Autophagy
·
2023
·
IF 13.3
Chaonan Sun,Yuxin Chen,Qianqian Gu,Yuanyuan Fu,Yao Wang,Cui Liu,Huazhong Xie,Yong Liao,Zhihua Zheng,Peiqing Liu,Min Li
ATG4B is a core protein and essential for cleaving precursor MAP1LC3/LC3 or deconjugating lipidated LC3-II to drive the formation of autophagosomes. The protein stability and activity of ATG4B regulated by post-translational modification (ubiquitination) will directly affect macroautophagy/autophagy. However, the mechanism involved in ATG4B ubiquitination is largely unclear. In this study, a new E3 ligase of ATG4B, UBE3C, was identified by mass spectra. UBE3C mainly assembles K33-branched ubiquitin chains on ATG4B at Lys119 without causing ATG4B degradation. In addition, the increased ubiquitination of ATG4B caused by UBE3C overexpression inhibits autophagy flux in both normal and starvation conditions, which might be due to the reduced activity of ATG4B and ATG4B-LC3 interaction. This reduction could be reversed once the lysine 119 of ATG4B was mutated to arginine. More important, under starvation conditions the interaction between ATG4B and UBE3C apparently decreased followed by the removal of the K33-branched ubiquitin chain of ATG4B. Thus, starvation-induced autophagy could be partially suppressed by an increased ubiquitination level of ATG4B. In conclusion, our research reveals a novel modification mode of ATG4B in which UBE3C can fine tune ATG4B activity by specific ubiquitination regulating autophagy without causing ATG4B degradation.
研究领域:
细胞生物学
·
分子生物学
·
生物化学
✓ 已验证
DOI
PubMed
高影响因子
Redox Biology
·
2022
·
IF 10.787
Fan Xia,Yuanyuan Fu,Huazhong Xie,Yuxin Chen,Dongmei Fang,Wei Zhang,Peiqing Liu,Min Li
Autophagy is an evolutionarily conserved self-protecting mechanism implicated in cellular homeostasis. ATG4B plays a vital role in autophagy process via undertaking priming and delipidation of LC3. Chemical inhibitors and regulative modifications such as oxidation of ATG4B have been demonstrated to modulate autophagy function. Whether and how ATG4B could be regulated by metal ions is largely unknown. Copper is an essential trace metal served as static co-factors in redox reactions in physiology process. Excessive accumulation of copper in ATP7B mutant cells leads to pathology progression such as insoluble Mallory body (MB) in Wilson disease (WD). The clearance of MB via autophagy pathway was thought as a promising strategy for WD. Here, we discovered that copper ion instead of other ions could inhibit the activity of ATG4B followed by autophagy suppression. In addition, copper could induce ATG4B oligomers depending on cysteine oxidation which could be abolished in reduced condition. Copper also promotes the formation of insoluble ATG4B aggregates, as well as p62-and ubiquitin-positive aggregates, which is consistent with the components of MB caused by copper overload in WD cell model. Importantly, overexpression of ATG4B could partially reduce the formation of MB and rescue impaired autophagy. Taken together, our results uncovered for the first time a new damage mechanism mediated by copper and implied new insights of the crosstalk between the toxicity of copper and autophagy in the pathogenesis of WD.
研究领域:
细胞生物学
·
病理学
·
代谢
✓ 已验证
DOI
PubMed
高影响因子
BIOELECTROCHEMISTRY
·
2026
·
IF 4.9
Jian Li,Tong Wang,Wenyuan Zhang,Lu Chen,Min Peng,Na Li,Lu Zhang
Simultaneous detection of key autophagic proteases—autophagy-related 4B (ATG4B) and cathepsin B (CTSB)—in living cells remains challenging, yet it is essential for understanding their dual regulatory roles in tumor progression and immune modulation, such as major histocompatibility complex I (MHC-I)-mediated antigen presentation. To address this gap, we developed a dual-channel peptide-functionalized glass nanopipette for simultaneous quantification of intracellular ATG4B and CTSB activities. Each channel is chemically modified with a protease-specific peptide substrate; upon specific cleavage by the target protease, the ionic current through the corresponding channel is altered, enabling label-free detection. The nanopipette exhibits exceptional selectivity, with current responses to ATG4B and CTSB over three-fold higher than those induced by common biological interferents (e.g., cations, amino acids, and redox-active molecules), and demonstrates acceptable stability for cellular assays. In cell studies, it successfully distinguished autophagy levels between normal hepatocytes and hepatocellular carcinoma cells, and further captured rapamycin-induced autophagy enhancement. Given the established correlation between protease activity and MHC-I expression, this method enables direct assessment of autophagy and indirect evaluation of immunogenicity for immunotherapy prediction.
✓ 已验证
DOI
PubMed
高影响因子
Autophagy
·
2018
·
IF 11.1
Yuanyuan Fu,Liang Hong,Jiecheng Xu,Guoping Zhong,Qiong Gu,Qianqian Gu,Yanping Guan,Xueping Zheng,Qi Dai,Xia Luo,Cui Liu,Zhiying Huang,Xiao-Ming Yin,Peiqing Liu,Min Li
Human Atg4 homologs are cysteine proteases, which play key roles in the macroautophagy/autophagy process by cleaving Atg8 homologs for conjugation to lipid membranes and for deconjugation of Atg8 homologs from membranes. Expression of ATG4B is significantly increased in colorectal cancer cells compared to normal cells, suggesting that ATG4B may be important for cancer biology. Inhibition of ATG4B may reduce the autophagy activity, thereby sensitizing cancer cells to therapeutic agents. Thus, developing specific and potent ATG4B inhibitors for research as well as for potential therapeutic uses is highly needed. In this study, we integrated in silico screening and in vitro assays to discover a potent ATG4B inhibitor, named S130, from a noncommercial library. This chemical binds to ATG4B with strong affinity and specifically suppresses the activity of ATG4B but not other proteases. S130 did not cause the impairment of autophagosome fusion, nor did it result in the dysfunction of lysosomes. Instead, S130 might attenuate the delipidation of LC3-II on the autolysosomes to suppress the recycling of LC3-I, which normally occurs after LC3-II cleavage by ATG4B. Intriguingly, S130 induced cell death, which was accompanied with autophagy stress and could be further exacerbated by nutrient deprivation. Such cytotoxicity could be partially reversed by enhancing ATG4B activity. Finally, we found that S130 was distributed in tumor tissues in vivo and was also effective in arresting the growth of colorectal cancer cells. Thus, this study indicates that ATG4B is a potential anticancer target and S130 might be a novel small-molecule candidate for future cancer therapy.
研究领域:
癌症生物学
·
药理学
·
分子生物学
·
细胞生物学
✓ 已验证
DOI
PubMed
高影响因子
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