Heat shock factor 4 regulates lysosome activity by modulating the αB-crystallin-ATP6V1A-mTOR complex in ocular lens

Cui, X., Feng, R., Wang, J., Du, C., Pi, X., Chen, D., Li, J., Li, H., Zhang, J., Zhang, J., Mu, H., Zhang, F., Liu, M., Hu, Y.
Biochimica et biophysica acta. General subjects   1864(3): 129496 (Journal)
Registered Authors
ATP6V1A, Lens epithelial cells, Lysosome acidification, Zebrafish, mTOR, αB-crystallin
MeSH Terms
  • Animals
  • Cell Line
  • Crystallins/metabolism
  • DNA-Binding Proteins/metabolism
  • Epithelial Cells/metabolism
  • Heat Shock Transcription Factors/genetics
  • Heat Shock Transcription Factors/metabolism*
  • Heat-Shock Proteins/metabolism
  • Heat-Shock Response
  • Humans
  • Lens, Crystalline/metabolism
  • Lysosomes/metabolism*
  • Lysosomes/physiology
  • Mice
  • Proteasome Endopeptidase Complex/metabolism
  • TOR Serine-Threonine Kinases/metabolism
  • Transcription Factors/metabolism
  • Ubiquitination
  • Vacuolar Proton-Translocating ATPases/metabolism
  • Zebrafish/metabolism
  • alpha-Crystallin B Chain/metabolism*
31786107 Full text @ BBA General Subjects
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.
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.
HSF4 deficiency or knock down of αB-crystallin elevates lysosomal pH and increases the ubiquitination and degradation of ATP6V1A by the proteasome. αB-crystallin localizes partially in the lysosome and interacts solely with the ATP6V1A protein of the V1 complex of V-ATPase. Furthermore, αB-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 αB-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 αB-crystallin. In the zebrafish model, HSF4 deficiency reduces αB-crystallin expression and elevates the lysosomal pH in lens tissues.
HSF4 regulates lysosomal acidification by controlling the association of αB-crystallin with ATP6V1A and mTOR and regulating ATP6V1A protein stabilization.
This study uncovers a novel function of αB-crystallin, demonstrating that αB-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.
Genes / Markers
Mutation and Transgenics
Human Disease / Model Data
Sequence Targeting Reagents
Engineered Foreign Genes
Errata and Notes