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* Vascular Research Division, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston,
Massachusetts 02115; Leukocyte adhesion to vascular endothelium
under flow involves an adhesion cascade consisting of
multiple receptor pairs that may function in an overlapping fashion. P-selectin glycoprotein ligand-1 (PSGL-1)
and L-selectin have been implicated in neutrophil adhesion to P- and E-selectin under flow conditions. To
study, in isolation, the interaction of PSGL-1 with P-and
E-selectin under flow, we developed an in vitro model
in which various recombinant regions of extracellular
PSGL-1 were coupled to 10-µm-diameter microspheres. In a parallel plate chamber with well defined
flow conditions, live time video microscopy analyses revealed that microspheres coated with PSGL-1 attached
and rolled on 4-h tumor necrosis factor-
Small Molecule Drug Discovery Group, Genetics Institute, Cambridge, Massachusetts 02140; and § Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611
-activated endothelial cell monolayers, which express high levels of
E-selectin, and CHO monolayers stably expressing E-or P-selectin. Further studies using CHO-E and -P
monolayers demonstrate that the first 19 amino acids
of PSGL-1 are sufficient for attachment and rolling on
both E- and P-selectin and suggest that a sialyl Lewis
x-containing glycan at Threonine-16 is critical for this
sequence of amino acids to mediate attachment to
E- and P-selectin. The data also demonstrate that a sulfated, anionic polypeptide segment within the amino
terminus of PSGL-1 is necessary for PSGL-1-mediated
attachment to P- but not to E-selectin. In addition, the
results suggest that PSGL-1 has more than one binding site for E-selectin: one site located within the first 19 amino acids of PSGL-1 and one or more sites located
between amino acids 19 through 148.
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