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© The Rockefeller University Press, 0021-9525/1997//529 $5.00
The Journal of Cell Biology, Volume 139, Number 2, , 1997 529-539

Article

Induction of Apoptosis after Expression of PYK2, a Tyrosine Kinase Structurally Related to Focal Adhesion Kinase



Wen-cheng Xiong and J. Thomas Parsons

Department of Microbiology, Health Science Center, University of Virginia, Charlottesville, Virginia 22908

Many cells (e.g., epithelial cells) require attachment to the extracellular matrix (ECM) to survive, a phenomenon known as anchorage-dependent cell survival. Disruption of the cell–ECM interactions mediated by the integrin receptors results in apoptosis. Focal adhesion kinase (FAK), a 125-kD protein tyrosine kinase activated by integrin engagement, appears to be involved in mediating cell attachment and survival. Proline-rich tyrosine kinase 2 (PYK2), also known as cellular adhesion kinase β (CAKβ) and related adhesion focal tyrosine kinase, is a second member of the FAK subfamily and is activated by an increase in intracellular calcium levels, or treatment with TNF{alpha} and UV light. However, the function of PYK2 remains largely unknown. In this study, we show that over-expression of PYK2, but not FAK, in rat and mouse fibroblasts leads to apoptotic cell death. Using a series of deletion mutants and chimeric fusion proteins of PYK2/FAK, we determined that the NH2-terminal domain and tyrosine kinase activity of PYK2 were required for the efficient induction of apoptosis. Furthermore, the apoptosis mediated by PYK2 could be suppressed by over-expressing catalytically active v-Src, c-Src, phosphatidylinositol-3-kinase, or Akt/protein kinase B. In addition, it could also be suppressed by overexpressing an ICE or ICE-like proteinase inhibitor, crmA, but not Bcl2. Collectively, our results suggest that PYK2 and FAK, albeit highly homologous in primary structure, appear to have different functions; FAK is required for cell survival, whereas PYK2 induces apoptosis in fibroblasts.

Abbreviations used in this paper: ECM, extracellular matrix; FAK, focal adhesion kinase; FRNK, FAK-related nonkinase; FAT, focal adhesion targeting domain; GST, glutathione-S-transferase; PI3 kinase, phosphatidylinositol-3-kinase.

Address all correspondence to J. Thomas Parsons, Department of Microbiology, Box 441, Health Science Center, University of Virginia, Charlottesville, VA 22908. Tel.: (804) 924-5395. Fax: (804) 982-1071. E-mail: jtp{at}virginia.edu


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