title: Actin polymerization stabilizes α4β1 integrin anchors that mediate monocyte adhesion.
abstract: Leukocytes arrested on inflamed endothelium via integrins are subjected to force imparted by flowing blood. How leukocytes respond to this force and resist detachment is poorly understood. Live-cell imaging with Lifeact-transfected U937 cells revealed that force triggers actin polymerization at upstream α4β1 integrin adhesion sites and the adjacent cortical cytoskeleton. Scanning electron microscopy revealed that this culminates in the formation of structures that anchor monocyte adhesion. Inhibition of actin polymerization resulted in cell deformation, displacement, and detachment. Transfection of dominant-negative constructs and inhibition of function or expression revealed key signaling steps required for upstream actin polymerization and adhesion stabilization. These included activation of Rap1, phosphoinositide 3-kinase γ isoform, and Rac but not Cdc42. Thus, rapid signaling and structural adaptations enable leukocytes to stabilize adhesion and resist detachment forces.
authors.affiliation: Toronto General Research Institute, University Health Network, Toronto, M5G 2C4 Ontario, Canada. jacob.rullo@utoronto.ca
authors.forename: Jacob
authors.initials: J
authors.lastname: Rullo
authors.forename: Henry
authors.initials: H
authors.lastname: Becker
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Hyduk
authors.forename: Janice C
authors.initials: JC
authors.lastname: Wong
authors.forename: Genevieve
authors.initials: G
authors.lastname: Digby
authors.forename: Pamma D
authors.initials: PD
authors.lastname: Arora
authors.forename: Adrianet Puig
authors.initials: AP
authors.lastname: Cano
authors.forename: John
authors.initials: J
authors.lastname: Hartwig
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McCulloch
authors.forename: Myron I
authors.initials: MI
authors.lastname: Cybulsky
mesh_terms: D000199:Actins / Q000378:metabolism*; D002448:Cell Adhesion; D002478:Cells, Cultured; D006801:Humans; D039041:Integrin alpha4beta1 / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000166:cytology* / Q000378:metabolism*; D020298:U937 Cells
chemical_list: D000199:Actins; D039041:Integrin alpha4beta1