Fig. 4. Diminished incorporation of caveolin-3 into lipid rafts in myotubes expressing the TFT mutant caveolin-3. (A) Extracts of myotubes expressing vector alone (Control) or the TFT mutation were subjected to sucrose density gradient fractionation. 50 µl samples from each fraction (1-12) were analyzed by western blotting for expression of caveolin-3. In control myotubes, caveolin-3 was detected exclusively in the lipid raft (LR) fraction. In myotubes expressing the mutant caveolin-3, most of the caveolin-3 (endogenous plus mutant) was instead found in the non-lipid raft (NLR) fraction with only a small proportion present in the LR fraction. (B) Extracts of myoblasts expressing wild-type caveolin-3 or the TFT mutation were subjected to sucrose density gradient fractionation and analyzed for caveolin-3 expression as in A. Wild-type caveolin-3 preferentially localized to the LR fractions, while mutant protein was completely excluded from lipid rafts.

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