title: Function of the lectin domain of Mac-1/complement receptor type 3 (CD11b/CD18) in regulating neutrophil adhesion.
abstract: A lectin function within CD11b mediates both cytotoxic priming of Mac-1/complement receptor type 3 (CR3) by beta-glucan and the formation of transmembrane signaling complexes with GPI-anchored glycoproteins such as CD16b (FcgammaRIIIb). A requirement for GPI-anchored urokinase plasminogen activator receptor (uPAR; CD87) in neutrophil adhesion and diapedesis has been demonstrated with uPAR-knockout mice. In this study, neutrophil activation conditions generating high-affinity (H-AFN) or low-affinity (L-AFN) beta(2) integrin adhesion were explored. A role for the Mac-1/CR3 lectin domain and uPAR in mediating H-AFN or L-AFN adhesion was suggested by the inhibition of Mac-1/CR3-dependent adhesion to ICAM-1 or fibrinogen by beta-glucan or anti-uPAR. The formation of uPAR complexes with Mac-1/CR3 activated for L-AFN adhesion was demonstrated by fluorescence resonance energy transfer. Conversely, Jurkat cell LFA-1 H-AFN-adhesion to ICAM-1 was not associated with uPAR/LFA-1 complexes, any requirement for GPI-anchored glycoproteins, or inhibition by beta-glucan. A single CD11b lectin site for beta-glucan and uPAR was suggested because the binding of either beta-glucan or uPAR to Mac-1/CR3 selectively masked two CD11b epitopes adjacent to the transmembrane domain. Moreover, treatment with phosphatidylinositol-specific phospholipase C that removed GPI-anchored proteins increased CD11b-specific binding of (125)I-labeled beta-glucan by 3-fold and this was reversed with soluble recombinant uPAR. Conversely, neutrophil activation for generation of Mac-1/CR3/uPAR complexes inhibited CD11b-dependent binding of (125)I-labeled beta-glucan by 75%. These data indicate that the same lectin domain within CD11b regulates both the cytotoxic and adhesion functions of Mac-1/CR3.
authors.affiliation: Chemoattractant Group of the James Graham Brown Cancer Center, Department of Pathology, University of Louisville, KY 40202, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Xia
authors.forename: Gita
authors.initials: G
authors.lastname: Borland
authors.forename: Jibiao
authors.initials: J
authors.lastname: Huang
authors.forename: Ikuko F
authors.initials: IF
authors.lastname: Mizukami
authors.forename: Howard R
authors.initials: HR
authors.lastname: Petty
authors.forename: Robert F
authors.initials: RF
authors.lastname: Todd
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Ross
mesh_terms: D000818:Animals; D001665:Binding Sites; D039481:CD11b Antigen / Q000737:chemistry* / Q000378:metabolism; D018821:CD18 Antigens / Q000737:chemistry* / Q000378:metabolism; D002448:Cell Adhesion / Q000276:immunology; D000939:Epitopes / Q000737:chemistry; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D019169:Jurkat Cells; D037102:Lectins / Q000737:chemistry / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D009504:Neutrophils / Q000166:cytology* / Q000276:immunology*; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology
chemical_list: D039481:CD11b Antigen; D018821:CD18 Antigens; D000939:Epitopes; D017261:Glycosylphosphatidylinositols; D037102:Lectins; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; C524898:PLAUR protein, human; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator