title: P-selectin cross-links PSGL-1 and enhances neutrophil adhesion to fibrinogen and ICAM-1 in a Src kinase-dependent, but GPCR-independent mechanism.
abstract: Endothelial and platelet P-selectin (CD62P) and leukocyte integrin alpha(M)beta(2) (CD11bCD18, Mac-1) are cell adhesion molecules essential for host defense and innate immunity. Upon inflammatory challenges, P-selectin binds to PSGL-1 (P-selectin glycoprotein ligand-1, CD162) to mediate neutrophil rolling, during which integrins become activated by extracellular stimuli for their firm adhesion in a G-protein coupled receptor (GPCR)-dependent mechanism. Here we show that cross-linking of PSGL-1 by dimeric or multimeric forms of platelet P-selectin, P-selectin receptor-globulin, anti-PSGL-1 mAb and its F(ab')2 induced adhesion of human neutrophils to fibrinogen (Fg) and intercellular cell adhesion molecule-1 (ICAM-1, CD54) and triggered a moderate clustering of alpha(M)beta(2), but monomeric forms of soluble P-selectin and anti-PSGL-1 Fab did not. Interestingly, P-selectin did not induce a detectable interleukine-8 (IL-8) secretion (<0.1 ng/ml) in 30 minutes, whereas a high concentration of IL-8 (>50 ng/ml) was required to increase neutrophil adhesion to Fg. P-selectin-induced neutrophil adhesion was significantly inhibited by PP2 (a Src kinase inhibitor), but not by pertussis toxin (PTX; a GPCR inhibitor). Activated platelets also increased neutrophil binding to fibrinogen and triggered tyrosine phosphorylation of cellular proteins. Our results indicate that P-selectin-induced integrin activation (Src kinase-dependent) is distinct from that elicited by cytokines, chemokines, chemoattractants (GPCR-dependent), suggesting that these two signal transduction pathways may cooperate for maximal activation of leukocyte integrins.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, The Graduate School of Chinese Academy of Sciences, Shanghai, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhen H
authors.initials: ZH
authors.lastname: Geng
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Wang
authors.forename: Jin-Tao
authors.initials: JT
authors.lastname: Wang
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Geng
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D019281:Dimerization; D005340:Fibrinogen / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism*; D016209:Interleukin-8 / Q000096:biosynthesis / Q000276:immunology; D036904:Leukocyte Rolling / Q000187:drug effects / Q000502:physiology; D016177:Macrophage-1 Antigen / Q000276:immunology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D019007:P-Selectin; D037342:Pertussis Toxin / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*
chemical_list: C412373:AG 1879; D000911:Antibodies, Monoclonal; C508606:CXCL8 protein, human; D007140:Immunoglobulin Fab Fragments; D016209:Interleukin-8; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D011743:Pyrimidines; D043562:Receptors, G-Protein-Coupled; D018799:Intercellular Adhesion Molecule-1; D005340:Fibrinogen; D037342:Pertussis Toxin; D019061:src-Family Kinases