Cell-to-Cell Propagation of the Bacterial Toxin CNF1 via Extracellular Vesicles: Potential Impact on the Therapeutic Use of the Toxin

Abstract

Eukaryotic cells secrete extracellular vesicles (EVs), either constitutively or in a regulated manner, which represent an important mode of intercellular communication. EVs serve as vehicles for transfer between cells of membrane and cytosolic proteins, lipids and RNA. Furthermore, certain bacterial protein toxins, or possibly their derived messages, can be transferred cell to cell via EVs. We have herein demonstrated that eukaryotic EVs represent an additional route of cell-to-cell propagation for the Escherichia coli protein toxin cytotoxic necrotizing factor 1 (CNF1). Our results prove that EVs from CNF1 pre-infected epithelial cells can induce cytoskeleton changes, Rac1 and NF-κB activation comparable to that triggered by CNF1. The observation that the toxin is detectable inside EVs derived from CNF1-intoxicated cells strongly supports the hypothesis that extracellular vesicles can offer to the toxin a novel route to travel from cell to cell. Since anthrax and tetanus toxins have also been reported to engage in the same process, we can hypothesize that EVs represent a common mechanism exploited by bacterial toxins to enhance their pathogenicity.

Microbial carcinogenic toxins and dietary anti-cancer protectants

“…CNF1 is one of the bacterial toxins whose carcinogenic properties are not confined to the GI tract. The toxin can be trafficked between cells via extracellular vesicles which are similar to, if not identical with, normal exosomes [ 56 ]. The toxin can therefore pass through the GI wall into other tissues, potentially transmitting its oncogenic activity to distant regions of the body.…”

Extracellular Vesicle-Induced Differentiation of Neural Stem Progenitor Cells

“…Proof that NSPCs-derived EVs play a role in intercellular communication requires that these vesicles are taken up by NSPCs and that this event can modify the biology of target cells. It has been demonstrated that exosomes are uptaken in a selective way by neighboring cells and that their uptake can lead to the activation of cell proliferation and differentiation [10,18,27].…”

Effects of the Escherichia coli Bacterial Toxin Cytotoxic Necrotizing Factor 1 on Different Human and Animal Cells: A Systematic Review

“…Overall, the specific activity of CNF1 is to permanently activate Rho, Rac, and Cdc42 GTPases in all the cell systems where its effects have been studied [2,4,5,7,[8][9][10][25][26][27][32][33][34][35][36][37][38][39][41][42][43]47,52,[55][56][57][58][59][60][61][62][63][64]68,69,75,[77][78][79][80][81]84,[89][90][91][92]. However, the timing and level of activation of the distinct members of the Rho GTPase family may turn out to be variable between different cell types and lines.…”

“…Multinucleation after treatment with CNF1 is reported for 19 cell lines (HEp-2 [27,49,50,53,57,96]; HeLa [33,34,36]; Caco-2 [39]; HT-29 [22]; T24 [26,27]; 5637 [26,27]; Y-1 [27]; A-498 [27]; J82 [27]; SV-HUC-1 [27]; ACHN [27]; human GMB [32]; GL261 [32]; JURKAT [44]; PAE [78]; NIH 3T3 [6,37]; 3T3-Swiss Albino [53]; 3T3-L1 [75]; HCT-116 [45]) (Figure 2A). These morphological changes are probably a consequence of CNF1-induced mitosis/cytokinesis failure [1,49,97].…”

“…In three cell lines, after prolonged treatment, the block of proliferation resulted in cell death (5637 [27]; 3T3-L1 [75]; GL261 [32]), which in one case occurred by an apoptotic mechanism (5637 [27]). In other cell lines, CNF1 treatment seems to protect cells from apoptosis induced by exposure to UV [57,96] or in simulated microgravity conditions [64,65]. Although the molecular mechanisms are still unknown, it seems reasonable, that the fate (senescence, cell death, or survival) of CNF1-treated cells largely depends on the cell type and on the transformation degree of the cells exposed.…”