Huang X P, Da Silva C, Fan X T, Castagna M
Institut de Recherches Scientifiques sur le Cancer, Villejuif, Paris, France.
Biochim Biophys Acta. 1993 Feb 17;1175(3):351-6. doi: 10.1016/0167-4889(93)90228-h.
Arachidonic acid (AA) activates brain protein kinase C (PKC) in a specific manner, and which differs from that of diacylglycerol (DG)-mediated PKC activation in cofactor Ca2+ and phosphatidylserine (PtdSer) requirements. We presently report that characteristics of AA-mediated activation are heterogenous, and are dependent upon the concentrations of AA. Highly sensitive PKC activation (HS) occurring at concentrations of 20 microM AA can be distinguished from less sensitive PKC activation (LS) requiring concentrations of at least 160 microM AA, on the basis of the effects of phorbol ester TPA or DG, phosphatidylcholine (PtdCho) and sodium deoxycholate (DOC). TPA, like DG suppressed the HS reaction whereas it enhanced the LS reaction. PtdCho, a phospholipid which does not affect DG-mediated activation, also prevented the HS reaction without affecting the LS reaction. This latter was inhibited at 100 microM DOC, a concentration which slightly stimulated the HS reaction. The substrate specificity was also different in the two reactions: the preferential substrate for PKC in HS was histone type VII-S, while it was histone type V-S in LS. Both reactions were similarly affected by PtdSer. In 0.1 mM CaCl2, PtdSer stimulated AA-mediated activation without evoking additive responses while this phospholipid prevented this activation in 0.5 mM EGTA, suggesting that AA and PtdSer bind PKC on the same or related sites. Together these results provide evidence for the existence of different modes of AA-mediated PKC activation with unique characteristics which presumably involve two different binding sites for AA on the same molecule and/or different PKC isoforms.
花生四烯酸（AA）以一种特定的方式激活脑蛋白激酶C（PKC），这与二酰基甘油（DG）介导的PKC激活在辅因子Ca2+和磷脂酰丝氨酸（PtdSer）需求方面有所不同。我们目前报告称，AA介导的激活具有异质性，且取决于AA的浓度。基于佛波酯TPA或DG、磷脂酰胆碱（PtdCho）和脱氧胆酸钠（DOC）的作用，在20微摩尔/升AA浓度下发生的高敏PKC激活（HS）可与至少需要160微摩尔/升AA浓度的低敏PKC激活（LS）区分开来。TPA与DG一样抑制HS反应，而增强LS反应。PtdCho是一种不影响DG介导激活的磷脂，它也能阻止HS反应而不影响LS反应。后者在100微摩尔/升DOC时受到抑制，该浓度对HS反应有轻微刺激。两种反应的底物特异性也不同：HS中PKC的优先底物是组蛋白VII-S型，而LS中是组蛋白V-S型。两种反应受PtdSer的影响相似。在0.1毫摩尔/升CaCl2中，PtdSer刺激AA介导的激活而不引发相加反应，而在0.5毫摩尔/升EGTA中这种磷脂则阻止这种激活，这表明AA和PtdSer在相同或相关位点结合PKC。这些结果共同为存在不同模式的AA介导的PKC激活提供了证据，这些激活具有独特的特征，可能涉及同一分子上AA的两个不同结合位点和/或不同的PKC亚型。
