Protein phosphatase 5 as a negative key regulator of Raf-1 activation.

Growth factors such as the epidermal growth factor cause sequential activation of receptor tyrosine kinases, adaptor molecules and the Raf-MEK-ERK pathway. The kinetics and intensity of these signals are dependent on the balance between phosphorylation and dephosphorylation of these molecules by numerous kinases and phosphatases, respectively. Recently, protein phosphatase 5 has been characterized as a key dephosphorylation regulator of Raf-1 activation in growth factor-mediated signaling, leading to attenuation of the MEK-ERK cascade.