Modulation of octopamine-mediated production of cyclic AMP by phorbol-ester-sensitive protein kinase C in an insect cell line

Partial characterization of protein kinase C from an insect cell line

The characteristics of protein kinase C (EC 2.7.1.37) from an insect cell line (Choristoneura fumiferana) have been described. DEAE-cellulose chromatography produced a major peak of activity which eluted at 0.04-0.055 M NaCl. The enzyme was sensitive to phosphatidylserine in the presence of calcium. Phorbol 12-myristate 13-acetate (PMA) in nanomolar concentrations stimulated protein kinase C activity 8-fold over basal levels and reduced the enzymes requirement for Ca2+. The enzyme had a Ka of 10 nM for PMA. Diacylglycerols tested included diolein, dilinolein, diarachidonin, oleoyl-acetyl-glycerol, dioctonoyl-sn-glycerol, dipalmitin and distearin. A 2.5- to 3-fold activation was obtained in the presence of 26 microM diolein, 40 microM oleoyl-acetyl-glycerol and 46 microM dioctonoyl-sn-glycerol. The enzyme activity was sensitive to the inhibitor H-7 and 50% inhibition was achieved at a concentration of 52 microM H-7. Phosphatidylinositol enhanced enzyme activity in the absence of phosphatidylserine but phosphatidylethanolamine had no effect.

Amblyomma americanum (L.): protein kinase C-independent fluid secretion by isolated salivary glands

Protein kinase C activity was partially purified from tick salivary glands by fast protein liquid chromatography anion-exchange chromatography. Enzyme activity was stimulated by Ca2+, phosphatidylserine, and diacylglycerol with the highest activity observed in the presence of all three modulators. Enzyme activity was inhibited by a synthetic pseudosubstrate peptide with an amino acid sequence resembling the protein kinase C substrate phosphorylation site. The protein kinase C activator, 1-oleoyl-2-acetyl-sn-glycerol (OAG), when added to whole in vitro salivary glands previously prelabeled with 32P, stimulated the phosphorylation of salivary gland proteins. Activators of protein kinase C (phorbol ester or OAG) did not stimulate fluid secretion by isolated tick salivary glands. OAG and phorbol ester had only minimal affects on the ability of dopamine to stimulate secretion by isolated salivary glands and dopamine's ability to increase salivary gland cyclic AMP.