Targeting Multiple Binding Sites on Cholera Toxin B with Glycomimetic Polymers Promotes the Formation of Protein–Polymer Aggregates
- 5 October 2020
- journal article
- research article
- Published by American Chemical Society (ACS) in Biomacromolecules
- Vol. 21 (12), 4878-4887
- https://doi.org/10.1021/acs.biomac.0c01122
Abstract
The canonical binding site on the B subunit of cholera toxin (CTB) binds to GM1 gangliosides on host cells. However, the recently dis-covered noncanonical binding site on CTB with affinity for fucosylated molecules has raised the possibility that both sites can be involved in initiating intoxication. Previously, we showed that blocking CTB binding to human and murine small intestine epithelial cells can be increased by simultaneously targeting both binding sites with multivalent norbornene-based glycopolymers [ACS Infect. Dis. 2020, 6, 5, 1192–1203]. However, the mechanistic origin of the increased blocking efficacy was unclear. Herein, we observed that mixing CTB pen-tamers and glycopolymers that display fucose and galactose sugars results in the formation of large aggregates, which further inhibits bind-ing of CTB to human granulocytes. Dynamic light scattering analysis, small-angle X-ray scattering analysis, transmission electron micros-copy, and turbidimetric assays revealed that the facial directionality of CTB promotes interchain cross-linking, which in turn leads to self-assembly of protein–polymer networks. This cross-linking-induced self-assembly occurs only when the glycopolymer system contains both galactose and fucose. In an assay of the glycopolymer’s ability to block CTB binding to human granulocytes, we observed a direct correlation between IC50 and self-assembly size. The aggregation mechanism of inhibition proposed herein has potential utility for the development of low-cost macromolecular clinical therapeutics for cholera that do not have exotic architectures and do not require com-plex synthetic sequences.Keywords
Funding Information
- Division of Chemistry (CHE1609494)
- Vetenskapsr?det (2017-02646)
- American Chemical Society Petroleum Research Fund (55729-ND9)
- National Institute of General Medical Sciences (R01GM097971)
This publication has 61 references indexed in Scilit:
- Bacterial toxininhibitors based on multivalent scaffoldsChemical Society Reviews, 2013
- Bioengineered bugs expressing oligosaccharide receptor mimics: Toxin-binding probiotics for treatment and prevention of enteric infectionsBioengineered Bugs, 2010
- Synthesis and Affinity Evaluation of a Small Library of Bidentate Cholera Toxin Ligands: Towards Nonhydrolyzable Ganglioside MimicsChemistry – A European Journal, 2010
- Sialylated multivalent antigens engage CD22in transand inhibit B cell activationProceedings of the National Academy of Sciences of the United States of America, 2009
- The Protein Data BankNucleic Acids Research, 2000
- Carbohydrate Mimetics: A New Strategy for Tackling the Problem of Carbohydrate-Mediated Biological RecognitionAngewandte Chemie, 1999
- Sugar Mimics: An Artificial Receptor for Cholera ToxinJournal of the American Chemical Society, 1999
- Crystal structure of cholera toxin B‐pentamer bound to receptor GM1 pentasaccharideProtein Science, 1994
- Intestinal fluid and electrolyte transport in human choleraJCI Insight, 1970
- Intestinal Microftora in Asiatic Cholera. II. The Small BowelThe Journal of Infectious Diseases, 1970