L166P mutant DJ-1 promotes cell death by dissociating Bax from mitochondrial Bcl-X_L

Background: Mutations or deletions in DJ-1/PARK7 gene are causative for recessive forms of early onset Parkinsons disease (PD). Wild-type DJ-1 has cytoprotective roles against cell death through multiple pathways. The most commonly studied mutant DJ-1(L166P) shifts its subcellular distribution to mitochondria and renders cells more susceptible to cell death under stress stimuli. We previously reported that wild-type DJ-1 binds to Bcl-X_L and stabilizes it against ultraviolet B (UVB) irradiation-induced rapid degradation. However, the mechanisms by which mitochondrial DJ-1(L166P) promotes cell death under death stimuli are largely unknown. Results: We show that DJ-1(L166P) is more prone to localize in mitochondria and it binds to Bcl-X _L more strongly than wild-type DJ-1. In addition, UVB irradiation significantly promotes DJ-1(L166P) translocation to mitochondria and binding to Bcl-X_L. DJ-1(L166P) but not wild-type DJ-1 dissociates Bax from Bcl-X_L, thereby leading to Bax enrichment at outer mitochondrial membrane and promoting mitochondrial apoptosis pathway in response to UVB irradiation. Conclusion: Our findings suggest that wild-type DJ-1 protects cells and DJ-1(L166P) impairs cells by differentially regulating mitochondrial Bax/Bcl-X_L functions.