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Endostatin associates with integrin alpha5beta1 and caveolin-1, and activates Src via a tyrosyl phosphatase-dependent

Sara A Wickström1, Kari Alitalo, Jorma Keski-Oja

  • 1Department of Pathology, Haartman Institute and University of Helsinki, Helsinki, Finland.

Cancer Research
|October 3, 2002
PubMed

Insights

Endostatin, a collagen fragment, inhibits tumor growth by disrupting endothelial cell interactions with the extracellular matrix. It targets alpha5beta1 integrin and caveolin-1, affecting cell migration and fibronectin deposition.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Endostatin, derived from collagen XVIII, is a known inhibitor of angiogenesis and tumor growth.
  • Understanding the molecular mechanisms of endostatin's action is crucial for developing targeted cancer therapies.

Purpose of the Study:

  • To investigate the interactions of recombinant human endostatin with endothelial cell surface proteins and its downstream signaling pathways.
  • To elucidate the mechanisms by which endostatin affects cell adhesion, matrix deposition, and migration.

Main Methods:

  • Cultured human microvascular endothelial cells were treated with recombinant endostatin.
  • Analysis of plasma membrane-extracellular matrix interactions, including integrin clustering and colocalization studies.
  • Coimmunoprecipitation assays to identify interacting proteins.
  • Western blotting and kinase assays to assess Src family kinase activation.
  • Wounding assays to evaluate cell migration and fibronectin deposition.

Main Results:

  • Endostatin induced clustering of alpha5beta1 integrin and colocalization with caveolin-1 at the cell surface.
  • Endostatin coimmunoprecipitated with alpha5beta1 integrin and caveolin-1.
  • Treatment activated caveolin-associated Src family kinases in a phosphatase-dependent manner.
  • Endostatin promoted the disassembly of actin stress fibers and focal adhesions via Src and tyrosyl phosphatase activation.
  • Cells lacking focal adhesions showed impaired fibronectin deposition and reduced migration.

Conclusions:

  • Recombinant endostatin directly interacts with alpha5beta1 integrin and caveolin-1 on endothelial cells.
  • The anti-migratory effects of endostatin are mediated by phosphatase-dependent Src activation, leading to impaired cell-matrix interactions and reduced cell motility.

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