The activation state of alphavbeta 3 regulates platelet and lymphocyte adhesion to intact and thrombin-cleaved osteopontin

J Biol Chem. 2000 Jun 16;275(24):18337-43. doi: 10.1074/jbc.M001529200.

Abstract

Cleavage of osteopontin by thrombin has been reported to enhance cell adhesion. We asked whether thrombin could regulate the alpha(v)beta(3)-mediated adhesion of platelets and B lymphocytes to this substrate. Although there was no difference in the extent or the avidity of thrombin- and ADP-stimulated platelet adhesion to intact or thrombin-cleaved human osteopontin, both the extent and avidity of phorbol ester-stimulated B cell adhesion to thrombin-cleaved osteopontin was significantly increased. Thus, these data suggest that the ability of alpha(v)beta(3) to recognize osteopontin can be differentially regulated in a cell-specific manner. To localize the alpha(v)beta(3) binding site on osteopontin, we measured cell adhesion to the two thrombin cleavage products of osteopontin and to a series of nested RGD-containing osteopontin peptides cross-linked to albumin. Whereas ADP-stimulated platelets adhered to the amino-terminal but not the carboxyl-terminal osteopontin fragment and to the osteopontin peptide RGDSVVYGLR, phorbol ester-stimulated B cells did not adhere to this peptide, although they did so in the presence of 1 mm Mn(2+). Thus, our data confirm that thrombin cleavage enhances the accessibility of the binding motif for alpha(v)beta(3) on osteopontin, but this enhancement is also a function of the activation state of alpha(v)beta(3). Moreover, they indicate that the sequence RGDSVVYGLR contains sufficient information to specify activation-dependent alpha(v)beta(3)-mediated platelet and lymphocyte adhesion.

Publication types

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

MeSH terms

  • Adenosine Diphosphate / pharmacology
  • B-Lymphocytes / physiology*
  • Blood Platelets / drug effects
  • Cell Adhesion*
  • Circular Dichroism
  • Electrophoresis, Polyacrylamide Gel
  • Herpesvirus 4, Human
  • Humans
  • Magnesium / pharmacology
  • Magnetic Resonance Spectroscopy
  • Osteopontin
  • Platelet Adhesiveness*
  • Protein Conformation
  • Receptors, Vitronectin / physiology*
  • Sialoglycoproteins / metabolism*
  • Thrombin / metabolism*

Substances

  • Receptors, Vitronectin
  • SPP1 protein, human
  • Sialoglycoproteins
  • Osteopontin
  • Adenosine Diphosphate
  • Thrombin
  • Magnesium