Bacterial Outer Membrane Protein OmpX Regulates β1 Integrin and Epidermal Growth Factor Receptor (EGFR) Involved in Invasion of M-HeLa Cells by Serratia proteamaculans

Opportunistic pathogen Serratia proteamaculans are able to penetrate the eukaryotic cells. The penetration rate can be regulated by bacterial surface protein OmpX. OmpX family proteins are able to bind to host cell surface to the epidermal growth factor receptor (EGFR) and the extracellular matrix protein fibronectin, whose receptors are in return the α5 β1 integrins. Here we elucidated the involvement of these host cell proteins in S. proteamaculans invasion. We have shown that, despite the absence of fibronectin contribution to S. proteamaculans invasion, β1 integrin was directly involved in invasion of M-HeLa cells. Herewith β1 integrin was not the only receptor that determines sensitivity of host cells to bacterial invasion. Signal transfer from EGFR was also involved in the penetration of these bacteria into M-HeLa cells. However, M-HeLa cells have not been characterized by large number of these receptors. It turned out that S. proteamaculans attachment to the host cell surface resulted in an increment of EGFR and β1 integrin genes expression. Such gene expression increment also caused Escherichia coli attachment, transformed with a plasmid encoding OmpX from S. proteamaculans. Thus, an OmpX binding to the host cell surface caused an increase in the EGFR and β1 integrin expression involved in S. proteamaculans invasion.