolina (A.A.J.); Keele University, Staffordshire, United Kingdom (S.N.); Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); and Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar (A.H.E.)
| | - Ali H Eid
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, Lebanon (D.M.); School of Medicine, University of South Carolina, Columbia, South Carolina (A.A.J.); Keele University, Staffordshire, United Kingdom (S.N.); Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran (A.S.); and Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar (A.H.E.)
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Girard M, Bellefeuille SD, Eiselt É, Arguin G, Longpré JM, Sarret P, Gendron FP. Ligand-dependent intracellular trafficking of the G protein-coupled P2Y 6 receptor. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119476. [PMID: 37059189 DOI: 10.1016/j.bbamcr.2023.119476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 03/28/2023] [Accepted: 04/05/2023] [Indexed: 04/16/2023]
Abstract
Endosomal trafficking is intricately linked to G protein-coupled receptors (GPCR) fate and signaling. Extracellular uridine diphosphate (UDP) acts as a signaling molecule by selectively activating the GPCR P2Y6. Despite the recent interest for this receptor in pathologies, such as gastrointestinal and neurological diseases, there is sparse information on the endosomal trafficking of P2Y6 receptors in response to its endogenous agonist UDP and synthetic selective agonist 5-iodo-UDP (MRS2693). Confocal microscopy and cell surface ELISA revealed delayed internalization kinetics in response to MRS2693 vs. UDP stimulation in AD293 and HCT116 cells expressing human P2Y6. Interestingly, UDP induced clathrin-dependent P2Y6 internalization, whereas receptor stimulation by MRS2693 endocytosis appeared to be associated with a caveolin-dependent mechanism. Internalized P2Y6 was associated with Rab4, 5, and 7 positive vesicles independent of the agonist. We have measured a higher frequency of receptor expression co-occurrence with Rab11-vesicles, the trans-Golgi network, and lysosomes in response to MRS2693. Interestingly, a higher agonist concentration reversed the delayed P2Y6 internalization and recycling kinetics in the presence of MRS2693 stimulation without changing its caveolin-dependent internalization. This work showed a ligand-dependent effect affecting the P2Y6 receptor internalization and endosomal trafficking. These findings could guide the development of bias ligands that could influence P2Y6 signaling.
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Affiliation(s)
- Mélissa Girard
- Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada; Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Canada
| | - Steve Dagenais Bellefeuille
- Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Émilie Eiselt
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Canada; Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Canada
| | - Guillaume Arguin
- Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Jean-Michel Longpré
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Canada; Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Canada
| | - Philippe Sarret
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Canada; Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Canada
| | - Fernand-Pierre Gendron
- Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada; Institut de Pharmacologie de Sherbrooke, Université de Sherbrooke, Canada.
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Mavri M, Glišić S, Senćanski M, Vrecl M, Rosenkilde MM, Spiess K, Kubale V. Patterns of human and porcine gammaherpesvirus-encoded BILF1 receptor endocytosis. Cell Mol Biol Lett 2023; 28:14. [PMID: 36810008 PMCID: PMC9942385 DOI: 10.1186/s11658-023-00427-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/30/2023] [Indexed: 02/23/2023] Open
Abstract
BACKGROUND The viral G-protein-coupled receptor (vGPCR) BILF1 encoded by the Epstein-Barr virus (EBV) is an oncogene and immunoevasin and can downregulate MHC-I molecules at the surface of infected cells. MHC-I downregulation, which presumably occurs through co-internalization with EBV-BILF1, is preserved among BILF1 receptors, including the three BILF1 orthologs encoded by porcine lymphotropic herpesviruses (PLHV BILFs). This study aimed to understand the detailed mechanisms of BILF1 receptor constitutive internalization, to explore the translational potential of PLHV BILFs compared with EBV-BILF1. METHODS A novel real-time fluorescence resonance energy transfer (FRET)-based internalization assay combined with dominant-negative variants of dynamin-1 (Dyn K44A) and the chemical clathrin inhibitor Pitstop2 in HEK-293A cells was used to study the effect of specific endocytic proteins on BILF1 internalization. Bioluminescence resonance energy transfer (BRET)-saturation analysis was used to study BILF1 receptor interaction with β-arrestin2 and Rab7. In addition, a bioinformatics approach informational spectrum method (ISM) was used to investigate the interaction affinity of BILF1 receptors with β-arrestin2, AP-2, and caveolin-1. RESULTS We identified dynamin-dependent, clathrin-mediated constitutive endocytosis for all BILF1 receptors. The observed interaction affinity between BILF1 receptors and caveolin-1 and the decreased internalization in the presence of a dominant-negative variant of caveolin-1 (Cav S80E) indicated the involvement of caveolin-1 in BILF1 trafficking. Furthermore, after BILF1 internalization from the plasma membrane, both the recycling and degradation pathways are proposed for BILF1 receptors. CONCLUSIONS The similarity in the internalization mechanisms observed for EBV-BILF1 and PLHV1-2 BILF1 provide a foundation for further studies exploring a possible translational potential for PLHVs, as proposed previously, and provides new information about receptor trafficking.
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Affiliation(s)
- Maša Mavri
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia
| | - Sanja Glišić
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Milan Senćanski
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Milka Vrecl
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia
| | - Mette M Rosenkilde
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Katja Spiess
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Virus and Microbiological Special Diagnostics, Statens Serum Institute, Copenhagen, Denmark
| | - Valentina Kubale
- Institute for preclinical sciences, Veterinary Faculty, Ljubljana, Slovenia.
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Yadav P, Podia M, Kumari SP, Mani I. Glutamate receptor endocytosis and signaling in neurological conditions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 196:167-207. [PMID: 36813358 DOI: 10.1016/bs.pmbts.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The non-essential amino acid glutamate acts as a major excitatory neurotransmitter and plays a significant role in the central nervous system (CNS). It binds with two different types of receptors, ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs), responsible for the postsynaptic excitation of neurons. They are important for memory, neural development and communication, and learning. Endocytosis and subcellular trafficking of the receptor are essential for the regulation of receptor expression on the cell membrane and excitation of the cells. The endocytosis and trafficking of the receptor are dependent on its type, ligand, agonist, and antagonist present. This chapter discusses the types of glutamate receptors, their subtypes, and the regulation of their internalization and trafficking. The roles of glutamate receptors in neurological diseases are also briefly discussed.
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Affiliation(s)
- Prerna Yadav
- Department of Microbiology, University of Delhi, New Delhi, India
| | - Mansi Podia
- Department of Microbiology, University of Delhi, New Delhi, India
| | - Shashi Prabha Kumari
- Department of Microbiology, Ram Lal Anand College, University of Delhi, New Delhi, India
| | - Indra Mani
- Department of Microbiology, Gargi College, University of Delhi, New Delhi, India.
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Differential Involvement of ACKR3 C-Tail in β-Arrestin Recruitment, Trafficking and Internalization. Cells 2021; 10:cells10030618. [PMID: 33799570 PMCID: PMC8002179 DOI: 10.3390/cells10030618] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/05/2021] [Accepted: 03/08/2021] [Indexed: 12/12/2022] Open
Abstract
Background: The atypical chemokine receptor 3 (ACKR3) belongs to the superfamily of G protein-coupled receptors (GPCRs). Unlike classical GPCRs, this receptor does not activate G proteins in most cell types but recruits β-arrestins upon activation. ACKR3 plays an important role in cancer and vascular diseases. As recruitment of β-arrestins is triggered by phosphorylation of the C-terminal tail of GPCRs, we studied the role of different potential phosphorylation sites within the ACKR3 C-tail to further delineate the molecular mechanism of internalization and trafficking of this GPCR. Methods: We used various bioluminescence and fluorescence resonance energy transfer-based sensors and techniques in Human Embryonic Kidney (HEK) 293T cells expressing WT or phosphorylation site mutants of ACKR3 to measure CXCL12-induced recruitment of β-arrestins and G-protein-coupled receptor kinases (GRKs), receptor internalization and trafficking. Results: Upon CXCL12 stimulation, ACKR3 recruits both β-arrestin 1 and 2 with equivalent kinetic profiles. We identified interactions with GRK2, 3 and 5, with GRK2 and 3 being important for β-arrestin recruitment. Upon activation, ACKR3 internalizes and recycles back to the cell membrane. We demonstrate that β-arrestin recruitment to the receptor is mainly determined by a single cluster of phosphorylated residues on the C-tail of ACKR3, and that residue T352 and in part S355 are important residues for β-arrestin1 recruitment. Phosphorylation of the C-tail appears essential for ligand-induced internalization and important for differential β-arrestin recruitment. GRK2 and 3 play a key role in receptor internalization. Moreover, ACKR3 can still internalize when β-arrestin recruitment is impaired or in the absence of β-arrestins, using alternative internalization pathways. Our data indicate that distinct residues within the C-tail of ACKR3 differentially regulate CXCL12-induced β-arrestin recruitment, ACKR3 trafficking and internalization.
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Moo EV, van Senten JR, Bräuner-Osborne H, Møller TC. Arrestin-Dependent and -Independent Internalization of G Protein-Coupled Receptors: Methods, Mechanisms, and Implications on Cell Signaling. Mol Pharmacol 2021; 99:242-255. [PMID: 33472843 DOI: 10.1124/molpharm.120.000192] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 01/07/2021] [Indexed: 01/05/2023] Open
Abstract
Agonist-induced endocytosis is a key regulatory mechanism for controlling the responsiveness of the cell by changing the density of cell surface receptors. In addition to the role of endocytosis in signal termination, endocytosed G protein-coupled receptors (GPCRs) have been found to signal from intracellular compartments of the cell. Arrestins are generally believed to be the master regulators of GPCR endocytosis by binding to both phosphorylated receptors and adaptor protein 2 (AP-2) or clathrin, thus recruiting receptors to clathrin-coated pits to facilitate the internalization process. However, many other functions have been described for arrestins that do not relate to their role in terminating signaling. Additionally, there are now more than 30 examples of GPCRs that internalize independently of arrestins. Here we review the methods, pharmacological tools, and cellular backgrounds used to determine the role of arrestins in receptor internalization, highlighting their advantages and caveats. We also summarize key examples of arrestin-independent GPCR endocytosis in the literature and their suggested alternative endocytosis pathway (e.g., the caveolae-dependent and fast endophilin-mediated endocytosis pathways). Finally, we consider the possible function of arrestins recruited to GPCRs that are endocytosed independently of arrestins, including the catalytic arrestin activation paradigm. Technological improvements in recent years have advanced the field further, and, combined with the important implications of endocytosis on drug responses, this makes endocytosis an obvious parameter to include in molecular pharmacological characterization of ligand-GPCR interactions. SIGNIFICANCE STATEMENT: G protein-coupled receptor (GPCR) endocytosis is an important means to terminate receptor signaling, and arrestins play a central role in the widely accepted classical paradigm of GPCR endocytosis. In contrast to the canonical arrestin-mediated internalization, an increasing number of GPCRs are found to be endocytosed via alternate pathways, and the process appears more diverse than the previously defined "one pathway fits all."
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Affiliation(s)
- Ee Von Moo
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Jeffrey R van Senten
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Thor C Møller
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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Olesen CW, Vogensen J, Axholm I, Severin M, Schnipper J, Pedersen IS, von Stemann JH, Schrøder JM, Christensen DP, Pedersen SF. Trafficking, localization and degradation of the Na +,HCO 3- co-transporter NBCn1 in kidney and breast epithelial cells. Sci Rep 2018; 8:7435. [PMID: 29743600 PMCID: PMC5943355 DOI: 10.1038/s41598-018-25059-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 04/13/2018] [Indexed: 01/28/2023] Open
Abstract
The Na+;HCO3− co-transporter NBCn1 (SLC4A7) is a major regulator of intracellular pH yet its trafficking and turnover are essentially unstudied. Here, we used MDCK-II and MCF-7 cells to investigate these processes in epithelial cells. GFP-NBCn1 membrane localization was abolished by truncation of the full NBCn1 C-terminal tail (C-tail) yet did not require the C-terminal PDZ-binding motif (ETSL). Glutathione-S-Transferase-pulldown of the C-tail followed by mass spectrometry analysis revealed putative interactions with multiple sorting-, degradation- and retention factors, including the scaffolding protein RACK1. Pulldown of FLAG-tagged deletion constructs mapped the RACK1 interaction to the proximal NBCn1 C-tail. Proximity Ligation Assay and co-immunoprecipitation confirmed that native NBCn1 interacts with RACK1 in a cellular context. Consistent with a functional role of this complex, RACK1 knockdown reduced NBCn1 membrane localization without affecting total NBCn1 expression. Notably, only non-confluent cells exhibited detectable NBCn1-RACK1 plasma membrane co-localization, suggesting that RACK1 regulates the trafficking of NBCn1 to the membrane. Whereas total NBCn1 degradation was slow, with a half-life of more than 24 h, one-third of surface NBCn1 was constitutively endocytosed from the basolateral membrane within 60 min. This suggests that a fraction of NBCn1 exhibits recycling between the basolateral membrane and intracellular compartment(s). Our findings have important implications for understanding NBCn1 regulation as well as its dysregulation in disease.
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Affiliation(s)
- Christina Wilkens Olesen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Jens Vogensen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Ida Axholm
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Marc Severin
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Julie Schnipper
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Isabella Skandorff Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Jakob Hjorth von Stemann
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Jacob Morville Schrøder
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark
| | - Dan Ploug Christensen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark.
| | - Stine Falsig Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark.
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Foster SR, Bräuner-Osborne H. Investigating Internalization and Intracellular Trafficking of GPCRs: New Techniques and Real-Time Experimental Approaches. Handb Exp Pharmacol 2017; 245:41-61. [PMID: 29018878 DOI: 10.1007/164_2017_57] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The ability to regulate the interaction between cells and their extracellular environment is essential for the maintenance of appropriate physiological function. For G protein-coupled receptors (GPCRs), this regulation occurs through multiple mechanisms that provide spatial and temporal control for signal transduction. One of the major mechanisms for GPCR regulation involves their endocytic trafficking, which serves to internalize the receptors from the plasma membrane and thereby attenuate G protein-dependent signaling. However, there is accumulating evidence to suggest that GPCRs can signal independently of G proteins, as well as from intracellular compartments including endosomes. It is in this context that receptor internalization and intracellular trafficking have attracted renewed interest within the GPCR field. In this chapter, we will review the current understanding and methodologies that have been used to investigate internalization and intracellular signaling of GPCRs, with a particular focus on emerging real-time techniques. These recent developments have improved our understanding of the complexities of GPCR internalization and intracellular signaling and suggest that the broader biological relevance and potential therapeutic implications of these processes remain to be explored.
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Affiliation(s)
- Simon R Foster
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
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Vreja IC, Nikić I, Göttfert F, Bates M, Kröhnert K, Outeiro TF, Hell SW, Lemke EA, Rizzoli SO. Super-resolution Microscopy of Clickable Amino Acids Reveals the Effects of Fluorescent Protein Tagging on Protein Assemblies. ACS NANO 2015; 9:11034-11041. [PMID: 26498474 DOI: 10.1021/acsnano.5b04434] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The advent of super-resolution microscopy (nanoscopy) has set high standards for fluorescence tagging. Fluorescent proteins (FPs) are convenient tags in conventional imaging, but their use in nanoscopy has been questioned due to their relatively large size and propensity to form multimers. Here, we compared the nanoscale organization of proteins with or without FP tags by introducing the unnatural amino acid propargyl-L-lysine (PRK) in 26 proteins known to form multimolecular arrangements and into their FP-tagged variants. We revealed the proteins by coupling synthetic fluorophores to PRK via click chemistry and visualized them using ground-state depletion microscopy followed by individual molecule return, as well as stimulated emission depletion microscopy. The arrangements formed by the FP-tagged and nontagged proteins were similar. Mild, but statistically significant differences were observed for only six proteins (23% of all proteins tested). This suggests that FP-based nanoscopy is generally reliable. Unnatural amino acids should be a reliable alternative for the few proteins that are sensitive to FP tagging.
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Affiliation(s)
- Ingrid C Vreja
- International Max Planck Research School for Molecular Biology , Göttingen, Germany
| | - Ivana Nikić
- Structural and Computational Biology Unit, EMBL , 69117 Heidelberg, Germany
| | - Fabian Göttfert
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry , 37077 Göttingen, Germany
| | - Mark Bates
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry , 37077 Göttingen, Germany
| | | | | | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry , 37077 Göttingen, Germany
| | - Edward A Lemke
- Structural and Computational Biology Unit, EMBL , 69117 Heidelberg, Germany
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de Munnik SM, Smit MJ, Leurs R, Vischer HF. Modulation of cellular signaling by herpesvirus-encoded G protein-coupled receptors. Front Pharmacol 2015; 6:40. [PMID: 25805993 PMCID: PMC4353375 DOI: 10.3389/fphar.2015.00040] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/12/2015] [Indexed: 12/22/2022] Open
Abstract
Human herpesviruses (HHVs) are widespread infectious pathogens that have been associated with proliferative and inflammatory diseases. During viral evolution, HHVs have pirated genes encoding viral G protein-coupled receptors (vGPCRs), which are expressed on infected host cells. These vGPCRs show highest homology to human chemokine receptors, which play a key role in the immune system. Importantly, vGPCRs have acquired unique properties such as constitutive activity and the ability to bind a broad range of human chemokines. This allows vGPCRs to hijack human proteins and modulate cellular signaling for the benefit of the virus, ultimately resulting in immune evasion and viral dissemination to establish a widespread and lifelong infection. Knowledge on the mechanisms by which herpesviruses reprogram cellular signaling might provide insight in the contribution of vGPCRs to viral survival and herpesvirus-associated pathologies.
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Affiliation(s)
- Sabrina M de Munnik
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Martine J Smit
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Rob Leurs
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
| | - Henry F Vischer
- Amsterdam Institute for Molecules Medicines and Systems - Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, Amsterdam Netherlands
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11
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Clayton CC, Donthamsetti P, Lambert NA, Javitch JA, Neve KA. Mutation of three residues in the third intracellular loop of the dopamine D2 receptor creates an internalization-defective receptor. J Biol Chem 2014; 289:33663-75. [PMID: 25336643 DOI: 10.1074/jbc.m114.605378] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Arrestins mediate desensitization and internalization of G protein-coupled receptors and also direct receptor signaling toward heterotrimeric G protein-independent signaling pathways. We previously identified a four-residue segment (residues 212-215) of the dopamine D2 receptor that is necessary for arrestin binding in an in vitro heterologous expression system but that also impairs receptor expression. We now describe the characterization of additional mutations at that arrestin binding site in the third intracellular loop. Mutating two (residues 214 and 215) or three (residues 213-215) of the four residues to alanine partially decreased agonist-induced recruitment of arrestin3 without altering activation of a G protein. Arrestin-dependent receptor internalization, which requires arrestin binding to β2-adaptin (the β2 subunit of the clathrin-associated adaptor protein AP2) and clathrin, was disproportionately affected by the three-residue mutation, with no agonist-induced internalization observed even in the presence of overexpressed arrestin or G protein-coupled receptor kinase 2. The disjunction between arrestin recruitment and internalization could not be explained by alterations in the time course of the receptor-arrestin interaction, the recruitment of G protein-coupled receptor kinase 2, or the receptor-induced interaction between arrestin and β2-adaptin, suggesting that the mutation impairs a property of the internalization complex that has not yet been identified.
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Affiliation(s)
- Cecilea C Clayton
- the Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239
| | - Prashant Donthamsetti
- the Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, the Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, and
| | - Nevin A Lambert
- the Department of Pharmacology and Toxicology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia 30912
| | - Jonathan A Javitch
- the Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, the Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, and
| | - Kim A Neve
- the Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239, From the Research Service, Department of Veterans Affairs Medical Center, Portland, Oregon 97239,
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12
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Arg347Cys polymorphism of α1a-adrenergic receptor in vasovagal syncope. Case–control study in a Mexican population. Auton Neurosci 2014; 183:66-71. [DOI: 10.1016/j.autneu.2014.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 12/26/2013] [Accepted: 01/13/2014] [Indexed: 01/10/2023]
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13
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Segura V, Pérez-Aso M, Montó F, Carceller E, Noguera MA, Pediani J, Milligan G, McGrath IC, D’Ocon P. Differences in the signaling pathways of α(1A)- and α(1B)-adrenoceptors are related to different endosomal targeting. PLoS One 2013; 8:e64996. [PMID: 23717684 PMCID: PMC3663791 DOI: 10.1371/journal.pone.0064996] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 04/20/2013] [Indexed: 01/14/2023] Open
Abstract
AIMS To compare the constitutive and agonist-dependent endosomal trafficking of α(1A)- and α(1B)-adrenoceptors (ARs) and to establish if the internalization pattern determines the signaling pathways of each subtype. METHODS Using CypHer5 technology and VSV-G epitope tagged α(1A)- and α(1B)-ARs stably and transiently expressed in HEK 293 cells, we analyzed by confocal microscopy the constitutive and agonist-induced internalization of each subtype, and the temporal relationship between agonist induced internalization and the increase in intracellular calcium (determined by FLUO-3 flouorescence), or the phosphorylation of ERK1/2 and p38 MAP kinases (determined by Western blot). RESULTS AND CONCLUSIONS Constitutive as well as agonist-induced trafficking of α(1A) and α(1B) ARs maintain two different endosomal pools of receptors: one located close to the plasma membrane and the other deeper into the cytosol. Each subtype exhibited specific characteristics of internalization and distribution between these pools that determines their signaling pathways: α(1A)-ARs, when located in the plasma membrane, signal through calcium and ERK1/2 pathways but, when translocated to deeper endosomes, through a mechanism sensitive to β-arrestin and concanavalin A, continue signaling through ERK1/2 and also activate the p38 pathway. α(1B)-ARs signal through calcium and ERK1/2 only when located in the membrane and the signals disappear after endocytosis and by disruption of the membrane lipid rafts by methyl-β-cyclodextrin.
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Affiliation(s)
- Vanessa Segura
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Miguel Pérez-Aso
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Fermí Montó
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - Elena Carceller
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - María Antonia Noguera
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
| | - John Pediani
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences. University of Glasgow, Glasgow, United Kingdom
- Autonomic Physiology Unit, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Graeme Milligan
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences. University of Glasgow, Glasgow, United Kingdom
| | - Ian Christie McGrath
- Autonomic Physiology Unit, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Pilar D’Ocon
- Departamento de Farmacología, Facultad de Farmacia, Universitat de València, Valencia, Spain
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14
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Marcello E, Saraceno C, Musardo S, Vara H, de la Fuente AG, Pelucchi S, Di Marino D, Borroni B, Tramontano A, Pérez-Otaño I, Padovani A, Giustetto M, Gardoni F, Di Luca M. Endocytosis of synaptic ADAM10 in neuronal plasticity and Alzheimer's disease. J Clin Invest 2013; 123:2523-38. [PMID: 23676497 DOI: 10.1172/jci65401] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 03/05/2013] [Indexed: 12/19/2022] Open
Abstract
A disintegrin and metalloproteinase 10 (ADAM10), a disintegrin and metalloproteinase that resides in the postsynaptic densities (PSDs) of excitatory synapses, has previously been shown to limit β-amyloid peptide (Aβ) formation in Alzheimer's disease (AD). ADAM10 also plays a critical role in regulating functional membrane proteins at the synapse. Using human hippocampal homogenates, we found that ADAM10 removal from the plasma membrane was mediated by clathrin-dependent endocytosis. Additionally, we identified the clathrin adaptor AP2 as an interacting partner of a previously uncharacterized atypical binding motif in the ADAM10 C-terminal domain. This domain was required for ADAM10 endocytosis and modulation of its plasma membrane levels. We found that the ADAM10/AP2 association was increased in the hippocampi of AD patients compared with healthy controls. Long-term potentiation (LTP) in hippocampal neuronal cultures induced ADAM10 endocytosis through AP2 association and decreased surface ADAM10 levels and activity. Conversely, long-term depression (LTD) promoted ADAM10 synaptic membrane insertion and stimulated its activity. ADAM10 interaction with the synapse-associated protein-97 (SAP97) was necessary for LTD-induced ADAM10 trafficking and required for LTD maintenance and LTD-induced changes in spine morphogenesis. These data identify and characterize a mechanism controlling ADAM10 localization and activity at excitatory synapses that is relevant to AD pathogenesis.
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Affiliation(s)
- Elena Marcello
- Università degli Studi di Milano, Dipartimento di Scienze Farmacologiche e Biomolecolari and Centre of Excellence on Neurodegenerative Diseases, Milan, Italy
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15
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Cunningham MR, Nisar SP, Cooke AE, Emery ED, Mundell SJ. Differential endosomal sorting of a novel P2Y12 purinoreceptor mutant. Traffic 2013; 14:585-98. [PMID: 23387322 DOI: 10.1111/tra.12054] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 01/30/2013] [Accepted: 02/06/2013] [Indexed: 12/11/2022]
Abstract
P2Y12 receptor internalization and recycling play an essential role in ADP-induced platelet activation. Recently, we identified a patient with a mild bleeding disorder carrying a heterozygous mutation of P2Y12 (P341A) whose P2Y12 receptor recycling was significantly compromised. Using human cell line models, we identified key proteins regulating wild-type (WT) P2Y12 recycling and investigated P2Y12 -P341A receptor traffic. Treatment with ADP resulted in delayed Rab5-dependent internalization of P341A when compared with WT P2Y12 . While WT P2Y12 rapidly recycled back to the membrane via Rab4 and Rab11 recycling pathways, limited P341A recycling was observed, which relied upon Rab11 activity. Although minimal receptor degradation was evident, P341A was localized in Rab7-positive endosomes with considerable agonist-dependent accumulation in the trans-Golgi network (TGN). Rab7 activity is known to facilitate recruitment of retromer complex proteins to endosomes to transport cargo to the TGN. Here, we identified that P341A colocalized with Vps26; depletion of which blocked limited recycling and promoted receptor degradation. This study has identified key points of divergence in the endocytic traffic of P341A versus WT-P2Y12 . Given that these pathways are retained in human platelets, this research helps define the molecular mechanisms regulating P2Y12 receptor traffic and explain the compromised receptor function in the platelets of the P2Y12 -P341A-expressing patient.
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Affiliation(s)
- Margaret R Cunningham
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK
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16
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Cotecchia S, Stanasila L, Diviani D. Protein-protein interactions at the adrenergic receptors. Curr Drug Targets 2012; 13:15-27. [PMID: 21777184 PMCID: PMC3290771 DOI: 10.2174/138945012798868489] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 02/12/2011] [Accepted: 02/16/2011] [Indexed: 01/07/2023]
Abstract
The adrenergic receptors are among the best characterized G protein-coupled receptors (GPCRs) and knowledge on this receptor family has provided several important paradigms about GPCR function and regulation. One of the most recent paradigms initially supported by studies on adrenergic receptors is that both βarrestins and G protein-coupled receptors themselves can act as scaffolds binding a variety of proteins and this can result in growing complexity of the receptor-mediated cellular effects. In this review we will briefly summarize the main features of βarrestin binding to the adrenergic receptor subtypes and we will review more in detail the main proteins found to selectively interact with distinct AR subtype. At the end, we will review the main findings on oligomerization of the AR subtypes.
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Affiliation(s)
- Susanna Cotecchia
- Départment de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland.
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17
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Stabilization of GABA(A) receptors at endocytic zones is mediated by an AP2 binding motif within the GABA(A) receptor β3 subunit. J Neurosci 2012; 32:2485-98. [PMID: 22396422 DOI: 10.1523/jneurosci.1622-11.2011] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The strength of synaptic inhibition can be controlled by the stability and endocytosis of surface and synaptic GABA(A) receptors (GABA(A)Rs), but the surface receptor dynamics that underpin GABA(A)R recruitment to dendritic endocytic zones (EZs) have not been investigated. Stabilization of GABA(A)Rs at EZs is likely to be regulated by receptor interactions with the clathrin-adaptor AP2, but the molecular determinants of these associations remain poorly understood. Moreover, although surface GABA(A)R downmodulation plays a key role in pathological disinhibition in conditions such as ischemia and epilepsy, whether this occurs in an AP2-dependent manner also remains unclear. Here we report the characterization of a novel motif containing three arginine residues (405RRR407) within the GABA(A)R β3-subunit intracellular domain (ICD), responsible for the interaction with AP2 and GABA(A)R internalization. When this motif is disrupted, binding to AP2 is abolished in vitro and in rat brain. Using single-particle tracking, we reveal that surface β3-subunit-containing GABA(A)Rs exhibit highly confined behavior at EZs, which is dependent on AP2 interactions via this motif. Reduced stabilization of mutant GABA(A)Rs at EZs correlates with their reduced endocytosis and increased steady-state levels at synapses. By imaging wild-type or mutant super-ecliptic pHluorin-tagged GABA(A)Rs in neurons, we also show that, under conditions of oxygen-glucose deprivation to mimic cerebral ischemia, GABA(A)Rs are depleted from synapses in dendrites, depending on the 405RRR407 motif. Thus, AP2 binding to an RRR motif in the GABA(A)R β3-subunit ICD regulates GABA(A)R residency time at EZs, steady-state synaptic receptor levels, and pathological loss of GABA(A)Rs from synapses during simulated ischemia.
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18
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Identification of a pivotal endocytosis motif in c-Met and selective modulation of HGF-dependent aggressiveness of cancer using the 16-mer endocytic peptide. Oncogene 2012; 32:1018-29. [PMID: 22525273 DOI: 10.1038/onc.2012.122] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Since c-Met has an important role in the development of cancer, it is considered as an attractive target for cancer therapy. Although molecular mechanisms for oncogenic property of c-Met have been actively investigated, regulatory elements for c-Met endocytosis and its effect on c-Met signaling remain unclear. In this study, we identified a pivotal endocytic motif in c-Met and tested it for selective modulation of HGF-induced c-Met response. Using various chimeric constructs with the cytoplasmic tail of c-Met, we were able to demonstrate that a dileucine motif located in the C-terminus of c-Met acts to regulate its endocytosis. Synthetic peptide Ant-3S, consisting of antennapedia-derived protein transduction domain (designated as Ant) and c-Met-derived 16 amino-acids (designated as 3S, spanning amino-acids 1378 to 1393), rapidly moved into cancer cells and disrupted c-Met trafficking. Importantly, an extension of c-Met retention time on the membrane by Ant-3S peptide significantly decreased phosphorylation-dependent c-Met signal transduction. Additionally, the peptide effectively inhibited HGF-induced cell growth, scattering and migration. The underlying molecular mechanism for these observations has been investigated and revealed that the dileucine motif interacts with endocytic machinery, including adaptin β and caveolin-1, for sustained and enhanced signal transduction. Finally, Ant-3S peptide specifically blocked internalization of interleukin-2 receptor α-subunit/3S chimeric protein, but not the other receptors, including Glut4, Glut8 and transferrin receptor. Such results indicate the presence of a selective endocytic assembly for c-Met. It also suggests a potential for c-Met-specific anti-cancer therapy using the identified endocytic motif in this study.
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19
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Damian M, Marie J, Leyris JP, Fehrentz JA, Verdié P, Martinez J, Banères JL, Mary S. High constitutive activity is an intrinsic feature of ghrelin receptor protein: a study with a functional monomeric GHS-R1a receptor reconstituted in lipid discs. J Biol Chem 2011; 287:3630-41. [PMID: 22117076 DOI: 10.1074/jbc.m111.288324] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Despite its central role in signaling and the potential therapeutic applications of inverse agonists, the molecular mechanisms underlying G protein-coupled receptor (GPCR) constitutive activity remain largely to be explored. In this context, ghrelin receptor GHS-R1a is a peculiar receptor in the sense that it displays a strikingly high, physiologically relevant, constitutive activity. To identify the molecular mechanisms responsible for this high constitutive activity, we have reconstituted a purified GHS-R1a monomer in a lipid disc. Using this reconstituted system, we show that the isolated ghrelin receptor per se activates G(q) in the absence of agonist, as assessed through guanosine 5'-O-(thiotriphosphate) binding experiments. The measured constitutive activity is similar in its extent to that observed in heterologous systems and in vivo. This is the first direct evidence for the high constitutive activity of the ghrelin receptor being an intrinsic property of the protein rather than the result of influence of its cellular environment. Moreover, we show that the isolated receptor in lipid discs recruits arrestin-2 in an agonist-dependent manner, whereas it interacts with μ-AP2 in the absence of ligand or in the presence of ghrelin. Of importance, these differences are linked to ligand-specific GHS-R1a conformations, as assessed by intrinsic fluorescence measurements. The distinct ligand requirements for the interaction of purified GHS-R1a with arrestin and AP2 provide a new rationale to the differences in basal and agonist-induced internalization observed in cells.
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Affiliation(s)
- Marjorie Damian
- Institut des Biomolécules Max Mousseron, CNRS UMR 5247, Université de Montpellier 1, Faculté de Pharmacie, 15 avenue Charles Flahaut, BP 14491, 34093 Montpellier cedex 5, France
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20
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An intact PDZ motif is essential for correct P2Y12 purinoceptor traffic in human platelets. Blood 2011; 118:5641-51. [PMID: 21937696 DOI: 10.1182/blood-2011-02-336826] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The platelet P2Y(12) purinoceptor (P2Y(12)R), which plays a crucial role in hemostasis, undergoes internalization and subsequent recycling to maintain receptor responsiveness, processes that are essential for normal platelet function. Here, we observe that P2Y(12)R function is compromised after deletion or mutation of the 4 amino acids at the extreme C-terminus of this receptor (ETPM), a putative postsynaptic density 95/disc large/zonula occludens-1 (PDZ)-binding motif. In cell line models, removal of this sequence or mutation of one of its core residues (P341A), attenuates receptor internalization and receptor recycling back to the membrane, thereby blocking receptor resensitization. The physiologic significance of these findings in the regulation of platelet function is shown by identification of a patient with a heterozygous mutation in the PDZ binding sequence of their P2Y(12)R (P341A) that is associated with reduced expression of the P2Y(12)R on the cell surface. Importantly, platelets from this subject showed significantly compromised P2Y(12)R recycling, emphasizing the importance of the extreme C-terminus of this receptor to ensure correct receptor traffic.
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21
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Delom F, Fessart D. Role of Phosphorylation in the Control of Clathrin-Mediated Internalization of GPCR. Int J Cell Biol 2011; 2011:246954. [PMID: 21765832 PMCID: PMC3132527 DOI: 10.1155/2011/246954] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 04/01/2011] [Indexed: 12/17/2022] Open
Abstract
The process by which G protein-coupled receptors (GPCRs) are internalized through the clathrin-coated vesicles involves interactions of multifunctional adaptor proteins. These interactions are tightly controlled by phosphorylation and dephosphorylation mechanisms resulting in the regulation of receptor endocytosis. However, the identities of the kinases involved in this process remained largely unknown until recently. This paper discusses advances in our knowledge of the important role played by protein phosphorylation in the regulation of the endocytic machinery and how phosphorylation controls the coated vesicle cycle.
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Affiliation(s)
- Frederic Delom
- Bordeaux Cardiothoracic Research Center, Bordeaux University, 146, Léo-Saignat, 33076 Bordeaux, France
- Inserm U1045, 146, Léo-Saignat, 33076 Bordeaux, France
| | - Delphine Fessart
- Bordeaux Cardiothoracic Research Center, Bordeaux University, 146, Léo-Saignat, 33076 Bordeaux, France
- Inserm U1045, 146, Léo-Saignat, 33076 Bordeaux, France
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22
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Björk K, Svenningsson P. Modulation of monoamine receptors by adaptor proteins and lipid rafts: role in some effects of centrally acting drugs and therapeutic agents. Annu Rev Pharmacol Toxicol 2011; 51:211-42. [PMID: 20887195 DOI: 10.1146/annurev-pharmtox-010510-100520] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The monoamines and their cognate receptors are widespread in the central nervous system and are vital for normal brain function. Dysfunction in these systems underlies several psychiatric and neurological disease states, and consequently monoamines are targets of a host of pharmacotherapies. This review provides an overview on how monoamine receptors are regulated by adaptor proteins and lipid rafts with emphasis on interactions in nerve cells. Monoamine receptors have prominent intracellular loops that provide binding sites for adaptor proteins. Receptor function is further modulated by cholesterol and submembranous microdomains termed lipid rafts. These interactions determine several facets of G protein-coupled receptor (GPCR) function including trafficking, localization, and signaling. Possible roles of adaptor proteins and lipid rafts in disease states and in mediating actions of drugs and therapeutic agents are also discussed.
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Affiliation(s)
- Karl Björk
- Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
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23
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Brady AE, Chen Y, Limbird LE, Wang Q. Study of GPCR-protein interactions using gel overlay assays and glutathione-S-transferase-fusion protein pull-downs. Methods Mol Biol 2011; 746:347-355. [PMID: 21607867 DOI: 10.1007/978-1-61779-126-0_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Numerous recent studies have suggested that the predicted cytosolic domains of G protein-coupled receptors represent a surface for association with proteins that may serve multiple roles in receptor localization, turnover, and signaling beyond the well-characterized interactions of these receptors with heterotrimeric G proteins. This Chapter describes two in vitro methods for ascertaining interactions between G protein-coupled receptors and various binding partners: gel overlay strategies and GST-fusion protein pull-downs.
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Affiliation(s)
- Ashley E Brady
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
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24
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Abstract
The α1-adrenergic receptor (AR) subtypes (α1a, α1b, and α1d) mediate several physiological effects of epinephrineand norepinephrine. Despite several studies in recombinant systems and insightfrom genetically modified mice, our understanding of the physiological relevance and specificity of the α1-AR subtypes is still limited. Constitutive activity and receptor oligomerization have emerged as potential features regulating receptor function. Another recent paradigm is that βarrestins and G protein-coupled receptors themselves can act as scaffolds binding a variety of proteins and this can result in growing complexity of the receptor-mediated cellular effects. The aim of this review is to summarize our current knowledge on some recently identified functional paradigms and signaling networks that might help to elucidate the functional diversity of the α1-AR subtypes in various organs.
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Affiliation(s)
- Susanna Cotecchia
- Dipartimento di Fisiologia Generale e Ambientale, Università di Bari, Italy.
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25
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Avellar MCW, Lázari MFM, Porto CS. Expression and function of G-protein-coupled receptorsin the male reproductive tract. AN ACAD BRAS CIENC 2009; 81:321-44. [DOI: 10.1590/s0001-37652009000300002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2008] [Accepted: 08/14/2008] [Indexed: 11/22/2022] Open
Abstract
This review focuses on the expression and function of muscarinic acetylcholine receptors (mAChRs), α1-adrenoceptors and relaxin receptors in the male reproductive tract. The localization and differential expression of mAChR and α1-adrenoceptor subtypes in specific compartments of the efferent ductules, epididymis, vas deferens, seminal vesicle and prostate of various species indicate a role for these receptors in the modulation of luminal fluid composition and smooth muscle contraction, including effects on male fertility. Furthermore, the activation of mAChRs induces transactivation of the epidermal growth factor receptor (EGFR) and the Sertoli cell proliferation. The relaxin receptors are present in the testis, RXFP1 in elongated spermatids and Sertoli cells from rat, and RXFP2 in Leydig and germ cells from rat and human, suggesting a role for these receptors in the spermatogenic process. The localization of both receptors in the apical portion of epithelial cells and smooth muscle layers of the vas deferens suggests an involvement of these receptors in the contraction and regulation of secretion.
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26
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Hoque MT, Cole SP. Down-regulation of Na+/H+Exchanger Regulatory Factor 1 Increases Expression and Function of Multidrug Resistance Protein 4. Cancer Res 2008; 68:4802-9. [DOI: 10.1158/0008-5472.can-07-6778] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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27
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Stanasila L, Abuin L, Dey J, Cotecchia S. Different Internalization Properties of the α1a- and α1b-Adrenergic Receptor Subtypes: The Potential Role of Receptor Interaction with β-Arrestins and AP50. Mol Pharmacol 2008; 74:562-73. [DOI: 10.1124/mol.107.043422] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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28
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Lee AW, Pfaff DW. Hormone effects on specific and global brain functions. J Physiol Sci 2008; 58:213-20. [PMID: 18505601 DOI: 10.2170/physiolsci.rv007008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Accepted: 05/24/2008] [Indexed: 11/05/2022]
Abstract
The first demonstration of how biochemical changes in neurons in specific parts of the brain direct a complete mammalian behavior derived from the effects of estrogens in hypothalamic neurons that facilitate lordosis behavior, the primary reproductive behavior of female quadrupeds (Pfaff. Estrogens and Brain Function. 1980; Pfaff. Drive: Neurobiological and Molecular Mechanisms of Sexual Motivation. 1999). Sex behaviors depend on sexual arousal that in turn depends on a primitive function: generalized CNS arousal (Pfaff. Brain Arousal and Information Theory. 2006). Here we summarize one of the ways in which a generalized arousal transmitter, norepinephrine, can influence the electrical excitability of ventromedial hypothalamic cells in a way that will foster female sex behavior.
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Affiliation(s)
- A W Lee
- Laboratory of Neurobiology and Behavior, The Rockefeller University, New York, NY 10021, USA
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29
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Lyssand JS, DeFino MC, Tang XB, Hertz AL, Feller DB, Wacker JL, Adams ME, Hague C. Blood pressure is regulated by an alpha1D-adrenergic receptor/dystrophin signalosome. J Biol Chem 2008; 283:18792-800. [PMID: 18468998 DOI: 10.1074/jbc.m801860200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hypertension is a cardiovascular disease associated with increased plasma catecholamines, overactivation of the sympathetic nervous system, and increased vascular tone and total peripheral resistance. A key regulator of sympathetic nervous system function is the alpha(1D)-adrenergic receptor (AR), which belongs to the adrenergic family of G-protein-coupled receptors (GPCRs). Endogenous catecholamines norepinephrine and epinephrine activate alpha(1D)-ARs on vascular smooth muscle to stimulate vasoconstriction, which increases total peripheral resistance and mean arterial pressure. Indeed, alpha(1D)-AR KO mice display a hypotensive phenotype and are resistant to salt-induced hypertension. Unfortunately, little information exists about how this important GPCR functions because of an inability to obtain functional expression in vitro. Here, we identified the dystrophin proteins, syntrophin, dystrobrevin, and utrophin as essential GPCR-interacting proteins for alpha(1D)-ARs. We found that dystrophins complex with alpha(1D)-AR both in vitro and in vivo to ensure proper functional expression. More importantly, we demonstrate that knock-out of multiple syntrophin isoforms results in the complete loss of alpha(1D)-AR function in mouse aortic smooth muscle cells and abrogation of alpha(1D)-AR-mediated increases in blood pressure. Our findings demonstrate that syntrophin and utrophin associate with alpha(1D)-ARs to create a functional signalosome, which is essential for alpha(1D)-AR regulation of vascular tone and blood pressure.
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Affiliation(s)
- John S Lyssand
- Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA
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30
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Maurice P, Daulat AM, Broussard C, Mozo J, Clary G, Hotellier F, Chafey P, Guillaume JL, Ferry G, Boutin JA, Delagrange P, Camoin L, Jockers R. A generic approach for the purification of signaling complexes that specifically interact with the carboxyl-terminal domain of G protein-coupled receptors. Mol Cell Proteomics 2008; 7:1556-69. [PMID: 18448421 DOI: 10.1074/mcp.m700435-mcp200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
G protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors and are major drug targets. Recent progress has shown that GPCRs are part of large protein complexes that regulate their activity. We present here a generic approach for identification of these complexes that is based on the use of receptor subdomains and that overcomes the limitations of currently used genetics and proteomics approaches. Our approach consists of a carefully balanced combination of chemically synthesized His6-tagged baits, immobilized metal affinity chromatography, one- and two-dimensional gel electrophoresis separation and mass spectrometric identification. The carboxyl-terminal tails (C-tails) of the human MT1 and MT2 melatonin receptors, two class A GPCRs, were used as models to purify protein complexes from mouse brain lysates. We identified 32 proteins that interacted with the C-tail of MT1, 14 proteins that interacted with the C-tail of MT2, and eight proteins that interacted with both C-tails. Several randomly selected proteins were validated by Western blotting, and the functional relevance of our data was further confirmed by showing the interaction between the full-length MT1 and the regulator of G protein signaling Z1 in transfected HEK 293 cells and native tissue. Taken together, we have established an integrated and generic purification strategy for the identification of high quality and functionally relevant GPCR-associated protein complexes that significantly widens the repertoire of available techniques.
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Affiliation(s)
- Pascal Maurice
- Department of Cell Biology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris F-75014, France
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31
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Marchese A, Paing MM, Temple BRS, Trejo J. G protein-coupled receptor sorting to endosomes and lysosomes. Annu Rev Pharmacol Toxicol 2008; 48:601-29. [PMID: 17995450 DOI: 10.1146/annurev.pharmtox.48.113006.094646] [Citation(s) in RCA: 339] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The heptahelical G protein-coupled receptors (GPCRs) belong to the largest family of cell surface signaling receptors encoded in the human genome. GPCRs signal to diverse extracellular stimuli and control a vast number of physiological responses, making this receptor class the target of nearly half the drugs currently in use. In addition to rapid desensitization, receptor trafficking is crucial for the temporal and spatial control of GPCR signaling. Sorting signals present in the intracytosolic domains of GPCRs regulate trafficking through the endosomal-lysosomal system. GPCR internalization is mediated by serine and threonine phosphorylation and arrestin binding. Short, linear peptide sequences including tyrosine- and dileucine-based motifs, and PDZ ligands that are recognized by distinct endocytic adaptor proteins also mediate internalization and endosomal sorting of GPCRs. We present new data from bioinformatic searches that reveal the presence of these types of sorting signals in the cytoplasmic tails of many known GPCRs. Several recent studies also indicate that the covalent modification of GPCRs with ubiquitin serves as a signal for internalization and lysosomal sorting, expanding the diversity of mechanisms that control trafficking of mammalian GPCRs.
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Affiliation(s)
- Adriano Marchese
- Department of Pharmacology and Experimental Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
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Urs NM, Kowalczyk AP, Radhakrishna H. Different Mechanisms Regulate Lysophosphatidic Acid (LPA)-dependent Versus Phorbol Ester-dependent Internalization of the LPA1 Receptor. J Biol Chem 2008; 283:5249-57. [DOI: 10.1074/jbc.m710003200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Huang R, He S, Chen Z, Dillon GH, Leidenheimer NJ. Mechanisms of homomeric alpha1 glycine receptor endocytosis. Biochemistry 2007; 46:11484-93. [PMID: 17887775 PMCID: PMC2597333 DOI: 10.1021/bi701093j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Little is known regarding the mechanism(s) by which glycine receptors are endocytosed. Here we examined the endocytosis of homomeric alpha1 glycine receptors expressed in HEK 293 cells using immunofluorescence/confocal microscopy and whole-cell patch-clamp recordings. Our studies demonstrate that constitutive endocytosis of glycine receptors is blocked by the dominant negative dynamin construct K44A and that intracellular dialysis with peptide P4, a dynamin/amphiphysin-disrupting peptide, increased whole-cell glycine-gated chloride currents. To examine whether receptor endocytosis could be regulated by PKC, experiments with the PKC activator PMA (phorbol 12-myristate 13-acetate) were performed. PMA, but not its inactive analogue PMM (phorbol 12-monomyristate), stimulated receptor endocytosis and inhibited glycine-gated chloride currents. Similar to constitutive endocytosis, PKC-stimulated endocytosis was blocked by dynamin K44A. Mutation of a putative AP2 adaptin dileucine motif (L314A, L315A) present in the receptor cytoplasmic loop blocked PMA-stimulated receptor endocytosis and also prevented PMA inhibition of glycine receptor currents. In patch-clamp experiments, intracellular dialysis of a 12-amino acid peptide corresponding to the region of the receptor containing the dileucine motif prevented PKC modulation of wild-type glycine receptors. Unlike PKC modulation of the receptor, constitutive endocytosis was not affected by mutation of this dileucine motif. These results demonstrate that PKC activation stimulates glycine receptor endocytosis, that both constitutive endocytosis and PKC-stimulated endocytosis are dynamin-dependent, and that PKC-stimulated endocytosis, but not constitutive endocytosis, occurs via the dileucine motif (L314A, L315A) within the cytoplasmic loop of the receptor.
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Affiliation(s)
- Renqi Huang
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | - Shaoqing He
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | - Zhenglan Chen
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | - Glenn H. Dillon
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | - Nancy J. Leidenheimer
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA
- To whom correspondence should be addressed: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130. Phone (318) 675-7855. Fax: (318) 675-5180. E-mail:
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34
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Holliday ND, Holst B, Rodionova EA, Schwartz TW, Cox HM. Importance of constitutive activity and arrestin-independent mechanisms for intracellular trafficking of the ghrelin receptor. Mol Endocrinol 2007; 21:3100-12. [PMID: 17717076 DOI: 10.1210/me.2007-0254] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The ghrelin receptor (GhrelinR) and its related orphan GPR39 each display constitutive signaling, but only GhrelinRs undergo basal internalization. Here we investigate these differences by considering the roles of the C tail receptor domains for constitutive internalization and activity. Furthermore the interaction between phosphorylated receptors and beta-arrestin adaptor proteins has been examined. Replacement of the FLAG-tagged GhrelinR C tail with the equivalent GPR39 domain (GhR-39 chimera) preserved G(q) signaling. However in contrast to the GhrelinR, GhR-39 receptors exhibited no basal and substantially decreased agonist-induced internalization in transiently transfected HEK293 cells. Internalized GhrelinR and GhR-39 were predominantly localized to recycling compartments, identified with transferrin and the monomeric G proteins Rab5 and Rab11. Both the inverse agonist [d-Arg(1), d-Phe(5), d-Trp(7,9), Leu(11)] substance P and a naturally occurring mutant GhrelinR (A204E) with eliminated constitutive activity inhibited basal GhrelinR internalization. Surprisingly, we found that noninternalizing GPR39 was highly phosphorylated and that basal and agonist-induced phosphorylation of the GhR-39 chimera was elevated compared with GhrelinRs. Moreover, basal GhrelinR endocytosis occurred without significant phosphorylation, and it was not prevented by cotransfection of a dominant-negative beta-arrestin1(319-418) fragment or by expression in beta-arrestin1/2 double-knockout mouse embryonic fibroblasts. In contrast, agonist-stimulated GhrelinRs recruited the clathrin adaptor green fluorescent protein-tagged beta-arrestin2 to endosomes, coincident with increased receptor phosphorylation. Thus, GhrelinR internalization to recycling compartments depends on C-terminal motifs and constitutive activity, but the high levels of GPR39 phosphorylation, and of the GhR-39 chimera, are not sufficient to drive endocytosis. In addition, basal GhrelinR internalization occurs independently of beta-arrestins.
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Affiliation(s)
- Nicholas D Holliday
- Institute of Cell Signalling, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
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35
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Hamdan FF, Rochdi MD, Breton B, Fessart D, Michaud DE, Charest PG, Laporte SA, Bouvier M. Unraveling G protein-coupled receptor endocytosis pathways using real-time monitoring of agonist-promoted interaction between beta-arrestins and AP-2. J Biol Chem 2007; 282:29089-100. [PMID: 17675294 DOI: 10.1074/jbc.m700577200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The most widely studied pathway underlying agonist-promoted internalization of G protein-coupled receptors (GPCRs) involves beta-arrestin and clathrin-coated pits. However, both beta-arrestin- and clathrin-independent processes have also been reported. Classically, the endocytic routes are characterized using pharmacological inhibitors and various dominant negative mutants, resulting sometimes in conflicting results and interpretational difficulties. Here, taking advantage of the fact that beta-arrestin binding to the beta2 subunit of the clathrin adaptor AP-2 (beta2-adaptin) is needed for the beta-arrestin-mediated targeting of GPCRs to clathrin-coated pits, we developed a bioluminescence resonance energy transfer-based approach directly assessing the molecular steps involved in the endocytosis of GPCRs in living cells. For 10 of the 12 receptors tested, including some that were previously suggested to internalize via clathrin-independent pathways, agonist stimulation promoted beta-arrestin 1 and 2 interaction with beta2-adaptin, indicating a beta-arrestin- and clathrin-dependent endocytic process. Detailed analyses of beta-arrestin interactions with both the receptor and beta2-adaptin also allowed us to demonstrate that recruitment of beta-arrestins to the receptor and the ensuing conformational changes are the leading events preceding AP-2 engagement and subsequent clathrin-mediated endocytosis. Among the receptors tested, only the endothelin A and B receptors failed to promote interaction between beta-arrestins and beta2-adaptin. However, both receptors recruited beta-arrestins upon agonist stimulation, suggesting a beta-arrestin-dependent but clathrin-independent route of internalization for these two receptors. In addition to providing a new tool to dissect the molecular events involved in GPCR endocytosis, the bioluminescence resonance energy transfer-based beta-arrestin/beta2-adaptin interaction assay represents a novel biosensor to assess receptor activation.
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Affiliation(s)
- Fadi F Hamdan
- Department of Biochemistry, Groupe de Recherche Universitaire sur le Médicament, Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec, Canada
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36
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Abstract
To ensure that extracellular stimuli are translated into intracellular signals of appropriate magnitude and specificity, most signaling cascades are tightly regulated. One of the major mechanisms involved in the regulation of G protein-coupled receptors (GPCRs) involves their endocytic trafficking. GPCR endocytic trafficking entails the targeting of receptors to discrete endocytic sites at the plasma membrane, followed by receptor internalization and intracellular sorting. This regulates the level of cell surface receptors, the sorting of receptors to degradative or recycling pathways, and in some cases the specific signaling pathways. In this chapter we discuss the mechanisms that regulate receptor endocytic trafficking, emphasizing the role of GPCR kinases (GRKs) and arrestins in this process.
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Affiliation(s)
- Catherine A C Moore
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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37
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Fessart D, Simaan M, Zimmerman B, Comeau J, Hamdan FF, Wiseman PW, Bouvier M, Laporte SA. Src-dependent phosphorylation of beta2-adaptin dissociates the beta-arrestin-AP-2 complex. J Cell Sci 2007; 120:1723-32. [PMID: 17456551 DOI: 10.1242/jcs.03444] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Beta-arrestins are known to act as endocytic adaptors by recruiting the clathrin adaptor protein 2 (AP-2) complex to G-protein-coupled receptors (GPCRs), linking them to clathrin-coated pits (CCPs) for internalization. They also act as signaling molecules connecting GPCRs to different downstream effectors. We have previously shown that stimulation of the angiotensin II (Ang II) type 1 receptor (AGTR1, hereafter referred to as AT1R), a member of the GPCR family, promotes the formation of a complex between beta-arrestin, the kinase Src and AP-2. Here, we report that formation of such a complex is involved in the AT1R-mediated tyrosine phosphorylation of beta2-adaptin, the subunit of AP-2 involved in binding beta-arrestin. We identify a crucial tyrosine residue in the ear domain of beta2-adaptin and show in vitro that the phosphorylation of this site regulates the interaction between beta-arrestin and beta2-adaptin. Using fluorescently tagged proteins combined with resonance energy transfer and image cross-correlation spectroscopy approaches, we show in live cells that beta2-adaptin phosphorylation is an important regulatory process for the dissociation of beta-arrestin-AP-2 complexes in CCPs. Finally, we show that beta2-adaptin phosphorylation is involved in the early steps of receptor internalization. Our findings not only unveil beta2-adaptin as a new Src target during AT1R internalization, but also support the role of receptor-mediated signaling in the control of clathrin-dependent endocytosis of receptors.
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Affiliation(s)
- Delphine Fessart
- Hormones and Cancer Research Unit, Department of Medicine, Royal Victoria Hospital, Montréal, QC, H3A 1A1, Canada
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Abstract
The heptahelical G protein-coupled receptor (GPCR) family includes approximately 900 members and is the largest family of signaling receptors encoded in the mammalian genome. G protein-coupled receptors elicit cellular responses to diverse extracellular stimuli at the plasma membrane and some internalized receptors continue to signal from intracellular compartments. In addition to rapid desensitization, receptor trafficking is critical for regulation of the temporal and spatial aspects of GPCR signaling. Indeed, GPCR internalization functions to control signal termination and propagation as well as receptor resensitization. Our knowledge of the mechanisms that regulate mammalian GPCR endocytosis is based predominantly on arrestin regulation of receptors through a clathrin- and dynamin-dependent pathway. However, multiple clathrin adaptors, which recognize distinct endocytic signals, are now known to function in clathrin-mediated endocytosis of diverse cargo. Given the vast number and diversity of GPCRs, the complexity of clathrin-mediated endocytosis and the discovery of multiple clathrin adaptors, a single universal mechanism controlling endocytosis of all mammalian GPCRs is unlikely. Indeed, several recent studies now suggest that endocytosis of different GPCRs is regulated by distinct mechanisms and clathrin adaptors. In this review, we discuss the diverse mechanisms that regulate clathrin-dependent GPCR endocytosis.
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Affiliation(s)
- Breann L Wolfe
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, 1106 Mary Ellen Jones Building, CB#7365, Chapel Hill, NC 27599-7563, USA
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39
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Abstract
G protein-coupled receptors (GPCRs) play an integral role in the signal transduction of an enormous array of biological phenomena, thereby serving to modulate at a molecular level almost all components of human biology. This role is nowhere more evident than in cardiovascular biology, where GPCRs regulate such core measures of cardiovascular function as heart rate, contractility, and vascular tone. GPCR/ligand interaction initiates signal transduction cascades, and requires the presence of the receptor at the plasma membrane. Plasma membrane localization is in turn a function of the delivery of a receptor to and removal from the cell surface, a concept defined most broadly as receptor trafficking. This review illuminates our current view of GPCR trafficking, particularly within the cardiovascular system, as well as highlights the recent and provocative finding that components of the GPCR trafficking machinery can facilitate GPCR signaling independent of G protein activation.
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Affiliation(s)
- Matthew T Drake
- Howard Hughes Medical Institute and Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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40
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Mundell SJ, Luo J, Benovic JL, Conley PB, Poole AW. Distinct clathrin-coated pits sort different G protein-coupled receptor cargo. Traffic 2006; 7:1420-31. [PMID: 16899088 DOI: 10.1111/j.1600-0854.2006.00469.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Upon activation, many G protein-coupled receptors (GPCRs) internalize by clathrin-mediated endocytosis and are subsequently sorted to undergo recycling or lysosomal degradation. Here we observe that sorting can take place much earlier than previously thought, by entry of different GPCRs into distinct populations of clathrin-coated pit (CCP). These distinct populations were revealed by analysis of two purinergic GPCRs, P2Y(1) and P2Y(12), which enter two populations of CCPs in a mutually exclusive manner. The mechanisms underlying early GPCR sorting involve differential kinase-dependent processes because internalization of P2Y(12) is mediated by GPCR kinases (GRKs) and arrestin, whereas P2Y(1) internalization is GRK- and arrestin-independent but requires protein kinase C. Importantly, the beta(2) adrenoceptor which also internalizes in a GRK-dependent manner also traffics exclusively to P2Y(12)-containing CCPs. Our data therefore reveal distinct populations of CCPs that sort GPCR cargo at the plasma membrane using different kinase-dependent mechanisms.
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MESH Headings
- Antibodies, Monoclonal/metabolism
- Arrestin/metabolism
- Cell Line
- Cell Membrane/metabolism
- Cell Membrane/ultrastructure
- Clathrin/metabolism
- Coated Pits, Cell-Membrane/metabolism
- Endocytosis/physiology
- Humans
- Protein Kinases/genetics
- Protein Kinases/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2Y1
- Receptors, Purinergic P2Y12
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Affiliation(s)
- Stuart J Mundell
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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41
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Xu Q, Xu N, Zhang T, Zhang H, Li Z, Yin F, Lu Z, Han Q, Zhang Y. Mammalian Tolloid Alters Subcellular Localization, Internalization, and Signaling of α1a-Adrenergic Receptors. Mol Pharmacol 2006; 70:532-41. [PMID: 16690783 DOI: 10.1124/mol.105.016451] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we identified the CUB5 domain of mammalian Tolloid (mTLD) as a novel protein binding to alpha(1A)-adrenergic receptor (AR) using the yeast two-hybrid system. Whereas CUB5 did not couple to either alpha(1B)-AR or alpha(1D)-AR. It was determined that amino acids 322 to 359 of alpha(1A)-AR were the major binding region for CUB5. The direct interaction between alpha(1A)-AR cytoplasmic tail and CUB5 was discovered by glutathione S-transferase pull-down assay. We confirmed the interaction of mTLD with alpha(1A)-AR in human embryonic kidney (HEK) 293 cells by immunoprecipitation, immunofluorescence, and fluorescence resonance energy transfer. Although mTLD did not affect the density and affinity of receptors in crudely prepared membranes from HEK293 cells stably expressing alpha(1A)-AR, it significantly altered the subcellular localization of the receptors. Moreover, mTLD reduced the level of cell surface alpha(1A)-ARs, delayed the initial rate of agonist-induced receptor internalization, and facilitated agonist-induced calcium transient. We have demonstrated that mTLD interacts with alpha(1A)-AR directly, alters the subcellular localization of receptor, and influences agonist-induced alpha(1A)-AR internalization and calcium signaling.
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Affiliation(s)
- Qi Xu
- Institute of Vascular Medicine, Peking University Third Hospital, No.49 Huayuan North Road, Haidian District, Beijing, P.R. China 100083
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42
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Paing MM, Johnston CA, Siderovski DP, Trejo J. Clathrin adaptor AP2 regulates thrombin receptor constitutive internalization and endothelial cell resensitization. Mol Cell Biol 2006; 26:3231-42. [PMID: 16581796 PMCID: PMC1446942 DOI: 10.1128/mcb.26.8.3231-3242.2006] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protease-activated receptor 1 (PAR1), a G protein-coupled receptor for the coagulant protease thrombin, is irreversibly activated by proteolysis. Unactivated PAR1 cycles constitutively between the plasma membrane and intracellular stores, thereby providing a protected receptor pool that replenishes the cell surface after thrombin exposure and leads to rapid resensitization to thrombin signaling independent of de novo receptor synthesis. Here, we show that AP2, a clathrin adaptor, binds directly to a tyrosine-based motif in the cytoplasmic tail of PAR1 and is essential for constitutive receptor internalization and cellular recovery of thrombin signaling. Expression of a PAR1 tyrosine mutant or depletion of AP2 by RNA interference leads to significant inhibition of PAR1 constitutive internalization, loss of intracellular uncleaved PAR1, and failure of endothelial cells and other cell types to regain thrombin responsiveness. Our findings establish a novel role for AP2 in direct regulation of PAR1 trafficking, a process critically important to the temporal and spatial aspects of thrombin signaling.
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Affiliation(s)
- May M Paing
- Department of Pharmacology, University of North Carolina at Chapel Hill, 1106 Mary Ellen Jones Bldg., Chapel Hill, NC 27599-7365. USA
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Chen Z, Hague C, Hall RA, Minneman KP. Syntrophins regulate alpha1D-adrenergic receptors through a PDZ domain-mediated interaction. J Biol Chem 2006; 281:12414-20. [PMID: 16533813 DOI: 10.1074/jbc.m508651200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
To find novel cytoplasmic binding partners of the alpha1D-adrenergic receptor (AR), a yeast two-hybrid screen using the alpha1D-AR C terminus as bait was performed on a human brain cDNA library. Alpha-syntrophin, a protein containing one PDZ domain and two pleckstrin homology domains, was isolated in this screen as an alpha1D-AR-interacting protein. Alpha-syntrophin specifically recognized the C terminus of alpha1D- but not alpha1A- or alpha1B-ARs. In blot overlay assays, the PDZ domains of syntrophin isoforms alpha, beta1, and beta2 but not gamma1 or gamma2 showed strong selective interactions with the alpha1D-AR C-tail fusion protein. In transfected human embryonic kidney 293 cells, full-length alpha1D- but not alpha1A- or alpha1B-ARs co-immunoprecipitated with syntrophins, and the importance of the receptor C terminus for the alpha1D-AR/syntrophin interaction was confirmed using chimeric receptors. Mutation of the PDZ-interacting motif at the alpha1D-AR C terminus markedly decreased inositol phosphate formation stimulated by norepinephrine but not carbachol in transfected HEK293 cells. This mutation also dramatically decreased alpha1D-AR binding and protein expression. In addition, stable overexpression of alpha-syntrophin significantly increased alpha1D-AR protein expression and binding but did not affect those with a mutated PDZ-interacting motif, suggesting that syntrophin plays an important role in maintaining receptor stability by directly interacting with the receptor PDZ-interacting motif. This direct interaction may provide new information about the regulation of alpha1D-AR signaling and the role of syntrophins in modulating G protein-coupled receptor function.
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Affiliation(s)
- Zhongjian Chen
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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44
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Stanasila L, Abuin L, Diviani D, Cotecchia S. Ezrin directly interacts with the alpha1b-adrenergic receptor and plays a role in receptor recycling. J Biol Chem 2005; 281:4354-63. [PMID: 16352594 DOI: 10.1074/jbc.m511989200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Using the yeast two-hybrid system, we identified ezrin as a protein interacting with the C-tail of the alpha1b-adrenergic receptor (AR). The interaction was shown to occur in vitro between the receptor C-tail and the N-terminal portion of ezrin, or Four-point-one ERM (FERM) domain. The alpha1b-AR/ezrin interaction occurred inside the cells as shown by the finding that the transfected alpha1b-AR and FERM domain or ezrin could be coimmunoprecipitated from human embryonic kidney 293 cell extracts. Mutational analysis of the alpha1b-AR revealed that the binding site for ezrin involves a stretch of at least four arginines on the receptor C-tail. The results from both receptor biotinylation and immunofluorescence experiments indicated that the FERM domain impaired alpha1b-AR recycling to the plasma membrane without affecting receptor internalization. The dominant negative effect of the FERM domain, which relies on its ability to mask the ezrin binding site for actin, was mimicked by treatment of cells with cytochalasin D, an actin depolymerizing agent. A receptor mutant (DeltaR8) lacking its binding site in the C-tail for ezrin displayed delayed receptor recycling. These findings identify ezrin as a new protein directly interacting with a G protein-coupled receptor and demonstrate the direct implication of ezrin in GPCR trafficking via an actin-dependent mechanism.
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Affiliation(s)
- Laura Stanasila
- Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Lausanne, Switzerland
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45
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Abstract
Endocytosis of transmembrane receptors largely occurs via clathrin-coated vesicles that bud from the plasma membrane and deliver their cargo to the endosomal system for recycling or degradation. PIs (phosphoinositides) control the timing and localization of endocytic membrane trafficking by recruiting adaptors and other components of the transport machinery, thereby being part of a coincidence detection system in adaptor-mediated vesicle transport. Activation of organelle- and substrate-specific PI kinases by small GTPases such as Arf (ADP-ribosylation factor) and other factors may result in local changes of PI content, thereby regulating activity-dependent endocytic events including the recycling of synaptic vesicle membranes at nerve terminals. One such example is the PtdIns(4)P 5-kinase-mediated formation of PI(4,5)P2 [PtdIns(4,5)P2], which is required for the exo- and endo-cytic cycling of presynaptic vesicles and secretory granules. Over the last few years, protein X-ray crystallography in combination with biochemical and cell biological assays has been used to investigate the structure and function of many PI-binding proteins, including protein components of the endocytic machinery. These studies have provided molecular insights into the mechanisms by which PI(4,5)P2 recruits and activates adaptor proteins and their binding partners. In this mini-review, I will discuss the pathways of PI(4,5)P2 formation and its interactions with endocytic trafficking adaptors.
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46
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Abstract
Alpha1-Adrenergic receptors (AR) play an important role in the regulation of physiological responses mediated by norepinephrine and epinephrine, particularly in the cardiovascular system. The three cloned alpha1-AR subtypes (alpha1A, alpha1B, and alpha1D) are G protein-coupled receptors that signal through the Gq/11 signaling pathway, each showing distinct pharmacological properties and tissue distributions. However, due to the lack of highly subtype-selective drugs, the functional roles of individual subtypes are still not clear. Development of new subtype-specific drugs will greatly facilitate the identification of the functions of each subtype. Conopeptide rho-TIA has been found to be a new alpha1B-AR selective antagonist with different modes of inhibition at alpha1-AR subtypes. In addition, recent studies using genetically engineered mice have shed some light on alpha1-AR functions in vivo, especially in the cardiovascular system and brain. Several proteins have been shown to interact directly with particular alpha1-AR, and may be important in regulating receptor function. Receptor heterodimerization has been shown to be important for cell surface expression, signaling and internalization. These new observations are likely to help elucidate the functional roles of individual alpha1-AR subtypes.
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Affiliation(s)
- Zhong-jian Chen
- Department of Pharmacology, School of Medicine, Emory University, Atlanta, GA 30322, USA
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Kittler JT, Chen G, Honing S, Bogdanov Y, McAinsh K, Arancibia-Carcamo IL, Jovanovic JN, Pangalos MN, Haucke V, Yan Z, Moss SJ. Phospho-dependent binding of the clathrin AP2 adaptor complex to GABAA receptors regulates the efficacy of inhibitory synaptic transmission. Proc Natl Acad Sci U S A 2005; 102:14871-6. [PMID: 16192353 PMCID: PMC1253579 DOI: 10.1073/pnas.0506653102] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The efficacy of synaptic inhibition depends on the number of gamma-aminobutyric acid type A receptors (GABA(A)Rs) expressed on the cell surface of neurons. The clathrin adaptor protein 2 (AP2) complex is a critical regulator of GABA(A)R endocytosis and, hence, surface receptor number. Here, we identify a previously uncharacterized atypical AP2 binding motif conserved within the intracellular domains of all GABA(A)R beta subunit isoforms. This AP2 binding motif (KTHLRRRSSQLK in the beta3 subunit) incorporates the major sites of serine phosphorylation within receptor beta subunits, and phosphorylation within this site inhibits AP2 binding. Furthermore, by using surface plasmon resonance, we establish that a peptide (pepbeta3) corresponding to the AP2 binding motif in the GABA(A)R beta3 subunit binds to AP2 with high affinity only when dephosphorylated. Moreover, the pepbeta3 peptide, but not its phosphorylated equivalent (pepbeta3-phos), enhanced the amplitude of miniature inhibitory synaptic current and whole cell GABA(A)R current. These effects of pepbeta3 on GABA(A)R current were occluded by inhibitors of dynamin-dependent endocytosis supporting an action of pepbeta3 on GABA(A)R endocytosis. Therefore phospho-dependent regulation of AP2 binding to GABA(A)Rs provides a mechanism to specify receptor cell surface number and the efficacy of inhibitory synaptic transmission.
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Affiliation(s)
- Josef T Kittler
- Department of Physiology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Madziva MT, Bai J, Bhalla A, Chapman ER, Edwardson JM. Effects of synaptotagmin reveal two distinct mechanisms of agonist-stimulated internalization of the M4 muscarinic acetylcholine receptor. Br J Pharmacol 2005; 144:761-71. [PMID: 15778699 PMCID: PMC1576056 DOI: 10.1038/sj.bjp.0706035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Synaptotagmin has been reported to function in clathrin-mediated endocytosis. Here, we investigated its involvement in agonist-stimulated internalization of M4 muscarinic acetylcholine receptors exogenously expressed in human embryonic kidney (HEK-293 tsA201) cells. 2. Synaptotagmin I was present at low levels in these cells, and when overexpressed resided at the plasma membrane. 3. Synaptotagmin overexpression alone did not affect receptor internalization, but 'rescued' internalization that had been inhibited by either dominant-negative dynamin-1 or dominant-negative arrestin-2. Both normal and 'rescued' internalization were sensitive to inhibitors of clathrin-mediated endocytosis, but not to inhibitors of the function of caveolae. 4. There was no increase in AP-2 recruitment to the plasma membrane in cells overexpressing synaptotagmin. However, a mutant form of the receptor lacking a potential AP-2 recruitment motif, while being internalized normally in response to agonist stimulation, was not rescued by synaptotagmin in cells expressing dominant-negative dynamin or arrestin. 5. A mutant form of synaptotagmin (K326,327A), which binds phosphatidylinositol-4,5-bisphosphate (PIP2) much more weakly than the wild-type protein, did not rescue internalization. Furthermore, internalization was inhibited by the PH domain of phospholipase C-delta1, which sequesters PIP2, and synaptotagmin was now unable to rescue. 6. We propose that AP-2 binding to the C-terminal tail of the receptor is not normally required for its endocytosis, but that the synaptotagmin-mediated rescue involves the formation of a ternary complex with the receptor and AP-2. PIP2 might play a role as an intermediary in the formation of this complex.
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Affiliation(s)
- Michael T Madziva
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD
| | - Jihong Bai
- Department of Physiology, University of Wisconsin, Madison, WI 53706, U.S.A
| | - Akhil Bhalla
- Department of Physiology, University of Wisconsin, Madison, WI 53706, U.S.A
| | - Edwin R Chapman
- Department of Physiology, University of Wisconsin, Madison, WI 53706, U.S.A
| | - J Michael Edwardson
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD
- Author for correspondence:
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49
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Abstract
Transmembrane proteins destined to endosomes are selectively accumulated in clathrin-coated pits at the plasma membrane and rapidly internalized in clathrin-coated vesicles. The recognition of specific sequence motifs in transmembrane cargo by coated-pit proteins confers specificity on the endocytic process. Interaction of membrane cargo with the clathrin adaptor protein complex AP-2 is the major mechanism of cargo sorting into coated pits in mammalian cells. Recent studies have revealed a variety of alternative mechanisms of cargo recruitment involving additional adaptor proteins. These alternative mechanisms appear to be particularly important during clathrin-mediated endocytosis of signaling receptors.
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Affiliation(s)
- Alexander Sorkin
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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Grass I, Thiel S, Höning S, Haucke V. Recognition of a basic AP-2 binding motif within the C2B domain of synaptotagmin is dependent on multimerization. J Biol Chem 2004; 279:54872-80. [PMID: 15491995 DOI: 10.1074/jbc.m409995200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Synaptotagmin is a multifunctional membrane protein that may regulate exo-endocytic cycling of synaptic vesicles at the presynaptic plasmalemma. Its C2B domain has been postulated to interact with a variety of effector molecules including acidic phospholipids, phosphoinositides, SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), calcium channels, and the clathrin adaptor complex AP-2. Here we report that a basic motif within the C2B domain is required and sufficient for binding to AP-2 via its mu2 subunit and that this interaction is dependent on multimerization of the AP-2 binding site. Moreover, we show that upon fusion to a plasma membrane reporter protein this sequence is sufficient to target the chimeric molecule for internalization. We hypothesize that basic motifs within multimeric membrane proteins may represent a novel type of clathrin/AP-2-dependent endocytosis signal.
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Affiliation(s)
- Isabelle Grass
- Institut für Chemie-Biochemie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany
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