Heat shock protein 27 is a substrate of cGMP-dependent protein kinase in intact human platelets: phosphorylation-induced actin polymerization caused by HSP27 mutants.

摘要: Phosphorylation of heat shock protein 27 (Hsp27) in human platelets by mitogen-activated kinase-activated kinase (MAPKAP) 2 is associated with signaling events involved platelet aggregation and regulation microfilament organization. We now show that Hsp27 also phosphorylated cGMP-dependent (cGK), a system important for the inhibition aggregation. Stimulation washed 8-para-chlorophenylthio-cGMP, cGK specific activator, resulted time-dependent phosphorylation Hsp27. This supported ability to phosphorylate vitro an extent comparable cGK-mediated its established substrate vasodilator-stimulated phosphoprotein. Studies mutants identified threonine 143 as yet uncharacterized site specifically targeted cGK. To test hypothesis could inhibit phosphorylating interfering MAPKAP Hsp27, known 2-phosphorylation sites (Ser15, Ser78, Ser82) well Thr143 were replaced negatively charged amino acids, which are considered mimic phosphate groups, tested actin polymerization experiments. Mimicry at led stimulating effect on polymerization. Mutation cGK-specific Thr143alone had no polymerization, but phosphorylation-mimicking mutant, this mutation reduced stimulation significantly. These data suggest Hsp27-dependent microfilaments contribute inhibitory effects function.