Gregory C W, DePhilip R M
Department of Cell Biology, Neurobiology and Anatomy, Ohio State University College of Medicine, Columbus 43210.
Endocrinology. 1992 Nov;131(5):2103-12. doi: 10.1210/endo.131.5.1330490.
Sertoli cell intracellular protein 1 (SCc1) and 2 (SCc2) are polypeptides found in rat Sertoli cell cultures incubated with either FSH or (Bu)2cAMP. They were first identified in [35S]methionine-labeled Sertoli cell lysates using two-dimensional gel electrophoresis. Here we extend these observations by showing that SCc1 and SCc2 are present in rat seminiferous tubules, ovaries, and granulosa cells incubated with either FSH or (Bu)2cAMP and in testicular peritubular cells incubated with (Bu)2cAMP. Peritubular cells do not, however, respond to FSH with the production of SCc1 and SCc2. Peptide mapping with N-chlorosuccinimide revealed that SCc1 and SCc2 have similar cleavage patterns, suggesting a common primary amino acid sequence that is modified posttranslationally. Metabolic labeling with [32P]orthophosphate provided direct evidence that SCc1 and SCc2 are phosphoproteins. A shift in mobility of SCc1 and SCc2 toward the basic region of the gel to positions designated SCc1' and SCc2' occurred when cell lysates were treated with alkaline phosphatase before electrophoresis, providing additional evidence that SCc1 and SCc2 are phosphoproteins. SCc1 and SCc2 are also shown to be mitochondrially-associated in the Sertoli cell. Peptide maps of SCc1, SCc2, SCc1', and SCc2' obtained by treatment with alpha-chymotrypsin, are identical to proteolytic maps of proteins pp30', p30, and pp30 from adrenocortical cells. SCc1, SCc2, SCc1', and SCc2' are homologous with regard to their regulated expression, electrophoretic mobility, and mitochondrial localization to the adrenal proteins pp30' and pp30 as well as a series of 30 kilodalton proteins from MA-10 Leydig tumor cells. Both the adrenal cell proteins and the Leydig tumor cell proteins are thought to participate in cholesterol transport to the inner mitochondrial membrane, providing substrate for the cholesterol side-chain cleavage enzyme complex, an activity which the Sertoli cell does not perform, suggesting that alternative functions must be sought for SCc1 and SCc2 in Sertoli cells.
支持细胞胞内蛋白1（SCc1）和2（SCc2）是在与促卵泡激素（FSH）或双丁酰环磷腺苷（Bu）2cAMP共同孵育的大鼠支持细胞培养物中发现的多肽。它们最初是在[35S]甲硫氨酸标记的支持细胞裂解物中通过二维凝胶电泳鉴定出来的。在此，我们通过研究发现，SCc1和SCc2存在于与FSH或（Bu）2cAMP共同孵育的大鼠生精小管、卵巢和颗粒细胞中，以及与（Bu）2cAMP共同孵育的睾丸管周细胞中。然而，管周细胞对FSH无反应，不会产生SCc1和SCc2。用N - 氯代琥珀酰亚胺进行肽图分析表明，SCc1和SCc2具有相似的裂解模式，这表明它们具有共同的一级氨基酸序列，且该序列在翻译后发生了修饰。用[32P]正磷酸盐进行代谢标记提供了直接证据，证明SCc1和SCc2是磷蛋白。在电泳前用碱性磷酸酶处理细胞裂解物时，SCc1和SCc2的迁移率向凝胶的碱性区域移动至标记为SCc1'和SCc2'的位置，这进一步证明了SCc1和SCc2是磷蛋白。在支持细胞中，SCc1和SCc2还被证明与线粒体相关。用α - 胰凝乳蛋白酶处理获得的SCc1、SCc2、SCc1'和SCc2'的肽图，与肾上腺皮质细胞中蛋白质pp30'、p30和pp30的蛋白水解图谱相同。SCc1、SCc2、SCc1'和SCc2'在其调控表达、电泳迁移率以及线粒体定位方面与肾上腺蛋白pp30'和pp30以及来自MA - 10睾丸间质细胞瘤细胞的一系列30千道尔顿蛋白同源。肾上腺细胞蛋白和睾丸间质细胞瘤细胞蛋白都被认为参与胆固醇向线粒体内膜的转运，为胆固醇侧链裂解酶复合物提供底物，而支持细胞不具备这种活性，这表明必须在支持细胞中寻找SCc1和SCc2的其他功能。
