5 years ago

Optineurin promotes autophagosome formation by recruiting the autophagy-related Atg12-5-16L1 complex to phagophores containing the Wipi2 protein.

D Partha Sarathi, B Jyothi Lakshmi, Mario Buono, Kapil Sirohi, Megha Bansal, Ghanshyam Swarup, Cherukuri Sudhakar, Satish Kumar, S Purnima Sailasree, Shivranjani C Moharir
Autophagy is a quality-control mechanism that helps to maintain cellular homeostasis by removing damaged proteins and organelles through lysosomal degradation. During autophagy, signaling events lead to the formation of a cup-shaped structure called the phagophore that matures into the autophagosome. Recruitment of the autophagy-associated Atg12-5-16L1 complex to wipi2-positive phagophores is crucial for producing LC3-II, which is required for autophagosome formation. Here, we explored the role of the autophagy receptor optineurin (Optn) in autophagosome formation. Fibroblasts from Optn knockout mouse showed reduced LC3-II formation, and a lower number of autophagosomes and autolysosomes during both basal and starvation-induced autophagy. However, the number of Wipi2-positive phagophores was not decreased in Optn-deficient cells. We also found that the number of Atg12/16L1-positive puncta and recruitment of the Atg12-5-16L1 complex to Wipi2-positive puncta are reduced in Optn-deficient cells. Of note, Optn was recruited to Atg12-5-16L1-positive puncta, and interacted with Atg5 and also with Atg12-5 conjugate. A disease-associated Optn mutant, E478G, defective in ubiquitin binding, was also defective in autophagosome formation and recruitment to the Atg12-5-16L1-positive puncta. Moreover, we noted that Optn phosphorylation at S177 was required for autophagosome formation but not for Optn recruitment to the phagophore. These results suggest that Optn potentiates LC3-II production and maturation of the phagophore into the autophagosome, by facilitating the recruitment of the Atg12-5-16L1 complex to Wipi2-positive phagophores.

Publisher URL: http://doi.org/10.1074/jbc.M117.801944

DOI: 10.1074/jbc.M117.801944

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