title: N-terminal processing and modifications of caveolin-1 in caveolae from human adipocytes.
abstract: Caveolin, the principal structural protein of caveolae membrane domains, has a cytosol-exposed N-terminal part that was cleaved off by trypsin treatment of caveolae vesicles isolated from primary human adipocytes. Sequencing of the released tryptic peptides by nanospray quadrupole time-of-flight mass spectrometry revealed that both caveolin-1alpha and caveolin-1beta were processed by excision of the starting methionines. The N-terminus of the mature caveolin-1alpha was acetylated, while caveolin-1beta was found in acetylated as well as in non-acetylated forms. Fractional phosphorylation of serine-36 in the mature caveolin-1alpha and of the homologous serine-5 in caveolin-1beta was identified. This is the first experimental evidence for in vivo phosphorylation of caveolin-1 at the consensus site for phosphorylation by protein kinase C. The phosphorylation was found in both the acetylated and non-acetylated variants of caveolin-1beta. This variability in modifications is consistent with critical involvement of the N-terminal domain of caveolin in the regulation of caveolae.
authors.affiliation: Division of Cell Biology, Faculty of Health Sciences, Linköping University, SE 58185, Linköping, Sweden.
authors.forename: Julia P
authors.initials: JP
authors.lastname: Vainonen
authors.forename: Nabila
authors.initials: N
authors.lastname: Aboulaich
authors.forename: Maria V
authors.initials: MV
authors.lastname: Turkina
authors.forename: Peter
authors.initials: P
authors.lastname: Strålfors
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Vener
mesh_terms: D000107:Acetylation; D017667:Adipocytes / Q000378:metabolism*; D000595:Amino Acid Sequence; D015153:Blotting, Western; D021941:Caveolae / Q000378:metabolism*; D051242:Caveolin 1; D022461:Caveolins / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012694:Serine / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D020033:Protein Isoforms; D012694:Serine