Novel interactions between urokinase and its receptor

O. Shliom, M. Huang, B. Sachais, A. Kou, J. W. Weisel, C. Nagaswami, T. Nassar, K. Bdeir, E. Hiss, S. Gawlak, S. Harris, A. Mazar, A. A R Higazi

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Urokinase-type plasminogen activator (uPA) binds to its receptor (uPAR) with a K(d) of about 1 nM. The catalytic activity of the complex is apparent at uPA concentrations close to K(d). Other functions of the complex, such as signal transduction, are apparent at much higher concentrations (35-60 nM). In the present study, we show that uPA and recombinant soluble uPAR (suPAR), at concentrations that exceed the K(d) and the theoretical saturation levels (10-80 nM), establish novel interactions that lead to a further increase in the activity of the single-chain uPA (scuPA)/suPAR and two-chain uPA (tcuPA)/suPAR complexes. Experiments performed using dynamic light scattering, gel filtration, and electron microscopy techniques indicate that suPAR forms dimers and oligomers. The three techniques provide evidence that the addition of an equimolar concentration of scuPA leads to the dissociation of these dimers and oligomers. Biacore data show that SuPAR dimers and oligomers bind scuPA with decreased affinity when compared with monomers. We postulate that uPAR is present in equilibrium between oligomer/dimer/monomer forms. The binding of uPA to suPAR dimers and oligomers occurs with lower affinity than the binding to monomer. These novel interactions regulate the activity of the resultant complexes and may be involved in uPA/uPAR mediated signal transduction.

Original languageEnglish (US)
Pages (from-to)24304-24312
Number of pages9
JournalJournal of Biological Chemistry
Volume275
Issue number32
DOIs
StatePublished - Aug 11 2000

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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