title: Soluble monomeric P-selectin containing only the lectin and epidermal growth factor domains binds to P-selectin glycoprotein ligand-1 on leukocytes.
abstract: Under shear stress, leukocytes use P-selectin glycoprotein ligand-1 (PSGL-1) to tether to and roll on P-selectin expressed on activated platelets or endothelial cells. P-selectin has an NH2-terminal lectin domain, an epidermal growth factor (EGF)-like motif, nine consensus repeats (CRs), a transmembrane domain, and a cytoplasmic tail. To determine whether the CRs are required for P-selectin to bind PSGL-1, we expressed a soluble protein (Lec-EGF) that contained only the lectin and EGF domains, plus a short C-terminal epitope tag. Electron microscopy and hydrodynamic analysis confirmed that Lec-EGF was monomeric, as previously shown for soluble P-selectin (sPS) that contained the lectin and EGF domains plus all nine CRs. Fluid-phase Lec-EGF or sPS inhibited binding of oligomeric125I-labeled membrane-derived P-selectin (mPS) to PSGL-1 on neutrophils and binding of 125I-PSGL-1 to immobilized mPS. The IC50 for inhibiting binding of mPS to neutrophils was fivefold greater for Lec-EGF than for sPS, whereas the IC50 for inhibiting binding of mPS to purified PSGL-1 was indistinguishable for Lec-EGF and sPS. Under static or shear conditions, neutrophils used PSGL-1 to tether to or roll on Lec-EGF that was captured by an immobilized monoclonal antibody to the C-terminal epitope. These data show that P-selectin requires only the lectin and EGF domains to bind to PSGL-1.
authors.affiliation: W. K. Warren Medical Research Institute, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City 73104, USA.
authors.forename: P
authors.initials: P
authors.lastname: Mehta
authors.forename: K D
authors.initials: KD
authors.lastname: Patel
authors.forename: T M
authors.initials: TM
authors.lastname: Laue
authors.forename: H P
authors.initials: HP
authors.lastname: Erickson
authors.forename: R P
authors.initials: RP
authors.lastname: McEver
mesh_terms: D002448:Cell Adhesion; D004815:Epidermal Growth Factor / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009504:Neutrophils / Q000166:cytology*; D019007:P-Selectin / Q000737:chemistry*; D011485:Protein Binding; D012995:Solubility; D013329:Structure-Activity Relationship; D014461:Ultracentrifugation
chemical_list: D008024:Ligands; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D004815:Epidermal Growth Factor