Adhesion-triggered rapid recruitment/exclusion of membrane-tethered ligands at cell–cell interface

Abstract

Various cell–cell interactions are triggered by the binding of ligands to receptors on the cell membrane. This binding occurs effectively within a biological membrane crowded with other types of membrane molecules. Understanding these initial binding events provides fundamental knowledge of cellular responses and insights into interface design for various biomedical applications, such as drug delivery systems, cell-based therapies, and the formation of multicellular aggregates. A detailed analysis requires an experimental model that can quantitatively track ligand–receptor binding at the membrane under controlled parameters. In this study, we used supported lipid bilayers (SLBs) as model cell membranes and a single-stranded DNA-poly(ethylene glycol)-phospholipid conjugate (ssDNA-PEG-lipid) as an artificial ligand–receptor system, as ssDNA-PEG-lipid allows for the rapid and non-toxic modification of the surface of living cells. The SLB was modified with a mixture of ssDNA-PEG-lipids carrying different DNA sequences to mimic a cell membrane that is crowded with multiple ligands. We found that cell attachment to the SLB via DNA hybridization resulted in the rapid recruitment of complementary ssDNA-PEG-lipids at the cell-attached interface and the exclusion of non-complementary ssDNA-PEG-lipids at the cell-attached interface. The recruitment and exclusion of ssDNA-PEG-lipids were observed even when the fraction of interacting ssDNA-PEG-lipids on the SLB decreased to 10%. These results suggest that the rapid localization change caused by the lateral diffusion of membrane-tethered ligands increases local ligand density, leading to efficient cell attachment.