title: Induction of apoptosis after expression of PYK2, a tyrosine kinase structurally related to focal adhesion kinase.
abstract: 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 beta (CAKbeta) 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 TNFalpha 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.
authors.affiliation: Department of Microbiology, Health Science Center, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: W
authors.initials: W
authors.lastname: Xiong
authors.forename: J T
authors.initials: JT
authors.lastname: Parsons
mesh_terms: D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D020170:Caspase 1; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000737:chemistry; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000096:biosynthesis; D005347:Fibroblasts; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D017353:Gene Deletion; D016391:Genes, src; D051379:Mice; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000737:chemistry; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis; D015843:Serpins / Q000096:biosynthesis; D014162:Transfection; D014764:Viral Proteins
chemical_list: D015815:Cell Adhesion Molecules; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D015843:Serpins; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; C496052:Ptk2 protein, rat; C496053:Ptk2b protein, mouse; C496054:Ptk2b protein, rat; D003546:Cysteine Endopeptidases; D020170:Caspase 1