RT Journal Article SR Electronic T1 LFA-1 signals to promote actin polymerization and upstream migration in T cells JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.04.29.069302 DO 10.1101/2020.04.29.069302 A1 Nathan H Roy A1 Sarah Hyun Ji Kim A1 Alexander Buffone, Jr A1 Daniel Blumenthal A1 Bonnie Huang A1 Sangya Agarwal A1 Pamela L Schwartzberg A1 Daniel A Hammer A1 Janis K Burkhardt YR 2020 UL http://biorxiv.org/content/early/2020/05/02/2020.04.29.069302.abstract AB T cell entry into inflamed tissue requires firm adhesion, cell spreading, and migration along and through the endothelial wall. These events require the T cell integrins LFA-1 and VLA-4 and their endothelial ligands ICAM-1 and VCAM-1, respectively. T cells migrate against the direction of shear flow on ICAM-1 and with the direction of shear flow on VCAM-1, suggesting that these two ligands trigger distinct cellular responses. However, the contribution of specific signaling events downstream of LFA-1 and VLA-4 has not been explored. Using primary mouse T cells, we found that engagement of LFA-1, but not VLA-4, induces cell shape changes associated with rapid 2D migration. Moreover, LFA-1 ligation results in activation of the PI3K and ERK pathways, and phosphorylation of multiple kinases and adaptor proteins, while VLA-4 ligation triggers only a subset of these signaling events. Importantly, T cells lacking Crk adaptor proteins, key LFA-1 signaling intermediates, or the ubiquitin ligase cCbl, failed to migrate against the direction of shear flow on ICAM-1. These studies identify novel signaling differences downstream of LFA-1 and VLA-4 that drive T cell migratory behavior.Summary Statement Inflammatory responses require leukocyte migration along the vascular wall. We show that signaling from β2, but not β1, integrins induces cytoskeletal changes needed for upstream migration under shear flow.