STIMULATION OF BRAIN MEMBRANE-PROTEIN PHOSPHORYLATION BY CALCIUM AND AN ENDOGENOUS HEAT-STABLE PROTEIN
STIMULATION OF BRAIN MEMBRANE-PROTEIN PHOSPHORYLATION BY CALCIUM AND AN ENDOGENOUS HEAT-STABLE PROTEIN
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DOI：
10.1038/271478a0
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发表时间：
1978-01-01
期刊：
影响因子：
64.8
通讯作者：
GREENGARD, P
中科院分区：
文献类型：
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作者：
SCHULMAN, H;GREENGARD, P
Ca2+ 在神经系统生理学中的重要作用已得到充分证明1,2。然而，其某些生理效应的生化机制，例如刺激-分泌耦合3,4和儿茶酚胺5,6的合成，尚未阐明。钙与多种对突触功能具有潜在重要性的生化反应有关。因此，钙和热稳定的钙结合蛋白激活哺乳动物大脑中的环核苷酸磷酸二酯酶7,8。来自猪脑 9、牛心 10 和牛脑 11 的钙依赖性调节因子 (CDR) 已被纯化和表征。 CDR 似乎是一种钙受体，因为它能强烈且特异性地结合钙。有证据表明 CDR·Ca2+ 复合物是环核苷酸磷酸二酯酶的真正激活剂12-14。这种钙结合蛋白也可以激活去污剂溶解的脑腺苷酸环化酶制剂15。钙刺激完整 16,17 和裂解 18,19 突触体中的蛋白质磷酸化，这种不依赖于环核苷酸的机制可能介导或调节 Ca2+ 对突触前神经末梢功能的一些细胞内效应。我们在此报告，大鼠大脑皮层突触体膜部分的钙依赖性磷酸化需要突触体细胞质中存在的内源性蛋白质因子。钙刺激的磷酸化在纯化突触膜时丢失，并且可以通过用突触体细胞质或纯化的 CDR 制剂重建来有效恢复。因此，钙对钙依赖性蛋白激酶活性的调节可能是通过钙结合蛋白在生理上介导的，钙结合蛋白被假定调节环核苷酸磷酸二酯酶和腺苷酸环化酶。
THE important role of Ca2+in the physiology of the nervous system is well documented1,2. However, the biochemical mechanisms underlying certain of its physiological effects, such as stimulus–secretion coupling3,4and synthesis of cate-cholamines5,6, have not yet been elucidated. Calcium has been implicated in several biochemical reactions of potential importance to synaptic function. Thus, calcium and a heat-stable calcium-binding protein activate the cyclic nucleotide phosphodiesterase from mammalian brain7,8. The calcium-dependent regulator (CDR) from porcine brain9, bovine heart10and bovine brain11has been purified and characterised. CDR seems to be a calcium receptor as it binds calcium strongly and specifically. There is evidence that a CDR·Ca2+complex is the true activator of cyclic nucleotide phosphodiesterase12–14. A detergent-solubilised preparation of brain adenylate cyclase can also be activated by this calcium-binding protein15. Calcium stimulates protein phosphorylation in both intact16,17and lysed18,19synaptosomes and this cyclic nucleotide-independent mechanism may mediate or modulate some of the intracellular effects of Ca2+on the function of presynaptic nerve terminals. We report here that calcium-dependent phosphorylation of synaptosomal membrane fractions from rat cerebral cortex requires an endogenous protein factor present in the synaptosomal cytoplasm. Calcium stimulated phosphorylation is lost on purification of synaptic membranes and can be effectively recovered by reconstitution with either the synaptosomal cytoplasm or with a purified preparation of CDR. Thus, regulation by calcium of calcium-dependent protein kinase activity may be mediated physiologically by the calcium-binding protein postulated to regulate cyclic nucleotide phosphodiesterase and adenylate cyclase.