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Pacer Is a Mediator of mTORC1 and GSK3-TIP60 Signaling in Regulation of Autophagosome Maturation and Lipid Metabolism
- Cheng, Xiawei, Ma, Xiuling, Zhu, Qi, Song, Dandan, Ding, Xianming, Li, Lin, Jiang, Xiao, Wang, Xinyi, Tian, Rui, Su, Hua, Shen, Zhirong, Chen, She, Liu, Ting, Gong, Weihua, Liu, Wei, Sun, Qiming
- Molecular cell 2019 v.73 no.4 pp. 788-802.e7
- acetylation, autophagy, dephosphorylation, droplets, glycogen, homeostasis, lipid metabolism, lipids, liver, liver cirrhosis, mice
- mTORC1 and GSK3 play critical roles in early stages of (macro)autophagy, but how they regulate late steps of autophagy remains poorly understood. Here we show that mTORC1 and GSK3-TIP60 signaling converge to modulate autophagosome maturation through Pacer, an autophagy regulator that was identified in our recent study. Hepatocyte-specific Pacer knockout in mice results in impaired autophagy flux, glycogen and lipid accumulation, and liver fibrosis. Under nutrient-rich conditions, mTORC1 phosphorylates Pacer at serine157 to disrupt the association of Pacer with Stx17 and the HOPS complex and thus abolishes Pacer-mediated autophagosome maturation. Importantly, dephosphorylation of Pacer under nutrient-deprived conditions promotes TIP60-mediated Pacer acetylation, which facilitates HOPS complex recruitment and is required for autophagosome maturation and lipid droplet clearance. This work not only identifies Pacer as a regulator in hepatic autophagy and liver homeostasis in vivo but also reveals a signal integration mechanism involved in late stages of autophagy and lipid metabolism.