Receptor-mediated endocytosis of Neisseria gonorrhoeae into primary human urethral epithelial cells: the role of the asialoglycoprotein receptor

Urethral epithelial cells are invaded by Neisseria gonorrhoeae during gonoc occal infection in men. To understand further the mechanisms of gonococcal entry into host cells, we used the primary human urethral epithelial cells (PHUECs) tissue culture system recently developed by our laboratory. These studies showed that human asialoglycoprotein receptor (ASGP-R) and the term inal lactosamine of lacto-N-neotetraose-expressing gonococcal lipooligosacc haride (LOS) play an important role in invasion of PHUECs. Microscopy studi es showed that ASGP-R traffics to the cell surface after gonococcal challen ge. Co-localization of ASGP-R with gonococci was observed. As ASGP-R-mediat ed endocytosis is clathrin dependent, clathrin localization in PHUECs was e xamined after infection. Infected PHUECs showed increased clathrin recruitm ent and co-localization of clathrin and gonococci. Preincubating PHUECs in 0.3 M sucrose or monodansylcadaverine (MDC), which both inhibit clathrin-co ated pit formation, resulted in decreased invasion. N. gonorrhoeae strain 1 291 produces a single LOS glycoform that terminates with Gal(beta1-4)Glc-Na c(beta1-3)Gal(beta1-4)Glc (lacto-N-neotetraose). Invasion assays showed tha t strain 1291 invades significantly more than four isogenic mutants express ing truncated LOS. Sialylation of strain 1291 LOS inhibited invasion signif icantly. Preincubation of PHUECs in asialofetuin (ASF), an ASGP-R ligand, s ignificantly reduced invasion. A dose-response reduction in invasion was ob served in PHUECs preincubated with increasing concentrations of NaOH-deacyl ated 1291 LOS. These studies indicated that an interaction between lacto-N- neotetraose-terminal LOS and ASGP-R allows gonococcal entry into PHUECs.