Abstract FR:

The Cytotoxic Necrotizing Factor 1 (CNF1) produced by uropathogenic Escherichia coli allows us to highlight that Smurf1 is the only ubiquitin-ligase involved in the CNF1-induced RhoA GTPase ubiquitylation, implying that Smurf1 ubiquitylates the activated forms of RhoA. Moreover, we showed that unlike primary cells, some cancerous cells lines lost the capacity of ubiquitylation of one or more Rho GTPases, indicating that there are, at least, three specific systems of ubiquitylation for RhoA, Rac1 and Cdc42. The study of the interaction between the Rac1 GTPase and Cullin-1, a protein of the SCF complex of ubiquitylation, enabled us to show that Rac1 activation by CNF1 induces IkBa ubiquitinylation and its degradation, leading to the activation of the Nf-kB pathway. This Rac1 activation leads to the recruitment of the phosphorylated forms of IkBa proteins in the membranes ruffles, as well as proteins Skp1 and Cullin-1, two proteins of the SCF complex responsible for the IkBa ubiquitylation. We observed that the bacterial factor EDIN (Epidermal Cell Differentiation Inhibitor) of Staphylococcus aureus produced trans-cellular perforation of endothelial cells, that we named macro-apertures. EDIN has an enzymatic activity which allows the inactivation of RhoA by the addition of ADP-ribose. We showed that the inhibition of RhoA and the destruction of the actin cables are responsible for the induction of the macro-apertures. This property of induction of macro-apertures could thus confer EDIN with the characteristics of an invasion factor.