Dawson G, McAtee P
Department of Pediatrics, University of Chicago, Illinois 60637.
J Cell Biochem. 1989 Jul;40(3):261-9. doi: 10.1002/jcb.240400302.
Myelin basic protein, an 80-kilodalton (kDa) protein in rat oligodendrocytes, and an 80-kDa basic protein in neuroblastoma x neonatal Chinese hamster brain explant hybrids were phosphorylated extensively when the cells were treated with either phorbol esters (TPA) or diacylglycerols (e.g., oleyoyl-acetylglycerol). TPA-stimulated phosphorylation was inhibited by pre-incubation with 50 microM psychosine (galactosyl-sphingosine), confirming that it is mediated through the phospholipid-dependent protein kinase C (PK-C). Surprisingly, phosphorylation of these proteins was inhibited by incubation of cells with agents which result in activation of cyclic-AMP-dependent protein kinase (dibutyryl cyclic AMP or forskolin). In contrast, phosphorylation of other nonbasic proteins, for example, the oligodendrocyte-specific 2',3'-cyclic nucleotide phosphohydrolase, was stimulated under these conditions (Vartanian et al.: Proceedings of the National Academy of Sciences of the United States of America 85:939, 1988). The possible role of cyclic AMP in activating specific phosphatases or restricting the availability of diacylglycerol for PK-C activation is discussed.
髓鞘碱性蛋白是大鼠少突胶质细胞中的一种80千道尔顿（kDa）的蛋白质，在神经母细胞瘤与新生中国仓鼠脑外植体杂交细胞中的一种80 kDa碱性蛋白，当用佛波酯（TPA）或二酰基甘油（如油酰基-乙酰甘油）处理细胞时会被广泛磷酸化。用50微摩尔的鞘氨醇半乳糖苷（半乳糖基-鞘氨醇）预孵育可抑制TPA刺激的磷酸化，证实其是通过磷脂依赖性蛋白激酶C（PK-C）介导的。令人惊讶的是，用导致环磷酸腺苷依赖性蛋白激酶激活的试剂（二丁酰环磷酸腺苷或福斯高林）孵育细胞会抑制这些蛋白质的磷酸化。相比之下，在这些条件下其他非碱性蛋白质的磷酸化，例如少突胶质细胞特异性2'，3'-环核苷酸磷酸二酯酶，会被刺激（瓦尔塔尼安等人：《美国国家科学院院刊》85:939，1988）。讨论了环磷酸腺苷在激活特定磷酸酶或限制二酰基甘油用于PK-C激活的可用性方面的可能作用。
