Hormone-induced changes in cardiolipin from Leydig cells: possible involvement in intramitochondrial cholesterol...

The rate-limiting and hormonally regulated step in steroid hormone biosynthesis is the delivery of cholesterol from the outer to the inner mitochondrial membrane where cytochrome P450scc resides. Although the exact mechanism of intramitochondrial cholesterol translocation remains unknown, the formation of contact sites between outer and inner mitochondrial membranes appears as a necessary component for cholesterol transfer. Several pieces of evidence suggest that local formation of intermembrane contact is a consequence of a non-bilayer arrangement of polymorphic lipids which are enriched in the junctions. As a step toward clarifying mitochondrial contact sites formation and thus cholesterol translocation in steroidogenic cells, we have undertaken studies to identify the factors which might result in non-bilayer structure to be adopted by mitochondrial phospholipids on stimulation of MA-10 Leydig cells. Our results demonstrate that an increase in the unsaturation of the cardiolipin acyl groups on hormonal stimulation might favor the formation of non-bilayer adhesion points.