ENDOTHELIN-1 STIMULATES MYRISTOYLATED ALANINE-RICH C-KINASE SUBSTRATE(MARCKS) PHOSPHORYLATION IN RAT CEREBELLAR SLICES

Protein phosphorylation induced by endothelins has been studied using [P-32]orthophosphate-prelabelled rat cerebellar slices. Endothelin-l i ncreased phosphorylation of an 87 kDa protein in a time-dependent mann er (reaching a maximun effect at about 2.5 min) and with an EC(50) equ al to 93 +/- 32 nM. Endothelin-3 and sarafotoxin 6c induced similar le vels of phosphorylation. Endothelin-1 also promoted [H-3]inositol phos phate accumulation with similar EC(50) (71 +/- 7.5 nM). The phosphopro tein of 87 kDa seems to be myristoylated alanine-rich C-kinase substra te (MARCKS) as demonstrated by acetic acid extraction. In addition, 12 -O-tetradecanoylphorbol-13-acetate (TPA) increased 87 kDa protein phos phorylation while Ro-31-8220, a specific protein kinase inhibitor, inh ibited both TPA and endothelin-induced 87 kDa protein phosphorylation. Therefore, it is concluded that protein kinase C is involved in the e ndothelin action on cerebellum.