title: Tyrosine replacement in P-selectin glycoprotein ligand-1 affects distinct kinetic and mechanical properties of bonds with P- and L-selectin.
abstract: Selectins are adhesion molecules that initiate tethering and rolling of leukocytes on the vessel wall. Rolling requires rapid formation and breakage of selectin-ligand bonds that must have mechanical strength to resist premature dissociation by the forces applied in shear flow. P- and L-selectin bind to the N-terminal region of P-selectin glycoprotein ligand-1 (PSGL-1), a mucin on leukocytes. To define determinants on PSGL-1 that contribute to the kinetic and mechanical properties of bonds with selectins, we compared rolling of transfected preB cells expressing P- or L-selectin on transfected cell monolayers expressing wild-type PSGL-1 or PSGL-1 constructs with substitutions in targeted N-terminal residues. Rolling through P- or L-selectin required a Thr or Ser at a specific position on PSGL-1, the attachment site for an essential O-glycan, but required only one of three nearby Tyr residues, which are sites for Tyr-SO(3) formation. The adhesive strengths and numbers of cells rolling through P- or L-selectin were similar on wild-type PSGL-1 and on each of the three PSGL-1 constructs containing only a single Tyr. However, the cells rolled more irregularly on the single-Tyr forms of PSGL-1. Analysis of the lifetimes of transient tethers on limiting densities of PSGL-1 revealed that L-selectin dissociated faster from single-Tyr than wild-type PSGL-1 at all shears examined. In sharp contrast, P-selectin dissociated faster from single-Tyr than wild-type PSGL-1 at higher shear but not at lower shear. Thus, tyrosine replacements in PSGL-1 affect distinct kinetic and mechanical properties of bonds with P- and L-selectin.
authors.affiliation: W. K. Warren Medical Research Institute, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: V
authors.initials: V
authors.lastname: Ramachandran
authors.forename: M U
authors.initials: MU
authors.lastname: Nollert
authors.forename: H
authors.initials: H
authors.lastname: Qiu
authors.forename: W J
authors.initials: WJ
authors.lastname: Liu
authors.forename: R D
authors.initials: RD
authors.lastname: Cummings
authors.forename: C
authors.initials: C
authors.lastname: Zhu
authors.forename: R P
authors.initials: RP
authors.lastname: McEver
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D015870:Gene Expression; D005818:Genetic Engineering; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D019041:L-Selectin / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009077:Mucins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D019007:P-Selectin / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism*
chemical_list: D008024:Ligands; D008562:Membrane Glycoproteins; D009077:Mucins; D019007:P-Selectin; C084882:P-selectin ligand protein; D019041:L-Selectin; D014443:Tyrosine