Lipid Raft-dependent Glucagon-like Peptide-2 Receptor Trafficking Occurs Independently of Agonist-induced Desensitization
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- Jennifer L. Estall
- Departments of Laboratory Medicine and Pathobiology, and Medicine, University of Toronto, The Banting and Best Diabetes Centre, Toronto General Hospital, Toronto, Canada M5G 2C4
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- Bernardo Yusta
- Departments of Laboratory Medicine and Pathobiology, and Medicine, University of Toronto, The Banting and Best Diabetes Centre, Toronto General Hospital, Toronto, Canada M5G 2C4
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- Daniel J. Drucker
- Departments of Laboratory Medicine and Pathobiology, and Medicine, University of Toronto, The Banting and Best Diabetes Centre, Toronto General Hospital, Toronto, Canada M5G 2C4
抄録
<jats:p>The intestinotrophic and cytoprotective actions of glucagon-like peptide-2 (GLP-2) are mediated by the GLP-2 receptor (GLP-2R), a member of the class II glucagon-secretin G protein-coupled receptor superfamily. Although native GLP-2 exhibits a short circulating half-life, long-acting degradation-resistant GLP-2 analogues are being evaluated for therapeutic use in human subjects. Accordingly, we examined the mechanisms regulating signaling, internalization, and trafficking of the GLP-2R to identify determinants of receptor activation and desensitization. Heterologous cells expressing the transfected rat or human GLP-2R exhibited a rapid, dose-dependent, and prolonged desensitization of the GLP-2–stimulated cAMP response and a sustained GLP-2–induced decrease in levels of cell surface receptor. Surprisingly, inhibitors of clathrin-dependent endocytosis failed to significantly decrease GLP-2R internalization, whereas cholesterol sequestration inhibited ligand-induced receptor internalization and potentiated homologous desensitization. The hGLP-2R localized to both Triton X-100–soluble and –insoluble (lipid raft) cellular fractions and colocalized transiently with the lipid raft marker caveolin-1. Although GLP-2R endocytosis was dependent on lipid raft integrity, the receptor transiently associated with green fluorescent protein tagged-early endosome antigen 1–positive vesicles and inhibitors of endosomal acidification attenuated the reappearance of the GLP-2R on the cell surface. Our data demonstrate that GLP-2R desensitization and raft-dependent trafficking represent distinct and independent cellular mechanisms and provide new evidence implicating the importance of a clathrin- and dynamin-independent, lipid raft-dependent pathway for homologous G protein-coupled receptor internalization.</jats:p>
収録刊行物
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- Molecular Biology of the Cell
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Molecular Biology of the Cell 15 (8), 3673-3687, 2004-08
American Society for Cell Biology (ASCB)