RECRUITMENT OF MITOCHONDRIAL CYCLOPHILIN TO THE MITOCHONDRIAL INNER MEMBRANE UNDER CONDITIONS OF OXIDATIVE STRESS THAT ENHANCE THE OPENING OF A CALCIUM-SENSITIVE NONSPECIFIC CHANNEL

Binding of mitochondrial matrix cyclophilin (CyP) to the rat liver mit ochondrial membranes was detected by SDS/PAGE and Western blotting wit h suitable antipeptide antibodies. Binding was not affected by prior e xposure of mitochondria to Ca2+, adenine nucleotides or inhibitors of the adenine nucleotide translocase, but was greatly increased by t-but yl hydroperoxide (tBH), phenylarsine oxide or diamide. These all sensi tized the opening of the non-specific mitochondrial pore to [Ca2+], an d the effect of tBH was shown to be maintained after washing away the tBH, consistent with it being caused by the enhanced CyP binding. The bound CyP did not demonstrate peptidyl-prolyl cis-trans isomerase acti vity. CyP-binding was prevented by 5 mu M cyclosporin A, but not rever sed by cyclosporin treatment of the membranes. The effect of tBH on bi nding was concentration-dependent and maximal within 30s.