Dokladny Karol, Ye Dongmei, Kennedy John C, Moseley Pope L, Ma Thomas Y
Internal Medicine-Gastroenterology and Hepatology, MSC10 5550, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
Am J Pathol. 2008 Mar;172(3):659-70. doi: 10.2353/ajpath.2008.070522. Epub 2008 Feb 14.
The heat stress (HS)-induced increase in occludin protein expression has been postulated to be a protective response against HS-induced disruption of the intestinal epithelial tight junction barrier. The aim of this study was to elucidate the cellular and molecular processes that mediate the HS-induced up-regulation of occludin expression in Caco-2 cells. Exposure to HS (39 degrees C or 41 degrees C) resulted in increased expression of occludin protein; this was preceded by an increase in occludin mRNA transcription and promoter activity. HS-induced activation of heat shock factor-1 (HSF-1) resulted in cytoplasmic-to-nuclear translocation of HSF-1 and binding to its binding motif in the occludin promoter region. HSF-1 activation was associated with an increase in occludin promoter activity, mRNA transcription, and protein expression; which were abolished by the HSF-1 inhibitor quercetin. Targeted HSF-1 knock-down by siRNA transfection inhibited the HSF-1-induced increase in occulin expression and junctional localization of occulin protein. Site-directed mutagenesis of the HSF-1 binding motif in the occludin promoter region inhibited HS-induced binding of HSF-1 to the occludin promoter region and subsequent promoter activity. In conclusion, our data show for the first time that the HS-induced increase in occludin protein expression is mediated by HSF-1 activation and subsequent binding of HSF-1 to the occludin promoter, which initiates a series of molecular and cellular events culminating in increased junctional localization of occludin protein.
热应激（HS）诱导的闭合蛋白表达增加被认为是针对HS诱导的肠道上皮紧密连接屏障破坏的一种保护反应。本研究的目的是阐明介导HS诱导的Caco-2细胞中闭合蛋白表达上调的细胞和分子过程。暴露于HS（39摄氏度或41摄氏度）导致闭合蛋白表达增加；这之前是闭合蛋白mRNA转录和启动子活性的增加。HS诱导的热休克因子-1（HSF-1）激活导致HSF-1从细胞质向细胞核转位，并与闭合蛋白启动子区域中的结合基序结合。HSF-1激活与闭合蛋白启动子活性、mRNA转录和蛋白表达增加相关；HSF-1抑制剂槲皮素可消除这些增加。通过siRNA转染靶向敲低HSF-1可抑制HSF-1诱导的闭合蛋白表达增加和闭合蛋白的连接定位。对闭合蛋白启动子区域中HSF-1结合基序进行定点诱变可抑制HS诱导的HSF-1与闭合蛋白启动子区域的结合以及随后的启动子活性。总之，我们的数据首次表明，HS诱导的闭合蛋白表达增加是由HSF-1激活以及随后HSF-1与闭合蛋白启动子结合介导的，这引发了一系列分子和细胞事件，最终导致闭合蛋白的连接定位增加。
