Inhibition of lipid raft-dependent signaling by a dystrophy-associated mutant of caveolin-3.
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.
Carozzi
Amanda J
AJ
Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis, and School of Biomedical Sciences, University of Queensland, Brisbane 4072, Australia.
Roy
Sandrine
S
Morrow
Isabel C
IC
Pol
Albert
A
Wyse
Bruce
B
Clyde-Smith
Jodi
J
Prior
Ian A
IA
Nixon
Susan J
SJ
Hancock
John F
JF
Parton
Robert G
RG
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*
C495549:Cav3 protein, rat; D051244:Caveolin 3; D022461:Caveolins; D002784:Cholesterol