Wise B C, Guidotti A, Costa E
Proc Natl Acad Sci U S A. 1983 Feb;80(3):886-90. doi: 10.1073/pnas.80.3.886.
gamma-Aminobutyric acid (GABA)-modulin is a brain protein of Mr 16,500 that down-regulates the high-affinity binding site for GABA which is located in crude synaptic membranes. This protein can be phosphorylated in vitro by the catalytic subunit of cAMP-dependent protein kinase and by a partially purified preparation of calmodulin-sensitive Ca2+-dependent protein kinase. The GABA-modulin sites that are phosphorylated by the two enzymes are different, as revealed by HPLC analysis of tryptic digests. The capacity of GABA-modulin to decrease the number of sites that bind [3H]muscimol was completely abolished by phosphorylation of this protein with the cAMP-dependent protein kinase but not with the Ca2+-dependent enzyme. GABA-modulin present in crude synaptic membranes prepared from rat cortex also was shown to be phosphorylated by endogenous protein kinases activated by cAMP, Ca2+ and calmodulin, and Ca2+ and phosphatidylserine. These results suggest a potentially important role for protein kinase and GABA-modulin in the regulation of the number of GABA recognition sites.
γ-氨基丁酸（GABA）调节蛋白是一种分子量为16500的脑蛋白，它可下调位于粗制突触膜上的GABA高亲和力结合位点。该蛋白在体外可被环磷酸腺苷（cAMP）依赖性蛋白激酶的催化亚基以及钙调蛋白敏感的Ca²⁺依赖性蛋白激酶的部分纯化制剂磷酸化。经胰蛋白酶消化产物的高效液相色谱（HPLC）分析表明，这两种酶磷酸化的GABA调节蛋白位点不同。用cAMP依赖性蛋白激酶对该蛋白进行磷酸化可完全消除GABA调节蛋白减少[³H]蝇蕈醇结合位点数量的能力，而用Ca²⁺依赖性酶进行磷酸化则不会。从大鼠皮层制备的粗制突触膜中存在的GABA调节蛋白也被证明可被由cAMP、Ca²⁺和钙调蛋白以及Ca²⁺和磷脂酰丝氨酸激活的内源性蛋白激酶磷酸化。这些结果表明蛋白激酶和GABA调节蛋白在调节GABA识别位点数量方面可能具有重要作用。
