The effect of transient receptor potential vanilloid 4 on the intestinal epithelial barrier and human colonic cells was affected by tyrosine-phosphorylated claudin-7

Abstract

TRPV4 is a type of nonselective cation channel, and activation of TRPV4 in the gastrointestinal tract causes experimental colitis in mice. A previous study found that tyrosine-phosphorylated claudin-7 is increased in experimental colitis. The relationship between tyrosine-phosphorylated claudin-7 and TRPV4 remains undefined. In the present study, we developed a claudin-7 mutant by replacing tyrosine with glutamic acid at position 210, named cld7-Y210E colonic cells. We found that activation of TRPV4 by GSK1016790A increased the permeability of control colonic cell monolayers, which was decreased by the TRPV4 antagonist HC067047. In monolayers of cld7-Y210E colonic cells, no differences in permeability were found between GSK1016790A and HC067047 treatments. GSK1016790A increased the aggregation of claudin-7 at the cell membrane in control colonic cells, and the effect was diminished by HC067047. In cld7-Y210E colonic cells, neither GSK1016790A nor HC067047 apparently changed the aggregation of claudin-7. Neither GSK1016790A nor HC067047 altered the TRPV4 protein level in vector colonic cells. In cld7-wild colonic cells, GSK1016790A did not alter the TRPV4 protein level, while HC067047 increased the TRPV4 protein level. The TRPV4 protein level was increased in cld7-Y210E colonic cells, decreased by GSK1016790A and further decreased by HC067047. Calcium influx was not significantly changed in the control colonic cells treated with GSK1016790A. However, GSK1016790A significantly increased calcium influx in cld7-Y210E colonic cells. We concluded that tyrosine-phosphorylated claudin-7 affects the TRPV4-modulated intestinal epithelial barrier, TRPV4-mediated calcium influx, and the protein expression of TRPV4 in human colonic cells. We suggest that tyrosine-phosphorylated claudin-7 affects the TRPV4-modulated intestinal epithelial barrier, which might be related to TRPV4 expression and TRPV4-mediated calcium influx.

Keywords: Claudin-7; Intestinal epithelial barrier; Transient receptor potential vanilloid 4; Tyrosine phosphorylation.