Journal of Gastroenterology 2015-11-01

Par-3 modulates intestinal epithelial barrier function through regulating intracellular trafficking of occludin and myosin light chain phosphorylation.

Min Yu, Songwei Yang, Yuan Qiu, Guoqing Chen, Wensheng Wang, Chao Xu, Wenqiang Cai, Lihua Sun, Weidong Xiao, Hua Yang

Index: J. Gastroenterol. 50 , 1103-13, (2015)

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Abstract

Tight junctions play a critical role in the maintenance of intestinal barrier function. Partitioning-defective protein 3 (Par-3) can regulate intestinal barrier function through the modulation of tight junction assembly and cell polarity. However, the mechanisms are still not fully understood.Adult C57BL/6 mice were treated with dextran sulfate sodium for 7 days, and segments of colon were harvested for immunofluorescent staining of Par-3. Caco-2 intestinal epithelial cells were treated with tumor necrosis factor α (TNF-α) for 24 h, and Par-3 expression was detected by Western blot analysis and immunofluorescence. Additionally, Caco-2 cells were treated with Par-3 small interfering RNA, and altered expression and subcellular localization of tight junction proteins were studied by Western blot analysis and immunofluorescence. Furthermore, the interaction between Par-3 and myosin light chain (MLC) was detected by immunoprecipitation.Par-3 was downregulated in murine dextran sulfate sodium induced acute inflammation and TNF-α-treated Caco-2 cells. Depletion of Par-3 expression by small interfering RNA delayed intestinal epithelial barrier development in Caco-2 cells. This regulation was due to the redistribution of the tight junction protein occludin rather than the altered total levels of tight junction proteins. Par-3 silencing blocked the trafficking of occludin from or through the Golgi complex to the cell surface, and dramatically induced occludin accumulated at the Golgi complex. Importantly, Par-3 can interact with MLC, and loss of Par-3 upregulated MLC kinase expression and MLC phosphorylation, which contributed to intestinal epithelial barrier dysfunction.These results indicate that Par-3 plays an important role in the modulation of intestinal barrier function by regulating delivery of occludin as well as suppression of MLC phosphorylation.