Shear forces induce ICAM-1 nanoclustering on endothelial cells that impact on T cell migration

Abstract

The leukocyte specific β2-integrin LFA-1, and its ligand ICAM-1 expressed on endothelial cells (ECs), are involved in the arrest, adhesion and transendothelial migration of leukocytes. Although the role of mechanical forces on LFA-1 activation is wellestablished, the impact of forces on its major ligand ICAM-1, has received less attention. Using a parallel-plate flow-chamber combined with confocal and super-resolution microscopy, we show that prolonged shear-flow induces global translocation of ICAM-1 on ECs upstream of flow direction. Interestingly, shear-forces caused actin rearrangements and promoted actin-dependent ICAM-1 nanoclustering prior to LFA-1 engagement. T-cells adhered to mechanically pre-stimulated ECs or nanoclustered ICAM-1 substrates, developed a pro-migratory phenotype, migrated faster and exhibited shorter-lived interactions with ECs than when adhered to non-mechanically stimulated ECs, or to monomeric ICAM-1 substrates. Together, our results indicate that shearforces increase ICAM-1/LFA-1 bonds due to ICAM-1 nanoclustering, strengthening adhesion and allowing cells to exert higher traction forces required for faster migration. Our data also underscores the importance of mechanical forces regulating the nanoscale organization of membrane receptors and their contribution to cell adhesion regulation.