title: Signal-dependent slow leukocyte rolling does not require cytoskeletal anchorage of P-selectin glycoprotein ligand-1 (PSGL-1) or integrin αLβ2.
abstract: In inflamed venules, neutrophils roll on P- or E-selectin, engage P-selectin glycoprotein ligand-1 (PSGL-1), and signal extension of integrin α(L)β(2) in a low affinity state to slow rolling on intercellular adhesion molecule-1 (ICAM-1). Cytoskeleton-dependent receptor clustering often triggers signaling, and it has been hypothesized that the cytoplasmic domain links PSGL-1 to the cytoskeleton. Chemokines cause rolling neutrophils to fully activate α(L)β(2), leading to arrest on ICAM-1. Cytoskeletal anchorage of α(L)β(2) has been linked to chemokine-triggered extension and force-regulated conversion to the high affinity state. We asked whether PSGL-1 must interact with the cytoskeleton to initiate signaling and whether α(L)β(2) must interact with the cytoskeleton to extend. Fluorescence recovery after photobleaching of transfected cells documented cytoskeletal restraint of PSGL-1. The lateral mobility of PSGL-1 similarly increased by depolymerizing actin filaments with latrunculin B or by mutating the cytoplasmic tail to impair binding to the cytoskeleton. Converting dimeric PSGL-1 to a monomer by replacing its transmembrane domain did not alter its mobility. By transducing retroviruses expressing WT or mutant PSGL-1 into bone marrow-derived macrophages from PSGL-1-deficient mice, we show that PSGL-1 required neither dimerization nor cytoskeletal anchorage to signal β(2) integrin-dependent slow rolling on P-selectin and ICAM-1. Depolymerizing actin filaments or decreasing actomyosin tension in neutrophils did not impair PSGL-1- or chemokine-mediated integrin extension. Unlike chemokines, PSGL-1 did not signal cytoskeleton-dependent swing out of the β(2)-hybrid domain associated with the high affinity state. The cytoskeletal independence of PSGL-1-initiated, α(L)β(2)-mediated slow rolling differs markedly from the cytoskeletal dependence of chemokine-initiated, α(L)β(2)-mediated arrest.
authors.affiliation: Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Bojing
authors.initials: B
authors.lastname: Shao
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Yago
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Coghill
authors.forename: Arkadiusz G
authors.initials: AG
authors.lastname: Klopocki
authors.forename: Padmaja
authors.initials: P
authors.lastname: Mehta-D'souza
authors.forename: David W
authors.initials: DW
authors.lastname: Schmidtke
authors.forename: William
authors.initials: W
authors.lastname: Rodgers
authors.forename: Rodger P
authors.initials: RP
authors.lastname: McEver
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000205:Actomyosin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D016466:CHO Cells; D018925:Chemokines / Q000235:genetics / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D036904:Leukocyte Rolling / Q000502:physiology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects / Q000502:physiology; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018925:Chemokines; C090509:Icam1 protein, mouse; D016169:Lymphocyte Function-Associated Antigen-1; D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D053778:Thiazolidines; D018799:Intercellular Adhesion Molecule-1; D000205:Actomyosin; C037068:latrunculin B