Characterization of High Molecular Weight Mucins of Rabbit Bladder

摘要

Epithelial mucin glycoproteins of bladder act as an effective barrier against invasion by pathogenic microorganismsand injury by toxic substances in urine. Although these glycoconjugates play important roles in the pathophysiologyof bladder disorders such as intestinal cystisis, cancer, and urinary tract infections, they have not been characterized indetail either in humans or in animals. Rabbits could be useful for developing models for studying bladder disorders. In thisstudy, we purified and partially characterized two major high molecular weight rabbit bladder mucin glycoproteins, designatedRBM1 and RBM2, found in urine. Consistent with their mucin characteristics, amino acid compositions showedhave high levels of serine, glutamic acid, proline, glycine and alanine, which together comprise 34% and 42% of the totalamino acids in RBM1 and RBM2, respectively. Carbohydrate compositional analysis indicated that RBM1 and RBM2 consistof N-acetylgalactosamine (GalNAc), N-acetylglucosamine (GlcNAc), galactose (Gal), N-acetylneuraminic acid(NeuAc) and fucose (Fuc) in the molar ratio of 1.0: 0.82: 0.12: 0.30: 0.02 and 1.0: 1.03: 0.46: 0.16: 0.05, respectively;mannose (Man) was not detected in either mucin. Both mucin fractions were strongly reactive to wheat germ agglutinin,but not to Ca2 antibody specific to a human tumor mucin antigen (asialylated carbohydrate linked to protein core), suggestingthat most of the galactosyl residues of oligosaccharides are sialylated. Together, the data suggest that rabbit mucinglycoproteins characterized here are distinctively different from MUC1 mucin glycoprotein found in human urine