Distinct roles for talin‐1 and kindlin‐3 in LFA‐1‐dependent neutrophil rolling and arrest

Abstract

β2 integrins, including LFA‐1 (αLβ2), play critical roles in leukocyte recruitment during inflammation by binding to ICAM‐1 expressed on the endothelium. The affinity of integrin for ligand is determined by its global conformation, regulated by the binding of proteins to the integrin cytoplasmic tails. At least three different integrin affinity states have been observed: low affinity with bent ectodomain, intermediate affinity with extended ectodomain, and high affinity with extended ectodomain and open headpiece. Intermediate affinity LFA‐1 contributes to neutrophil rolling interactions with the endothelium, whereas high affinity LFA‐1 mediates neutrophil arrest. In the current study, we determined the roles for two integrin activating proteins, talin‐1 and kindlin‐3, in neutrophil rolling and arrest. Using established in vivo (intravital microscopy of post‐capillary venules) and ex vivo (microfluidic flow chamber) models, we found that talin‐1 is necessary for both LFA‐1‐dependent neutrophil rolling and arrest. In contrast, kindlin‐3 was required only for neutrophil arrest and was dispensable for rolling mediated by intermediate affinity LFA‐1. We further corroborate our results with imaging and in vitro studies using antibodies that directly report β2 integrin conformation. These data indicate that talin‐1 is sufficient to induce LFA‐1 extension to an intermediate affinity state whereas kindlin‐3 is critical for the transition of LFA‐1 to a high affinity state.