Expression of SCC in ovarian granulosa cells and cultured cells, induced rapid structural changes in mitochondria

In this study, the relation of P450scc expression and mitochondrial ultrastructure was examined in rat granulosa cells at the time of ovulation, and in the NIH/3T3 cells. Before ovulation in the ovary, granulosa cells of Graafian follicle which expressed only mRNA of P450scc had elongated mitochonria with lamellar cristae. After ovulation, granulosa lutein cells which expressed both P450scc mRNA and protein had oval and round mitochondria with tubular or vesicular cristae. Two different cytochrome P450scc cDNA fragments in length were subcloned into pEGFPN vector, transfected into NIH/3T3 cells, and the mitochondrial structure was examined under fluorescent microscope with GFP and by electron microscopy. 5'end of cytochrome P450scc contained mitochondrial localization signal, and was composed of about 40 amino acids. NIH/3T3 cells had filamentous and elongated mitochondria with lamellar cristae, free ribosomes, and rER. After the transfection of short fragment of SCC(scc-s:200bp), mitochondria remained filamentous and their cristae also remained lamellar. On the other hand, when almost full length of SCC fragment(scc-f:1.1kb) was transfected, globular and round mitochondria were labeled with GFP, and round or oval mitochondria with vesicular or tubular cristae could be examined by electron microscope. Our study suggests that cytochrome P450scc located in mitochondrial inner membrane plays an important role to determine the mitochondrial morphology in vivo and in vitro.