Falciparum malaria parasitized erythrocytes bind to a carboxy-terminal thrombospondin fragment and not the amino-terminal heparin-binding region

Mol Biochem Parasitol. 1990 May;40(2):173-81. doi: 10.1016/0166-6851(90)90039-o.

Abstract

We investigated Plasmodium falciparum parasitized erythrocyte binding to proteolytic fragments of thrombospondin and the effects of anti-thrombospondin monoclonal antibodies on this binding. Purified human platelet thrombospondin was cleaved by trypsin, chymotrypsin or thrombin. Fragments were separated by heparin-agarose affinity chromatography, removing the amino-terminal heparin-binding region. Trypsin at 5.0 micrograms ml-1 of thrombospondin cleaved thrombospondin to reduced 140 and 120 kDa fragments plus a reduced 25-kDa heparin-binding fragment. Infected erythrocytes bound to intact thrombospondin (3420 +/- 460 infected erythrocytes mm-2) and the carboxy-terminal fragment, yielding 120-140-kDa fragments on sulfhydryl reduction, but not to the 25-kDa fragment (144 +/- 104 infected erythrocytes mm-2 (mean +/- s.d., N = 4). Similar results were obtained with chymotrypsin and thrombin cleavage. When the anti-thrombospondin monoclonal antibody MA-I was added to immobilized thrombospondin prior to infected erythrocytes, adherence was inhibited by 99%. At the same concentration, MA-I inhibited adherence to C32 melanoma cells by only 35%. MA-I binds to a calcium-dependent structure at the C-terminal globular region of thrombospondin. Monoclonal antibody MA-II inhibited adherence to thrombospondin by 46%, while MA-III had no effect. These antibodies bind to the N-terminal globular region which includes the heparin-binding site and the segment connecting the two globular regions, respectively. The site(s) for infected erythrocyte binding on thrombospondin reside in the large, 140- or 120-kDa, proteolytic cleavage fragments, and not in the N-terminal heparin-binding region.

Publication types

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

MeSH terms

  • Animals
  • Antibodies, Protozoan / immunology
  • Cell Adhesion
  • Chromatography, Affinity
  • Erythrocytes / parasitology*
  • Heparin*
  • Humans
  • Membrane Glycoproteins / immunology
  • Membrane Glycoproteins / metabolism*
  • Plasmodium falciparum* / immunology
  • Thrombospondins
  • Tumor Cells, Cultured

Substances

  • Antibodies, Protozoan
  • Membrane Glycoproteins
  • Thrombospondins
  • Heparin