Description and functional evaluation of a new TccP (Tir-cytoskeleton coupling protein) subtype in formation of attaching and effacing lesion, independently of Nck, in an Escherichia albertii isolate

Abstract

The species Escherichia albertii comprises the newest member of the genus Escherichia and is associated with sporadic cases, as well as outbreaks of diarrhea in several countries, including Brazil. One of the main characteristics of virulence observed in E. albertii isolates is the formation of the attaching and effacing lesion (AE), which is characterized by intimate bacteria adherence to the epithelial cells, destruction of microvilli and formation of a pedestal-like structure rich in F-actin and other elements of the eukaryotic cytoskeleton. Studies conducted with enteropathogenic (EPEC) and enterohemorrhagic (EHEC) E. coli have demonstrated that the formation of the AE lesion can occur in two distinct pathways, one dependent and the other independent of the non-catalytic region of the eukaryotic protein tyrosine kinase (Nck). Previous studies carried out with the Brazilian prototype of E. albertii 1551-2 showed that this pathogen is able to promote the recruitment of F-actin, for the formation of the AE lesion, using both the Nck-dependent and the Nck-independent pathways. In EHEC it is known that the Nck-independent pathway utilizes the Tir-cytoskeleton coupling protein (TccP) adapter protein in the F-actin recruitment cascade. Genome analysis of E. albertii revealed the presence of two genes responsible for encoding two new variants of the TccP adapter protein, which genes were called tccP3 and tccP4. A study recently published by our laboratories showed that the TccP3 protein plays a minor role in the establishment of the AE lesion, while the role of TccP4 remains unknown. Therefore, the main objective of this research project is to evaluate the production of TccP4 by the E. albertii 1551-2 isolate, the co-localization of this protein with the F-actin accumulation, as well as to establish whether TccP4 is necessary for the formation of the AE lesion in cells infected by this pathogen.