Amphiphilic and ganglioside-binding properties of SARS CoV-2 Spike protein variants dissected by charge shift electrophoresis in deterged solution

The data contained in this thesis provide a demonstration of the amphiphilic properties of SARS-2-S, the Spike glycoprotein of SARS-CoV-2, as well as of its  (B.1.617.2, delta) and  (B.1.1.529, omicron) variants, obtained by charge shift electrophoresis (CSE) in detergent solution. Wild-type,  and  SARS-2-S presented distinct amphiphilic properties, reflecting their ability to participate in the formation of mixed TX-100/DOC and TX-100/CTAB micelles of homogeneous size. The SARS-2-S  plus variant exhibited a more limited amphiphilicity in TX/DOC, possibly reflecting its propensity for TX-100/DOC micelles with a lower DOC content, perhaps due to charge-specific interactions between DOC and positively charged amino acids. We also provide a demonstration of the ability of different variants of the SARS-CoV-2 Spike glycoprotein to bind GM1 ganglioside, by the same approach, in the absence of detergents. Even though the sialoside-binding ability of coronaviruses was known, ours is the first direct demonstration of the GM1-ganglioside-binding ability of the SARS-2-S glycoprotein. Unlike wild-type SARS-2-S and the SARS-2-S  variant, the SARS-2-S  and  plus variants exhibited, after pre-incubation with GM1, anodal shifts characterized by variable degrees of polydispersity of migration, that likely reflected the formation of heterogeneous populations of micelles and/or aggregates of GM1 ganglioside and SARS-2-S conformers, as though the interaction with GM1 had a disordering effect upon these SARS-2-S variants. Investigation of the determinants of such diverse responses to the interaction with GM1 may help decipher how genetic variation can affect the fusogenic activity and infectivity of SARS-CoV-2 variants. Elucidating the contribution of GM1 binding to SARS-2-S-mediated viral attachment and entry into target cells might pave the way to the development of inhibitors of SARS-CoV-2 infection, based on multimers of oligosaccharides that mimic membrane-bound GM1.