1
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Wedegaertner H, Bosompra O, Kufareva I, Trejo J. Divergent regulation of α-arrestin ARRDC3 function by ubiquitination. Mol Biol Cell 2023; 34:ar93. [PMID: 37223976 PMCID: PMC10398895 DOI: 10.1091/mbc.e23-02-0055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/14/2023] [Accepted: 05/19/2023] [Indexed: 05/25/2023] Open
Abstract
The α-arrestin ARRDC3 is a recently discovered tumor suppressor in invasive breast cancer that functions as a multifaceted adaptor protein to control protein trafficking and cellular signaling. However, the molecular mechanisms that control ARRDC3 function are unknown. Other arrestins are known to be regulated by posttranslational modifications, suggesting that ARRDC3 may be subject to similar regulatory mechanisms. Here we report that ubiquitination is a key regulator of ARRDC3 function and is mediated primarily by two proline-rich PPXY motifs in the ARRDC3 C-tail domain. Ubiquitination and the PPXY motifs are essential for ARRDC3 function in regulating GPCR trafficking and signaling. Additionally, ubiquitination and the PPXY motifs mediate ARRDC3 protein degradation, dictate ARRDC3 subcellular localization, and are required for interaction with the NEDD4-family E3 ubiquitin ligase WWP2. These studies demonstrate a role for ubiquitination in regulating ARRDC3 function and reveal a mechanism by which ARRDC3 divergent functions are controlled.
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Affiliation(s)
- Helen Wedegaertner
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA92093
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA92093
| | - Oye Bosompra
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA92093
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA92093
| | - Irina Kufareva
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA92093
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA92093
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA92093
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2
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Peach CJ, Edgington-Mitchell LE, Bunnett NW, Schmidt BL. Protease-activated receptors in health and disease. Physiol Rev 2023; 103:717-785. [PMID: 35901239 PMCID: PMC9662810 DOI: 10.1152/physrev.00044.2021] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 07/08/2022] [Accepted: 07/10/2022] [Indexed: 11/22/2022] Open
Abstract
Proteases are signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation; from immune, inflammatory epithelial, and cancer cells; as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure, and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.
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Affiliation(s)
- Chloe J Peach
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, New York
- Department of Neuroscience and Physiology and Neuroscience Institute, Grossman School of Medicine, New York University, New York, New York
| | - Laura E Edgington-Mitchell
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
- Bluestone Center for Clinical Research, Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, New York, New York
| | - Nigel W Bunnett
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, New York
- Department of Neuroscience and Physiology and Neuroscience Institute, Grossman School of Medicine, New York University, New York, New York
| | - Brian L Schmidt
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, New York
- Bluestone Center for Clinical Research, Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, New York, New York
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3
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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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4
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Thrombin-activated PAR1 membrane expression is regulated by Rab11a-RCP complex dissociation. Cell Signal 2020; 75:109748. [PMID: 32860953 DOI: 10.1016/j.cellsig.2020.109748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/16/2020] [Accepted: 08/19/2020] [Indexed: 11/22/2022]
Abstract
PAR1 activation by thrombin promotes intracellular signaling leading to RPE cell transformation, proliferation, and migration, characteristic of fibroproliferative eye diseases. Due to the cleavage of PAR1 N-terminal domain, carried by thrombin, the arrest of PAR1 signaling is achieved by transport into lysosomes and degradation. Recent findings suggest that the GTPase Rab11a in conjunction with its effector RCP may direct PAR1 to lysosomes. Hereby we demonstrate that thrombin-induced PAR1 internalization and lysosomal targeting requires the disassembly of the Rab11a/RCP complex, and that this process depends on thrombin-induced intracellular calcium increase and calpain activation. These findings unveil a novel mechanism that regulates thrombin activated PAR1 internalization and degradation.
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5
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Li Z, Yin M, Zhang H, Ni W, Pierce RW, Zhou HJ, Min W. BMX Represses Thrombin-PAR1-Mediated Endothelial Permeability and Vascular Leakage During Early Sepsis. Circ Res 2020; 126:471-485. [PMID: 31910739 DOI: 10.1161/circresaha.119.315769] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RATIONALE BMX (bone marrow kinase on the X chromosome) is highly expressed in the arterial endothelium from the embryonic stage to the adult stage in mice. It is also expressed in microvessels and the lymphatics in response to pathological stimuli. However, its role in endothelial permeability and sepsis remains unknown. OBJECTIVE We aimed to delineate the function of BMX in thrombin-mediated endothelial permeability and the vascular leakage that occurs with sepsis in cecal ligation and puncture models. METHODS AND RESULTS The cecal ligation and puncture model was applied to WT (wild type) and BMX-KO (BMX global knockout) mice to induce sepsis. Meanwhile, the electric cell-substrate impedance sensing assay was used to detect transendothelial electrical resistance in vitro and, the modified Miles assay was used to evaluate vascular leakage in vivo. We showed that BMX loss caused lung injury and inflammation in early cecal ligation and puncture-induced sepsis. Disruption of BMX increased thrombin-mediated permeability in mice and cultured endothelial cells by 2- to 3-fold. The expression of BMX in macrophages, neutrophils, platelets, and lung epithelial cells was undetectable compared with that in endothelial cells, indicating that endothelium dysfunction, rather than leukocyte and platelet dysfunction, was involved in vascular permeability and sepsis. Mechanistically, biochemical and cellular analyses demonstrated that BMX specifically repressed thrombin-PAR1 (protease-activated receptor-1) signaling in endothelial cells by directly phosphorylating PAR1 and promoting its internalization and deactivation. Importantly, pretreatment with the selective PAR1 antagonist SCH79797 rescued BMX loss-mediated endothelial permeability and pulmonary leakage in early cecal ligation and puncture-induced sepsis. CONCLUSIONS Acting as a negative regulator of PAR1, BMX promotes PAR1 internalization and signal inactivation through PAR1 phosphorylation. Moreover, BMX-mediated PAR1 internalization attenuates endothelial permeability to protect vascular leakage during early sepsis.
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Affiliation(s)
- Zhao Li
- From the The Center for Translational Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China (Z.L.).,Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
| | - Mingzhu Yin
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.).,Department of Dermatology, Hunan Engineering Research, Center of Skin Health and Disease, Xiangya Hospital, Central South University, China (M.Y.)
| | - Haifeng Zhang
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
| | - Weiming Ni
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
| | - Richard W Pierce
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
| | - Huanjiao Jenny Zhou
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
| | - Wang Min
- Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT (Z.L., M.Y., H.Z., W.N., R.W.P., H.J.Z., W.M.)
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6
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Willis Fox O, Preston RJS. Molecular basis of protease-activated receptor 1 signaling diversity. J Thromb Haemost 2020; 18:6-16. [PMID: 31549766 DOI: 10.1111/jth.14643] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/13/2019] [Accepted: 09/17/2019] [Indexed: 12/13/2022]
Abstract
Protease-activated receptors (PARs) are a family of highly conserved G protein-coupled receptors (GPCRs) that respond to extracellular proteases via a unique proteolysis-dependent activation mechanism. Protease-activated receptor 1 (PAR1) was the first identified member of the receptor family and plays important roles in hemostasis, inflammation and malignancy. The biology underlying PAR1 signaling by its canonical agonist thrombin is well characterized; however, definition of the mechanistic basis of PAR1 signaling by other proteases, including matrix metalloproteases, activated protein C, plasmin, and activated factors VII and X, remains incompletely understood. In this review, we discuss emerging insights into the molecular bases for "biased" PAR1 signaling, including atypical PAR1 proteolysis, PAR1 heterodimer and coreceptor interactions, PAR1 translocation on the membrane surface, and interactions with different G-proteins and β-arrestins upon receptor activation. Moreover, we consider how these new insights into PAR1 signaling have acted to spur development of novel PAR1-targeted therapeutics that act to inhibit, redirect, or fine-tune PAR1 signaling output to treat cardiovascular and inflammatory disease. Finally, we discuss some of the key unanswered questions relating to PAR1 biology, in particular how differences in PAR1 proteolysis, signaling intermediate coupling, and engagement with coreceptors and GPCRs combine to mediate the diversity of identified PAR1 signaling outputs.
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Affiliation(s)
- Orla Willis Fox
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, Dublin, Ireland
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Roger J S Preston
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, Dublin, Ireland
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
- National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland
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7
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Tsai CC, Kuo FT, Lee SB, Chang YT, Fu HW. Endocytosis-dependent lysosomal degradation of Src induced by protease-activated receptor 1. FEBS Lett 2019; 593:504-517. [PMID: 30758841 DOI: 10.1002/1873-3468.13336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 01/28/2019] [Accepted: 02/07/2019] [Indexed: 11/08/2022]
Abstract
Src plays a critical role in regulating cellular responses induced by protease-activated receptor 1 (PAR1). Here, we found that PAR1 activation induces lysosomal degradation of Src. Src is associated and trafficked together with activated PAR1 to early endosomes and then sorted to lysosomes for degradation. Blocking agonist-induced endocytosis of PAR1 by inhibition of dynamin activity suppresses PAR1-induced degradation of Src. However, Src activity is neither required for agonist-induced PAR1 internalization nor required for Src degradation upon PAR1 activation. We show that PAR1 activation triggers endocytosis-dependent lysosomal degradation of Src in both human embryonic kidney 293 and human umbilical vein endothelial cells. Our finding provides a new paradigm for how an irreversibly activated receptor regulates its downstream signalling.
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Affiliation(s)
- Chung-Che Tsai
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
| | - Fang-Ting Kuo
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
| | - Sung-Bau Lee
- Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.,College of Pharmacy, Taipei Medical University, Taiwan, Republic of China
| | - Yu-Ting Chang
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
| | - Hua-Wen Fu
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.,Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
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8
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Arakaki AKS, Pan WA, Trejo J. GPCRs in Cancer: Protease-Activated Receptors, Endocytic Adaptors and Signaling. Int J Mol Sci 2018; 19:ijms19071886. [PMID: 29954076 PMCID: PMC6073120 DOI: 10.3390/ijms19071886] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 06/20/2018] [Accepted: 06/21/2018] [Indexed: 01/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are a large diverse family of cell surface signaling receptors implicated in various types of cancers. Several studies indicate that GPCRs control many aspects of cancer progression including tumor growth, invasion, migration, survival and metastasis. While it is known that GPCR activity can be altered in cancer through aberrant overexpression, gain-of-function activating mutations, and increased production and secretion of agonists, the precise mechanisms of how GPCRs contribute to cancer progression remains elusive. Protease-activated receptors (PARs) are a unique class of GPCRs implicated in cancer. PARs are a subfamily of GPCRs comprised of four members that are irreversibly activated by proteolytic cleavage induced by various proteases generated in the tumor microenvironment. Given the unusual proteolytic irreversible activation of PARs, expression of receptors at the cell surface is a key feature that influences signaling responses and is exquisitely controlled by endocytic adaptor proteins. Here, we discuss new survey data from the Cancer Genome Atlas and the Genotype-Tissue Expression projects analysis of expression of all PAR family member expression in human tumor samples as well as the role and function of the endocytic sorting machinery that controls PAR expression and signaling of PARs in normal cells and in cancer.
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Affiliation(s)
- Aleena K S Arakaki
- Biomedical Sciences Graduate Program, School of Medicine, University of California, La Jolla, San Diego, CA 92093, USA.
- Department of Pharmacology, School of Medicine, University of California, La Jolla, San Diego, CA 92093, USA.
| | - Wen-An Pan
- Department of Pharmacology, School of Medicine, University of California, La Jolla, San Diego, CA 92093, USA.
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, La Jolla, San Diego, CA 92093, USA.
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9
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Ramachandran R, Altier C, Oikonomopoulou K, Hollenberg MD. Proteinases, Their Extracellular Targets, and Inflammatory Signaling. Pharmacol Rev 2016; 68:1110-1142. [PMID: 27677721 DOI: 10.1124/pr.115.010991] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Given that over 2% of the human genome codes for proteolytic enzymes and their inhibitors, it is not surprising that proteinases serve many physiologic-pathophysiological roles. In this context, we provide an overview of proteolytic mechanisms regulating inflammation, with a focus on cell signaling stimulated by the generation of inflammatory peptides; activation of the proteinase-activated receptor (PAR) family of G protein-coupled receptors (GPCR), with a mechanism in common with adhesion-triggered GPCRs (ADGRs); and by proteolytic ion channel regulation. These mechanisms are considered in the much wider context that proteolytic mechanisms serve, including the processing of growth factors and their receptors, the regulation of matrix-integrin signaling, and the generation and release of membrane-tethered receptor ligands. These signaling mechanisms are relevant for inflammatory, neurodegenerative, and cardiovascular diseases as well as for cancer. We propose that the inflammation-triggering proteinases and their proteolytically generated substrates represent attractive therapeutic targets and we discuss appropriate targeting strategies.
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Affiliation(s)
- Rithwik Ramachandran
- Inflammation Research Network-Snyder Institute for Chronic Disease, Department of Physiology & Pharmacology (R.R., C.A., M.D.H.) and Department of Medicine (M.D.H.),University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada; Department of Pathology and Laboratory Medicine, Toronto Western Hospital, Toronto, Ontario, Canada (K.O.); and Department of Physiology and Pharmacology, Western University, London, Ontario, Canada (R.R.)
| | - Christophe Altier
- Inflammation Research Network-Snyder Institute for Chronic Disease, Department of Physiology & Pharmacology (R.R., C.A., M.D.H.) and Department of Medicine (M.D.H.),University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada; Department of Pathology and Laboratory Medicine, Toronto Western Hospital, Toronto, Ontario, Canada (K.O.); and Department of Physiology and Pharmacology, Western University, London, Ontario, Canada (R.R.)
| | - Katerina Oikonomopoulou
- Inflammation Research Network-Snyder Institute for Chronic Disease, Department of Physiology & Pharmacology (R.R., C.A., M.D.H.) and Department of Medicine (M.D.H.),University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada; Department of Pathology and Laboratory Medicine, Toronto Western Hospital, Toronto, Ontario, Canada (K.O.); and Department of Physiology and Pharmacology, Western University, London, Ontario, Canada (R.R.)
| | - Morley D Hollenberg
- Inflammation Research Network-Snyder Institute for Chronic Disease, Department of Physiology & Pharmacology (R.R., C.A., M.D.H.) and Department of Medicine (M.D.H.),University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada; Department of Pathology and Laboratory Medicine, Toronto Western Hospital, Toronto, Ontario, Canada (K.O.); and Department of Physiology and Pharmacology, Western University, London, Ontario, Canada (R.R.)
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10
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Smith TH, Coronel LJ, Li JG, Dores MR, Nieman MT, Trejo J. Protease-activated Receptor-4 Signaling and Trafficking Is Regulated by the Clathrin Adaptor Protein Complex-2 Independent of β-Arrestins. J Biol Chem 2016; 291:18453-64. [PMID: 27402844 DOI: 10.1074/jbc.m116.729285] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor-4 (PAR4) is a G protein-coupled receptor (GPCR) for thrombin and is proteolytically activated, similar to the prototypical PAR1. Due to the irreversible activation of PAR1, receptor trafficking is intimately linked to signal regulation. However, unlike PAR1, the mechanisms that control PAR4 trafficking are not known. Here, we sought to define the mechanisms that control PAR4 trafficking and signaling. In HeLa cells depleted of clathrin by siRNA, activated PAR4 failed to internalize. Consistent with clathrin-mediated endocytosis, expression of a dynamin dominant-negative K44A mutant also blocked activated PAR4 internalization. However, unlike most GPCRs, PAR4 internalization occurred independently of β-arrestins and the receptor's C-tail domain. Rather, we discovered a highly conserved tyrosine-based motif in the third intracellular loop of PAR4 and found that the clathrin adaptor protein complex-2 (AP-2) is important for internalization. Depletion of AP-2 inhibited PAR4 internalization induced by agonist. In addition, mutation of the critical residues of the tyrosine-based motif disrupted agonist-induced PAR4 internalization. Using Dami megakaryocytic cells, we confirmed that AP-2 is required for agonist-induced internalization of endogenous PAR4. Moreover, inhibition of activated PAR4 internalization enhanced ERK1/2 signaling, whereas Akt signaling was markedly diminished. These findings indicate that activated PAR4 internalization requires AP-2 and a tyrosine-based motif and occurs independent of β-arrestins, unlike most classical GPCRs. Moreover, these findings are the first to show that internalization of activated PAR4 is linked to proper ERK1/2 and Akt activation.
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Affiliation(s)
- Thomas H Smith
- From the Biomedical Sciences Graduate Program and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Luisa J Coronel
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Julia G Li
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Michael R Dores
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093, Department of Biology, Hofstra University, Hempstead, New York 11549, and
| | - Marvin T Nieman
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44016
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093,
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11
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Grimsey NJ, Coronel LJ, Cordova IC, Trejo J. Recycling and Endosomal Sorting of Protease-activated Receptor-1 Is Distinctly Regulated by Rab11A and Rab11B Proteins. J Biol Chem 2015; 291:2223-36. [PMID: 26635365 DOI: 10.1074/jbc.m115.702993] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor-1 (PAR1) is a G protein-coupled receptor that undergoes proteolytic irreversible activation by coagulant and anti-coagulant proteases. Given the irreversible activation of PAR1, signaling by the receptor is tightly regulated through desensitization and intracellular trafficking. PAR1 displays both constitutive and agonist-induced internalization. Constitutive internalization of PAR1 is important for generating an internal pool of naïve receptors that replenish the cell surface and facilitate resensitization, whereas agonist-induced internalization of PAR1 is critical for terminating G protein signaling. We showed that PAR1 constitutive internalization is mediated by the adaptor protein complex-2 (AP-2), whereas AP-2 and epsin control agonist-induced PAR1 internalization. However, the mechanisms that regulate PAR1 recycling are not known. In the present study we screened a siRNA library of 140 different membrane trafficking proteins to identify key regulators of PAR1 intracellular trafficking. In addition to known mediators of PAR1 endocytosis, we identified Rab11B as a critical regulator of PAR1 trafficking. We found that siRNA-mediated depletion of Rab11B and not Rab11A blocks PAR1 recycling, which enhanced receptor lysosomal degradation. Although Rab11A is not required for PAR1 recycling, depletion of Rab11A resulted in intracellular accumulation of PAR1 through disruption of basal lysosomal degradation of the receptor. Moreover, enhanced degradation of PAR1 observed in Rab11B-deficient cells is blocked by depletion of Rab11A and the autophagy related-5 protein, suggesting that PAR1 is shuttled to an autophagic degradation pathway in the absence of Rab11B recycling. Together these findings suggest that Rab11A and Rab11B differentially regulate intracellular trafficking of PAR1 through distinct endosomal sorting mechanisms.
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Affiliation(s)
- Neil J Grimsey
- From the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Luisa J Coronel
- From the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Isabel Canto Cordova
- From the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - JoAnn Trejo
- From the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
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12
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Dores MR, Lin H, J Grimsey N, Mendez F, Trejo J. The α-arrestin ARRDC3 mediates ALIX ubiquitination and G protein-coupled receptor lysosomal sorting. Mol Biol Cell 2015; 26:4660-73. [PMID: 26490116 PMCID: PMC4678022 DOI: 10.1091/mbc.e15-05-0284] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 10/16/2015] [Indexed: 01/21/2023] Open
Abstract
The novel ALIX-dependent GPCR sorting pathway is regulated by the a-arrestin ARRDC3. A critical role is also shown for the E3 ubiquitin ligase WWP2 in regulation of ALIX ubiquitination and lysosomal sorting of GPCRs. The sorting of G protein–coupled receptors (GPCRs) to lysosomes is critical for proper signaling and cellular responses. We previously showed that the adaptor protein ALIX regulates lysosomal degradation of protease-activated receptor-1 (PAR1), a GPCR for thrombin, independent of ubiquitin-binding ESCRTs and receptor ubiquitination. However, the mechanisms that regulate ALIX function during PAR1 lysosomal sorting are not known. Here we show that the mammalian α-arrestin arrestin domain–containing protein-3 (ARRDC3) regulates ALIX function in GPCR sorting via ubiquitination. ARRDC3 colocalizes with ALIX and is required for PAR1 sorting at late endosomes and degradation. Depletion of ARRDC3 by small interfering RNA disrupts ALIX interaction with activated PAR1 and the CHMP4B ESCRT-III subunit, suggesting that ARRDC3 regulates ALIX activity. We found that ARRDC3 is required for ALIX ubiquitination induced by activation of PAR1. A screen of nine mammalian NEDD4-family E3 ubiquitin ligases revealed a critical role for WWP2. WWP2 interacts with ARRDC3 and not ALIX. Depletion of WWP2 inhibited ALIX ubiquitination and blocked ALIX interaction with activated PAR1 and CHMP4B. These findings demonstrate a new role for the α-arrestin ARRDC3 and the E3 ubiquitin ligase WWP2 in regulation of ALIX ubiquitination and lysosomal sorting of GPCRs.
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Affiliation(s)
- Michael R Dores
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Huilan Lin
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Neil J Grimsey
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Francisco Mendez
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093
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Grimsey NJ, Aguilar B, Smith TH, Le P, Soohoo AL, Puthenveedu MA, Nizet V, Trejo J. Ubiquitin plays an atypical role in GPCR-induced p38 MAP kinase activation on endosomes. J Cell Biol 2015; 210:1117-31. [PMID: 26391660 PMCID: PMC4586747 DOI: 10.1083/jcb.201504007] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 08/18/2015] [Indexed: 12/21/2022] Open
Abstract
K63-linked ubiquitination of GPCRs mediated by the NEDD4-2 E3 ubiquitin ligase regulates recruitment of a TAB1–TAB2 complex on endosomes and stimulates p38 MAPK through a noncanonical pathway, which is critical for endothelial barrier disruption. Protease-activated receptor 1 (PAR1) is a G protein–coupled receptor (GPCR) for thrombin and promotes inflammatory responses through multiple pathways including p38 mitogen-activated protein kinase signaling. The mechanisms that govern PAR1-induced p38 activation remain unclear. Here, we define an atypical ubiquitin-dependent pathway for p38 activation used by PAR1 that regulates endothelial barrier permeability. Activated PAR1 K63-linked ubiquitination is mediated by the NEDD4-2 E3 ubiquitin ligase and initiated recruitment of transforming growth factor-β–activated protein kinase-1 binding protein-2 (TAB2). The ubiquitin-binding domain of TAB2 was essential for recruitment to PAR1-containing endosomes. TAB2 associated with TAB1, which induced p38 activation independent of MKK3 and MKK6. The P2Y1 purinergic GPCR also stimulated p38 activation via NEDD4-2–mediated ubiquitination and TAB1–TAB2. TAB1–TAB2-dependent p38 activation was critical for PAR1-promoted endothelial barrier permeability in vitro, and p38 signaling was required for PAR1-induced vascular leakage in vivo. These studies define an atypical ubiquitin-mediated signaling pathway used by a subset of GPCRs that regulates endosomal p38 signaling and endothelial barrier disruption.
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Affiliation(s)
- Neil J Grimsey
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093
| | - Berenice Aguilar
- Department of Pediatrics, School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - Thomas H Smith
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093
| | - Phillip Le
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093
| | - Amanda L Soohoo
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213
| | | | - Victor Nizet
- Department of Pediatrics, School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093
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Abstract
The lysosomal degradation of G protein-coupled receptors (GPCRs) is essential for receptor signaling and down regulation. Once internalized, GPCRs are sorted within the endocytic pathway and packaged into intraluminal vesicles (ILVs) that bud inward to form the multivesicular endosome (MVE). The mechanisms that control GPCR sorting and ILV formation are poorly understood. Quantitative strategies are important for evaluating the function of adaptor and scaffold proteins that regulate sorting of GPCRs at MVEs. In this chapter, we outline two strategies for the quantification and visualization of GPCR sorting into the lumen of MVEs. The first protocol utilizes a biochemical approach to assay the sorting of GPCRs in a population of cells, whereas the second strategy examines GPCR sorting in individual cells using immunofluorescence confocal microscopy. Combined, these assays can be used to establish the kinetics of activated GPCR lysosomal trafficking in response to specific ligands, as well as evaluate the contribution of endosomal adaptors to GPCR sorting at MVEs. The protocols presented in this chapter can be adapted to analyze GPCR sorting in a myriad of cell types and tissues, and expanded to analyze the mechanisms that regulate MVE sorting of other cargoes.
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Affiliation(s)
- Michael Robert Dores
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, USA
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Chen B, Soto AG, Coronel LJ, Goss A, van Ryn J, Trejo J. Characterization of thrombin-bound dabigatran effects on protease-activated receptor-1 expression and signaling in vitro. Mol Pharmacol 2015; 88:95-105. [PMID: 25934730 DOI: 10.1124/mol.114.096446] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 04/30/2015] [Indexed: 12/15/2022] Open
Abstract
Thrombin, the key effector protease of the coagulation cascade, drives fibrin deposition and activates human platelets through protease-activated receptor-1 (PAR1). These processes are critical to the progression of thrombotic diseases. Thrombin is the main target of anticoagulant therapy, and major efforts have led to the discovery of new oral direct inhibitors of thrombin. Dabigatran is the first oral anticoagulant licensed for the prevention of thromboembolisms associated with orthopedic surgery and stroke prevention in atrial fibrillation. Dabigatran is a direct thrombin inhibitor that effectively blocks thrombin's catalytic activity but does not preclude thrombin's exosites and binding to fibrinogen. Thus, we hypothesized that catalytically inactive thrombin retains the capacity to bind to PAR1 through exosite-I and may modulate its function independent of receptor cleavage and activation. Here, we report that dabigatran at clinically relevant concentrations is an effective and acute inhibitor of thrombin-induced PAR1 cleavage, activation, internalization, and β-arrestin recruitment in vitro. Interestingly, prolonged exposure to catalytic inactive thrombin incubated with dabigatran at 20-fold higher therapeutic concentration resulted in increased PAR1 cell-surface expression, which correlated with higher detectable levels of ubiquitinated receptor. These findings are consistent with ubiquitin function as a negative regulator of PAR1 constitutive internalization. Increased PAR1 expression also enhanced agonist-induced phosphoinositide hydrolysis and endothelial barrier permeability. Thus, catalytically inactive thrombin appears to modulate PAR1 function in vitro by stabilizing receptor cell-surface expression; but given the high clearance rate of thrombin, the high concentration of dabigatran required to achieve this effect the in vivo physiologic relevance is unknown.
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Affiliation(s)
- Buxin Chen
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
| | - Antonio G Soto
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
| | - Luisa J Coronel
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
| | - Ashley Goss
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
| | - Joanne van Ryn
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California (B.C., A.G.C., L.J.C., J.T.); Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, Connecticut (A.G.); and Department of CardioMetabolic Disease Research, Boehringer Ingelheim Pharma Gmbh, Biberach, Germany (J.R.)
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16
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Milam KE, Parikh SM. The angiopoietin-Tie2 signaling axis in the vascular leakage of systemic inflammation. Tissue Barriers 2015; 3:e957508. [PMID: 25838975 DOI: 10.4161/21688362.2014.957508] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 08/19/2014] [Indexed: 12/31/2022] Open
Abstract
The ability of small blood vessels to undergo rapid, reversible morphological changes is essential for the adaptive response to tissue injury or local infection. A canonical feature of this response is transient hyperpermeability. However, when leakiness is profound or persistent, adverse consequences accrue to the host, including organ dysfunction and shock. A growing body of literature identifies the Tie2 receptor, a transmembrane tyrosine kinase highly enriched in the endothelium, as an important regulator of vascular barrier function in health and in disease. The principal ligands of Tie2, Angiopoietins 1 and 2, exert opposite effects on this receptor in the context of inflammation. This review will focus on recent studies that have illuminated novel aspects of the exquisitely controlled Tie2 signaling axis while proposing unanswered questions and future directions for this field of study.
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Affiliation(s)
- Katelyn E Milam
- Center for Vascular Biology Research; Beth Israel Deaconess Medical Center and Harvard Medical School ; Boston, MA USA
| | - Samir M Parikh
- Center for Vascular Biology Research; Beth Israel Deaconess Medical Center and Harvard Medical School ; Boston, MA USA ; Division of Nephrology; Beth Israel Deaconess Medical Center and Harvard Medical School ; Boston, MA USA
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17
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Hänzelmann S, Wang J, Güney E, Tang Y, Zhang E, Axelsson AS, Nenonen H, Salehi AS, Wollheim CB, Zetterberg E, Berntorp E, Costa IG, Castelo R, Rosengren AH. Thrombin stimulates insulin secretion via protease-activated receptor-3. Islets 2015; 7:e1118195. [PMID: 26742564 PMCID: PMC4878264 DOI: 10.1080/19382014.2015.1118195] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The disease mechanisms underlying type 2 diabetes (T2D) remain poorly defined. Here we aimed to explore the pathophysiology of T2D by analyzing gene co-expression networks in human islets. Using partial correlation networks we identified a group of co-expressed genes ('module') including F2RL2 that was associated with glycated hemoglobin. F2Rl2 is a G-protein-coupled receptor (GPCR) that encodes protease-activated receptor-3 (PAR3). PAR3 is cleaved by thrombin, which exposes a 6-amino acid sequence that acts as a 'tethered ligand' to regulate cellular signaling. We have characterized the effect of PAR3 activation on insulin secretion by static insulin secretion measurements, capacitance measurements, studies of diabetic animal models and patient samples. We demonstrate that thrombin stimulates insulin secretion, an effect that was prevented by an antibody that blocks the thrombin cleavage site of PAR3. Treatment with a peptide corresponding to the PAR3 tethered ligand stimulated islet insulin secretion and single β-cell exocytosis by a mechanism that involves activation of phospholipase C and Ca(2+) release from intracellular stores. Moreover, we observed that the expression of tissue factor, which regulates thrombin generation, was increased in human islets from T2D donors and associated with enhanced β-cell exocytosis. Finally, we demonstrate that thrombin generation potential in patients with T2D was associated with increased fasting insulin and insulinogenic index. The findings provide a previously unrecognized link between hypercoagulability and hyperinsulinemia and suggest that reducing thrombin activity or blocking PAR3 cleavage could potentially counteract the exaggerated insulin secretion that drives insulin resistance and β-cell exhaustion in T2D.
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Affiliation(s)
- Sonja Hänzelmann
- Research Program on Biomedical Informatics (GRIB); Hospital del Mar Medical Research Institute (IMIM); Barcelona, Catalonia, Spain
- Universitat Pompeu Fabra; Parc de Recerca Biomédica de Barcelona; Barcelona, Catalonia, Spain
- Lund University Diabetes Center; Lund University; Malmö, Sweden
- Interdisciplinary Center for Clinical Research (IZKF); RWTH University Medical School; Aachen, Germany
- These authors contributed equally to this work
| | - Jinling Wang
- Lund University Diabetes Center; Lund University; Malmö, Sweden
- These authors contributed equally to this work
| | - Emre Güney
- Universitat Pompeu Fabra; Parc de Recerca Biomédica de Barcelona; Barcelona, Catalonia, Spain
- Center for Complex Network Research; Northeastern University; Boston, MA USA
| | - Yunzhao Tang
- Lund University Diabetes Center; Lund University; Malmö, Sweden
| | - Enming Zhang
- Lund University Diabetes Center; Lund University; Malmö, Sweden
| | | | - Hannah Nenonen
- Lund University Diabetes Center; Lund University; Malmö, Sweden
| | - Albert S Salehi
- Lund University Diabetes Center; Lund University; Malmö, Sweden
| | - Claes B Wollheim
- Lund University Diabetes Center; Lund University; Malmö, Sweden
- Department of Cell Physiology and Metabolism; University Medical Center; Geneva, Switzerland
| | - Eva Zetterberg
- Clinical Coagulation Research Unit; Department of Clinical Sciences Malmö; Lund University; Malmö, Sweden
| | - Erik Berntorp
- Clinical Coagulation Research Unit; Department of Clinical Sciences Malmö; Lund University; Malmö, Sweden
| | - Ivan G Costa
- Interdisciplinary Center for Clinical Research (IZKF); RWTH University Medical School; Aachen, Germany
- Helmholtz-Institute for Biomedical Engineering; RWTH University Medical School; Aachen, Germany
| | - Robert Castelo
- Research Program on Biomedical Informatics (GRIB); Hospital del Mar Medical Research Institute (IMIM); Barcelona, Catalonia, Spain
- Universitat Pompeu Fabra; Parc de Recerca Biomédica de Barcelona; Barcelona, Catalonia, Spain
| | - Anders H Rosengren
- Lund University Diabetes Center; Lund University; Malmö, Sweden
- These authors contributed equally to this work
- Correspondence to: Anders H Rosengren;
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18
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Canto I, Trejo J. Palmitoylation of protease-activated receptor-1 regulates adaptor protein complex-2 and -3 interaction with tyrosine-based motifs and endocytic sorting. J Biol Chem 2013; 288:15900-12. [PMID: 23580642 DOI: 10.1074/jbc.m113.469866] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor-1 (PAR1) is a G protein-coupled receptor for the coagulant protease thrombin. Thrombin binds to and cleaves the N terminus of PAR1, generating a new N terminus that functions as a tethered ligand that cannot diffuse away. In addition to rapid desensitization, PAR1 trafficking is critical for the regulation of cellular responses. PAR1 displays constitutive and agonist-induced internalization. Constitutive internalization of unactivated PAR1 is mediated by the clathrin adaptor protein complex-2 (AP-2), which binds to a distal tyrosine-based motif localized within the C-terminal tail (C-tail) domain. Once internalized, PAR1 is sorted from endosomes to lysosomes via AP-3 interaction with a second C-tail tyrosine motif proximal to the transmembrane domain. However, the regulatory processes that control adaptor protein recognition of PAR1 C-tail tyrosine-based motifs are not known. Here, we report that palmitoylation of PAR1 is critical for regulating proper utilization of tyrosine-based motifs and endocytic sorting. We show that PAR1 is basally palmitoylated at highly conserved C-tail cysteines. A palmitoylation-deficient PAR1 mutant is competent to signal and exhibits a marked increase in constitutive internalization and lysosomal degradation compared with wild type receptor. Intriguingly, enhanced constitutive internalization of PAR1 is mediated by AP-2 and requires the proximal tyrosine-based motif rather than the distal tyrosine motif used by wild type receptor. Moreover, palmitoylation-deficient PAR1 displays increased degradation that is mediated by AP-3. These findings suggest that palmitoylation of PAR1 regulates appropriate utilization of tyrosine-based motifs by adaptor proteins and endocytic trafficking, processes that are critical for maintaining appropriate expression of PAR1 at the cell surface.
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Affiliation(s)
- Isabel Canto
- Biomedical Sciences Graduate Program, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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Yan J, Manaenko A, Chen S, Klebe D, Ma Q, Caner B, Fujii M, Zhou C, Zhang JH. Role of SCH79797 in maintaining vascular integrity in rat model of subarachnoid hemorrhage. Stroke 2013; 44:1410-7. [PMID: 23539525 DOI: 10.1161/strokeaha.113.678474] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND AND PURPOSE Plasma thrombin concentration is increased after subarachnoid hemorrhage (SAH). However, the role of thrombin receptor (protease-activated receptor-1 [PAR-1]) in endothelial barrier disruption has not been studied. The aims of this study were to investigate the role of PAR-1 in orchestrating vascular permeability and to assess the potential therapeutics of a PAR-1 antagonist, SCH79797, through maintaining vascular integrity. METHODS SCH79797 was injected intraperitoneally into male Sprauge-Dawley rats undergoing SAH by endovascular perforation. Assessment was conducted at 24 hours after SAH for brain water content, Evans blue content, and neurobehavioral testing. To explore the role of PAR-1 activation and the specific mechanism of SCH79797's effect after SAH, Western blot, immunoprecipitation, and immunofluorescence of hippocampus tissue were performed. A p21-activated kinase-1 (PAK1) inhibitor, IPA-3, was used to explore the underlying protective mechanism of SCH79797. RESULTS At 24 hours after SAH, animals treated with SCH79797 demonstrated a reduction in brain water content, Evans blue content, and neurobehavioral deficits. SCH79797 also attenuated PAR-1 expression and maintained the level of vascular endothelial-cadherin, an important component of adherens junctions. Downstream to PAR-1, c-Src-dependent activation of p21-activated kinase-1 led to an increased serine/threonine phosphorylation of vascular endothelial-cadherin; immunoprecipitation results revealed an enhanced binding of phosphorylated vascular endothelial-cadherin with endocytosis orchestrator β-arrestin-2. These pathological states were suppressed after SCH79797 treatment. CONCLUSIONS PAR-1 activation after SAH increases microvascular permeability, at least, partly through a PAR-1-c-Src-p21-activated kinase-1-vascular endothelial-cadherin phosphorylation pathway. Through suppressing PAR-1 activity, SCH79797 plays a protective role in maintaining microvascular integrity after SAH.
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Affiliation(s)
- Junhao Yan
- Department of Anatomy and Histology, School of Basic Medical Sciences, Peking University, Beijing, China
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Lin H, Trejo J. Transactivation of the PAR1-PAR2 heterodimer by thrombin elicits β-arrestin-mediated endosomal signaling. J Biol Chem 2013; 288:11203-15. [PMID: 23476015 DOI: 10.1074/jbc.m112.439950] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Thrombin cleaves the N terminus of PAR1, generating a new N-terminal domain that functions as a tethered ligand that binds intermolecularly to activate PAR2 in trans. The mechanisms that regulate PAR1-PAR2 heterodimer signaling and trafficking are not known. We now report that PAR1 and PAR2 form a heterodimer that exhibits unique trafficking and signaling behaviors compared with receptor protomers. Using bioluminescence resonance energy transfer, immunofluorescence microscopy, co-immunoprecipitation, and cells expressing receptors exogenously and endogenously, we show that PAR1 and PAR2 specifically interact and form stable dimers. Intriguingly, the PAR1-PAR2 heterodimer displays constitutive internalization that is driven by PAR1 C-terminal tail sorting motifs and is a process that enhances dimer formation. Upon thrombin activation, PAR1-PAR2 dimers co-internalize and recruit β-arrestins to endosomes. Remarkably, PAR1-PAR2 heterodimers appear to utilize a distinct interface for β-arrestin interaction compared with receptor protomers. Moreover, thrombin-activated PAR1-PAR2 heterodimers enhance β-arrestin-mediated ERK1/2 activation in the cytoplasm, whereas activated ERK1/2 induced by the thrombin-activated PAR1 protomer redistributes to the nucleus. Thus, the formation of PAR1-PAR2 heterodimers provides additional modes of thrombin-stimulated signaling responses that appear to be distinctly regulated compared with the receptor protomer.
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Affiliation(s)
- Huilan Lin
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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Dores MR, Chen B, Lin H, Soh UJK, Paing MM, Montagne WA, Meerloo T, Trejo J. ALIX binds a YPX(3)L motif of the GPCR PAR1 and mediates ubiquitin-independent ESCRT-III/MVB sorting. ACTA ACUST UNITED AC 2012; 197:407-19. [PMID: 22547407 PMCID: PMC3341166 DOI: 10.1083/jcb.201110031] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The sorting of signaling receptors to lysosomes is an essential regulatory process in mammalian cells. During degradation, receptors are modified with ubiquitin and sorted by endosomal sorting complex required for transport (ESCRT)-0, -I, -II, and -III complexes into intraluminal vesicles (ILVs) of multivesicular bodies (MVBs). However, it remains unclear whether a single universal mechanism mediates MVB sorting of all receptors. We previously showed that protease-activated receptor 1 (PAR1), a G protein-coupled receptor (GPCR) for thrombin, is internalized after activation and sorted to lysosomes independent of ubiquitination and the ubiquitin-binding ESCRT components hepatocyte growth factor-regulated tyrosine kinase substrate and Tsg101. In this paper, we report that PAR1 sorted to ILVs of MVBs through an ESCRT-III-dependent pathway independent of ubiquitination. We further demonstrate that ALIX, a charged MVB protein 4-ESCRT-III interacting protein, bound to a YPX(3)L motif of PAR1 via its central V domain to mediate lysosomal degradation. This study reveals a novel MVB/lysosomal sorting pathway for signaling receptors that bypasses the requirement for ubiquitination and ubiquitin-binding ESCRTs and may be applicable to a subset of GPCRs containing YPX(n)L motifs.
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Affiliation(s)
- Michael R Dores
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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Activation of myeloid cell-specific adhesion class G protein-coupled receptor EMR2 via ligation-induced translocation and interaction of receptor subunits in lipid raft microdomains. Mol Cell Biol 2012; 32:1408-20. [PMID: 22310662 DOI: 10.1128/mcb.06557-11] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The adhesion class G protein-coupled receptors (adhesion-GPCRs) play important roles in diverse biological processes ranging from immunoregulation to tissue polarity, angiogenesis, and brain development. These receptors are uniquely modified by self-catalytic cleavage at a highly conserved GPCR proteolysis site (GPS) dissecting the receptor into an extracellular subunit (α) and a seven-pass transmembrane subunit (β) with cellular adhesion and signaling functions, respectively. Using the myeloid cell-restricted EMR2 receptor as a paradigm, we exam the mechanistic relevance of the subunit interaction and demonstrate a critical role for GPS autoproteolysis in mediating receptor signaling and cell activation. Interestingly, two distinct receptor complexes are identified as a result of GPS proteolysis: one consisting of a noncovalent α-β heterodimer and the other comprising two completely independent receptor subunits which distribute differentially in membrane raft microdomains. Finally, we show that receptor ligation induces subunit translocation and colocalization within lipid rafts, leading to receptor signaling and inflammatory cytokine production by macrophages. Our present data resolve earlier conflicting results and provide a new mechanism of receptor signaling, as well as providing a paradigm for signal transduction within the adhesion-GPCR family.
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Jin M, Hwang SM, Davies AJ, Shin Y, Bae JS, Lee JH, Lee EB, Song YW, Park K. Autoantibodies in primary Sjögren's syndrome patients induce internalization of muscarinic type 3 receptors. Biochim Biophys Acta Mol Basis Dis 2011; 1822:161-7. [PMID: 22137887 DOI: 10.1016/j.bbadis.2011.11.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 11/10/2011] [Accepted: 11/14/2011] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by lymphocyte infiltration into the salivary and lachrymal glands, leading to dry mouth and eyes. The presence of functional autoantibodies against muscarinic type 3 receptor (M3R) has been reported in pSS patients. However, the pathological role of anti-M3R autoantibodies in pSS salivary dysfunction remains controversial. METHODS Purified IgGs were obtained from normal (control) and primary SS patients' sera (pSS IgG). Internalization of M3R and clathrin was analyzed by biochemical assay and immunofluorescence confocal microscopy using human submandibular gland (hSMG) cells. Cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) was measured by microspectrofluorimetry. RESULTS Incubation of hSMG cells with pSS IgG (1mg/ml) significantly decreased M3R expression levels at the membrane. Carbachol-induced [Ca(2+)](i) transients (CICTs) in these cells were also inhibited by pSS IgG. In contrast to pSS IgG, control IgG had no effect on both the M3R expression level and CICTs. We found that binding of pSS IgG to M3R induces phosphorylation of the receptor, and that the pSS IgG-induced M3R internalization is prevented by the lysosomal inhibitor, chloroquine. In addition, pSS IgG decreased membrane clathrin expression, which was inhibited by atropine. Our immunofluorescence study further confirmed that pSS IgG induces a co-localization of M3R with clathrin and subsequent internalization of M3R. CONCLUSION pSS IgG induces internalization of M3R partly through a clathrin-mediated pathway. The results suggest M3R internalization as a potential mechanism to explain the exocrinopathy seen in pSS patients.
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Affiliation(s)
- Meihong Jin
- Department of Physiology, College of Medicine, Seoul National University and Dental Research Institute, Seoul 110-749, Republic of Korea
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Chen B, Dores MR, Grimsey N, Canto I, Barker BL, Trejo J. Adaptor protein complex-2 (AP-2) and epsin-1 mediate protease-activated receptor-1 internalization via phosphorylation- and ubiquitination-dependent sorting signals. J Biol Chem 2011; 286:40760-70. [PMID: 21965661 DOI: 10.1074/jbc.m111.299776] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signaling by protease-activated receptor-1 (PAR1), a G protein-coupled receptor (GPCR) for thrombin, is regulated by desensitization and internalization. PAR1 desensitization is mediated by β-arrestins, like most classic GPCRs. In contrast, internalization of PAR1 occurs through a clathrin- and dynamin-dependent pathway independent of β-arrestins. PAR1 displays two modes of internalization. Constitutive internalization of unactivated PAR1 is mediated by the clathrin adaptor protein complex-2 (AP-2), where the μ2-adaptin subunit binds directly to a tyrosine-based motif localized within the receptor C-tail domain. However, AP-2 depletion only partially inhibits agonist-induced internalization of PAR1, suggesting a function for other clathrin adaptors in this process. Here, we now report that AP-2 and epsin-1 are both critical mediators of agonist-stimulated PAR1 internalization. We show that ubiquitination of PAR1 and the ubiquitin-interacting motifs of epsin-1 are required for epsin-1-dependent internalization of activated PAR1. In addition, activation of PAR1 promotes epsin-1 de-ubiquitination, which may increase its endocytic adaptor activity to facilitate receptor internalization. AP-2 also regulates activated PAR1 internalization via recognition of distal C-tail phosphorylation sites rather than the canonical tyrosine-based motif. Thus, AP-2 and epsin-1 are both required to promote efficient internalization of activated PAR1 and recognize discrete receptor sorting signals. This study defines a new pathway for internalization of mammalian GPCRs.
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Affiliation(s)
- Buxin Chen
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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Adams MN, Ramachandran R, Yau MK, Suen JY, Fairlie DP, Hollenberg MD, Hooper JD. Structure, function and pathophysiology of protease activated receptors. Pharmacol Ther 2011; 130:248-82. [PMID: 21277892 DOI: 10.1016/j.pharmthera.2011.01.003] [Citation(s) in RCA: 267] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 01/03/2011] [Indexed: 12/18/2022]
Abstract
Discovered in the 1990s, protease activated receptors(1) (PARs) are membrane-spanning cell surface proteins that belong to the G protein coupled receptor (GPCR) family. A defining feature of these receptors is their irreversible activation by proteases; mainly serine. Proteolytic agonists remove the PAR extracellular amino terminal pro-domain to expose a new amino terminus, or tethered ligand, that binds intramolecularly to induce intracellular signal transduction via a number of molecular pathways that regulate a variety of cellular responses. By these mechanisms PARs function as cell surface sensors of extracellular and cell surface associated proteases, contributing extensively to regulation of homeostasis, as well as to dysfunctional responses required for progression of a number of diseases. This review examines common and distinguishing structural features of PARs, mechanisms of receptor activation, trafficking and signal termination, and discusses the physiological and pathological roles of these receptors and emerging approaches for modulating PAR-mediated signaling in disease.
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Affiliation(s)
- Mark N Adams
- Mater Medical Research Institute, Aubigny Place, Raymond Terrace, South Brisbane Qld 4101, Australia
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Soh UJK, Dores MR, Chen B, Trejo J. Signal transduction by protease-activated receptors. Br J Pharmacol 2010; 160:191-203. [PMID: 20423334 DOI: 10.1111/j.1476-5381.2010.00705.x] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The family of G protein-coupled receptors (GPCRs) constitutes the largest class of signalling receptors in the human genome, controlling vast physiological responses and are the target of many drugs. After activation, GPCRs are rapidly desensitized by phosphorylation and beta-arrestin binding. Most classic GPCRs are internalized through a clathrin, dynamin and beta-arrestin-dependent pathway and then recycled back to the cell surface or sorted to lysosomes for degradation. Given the vast number and diversity of GPCRs, different mechanisms are likely to exist to precisely regulate the magnitude, duration and spatial aspects of receptor signalling. The G protein-coupled protease-activated receptors (PARs) provide elegant examples of GPCRs that are regulated by distinct desensitization and endocytic sorting mechanisms, processes that are critically important for the spatial and temporal fidelity of PAR signalling. PARs are irreversibly activated through proteolytic cleavage and transmit cellular responses to extracellular proteases. Activated PAR(1) internalizes through a clathrin- and dynamin-dependent pathway independent of beta-arrestins. Interestingly, PAR(1) is basally ubiquitinated and deubiquitinated after activation and traffics from endosomes to lysosomes independent of ubiquitination. In contrast, beta-arrestins mediate activated PAR(2) internalization and function as scaffolds that promote signalling from endocytic vesicles. Moreover, activated PAR(2) is modified with ubiquitin, which facilitates lysosomal degradation. Activated PARs also adopt distinct active conformations that signal to diverse effectors and are likely regulated by different mechanisms. Thus, the identification of the molecular machinery important for PAR signal regulation will enable the development of new strategies to manipulate receptor signalling and will provide novel targets for the development of drugs.
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Affiliation(s)
- Unice J K Soh
- Department of Pharmacology, University of California, San Diego, 92093-0636, USA
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27
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Soto AG, Trejo J. N-linked glycosylation of protease-activated receptor-1 second extracellular loop: a critical determinant for ligand-induced receptor activation and internalization. J Biol Chem 2010; 285:18781-93. [PMID: 20368337 DOI: 10.1074/jbc.m110.111088] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor-1 (PAR1) contains five N-linked glycosylation consensus sites as follows: three residing in the N terminus and two localized on the surface of the second extracellular loop (ECL2). To study the effect of N-linked glycosylation in the regulation of PAR1 signaling and trafficking, we generated mutants in which the critical asparagines of the consensus sites were mutated. Here, we report that both the PAR1 N terminus and ECL2 serve as sites for N-linked glycosylation but have different functions in the regulation of receptor signaling and trafficking. N-Linked glycosylation of the PAR1 N terminus is important for transport to the cell surface, whereas the PAR1 mutant lacking glycosylation at ECL2 (NA ECL2) trafficked to the cell surface like the wild-type receptor. However, activated PAR1 NA ECL2 mutant internalization was impaired compared with wild-type receptor, whereas constitutive internalization of unactivated receptor remained intact. Remarkably, thrombin-activated PAR1 NA ECL2 mutant displayed an enhanced maximal signaling response compared with wild-type receptor. The increased PAR1 NA ECL2 mutant signaling was not due to defects in the ability of thrombin to cleave the receptor or signal termination mechanisms. Rather, the PAR1 NA ECL2 mutant displayed a greater efficacy in thrombin-stimulated G protein signaling. Thus, N-linked glycosylation of the PAR1 extracellular surface likely influences ligand docking interactions and the stability of the active receptor conformation. Together, these studies strongly suggest that N-linked glycosylation of PAR1 at the N terminus versus the surface of ECL2 serves distinct functions critical for proper regulation of receptor trafficking and the fidelity of thrombin signaling.
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Affiliation(s)
- Antonio G Soto
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0636, USA
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28
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Swift S, Xu J, Trivedi V, Austin KM, Tressel SL, Zhang L, Covic L, Kuliopulos A. A novel protease-activated receptor-1 interactor, Bicaudal D1, regulates G protein signaling and internalization. J Biol Chem 2010; 285:11402-10. [PMID: 20164183 DOI: 10.1074/jbc.m110.105403] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Protease-activated receptor-1 (PAR1) is a G protein-coupled receptor that plays critical roles in cancer, angiogenesis, inflammation, and thrombosis. Proteolytic cleavage of the extracellular domain of PAR1 generates a tethered ligand that activates PAR1 in an unusual intramolecular mode. The signal emanating from the irreversibly cleaved PAR1 is terminated by G protein uncoupling and internalization; however, the mechanisms of PAR1 signal shut off still remain unclear. Using a yeast two-hybrid screen, we identified Bicaudal D1 (BicD1) as a direct interactor with the C-terminal cytoplasmic domain of PAR1. BICD was originally identified as an essential developmental gene associated with mRNA and Golgi-endoplasmic reticulum transport. We discovered a novel function of BicD1 in the modulation of G protein signaling, cell proliferation, and endocytosis downstream of PAR1. BicD1 and its C-terminal CC3 domain inhibited PAR1 signaling to G(q)-phospholipase C-beta through coiled-coil interactions with the cytoplasmic 8th helix of PAR1. Unexpectedly, BicD1 was also found to be a potent suppressor of PAR1-driven proliferation of breast carcinoma cells. The growth-suppressing effects of BicD1 required the ability to interact with the 8th helix of PAR1. Silencing of BicD1 expression impaired endocytosis of PAR1, and BicD1 co-localized with PAR1 and tubulin, implicating BicD1 as an important adapter protein involved in the transport of PAR1 from the plasma membrane to endosomal vesicles. Together, these findings provide a link between PAR1 signal termination and internalization through the non-G protein effector, BicD1.
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Affiliation(s)
- Steven Swift
- Molecular Oncology Research Institute, Tufts Medical Center, and Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Ricks TK, Trejo J. Phosphorylation of protease-activated receptor-2 differentially regulates desensitization and internalization. J Biol Chem 2009; 284:34444-57. [PMID: 19815543 DOI: 10.1074/jbc.m109.048942] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor 2 (PAR2) is a G protein-coupled receptor irreversibly activated by extracellular proteases. Activated PAR2 couples to multiple heterotrimeric G-protein subtypes including G alpha(q), G alpha(i), and G alpha(12/13). Most activated G protein-coupled receptors are rapidly desensitized and internalized following phosphorylation and beta-arrestin binding. However, the role of phosphorylation in regulation of PAR2 signaling and trafficking is not known. To investigate the function of phosphorylation, we generated a PAR2 mutant in which all serines and threonines in the C-tail were converted to alanines and designated it PAR2 0P. In mammalian cells, the addition of agonist induced a rapid and robust increase in phosphorylation of wild-type PAR2 but not the 0P mutant, suggesting that the major sites of phosphorylation occur within the C-tail domain. Moreover, desensitization of PAR2 0P signaling was markedly impaired compared with the wild-type receptor. Wild-type phosphorylated PAR2 internalized through a canonical dynamin, clathrin- and beta-arrestin-dependent pathway. Strikingly, PAR2 0P mutant internalization proceeded through a dynamin-dependent but clathrin- and beta-arrestin-independent pathway in both a constitutive and agonist-dependent manner. Collectively, our studies show that PAR2 phosphorylation is essential for beta-arrestin binding and uncoupling from heterotrimeric G-protein signaling and that the presence of serine and threonine residues in the PAR2 C-tail hinder constitutive internalization through a non-canonical pathway. Thus, our studies reveal a novel function for phosphorylation that differentially regulates PAR2 desensitization and endocytic trafficking.
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Affiliation(s)
- Tiffany K Ricks
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7365, USA
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31
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Protease-activated receptors as drug targets in inflammation and pain. Pharmacol Ther 2009; 123:292-309. [PMID: 19481569 DOI: 10.1016/j.pharmthera.2009.05.004] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Accepted: 05/05/2009] [Indexed: 12/12/2022]
Abstract
Proteases have been shown to signal to cells through the activation of a novel class of receptors coupled to G proteins: the protease-activated receptors (PARs). Those receptors are expressed in a wide range of cells, which ultimately are all involved in mechanisms of inflammation and pain. Numerous studies have considered the role of PARs in cells, organ systems or in vivo, highlighting the fact that PAR activation results in signs of inflammation. A growing body of evidences discussed here suggests that these receptors, and the proteases that activate them, interfere with inflammation and pain processes. Whether a role for PARs has been clearly defined in inflammatory and pain pathologies is discussed in this review. Further, the pros and cons for considering PARs as targets for the development of therapeutic options for the treatment of inflammation and pain are discussed.
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32
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Sun Y, Lee JH, Kim NH, Lee CW, Kim MJ, Kim SH, Huh SO. Lysophosphatidylcholine-induced apoptosis in H19-7 hippocampal progenitor cells is enhanced by the upregulation of Fas Ligand. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:61-8. [DOI: 10.1016/j.bbalip.2008.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 09/18/2008] [Accepted: 09/30/2008] [Indexed: 11/15/2022]
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33
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Critical role for endocytosis in the regulation of signaling by the Kaposi's sarcoma-associated herpesvirus K1 protein. J Virol 2008; 82:6514-23. [PMID: 18434405 DOI: 10.1128/jvi.02637-07] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a member of the gammaherpesvirus family. KSHV is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. The first open reading frame of the KSHV genome encodes a type 1 transmembrane glycoprotein named K1. K1 is structurally similar to the B-cell receptor (BCR), and its cytoplasmic tail contains an immunoreceptor tyrosine-based activation motif that can activate Syk kinase and the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Recent evidence suggests that receptor signaling occurs not only at the cell membrane, but from intracellular compartments as well. We have found that K1 is internalized in a clathrin-dependent manner, and efficient internalization is coupled to its signaling function. Once internalized, K1 traffics from the early endosome to the recycling endosome. Interestingly, blocking K1's activation of Syk and PI3K prevents K1 from internalizing. We have also found that blocking clathrin-mediated endocytosis prevents downstream signaling by K1. These results strongly suggest that internalization of K1 is intimately associated with normal signaling. When K1 internalization was examined in B lymphocytes, we found that K1 cointernalized with the BCR. Altogether, these results suggest that K1's signaling function is tightly coupled to its internalization.
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34
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Arora P, Ricks TK, Trejo J. Protease-activated receptor signalling, endocytic sorting and dysregulation in cancer. J Cell Sci 2007; 120:921-8. [PMID: 17344429 DOI: 10.1242/jcs.03409] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Protease-activated receptors (PARs) are G-protein-coupled receptors (GPCRs) that are activated by a unique proteolytic mechanism. PARs play crucial roles in hemostasis and thrombosis, as well as in inflammation and vascular development. Coagulant proteases, which are generated at sites of vascular injury, act mainly through PARs to elicit signalling in a variety of cell types. Since PARs are irreversibly activated signalling must be tightly regulated. Desensitization and trafficking of proteolytically activated PARs control the magnitude, duration and spatial aspects of receptor signalling. Recent studies have revealed novel endocytic sorting mechanisms that regulate PAR signalling. PARs have also been implicated in tumor progression. PARs are overexpressed in several types of malignant cancer, transmit signals in response to tumor-generated proteases and promote tumor growth, invasion and metastasis. Recent work also indicates that matrix metalloprotease 1 (MMP-1) signals through PAR1 to promote tumor growth and invasion. In addition to PAR overexpression, tumor cells display aberrant PAR1 trafficking, which causes persistent signalling and cellular invasion. Thus, a novel type of gain-of-function in GPCR signalling in cancer can be acquired through dysregulation of receptor trafficking.
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Affiliation(s)
- Puneeta Arora
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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35
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Wolfe BL, Marchese A, Trejo J. Ubiquitination differentially regulates clathrin-dependent internalization of protease-activated receptor-1. ACTA ACUST UNITED AC 2007; 177:905-16. [PMID: 17535965 PMCID: PMC2064289 DOI: 10.1083/jcb.200610154] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protease-activated receptor-1 (PAR1), a G protein–coupled receptor (GPCR) for thrombin, is irreversibly activated by proteolysis. Consequently, PAR1 trafficking is critical for the fidelity of thrombin signaling. PAR1 displays constitutive and agonist-induced internalization, which are clathrin and dynamin dependent but are independent of arrestins. The clathrin adaptor AP2 (adaptor protein complex-2) is critical for constitutive but not for activated PAR1 internalization. In this study, we show that ubiquitination negatively regulates PAR1 constitutive internalization and specifies a distinct clathrin adaptor requirement for activated receptor internalization. PAR1 is basally ubiquitinated and deubiquitinated after activation. A PAR1 lysineless mutant signaled normally but was not ubiquitinated. Constitutive internalization of ubiquitin (Ub)-deficient PAR1 was markedly increased and inhibited by the fusion of Ub to the cytoplasmic tail. Ub-deficient PAR1 constitutive internalization was AP2 dependent like the wild-type receptor. However, unlike wild-type PAR1, AP2 was required for the internalization of activated Ub-deficient receptor, suggesting that the internalization of ubiquitinated PAR1 requires different endocytic machinery. These studies reveal a novel function for ubiquitination in the regulation of GPCR internalization.
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Affiliation(s)
- Breann L Wolfe
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, NC 27599, USA
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36
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Kuo FT, Lu TL, Fu HW. Opposing effects of β-arrestin1 and β-arrestin2 on activation and degradation of Src induced by protease-activated receptor 1. Cell Signal 2006; 18:1914-23. [PMID: 16580177 DOI: 10.1016/j.cellsig.2006.02.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 02/15/2006] [Accepted: 02/15/2006] [Indexed: 10/25/2022]
Abstract
Protease-activated receptor 1 (PAR1), a G protein-coupled receptor for thrombin, is irreversibly proteolytically activated. beta-Arrestin1 and beta-arrestin2 have been reported to have different effects on signal desensitization and transduction of PAR1. In this study, we investigated whether beta-arrestin1 and beta-arrestin2 regulate Src-dependent activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) induced by PAR1 in HEK 293 cells. Our results show that PAR1-mediated activation of Src and ERK1/2 in HEK 293 cells was increased with overexpression of beta-arrestin1 or depletion of beta-arrestin2. PAR1-mediated activation of Src and ERK1/2 in HEK 293 cells was decreased or eliminated with depletion of beta-arrestin1 or overexpression of beta-arrestin2. Furthermore, depletion of beta-arrestin2 blocked PAR1-induced degradation of Src. Thus, beta-arrestin1 and beta-arrestin2 have opposing roles in regulating the activation of Src induced by PAR1. beta-Arrestin2 also appears to promote PAR1-induced degradation of Src. This degradation of Src provides a possible mechanism for terminating PAR1 signaling.
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Affiliation(s)
- Fang-Ting Kuo
- Institute of Molecular and Cellular Biology, Hsinchu 30013, Taiwan ROC
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37
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Lu TL, Kuo FT, Lu TJ, Hsu CY, Fu HW. Negative regulation of protease-activated receptor 1-induced Src kinase activity by the association of phosphocaveolin-1 with Csk. Cell Signal 2006; 18:1977-87. [PMID: 16678999 DOI: 10.1016/j.cellsig.2006.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 03/05/2006] [Accepted: 03/06/2006] [Indexed: 11/18/2022]
Abstract
Protease-activated receptor 1 (PAR1), a G protein-coupled receptor (GPCR) for thrombin, has been correlated with cell proliferation. PAR1 is activated by the irreversibly proteolytic cleavage, internalized via clathrin-coated pits, and then sorted to lysosomes for degradation. Caveolae play important roles in both signaling transduction and internalization of several GPCRs. However, the role of caveolae in cellular signaling and trafficking of PAR1 is still unclear. In this study, we show that PAR1 was partially localized in caveolae. Disruption of caveolae by cholesterol depletion did not inhibit PAR1 internalization, indicating that internalization of PAR1 was not via caveolae. Of interest, activation of PAR1 resulted in the phosphorylation of caveolin-1, a principal component of caveolae, on tyrosine 14 by a Gi-linked Src kinase pathway and p38 mitogen-activated protein kinase. Analysis of immunoprecipitates from cells stimulated by PAR1 showed that phosphocaveolin-1 but not caveolin-1 with mutation at tyrosine 14 could bind to Csk. In addition, phosphocaveolin-1 could not bind to CskS109C mutant with the defective SH2 domain. These results indicated that phosphocaveolin-1 was associated with the SH2 domain of Csk in response to PAR1 activation. The association further resulted in a rapid decrease in Src kinase activity. Thus, PAR1-induced Src activation is negatively regulated by recruiting Csk through phosphocaveolin-1. Our results also reveal that phosphocaveolin-1 represents a novel effector of PAR1 to downregulate Src kinase activity. The downregulation of PAR1-induced Src activation mediated by phosphocaveolin-1 provides an additional mechanism for the termination of PAR1 signaling at its downstream molecules.
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Affiliation(s)
- Te-Ling Lu
- Department of Life Science, National Tsing Hua University, 101 Section 2 Kuang Fu Road, Hsinchu 30013, Taiwan, ROC
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38
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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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Gullapalli A, Wolfe BL, Griffin CT, Magnuson T, Trejo J. An essential role for SNX1 in lysosomal sorting of protease-activated receptor-1: evidence for retromer-, Hrs-, and Tsg101-independent functions of sorting nexins. Mol Biol Cell 2006; 17:1228-38. [PMID: 16407403 PMCID: PMC1382312 DOI: 10.1091/mbc.e05-09-0899] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting nexin 1 (SNX1) and SNX2 are the mammalian homologues of the yeast Vps5p retromer component that functions in endosome-to-Golgi trafficking. SNX1 is also implicated in endosome-to-lysosome sorting of cell surface receptors, although its requirement in this process remains to be determined. To assess SNX1 function in endocytic sorting of protease-activated receptor-1 (PAR1), we used siRNA to deplete HeLa cells of endogenous SNX1 protein. PAR1, a G-protein-coupled receptor, is proteolytically activated by thrombin, internalized, sorted predominantly to lysosomes, and efficiently degraded. Strikingly, depletion of endogenous SNX1 by siRNA markedly inhibited agonist-induced PAR1 degradation, whereas expression of a SNX1 siRNA-resistant mutant protein restored agonist-promoted PAR1 degradation in cells lacking endogenous SNX1, indicating that SNX1 is necessary for lysosomal degradation of PAR1. SNX1 is known to interact with components of the mammalian retromer complex and Hrs, an early endosomal membrane-associated protein. However, activated PAR1 degradation was not affected in cells depleted of retromer Vps26/Vps35 subunits, Hrs or Tsg101, an Hrs-interacting protein. We further show that SNX2, which dimerizes with SNX1, is not essential for lysosomal sorting of PAR1, but rather can regulate PAR1 degradation by disrupting endosomal localization of endogenous SNX1 when ectopically expressed. Together, our findings establish an essential role for endogenous SNX1 in sorting activated PAR1 to a distinct lysosomal degradative pathway that is independent of retromer, Hrs, and Tsg101.
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Affiliation(s)
- Anuradha Gullapalli
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599-7365, USA
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40
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Hyman T, Shmuel M, Altschuler Y. Actin is required for endocytosis at the apical surface of Madin-Darby canine kidney cells where ARF6 and clathrin regulate the actin cytoskeleton. Mol Biol Cell 2005; 17:427-37. [PMID: 16251360 PMCID: PMC1345679 DOI: 10.1091/mbc.e05-05-0420] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In epithelial cell lines, apical but not basolateral clathrin-mediated endocytosis has been shown to be affected by actin-disrupting drugs. Using electron and fluorescence microscopy, as well as biochemical assays, we show that the amount of actin dedicated to endocytosis is limiting at the apical surface of epithelia. In part, this contributes to the low basal rate of clathrin-dependent endocytosis observed at this epithelial surface. ARF6 in its GTP-bound state triggers the recruitment of actin from the cell cortex to the clathrin-coated pit to enable dynamin-dependent endocytosis. In addition, we show that perturbation of the apical endocytic system by expression of a clathrin heavy-chain mutant results in the collapse of microvilli. This phenotype was completely reversed by the expression of an ARF6-GTP-locked mutant. These observations indicate that concomitant to actin recruitment, the apical clathrin endocytic system is deeply involved in the morphology of the apical plasma membrane.
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Affiliation(s)
- Tehila Hyman
- Department of Pharmacology School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem-Ein Kerem Campus, Jerusalem 91120, Israel
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41
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Saito T, Bunnett NW. Protease-activated receptors: regulation of neuronal function. Neuromolecular Med 2005; 7:79-99. [PMID: 16052040 DOI: 10.1385/nmm:7:1-2:079] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Revised: 02/13/2005] [Accepted: 02/17/2005] [Indexed: 12/20/2022]
Abstract
Certain serine proteases from the circulation (e.g., coagulation factors), inflammatory cells (e.g., mast-cell tryptase, neutrophil proteinase 3), and from many other cell types (e.g., trypsins) can specifically signal to cells by cleaving protease-activated receptors (PARs), a family of four G protein-coupled receptors. Proteases cleave PARs at specific sites within the extracellular amino-terminus to expose amino-terminal tethered ligand domains that bind to and activate the cleaved receptors. The proteases that activate PARs are often generated and released during injury and inflammation, and activated PARs orchestrate tissue responses to injury, including hemostasis, inflammation, pain, and repair. This review concerns protease and PAR signaling in the nervous system. Neurons of the central and peripheral nervous systems express all four PARs. Proteases that may derive from the circulation, inflammatory cells, or neural tissues can cleave PARs on neurons and thereby activate diverse signaling pathways that control survival, morphology, release of neurotransmitters, and activity of ion channels. In this manner proteases and PARs regulate neurodegeneration, neurogenic inflammation, and pain transmission. Thus, PARs may participate in disease states and PAR antagonists or agonists may be useful therapies for certain disorders.
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Affiliation(s)
- Toshiyuki Saito
- Department of Surgery, University of California, San Francisco, CA, USA
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Suvorova ES, Gripentrog JM, Miettinen HM. Different Endocytosis Pathways of the C5a Receptor and the N-formyl Peptide Receptor. Traffic 2004; 6:100-15. [PMID: 15634211 DOI: 10.1111/j.1600-0854.2004.00256.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Two chemoattractant receptors, C5aR (the complement fragment C5a receptor) and FPR (the N-formyl peptide receptor), are involved in neutrophil activation at sites of inflammation. In this study, we found major differences in the intracellular trafficking of the receptors in transfected Chinese hamster ovary (CHO) cells. Western blot analysis showed that FPR was stable during a 3 h stimulation with ligand, but C5aR was reduced in quantity by 50%. Not all C5aR was targeted directly for degradation however; a small, but visible fraction of the receptor became re-phosphorylated upon subsequent addition of ligand, suggesting that some of the receptor had cycled to the cell surface. Light membrane fractions isolated from activated cells showed C5aR distribution at the bottom of a glycerol gradient, colocalizing with the main distribution of the late endosomal/lysosomal marker LAMP2, whereas FPR was found at the bottom of the gradient as well as in the middle of the gradient, where it cofractionated with the early/sorting endosomal marker Rab5. Using fluorescence microscopy, we observed ligand-dependent redistribution of C5aR-EGFP from the plasma membrane to LAMP2-positive compartments, whereas FPR-EGFP showed significant colocalization with the early/sorting endosomes. Analysis of endogenous C5aR and FPR in neutrophils revealed a pattern similar to the CHO transfectants: C5aR underwent degradation after prolonged ligand stimulation, while FPR did not. Finally, we confirmed the down-regulation of C5aR in a functional assay by showing reduced chemotaxis toward C5a in both CHO transfectants and neutrophils after preincubation with C5a. A similar decrease in FPR-mediated chemotaxis was not observed.
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Affiliation(s)
- Elena S Suvorova
- Department of Microbiology, Montana State University, Bozeman, MT 59717-3520, USA
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Stalheim L, Ding Y, Gullapalli A, Paing MM, Wolfe BL, Morris DR, Trejo J. Multiple independent functions of arrestins in the regulation of protease-activated receptor-2 signaling and trafficking. Mol Pharmacol 2004; 67:78-87. [PMID: 15475570 DOI: 10.1124/mol.104.006072] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The irreversible proteolytic nature of protease-activated receptor-2 (PAR2) activation suggests that mechanism(s) responsible for termination of receptor signaling are critical determinants of the magnitude and duration of PAR2-elicited cellular responses. Rapid desensitization of activated G-protein-coupled receptors (GPCRs) involves both phosphorylation and binding of arrestins. Arrestins also function as scaffolds and transducers of mitogen-activated protein (MAP) kinase signaling cascades. The PAR2 cytoplasmic tail (C-tail) contains multiple sites of phosphorylation and may be an important determinant for arrestin interaction. Desensitization and internalization of activated PAR2 were markedly impaired in arrestin-deficient cells compared with wild-type control cells. PAR2 C-tail truncation mutants displayed normal agonist-induced internalization, caused rapid distribution of betaarr2-GFP to the plasma membrane, and desensitized in an arrestin-dependent manner similar to that of wild-type PAR2. It is interesting that PAR2 C-tail mutants lost the capacity to stably associate with arrestins and consequently, redistributed to endocytic vesicles without betaarr2-GFP, whereas internalized wild-type PAR2 remained stably associated with betaarr2-GFP in endosomes. Moreover, activated PAR2 caused rapid and prolonged activation of endogenous extracellular signal-regulated kinase (ERK1/2). It was striking that in arrestin-deficient cells, activated PAR2 induced an initial peak in ERK1/2 activity that rapidly declined. The inability of internalized PAR2 C-tail mutants to stably associate with arrestins also resulted in loss of prolonged ERK2 activation. Thus, the PAR2 C-tail regulates the stability of arrestin interaction and kinetics of ERK1/2 activation but is not essential for desensitization or internalization. These findings further suggest that the diverse functions of arrestins in regulating PAR2 signaling and trafficking are controlled by multiple independent interactions involving both the intracellular loops and the C-tail.
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Affiliation(s)
- Lisa Stalheim
- 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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Paing MM, Temple BRS, Trejo J. A tyrosine-based sorting signal regulates intracellular trafficking of protease-activated receptor-1: multiple regulatory mechanisms for agonist-induced G protein-coupled receptor internalization. J Biol Chem 2004; 279:21938-47. [PMID: 15023990 DOI: 10.1074/jbc.m401672200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protease-activated receptor-1 (PAR1), a G protein-coupled receptor (GPCR) for thrombin, is irreversibly proteolytically activated, internalized, and then sorted to lysosomes and degraded. Internalization and lysosomal sorting of activated PAR1 is critical for termination of receptor signaling. We previously demonstrated that activated PAR1 is rapidly phosphorylated and internalized via a clathrin- and dynamin-dependent pathway that is independent of arrestins. Toward understanding the mechanisms responsible for activated PAR1 internalization through clathrin-coated pits we examined the function of a highly conserved tyrosine-based motif, YXXL, localized in the cytoplasmic carboxyl tail of the receptor. A mutant PAR1 in which tyrosine 383 and leucine 386 were replaced with alanines (Y383A/L386A) was significantly impaired in agonist-triggered internalization and degradation compared with wild-type receptor. In contrast, constitutive internalization, and recycling of unactivated PAR1 Y383A/L386A mutant was not affected, suggesting that tonic cycling of the mutant receptor remained intact. Strikingly, a PAR1 C387Z truncation mutant in which the YXXL motif was exposed at the C terminus constitutively internalized and degraded in an agonist-independent manner, whereas C387Z truncation mutant in which the critical tyrosine and leucine were mutated to alanine (C387Z-Y383A/L386A) failed to internalize. Inhibition of PAR1 C387Z mutant constitutive internalization with dominant-negative K44A dynamin blocked agonist-independent degradation of the mutant receptor. Together these findings strongly suggest that internalization of activated PAR1 is controlled by multiple regulatory mechanisms involving phosphorylation and a highly conserved tyrosine-based motif, YXXL. This study is the first to describe a function for a tyrosine-based motif, YXX, in GPCR internalization and reveal novel complexities in the regulation of GPCR trafficking.
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Affiliation(s)
- May M Paing
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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Booden MA, Eckert LB, Der CJ, Trejo J. Persistent signaling by dysregulated thrombin receptor trafficking promotes breast carcinoma cell invasion. Mol Cell Biol 2004; 24:1990-9. [PMID: 14966279 PMCID: PMC350540 DOI: 10.1128/mcb.24.5.1990-1999.2004] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Increased expression of protease-activated receptor 1 (PAR1), a G protein-coupled receptor for thrombin, has previously been correlated with breast carcinoma cell invasion. PAR1 is irreversibly proteolytically activated, internalized, and sorted directly to lysosomes, a critical process for the termination of signaling. We determined that activated PAR1 trafficking is severely altered in metastatic breast carcinoma cells but not in nonmetastatic or normal breast epithelial cells. Consequently, the proteolytically activated receptor is not sorted to lysosomes and degraded. Altered trafficking of proteolytically activated PAR1 caused sustained activation of phosphoinositide hydrolysis and extracellular signal-regulated kinase signaling, even after thrombin withdrawal, and enhanced cellular invasion. Thus, our results reveal that a novel alteration in trafficking of activated PAR1 causes persistent signaling and, in addition to other processes and proteins, contributes to breast carcinoma cell invasion.
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Affiliation(s)
- Michelle A Booden
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295, USA
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Abstract
Proteases acting at the surface of cells generate and destroy receptor agonists and activate and inactivate receptors, thereby making a vitally important contribution to signal transduction. Certain serine proteases that derive from the circulation (e.g., coagulation factors), inflammatory cells (e.g., mast cell and neutrophil proteases), and from multiple other sources (e.g., epithelial cells, neurons, bacteria, fungi) can cleave protease-activated receptors (PARs), a family of four G protein-coupled receptors. Cleavage within the extracellular amino terminus exposes a tethered ligand domain, which binds to and activates the receptors to initiate multiple signaling cascades. Despite this irreversible mechanism of activation, signaling by PARs is efficiently terminated by receptor desensitization (receptor phosphorylation and uncoupling from G proteins) and downregulation (receptor degradation by cell-surface and lysosomal proteases). Protease signaling in tissues depends on the generation and release of proteases, availability of cofactors, presence of protease inhibitors, and activation and inactivation of PARs. Many proteases that activate PARs are produced during tissue damage, and PARs make important contributions to tissue responses to injury, including hemostasis, repair, cell survival, inflammation, and pain. Drugs that mimic or interfere with these processes are attractive therapies: selective agonists of PARs may facilitate healing, repair, and protection, whereas protease inhibitors and PAR antagonists can impede exacerbated inflammation and pain. Major future challenges will be to understand the role of proteases and PARs in physiological control mechanisms and human diseases and to develop selective agonists and antagonists that can be used to probe function and treat disease.
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Gullapalli A, Garrett TA, Paing MM, Griffin CT, Yang Y, Trejo J. A role for sorting nexin 2 in epidermal growth factor receptor down-regulation: evidence for distinct functions of sorting nexin 1 and 2 in protein trafficking. Mol Biol Cell 2004; 15:2143-55. [PMID: 14978220 PMCID: PMC404011 DOI: 10.1091/mbc.e03-09-0711] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting nexin 1 (SNX1) and SNX2, homologues of the yeast vacuolar protein-sorting (Vps)5p, contain a phospholipid-binding motif termed the phox homology (PX) domain and a carboxyl terminal coiled-coil region. A role for SNX1 in trafficking of cell surface receptors from endosomes to lysosomes has been proposed; however, the function of SNX2 remains unknown. Toward understanding the function of SNX2, we first examined the distribution of endogenous protein in HeLa cells. We show that SNX2 resides primarily in early endosomes, whereas SNX1 is found partially in early endosomes and in tubulovesicular-like structures distributed throughout the cytoplasm. We also demonstrate that SNX1 interacts with the mammalian retromer complex through its amino terminal domain, whereas SNX2 does not. Moreover, activated endogenous epidermal growth factor receptor (EGFR) colocalizes markedly with SNX2-positive endosomes, but minimally with SNX1-containing vesicles. To assess SNX2 function, we examined the effect of a PX domain-mutated SNX2 that is defective in vesicle localization on EGFR trafficking. Mutant SNX2 markedly inhibited agonist-induced EGFR degradation, whereas internalization remained intact. In contrast, SNX1 PX domain mutants failed to effect EGFR degradation, whereas a SNX1 deletion mutant significantly inhibited receptor down-regulation. Interestingly, knockdown of SNX1 and SNX2 expression by RNA interference failed to alter agonist-induced EGFR down-regulation. Together, these findings suggest that both SNX1 and SNX2 are involved in regulating lysosomal sorting of internalized EGFR, but neither protein is essential for this process. These studies are the first to demonstrate a function for SNX2 in protein trafficking.
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Affiliation(s)
- Anuradha Gullapalli
- Department of Pharmacology, Cardiovascular Biology Center, Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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Trejo J. Protease-activated receptors: new concepts in regulation of G protein-coupled receptor signaling and trafficking. J Pharmacol Exp Ther 2003; 307:437-42. [PMID: 12966163 DOI: 10.1124/jpet.103.052100] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Most G protein-coupled receptors (GPCRs) are reversibly activated upon ligand binding. However, activation of protease-activated G protein-coupled receptors (PARs) occurs through an irreversible proteolytic event that results in the generation of a tethered ligand that cannot diffuse away. This unusual mode of PAR activation raises important questions regarding the mechanisms responsible for termination of receptor signaling. There are currently four members of the PAR family. Thrombin activates PAR1, PAR3, and PAR4, whereas multiple trypsin-like serine proteases activate PAR2. The regulation of signaling by PAR1 has been extensively studied, whereas considerably less is known about the other PARs. It has been demonstrated that rapid termination of PAR1 signaling is critical in determining the magnitude and kinetics of the cellular protease response. Therefore, elucidating the molecular mechanisms involved in the regulation of PAR signaling is essential to fully understand protease-mediated responses. Recent findings indicate that novel mechanisms contribute to PAR1 desensitization, internalization, and down-regulation. This review focuses on the intracellular mechanisms that regulate PAR signaling and the recent progress in developing inhibitors of PAR signaling.
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Affiliation(s)
- Joann Trejo
- University of North Carolina at Chapel Hill, Department of Pharmacology, 1106 Mary Ellen Jones Bldg., CB #7365, Chapel Hill, NC 27599-7365, USA.
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Fraile-Ramos A, Kohout TA, Waldhoer M, Marsh M. Endocytosis of the viral chemokine receptor US28 does not require beta-arrestins but is dependent on the clathrin-mediated pathway. Traffic 2003; 4:243-53. [PMID: 12694563 DOI: 10.1034/j.1600-0854.2003.00079.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Arrestins bind phosphorylated G-protein coupled-receptors (GPCR) and inhibit agonist-induced signal transduction by uncoupling the receptors from their cognate G-proteins. beta-arrestins also act as adaptors that target GPCR to endocytic clathrin-coated vesicles. Unlike cellular GPCRs, the human cytomegalovirus GPCRs and chemokine receptor, US28, shows constitutive signal transduction activity and undergoes constitutive endocytosis. To determine the role of beta-arrestins in US28 trafficking, we used embryonic fibroblasts derived from beta-arrestin knockout mice. In these cells, the internalization of transfected beta2-adrenergic receptor and of the cellular chemokine receptor CCR5 was impaired. By contrast, US28 distribution was unaffected, and US28-mediated RANTES internalization was similar in normal and knockout cell lines. To investigate whether a clathrin-mediated pathway is involved in US28 endocytosis, we developed small interfering RNA against the micro2-adaptin subunit of the AP-2 adaptor complex. In cells transfected with micro2 small interfering RNA transferrin endocytosis was severely inhibited. Antibody-feeding experiments and biochemical analysis showed that US28 internalization was also inhibited. Together, these data indicate that US28 endocytosis occurs via a clathrin-mediated mechanism but is independent of beta-arrestins.
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Affiliation(s)
- Alberto Fraile-Ramos
- Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, UK
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D'Andrea MR, Saban MR, Nguyen NB, Andrade-Gordon P, Saban R. Expression of protease-activated receptor-1, -2, -3, and -4 in control and experimentally inflamed mouse bladder. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 162:907-23. [PMID: 12598324 PMCID: PMC1868088 DOI: 10.1016/s0002-9440(10)63886-2] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Inflammation underlines all major bladder pathologies and represents a defense reaction to injury involving a mandatory participation of mast cells and sensory nerves. Mast cells are particularly frequent in close proximity to epithelial surfaces where they are strategically located in the bladder and release their mediators in response to inflammation. Tryptase is specifically produced by mast cells and modulates inflammation by activating protease-activated receptors (PARs). We recently found that PAR-4 mRNA is up-regulated in experimental bladder inflammation regardless of the initiating stimulus. Because it has been reported that PAR-1, PAR-2, and PAR-3 may also be involved in the processes of inflammation, we used immunohistochemistry to characterize the expression of all known PARs in normal, acute, and chronic inflamed mouse bladder. We found that all four PARs are present in the control mouse bladder, and follow a unique distribution. All four PARs are co-expressed in the urothelium, whereas PAR-1 and PAR-2 are predominant in the detrusor muscle, and PAR-4 is expressed in peripheral nerves and plexus cell bodies. The strong expression of PARs in the detrusor muscle indicates the need for studies on the role of these receptors in motility whereas the presence of PAR-4 in nerves may indicate its participation in neurogenic inflammation. In addition, PARs are differentially modulated during inflammation. PAR-1 and PAR-2 are down-regulated in acute inflammation whereas PAR-3 and PAR-4 are up-regulated. Bladder fibroblasts were found to present a clear demarcation in PAR expression secondary to acute and chronic inflammation. Our findings provide evidence of participation of PARs in the urinary system, provide a working model for mast cell tryptase signaling in the mouse bladder, and evoke testable hypotheses regarding the roles of PARs in bladder inflammation. It is timely to understand the role of tryptase signaling and PARs in the context of bladder biology.
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Affiliation(s)
- Michael R D'Andrea
- Johnson and Johnson Pharmaceutical Research and Development, Spring House, Pennsylvania, USA
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