Functional analysis of the combined role of the O-linked branching enzyme core 2 beta1-6-N-glucosaminyltransferase and dimerization of P-selectin glycoprotein ligand-1 in rolling on P-selectin

J Biol Chem. 2004 May 21;279(21):21984-91. doi: 10.1074/jbc.M402731200. Epub 2004 Mar 16.

Abstract

Leukocyte P-selectin glycoprotein ligand-1 (PSGL-1) is expressed as a homodimer and mediates leukocyte rolling through interactions with endothelial P-selectin. Previous studies have shown that PSGL-1 must be properly modified by specific glycosyltransferases including alpha1,3-fucosyltransferase-VII, core 2 beta1-6-N-glucosaminyltransferase (C2GlcNAcT-I), one or more alpha2,3-sialytransferases, and a tyrosulfotransferase. In addition, dimerization of PSGL-1 through its sole extracellular cysteine (Cys(320)) is essential for rolling on P-selectin under shear conditions. In this report, we measured the contributions of both C2GlcNAcT-I glycosylation and dimerization of PSGL-1 to adhesive bonds formed during tethering and rolling of transfected cell lines on purified P-selectin. Tethering to P-selectin under flow increased with dimerization compared with cells expressing monomeric PSGL-1 (referred to as C320A). The rolling defects (decreased cellular accumulation, PSGL-1/P-selectin bond strengths and tethering rates, and increased velocities and skip distance) demonstrated by transfectants expressing monomeric PSGL-1 could be overcome by increasing the substrate P-selectin site density and by overexpressing C2GlcNAcT-I in C320A transfectants. Two molecular weight variants of PSGL-1 were isolated from cell lines transfected with PSGL-1, C320A, and/or C2GlcNAcT-I cDNAs, and these differences in electrophoretic mobility appeared to correlate with C2GlcNAcT-I expression. C320A transfectants expressing low molecular weight PSGL-1 had lower C2GlcNAcT-I levels (measured by reactivity to core 2 specific linkage antibody, CHO-131) and compromised rolling on P-selectin (regardless of site density) compared with C320A cells with high levels of C2GlcNAcT-I and high molecular weight PSGL-1. Both C2GlcNAcT-I glycosylation and PSGL-1 dimerization increased the rate of tethering to P-selectin under flow, whereas C2GlcNAcT-I levels primarily influenced tether bond strength.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Blotting, Southern
  • Blotting, Western
  • Cell Adhesion
  • Cell Line
  • DNA, Complementary / metabolism
  • Dimerization
  • Epitopes
  • Flow Cytometry
  • Glycosylation
  • Humans
  • Image Processing, Computer-Assisted
  • K562 Cells
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / metabolism
  • Microscopy, Video
  • N-Acetylglucosaminyltransferases / chemistry
  • N-Acetylglucosaminyltransferases / physiology*
  • P-Selectin / chemistry*
  • Protein Binding
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors
  • Transfection

Substances

  • DNA, Complementary
  • Epitopes
  • Membrane Glycoproteins
  • P-Selectin
  • P-selectin ligand protein
  • N-Acetylglucosaminyltransferases
  • beta-1,3-galactosyl-O-glycosyl-glycoprotein beta-1,6-acetylglucosaminyl transferase