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

• Published in: The Journal of biological chemistry Vol. 293; no. 1; pp. 132 - 147
• Main Authors: Bansal, Megha, Moharir, Shivranjani C., Sailasree, S. Purnima, Sirohi, Kapil, Sudhakar, Cherukuri, Sarathi, D. Partha, Lakshmi, B. Jyothi, Buono, Mario, Kumar, Satish, Swarup, Ghanshyam
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05-01-2018; American Society for Biochemistry and Molecular Biology
• Subjects: AMP-activated kinase (AMPK); Animals; Atg12-5-16L1; autophagosome formation; Autophagosomes - metabolism; autophagy; Autophagy - physiology; Autophagy-Related Proteins - metabolism; Carrier Proteins - metabolism; Cell Biology; Cell Cycle Proteins; Eye Proteins - metabolism; Female; HEK293 Cells; Humans; Male; Membrane Proteins - metabolism; Membrane Transport Proteins; Mice; Mice, Knockout; Microtubule-Associated Proteins - metabolism; mutant; optineurin; phagophore maturation; Phosphate-Binding Proteins; phosphorylation; Protein Binding; Transcription Factor TFIIIA - metabolism; ubiquitin; Wipi2; autophagy; optineurin; AMP-activated kinase (AMPK); mutant; Wipi2; autophagosome formation; phosphorylation; Atg12-5-16L1; ubiquitin; phagophore maturation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M117.801944

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 microtubule-associated protein 1 light chain 3-II (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 knock-out 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 Ser-177 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.