FIGURE 7.

Activation and dependence of apoptotic cell death on activity of the FGFR4 tyrosine kinase. A, activation of the FGFR4 kinase by KLB. 293 cells co-expressing constitutive KLB and FGFR4 induced by 300 ng/ml Tet overnight were maintained in serum-free medium for 6 h (33) and then exposed to 300 ng/ml of FGF19 for 10 min followed by immunoblot analysis of lysates with anti-phosphotyrosine (pTyr) and anti-FGFR4 antibodies. B and C, rescue of KLB-FGFR4-induced apoptosis and cell death by inhibition of tyrosine kinase activity. The FGFR kinase inhibitor 1-(2-amino-6-(3,5-dimethoxyphenyl) pyrido [2,3-d] pyrimidin-7-yl)-3-tert-butyl urea (341608; Calbiochem, San Diego, CA) at 1 μm was added during the 24-h induction of FGFR4 by 300 ng/ml Tet in cells expressing KLB followed by analysis of cell morphology (B) and apoptosis and cell death (C). FGF19 was present at 1 μg/ml.