Koroscil T M, Gallant S
J Biol Chem. 1981 Jul 10;256(13):6700-7.
The phosphorylation of rat adrenal protein components in response to adrenocorticotropin has been studied in adrenal quarters, isolated cells, and in vivo. In adrenal quarters, adrenocorticotropic hormone (ACTH)-stimulated phosphorylation or dephosphorylation of proteins was not affected by the presence of protein synthesis inhibitors despite a total inhibition of steroidogenesis. (The term dephosphorylation refers to an apparent decrease in the labeling of a particular protein with 32P at various times after the addition of ACTH. This may be due to enzymatic removal of phosphate or protein degradation or complexation of this protein with another cellular component.) Studies with isolated cell preparations identified several proteins that are phosphorylated or dephosphorylated in response to hormone. These changes in phosphorylation were also observed in adrenal quarters and correlated well with ACTH-stimulated steroidogenesis as determined by temporal analysis and dose-response studies of corticosterone production. In vivo injection of male hypophysectomized rats with [32P]phosphate and ACTH demonstrated changes in the labeling of six adrenal proteins. Many of the proteins phosphorylated in vivo were also demonstrated to be phosphorylated in both in vitro systems. Finally, the injection of a physiological dose of ACTH appeared to selectively activate the type I cAMP-dependent protein kinase within the microsomal fraction as determined by the binding of a photoaffinity-labeled reagent. These results suggest that alterations in phosphorylation of adrenal proteins in response to ACTH is proximal to or independent of the obligatory role of protein synthesis in acute steroidogenesis.
已在肾上腺切片、分离细胞及体内研究了大鼠肾上腺蛋白质成分对促肾上腺皮质激素的磷酸化反应。在肾上腺切片中，尽管类固醇生成被完全抑制，但促肾上腺皮质激素（ACTH）刺激的蛋白质磷酸化或去磷酸化不受蛋白质合成抑制剂存在的影响。（去磷酸化一词指在添加ACTH后不同时间，特定蛋白质用32P标记的明显减少。这可能是由于磷酸的酶促去除、蛋白质降解或该蛋白质与另一种细胞成分的络合。）对分离细胞制剂的研究鉴定出几种响应激素而发生磷酸化或去磷酸化的蛋白质。这些磷酸化变化在肾上腺切片中也观察到，并且与通过皮质酮产生的时间分析和剂量反应研究确定的ACTH刺激的类固醇生成密切相关。对雄性垂体切除大鼠进行[32P]磷酸盐和ACTH的体内注射，显示六种肾上腺蛋白质的标记发生变化。许多在体内发生磷酸化的蛋白质在两种体外系统中也被证明发生了磷酸化。最后，通过光亲和标记试剂的结合确定，注射生理剂量的ACTH似乎选择性地激活了微粒体部分中的I型cAMP依赖性蛋白激酶。这些结果表明，肾上腺蛋白质对ACTH的磷酸化改变在急性类固醇生成中蛋白质合成的必需作用之前或与之无关。
