Role of Lipooligosaccharide in Opa-Independent Invasion of Neisseria gonorrhoeae into Human Epithelial Cells

Abstract

Lipooligosaccharide (LOS) has been implicated in the adhesion and invasion of host epithelial cells. We examined the adhesive and invasive abilities of isogenic gonococcal opacity-associated outer membrane protein–negative, pilus-positive (Opa−Pil+) Neisseria gonorrhoeae strains expressing genetically defined LOS. Strain F62 (Opa−Pil+), expressing the lacto-N-neotetraose and the galNac-lacto-N-neotetraose LOS, and its isogenic derivative that expressed only the lacto-N-neotetraose LOS (F62ΔlgtD), adhered to, and invaded, to the same extent the human cervical epidermoid carcinoma cell line, ME180. While the adhesive abilities of Opa−Pil+ isogenic strains that express LOS molecules lacking the lacto-N-neotetraose structure were similar to that seen for F62, their invasive abilities were much lower than the strains expressing lacto-N-neotetraose. Fluorescence microscopy studies showed that the adherence of F62, but not the strains lacking lacto-N-neotetraose, induced the rearrangement of actin filaments under the adherent sites. Electron microscopy studies demonstrated that F62, but not the strains lacking lacto-N-neotetraose, formed extensive and intimate associations with epithelial cell membranes. Thus, in the absence of detectable Opa protein, the lacto-N-neotetraose LOS promotes gonococcal invasion into ME180 cells. The data also suggest that LOS is involved in the mobilization of actin filaments in host cells, and in the formation of a direct interaction between the bacterial outer membrane and the plasma membrane of ME180 cells.

Invasion of endothelial cells by Neisseria meningitidis requires cortactin recruitment by a phosphoinositide-3-kinase/Rac1 signalling pathway triggered by the lipo-oligosaccharide

“…The formation of the actin-rich cell projections promoting efficient internalization of N. meningitidis therefore results from two converging co-stimulatory signalling pathways, triggered by pili and LOS, most likely via interactions with distinct receptors on the surface of endothelial cells. Interestingly, it appears that, in line with our observations on N. meningitidis, the Opa-independent internalization process of piliated strains of the related pathogen N. gonorrhoeae into epithelial cells also involves both pili and LOS interactions with specific cell-surface receptors (Song et al, 2000). Although the signalling events have not been fully identified, the elongation of epithelial microvilli induced by N. gonorrhoeae required the interaction of the lacto-N-neotetraose moiety of LOS with the cell-surface asialoglycoprotein receptor (ASGP-R) (Harvey et al, 2001;Harvey et al, 2002).…”

Analysis of Lipooligosaccharide Biosynthesis in the Neisseriaceae

“…It is an outer membrane glycolipid involved in immune system evasion, attachment to epithelial tissue, host cell invasion, mediation of toxic damage in the fallopian tube, and stimulation of the production of bactericidal antibodies (2,15,20,41,44,45). Biosynthesis of gonococcal and meningococcal LOS occurs via the same biosynthetic pathway producing a branched oligosaccharide attached to lipid A via two 3-deoxy-D-manno-2-octulosonic acid (KDO) molecules (12,13,21,22,48).…”

“…Variation in the number of LOS components expressed and their relative concentrations and in the sugar compositions of the individual LOS molecules is observed (10,12,13,21,26,27,33,47). The number of branches and the length of each oligosaccharide in the branch vary, and this variation is important in determining the pathogenic potential of the expressing strain (41,47). Additionally, gonococci and meningococci can modify their LOS by adding a sialic acid residue onto a terminal galactose that is found in the lacto-N-neotetraose structure (32).…”

“…are rarely associated with disease, some strains occasionally cause clinical illnesses (e.g., endocarditis caused by N. sicca (11) and arthritis caused by N. subflava (1). We have recently shown that the expression of the lacto-N-neotetraose LOS is able to promote gonococcal invasion into tissue culture cells (41), indicating that the expression of the lacto-N-neotetraose glycoform is important for the establishment of invasive infections. Since most commensal Neisseria spp.…”

Cholera toxin and extracellular Ca2+ induce adherence of non-piliated Neisseria: evidence for an important role of G-proteins and Rho in the bacteria-cell interaction

“…For example, the porin PorB1a of N. gonorrhoeae promotes bacterial invasion (van Putten et al, 1998), and variation of the lipoligosaccharide (LOS) modulates bacterial invasion (Song et al 2000). Also, it has been shown that N. gonorrhoeae produces a 36 kDa outer membrane protein with a binding specificity to gangliotetraosylceramide.…”