O'Callaghan J P, Dunn L A, Lovenberg W
Proc Natl Acad Sci U S A. 1980 Oct;77(10):5812-6. doi: 10.1073/pnas.77.10.5812.
Calcium stimulated the phosphorylation of several specific synaptosomal cytosolic proteins. The effects of calcium were both concentration and time dependent and were most apparent for proteins with molecular weights of 50,000, 55,000, and 60,000. Exogenous calcium (1.0-100 microM) enhanced the net incorporation of phosphate into protein by as much as 23-fold. In the absence of added calcium, the calcium chelator [ethylenebis(oxyethylenenitriolo)]tetraacetic acid did not lower the phosphorylation of any protein below control levels. The antipsychotic, fluphenazine (1.0-100 microM), caused a concentration-dependent decrease in calcium-stimulated protein phosphorylation. When the heat-stable calcium-binding protein, calmodulin, was removed from synaptosomal cytosol by affinity chromatography on fluphenazine-Sepharose, calcium-stimulated protein phosphorylation was abolished. Responsiveness to calcium could be restored by the addition of calmodulin to the phosphorylation assay. These results indicate that calcium-dependent protein kinases are of major importance in regulating the phosphorylation of specific cytosolic proteins in neuronal tissue. Furthermore, it would appear that one of the three substrates under investigation is specific to synaptosomal cytosol whereas the other two are present in both the cytosol and membrane fractions.
钙刺激了几种特定突触体胞质蛋白的磷酸化。钙的作用具有浓度和时间依赖性，对于分子量为50,000、55,000和60,000的蛋白质最为明显。外源钙（1.0 - 100微摩尔）使蛋白质中磷酸的净掺入量增加了多达23倍。在不添加钙的情况下，钙螯合剂[乙二胺双（氧乙烯基三胺）]四乙酸并没有将任何蛋白质的磷酸化水平降低到对照水平以下。抗精神病药物氟奋乃静（1.0 - 100微摩尔）导致钙刺激的蛋白质磷酸化呈浓度依赖性降低。当通过在氟奋乃静 - 琼脂糖上进行亲和层析从突触体胞质溶胶中去除热稳定钙结合蛋白钙调蛋白时，钙刺激的蛋白质磷酸化被消除。通过向磷酸化测定中添加钙调蛋白可以恢复对钙的反应性。这些结果表明，钙依赖性蛋白激酶在调节神经元组织中特定胞质蛋白的磷酸化方面具有重要作用。此外，在所研究的三种底物中，似乎有一种对突触体胞质溶胶具有特异性，而另外两种则同时存在于胞质溶胶和膜组分中。
