PD-98059 (167869-21-8) is an inhibitor of mitogen-activated protein kinase kinase (MKK / MEK). Acts via binding to the inactivated form of MEK, preventing its phosphorylation by cRAF or MEK kinase (IC₅₀=2-7μM).^1,2 PD-98059 accelerates differentiation of RAW264.7 cells into osteoclast-like cells.³ Mimics BMP4 in supporting self renewal of embryonic stem cells.⁴

References/Citations
1) Alessi et al. (1995), PD 098059 is a specific inhibitor of the activation of mitogen-activated protein kinase kinase in vitro and in vivo; J. Biol. Chem., 270 27489
2) Dudley et al. (1995), A synthetic inhibitor of the mitogen-activated protein kinase cascade; Proc. Natl. Acad. Sci., 92 7686
3) Hotokezaka et al. (2002) U0126 and PD98059, specific inhibitors of MEK, accelerate differentiation of RAW264.7 cells into osteoclast-like cells; J. Biol. Chem., 277 47366
4) Xiaoxia et al. (2004) BMP4 supports self-renewal of embryonic stem cells by inhibiting mitogen-activated protein kinase pathways; Proc. Natl. Acad. Sci. USA 101 6027