FIGURE 1.

Extracellular signal-regulated kinase (ERK) signaling cascade in AD: activation of receptor tyrosine kinase (RTK) or APOE receptor (APOER) leads to the activation of Ras/Raf protein which in turn phosphorylates and activates MEK. MEK phosphorylates and activates ERK. Once ERK is activated it activates numerous downstream targets both in the cytosol and nucleus. Activation of nuclear transcription factors by ERK leads to increased transcription of APP gene and hence increased APP protein production. Increased level of APP protein potentially leads to increased Aβ plaque formation. ERK is inactivated by de-phosphorylation via dual specificity phosphatases such as DUSP4.