• Open Access

Activation of focal adhesion kinase in human lung cancer cells involves multiple and potentially parallel signaling events

Authors

  • Nishit K. Mukhopadhyay,

    1. Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
    2. Division of Urology/Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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  • Gavin J. Gordon,

    1. Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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  • Chang-Jie Chen,

    1. Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Masschusetts, USA
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  • Raphael Bueno,

    1. Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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  • David J. Sugarbaker,

    1. Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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  • Michael T. Jaklitsch

    Corresponding author
    1. Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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*Michael T JAKLITSCH, Division of Thoracic Surgery, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston MA 02115, USA. Tel.: 617-732-6988, Fax: 617-730-2898 E-mail: mjaklitsch@partners.org

Abstract

Integrins are adhesion receptors that transmit signals bidirectionally across the plasma membrane. In our previous report we have shown that the squamous lung cancer cell line, Calu-1, binds to collagen type IV (Coll IV) through β1-integrin and results in phosphorylation of focal adhesion kinase (FAK) (Ann Thorac Surg 2004; 78:450-7). Considering the critical role of FAK in cell migration, proliferation, and survival, here we investigated potential mechanisms of its activation and regulation in Calu-1 cells. We observed the phosphorylation of Tyr397 of FAK (the autophosphorylation site of FAK) and paxillin, the immediate downstream substrate of FAK following the adhesion of Calu-1 cells to Coll IV. FAK remains phosphorylated during proliferation either on Coll IV or on uncoated plates for 72 h, as determined by peroxivanadate treatment. Exposure of Calu-1 cells with 60 μM genistein, reduces FAK phosphorylation (7.6 fold) and cell proliferation. Extracellular signal regulated kinases (ERKs) were also phosphorylated after Coll IV attachment. Disruption of Calu-1 cell cytoskeleton integrity by 1–5 μM Cytochalasin D resulted in the inhibition of cell adhesion (50% to 75%, p<0.19–6.6×10-7) and ERKs phosphorylation (2 fold) without any effect on FAK phosphorylation. Protein Kinase C inhibitor, Calphostin C at 100 and 250 nM concentrations did not block Coll IV induced FAK phosphorylation, but activated the ERKs in a dose dependent manner. β1-integrin is essential for Coll IV induced FAK activation, but it is not physically associated with FAK as determined by immunodetection assay. Collectively, this report defines the existence of multiple and potentially parallel Coll IV/β1-integrin mediated signaling events in Calu-1 cells, which involve FAK, ERKs, and PKC.

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