title: Inhibition of lipid raft-dependent signaling by a dystrophy-associated mutant of caveolin-3.
abstract: Specific point mutations in caveolin-3, a predominantly muscle-specific member of the caveolin family, have been implicated in limb-girdle muscular dystrophy and in rippling muscle disease. We examined the effect of these mutations on caveolin-3 localization and function. Using two independent assay systems, Raf activation in fibroblasts and neurite extension in PC12 cells, we show that one of the caveolin-3 point mutants, caveolin-3-C71W, specifically inhibits signaling by activated H-Ras but not by K-Ras. To gain insights into the effect of the mutant protein on H-Ras signaling, we examined the localization of the mutant proteins in fibroblastic cells and in differentiating myotubes. Unlike the previously characterized caveolin-3-DGV mutant, the inhibitory caveolin-3-C71W mutant reached the plasma membrane and colocalized with wild type caveolins. In BHK cells, caveolin-3-C71W associated with caveolae and in differentiating muscle cells with the developing T-tubule system. In contrast, the caveolin-3-P104L mutant accumulated in the Golgi complex and had no effect on H-Ras-mediated Raf activation. Inhibition by caveolin-3-C71W was rescued by cholesterol addition, suggesting that the mutant protein perturbs cholesterol-rich raft domains. Thus, we have demonstrated that a naturally occurring caveolin-3 mutation can inhibit signaling involving cholesterol-sensitive raft domains.
authors.affiliation: Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis, and School of Biomedical Sciences, University of Queensland, Brisbane 4072, Australia.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Carozzi
authors.forename: Sandrine
authors.initials: S
authors.lastname: Roy
authors.forename: Isabel C
authors.initials: IC
authors.lastname: Morrow
authors.forename: Albert
authors.initials: A
authors.lastname: Pol
authors.forename: Bruce
authors.initials: B
authors.lastname: Wyse
authors.forename: Jodi
authors.initials: J
authors.lastname: Clyde-Smith
authors.forename: Ian A
authors.initials: IA
authors.lastname: Prior
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Nixon
authors.forename: John F
authors.initials: JF
authors.lastname: Hancock
authors.forename: Robert G
authors.initials: RG
authors.lastname: Parton
mesh_terms: D000818:Animals; D051244:Caveolin 3; D022461:Caveolins / Q000235:genetics* / Q000494:pharmacology*; D002460:Cell Line; D002784:Cholesterol / Q000494:pharmacology*; D006224:Cricetinae; D011905:Genes, ras; D006056:Golgi Apparatus / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects*; D009132:Muscles / Q000378:metabolism; D009136:Muscular Dystrophies / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D017354:Point Mutation; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: C495549:Cav3 protein, rat; D051244:Caveolin 3; D022461:Caveolins; D002784:Cholesterol