title: Differential engagement of modules 1 and 4 of vascular cell adhesion molecule-1 (CD106) by integrins alpha4beta1 (CD49d/29) and alphaMbeta2 (CD11b/18) of eosinophils.
abstract: We have studied adhesion of eosinophils to various forms of vascular cell adhesion molecule 1 (VCAM-1, CD106), an integrin counter-receptor implicated in eosinophil recruitment to the airway in asthma. Full-length 7d-VCAM-1, with seven immunoglobulin-like modules, contains integrin-binding sites in modules 1 and 4. The alternatively spliced six-module protein, 6d-VCAM-1, lacks module 4. In static assays, unactivated purified human blood eosinophils adhered similarly to recombinant soluble human 6d-VCAM-1 and 7d-VCAM-1 coated onto polystyrene microtiter wells. Further experiments, however, revealed differences in recognition of modules 1 and 4. Antibody blocking indicated that eosinophil adhesion to 6d-VCAM-1 or a VCAM-1 construct containing only modules 1-3, 1-3VCAM-1, is mediated by alpha4beta1 (CD49d/29), whereas adhesion to a construct containing modules 4-7, 4-7VCAM-1, is mediated by bothalpha4beta1 andalphaMbeta2 (CD11b/18). Inhibitors of phosphoinositide 3-kinase, which block adhesion of eosinophils mediated by alphaMbeta2, blocked adhesion to 4-7VCAM-1 but had no effect on adhesion to 6d-VCAM-1. Consistent with the antibody and pharmacological blocking experiments, eosinophilic leukemic cell lines lacking alphaMbeta2 did not adhere to 4-7VCAM-1 but did adhere to 6d-VCAM-1 or 1-3VCAM-1. Activation of eosinophils by interleukin (IL)-5 enhanced static adhesion to 6d-VCAM-1, 7d-VCAM-1, or 4-7VCAM-1; IL-5-enhanced adhesion to all 3 constructs was blocked by anti-alphaMbeta2. Adhesion of unstimulated eosinophils to 7d-VCAM-1 under flow conditions was inhibited by anti-alpha4 or anti-alphaM. IL-5 treatment decreased eosinophil adhesion to 7d-VCAM-1 under flow, and anti-alphaM had the paradoxical effect of increasing adhesion. These results demonstrate that alphaMbeta2 modulatesalpha4beta1-mediated eosinophil adhesion to VCAM-1 under both static and flow conditions.
authors.affiliation: Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, 4285A Medical Sciences Center, 1300 University Avenue, Madison, WI 53706-1532, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Barthel
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Annis
authors.forename: Deane F
authors.initials: DF
authors.lastname: Mosher
authors.forename: Mats W
authors.initials: MW
authors.lastname: Johansson
mesh_terms: D001665:Binding Sites; D039481:CD11b Antigen / Q000378:metabolism*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D004804:Eosinophils / Q000737:chemistry* / Q000166:cytology / Q000276:immunology; D006801:Humans; D039041:Integrin alpha4beta1 / Q000378:metabolism*; D019169:Jurkat Cells; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D039481:CD11b Antigen; D039041:Integrin alpha4beta1; D011994:Recombinant Proteins; D019010:Vascular Cell Adhesion Molecule-1