title: Caveolin-1 loss of function accelerates glucose transporter 4 and insulin receptor degradation in 3T3-L1 adipocytes.
abstract: Caveolae are a specialized type of lipid rafts that are stabilized by oligomers of caveolin protein. Caveolae are particularly enriched in adipocytes. Here we analyzed the effects of caveolin-1 knockdown and caveolae ablation on adipocyte function. To this end, we obtained several multiclonal mouse 3T3-L1 cell lines with a reduced expression of caveolin-1 (95% reduction) by a small interfering RNA approach using lentiviral vectors. Control cell lines were obtained by lentiviral infection with lentiviral vectors encoding appropriate scrambled RNAs. Caveolin-1 knockdown adipocytes showed a drastic reduction in the number of caveolae (95% decrease) and cholera toxin labeling was reorganized in dynamic plasma membrane microdomains. Caveolin-1 depletion caused a specific decrease in glucose transporter 4 (GLUT4) and insulin receptor protein levels. This reduction was not the result of a generalized defect in adipocyte differentiation or altered gene expression but was explained by faster degradation of these proteins. Caveolin-1 knockdown adipocytes showed reductions in insulin-stimulated glucose transport, insulin-triggered GLUT4 recruitment to the cell surface, and insulin receptor activation. In all, our data indicate that caveolin-1 loss of function reduces maximal insulin response through lowered stability and diminished expression of insulin receptors and GLUT4. We propose that caveolin-1/caveolae control insulin action in adipose cells.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Institute for Research in Biomedicine (IRB Barcelona), Serveis Cientifico-Tècnics, Universitat de Barcelona, 08028 Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: González-Muñoz
authors.forename: Carmen
authors.initials: C
authors.lastname: López-Iglesias
authors.forename: Maria
authors.initials: M
authors.lastname: Calvo
authors.forename: Manuel
authors.initials: M
authors.lastname: Palacín
authors.forename: Antonio
authors.initials: A
authors.lastname: Zorzano
authors.forename: Marta
authors.initials: M
authors.lastname: Camps
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D021941:Caveolae / Q000378:metabolism / Q000648:ultrastructure; D051242:Caveolin 1 / Q000235:genetics / Q000502:physiology*; D036681:Fluorescence Recovery After Photobleaching; D005455:Fluorescent Antibody Technique; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D047468:Immunoprecipitation; D007328:Insulin / Q000494:pharmacology; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D046529:Microscopy, Electron, Transmission; D034741:RNA, Small Interfering; D011972:Receptor, Insulin / Q000378:metabolism*
chemical_list: D051242:Caveolin 1; D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; D007328:Insulin; D034741:RNA, Small Interfering; C495693:Slc2a4 protein, mouse; D011972:Receptor, Insulin