Structured clustering of the glycosphingolipid GM1 is required for membrane curvature induced by cholera toxin

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 26; pp. 14978 - 14986
• Main Authors: Kabbani, Abir Maarouf, Raghunathan, Krishnan, Lencer, Wayne I., Kenworthy, Anne K., Kelly, Christopher V.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 30.06.2020
• Subjects: Animals; Antibodies; Binding sites; Biological Sciences; Cell Membrane - chemistry; Cell Membrane - drug effects; Cell Membrane - metabolism; Ceramide; Chlorocebus aethiops; Cholera; Cholera toxin; Cholera Toxin - pharmacology; Clustering; COS Cells; Crosslinking; Curvature; Glycosphingolipids; Infections; Internalization; Localization; Membranes; Mutants; Phenotypes; Physical Sciences; Receptors; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Toxins; Waterborne diseases; gangliosides; binding stoichiometry; curvature generation; clathrin-independent endocytosis; toxins
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2001119117

AB₅ bacterial toxins and polyomaviruses induce membrane curvature as a mechanism to facilitate their entry into host cells. How membrane bending is accomplished is not yet fully understood but has been linked to the simultaneous binding of the pentameric B subunit to multiple copies of glycosphingolipid receptors. Here, we probe the toxin membrane binding and internalization mechanisms by using a combination of superresolution and polarized localization microscopy. We show that cholera toxin subunit B (CTxB) can induce membrane curvature only when bound to multiple copies of its glycosphingolipid receptor, GM1, and the ceramide structure of GM1 is likely not a determinant of this activity as assessed in model membranes. A mutant CTxB capable of binding only a single GM1 fails to generate curvature either in model membranes or in cells, and clustering the mutant CTxB–single-GM1 complexes by antibody cross-linking does not rescue the membrane curvature phenotype. We conclude that both the multiplicity and specific geometry of GM1 binding sites are necessary for the induction of membrane curvature. We expect this to be a general rule of membrane behavior for all AB₅ toxins and polyomaviruses that bind glycosphingolipids to invade host cells.