CONICET | Buscador de Institutos y Recursos Humanos

VMP1 DependentSelective Mitophagy and Mitochondrial Fragmentation are Protective CellularMechanisms in PancreatitisMaria Ines VaccaroInstitute ofBiochemistry and Molecular Medicine (IBIMOL-CONICET), School of Pharmacy andBiochemistry, University of Buenos Aires, Buenos Aires, Argentina. VMP1 is anautophagy-related protein essential for autophagosome biogenesis. Autophagyinduced by VMP1 protects pancreas against acute pancreatitis through theinduction of selective types of autophagy. Premature Zymogen activation is andinitial cellular event in the pathogenesis of Acute pancreatitis. Zymophagy,which is a VMP1-related selective autophagy of zymogen granules that preventspancreas from self-digestion. Mitochondrial damage is another early cellular eventin acute pancreatitis and the consequent ATP depletion could eventually lead topancreatic cell death. Today we characterize mitophagy in Acute Pancreatitis(AP), its molecular mechanisms and its relationship with mitochondrial dynamicsduring selective autophagy induced by acute pancreatitis in animal and cellularmodels. In the cell model of AP, mitochondrial membrane potential is decreased 15%at 30min. Mitochondrial dynamics show significant induction of themitochondrial fission protein DRP1 at 15min, while the mitochondrial fusionprotein OPA1 is maximal at 1h. This is accompanied by an increase in the expressionof Parkin and recruitment of LC3-RFP. Redistribution of EGFP-VMP1 shows thesequestration of damaged mitochondria in autophagosomes. Mitophagy was confocalanalyzed through the dual pMITO-RFP-GFP specific probe, and electronicmicroscopy confirm mitophagy and mitochondrial dynamics in the cell model of AP.Interestingly, inhibition of mitophagy by downregulation of VMP1 leads to a dramaticdecrease of 60% in mitochondrial function. We evaluate the pathophysiological relevanceof these findings studying mitophagy, mitochondrial dynamics and function inthe rat model of AP. Mitochondrial respiration and ATP production is decreasedby 35% at 1h (p<0.01). DRP1 expression is maximal at 15min and is notdetectable after 30min, whereas increment of OPA1 expression is observed after1h. LC3II, VMP1 and Parkin expressions as well as isolation of autophagosomesdemonstrate VMP1-related mitophagy. All the parameters return to control valueswhen pancreatic morphology is recovered. Finally, the inhibition of selectiveautophagy leads to a dramatic decrease in mitochondrial function, suggesting aprotective role of VMP1-mitophagy. We have identified theDrp1-Parkin-VMP1-pathway of selective mitophagy in AP, which removes damagedmitochondria, allowing the recovery of energetic status by the OPA1 mediatedfusion and elongation. Our findings point to VMP1 dependent mitophagy andmitochondrial fragmentation as protective pancreatic cell mechanisms, providingnovel evidence of the potential relevance of VMP1-mediated selective autophagyin human complex diseases.