Chemoattractant-mediated increases in cGMP induce changes in Dictyostelium myosin II heavy chain-specific protein kinase C activities.

Myosin II heavy chain (MHC)-specific protein kinase C isolated from the ameba, Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cAMP (Abu-Elneel et al. 1996. J. Biol. Chem. 271:977- 984). Recent studies have indicated that cAMP-induced cGMP accumulation plays a role in the regulation of myosin II phosphorylation and localization (Liu, G., and P. Newell. 1991. J. Cell. Sci. 98: 483-490). This report describes the roles of cAMP and cGMP in the regulation of membrane association, phosphorylation, and activity (hereafter termed MHC-duanyu1531 activities). cAMP stimulation of Dictyostelium cells resulted in translocation of MHC-duanyu1531 from the cytosol to the membrane fraction, as well as increasing in MHC-duanyu1531 phosphorylation and in its kinase activity. We present evidence that MHC is phosphorylated by MHC-duanyu1531 in the cell cortex which leads to myosin II dissociation from the cytoskeleton. Use of Dictyostelium mutants that exhibit aberrant cAMP-induced increases in cGMP accumulation revealed that MHC-duanyu1531 activities are regulated by cGMP. Dictyostelium streamer F mutant (stmF), which produces a prolonged peak of cGMP accumulation upon cAMP stimulation, exhibits prolonged increases in MHC-duanyu1531 activities. In contrast, Dictyostelium KI-10 mutant that lacks the normal cAMP-induced cGMP response, or KI-4 mutant that shows nearly normal cAMP-induced cGMP response but has aberrant cGMP binding activity, show no changes in MHC-duanyu1531 activities. We provide evidence that cGMP may affect MHC-duanyu1531 activities via the activation of cGMP-dependent protein kinase which, in turn, phosphorylates The results presented here indicate that cAMP-induced cGMP accumulation regulates myosin II phosphorylation and localization via the regulation of

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