[1-(1-OXOTRIDECYL)-2-PIPERIDINYL]METHYL)HEXANAMIDE (NPC 15437) - A NOVEL INHIBITOR OF PROTEIN-KINASE-C INTERACTING AT THE REGULATORY DOMAIN

NPC 15437 is a prototype member of a new class of synthetically derive d protein kinase C (PKC) inhibitors. PKC activity and binding of phorb ol ester to the enzyme were inhibited by NPC 15437, with IC50 values o f 19 +/- 2-mu-M and 23 +/- 4-mu-M, respectively. No inhibition of cAMP -dependent or calcium/calmodulin-dependent protein kinases was observe d at concentrations of NPC 15437 up to 300-mu-M. To investigate the me chanism by which NPC 15437 exerts its effect, a kinetic analysis of th e inhibition with respect to three activators of the enzyme, phosphati dylserine, calcium, and phorbol ester, was performed. NPC 15437 was a competitive inhibitor of the activation of PKC by phorbol ester (K(i) = 5 +/- 3-mu-M). Stimulation of PKC-alpha by phosphatidylserine was co mpetitively inhibited by NPC 15437 (K(i) = 12 +/- 4-mu-M). The inhibit ion was mixed with respect to activation by calcium. These results sug gest that NPC 15437 is a selective inhibitor of PKC, interacting at th e regulatory region of the enzyme. NPC 15437 inhibited PKC in intact c ells, dose-dependently antagonizing the phorbol ester-induced phosphor ylation of a 47-kDa protein in human platelets.