Differential detection of phosphorylated glycogen synthase kinase 3 alpha and beta depending on blocking conditions

It is generally recommended that immunoblots using phosphospecific antibodies be performed using bovine serum albumin (BSA) instead of milk. There are two subtypes of glycogen synthase kinase 3 (GSK3), GSK3 alpha and GSK3 beta, with apparent molecular weights of 51 and 49 kDa, respectively. Here we show that immunoblots performed using 5% milk allow the detection of both phosphorylated GSK3 alpha and phosphorylated GSK3 beta, whereas only phosphorylated GSK3 alpha is visible when immunoblots are performed using 3% BSA.