Cultured mammalian cells attach to the invasin protein of Yersinia pseudotuberculosis.

The expression of invasin, the product of the Yersinia pseudotuberculosis inv gene, allows enteric bacteria to enter cultured mammalian cells. The ability of invasin to bind animal cells and the potential significance of this interaction in the entry process were investigated. It was found that HEp-2 cells could attach to surfaces coated with bacterial membranes containing invasin. By fractionating bacterial membrane proteins on NaDodSO4/polyacrylamide gels and transferring the protein to filters, we demonstrated that the cell-binding component of the membranes comigrated with invasin. Mutations that changed the electrophoretic mobility of the protein also caused a corresponding shift in the migration of the cell-binding activity, showing that the comigrating protein was indeed invasin. Monoclonal antibodies directed against invasin that blocked invasin-HEp-2 cell interaction also inhibited bacteria from penetrating HEp-2 cells, indicating that interaction of this protein with animal cells is critical for cellular penetration.