TRAP1 and cyclophilin D compete at OSCP subunit to regulate enzymatic activity and permeability transition pore opening by F-ATP synthase

Binding of the mitochondrial chaperone TRAP1 to client proteins shapes cell bioenergetic and proteostatic adaptations, but the panel of TRAP1 clients is only partially defined. Here we show that TRAP1 interacts with F-ATP synthase, the protein complex that provides most cellular ATP. TRAP1 competes with the peptidyl-prolyl cis-trans isomerase cyclophilin D (CyPD) for binding to the oligomycin sensitivity-conferring protein (OSCP) subunit of F-ATP synthase, increasing its catalytic activity and counteracting the inhibitory effect of CyPD. Moreover, TRAP1 inhibits opening of the permeability transition pore (PTP) formed by F-ATP synthase and effectively antagonizes the PTP-inducing effect of CyPD, which elicits mitochondrial depolarization and cell death. Consistently, electrophysiological measurements indicate that TRAP1 and CyPD compete in the modulation of channel activity of purified F-ATP synthase, resulting in PTP inhibition and activation, respectively, and outcompeting each other effect on the channel. Moreover, TRAP1 counteracts PTP induction by CyPD, whereas CyPD reverses TRAP1-mediated PTP inhibition. Our data identify TRAP1 as a F-ATP synthase regulator that can influence cell bioenergetics and survival and can be targeted in pathological conditions where these processes are dysregulated, such as cancer.