Effects of Ethanol on Protein Kinase C Activity Induced by Association with Rho GTPases
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- 作者：Simon J. Slater ; Anthony C. Cook ; Jodie L. Seiz ; Steve A. Malinowski ; Brigid A. Stagliano ; and Christopher D. Stubbs
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：October 21, 2003
- 年：2003
- 卷：42
- 期：41
- 页码：12105 - 12114
- 全文大小：144K
- 年卷期：v.42,no.41(October 21, 2003)
- ISSN：1520-4995
文摘
Previous studies have shown that n-alkanols have biphasic chain length-dependent effects onprotein kinase C (PKC) activity induced by association with membranes or with filamentous actin [Slater,S. J., et al. (1997) J. Biol. Chem. 272, 6167-6173; Slater, S. J., et al. (2001) Biochim. Biophys. Acta1544, 207-216]. Recently, we showed that PKC
is also activated by a direct membrane lipid-independentinteraction with Rho GTPases. Here, the effects of ethanol and 1-hexanol on Rho GTPase-induced activitywere investigated using an in vitro assay system to provide further insight into the mechanism of theeffects of n-alkanols on PKC activity. Both ethanol and 1-hexanol were found to have two competingconcentration-dependent effects on the Ca2+- and phorbol ester- or diacylglycerol-dependent activities ofPKC associated with either RhoA or Cdc42, consisting of a potentiation at low alcohol levels and anattenuation of activity at higher levels. Measurements of the Ca2+, phorbol ester, and diacylglycerolconcentration-response curves for Cdc42-induced activation indicated that the activating effect corresponded to a shift in the midpoints of each of the curves to lower activator concentrations, while theattenuating effect corresponded to a decrease in the level of activity induced by maximal activator levels.The presence of ethanol enhanced the interaction of PKC with Cdc42 within a concentration rangecorresponding to the potentiating effect, whereas the level of binding was unaffected by higher ethanollevels that were found to attenuate activity. Thus, ethanol may either enhance activation of PKC by RhoGTPases by enhancing the interaction between the two proteins or attenuate the level of activity of RhoGTPase-associated PKC by inhibiting the ensuing activating conformational change. The results alsosuggest that the effects of ethanol on Rho GTPase-induced activity may switch between an activation andinhibition depending on the concentration of Ca2+ and other activators.
is also activated by a direct membrane lipid-independentinteraction with Rho GTPases. Here, the effects of ethanol and 1-hexanol on Rho GTPase-induced activitywere investigated using an in vitro assay system to provide further insight into the mechanism of theeffects of n-alkanols on PKC activity. Both ethanol and 1-hexanol were found to have two competingconcentration-dependent effects on the Ca2+- and phorbol ester- or diacylglycerol-dependent activities ofPKC associated with either RhoA or Cdc42, consisting of a potentiation at low alcohol levels and anattenuation of activity at higher levels. Measurements of the Ca2+, phorbol ester, and diacylglycerolconcentration-response curves for Cdc42-induced activation indicated that the activating effect corresponded to a shift in the midpoints of each of the curves to lower activator concentrations, while theattenuating effect corresponded to a decrease in the level of activity induced by maximal activator levels.The presence of ethanol enhanced the interaction of PKC with Cdc42 within a concentration rangecorresponding to the potentiating effect, whereas the level of binding was unaffected by higher ethanollevels that were found to attenuate activity. Thus, ethanol may either enhance activation of PKC by RhoGTPases by enhancing the interaction between the two proteins or attenuate the level of activity of RhoGTPase-associated PKC by inhibiting the ensuing activating conformational change. The results alsosuggest that the effects of ethanol on Rho GTPase-induced activity may switch between an activation andinhibition depending on the concentration of Ca2+ and other activators.