Functional Binding of E-selectin to its Ligands is Enhanced by Structural Features Beyond its Lectin Domain
Fajr A. Aleisa et al., 2020 http://www.jbc.org/cgi/doi/10.1074/jbc.RA119.010910, attached
Using various Eselectin constructs produced in a newly developed silkworm-based expression system and several assays performed under both static and physiological flow conditions, including flow cytometry, glycan array analysis, surface plasmon resonance, and cell-rolling assays, we show here that a reduction in the number of SCR domains is correlated with a decline in functional E-selectin binding to hematopoietic cell E- or L- selectin ligand (HCELL) and P-selectin glycoprotein ligand-1 (PSGL-1). Moreover, the binding was significantly improved through E-selectin dimerization and by a substitution (A28H) that mimics an extended conformation of the lectin and EGF domains. Analyses of the association and dissociation rates indicated that the SCR domains, conformational extension, and dimerization collectively contribute to the association rate of Eselectin– ligand binding, whereas just the lectin and EGF domains contribute to the dissociation rate. These findings provide the first evidence of the critical role of the association rate in functional Eselectin– ligand interactions, and they highlight thatthe SCR domains have an important role that goesbeyond the structural extension of the lectin and EGF domains.