Annotated Bibliography

Banerjee, R., Das, B., Balakrish Nair, G. & Basak, S. Dynamics in genome evolution of Vibrio cholerae. Infect. Genet. Evol. 23, 32–41 (2014).

  • This review summarizes recent findings regarding the genetics and evolutionary relationships between toxigenic Vibrio cholerae strains. Among recent findings is the identification of genetic elements that serve as a marker of differentiation among viral clones.

Bernardi, K. M. et al. The E3 Ubiquitin Ligases Hrd1 and gp78 Bind to and Promote Cholera Toxin Retro-Translocation. Mol. Biol. Cell 21, 140–151 (2010).

  •  Proteins that have been identified to be active in the retro-translocation of the catalytic CTA1 subunit include the Derlins and ER-associated multi-spanning E3 ubiquitin ligases, Hrd1 and gp78. In this study, mutation and knock-out experiments of Hrd1 and gp78 yielded decreased translocation, thus indicating that ubiquitination is involved in the transport process.

Cholera vaccines: WHO position paper. Relevé Épidémiologique Hebd. Sect. Hygiène Secrétariat Société Nations Wkly. Epidemiol. Rec. Health Sect. Secr. Leag. Nations 85, 117–128 (2010).

  • The document of a interest is a position paper that states the state of cholera vaccines in the world as per the WHO. The paper characterizes the oral vaccines Dukoral, Shanchol, and mORCVAX in regards to their administration, effectiveness, and safety.

Harris, J. B., LaRocque, R. C., Qadri, F., Ryan, E. T. & Calderwood, S. B. Cholera. Lancet 379, 2466–2476 (2012).

  • This review describes the state of cholera in recent years. It includes etiological information regarding viral serogroups and briefly describes the mechanism by which the pathogen achieves virulence by elevating cAMP, thus leading to chloride secretion and secretory diarrhea. It also elucidates antibiotics currently employed in the management of cholera.

Jobling, M. G., Yang, Z., Kam, W. R., Lencer, W. I. & Holmes, R. K. A Single Native Ganglioside GM1-Binding Site Is Sufficient for Cholera Toxin To Bind to Cells and Complete the Intoxication Pathway. mBio 3, (2012).

  •  In the previous 2008 study, Jobling et al. demonstrated that multivalent binding of GM1 is nonessential for CT virulence. Here, the authors formally test this finding by creating homogenous chimeric holotoxins with defined numbers of native GM1 binding sites from zero (nonbinding) to five (WT). The authors concluded that a single GM1 binding site was sufficient for toxicity to occur.

Keddy, K. H. et al. Diagnosis of Vibrio cholerae O1 Infection in Africa. J. Infect. Dis. 208, S23–S31 (2013).

  • This article describes recent technologies that have been introduced in the diagnosis as well as phenotypic and molecular characterization of cholera in Africa. Rapid diagnostic testing based on lipopolysaccharide detection allows for quality management as well as early detection of the disease.

Qadir, M. I., Arshad, A. & Ahmad, B. Zinc: Role in the management of diarrhea and cholera. World J. Clin. Cases WJCC 1, 140–142 (2013).

  • This paper describes the role of zinc in the management of cholera symptoms when administered in tandem with the oral vaccine or oral rehydrating solutions. It appears that the administration of zinc reduces cAMP concentration as well as cholera toxin-induced ion secretion.

Reddy, S. et al. Grape Extracts Inhibit Multiple Events in the Cell Biology of Cholera Intoxication. PLoS ONE 8, e73390 (2013).

  •  Here, the authors demonstrate that grape extract prevented unfolding of the isolated CTA1 subunit, inhibited CTA1 translocation to the cytosol, and therefore disrupted the catalytic activity of CTA1. Hence, grape extract could potentially serve as a novel therapeutic to prevent or possibly treat cholera.

Ryan, E. T. Eyes on the Prize: Lessons from the Cholera Wars for Modern Scientists, Physicians, and Public Health Officials. Am. J. Trop. Med. Hyg. 89, 610–614 (2013).

  • This article outlines the history and implications of cholera pandemics that have occurred in the past. Among them are the first sightings of the disease among British troops in Calcutta in 1817, as well as the recent 2010 outbreak in Haiti, which is the largest in recorded history.

Saha, D. et al. Single-Dose Azithromycin for the Treatment of Cholera in Adults. N. Engl. J. Med. 354, 2452–2462 (2006).

  • Prior to this study, tetracycline had been the compound primarily used in the management of cholera. Although azithromycin had been demonstrated to be effective in children infected with cholera when administered in a single dose. In this study, the authors evaluate the equivalence in adults of single-dose azithromycin and single-dose ciprofloxacin, a regimen that had been previously demonstrated to be effective in the treatment of severe cholera.

Sanchez, J. & Holmgren, J. Cholera toxin — A foe & a friend. Indian J. Med. Res. 133, 153–163 (2011).

  • This review outlines pivotal research that has been performed on the CT since the discovery of the disease. Information regarding structure, genetic regulation, immunology, and toxin secretion is included.

Saslowsky, D. E. et al. Ganglioside GM1-mediated transcytosis of cholera toxin bypasses the retrograde pathway and depends on the structure of the ceramide domain. J. Biol. Chem. 288, 25804–25809 (2013).

  • It is known that in addition to being trafficked retrograde through sorting endosomes and the trans-Golgi network (TGN), a fraction of the cholera toxin also moves from endosomes across the cell to the basolateral plasma membrane by transcytosis. Here, the authors demonstrate that sorting of cholera toxin into this transcytotic pathway bypasses retrograde transport to the TGN. They also found that GM1 sphingolipids can traffic from apical to basolateral membranes by transcytosis in the absence of toxin binding but only if the GM1 species contain cis-unsaturated or short acyl chains in the ceramide domain.

Saslowsky, D. E. & Lencer, W. I. Conversion of apical plasma membrane sphingomyelin to ceramide attenuates the intoxication of host cells by cholera toxin. Cell. Microbiol. 10, 67–80 (2008).

  • Trafficking of CT toxin is dependent on the association of CT–GM1 complexes with sphingomyelin (SM)- and cholesterol-rich membrane microdomains termed lipid rafts. Here, the authors demonstrate that the conversion of apical membrane SM to ceramide by bacterial sphingomyelinase attenuates CT toxicity, an effect is reversible by the addition of exogenous long-chain ceramides. Interestingly, conversion of apical membrane SM to ceramide inhibits the efficiency of toxin endocytosis, but retrograde trafficking from the apical PM to the Golgi and ER is not affected, thus suggesting that toxin resistance that may be occurring at steps required for retro-translocation of the CT A1-chain to the cytosol.

Taylor, M. et al. Substrate-Induced Unfolding of Protein Disulfide Isomerase Displaces the Cholera Toxin A1 Subunit from Its Holotoxin. PLoS Pathog. 10, (2014).

  •  Protein disulfide isomarase is known to mediate the unfolding of the CTA1 subunit prior to retro-translocation to the cytosol. Here, the authors demonstrate that the enzyme itself unfolds upon binding of the CTA1, thus providing a novel molecular mechanism for holotoxin disassembly and the prevention of protein aggregation.

Teter, K., Jobling, M. G., Sentz, D. & Holmes, R. K. The Cholera Toxin A13 Subdomain Is Essential for Interaction with ADP-Ribosylation Factor 6 and Full Toxic Activity but Is Not Required for Translocation from the Endoplasmic Reticulum to the Cytosol. Infect. Immun. 74, 2259–2267 (2006).

  • Prior to this study, the role of of the hydrophobic CTA13 subdomain in the CTA1 passage from the ER to the cytosol had not been addressed. Previous, it was believed that it (i) acted as a trigger for ERAD-mediated export to the cytosol and (ii) promoted interaction with cytosolic ADP-ribosylation factors (ARFs) that served as allosteric activators of CTA1. Here the authors demonstrate that the subdomain is required for interaction with ARF6, but however is not required for ERAD-mediated transport of the subunit.

Wernick, N. L. B., Chinnapen, D. J.-F., Cho, J. A. & Lencer, W. I. Cholera Toxin: An Intracellular Journey into the Cytosol by Way of the Endoplasmic Reticulum. Toxins 2, 310–325 (2010).

  •  Cholera toxin (CT) infects host cells by binding the ganglioside GM1 at the plasma membrane and travels retrograde through the trans-Golgi Network into the ER. In the ER, the A1-chain of CT is unfolded by protein disulfide isomerase and retro-transocated to the cytosol. In this review, the authors outline the mechanisms by which the aforementioned actions occur.

Wolf, A. A. et al. Attenuated Endocytosis and Toxicity of a Mutant Cholera Toxin with Decreased Ability To Cluster Ganglioside GM1 Molecules. Infect. Immun. 76, 1476–1484 (2008).

  • In this study, the authors examined the role of polyvalent binding of GM1 in the virulence of the cholera toxin by producing chimeric CTs that had B-subunits with only one or two normal binding pockets. The authors concluded that although binding normally to one or two GM1 molecules is sufficient for toxin action, the mutants were much less potent than WT and entered the cell by endocytosis more slowly.

Zhang, R.-G. et al. The Three-dimensional Crystal Structure of Cholera Toxin. J. Mol. Biol. 251, 563–573 (1995).

  • In this study, the authors solved the crystal structure of the cholera toxin (PDB 1XTC) which is the primary cause of virulence in the disease. The author describe the structure as a hexameric AB5 enterotoxin which comprises of a single A subunit that is held high above the plane of the pentameric B subunits by a tethering A2 chain.