Mitochondrial Selective Autophagy (mitophagy) During Dengue Infection

Mitophagy (mitochondrial‐selective autophagy) and mitochondrial dynamics co‐ordinate to maintain mitochondrial homeostasis and quality control. Mutation in the proteins involved in mitophagy such as PARKIN and PINK1 have been linked to neurodegenerative disorders like Parkinson's and Alzheimer's. Mitophagy plays a key role in eliminating damaged mitochondria and keeps the accumulation of mitochondrial garbage in check. Damaged mitochondria can trigger a vicious cycle of mitochondrial dysregulation and damage hence defective clearance of damaged mitochondria further exacerbates the mitochondrial injury. Mitochondrial injury can lead to the release of mitochondrial damage associated molecular patterns (MTDs) into the cellular cytoplasm and extracellular milieu. Defective mitophagy has been implicated in hyperactivation of inflammasomes and inflammatory signalling. We observe that Dengue virus (DENV) promotes substantial mitochondrial injury in hepatic cells. During the initial phase of infection Dengue‐infected cells display tubular mitochondrial network, however as the infection proceeds, we observe accumulation of abnormally swollen mitochondria suggestive of severe mitochondrial injury. Scoring for mitochondrial injury by quantitating the average number of abnormally swollen mitochondria in Dengue infected cells suggested a time‐dependent increase in mitochondrial injury in infected cells. Monitoring autophagy flux with mRFP‐GFP‐LC3 tandem construct, we observed that Dengue promotes global autophagy. Further, we confirmed the same by monitoring LC3‐II levels via immunoblot analysis. Subsequently, we also monitored mitophagy levels in Dengue‐infected cells using a novel mitochondria‐specific traffic light reporter mito‐mRFP‐GFP. In contrast to the global autophagy, we observed that Dengue inhibits mitochondrial‐selective autophagy. CCCP‐induced mitophagy was also attenuated in Dengue‐infected cells. Interestingly, PINK‐1 mediated Parkin phosphorylation increased in a time‐dependent fashion suggesting that PINK‐1 and Parkin effectively coordinate to flag the damaged mitochondria for elimination via mitophagy in Dengue‐infected cells. In agreement, we also observed the colocalization of the autophagosomal marker LC3‐GFP with mitochondria in Dengue‐infected cells. However, we did not observe significant colocalization of mitochondria with lysosomes in DENV‐infected cells. Overall our observations suggest a defect in the downstream events of mitophagy in Dengue infection. A defect in mitophagy inhibits the rapid turnover of damaged mitochondria leading to their accumulation in Dengue‐infected cells. Hence, we speculate that defective mitophagy plays a major role in the exponential increase of inflammation during dengue pathogenesis. Currently, we are exploring the underlying mechanism involved in the attenuation of mitophagy in Dengue‐infected cells. Our studies will enhance knowledge on molecular mechanisms that underlie Dengue pathogenesis and provide new avenues for development of potential therapeutic strategies.Support or Funding InformationWellcome Trust‐ DBT India Alliance Intermediate fellowship ‐ IA/I/15/1/501826 awarded to Dr G H Syed.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.