Fig. 6. Surface expression of CD147 modifies invasion of L. monocytogenes into epithelial cells. (A) HEK293 cells were transiently transfected with pcDNA4-Xpress-NOD2 and/or pEGFP-N1-CD147 and infected with L. monocytogenes for 1 hour. After killing of extracellular bacteria by gentamicin, cells were lysed and plated on solid medium. CFU of Listeria were expressed as relative invasion adjusted to the cell number (measured in parallel by MTT test). Transient overexpression of NOD2 led to a protection of HEK293 against infection, whereas this effect was abolished by parallel overexpression of CD147. CD147 overexpression alone enhanced the relative infection rate of Listeria. (B) HEK^NOD2 cells stably transfected with siRNA constructs targeting CD147 were used for gentamicin protection assays as described. Gene-silencing of CD147 strongly reduced the infection by Listeria monocytogenes. Antibodies directed against the extracellular part of CD147 inhibited invasion [relative invasion as a percentage of control; mean ± s.d. (n=3); ^*P<0.05, ^**P<0.01 for experiment versus control].