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Transformation-dependent activation of urokinase-type plasminogen-activator by a plasmin-independent mechanism - involvement of cell-surface membranes

Academic Article
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Overview

authors

  • Berkenpas, M. B.
  • Quigley, James

publication date

  • September 1991

journal

  • Proceedings of the National Academy of Sciences of the United States of America  Journal

abstract

  • Transformed cells produce elevated levels of the urokinase-type plasminogen activator (u-PA), which has been linked with the invasive or migratory phenotype of these cells. The u-PA is secreted and normally maintained in the inactive, single-chain form (scu-PA) and it has been assumed that natural activation occurs via a plasmin-mediated cleavage converting scu-PA to the active, two-chain form (tcu-PA). We now demonstrate that secreted scu-PA in Rous sarcoma virus-transformed chicken embryo fibroblast (RSVCEF) cultures is activated by an endogenous, plasmin-independent mechanism. Normal CEFs and CEFs infected with a temperature-sensitive RSV mutant and incubated at the nonpermissive temperature do not activate scu-PA. Conditioned medium harvested from plasmin-free cultures of RSVCEFs contains active tcu-PA as determined by two independent methods. The scu-PA is progressively converted with time in culture and requires the presence of intact cells or a plasma membrane-enriched fraction. When added to RSVCEF cultures, a synthetic peptide corresponding to residues 20-41 of the growth factor domain of chicken u-PA blocks the conversion to tcu-PA, and scu-PA accumulates in the cultures. These results suggest that scu-PA is secreted by cells, becomes bound to a u-PA receptor, and is proteolytically converted to active tcu-PA by a catalytic mechanism on the surface of RSV-transformed fibroblasts.

subject areas

  • Amino Acid Sequence
  • Animals
  • Avian Sarcoma Viruses
  • Cell Membrane
  • Cell Transformation, Neoplastic
  • Cells, Cultured
  • Chick Embryo
  • Enzyme Activation
  • Enzyme Precursors
  • Fibrinolysin
  • Immune Sera
  • Isoflurophate
  • Kinetics
  • Molecular Sequence Data
  • Peptides
  • Plasminogen Activators
  • Urokinase-Type Plasminogen Activator
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Identity

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.88.17.7768

PubMed ID

  • 1652763
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Additional Document Info

start page

  • 7768

end page

  • 7772

volume

  • 88

issue

  • 17

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