Cdc42-independent activation and translocation of the cytostatic p21-activated protein kinase gamma-PAK by sphingosine

Autophosphorylation of p21-activated protein kinase gamma -PAK is stimulate d at 10 muM sphingosine in vitro and is maximal at 100 muM. Sites autophosp horylated on gamma -PAK in response to sphingosine are identical to those o btained with Cdc42(GTP). Autophosphorylation is paralleled by stimulation o f gamma -PAK activity as measured with peptide and protein substrates. In 3 T3-L1 cells, sphingosine stimulates the autophosphorylation and activity of gamma -PAK associated with the membrane-containing particulate fraction by 2.8-fold, but does not stimulate the activity of the soluble enzyme. Thus, gamma -PAK is activatable via a Cdc42-independent mechanism, suggesting sp hingosine has a role in gamma -PAK activation under conditions of cell stre ss. (C) 2001 Federation of European Biochemical Societies. Published by Els evier Science B.V. All rights reserved.