FIGURE 5.

Phosphatase-mediated regulation of the MAPK signaling response. The influence of individual phosphatases in sensitizing the ERK output was monitored in silico by analyzing ligand dose versus peak phospho-ERK (ppERK) levels within the first 30 min of activation. This analysis was performed either in normal cells (Normal) or in cells where the indicated phosphatase was depleted from the system. In each case, the -fold change in ligand concentration required to increase ERK phosphorylation from 10 to 90% of its maximal value is also given (F). These values confirm that the ERK response remains proportional under all of these conditions.