Glycocalyx micro- and nanodomains in cell-cell and cell-matrix adhesions revealed by sensitive click chemistry
The glycocalyx consists of glycoproteins, glycolipids and extracellular polysaccharides at the cell surface which mediate viscoelastic and electrostatic barrier function. In molecular interactions the glycocalyx is thought to segregate locally to facilitate receptor-ligand binding, yet high-resolution maps of glycocalyx domains in cell-cell and cell-matrix interactions are lacking. We here applied TMTH-sulfoximine (THS)-based biorthogonal chemistry in live-cell culture and demonstrate much-enhanced glycocalyx detection, compared to established  dibenzocyclooctyne-based labeling. Using superresolution microscopy, we identified micron-scale moderately diminished glycocalyx in cell-cell contacts and subtotal depletion in protrusions at the leading and trailing edges and membrane blebs when cells invaded 3D fibrillar matrix. At contacts to collagen fibrils, focal integrin clusters segregated in outward-protrusive nanodomains from glycocalyx (distance: 350 nm), forming adhesion sites of low glycocalyx content. Thus, THS-based next-generation bioorthogonal labelling of live cells identifies micro- and nanodomains with altered glycocalyx density, implicating local glycocalyx downregulation in functional cell-cell and cell-matrix interactions. Overall design: RNA-sequencing to determine transcriptomic interference by metabolic labelling using Ac4ManNAz (5-day treatment), so comparing treated vs. untreated.