Browsing by Author "Yang, Zuolong"

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    AMDE-1 is a dual function chemical for autophagy activation and inhibition
    (PLoS, 2015-04-20) Li, Min; Yang, Zuolong; Vollmer, Laura L.; Gao, Ying; Fu, Yuanyuan; Lui, Cui; Chen, Xiaoyun; Liu, Peiqing; Vogt, Andreas; Yin, Xiao-Ming; Department of Pathology and Laboratory Medicine, IU School of Medicine
    Autophagy is the process by which cytosolic components and organelles are delivered to the lysosome for degradation. Autophagy plays important roles in cellular homeostasis and disease pathogenesis. Small chemical molecules that can modulate autophagy activity may have pharmacological value for treating diseases. Using a GFP-LC3-based high content screening assay we identified a novel chemical that is able to modulate autophagy at both initiation and degradation levels. This molecule, termed as Autophagy Modulator with Dual Effect-1 (AMDE-1), triggered autophagy in an Atg5-dependent manner, recruiting Atg16 to the pre-autophagosomal site and causing LC3 lipidation. AMDE-1 induced autophagy through the activation of AMPK, which inactivated mTORC1 and activated ULK1. AMDE-1did not affect MAP kinase, JNK or oxidative stress signaling for autophagy induction. Surprisingly, treatment with AMDE-1 resulted in impairment in autophagic flux and inhibition of long-lived protein degradation. This inhibition was correlated with a reduction in lysosomal degradation capacity but not with autophagosome-lysosome fusion. Further analysis indicated that AMDE-1 caused a reduction in lysosome acidity and lysosomal proteolytic activity, suggesting that it suppressed general lysosome function. AMDE-1 thus also impaired endocytosis-mediated EGF receptor degradation. The dual effects of AMDE-1 on autophagy induction and lysosomal degradation suggested that its net effect would likely lead to autophagic stress and lysosome dysfunction, and therefore cell death. Indeed, AMDE-1 triggered necroptosis and was preferentially cytotoxic to cancer cells. In conclusion, this study identified a new class of autophagy modulators with dual effects, which can be explored for potential uses in cancer therapy.
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    Golgi-associated LC3 lipidation requires V-ATPase in noncanonical autophagy
    (Nature Publishing Group, 2016-08-11) Gao, Ying; Liu, Yajun; Hong, Liang; Yang, Zuolong; Cai, Xinran; Chen, Xiaoyun; Fu, Yuanyuan; Lin, Yujie; Wen, Weijie; Li, Sitong; Liu, Xingguo; Huang, Heqing; Vogt, Andreas; Liu, Peiqing; Yin, Xiao-Ming; Li, Min; Department of Pathology and Laboratory Medicine, School of Medicine
    Autophagy is an evolutionarily conserved catabolic process by which cells degrade intracellular proteins and organelles in the lysosomes. Canonical autophagy requires all autophagy proteins (ATGs), whereas noncanonical autophagy is activated by diverse agents in which some of the essential autophagy proteins are dispensable. How noncanonical autophagy is induced and/or inhibited is still largely unclear. In this study, we demonstrated that AMDE-1, a recently identified chemical that can induce canonical autophagy, was able to elicit noncanonical autophagy that is independent of the ULK1 (unc-51-like kinase 1) complex and the Beclin1 complex. AMDE-1-induced noncanonical autophagy could be specifically suppressed by various V-ATPase (vacuolar-type H(+)-ATPase) inhibitors, but not by disturbance of the lysosome function or the intracellular ion redistribution. Similar findings were applicable to a diverse group of stimuli that can induce noncanonical autophagy in a FIP200-independent manner. AMDE-1-induced LC3 lipidation was colocalized with the Golgi complex, and was inhibited by the disturbance of Golgi complex. The integrity of the Golgi complex was also required for multiple other agents to stimulate noncanonical LC3 lipidation. These results suggest that the Golgi complex may serve as a membrane platform for noncanonical autophagy where V-ATPase is a key player. V-ATPase inhibitors could be useful tools for studying noncanonical autophagy.
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    Measurement of the Activity of the ATG4 Cysteine Proteases
    (Elsevier, 2017) Li, Min; Fu, Yuanyuan; Yang, Zuolong; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of Medicine
    While only one Atg4 is present in yeast, there are four Atg4 homologues in human and in mouse with different substrate specificities and catalytic efficiencies. The molecule Atg4 is a type of cysteine protease, and is known for its crucial roles in cleavage of the Atg8 family proteins before they can be conjugated to phospholipids, and also in cleavage of the conjugated Atg8 molecules from the membrane, a process known as deconjugation. Both processes are required for the maximal efficiency in autophagosome biogenesis. Atg4 could thus be a target for intervention of the autophagy process. It is thus important to measure Atg4 activity to determine and to modulate the autophagy function. Here we review the catalytic functions and regulatory mechanisms of human Atg4 proteases, and discuss the methodology for analyzing Atg4 activity in details.
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    The protease activity of human ATG4B is regulated by reversible oxidative modification
    (Taylor & Francis, 2020-10) Zheng, Xueping; Yang, Zuolong; Gu, Qianqian; Xia, Fan; Fu, Yuanyuan; Liu, Peiqing; Yin, Xiao-Ming; Li, Min; Pathology and Laboratory Medicine, School of Medicine
    Macroautophagy/autophagy plays a pivotal role in cytoplasmic material recycling and metabolic turnover, in which ATG4B functions as a "scissor" for processing pro-LC3 and lipidated LC3 to drive the autophagy progress. Mounting evidence has demonstrated the tight connection between ROS and autophagy during various pathological situations. Coincidentally, several studies have shown that ATG4B is potentially regulated by redox modification, but the underlying molecular mechanism and its relationship with autophagy is ambiguous. In this study, we verified that ATG4B activity was definitely regulated in a reversible redox manner. We also determined that Cys292 and Cys361 are essential sites of ATG4B to form reversible intramolecular disulfide bonds that respond to oxidative stress. Interestingly, we unraveled a new phenomenon that ATG4B concurrently formed disulfide-linked oligomers at Cys292 and Cys361, and that both sites underwent redox modifications thereby modulating ATG4B activity. Finally, increased autophagic flux and decreased oxidation sensitivity were observed in Cys292 and Cys361 double site-mutated cells under normal growth conditions. In conclusion, our research reveals a novel molecular mechanism that oxidative modification at Cys292 and Cys361 sites regulates ATG4B function, which modulates autophagy.