Interaction of Protein Kinase C with Filamentous Actin: Isozyme Specificity Resulting from Divergent Phorbol Ester and Calcium Dependencies
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- 作者：Simon J. Slater ; Shawn K. Milano ; Brigid A. Stagliano ; Kevin J. Gergich ; Jeffery P. Curry ; Frank J. Taddeo ; and Christopher D. Stubbs
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：January 18, 2000
- 年：2000
- 卷：39
- 期：2
- 页码：271 - 280
- 全文大小：123K
- 年卷期：v.39,no.2(January 18, 2000)
- ISSN：1520-4995
文摘
The mechanism of activation of protein kinase C isoforms by filamentous actin (F-actin) wasinvestigated with respect to isozyme specificity and phorbol ester and Ca2+ dependencies. It was foundthat the "conventional" (cPKC), 
, 
I, II, and 
, "novel" (nPKC) 
and 
, and "atypical" (aPKC) 
isoforms were each activated by F-actin with varying potencies. The level of activity along with theaffinity for binding to F-actin was further potentiated by the phorbol ester 4-12-O-tetradecanoylphorbol13-acetate (TPA), the potency of which again varied for each isoform. By contrast to the other cPKCisoforms, the level of cPKC- activity was unaffected by TPA, as was also the case for aPKC-. It wasfound that whereas in the absence of F-actin the soluble form of cPKC-I contained two phorbol esterbinding sites of low and high affinity, respectively, as previously reported for cPKC- [Slater et al. (1998)J. Biol. Chem. 273, 23160-23168], the F-actin-bound form of the isozyme contained only a single siteof relatively low affinity. The level of TPA required to induce cPKC-, -I, and -II activity and thebinding of these isozymes to F-actin was reduced in the presence of Ca2+. By contrast, the activity ofcPKC- was unaffected by Ca2+, as were the activities of nPKC- and - and aPKC-, as expected.Thus, the interaction with F-actin appears to be a general property of each of the seven PKC isozymestested. However, isoform specificity may, in part, be directed by differences in the phorbol ester andCa2+ dependences, which, with the notable exception of cPKC-, appear to resemble those observed forthe activation of each isoform by membrane association. The observation that cPKC isoforms maytranslocate to F-actin as well as the membrane as a response to an elevation of Ca2+ levels may allow forthe functional coupling of fluctuations of intracellular Ca2+ levels through cPKC to F-actin cytoskeleton-mediated processes.
, I, II, and , "novel" (nPKC) and , and "atypical" (aPKC) isoforms were each activated by F-actin with varying potencies. The level of activity along with theaffinity for binding to F-actin was further potentiated by the phorbol ester 4-12-O-tetradecanoylphorbol13-acetate (TPA), the potency of which again varied for each isoform. By contrast to the other cPKCisoforms, the level of cPKC- activity was unaffected by TPA, as was also the case for aPKC-. It wasfound that whereas in the absence of F-actin the soluble form of cPKC-I contained two phorbol esterbinding sites of low and high affinity, respectively, as previously reported for cPKC- [Slater et al. (1998)J. Biol. Chem. 273, 23160-23168], the F-actin-bound form of the isozyme contained only a single siteof relatively low affinity. The level of TPA required to induce cPKC-, -I, and -II activity and thebinding of these isozymes to F-actin was reduced in the presence of Ca2+. By contrast, the activity ofcPKC- was unaffected by Ca2+, as were the activities of nPKC- and - and aPKC-, as expected.Thus, the interaction with F-actin appears to be a general property of each of the seven PKC isozymestested. However, isoform specificity may, in part, be directed by differences in the phorbol ester andCa2+ dependences, which, with the notable exception of cPKC-, appear to resemble those observed forthe activation of each isoform by membrane association. The observation that cPKC isoforms maytranslocate to F-actin as well as the membrane as a response to an elevation of Ca2+ levels may allow forthe functional coupling of fluctuations of intracellular Ca2+ levels through cPKC to F-actin cytoskeleton-mediated processes.