Transcriptional Regulation of Ovarian Steroidogenic Genes: Recent Findings Obtained from Stem Cell-Derived Steroidogenic Cells

Figure 4

P450 enzymes and their redox partners in steroidogenesis. (a) Schematic diagram of electron transfer from NADPH to mitochondrial type I P450 enzymes by FDXR and FDX1. At first, NADPH passes the electrons to the nonreduced (ox) FAD moiety of FDXR. Then, reduced (red) FDXR passes them to FDX1, followed by the transfer to P450 enzymes and hydroxylation of cholesterol and its metabolites. (b) Schematic diagram of electron transfer from NADH to microsomal type II P450 enzymes by POR. POR receives the electrons from NADPH by using its FAD moiety, and red FAD passes them to its FMN. Then, electrons are transferred to P450 enzymes to activate the steroid hormone production. (c) The binding sites of NR5A family and other transcription factors, which are essential for the transcription of FDX, FDXR, and ovarian type I P450 genes. (d) Pituitary hormones promote the steroidogenesis by enhancing the transcription of both mitochondrial P450 enzymes and POR.