Attachment of Neisseria gonorrhoeae to the cellular pilus receptor CD46: identification of domains important for bacterial adherence

pill of Neisseria gonorrhoeae mediate binding of the bacteria to human host cells. Membrane cofactor protein (MCP or CD46), a human cell-surface prote in involved in regulation of complement activation, acts as a cellular pilu s receptor. In this work, we examined which domains of CD46 mediate bacteri al adherence. The CD46 expression was quantified and characterized in human epithelial cell lines. N. gonorrhoeae showed the highest adherence to ME18 0 cells, which have BC1 as the dominant phenotype, The Sc isoforms of CD46 were expressed in all cell lines tested. The adherence was not enhanced by high expression of other isoforms, showing that the sc domain of CD46 is im portant in adherence of N, gonorrhoeae to human cells. To characterize the pilus-binding site within the CD46 molecule, a set of CD46-BC1 deletion con structs were transfected into COS-7 cells. Piliated N. gonorrhoeae attached well to CD46-BC1-expressing COS-7 cells. We show that the complement contr ol protein repeat 3 (CCP-3) and the serine-threonine-proline (STP)-rich dom ain of CD46 are important for efficient adherence to host cells. Further, p artial deletion of the cytoplasmic tail of CD46 results in low bacterial bi nding, indicating that the cytoplasmic tail takes part in the process of es tablishing a stable interaction between N. gonorrhoeae and host cells.