Cellular and molecular mechanisms of heat stress-induced up-regulation of occludin protein expression: regulatory role of heat shock factor-1.
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.
Dokladny
Karol
K
Internal Medicine-Gastroenterology and Hepatology, MSC10 5550, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
Ye
Dongmei
D
Kennedy
John C
JC
Moseley
Pope L
PL
Ma
Thomas Y
TY
D018938:Caco-2 Cells; D004268:DNA-Binding Proteins / Q000502:physiology*; D000076249:Heat Shock Transcription Factors; D018882:Heat Stress Disorders / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D062793:Occludin; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding; D021381:Protein Transport; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology*; D015854:Up-Regulation / Q000235:genetics
D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D014157:Transcription Factors