HTRA2 encodes a mitochondrial serine protease that plays crucial roles in mitochondrial quality control and apoptosis regulation. The protein localizes primarily to mitochondria where it undergoes maturation by removal of N-terminal residues, exposing an AVPS tetrapeptide motif that enables binding and cleavage of Inhibitor of Apoptosis Proteins (IAPs) 1. HTRA2 exhibits dual chaperone-protease activity essential for maintaining mitochondrial proteome quality control and cellular homeostasis 1. Upon cellular stress, HTRA2 is released from mitochondria into the cytosol where it promotes apoptosis through caspase cascade activation 2. The protein demonstrates multifaceted regulation, with transcriptional control involving p53 and HSF1 transcription factors 3. HTRA2 dysfunction is implicated in several diseases, particularly neurodegenerative disorders. In Parkinson's disease, dopaminergic neurons show increased HTRA2 abundance alongside other mitochondrial proteases, suggesting compromised mitochondrial quality control 4. Heart failure patients exhibit downregulation of HTRA2 expression as part of broader mitochondrial quality control gene dysfunction 5. Additionally, HTRA2 modulates protein homeostasis by regulating PrP protein levels and influencing cancer cell behavior 6. This positions HTRA2 as a critical regulator of mitochondrial function and cellular survival.