HOME
Return to Table of Contents
REGULATION AND POTENTIAL MECHANISMS OF SMALL PROLINE RICH PROTEIN-2 EXPRESSION IN DIFFERENTIATED SMALL INTESTINAL EPITHELIUM
Patrick J Hui, Brandon Ritcey, MJ Ropeleski
Gastrointestinal Diseases Research Unit (GIDRU), Queen’s University, Kingston, Ontario
Small proline-rich protein-2 (SPRR2) may mediate commensal flora trophism during epithelial differentiation of the small intestine and is up-regulated during adaptation and in allergic inflammation. Using the Caco-2 model of differentiation along the crypt-villus axis, we have shown that SPRR2 is preferentially expressed in post-confluent differentiated Caco-2 cells and in undifferentiated cells in response to short chain fatty acids (SCFAs). We aimed to delineate mechanisms by which SPRR2 is regulated during differentiation and how it responds to the physiologically relevant factors IL-11, EGF, IL-13 and S. typhimurium.
SPRR2 expression was examined in Caco-2 and T84 cell lines. SPRR2 protein expression was detected by immunoblotting and immunofluorescence in the presence of SB203580 or 8-Br-cAMP, as were the time and dose-dependent effects of SCFAs and specific histone deacetylase (HDAC) inhibitors. SPRR2 responses to cytokines, growth factors, and S. typhimurium grown under microaerophilic conditions were similarly examined.
SPRR2 expression increased at four days post confluence with a maximal increase at ten days. Differentiation induced SPRR2 was down-regulated by 8-Br-cAMP but not by the p38 MAPK inhibitor SB203580. Surprisingly, no induction was seen with specific HDAC inhibitors TSA or SBHA. IL-11, EGF and IL-13 failed to induce SPRR2 while S. typhimurium induced SPRR2 at the six hour timepoint in Caco-2 cells.
We conclude that SPRR2 expression is associated with differentiated epithelia and is down-regulated by PKA activators and up-regulated by by-products of the bowel flora which does not involve the inhibition of histone deacetylases. SPRR2 induction by S. typhimurium ascribes to it a putative role in host/pathogen interactions. Whether the SPRR2 response is specific to S. typhimurium or reflects a generalized response to bacteria or their constituents such as LPS is the subject of ongoing studies.
Supported by Crohn’s and Colitis Foundation of Canada