Growth factor treatment of medulloblastoma cells induces degradation of GRK6 via the proteasomal pathway. (A) D556 or (B) Daoy was cultured in EMEM medium with GF + or serum-free EMEM (GF-), treated with100μg/ml CHX or without CHX at indicated time points. GRK6 level was determined by Western blot. Growth factor withdrawal increases stability of GRK6 (C) Daoy or D556 was treated with CHX alone or CHX plus 10 μM MG132 for 8 h, then GRK6 protein level was examined by Western blot. GRK6 stability is maintained in the presence of proteasomal inhibitor MG132.