期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：2
页码：693-698
DOI：10.1073/pnas.1315017111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Protein tyrosine phosphatase (PTP){sigma} (PTPRS) was shown previously to be associated with susceptibility to inflammatory bowel disease (IBD). PTP{sigma}-/- mice exhibit an IBD-like phenotype in the intestine and show increased susceptibility to acute models of murine colitis. However, the function of PTP{sigma} in the intestine is uncharacterized. Here, we show an intestinal epithelial barrier defect in the PTP{sigma}-/- mouse, demonstrated by a decrease in transepithelial resistance and a leaky intestinal epithelium that was determined by in vivo tracer analysis. Increased tyrosine phosphorylation was observed at the plasma membrane of epithelial cells lining the crypts of the small bowel and colon of the PTP{sigma}-/- mouse, suggesting the presence of PTP{sigma} substrates in these regions. Using mass spectrometry, we identified several putative PTP{sigma} intestinal substrates that were hyper-tyrosine-phosphorylated in the PTP{sigma}-/- mice relative to wild type. Among these were proteins that form or regulate the apical junction complex, including ezrin. We show that ezrin binds to and is dephosphorylated by PTP{sigma} in vitro, suggesting it is a direct PTP{sigma} substrate, and identified ezrin-Y353/Y145 as important sites targeted by PTP{sigma}. Moreover, subcellular localization of the ezrin phosphomimetic Y353E or Y145 mutants were disrupted in colonic Caco-2 cells, similar to ezrin mislocalization in the colon of PTP{sigma}-/- mice following induction of colitis. Our results suggest that PTP{sigma} is a positive regulator of intestinal epithelial barrier, which mediates its effects by modulating epithelial cell adhesion through targeting of apical junction complex-associated proteins (including ezrin), a process impaired in IBD.
