L12 enhances gonococcal transcytosis of polarized Hec1B cells via the lutropin receptor

We previously reported that gonococci convert to a more invasive phenotype (Inv(+)GC) following contact with cells expressing the lutropin receptor (LHr) and that Inv(+)GC express a novel adhesin that interacts with LHr. We propose that this adhesion allows Inv(+)GC to activate LHr and induce gonococcal transcytosis, usurping normal LHr function in fallopian and endometrial epithelium, which is to transport fetal chorionic gonadotropin (hCG) into the mother. Infected polarized Hec1 B monolayers, grown on collagen-coated transwells, showed that the passage of GC across the monolayer occurred rapidly, within 30 min, and proceeded at a constant rate with Inv(+)GC passage three-fold faster than GC grown in tissue culture media alone (Inv(-)GC). Electron microscopy found that Inv(+)GC triggered pseudopod formation around the bacterium, with GC found throughout the Hec1B targets within 30 min, while Inv(-)GC did neither. Pre-treatment of Inv(-)GC with recombinant ribosomal protein L12, a gonococcal 'hCG-like' protein previously shown to increase invasion, also increased Inv(-)GC transcytosis to the rate of Inv(+)GC. This enhancement was completely abolished by addition of luteinizing hormone, a cognate ligand of LHr. This is convincing evidence that surface expressed L12 mediates gonococcal invasion and transcytosis via LHr, a mechanism that could be important in the development of invasive gonococcal disease in women. (C) 2002 Elsevier Science Ltd.