Analysis of Wnt7a-stimulated JNK activity and cJun phosphorylation in non-small cell lung cancer cells.

The cJun N-terminal kinases (JNKs) are activated in response to diverse growth factors and morphogens, including specific Wnt proteins. Genetic approaches have defined key roles for the JNKs as mediators of the Wnt-regulated epithelial cell programs including planar cell polarity and convergent extension. Moreover, our recent studies demonstrate that the JNK pathway is activated by Wnt-7a and Fzd9 to promote an epithelial differentiation program in lung cancer cells. In comparison to cell stresses such as hypertonicity or ultraviolet irradiation, which strongly activate JNKs, morphogens and growth factors induce activation of the pathway that is more modest and that may be difficult to assess by immunoblotting approaches with anti-phospho-JNK antibodies. We find that the tight binding of JNKs by their substrate, cJun, provides the basis for a simple and reliable assay for measuring JNK activity in cells stimulated with Wnt proteins and growth factors.