Cholera Toxin Disrupts Barrier Function by Inhibiting Exocyst-Mediated Trafficking of Host Proteins to Intestinal Cell Junctions

Abstract

Summary Cholera toxin (CT), a virulence factor elaborated by Vibrio cholerae, is sufficient to induce the severe diarrhea characteristic of cholera. The enzymatic moiety of CT (CtxA) increases cAMP synthesis in intestinal epithelial cells, leading to chloride ion (Cl−) efflux through the CFTR Cl− channel. To preserve electroneutrality and osmotic balance, sodium ions and water also flow into the intestinal lumen via a paracellular route. We find that CtxA-driven cAMP increase also inhibits Rab11/exocyst-mediated trafficking of host proteins including E-cadherin and Notch signaling components to cell-cell junctions in Drosophila, human intestinal epithelial cells, and ligated mouse ileal loops, thereby disrupting barrier function. Additionally, CtxA induces junctional damage, weight loss, and dye leakage in the Drosophila gut, contributing to lethality from live V. cholerae infection, all of which can be rescued by Rab11 over-expression. These barrier-disrupting effects of CtxA may act in parallel with Cl− secretion to drive the pathophysiology of cholera.

CpG Oligodeoxynucleotides Facilitate Delivery of Whole Inactivated H9N2 Influenza Virus via Transepithelial Dendrites of Dendritic Cells in Nasal Mucosa

“…Interestingly, in this system, it was difficult to find any viruses within the DCs or the ECs, and furthermore, the indexes of paracellular transport, including TEER and tight junctions, were not altered, indicating that submucosal DCs but not ECs played a dominant role in viral transport in the coculture system. Consistent with a recent report (48), the typical mucosal adjuvant CT, in contrast to CpGs, strongly disrupted the EC barrier function, implying another adjuvant mechanism whereby CT can facilitate antigen transport via the epithelial paracellular pathway.…”

Micropatterned Macrophage Analysis Reveals Global Cytoskeleton Constraints Induced by Bacillus anthracis Edema Toxin

“…EF acts on RAB11 through the increase of cAMP and protein kinase A (PKA) and EPAC-RAP-1 activation. It is also interesting that the cholera toxin ADP-ribosylates the stimulatory G protein (G s␣ ), which causes a pathological intracellular increase of cAMP, and RAB11 disruption through PKA and EPAC-RAP-1 (42). How cAMP increase affects RAB11 regulation is still unknown, but this may explain some effects observed on the cytoskeleton organization (43).…”

Cholera Toxin Notches Epithelial Junctions

“…In this issue, Guichard et al (2013) report that CT compromises intestinal epithelium barrier function via cyclic AMP (cAMP)-induced disruption of Rab11-and exocyst-dependent delivery of endocytic recycling cargo to cell-cell junctions.…”

“…As with other enteropathogens triggering watery diarrhea, the mechanism by which water flows across and out of the epithelium is not fully understood. Now, Guichard et al (2013) reveal that dysfunction of Rab11 and exocyst machinery, which is triggered by CT via forced induction of cyclic AMP (cAMP) signaling, compromises epithelium barrier integrity and contributes to efflux of water and solutes associated with V. cholera infection.…”