TI - Lipopolysaccharide triggered ERK1/2 PHOSphorylation in both cytoplasm and the nucleus . AB - The absence of pERK1/2 from the nucleus of ESAT-6 -stimulated RAW264.7 cells was specific for ESAT-6 treatment . To establish this , we stimulated the cells with the bacterial lipopolysaccharide ( LPS ) , which is a general activator of macrophages [39-47] . In the RAW264.7 cells stimulated with 0.1 mug/ml of LPS for the same time points as before , we observed time -dependent PHOSphorylation of ERK1/2 in both cytoplasm ( Fig 2A ) and nucleus ( Fig 2C ) . Next we wanted to know whether LPS can overcome the ESAT-6 imposed inhibition of PHOSphorylation of ERK1/2 in nucleus , for this RAW264.7 cells were co-stimulated for the same time points with LPS ( 01 mug/ml ) and ESAT-6 ( 5 mug/ml ) . In the presence of ESAT-6 , LPS caused only weak PHOSphorylation of ERK1/2 in nucleus ( Fig 2G ) compared to the LPS alone . Thus , ESAT-6 seemed to dampen the ERK1/2 signaling of the MAP kinase family by limiting the activation of ERK1/2 in the nucleus .