In vitro binding of type 1-fimbriated Escherichia coli to uroplakins Ia and Ib: relation to urinary tract infections.

Urinary tract infections, caused mainly by Escherichia coli, are among the most common infectious diseases. Most isolates of the uropathogenic E.coli can express type 1 and P fimbriae containing adhesins that recognize cell receptors. While P fimbriae recognize kidney glycolipid receptors and are involved in peyelonephritis, the urothelial for type 1 fimbriae were not identified. We show that type 1-fimbriated E. coli recognize uroplakins Ia and Ib, two major glycoproteins of urothelial apical plaques. Anchorage of E. coli to urothelial surface via type 1 fimbriae-uroplakin I interactions may play a role in its bladder colonization and eventual ascent through the ureters, against urine flow, to invade the kidneys.

Close association of the alpha subunits of Gq and G11 G proteins with actin filaments in WRK1 cells: relation to G protein-mediated phospholipase C activation.

A selective polyclonal antibody directed toward the C-terminal decapeptide common to the alpha subunits of Gq and G11 G proteins (G alpha q/G alpha 11) was prepared and used to investigate the subcellular distribution fo these proteins in WRK1 cells, a rat mammary tumor cell line. In immunoblots, the antibody recognized purified G alpha q and G alpha 11 proteins and labeled only two bands corresponding to these alpha subunits. Functional studies indicated that this antibody inhibited vasopressin- and guanosine 5'-[alpha-thio]triphosphate-sensitive phospholipase C activities. Immunofluorescence experiments done with this antibody revealed a filamentous labeling corresponding to intracytoplasmic and perimembranous actin-like filament structures. Colocalization of G alpha q/G alpha 11 and F-actin filaments (F-actin) was demonstrated by double-labeling experiments with anti-G alpha q/G alpha 11 and anti-actin antibodies. Immunoblot analysis of membrane, cytoskeletal, and F-actin-rich fractions confirmed the close association of G alpha q/G alpha 11 with actin. Large amounts of G alpha q/G alpha 11 were recovered in the desmin- and tubulin-free F-actin-rich fraction obtained by a double depolymerization-repolymerization cycle. Disorganization of F-actin filaments with cytochalasin D preserved G alpha q/G alpha 11 and F-actin colocalization but partially inhibited vasopressin- and fluoroaluminate-sensitive phospholipase C activity, suggesting that actin-associated G alpha q/G alpha 11 proteins play a role in signal transduction.