Terminal glycosylation of bovine uroplakin III, one of the major integral-membrane glycoproteins of mammalian bladder

Uroplakin III (UPIII) is one of the major transmembrane glycoproteins expos ed at the luminal face of mammalian bladder. We investigated the terminal g lycosylation of bovine UPIII in order to ascertain whether it contains the alpha 2,3-sialylated sequence thus potentially serving as a receptor for ur opathogenic Escherichia coli expressing type S adhesins. We report the occu rrence of sialic acid in alpha 2,3- and alpha 2,6-linkage to galactose in b ovine UPIII glycans as evidenced by the sensitivity of UPIII to both Vibrio cholera and Newcastle disease virus neuraminidase and by the colocalizatio n of UPIII antigen and material detected by lectins of Sambucus nigra and M aackia amurensis on the luminal face of the bladder. We also present eviden ce that UPIII glycans are capped by Gal-alpha 1,3-Gal epitope. Consistently , alpha 2,3- and alpha 2,6-sialyltransferase, as well as alpha 1,3-galactos yltransferase were found to be present in the cells detached from the lumin al side of bovine bladder, which are responsible for the UPIII biosynthesis . The putative role of UPIII sialylated glycans in enhancing the uropathoge nicity of E. coli expressing type S adhesins is discussed. (C) 2000 Elsevie r Science B.V. All rights reserved.