ACTIVATION OF P21-ACTIVATED PROTEIN-KINASE-ALPHA (ALPHA-PAK) BY HYPEROSMOTIC SHOCK IN NEONATAL VENTRICULAR MYOCYTES

The p21-activated protein kinases (PAKs) may participate in signalling from Cdc42/Rac1 to the stress-regulated MAPKs (SAPKs/JNKs and p38-/HO G-1-related-MAPKs). We characterized the expression and regulation of alpha PAK in cultured ventricular myocytes. alpha PAK was specifically immunoprecipitated from myocyte extracts. High basal alpha PAK activi ty was detected in unstimulated myocytes. Its activity was increased r apidly (< 30 s) by hyperosmotic shock in the presence of okadaic acid, and was maximal by 3 min (187 +/- 7% relative to unstimulated cells). Endothelin-1 and interleukin-1 beta, which also activate SAPKs/JNKs, did not increase alpha PAK activity and presumably act through differe nt PAK isoforms or other mechanisms. (C) 1997 Federation of European B iochemical Societies.