PROTEIN-PHOSPHORYLATION IN THE NEURAL TISSUE OF AN ADULT CRICKET (ACHETA-DOMESTICUS) - ENDOGENOUS SUBSTRATES AND THEIR PROTEIN-KINASES

Protein phosphorylation was analysed in neural tissue of adult cricket s (Acheta domesticus). After in vitro phosphorylation of 15,000 g supe rnatants and pellets, endogenous substrates for several protein kinase s were separated on SDS-PAGE. Ten polypeptides with apparent molecular weights ranging from 89.5 to 20 kDa were phosphorylated in a cyclic n ucleotide-dependent manner; several (70, 42, 41 and 34.5 kDa peptides) were observed in both fractions. A strong enhancement of P-32 incor poration into 57, 50, 37 and 28.5 kDa peptides was observed in the pre sence of Ca2+ and calmodulin. In the presence of stimulators of protei n kinase C (Ca2+, PMA, phosphatidylserine), the phosphorylation of sev eral peptides (34, 29.5, 24.5, 22, 20 and 17.5 kDa) was stimulated. Ga ngliosides were also demonstrated to be able to modulate the phosphory lation of several peptides, especially as 39 kDa peptide in the partic ulate fraction. Polyamines stimulated the phosphorylation of two pepti des (53.5 and 37.5 kDa), one of which was specific for the neural tiss ue cytosol (53.5 kDa). By contrast, the phosphorylation of three high molecular weight peptides (207, 128 and 108 kDa) present in the supern atant and pellet decreased in the presence of polyamines. These findin gs were compared to results obtained in other insects.