Vibrio cholerae and Escherichia coli heat-labile enterotoxins and beyond

Heggelund, J.E.; Bjørnestad, Victoria Ariel; Krengel, Ute

doi:10.1016/b978-0-12-800188-2.00007-0

Cited by 25 publications

(31 citation statements)

References 261 publications

(331 reference statements)

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“…The bacteria colonize the small intestine and secrete the cholera toxin (CT) 4 . CT belongs to the protein family of AB 5 toxins that consist of one catalytically active A-subunit and a homopentamer of non-toxic B-subunits 4,5 . The CT B-pentamer (CTB) facilitates binding to epithelial cells in the small intestine and subsequent cellular uptake of the holotoxin 4, 6 .…”

Section: Introductionmentioning

confidence: 99%

“…CT belongs to the protein family of AB 5 toxins that consist of one catalytically active A-subunit and a homopentamer of non-toxic B-subunits 4,5 . The CT B-pentamer (CTB) facilitates binding to epithelial cells in the small intestine and subsequent cellular uptake of the holotoxin 4, 6 . In the cytosol, the A-subunit hijacks the cells’ own signalling pathways, causing the secretion of chloride ions into the intestinal lumen and, due to the osmotic gradient, ultimately the severe watery diarrhoea typical of cholera 6–8 .…”

Section: Introductionmentioning

confidence: 99%

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Crystal structures reveal that Lewis-x and fucose bind to secondary cholera toxin binding site – in contrast to fucosyl-GM1

Hodnik

et al. 2018

Preprint

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13Cholera is a life-threatening diarrhoeal disease caused by the human pathogen Vibrio cholerae. 14 Infection occurs after ingestion of the bacteria, which colonize the human small intestine and 15 secrete their major virulence factorthe cholera toxin (CT). Recent studies suggest that the 16 GM1 receptor may not be the only target of the CT, and that fucosylated receptors such as 17 Lewis x (Le x ) and histo-blood group antigens may also be important for cellular uptake and 18 toxicity. However, where and how Le x binds to the CT remains unclear. Here we report the high-19resolution crystal structure (1.5 Å) of the receptor-binding B-subunit of the CT bound to the Le x 20 trisaccharide, and present matching SPR data for CT holotoxins. Le x , and also L-fucose alone (at 21 500-fold molar excess), bind to the secondary binding site of the toxin, distinct from the GM1 22 binding site. In contrast, fucosyl-GM1 binds to the primary binding sites due to high-affinity 23 interactions of its GM1 core. The two binding sites are likely connected by allosteric cross-talk. 24 rabbit small bowel segments lead to a concentration-dependent increase in the number of toxin 46 receptors and in the sensitivity to the diarrheogenic action of CT 10,13 . CT binds GM1 at the 47 bottom surface of the B-pentamer, which serves as a landing platform on the cell membrane 12 . 48More recently, CT was found to bind histo-blood group antigens (BGAs) at a secondary binding 49 site on the lateral side of the B-pentamer, which had originally been discovered for chimeras of 50 CTB and the homologous Escherichia coli heat-labile enterotoxin (LTB) 18 . Cholera toxin 51 naturally occurs in two variants -classical CT (cCT) and El Tor CT (ET CT), which are 52 produced by the corresponding V. cholerae biotypes 4 . However, since 2001 a new vibrio strain 53 has been observed with characteristics of the El Tor biotype that produces CT with the classical 54 amino acid sequence 19 . The two variants only differ in residues 18 and 47 in the secondary CT 55 binding site (cCT: H18, T47, ET CT: Y18, I47) 4,20 , which is why they have been in the focus of 56 cholera blood group binding studies [21][22][23][24] . Moreover, there is increasing evidence that GM1 is not 57 the only CT receptor and may not even be its main receptor 18,25-31 . 58 Current research shows that fucosylated structures have an important role in cholera 59 intoxication 29,30 . CT binds fucosylated human BGAs merely with millimolar affinity 21-24 , but 60 nevertheless causes blood-group-dependent cellular intoxication 32 . Patients with blood group O 61 are also more likely to get severe cholera symptoms [33][34][35][36] . BGAs are present in the intestine in 62 high concentrations, especially compared to GM1 37 . Most recently, Le x , a BGA precursor 63 expressed on human granulocytes and intestinal cells, has been shown to specifically bind to 64 CTB and was proposed to function as a cellular receptor 30 . Cholera intoxication in mice can be 65 independent of GM1 30 , and fucose-based ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Crystal structures reveal that Lewis-x and fucose bind to secondary cholera toxin binding site – in contrast to fucosyl-GM1

Hodnik

et al. 2018

Preprint

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“…and blood-group antigen binding (Mudrak et al 2010;Heggelund et al 2015). However, the biological significance of the greater promiscuity of the LTB primary binding site and LPS binding has yet to be explained.…”

Section: Biological Contextmentioning

confidence: 99%

“…LT consists of an A-subunit inserted into a doughnut-shaped B-pentamer (LTB) (Sixma et al 1991). LT is structurally and functionally similar to the cholera toxin (CT), the main virulence factor of Vibrio cholerae, with which it shares approximately 82% sequence identity (Heggelund et al 2015). During infection, the bacteria colonize the intestine and secrete the holotoxins into the intestinal lumen where the B-pentamer is responsible for anchoring the toxin to the GM1-receptors present on the epithelial cells (Holmgren 1973).…”

Section: Biological Contextmentioning

confidence: 99%

1H, 13C, 15N backbone assignment of the human heat-labile enterotoxin B-pentamer and chemical shift mapping of neolactotetraose binding

et al. 2017

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The major virulence factor of enterotoxigenic Escherichia coli (ETEC) is the heat-labile enterotoxin (LT), an AB5 toxin closely related to the cholera toxin. LT consists of six subunits, the catalytically active A-subunit and five B-subunits arranged as a pentameric ring (LTB), which enable the toxin to bind to the epithelial cells in the intestinal lumen. LTB has two recognized binding sites; the primary binding site is responsible for anchoring the toxin to its main receptor, the GM1-ganglioside, while the secondary binding site recognizes blood group antigens. Herein, we report the 1 H, 13 C, 15 N main chain assignment of LTB from human isolates (hLTB; 103 a.a. per subunit, with a total molecular mass of 58.5 kDa). The secondary structure was predicted based on 13 C',

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“…The cholera toxin (CT) and the heat-labile enterotoxin (LT) consist of one catalytically active A-subunit bound to five non-toxic B-subunits that are arranged in a homopentamer (Merritt & Hol, 1995). The B-pentamers (CTB and LTB, respectively) are responsible for the binding to epithelial cells in the small intestine, facilitating the endocytosis of the toxin (Chinnapen et al, 2007;Heggelund et al, 2015). Inside the intestinal cell, the A-subunit causes a signaling cascade leading to watery diarrhea by the opening of ion channels.…”

Section: Introductionmentioning

confidence: 99%

Towards new cholera prophylactics and treatment: Crystal structures of bacterial enterotoxins in complex with GM1 mimics

Heggelund

Mackenzie

Martinsen

et al. 2016

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Cholera is a life-threatening disease in many countries, and new drugs are clearly needed. C-glycosidic antagonists may serve such a purpose. Here we report atomic-resolution crystal structures of three such compounds in complexes with the cholera toxin. The structures give unprecedented atomic details of the molecular interactions and show how the inhibitors efficiently block the GM1 binding site. These molecules are well suited for development into low-cost prophylactic drugs, due to their relatively easy synthesis and their resistance to glycolytic enzymes. One of the compounds links two toxin B-pentamers in the crystal structure, which may yield improved inhibition through the formation of toxin aggregates. These structures can spark the improved design of GM1 mimics, either alone or as multivalent inhibitors connecting multiple GM1-binding sites. Future developments may further include compounds that link the primary and secondary binding sites. Serving as decoys, receptor mimics may lessen symptoms while avoiding the use of antibiotics.

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Vibrio cholerae and Escherichia coli heat-labile enterotoxins and beyond

Cited by 25 publications

References 261 publications

Crystal structures reveal that Lewis-x and fucose bind to secondary cholera toxin binding site – in contrast to fucosyl-GM1

Crystal structures reveal that Lewis-x and fucose bind to secondary cholera toxin binding site – in contrast to fucosyl-GM1

1H, 13C, 15N backbone assignment of the human heat-labile enterotoxin B-pentamer and chemical shift mapping of neolactotetraose binding

Towards new cholera prophylactics and treatment: Crystal structures of bacterial enterotoxins in complex with GM1 mimics

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