title: Immunopurification and characterization of rat adipocyte caveolae suggest their dissociation from insulin signaling.
abstract: Adipocytes play an important role in the insulin-dependent regulation of organismal fuel metabolism and express caveolae at levels as high or higher than any other cell type. Recently, a link between insulin signaling and caveolae has been suggested; nevertheless, adipocyte caveolae have been the subject of relatively few studies, and their contents have been minimally characterized. With the aid of a new monoclonal antibody, we developed a rapid procedure for the immunoisolation of caveolae derived from the plasma membrane of adipocytes, and we characterized their protein content. We find that immunopurified adipocyte caveolae have a relatively limited protein composition, and they lack the raft protein, flotillin, and insulin receptors. Immunogold labeling and electron microscopy of the adipocyte plasma membrane confirmed the lack of insulin receptors in caveolae. In addition to caveolins, the structural components of caveolae, their major protein constituents, are the semicarbazide-sensitive amine oxidase and the scavenger lipoprotein receptor CD36. The results are consistent with a role for caveolae in lipid flux in and of adipocytes.
authors.affiliation: Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Ricardo P
authors.initials: RP
authors.lastname: Souto
authors.forename: Gino
authors.initials: G
authors.lastname: Vallega
authors.forename: Jonathan
authors.initials: J
authors.lastname: Wharton
authors.forename: Jorgen
authors.initials: J
authors.lastname: Vinten
authors.forename: Jorgen
authors.initials: J
authors.lastname: Tranum-Jensen
authors.forename: Paul F
authors.initials: PF
authors.lastname: Pilch
mesh_terms: D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D019921:Biotinylation; D015153:Blotting, Western; D018955:CD36 Antigens / Q000378:metabolism; D021941:Caveolae / Q000378:metabolism*; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011233:Precipitin Tests; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction; D013347:Subcellular Fractions
chemical_list: D000911:Antibodies, Monoclonal; D018955:CD36 Antigens; D051242:Caveolin 1; D022461:Caveolins; D007328:Insulin; D008565:Membrane Proteins; C106354:flotillins; D011972:Receptor, Insulin