Heat shock factor 4 regulates lysosome activity by modulating the αB-crystallin-ATP6V1A-mTOR complex in ocular lens
Heat shock factor 4 regulates lysosome activity by modulating the αB-crystallin-ATP6V1A-mTOR complex in ocular lens
复制标题
热休克因子 4 通过调节眼晶状体中的 α B-晶状体蛋白-ATP6V1A-mTOR 复合物来调节溶酶体活性
DOI：
10.1016/j.bbagen.2019.129496
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发表时间：
2020-03-01
影响因子：
3
通讯作者：
Hu, Yanzhong
中科院分区：
文献类型：
--
作者：
Cui, Xiukun;Feng, Ruiping;Hu, Yanzhong
Background: Germline mutations in heat shock factor 4 (HSF4) cause congenital cataracts. Previously, we have shown that HSF4 is involved in regulating lysosomal pH in mouse lens epithelial cell in vitro. However, the underlying mechanism remains unclear.Methods: HSF4-deficient mouse lens epithelial cell lines and zebrafish were used in this study. Immunoblotting and quantitative RT-PCR were used for expression analysis. The protein-protein interactions were tested with GST-pull downs. The lysosomes were fractioned by ultracentrifugation.Results: HSF4 deficiency or knock down of alpha B-crystallin elevates lysosomal pH and increases the ubiquitination and degradation of ATP6V1A by the proteasome. alpha B-crystallin localizes partially in the lysosome and interacts solely with the ATP6V1A protein of the V1 complex of V-ATPase. Furthermore, alpha B-crystallin can co-precipitate with mTORC1 and ATP6V1A in GST pull down assays. Inhibition of mTORC1 by rapamycin or siRNA can lead to dissociation of alpha B-crystallin from the ATP6V1A and mTORC1complex, shortening the half-life of ATP6V1A and increasing the lysosomal pH. Mutation of ATP6V1A/S441A (the predicted mTOR phosphorylation site) reduces its association with alpha B-crystallin. In the zebrafish model, HSF4 deficiency reduces alpha B-crystallin expression and elevates the lysosomal pH in lens tissues.Conclusion: HSF4 regulates lysosomal acidification by controlling the association of alpha B-crystallin with ATP6V1A and mTOR and regulating ATP6V1A protein stabilization.General significance: This study uncovers a novel function of alpha B-crystallin, demonstrating that alpha B-crystallin can regulate lysosomal ATP6V1A protein stabilization by complexing to ATP6V1A and mTOR. This highlights a novel mechanism by which HSF4 regulates the proteolytic process of organelles during lens development.
