BIX 02189S1531

BIX02189 blocks MEK5 and ERK5 catalytic activity with IC50 values of 1.5 nM and 59 nM, respectively. They are more potent than the effect caused by BIX02188 with IC50 values of 4.3 nM and 810 nM, respectively. BIX02189 shows inhibitory activity against CSF1R (FMS) with IC50 of 46 nM but displays no activity against related kinases MEK1, MEK2, ERK1, p38α, JNK2, EGFR, and STK16 with IC50 values of >3.7 μM. Pretreatment with BIX02189 inhibits sorbitol-induced phosphorylation of ERK5 in HeLa cells in a dose dependent manner, and displays no inhibitory activity against the phosphorylation of ERK1/2, p38, and JNK1/2 MAPKs. Treatment with only BIX02189 for 24 hours in HeLa or HEK293 cells does not show any cytotoxic effect. BIX02189 inhibits MEK5/ERK5/MEF2C-driven luciferase expression in HeLa and HEK293 cells with IC50 values of 0.53 μM and 0.26 μM, respectively. This is a more significant than the effect caused by BIX02188. ^[1] BIX02189 inhibits the activation of ERK5, and suppresses C-terminus of Hsc70-interacting protein (CHIP) mediated p53 ubiquitination, leading to the reverse of the protective effect caused by laminar flow (L-flow) in human umbilical vein endothelial cells (HUVECs) exposed to 15d-PGJ2. ^[2] BIX02189 (10 uM) inhibits ERK5 phosphorylation, and reduces myocyte enhancer factor 2 (MEF2) transcriptional activity in neonatal rat cardiomyocytes (NRCMs) stimulated by isoproterenol. BIX02189 enhances the sorbitol induced apoptosis in NRCMs, confirming the protective role of ERK5 in cardiomyocytes. ^[3]