Abstract Number: PB1817
Meeting: ISTH 2020 Congress
Background: Besides their roles in hemostasis and as components of the circulating immune system, platelets also constitute a potential target for bacteria that enter the bloodstream. Bacteria produce diverse toxins capable of modulating platelet function. The cytotoxic necrotizing factor 1 (CNF1) is the major virulence factor of extraintestinal pathogenic E. coli (ExPEC), which is the leading cause of bacteremia world-wide and a frequent cause of sepsis. CNF1 is internalized upon binding to specific plasma membrane receptors and processed to release the enzymatic domain into the cytoplasm. This domain catalyzes deamidation of a specific glutamine residue of Rho GTPases rendering them constitutively active and causing profound morpho-functional alterations in the target cell.
Aims: While the molecular and functional effects of CNF1 have been studied to some extent in epithelial cells, fibroblasts and leukocytes, no studies have addressed the impact of this toxin on platelet function.
Methods: We used platelets isolated from volunteer donors. Platelets were incubated with CNF1 at 37°C for up to 4 hours. Secretion and integrin activation were assayed by flow cytometry. Spreading was assayed by immunocytochemistry.
Results: Platelets express both laminin receptors, p37/67 and Lu/BCAM, involved in binding of CNF1. CNF1 becomes internalized in platelets and causes a shift in the electrophoretic mobility of RhoA, indicating that it becomes deamidated. CNF1 causes an increase in the levels of basal F-actin and impairs secretion of alpha and dense granules as well as integrin αIIbβ3 activation. The toxin does not impair adhesion to collagen or fibrinogen, however one third of the platelets adopt a strikingly spiky morphology. We are investigating the molecular mechanisms underlying these alterations and how they relate to Rho GTPase function.
Conclusions: By affecting platelet function CNF1 may contribute to the pathogenesis of sepsis by E. coli.
To cite this abstract in AMA style:Chacko A, Riley D, Wei J, Colarusso A, Tutino ML, Rivero F. Effects of the Bacterial Toxin Cytotoxic Necrotising Factor 1 on Platelet Function [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/effects-of-the-bacterial-toxin-cytotoxic-necrotising-factor-1-on-platelet-function/. Accessed January 27, 2022.
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