UCSF

Abstract: Neutrophils are the most abundant leukocytes in human blood. Neutrophil malfunction may cause various immunological diseases. Beta2 integrins are critical for neutrophil recruitment. Kindlin-3 and talin-1 are important regulators for beta2 integrin activation. We have confirmed this using conformation-specific antibodies KIM127 and mAb24 that recognize activation epitopes in beta2 integrin. Besides activation, clustering is also critical for beta2 integrin avidity and adhesion of neutrophils. Whether kindlin-3 and talin-1 are involved in beta2 integrin clustering remains unclear. Here we used super-resolution stochastic optical reconstruction microscopy (STORM) to study their roles in beta2 integrin clustering on human neutrophil-like HL60 cells. We find that lymphocyte function-associated antigen 1 (LFA-1) and macrophage-1 antigen (Mac-1) are significantly clustered in wild-type cells after IL-8 or fMLP stimulation. Using CRISPR-Cas9-mediated kindlin-3 and talin-1 knockout HL60 cells, we found that kindlin-3 but not talin-1 are responsible for beta2 integrin clustering. Our study provides new insights into the regulation of beta2 integrin clustering and leukocyte recruitment. Supported by grants from the National Institutes of Health, National Heart, Lung, and Blood Institute, USA (R01HL145454), and a startup fund from UConn Health.