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MUCOSAL BIOLOGY
1Gastrointestinal Research Laboratory, Veterans' Affairs Medical Center, San Francisco, California; 2Department of Medicine, University of California San Francisco, California; and 3Second Department of Internal Medicine, National Defense Medical College, Saitama, Japan
Submitted 28 March 2005 ; accepted in final form 14 June 2005
VIP exerts a spectrum of effects as a potent anti-inflammatory factor. In addition, VIP increases expression of MUC2, a major intestinal secretory mucin. We therefore investigated the effects of VIP on the promoter activity of the 5'-flanking region of the MUC2 gene. VIP activated MUC2 transcription in human colonic epithelial cells via cAMP signaling to ERK and p38. cAMP/Epac/Rap1/B-Raf signaling was not involved in MUC2 reporter activation. Furthermore, activation of MUC2 transcription was independent of many of the reported downstream effectors of G protein-coupled receptors, such as PKC, Ras, Raf, Src, calcium, and phosphoinositide 3-kinase. VIP induced cAMP response element-binding protein (CREB)/ATF1 phosphorylation, and this was prevented by treatment with inhibitors of either MEK or p38 and by PKA and MSK1 inhibitor H89. CREB/ATF1 and c-Jun were shown to bind to an oligonucleotide encompassing a distal, conserved CREB/AP1 site in the 5'-flanking region of the MUC2 gene, and this cis element was shown to mediate promoter reporter activation by VIP. This study has identified a new, functional cis element within the MUC2 promoter and also a new pathway regulating MUC2 expression, thus providing further insight into the molecular mechanism of VIP action in the colon. These findings are relevant to the normal biology of the colonic mucosa as well as to the development of VIP as a therapeutic agent for treatment of inflammatory bowel disease.
signaling; G protein-coupled receptor; inflammatory bowel disease; protein kinase A
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