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  • Title: Cortactin is essential for F-actin assembly in enteropathogenic Escherichia coli (EPEC)- and enterohaemorrhagic E. coli (EHEC)-induced pedestals and the alpha-helical region is involved in the localization of cortactin to bacterial attachment sites.
    Author: Cantarelli VV, Kodama T, Nijstad N, Abolghait SK, Iida T, Honda T.
    Journal: Cell Microbiol; 2006 May; 8(5):769-80. PubMed ID: 16611226.
    Abstract:
    Enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC) are important human pathogens. Upon attachment to host cells, EPEC and EHEC are able to induce actin polymerization, which accumulates, forming a pedestal-like structure beneath the attached bacteria. Using siRNA, we show here that EPEC- and EHEC-induced pedestals are dependent on cortactin, an F-actin-binding protein found in the mammalian cell cortex. Knock-down of cortactin by siRNA resulted in a dramatic reduction of the pedestal formation induced by both pathogens. We also show that disruption of the Src homology 3 (SH3) domain of cortactin, or its downregulation by specific point mutations, negatively affects pedestal formation, suggesting that this domain is important for regulation of F-actin assembly by EPEC and EHEC. Green fluorescent protein (GFP) fused with the SH3 domain (GFP-SH3), proline-rich region (GFP-PRR) or alpha-helical region of cortactin markedly reduced the amount of F-actin at the bacterial attachment sites. Interestingly, neither GFP-SH3 nor GFP-PRR was recruited to the vicinity of the bacterial adherence sites; however, GFP fused to the alpha-helical region was efficiently recruited and colocalized with the attached bacteria. These results demonstrate that cortactin is a requirement for pedestal formation and suggest a novel function for the predicted alpha-helical region of cortactin in actin assembly induced by EPEC and EHEC.
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