Figure 4.

NTN causes sustained activation of Ret and MAPK. (A) SCG cultures were treated with control medium (Cont), NTN, or GDNF and lysed either 10 min or 30 h after treatment. Western blots of phosphotyrosine immunoprecipitates (Upper) and corresponding total lysates (Lower) were probed with an anti-Ret antibody. (B) SCG cultures were deprived of NGF for 2 h then treated with control medium (Cont) or NTN for 10 min, 60 min, 4 h, or 30 h. A protein blot of total cell lysates was first probed with a phospho-specific MAPK antibody (P-MAPK; Upper) and then re-probed with an antibody that recognizes phosphorylated and nonphosphorylated MAPK (p44/p42; Lower).