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J Proteome Res. 2007 Mar;6(3):1016-28.

Proteomic identification of lynchpin urokinase plasminogen activator receptor protein interactions associated with epithelial cancer malignancy.

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Australian Proteome Analysis Facility Ltd and Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, 2109, NSW Australia.


Urokinase plasminogen activator (uPA) and its high affinity receptor (uPAR) play crucial proteolytic and non-proteolytic roles in cancer metastasis. In addition to promoting plasmin-mediated degradation of extracellular matrix barriers, cell surface engagement of uPA through uPAR binding results in the activation of a suite of diverse cellular signal transduction pathways. Because uPAR is bound to the plasma membrane through a glycosyl-phosphatidylinositol anchor, these signalling sequelae are thought to occur through the formation of multi-protein cell surface complexes involving uPAR. To further characterize uPAR-driven protein complexes, we co-immunoprecipitated uPAR from the human ovarian cancer cell line, OVCA 429, and employed sensitive proteomic methods to identify the uPAR-associated proteins. Using this strategy, we identified several known, as well as numerous novel, uPAR associating proteins, including the epithelial restricted integrin, alphavbeta6. Reverse immunoprecipitation using anti-beta6 integrin subunit monoclonal antibodies confirmed the co-purification of this protein with uPAR. Inhibition of uPAR and/or beta6 integrin subunit using neutralizing antibodies resulted in the inhibition of uPA-mediated ERK 1/2 phosphorylation and subsequent cell proliferation. These data suggest that the association of beta6 integrin (and possibly other lynchpin cancer regulatory proteins) with uPAR may be crucial in co-transmitting uPA signals that induce cell proliferation. Our findings support the notion that uPAR behaves as a lynchpin in promoting tumorigenesis by forming functionally active multiprotein complexes.

[Indexed for MEDLINE]

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