Fig. 6. Effects of the TFT caveolin-3 mutation on caveolin-3 binding to Src and targeting of Src to lipid rafts. (A) Equal amounts of protein from control myotubes and myotubes expressing the TFT mutation were used for immunoprecipitation of Src. The total immunoprecipitated samples were then analyzed by western blotting for levels of Src and caveolin-3. Even though the total levels of Src were similar in both cell populations, there was a decrease in associated caveolin-3 in myotubes expressing the TFT mutation compared to control myotubes. (B) In order to test for the effects of the TFT mutation on the targeting of Src to lipid rafts, extracts from control myotubes or myotubes expressing the TFT mutation were subjected to sucrose density gradient fractionation (SDGF) as in Fig. 4. For ease of analysis, fractions 4 and 5 were pooled from each gradient and referred to as the lipid raft (LR) fraction. An equal amount of protein (10 µg) from the LR fraction of each cell population was analyzed by western blotting for levels of Src and caveolin-3. Both Src and caveolin-3 levels were reduced in LR fractions from myotubes expressing the mutant caveolin-3.