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We previously showed that the RGD integrin-binding sequence-containing ADAM15 is expressed in intestinal epithelial cells (IEC). The presence of a RGD-containing disintegrin protein in IEC suggested a potential role of ADAM15 in cell adhesion involving these cells. As already described in NIH3T3 cells, our previous finding of the inhibition of IEC wound-healing by ADAM15 overexpression could-be due to enhanced cell-cell interactions. Therefore, our recent finding of ADAM15 up-regulation during inflammatory bowel disease (IBD) led us to examine the roles of ADAM15 in cell adhesion relevant to IBD. T cell adhesion on IEC was assessed using Jurkat cells and Caco2-BBE monolayers. Our results show that an anti-ADAM15 ectodomain antibody inhibited the binding of Jurkat cells on Caco2-BBE monolayers. Overexpression of ADAM15 in Caco2-BBE cells enhanced Jurkat cells binding and overexpression of ADAM15 in Jurkat cells enhanced homotypic adhesion. Both the mutation of the RGD domain and the deletion of the cytoplasmic tail decreased these cell-cell interactions. Here we demonstrate that 1) ADAM15 is involved in T cell adhesion to IEC as well as T cell aggregation; 2) both the RGD motif and the cytoplasmic tail of ADAM15 are involved for these cell-cell interactions. Altogether these findings point to ADAM15 as a possible. therapeutic target for prevention of inappropriate T cell activation involved in some pathologies. [ABSTRACT FROM AUTHOR]

Intestinal epithelial cells respond to inflammatory extracellular stimuli by activating mitogen activated protein kinase (MAPK) signaling, which mediates numerous pathophysiological effects, including intestinal inflammation. Here, we show that a novel isoform of SPS1-related proline alanine-rich kinase (SPAK/STE20) is involved in this inflammatory signaling cascade. We cloned and characterized a SPAK isoform from inflamed colon tissue, and found that this SPAK isoform lacked the characteristic PAPA box found in SPAK. The SPAK isoform was found in inflamed and non-inflamed colon tissues as well as Caco2-BBE cells, but other tissues, such as liver, spleen, brain, prostate and kidney. In vitro analyses demonstrated that the SPAK isoform possessed serine/threonine kinase activity, which could be abolished by a substitution of isoleucine for the lysine at position 34 in the ATP-binding site of the catalytic domain. Treatment of Caco2-BBE cells with the pro-inflammatory cytokine, interferon gamma, induced expression of the SPAK isoform. Over-expression of the SPAK isoform in Caco2-BBE cells led to nuclear translocation of an N-terminal fragment of the SPAK isoform, as well as activation of p38 MAP kinase signaling cascades and increased intestinal barrier permeability. These findings collectively suggest that pro-inflammatory cytokine signaling may induce expression of this novel SPAK isoform in intestinal epithelia, triggering the signaling cascades that govern intestinal inflammation. [ABSTRACT FROM AUTHOR]

The intestinal epithelial apical membrane transporter, hPepT1, is expressed in the small intestine and in colonic tissue from inflammatory bowel disease, with little or no expression seen in the normal colon. The flora constituents of the colon are involved in inflammatory bowel disease, but no previous study has examined whether bacterial products can affect PepT1 expression and activity. To examine this issue, we stimulated Caco2-BBE cells with sodium butyrate, a short-chain fatty acid produced in large amounts by bacterial fermentation. Our results revealed that butyrate dose- and time-dependently increased hPepT1 promoter and transport activities in Caco2-BBE cells, with maximal activity observed in cells treated with 5 mM butyrate for 24 hours. Under these conditions, we observed a 22-fold increase in reporter activity from the hPepT1 promoter; this stimulation could be blocked by actinomycin D, confirming transcriptional activation. Furthermore, we observed increased hPepT1 mRNA expression, protein expression and transport activity (measured by the uptake of *Gly-Sar) in butyrate-treated cells. Collectively, these data suggest that a bacterial product could induce or regulate hPepT1 expression. [ABSTRACT FROM AUTHOR]