Girault J A, Hemmings H C, Zorn S H, Gustafson E L, Greengard P
Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, New York.
J Neurochem. 1990 Nov;55(5):1772-83. doi: 10.1111/j.1471-4159.1990.tb04968.x.
DARPP-32, a dopamine- and cyclic AMP-regulated phosphoprotein of Mr 32,000, is phosphorylated in vitro by casein kinase II at a site which is also phosphorylated in intact cells. In the present study, we show that a protein kinase activity, present in caudate-putamen cytosol, phosphorylates DARPP-32 on a seryl residue located on the same thermolytic peptide that is phosphorylated by purified casein kinase II. This DARPP-32 serine kinase was indistinguishable from casein kinase II on the basis of a number of biochemical criteria. Excitotoxic lesions of the caudate-putamen and immunocytochemistry revealed the presence of casein kinase II in the medium-sized striatonigral neurons which are known to contain DARPP-32. Casein kinase II activity was high in all rat brain regions studied, and casein kinase II-like immunoreactivity was detected in most brain neurons, although some neuronal populations (e.g., cortical pyramidal cells and large striatal neurons) were stained more intensely than others. In rat caudate-putamen, 45% of the total casein kinase II activity was in the cytosol and 20% in the synaptosomal fraction. In mouse cerebral cortex and caudate-putamen, casein kinase II activity was high at embryonic day 16, and remained elevated during development. In addition to DARPP-32, several major substrates for casein kinase II were observed specifically in brain, but not in liver extracts. The high activity of casein kinase II in brain from the embryonic period to adult age and the existence of a number of specific substrates suggest that this enzyme may play an important role in both developing and mature brain, possibly in modulating the responsiveness of target proteins to various extracellular signals.
DARPP - 32是一种分子量为32000的多巴胺和环磷酸腺苷调节磷蛋白，在体外可被酪蛋白激酶II在一个完整细胞中也会磷酸化的位点磷酸化。在本研究中，我们发现尾状核 - 壳核细胞溶质中存在一种蛋白激酶活性，可使DARPP - 32位于与纯化的酪蛋白激酶II磷酸化的相同热解肽上的一个丝氨酸残基磷酸化。基于一些生化标准，这种DARPP - 32丝氨酸激酶与酪蛋白激酶II无法区分。尾状核 - 壳核的兴奋性毒性损伤和免疫细胞化学显示，在已知含有DARPP - 32的中等大小纹状体黑质神经元中存在酪蛋白激酶II。在所研究的所有大鼠脑区中，酪蛋白激酶II活性都很高，并且在大多数脑神经元中都检测到了酪蛋白激酶II样免疫反应性，尽管一些神经元群体（如皮质锥体细胞和大的纹状体神经元）染色比其他群体更强烈。在大鼠尾状核 - 壳核中，总酪蛋白激酶II活性的45%存在于细胞溶质中，20%存在于突触体部分。在小鼠大脑皮质和尾状核 - 壳核中，酪蛋白激酶II活性在胚胎第16天很高，并在发育过程中持续升高。除了DARPP - 32外，在脑提取物中还特异性观察到了几种酪蛋白激酶II的主要底物，但在肝脏提取物中未观察到。从胚胎期到成年期，酪蛋白激酶II在脑中的高活性以及许多特异性底物的存在表明，这种酶可能在发育中的和成熟的大脑中都发挥重要作用，可能在调节靶蛋白对各种细胞外信号的反应性方面发挥作用。
