Establishment of MDCK cells expressing an active Ras or BRaf protein and a FRET biosensor for ERK activity.

<p>(A) A scheme of the Ras-Raf-MEK-ERK pathway and the mode of action of the intramolecular FRET biosensor, EKAREV-NLS. DUSPs, dual-specificity phosphatases; PSPs, protein serine/threonine phosphatases. (B) Parental MDCK cells were stably-transfected with an expression vector for EKAREV-NLS. The transfected cells were then further transfected with the pPBbsr2-lox-tdTomato-oncogene. After the introduction of ER^T2CreER^T2, the oncogenes were induced by 4OHT. (C) The MDCK-EKAREV-NLS-floxed-tdTomato-oncogene, the name of which is depicted in the first row, was cultured in the presence or absence of 1 μM 4OHT and analyzed by Western blotting with the antibodies listed on the left of each panel.