ACUTE HORMONAL REGULATION OF STEROIDOGENESIS

营养激素通过作用于 类固醇生成的速率决定步骤， 底物胆固醇从细胞内储存到内部 线粒体膜 在那里，胆固醇会被代谢成 去甲烯醇酮 使用各种方法，我们证明， 线粒体外周型苯二氮卓受体（PBR）介导 胆固醇从线粒体外层向线粒体内层的转运 膜和随后的类固醇生物合成。 我们进一步 证明PBR作为胆固醇特异性通道发挥作用。 我们的假设是，急性（秒至分钟）的激素调节， PBR受体复合物，优先位于线粒体上 膜接触部位，负责激素诱导 类固醇生成和PBR复合物与 类固醇诱导的类固醇生成急性调节蛋白（星星）是 负责维持类固醇生产更长的时间 （小时）。 在第一个目标中，我们将建立时间和空间 PBR和星星蛋白在响应hCG中的关系。 在第二 目的，我们将研究PBR复合物的结构， 从对照和LH处理的Leydig中分离的线粒体接触位点 细胞在寻找“分子开关”负责的影响， LH/hCG对PBR的影响，我们鉴定了两种候选的PBR相关蛋白 （PAPs）。 在第三个目标中，我们将研究PAP在以下方面的作用： 胆固醇转运， 类固醇生成 考虑到追回星星发挥其作用的结论， 在地球之外，它可能直接作用于 PBR或通过PAP间接。 在第四个目标中，我们将研究 StAR-PBR相互作用及其功能后果 互动 我们的目标是了解事件发生的顺序 负责诱导和维持类固醇合成， 荷尔蒙 我们的睾丸间质细胞模型系统是MA-10激素- 反应细胞系，纯化的大鼠Leydig细胞，R2 C细胞系 表达组成型类固醇生成，和R2 C PBR阴性（-）细胞， 通过基因靶向产生。

Trophic hormones acutely stimulate steroid production by acting on the rate-determining step of steroidogenesis, the transport of the substrate, cholesterol, from intracellular stores to the inner mitochondrial membrane. There, cholesterol will be metabolized to pregnenolone. Using various approaches we demonstrated that the mitochondrial peripheral-type benzodiazepine receptor (PBR) mediates the transport of cholesterol from the outer to the inner mitochondrial membrane and the subsequent steroid biosynthesis. We further demonstrated that PBR functions as a channel specific for cholesterol. It is our hypothesis that the acute (sec to min) hormonal regulation of the PBR receptor complex, preferentially located on the mitochondrial membrane contact sites, is responsible for the hormonal induction of steroidogenesis and that the interaction of the PBR complex with the hormone-induced steroidogenic acute regulatory protein (StAR) is responsible for sustaining steroid production for longer periods of time (hours). In the first aim we will establish the temporal and spatial relationship of PBR and StAR proteins in response to hCG. In the second aim we will examine the structure of the PBR complex in the mitochondrial contact sites isolated from control and LH-treated Leydig cells. In search for the "molecular switch" responsible for the effects of LH/hCG on PBR we identified two candidate PBR-associated proteins (PAPs). In the third aim, we will investigate the role of the PAPs in the hormone-induced changes in PBR, cholesterol transport, and steroidogenesis. Considering the finding that StAR exerts its effect outside the mitochondrion, it is possible that it may act directly on PBR or indirectly via a PAP. In the fourth aim we will examine the StAR-PBR interaction and the functional consequences of this interaction. Our goal is to understand the sequence of events responsible for the induction and maintenance of steroidogenesis by hormones. Our Leydig cell model systems are the MA-10 hormone- responsive cell line, purified rat Leydig cells, the R2C cell line expressing constitutive steroidogenesis, and R2C PBR negative (-) cells, generated by gene targeting.