The studies outlined in this application will explore the structure and function of colonic glycoproteins in an effort to understand their role in inflammatory bowel disease. Past studies in this laboratory have demonstrated the presence of several structurally distinct mucin glycoproteins in the human colon, designated mucin species I-VI (HCM I-IV) which appear to arise from functionally distinct subpopulations of goblet cells. The biological importance of the glycoprotein species is supported by the demonstration of selective deficiency in one species (IV) in specific association with ulcerative colitis. The molecular and cellular basis of colonic mucin glycoprotein heterogeneity will be defined using human colonic tissue and a colon carcinoma derived cell line (HT-29, N2) which differentiates into a goblet cell population in vitro. The genes encoding the peptide backbones of the individual mucin species will be cloned utilizing nucleotide sequences derived from peptide digests and anti-HCM antibodies. These studies should provide insight into the fundamental peptide and macromolecular structure of the mucin class of glycoproteins generally. In addition regulation of biosynthesis and secretion of colonic glycoproteins will be examined and physiologic secretagogues identified through the use of in vitro organ culture and cell culture techniques. The basis of the observed defect of HCM species IV in ulcerative colitis will be delineated. Expression of HCM peptide genes in UC and control tissues will be assessed and effects of therapeutic agents on the expression of HCM species will also be examined. Additional studies will be undertaken to characterize glycoconjugate structural determinants recognized by newly developed monoclonal antibodies which specifically bind to UC mucosa. Thus, a comprehensive study of colonic glycoproteins is proposed to enhance our understanding of their structure, function and contribution to inflammatory bowel disease.
