The study investigates the role of presenilin-associated rhomboid-like protein (PARL) in the proteolytic cleavage and stability of PINK1, a mitochondrial kinase involved in Parkinson's disease. PARL is found to mediate the cleavage of PINK1, generating a 52-kD form that is degraded by an MG132-sensitive protease. In the absence of PARL, PINK1 is constitutively degraded, stabilizing a 60-kD form. When mitochondrial membrane potential is dissipated, PINK1 accumulates as the full-length 63-kD form on the outer mitochondrial membrane, where it recruits Parkin to impaired mitochondria. This differential localization to the inner and outer mitochondrial membranes regulates PINK1 stability and function. The study also reports on a mutagenesis screen that identified amino acid residues in the transmembrane domain of PINK1 that affect PARL-mediated cleavage, providing insights into the regulation of PINK1 by mitochondrial membrane potential.The study investigates the role of presenilin-associated rhomboid-like protein (PARL) in the proteolytic cleavage and stability of PINK1, a mitochondrial kinase involved in Parkinson's disease. PARL is found to mediate the cleavage of PINK1, generating a 52-kD form that is degraded by an MG132-sensitive protease. In the absence of PARL, PINK1 is constitutively degraded, stabilizing a 60-kD form. When mitochondrial membrane potential is dissipated, PINK1 accumulates as the full-length 63-kD form on the outer mitochondrial membrane, where it recruits Parkin to impaired mitochondria. This differential localization to the inner and outer mitochondrial membranes regulates PINK1 stability and function. The study also reports on a mutagenesis screen that identified amino acid residues in the transmembrane domain of PINK1 that affect PARL-mediated cleavage, providing insights into the regulation of PINK1 by mitochondrial membrane potential.