Does Protein Phosphorylation by Protein Kinase C Support Pseudopodial Cable Growth in Cultured Micromere-Derived Cells of the Sea Urchin, Hemicentrotus pulcherrimus?: (sea urchin/protein kinase C/spicule formation/phorbol ester/H-7).

In cultured cells derived from micromeres, H-7 strongly inhibited the outgrowth of pseudopodial cables and the formation of spicule rods at concentrations around the Ki values for protein kinases. HA1004 did not inhibit the cable growth and spicule rod formation in these cells at higher concentrations than the Ki values for cyclic nucleotide-dependent protein kinases. Pseudopodial cable growth was also inhibited by H-7 in furosemide-treated cells which were able to undergo normal growth of the cables without the formation of spicule rods. Protein phosphorylation, measured by P incorporation into proteins in the cells exposed to Pi, was inhibited by H-7 at the concentrations for the blockage of the cable growth but was hardly blocked by HA1004. The cable growth and protein phosphorylation were activated by phorbol 12-myristate 13-acetate. The activity of Ca , phospholipid-dependent protein kinase (protein kinase C), which was inhibited by H-7, became appreciably high in micromere-derived cells at 16 hr of culture at 20°C, at which the outgrowth of pseudopodial cables was going to be initiated and gradually increased keeping pace with the cable growth. These suggest that the outgrowth of the cables is supported by protein phosphorylation catalyzed by protein kinase C.