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

Abstract

Changes in barrier function of the gastrointestinal tract are thought to contribute to the inflammatory bowel diseases Crohn’s disease and ulcerative colitis. Previous work in our lab demonstrated that apical exposure of intestinal epithelial cell lines to serine proteases results in an increase in transepithelial electrical resistance (TER). However, the underlying mechanisms governing this response are unclear. We aimed to determine the requirement for proteolytic activity, epidermal growth factor receptor (EGFR) activation, and downstream intracellular signaling in initiating and maintaining enhanced barrier function following protease treatment using a canine intestinal epithelial cell line (SCBN). We also examined the role of phosphorylation of myosin regulatory light chain on the serine protease-induced increase in TER through. It was found that proteolytic activity of the serine proteases trypsin and matriptase is required to initiate and maintain the protease-mediated increase in TER. We also show that MMP-independent EGFR activation is essential to the sustained phase of the protease response, and that Src kinases may mediate EGFR transactivation. PI3-K and ERK1/2 signaling were important in reaching a maximal increase in TER following protease stimulation; however, their upstream activators are yet to be determined. CK2 inhibition prevented the increase in TER induced by serine proteases. The bradykinin B(2) receptor was not involved in the change in TER in response to serine proteases, and no change in phosphorylation of MLC was observed after trypsin or matriptase treatment. Taken together, our data show a requirement for ongoing proteolytic activity, EGFR transactivation, as well as downstream PI3-K, ERK1/2, and CK2 signaling in protease-mediated barrier enhancement of intestinal epithelial cells. The pathways mediating enhanced barrier function by proteases may be novel therapeutic targets for intestinal disorders characterized by disrupted epithelial barrier function.

Periplaneta americana Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Rats by Keap1/Nrf-2 Activation, Intestinal Barrier Function, and Gut Microbiota Regulation

“… Samak et al (2015) found that DSS treatment could increase tyrosine phosphorylation of occludin and ZO-1 in Caco-2 cells, indicating the disruption of tight junctions. A previous study ( Lahey et al, 2017 ) has demonstrated the promotion of tight junction, composed of various transmembrane proteins such as occluding, claudin family proteins and intracellular zona occludens (ZO) family proteins, could help to alleviate UC symptoms. In present study, representative proteins of tight junctions, i.e., ZO-1, occludin and claudin-1, were evaluated, showing that DSS treatment could down-regulate the tight junction proteins in colons of UC rats ( Figure 5 ).…”

Serine proteases at the cutting edge of IBD: Focus on gastrointestinal inflammation

“…Stimulating actin cytoskeleton contraction, as assessed through myosin light chain phosphorylation in epithelial cells has been involved in tight junction (TJ) modulation 35‐37 . Another avenue of regulation is through TJ phosphorylation by upstream kinases including protein kinase C‐zeta (PKCζ) 38,39 . In this context, the serine proteases trypsin, chymotrypsin, and elastase have been suggested as essential for epithelial integrity as they increase ion transport across human intestinal cells while decreasing paracellular conductance 40 .…”

Proteomic Analysis of Peri-Wounding Tissue Expressions in Extracorporeal Shock Wave Enhanced Diabetic Wound Healing in a Streptozotocin-Induced Diabetes Model

“…Studies showed the serpin involved in EGFR activation and epithelial barrier [12,21]. EGFR is an important role in angiogenesis and cell proliferation via regulating the Raf-MEK-ERK signaling [13,14].…”

“…The study showed serpin as an epithelial barrier involved in epidermal growth factor receptor (EGFR) activation [12]. Cell proliferation and angiogenesis are important roles via regulating the EGFR-MAPK pathway [13,14].…”