title: P-Selectin glycoprotein ligand 1 (PSGL-1) is expressed on platelets and can mediate platelet-endothelial interactions in vivo.
abstract: The platelet plays a pivotal role in maintaining vascular integrity. In a manner similar to leukocytes, platelets interact with selectins expressed on activated endothelium. P-selectin glycoprotein ligand 1 (PSGL-1) is the main P-selectin ligand expressed on leukocytes. Searching for platelet ligand(s), we used a P-selectin-immunoglobulin G (IgG) chimera to affinity purify surface-biotinylated proteins from platelet lysates. P-selectin-bound ligands were eluted with ethylenediaminetetraacetic acid. An approximately 210-kD biotinylated protein was isolated from both human neutrophil and platelet preparations. A band of the same size was also immunopurified from human platelets using a monoclonal anti-human PSGL-1 antibody and could be blotted with P-selectin-IgG. Under reducing conditions, both the predicted PSGL-1 approximately 210-kD dimer and the approximately 120-kD monomer were isolated from platelets. Comparative immunoelectron microscopy and Western blotting experiments suggested that platelet PSGL-1 expression is 25-100-fold lower than that of leukocytes. However, patients with chronic idiopathic thrombocytopenic purpura who harbor predominantly young platelets displayed greater expression, indicating that PSGL-1 expression may be decreased during platelet aging. By flow cytometry, thrombin-activated platelets from normal individuals exhibited greater expression than those unstimulated. An inhibitory anti-PSGL-1 antibody significantly reduced platelet rolling in mesenteric venules, as observed by intravital microscopy. Our results indicate that functional PSGL-1 is expressed on platelets, and suggest an additional mechanism by which selectins and their ligands participate in inflammatory and/or hemostatic responses.
authors.affiliation: The Center for Blood Research, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA. paul.frenette@mssm.edu
authors.forename: P S
authors.initials: PS
authors.lastname: Frenette
authors.forename: C V
authors.initials: CV
authors.lastname: Denis
authors.forename: L
authors.initials: L
authors.lastname: Weiss
authors.forename: K
authors.initials: K
authors.lastname: Jurk
authors.forename: S
authors.initials: S
authors.lastname: Subbarao
authors.forename: B
authors.initials: B
authors.lastname: Kehrel
authors.forename: J H
authors.initials: JH
authors.lastname: Hartwig
authors.forename: D
authors.initials: D
authors.lastname: Vestweber
authors.forename: D D
authors.initials: DD
authors.lastname: Wagner
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D001792:Blood Platelets / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D017931:DNA Primers / Q000235:genetics; D004730:Endothelium, Vascular / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000097:blood* / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D019007:P-Selectin / Q000097:blood*; D015539:Platelet Activation; D012333:RNA, Messenger / Q000097:blood / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D017931:DNA Primers; D008024:Ligands; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D012333:RNA, Messenger