title: Rap1a activation by CalDAG-GEFI and p38 MAPK is involved in E-selectin-dependent slow leukocyte rolling.
abstract: Rolling leukocytes are exposed to different adhesion molecules and chemokines. Neutrophils rolling on E-selectin induce integrin αLβ2-mediated slow rolling on ICAM-1 by activating a phospholipase C (PLC)γ2-dependent and a separate PI3Kγ-dependent pathway. E-selectin-signaling cooperates with chemokine signaling to recruit neutrophils into inflamed tissues. However, the distal signaling pathway linking PLCγ2 (Plcg2) to αLβ2-activation is unknown. To identify this pathway, we used different Tat-fusion-mutants and gene-deficient mice in intravital microscopy, autoperfused flow chamber, peritonitis, and biochemical studies. We found that the small GTPase Rap1 is activated following E-selectin engagement and that blocking Rap1a in Pik3cg-/- mice by a dominant-negative Tat-fusion mutant completely abolished E-selectin-mediated slow rolling. We identified CalDAG-GEFI (Rasgrp2) and p38 MAPK as key signaling intermediates between PLCγ2 and Rap1a. Gαi-independent leukocyte adhesion to and transmigration through endothelial cells in inflamed postcapillary venules of the cremaster muscle were completely abolished in Rasgrp2-/- mice. The physiological importance of CalDAG-GEFI in E-selectin-dependent integrin activation is shown by complete inhibition of neutrophil recruitment into the inflamed peritoneal cavity of Rasgrp2-/- leukocytes treated with pertussis toxin to block Gαi-signaling. Our data demonstrate that Rap1a activation by p38 MAPK and CalDAG-GEFI is involved in E-selectin-dependent slow rolling and leukocyte recruitment.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University of Münster, Münster, Germany; Max-Planck Institute Münster, Münster, Germany.
authors.forename: Anika
authors.initials: A
authors.lastname: Stadtmann
authors.forename: Laura
authors.initials: L
authors.lastname: Brinkhaus
authors.forename: Helena
authors.initials: H
authors.lastname: Mueller
authors.forename: Jan
authors.initials: J
authors.lastname: Rossaint
authors.forename: Matteo
authors.initials: M
authors.lastname: Bolomini-Vittori
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bergmeier
authors.forename: Hugo
authors.initials: H
authors.lastname: Van Aken
authors.forename: Denisa D
authors.initials: DD
authors.lastname: Wagner
authors.forename: Carlo
authors.initials: C
authors.lastname: Laudanna
authors.forename: Klaus
authors.initials: K
authors.lastname: Ley
authors.forename: Alexander
authors.initials: A
authors.lastname: Zarbock
mesh_terms: D000818:Animals; D058544:Class Ib Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism; D019040:E-Selectin / Q000378:metabolism*; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism; D036904:Leukocyte Rolling; D016169:Lymphocyte Function-Associated Antigen-1; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020556:Neutrophil Infiltration / Q000235:genetics; D009504:Neutrophils / Q000502:physiology*; D010538:Peritonitis / Q000276:immunology / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D051966:Phospholipase C gamma; D015398:Signal Transduction; D057705:Transendothelial and Transepithelial Migration; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism
chemical_list: D019040:E-Selectin; D020662:Guanine Nucleotide Exchange Factors; D016023:Integrins; D016169:Lymphocyte Function-Associated Antigen-1; C485927:Rasgrp2 protein, mouse; D054322:tat Gene Products, Human Immunodeficiency Virus; D037342:Pertussis Toxin; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546764:Pik3cg protein, mouse; D048051:p38 Mitogen-Activated Protein Kinases; D051966:Phospholipase C gamma; D051960:GTP-Binding Protein alpha Subunit, Gi2; D020827:rap1 GTP-Binding Proteins