Interactions of Campylobacter jejuni Cytolethal Distending Toxin Subunits CdtA and CdtC with HeLa Cells

Abstract

Campylobacter jejuni produces a toxin, called cytolethal distending toxin (CDT), which causes direct DNA damage leading to invocation of DNA damage checkpoint pathways. The affected cells arrest in G 1 or G 2 and eventually die. CDT consists of three protein subunits, CdtA, CdtB, and CdtC, with CdtB recently identified as a nuclease. However, little is known about the functions of CdtA or CdtC. In this work, enzyme-linked immunosorbent assay-based experiments were used to show, for the first time, that both CdtA and CdtC bound with specificity to the surface of HeLa cells, whereas CdtB did not. Varying the order of the addition of subunits for reconstitution of the holotoxin had no effect on activity. In addition, mutants containing deletions of conserved regions of CdtA and CdtC were able to bind to the surface of HeLa cells but were not able to participate in holotoxin assembly. Finally, both Cdt mutant subunits were able to effectively compete with CDT holotoxin in the HeLa cell binding assay.

Carbohydrate-Binding Specificity of the Escherichia coli Cytolethal Distending Toxin CdtA-II and CdtC-II Subunits

“…The normal route for triggering the cytolethal activity of CDT requires the presence of all three CDT subunits. Recent reports indicate that CdtA and CdtC are the binding subunits of the CDT holotoxin (5,14,16). These data are supported by structural analysis of the CDT Hd holotoxin, indicating that CdtA Hd and CdtC Hd possess structural folds that resemble those of the ricin B chain (17).…”

“…Unlike the CdtAC heterodimer, individual CdtA Hd and CdtC Hd subunits failed to block the action of holotoxin, suggesting that the CdtAC heterodimer is the functional cell surface-binding component of CDT (5). Recently, Lee et al demonstrated that CdtA and CdtC of C. jejuni (CdtA Cj and CdtC Cj , respectively) bound independently to HeLa cells and exhibited competitive binding for one another, suggesting that these subunits bind to the same cell surface structure (14).…”

Cytolethal Distending Toxin Family Members Are Differentially Affected by Alterations in Host Glycans and Membrane Cholesterol

“…Consistent with their proposed roles as binding subunits, CdtA and/or CdtC increase the ability of CdtB to associate with host cells and greatly enhance intoxication (7,(17)(18)(19)(20)(21)(22)(23)(24)(25). The identification of ricin-like lectin domains in CdtA and CdtC from structural and biochemical data first suggested that these subunits may interact with carbohydrates on the cell surface (13,26,27).…”

“…It is not currently known which activity is of greater importance, and this may depend on the specific toxin and/or the host target cell type (12,14). CdtB enzymatic activity induces cell cycle arrest predominantly at the G 2 /M transition, resulting in cellular distension and ultimately cell death (5,15,16).Consistent with their proposed roles as binding subunits, CdtA and/or CdtC increase the ability of CdtB to associate with host cells and greatly enhance intoxication (7,(17)(18)(19)(20)(21)(22)(23)(24)(25). The identification of ricin-like lectin domains in CdtA and CdtC from structural and biochemical data first suggested that these subunits may interact with carbohydrates on the cell surface (13,26,27).…”

Cloning and protein expression of Aggregatibacter actinomycetemcomitans cytolethal distending toxin C

“…Very limited data are available about the function of CdtA and especially of CdtC. Many studies find that both CdtA and CdtC are capable of binding to the cellular membrane and some suggested that they might share the same receptor [15][16][17][18] . Reports indicating that antibodies raised against CdtC were protective against CDT toxicity corroborated these findings.…”