Knight D E, Sugden D, Baker P F
MRC Secretory Mechanism Group, Division of Biomedical Sciences, Kings College, London, England.
J Membr Biol. 1988 Aug;104(1):21-34. doi: 10.1007/BF01871899.
The calcium sensitivity of exocytosis from electro-permeabilized chromaffin cells is increased by activators of protein kinase C, such as TPA and certain phorbol esters, diacylglycerols, and mezerein. A range of putative inhibitors of protein kinase C block both the phorbol ester-sensitive component of secretion and also the underlying insensitive component. These inhibitors are also shown to inhibit medulla protein kinase C activity in vitro. The extent of secretion is reduced when electro-permeabilized cells are exposed to Ca2+ levels much in excess of 50 microM. The onset of inhibition is faster than the relatively slow rate of Ca-dependent exocytosis and is insensitive to inhibitors of proteolysis. Adrenal medulla protein kinase C activity is also irreversibly inhibited by high Ca2+ concentrations. Both the secretory response and the protein kinase C activity in vitro have similar nucleotide and cation specificities. Although these data do not definitely establish an involvement of protein kinase C in exocytosis, none argue against it.
蛋白激酶C的激活剂，如佛波酯（TPA）和某些佛波醇酯、二酰甘油以及大戟二萜醇，可增强电通透嗜铬细胞胞吐作用的钙敏感性。一系列假定的蛋白激酶C抑制剂既能阻断分泌的佛波酯敏感成分，也能阻断潜在的不敏感成分。这些抑制剂在体外也能抑制髓质蛋白激酶C的活性。当电通透细胞暴露于远超过50微摩尔的钙离子水平时，分泌程度会降低。抑制的起始速度比相对较慢的钙依赖性胞吐作用速度快，并且对蛋白水解抑制剂不敏感。高浓度钙离子也会不可逆地抑制肾上腺髓质蛋白激酶C的活性。体外的分泌反应和蛋白激酶C活性具有相似的核苷酸和阳离子特异性。尽管这些数据并不能明确证明蛋白激酶C参与了胞吐作用，但也没有与之相悖的证据。
