The duration, magnitude and compartmentalization of ERK MAP kinase activity: mechanisms for providing signaling specificity.

ERK MAP kinase signaling plays a pivotal role in diverse cellular functions, including cell proliferation, differentiation, migration and survival. One of the central questions concerning this signaling is how activation of the same protein kinase, ERK, elicits distinct cellular outcomes. Recent progress has demonstrated that differences in the duration, magnitude and subcellular compartmentalization of ERK activity generate variations in signaling output that regulate cell fate decisions. Furthermore, several molecules have been identified as spatial, temporal or strength-controlling regulators of ERK activity. Signaling by various extracellular stimuli thus could be modulated by these regulators to give qualitative and quantitative differences in ERK activity, which are then interpreted by the cells as determinants for appropriate responses.