title: Migrational guidance of neutrophils is mechanotransduced via high-affinity LFA-1 and calcium flux.
abstract: Acute inflammation triggers the innate immune response of neutrophils that efficiently traffic from the bloodstream to concentrate at high numbers at the site of tissue infection or wounding. A gatekeeper in this process is activation of β(2) integrins, which form bond clusters with ICAM-1 on the endothelial surface. These bond clusters serve dual functions of providing adhesive strength to anchor neutrophils under the shear forces of blood flow and directional guidance for cell polarization and subsequent transmigration on inflamed endothelium. We hypothesized that shear forces transmitted through high-affinity LFA-1 facilitates the cooperation with the calcium release-activated channel Orai1 in directing localized cytoskeletal activation and directed migration. By using vascular mimetic microfluidic channels, we observed neutrophil arrest on a substrate of either ICAM-1 or allosteric Abs that stabilize a high- or low-affinity conformation of LFA-1. Neutrophils captured via low-affinity LFA-1 did not exhibit intracellular calcium flux, F-actin polymerization, cell polarization, or directional migration under shear flow. In contrast, high-affinity LFA-1 provided orientation along a uropod-pseudopod axis that required calcium flux through Orai1. We demonstrate how the shear stress of blood flow can transduce distinct outside-in signals at focal sites of high-affinity LFA-1 that provide contact-mediated guidance for neutrophil emigration.
authors.affiliation: Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA.
authors.forename: Neha
authors.initials: N
authors.lastname: Dixit
authors.forename: Itsukyo
authors.initials: I
authors.lastname: Yamayoshi
authors.forename: Ari
authors.initials: A
authors.lastname: Nazarian
authors.forename: Scott I
authors.initials: SI
authors.lastname: Simon
mesh_terms: D000199:Actins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000328:Adult; D000818:Animals; D015220:Calcium Channels / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D020013:Calcium Signaling / Q000276:immunology*; D002448:Cell Adhesion / Q000276:immunology; D002465:Cell Movement / Q000276:immunology*; D016764:Cell Polarity / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D009504:Neutrophils / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D000071740:ORAI1 Protein; D011485:Protein Binding / Q000276:immunology
chemical_list: D000199:Actins; D015220:Calcium Channels; D016169:Lymphocyte Function-Associated Antigen-1; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; D018799:Intercellular Adhesion Molecule-1