High Temperature Requirement Factor A2 (HTRA2)

HTRA2 encodes a serine protease. HtrA2, also known as Omi, is a mitochondrially-located serine protease. HtrA2 can be released from the mitochondria during apoptosis and uses its four most N-terminal amino acids to mimic a caspase and be recruited by IAP caspase inhibitors such as XIAP and CIAP1/2. Once bound, the serine protease cleaves the IAP, reducing the cell's inhibition to caspase activation. Additionally, HtrA2 has a PDZ domain, though little is known about its ability to bind PDZ binding motif peptides. HtrA2 has recently been identified as a gene related to Parkinson's disease. Mutations in Htra2 have been found in patients suffering from Parkinson's disease. Additionally, mice lacking HtrA2 have a parkinsonian phenotype. This suggests that HtrA2 is linked to Parkinson's disease progression in humans and mice.