Cyclophilin D plays a critical role in the survival of senescent cells.

Senescent cells play a causative role in many diseases, and their elimination is a promising therapeutic strategy. Here, through a genome-wide CRISPR/Cas9 screen, we identify the gene PPIF, encoding the mitochondrial protein cyclophilin D (CypD), as a novel senolytic target. Cyclophilin D promotes the transient opening of the mitochondrial permeability transition pore (mPTP), which serves as a failsafe mechanism for calcium efflux. We show that senescent cells exhibit a high frequency of transient CypD/mPTP opening events, known as 'flickering'. Inhibition of CypD using genetic or pharmacologic tools, including cyclosporin A, leads to the toxic accumulation of mitochondrial Ca2+ and the death of senescent cells. Genetic or pharmacological inhibition of NCLX, another mitochondrial calcium efflux channel, also leads to senolysis, while inhibition of the main Ca2+ influx channel, MCU, prevents senolysis induced by CypD inhibition. We conclude that senescent cells are highly vulnerable to elevated mitochondrial Ca2+ ions, and that transient CypD/mPTP opening is a critical adaptation mechanism for the survival of senescent cells. Synopsis: Senescent cells present an excessive flux of Ca2+ from the ER into the mitochondria. This study shows that cyclophilin D increases the survival of senescent cells by mediating a transient opening of the mitochondrial permeability transition pore (mPTP). Cyclophilin D (CypD) is a novel senolytic target. Senescent cells rely on CypD-dependent mPTP flickering, a mechanism that effects matrix Ca2+ efflux. Genetic or pharmacological blockage of CypD or of mitochondrial Ca2+ efflux channel NCLX leads to preferential elimination of senescent cells. Reduction of mitochondrial Ca2+ influx in senescent cells via MCU reduces the toxicity of CypD inhibition. Senescent cells rely on cyclophilin D to allow the release of calcium overload from the mitochondrial matrix. [ABSTRACT FROM AUTHOR]