MEK Partner1

MEK partner-1 (MP-1) is a widely expressed scaffold that promotes the association of MEK with ERK, thereby facilitating ERK phosphorylation (Schaeffer et al. 1998). Through an interaction with p14, MP-1 is localised to endosomes (Fig. 5), and a reduction in expression of either MP-1 or p14 attenuates EGF-dependant ERK activation (Teis et al. 2002). Conversely, increasing expression of either MP-1 or p14 promotes activation of ERK by EGF. Endosome localisation is crucial for MP-1 activity, as mislocalisation abrogates the positive effect of MP-1 overexpression on ERK activation (Teis et al. 2002). MP-1 binds MEK1 constitutively, but associates with ERK transiently. Following phosphorylation by MEK1, ERK is released from MP-1, and it has been proposed that MP-1 can translate a weak MEK signal into sustained ERK activation (Sharma et al. 2005).

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