Signaling pathways induced by serine proteases to increase intestinal epithelial barrier function

Area of Science:

• Gastroenterology
• Cell Biology
• Molecular Biology

Background:

• Altered gastrointestinal barrier function is implicated in inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative colitis.
• Previous studies showed serine proteases increase transepithelial electrical resistance (TER) in intestinal cells, but mechanisms remain unclear.

Purpose of the Study:

• To elucidate the mechanisms of protease-induced enhancement of intestinal epithelial barrier function.
• To determine the roles of proteolytic activity, epidermal growth factor receptor (EGFR) activation, and intracellular signaling in this process.

Main Methods:

• Utilized a canine intestinal epithelial cell line (SCBN).
• Investigated the requirement for proteolytic activity, EGFR activation, and downstream signaling (PI3-K, ERK1/2, CK2).
• Assessed the involvement of Src kinases and the bradykinin B(2) receptor; examined myosin light chain (MLC) phosphorylation.

Main Results:

• Proteolytic activity of trypsin and matriptase is essential for initiating and maintaining the increase in TER.
• MMP-independent EGFR activation is crucial for the sustained response, potentially mediated by Src kinases.
• PI3-K, ERK1/2, and CK2 signaling pathways are important for maximal TER increase; bradykinin B(2) receptor and MLC phosphorylation were not involved.

Conclusions:

• Ongoing proteolytic activity and EGFR transactivation are required for protease-mediated intestinal epithelial barrier enhancement.
• Downstream signaling via PI3-K, ERK1/2, and CK2 pathways contributes to this barrier improvement.
• These identified pathways represent potential therapeutic targets for disorders involving disrupted intestinal barrier function.