title: Hsf4 counteracts Hsf1 transcription activities and increases lens epithelial cell survival in vitro.
abstract: The interplay between Hsf4 and Hsf1 plays an important role in the regulation of lens homeostasis. However, the mechanism of the intermolecular association involved is still unclear. In this paper, we find that reconstitution of Hsf4b into Hsf4-/- lens epithelial (mLEC/Hsf4-/-) cells can simultaneously downregulate Hsp70 expression and upregulate the expression of small heat shock proteins Hsp25 and αB-crystallin at both RNA and protein levels. ChIP assay results indicate Hsf4b, which binds to the promoters of Hsp90α, Hsp70.3, Hsp25 and αB-crystallin but not Hsp70.1, can inhibit Hsf1 binding to Hsp70.3 promoter and the heat shock mediated Hsp70 promoter activity by reducing Hsf1 protein expression. Hsf4b N-terminal hydrophobic region can interact with Hsf1 N-terminal hydrophobic region. Their interaction impairs Hsf1's intramolecular interaction between the N- and C-terminal hydrophobic regions, leading to Hsf1's cytosolic retention and protein degradation. Both lysosome inhibitors (chloroquine, pepstatin A plus E64d) and proteasome inhibitor MG132 can inhibit Hsf4-mediated Hsf1 protein degradation, but MG132 can induce Hsf1 activation as well. Upregulation of Hsf4b can significantly inhibit cisplatin and staurosporine induced lens epithelial cell apoptosis through direct upregulation of Hsp25 and αB-crystallin expression. Taken together, our results imply that upregulation of Hsf4b modulates the expression pattern of heat shock proteins in lens tissue by either directly binding to their promoters or promoting Hsf1 protein degradation. Moreover, upregulation of Hsf4b protects lens cell survival by upregulating anti-apoptotic pathways. These studies reveal a novel regulatory mechanism between Hsf1 and Hsf4b in modulating lens epithelial cell homeostasis.
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Xiukun
authors.initials: X
authors.lastname: Cui
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Pan Pan
authors.initials: PP
authors.lastname: Xie
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Pan Pan
authors.initials: PP
authors.lastname: Jia
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Lou
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Guoqing
authors.initials: G
authors.lastname: Dun
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Shulian
authors.initials: S
authors.lastname: Li
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Guangchao
authors.initials: G
authors.lastname: Liu
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China; Department of Cell Biology and Anatomy, Georgia Regents University, Augusta, GA 30912, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Dong
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China.
authors.forename: Yuanfang
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Henan Key laboratory of Molecular and Cellular Immunology, Department of Cell Biology and Genetics, Henan University School of Medicine, Jin-Ming Road, Kaifeng, Henan 475004, China. Electronic address: hyz@henu.edu.cn.
authors.forename: Yanzhong
authors.initials: Y
authors.lastname: Hu
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006706:Homeostasis / Q000235:genetics; D007908:Lens, Crystalline / Q000166:cytology* / Q000502:physiology; D051379:Mice; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; C486113:Hsbp1 protein, mouse; C490017:Hsf1 protein, mouse; C484462:Hsf4 protein, mouse; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D014157:Transcription Factors
keywords: Apoptosis; Hsf1; Hsf4; Lysosome and lens epithelial cell