Role of steroid sulfates in the regulation of steroid hormone biosynthesis

类固醇激素的生物合成是通过六种细胞色素P450参与的一系列反应实现的。Cyp11a1发挥着核心作用，因为它催化了最初的反应，即胆固醇侧链断裂为孕烯醇酮。细胞色素P17是一种酶，催化形成性激素生物合成所必需的中间体。硫化类固醇和类固醇生物合成途径的中间产物和最终产物对这些细胞色素P450的影响研究很少或没有，但人们很感兴趣，特别是因为与游离形式相比，许多类固醇激素以更高的浓度以酯的形式出现。本项目的目的是研究这些化合物在重组的体外系统中对Cyp11a1和CyP17活性的影响。将研究硫化类固醇是否可以作为这些酶的底物或抑制剂。此外，还将研究它们对蛋白质-蛋白质相互作用的影响。最后，使用共表达Cyp11a1和CyP17系统的重组COS-1细胞培养物，类固醇硫酸盐载体如SOAT、类固醇磺基转移酶或STS，将在细胞系统中研究不同途径(类固醇生物合成、类固醇磺化、类固醇硫酸盐水解)对类固醇激素生物合成的影响。

De novo steroid hormone biosynthesis is realized via a cascade of reactions with participation of six cytochromes P450. CYP11A1 is playing a central role, since it is catalyzing the initial reaction, the side-chain cleavage of cholesterol to pregnenolone. CYP17 is the enzyme catalyzing the formation of essential intermediates for the biosynthesis of sexual hormones. The effect of sulfated steroids and of intermediates and end products of the steroid biosynthesis pathway onto these cytochromes P450 is poorly or not studied but of high interest, especially since many steroid hormones occur in much higher concentrations as esters compared with the free forms. The aim of our project is to investigate the effect of these compounds on the activities of CYP11A1 and CYP17 in reconstituted in vitro systems. It will be studied whether sulfated steroids could serve as substrates or inhibitors of these enzymes. In addition, their effect on protein-protein interactions will be investigated. Finally, using recombinant COS-1 cell cultures co-expressing the CYP11A1 and CYP17 systems, steroid sulfate carriers such as SOAT, steroid sulfotransferases or StS, the effect of the different pathways (steroid biosynthesis, steroid sulfonation, steroid sulfate hydrolysis) on steroid hormone biosynthesis will be investigated in a cellular system.