Chronic activation of ERK and neurodegenerative diseases.

The extracellular-signal regulated kinases 1/2 (ERK or ERKs) are involved in the regulation of important neuronal functions, including neuronal plasticity in normal and pathological conditions. We present findings that support the notion that the kinetics and localization of ERK are intrinsically linked, in that the duration of ERK activation dictates its subcellular compartmentalization and/or trafficking. The latter, in turn, dictates whether ERK-expressing cells would enter a program of cell death, survival or differentiation. We summarize experimental data showing that chronic activation of ERK plays a role in the mechanisms that trigger neurodegeneration. We also discuss how MKPs, members of the subclass of dual specificity phosphatases, might be the link between ERK kinetics and its subcellular localization. Copyright 2003 Wiley Periodicals, Inc.