Mitochondrial phosphorylation in apoptosis: flipping the death switch.

SIGNIFICANCE: Apoptosis is a complex cellular process subject to multiple layers of regulation. One such layer of regulation includes post-translational modifications, including acetylation and phosphorylation. In particular, phosphorylation of proteins directly implicated in the apoptotic process has been extensively documented. Importantly, these phosphorylation events often have functional consequences, affecting the onset of apoptotic cell death. RECENT ADVANCES: Large-scale proteomics studies have identified multiple novel phosphorylation sites on proteins involved in the apoptotic process. The delineation of the regulation and functional consequences of these phosphorylation events will be important in understanding the regulatory complexity of apoptosis. CRITICAL ISSUES: Multiple mitochondrial-localized proteins involved in apoptosis are functionally affected by phosphorylation, which can ultimately dictate whether a cell lives or dies. The dynamic interplay between these phosphorylated proteins and their regulatory enzymes is critical for understanding the complex cellular decision to undergo apoptosis. FUTURE DIRECTIONS: Detailed analysis of the kinetic and spatial regulation of phosphorylation events on apoptotic proteins, as well as how these dynamics influence the cell death process, will illuminate the complex interplay between the network of proteins that control the decision to undergo cell death.