Figure 8.

Lipid rafts protect Ret from degradation by sequestering Ret away from Cbl proteins. Sympathetic neurons were treated with medium alone or with medium containing GDNF (50 ng/ml) for 45 min. Detergent-resistant membranes were purified as described in Materials and Methods. Cbl-b was immunoprecipitated from both Triton X-100-insoluble and -soluble fractions, and these immunoprecipitates were analyzed by immunoblotting using the antibodies listed to the right of each blot. The relative purity of the lipid raft fractions were confirmed with flotillin-1 and transferrin receptor immunoblotting of the supernatants from the immunoprecipitations. This experiment was performed twice with similar results. INSOL, Insoluble pellets containing lipid rafts; SOL, soluble fraction containing nonraft membrane fractions; IP, immunoprecipitate; TrfR, transferrin receptor; P-Tyr, phosphotyrosine; W, Western blot.