Competition for membrane receptors: norovirus detachment via lectin attachment.

Virus internalization into the host cells occurs via multivalent interaction with laterally mobile receptor molecules in the plasma membrane. Because of analytical and experimental limitations this complex type of interaction is still poorly understood and quantified. Herein, the multivalent interaction of norovirus-like particles (noroVLPs) with H or B type 1 glycosphingolipid receptors embedded in a supported phospholipid bilayer is investigated by following the competition between noroVLPs and a lectin (from Ralstonia solanacearum) upon binding to these receptors. Changes in noroVLP and lectin coverage, caused by competition, were monitored for both receptor types and at different concentrations of the receptors using quartz crystal microbalance with dissipation monitoring, yielding information about i) the minimum receptor concentration needed for noroVLPs to achieve firm attachment to the bilayer prior to competition, and to ii) remain firmly attached to the bilayer during competition. We show that these two concentrations are almost identical for the H type 1-noroVLP interaction, but differ for B type 1, indicating an accumulation of B type 1 receptors in the noroVLP-bilayer interaction area. Furthermore, the receptor concentration required for firm attachment is significantly larger for H type 1 than for B type 1, indicating a higher affinity of noroVLP towards B type 1. This finding is supported by extracting the energy of single noroVLP-H type 1 and noroVLP-B type 1 bonds from the competition kinetics, which were estimated to be 5 and 6 kcal/mol, respectively. This demonstrates the potential of utilizing competitive receptor-binding kinetics to analyse multivalent interactions, which has remained difficult to quantify using conventional approaches.