HORMONE-INDUCED CHANGES IN CARDIOLIPIN FROM LEYDIG-CELLS - POSSIBLE INVOLVEMENT IN INTRAMITOCHONDRIAL CHOLESTEROL TRANSLOCATION

The rate-limiting and hormonally regulated step in steroid hormone bio synthesis is the delivery of cholesterol from the outer to the inner m itochondrial membrane where cytochrome P450scc resides. Although the e xact mechanism of intramitochondrial cholesterol translocation remains unknown, the formation of contact sites between outer and inner mitoc hondrial membranes appears as a necessary component for cholesterol tr ansfer. Several pieces of evidence suggest that local formation of int ermembrane contact is a consequence of a non-bilayer arrangement of po lymorphic 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 i dentify 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 f ormation of non-bilayer adhesion points.