Mitochondria-specific photorelease of ceramide induces apoptosis

Deciphering the mechanisms by which bioactive intermediates of lipid metabolism influence cell behavior is a challenging task. We previously demonstrated that de novo synthesized ceramides are authentic transducers of apoptosis and that their CERT-mediated diversion to mitochondria is sufficient to initiate BAX-dependent apoptosis. To further unravel the mechanism by which mitochondrial ceramides commit cells to death, we here developed a novel mitochondria-targeted and photocaged short-chain ceramide with a clickable alkyne group for derivatization with a fluorescent reporter. We show that this compound readily and selectively accumulates inside mitochondria in a biologically inert state. Subsequent photorelease of the ceramide moiety triggered apoptosis as evidenced by proteolytic cleavage of central components of the caspase-dependent cell death pathway. Our findings reinforce the notion that ceramides can initiate apoptotic cell death by acting directly on mitochondria and establish mitochondria-targeted photocaged ceramides as novel tools to elucidate the underlying mechanism with the spatiotemporal precision of light.