Abstract 3298: Parkin Complex Protects Mitochondrial Function Through Mitochondrial Quality Control Mediated by Bcl2 in Preconditioned Hearts
Mitochondria are vulnerable to stress. Autophagic removal of mitochondria reduces mitochondria-induced cell death. However, the selectivity of mitophagy is unknown. Mitochondrial turnover is a reflection of mitochondrial degradation via autophagy. Parkin, an E3 ubiquitin ligase, has been shown to selectively remove damaged mitochondria through autophagy. Parkin and its 110kDa complex are expressed in the heart, but no study has elucidated Parkin function in the heart. We previously reported that autophagy, via Atg5, was induced in hearts treated with adenosine A1 agonist (CCPA), a preconditioning compound. Here, we investigated the roles of parkin in normal and CCPA-treated hearts. CCPA caused an increase in Bcl-2 in both mitochondria and cytosol by analysis of subcellular fractionation; the parkin 110kDa-complex was present in both the mitochondrial fraction and cytosol, which was not changed with CCPA administration. Immunostaining revealed colocalization of parkin with the mitochondrial marker COX IV. Inhibition of Bcl-2 with Bcl-2 inhibitor(B-in) resulted in 80% reduction of mitochondria parkin in control hearts, whereas CCPA attenuated this loss of parkin (30% reduction), suggesting that CCPA and Bcl-2 may function independently to stabilize parkin in the mitochondria. To examine whether parkin protects mitochondria against swelling, we isolated cardiac mitochondria from mice treated with saline, CCPA, B-in, or CCPA+B-in for 30min. Mitochondrial swelling was greatest in mitochondria from B-in treated hearts, whereas CCPA attenuated swelling. To further explore the role of parkin in vivo, hearts were subjected to 30 min regional ischemia and 24hrs reperfusion. There was significantly more parkin in mitochondria from CCPA-treated hearts, and this was associated with reduced cytochrome c release. Interestingly, in hearts subjected to I/R, inhibition of Bcl-2 resulted in 90% reduction in mitochondria-associated parkin in both CCPA and saline-hearts associated with similar extent of cytochrome c release. Researchers have shown that mitochondrial parkin in neurons involves Atg5. These results suggest that parkin and Bcl-2 stabilize the mitochondria and may play a role in selective removal of damaged mitochondria through autophagy.