title: Cytohesin-1 regulates human blood neutrophil adhesion to endothelial cells through β2 integrin activation.
abstract: Cytohesin-1 is a guanine nucleotide exchange factor for ADP ribosylation factor 6 (Arf6) in human blood neutrophils and differentiated PLB-985 neutrophil-like cells. Cytohesin-1 regulates adhesion and the transendothelial migration of monocytes, dendritic cells and T lymphocytes through activation of the β2 integrin LFA-1. In this study we investigated the role of cytohesin-1 in neutrophil and neutrophil-like cell adhesion to HUVECs, immobilized ICAM-1, and the α4β1 and α5β1 integrin extracellular matrix ligand fibronectin. We show that cytohesin-1 knockdown or inhibition with secinH3 inhibits fMLF-mediated cell adhesion to HUVECs and immobilized ICAM-1, whereas cytohesin-1 over-expression has the opposing effect. Binding of PLB-985 cells to HUVECs correlated with expression of the high-affinity β2 integrin epitope recognized by mAb24. Adhesion to HUVECs was inhibited by soluble ICAM-1, anti-ICAM-1, anti-CD11a and anti-CD18, but not anti-CD11b, blocking antibodies. We also demonstrate that cytohesin-1 knockdown promotes fMLF-mediated cell adhesion to fibronectin whereas cytohesin-1 over-expression has the opposing effect. Crosstalk between β1 and β2 integrins also exists since inhibition of β1 integrin functions with blocking antibodies enhanced adhesion of PLB-985 over-expressing cytohesin-1 to ICAM-1. We suggest that cytohesin-1 is a key regulator of neutrophil adhesion to endothelial cells and to components of extracellular matrix, which may influence cell emigration through its dual opposing effect on β2 and β1 integrin activation.
authors.affiliation: Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ-CHUL, Québec, Canada.
authors.forename: Mohammed-Amine
authors.initials: MA
authors.lastname: El azreq
authors.forename: Sylvain G
authors.initials: SG
authors.lastname: Bourgoin
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D000328:Adult; D000911:Antibodies, Monoclonal; D018845:CD11 Antigens / Q000276:immunology; D018821:CD18 Antigens / Q000276:immunology / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000276:immunology / Q000502:physiology*; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000502:physiology*; D034741:RNA, Small Interfering; D014230:Triazoles / Q000494:pharmacology; D014469:Umbilical Arteries
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000911:Antibodies, Monoclonal; D018845:CD11 Antigens; D018821:CD18 Antigens; D005353:Fibronectins; D020662:Guanine Nucleotide Exchange Factors; D034741:RNA, Small Interfering; C516025:SecinH3; D014230:Triazoles; C100723:cytohesin-1; D018799:Intercellular Adhesion Molecule-1; C000715348:ARF6 protein, human