HSP90β Regulates Cell Proliferation through Interaction with the charged multivesicular body protein 4B (CHMP4B), A Novel Client Protein

Abstract

Purpose : HSP90β is an important chaperone and plays a fundamental role in maintaining cellular homeostasis in most eukaryotes. Whether it is implicated in lens development and pathogenesis remains largely unknown. Here we show that HSP90β can regulate cell proliferation in the ocular lens through direct interaction with CHMP4B, a novel client protein and also an important member of the ESCRT pathway.

Methods : Morpholino oligos and CRISPR/Cas9 technology were used to silence HSP90β in zebrafish. H.E. staining was used to examine the morphology of the wild type and HSP90β silenced zebrafish; Mouse lens epithelial cell line, aTN4-1 and human lens epithelial cell line FHL124 were used to study the mechanisms of HSP90β regulation on cell proliferation. 17-AAG was used to inhibit the activity of HSP90β in the above cell lines as well as in wildtype zebrafish. Mass Spectrometry and Co-IP assay were used to verify the interaction between HSP90β and CHMP4B. QRT-PCR and Western blot were used to analyze gene expression.

Results : Silence of HSP90β in zebrafish causes cataracts, microphthalmia and other eye abnormality. Mass Spectrometry and Co-IP assays reveal that HSP90β directly interacts with CHMP4B. Silence of HSP90β causes upregulation of both CHMP4B and Ki67, which leads to abnormal proliferation of lens epithelial cells followed by enhanced apoptosis via p53-Bak/Bim pathway.

Conclusions : Our results demonstrated that HSP90β plays a fundamental role during lens development. Through interactions with CHAMP4B and p53, HSP90β suppresses abnormal cell proliferation and apoptosis to guard normal lens development.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.