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PTPN2 mutations cause epithelium-intrinsic barrier loss that synergizes with mucosal immune hyperactivation
Yan Y. Sweat, Jerrold R. Turner
Yan Y. Sweat, Jerrold R. Turner
Published September 1, 2021
Citation Information: J Clin Invest. 2021;131(17):e151414. https://doi.org/10.1172/JCI151414.
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Commentary

PTPN2 mutations cause epithelium-intrinsic barrier loss that synergizes with mucosal immune hyperactivation

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Abstract

It is clear that excessive mucosal immune activation and intestinal barrier dysfunction both contribute to inflammatory bowel disease (IBD) pathogenesis. T cell protein tyrosine phosphatase (TCPTP), which extinguishes signaling in immune cells, is linked to IBD and other immune-mediated diseases. In this issue of the JCI, Marchelletta and Krishnan et al. demonstrate that, in intestinal epithelial cells, TCPTP regulates tight junction permeability in vivo. Intestinal epithelial TCPTP loss potentiated cytokine-induced barrier loss, and this synergized with effects of TCPTP loss in immune cells. This work implicates a single mutation as the cause of distinct functional aberrations in diverse cell types and demonstrates how one genetic defect can drive multihit disease pathogenesis.

Authors

Yan Y. Sweat, Jerrold R. Turner

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Figure 1

A cycle of barrier loss and mucosal immune hyperactivation.

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A cycle of barrier loss and mucosal immune hyperactivation.
(A) WT cells...
(A) WT cells that express TCPTP are able to effectively dampen immune responses to limit changes in flux across the pore pathway (hatched green arrow), permeable to sodium and water, and the leak pathway (hatched blue arrow), permeable to larger molecules, including proteins and polysaccharides. (B) TCPTP loss in intestinal epithelial cells leads to epithelium-intrinsic signaling that upregulates claudin-2 expression (i). The resulting claudin-2–related increases in pore pathway (solid green arrow) permeability trigger excessive cytokine secretion in TCPTP-deficient immune cells. This cytokine release activates myosin light chain kinase (MLCK) to cause occludin internalization and leak pathway (solid blue arrow) permeability increases (ii). The exaggerated immune responses may also cause further increases in claudin-2 expression (iii). These cytokine-induced changes in permeabilities of and flux across pore and leak pathways trigger further immune activation, thereby creating a vicious cycle that leads to disease. In this manner, dysfunction of a single protein, TCPTP, results in excessive signaling in both epithelial and immune cells in development of a dysregulated cycle that leads to disease.

Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)

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