TARGET-CELL CONTACT TRIGGERS EXPRESSION AND POLARIZED TRANSFER OF YERSINIA YOPE CYTOTOXIN INTO MAMMALIAN-CELLS

Pathogenic bacteria of the species Yersinia, including Yersinia pestis , block phagocytosis by macrophages. This process involves the YopE pr otein, which induces disruption of the host cell actin microfilament s tructure. Here, we show that the contact between the pathogen and the mammalian cell induces expression and then polarized transfer of YopE into the eukaryotic cell. While the bacteria remain at the surface of the target cell, the YopE cytotoxin is transferred through the host ce ll plasma membrane and YopE is only recovered within the cytosol of th e target cell. The results suggest that the pathogen senses cell struc tures and focuses the transfer of YopE to occur solely at the interact ion zone between the bacterium and the eukaryotic cell. The regulation of this process is shown to involve surface-located YopN sensor prote in of the bacterium.