Several essential cellular functions are critically influenced by the Ras-Raf-MEK-ERK cascade, and pathological problems have been implicated with loss as well as gain of its activity. Therefore, there is a great demand for chemical probes that act as modulators of the cascade in order to correct medical problems associated with its malfunctions. Here we describe the use of the In-Cell Western assay, a fast and easy method for the detection of ERK activity. This method is useful for the screening of chemical libraries for compounds that modulate the intensity and duration of growth factor-induced MAPK activity. Examples are provided from a screen for MAPK modulators in Vichem Chemie Research�s Nested Chemical Library™.
