IndraLab

"As shown in Figure 5A, a constitutively active (CA) mitogen-activated protein kinase 1 (MEK1) (24) induced the Ser-380 phosphorylation of WT RSK1, but not CTKm, indicating the classical ERK-mediated activation of RSK1 in a CTK-dependent manner."

"Several lines of evidence indicate that the mapkap-k1 isoforms are also activated by mapks in vivo via the ras-dependent protein kinase cascade that is triggered by growth factors or tumor-promoting phorbol esters, such as phorbol 12-myristate 13-acetate (pma). here we identify six sites in mapkap-k1a that become phosphorylated in transfected cos-1 cells. The inactive form of mapkap-k1a in unstimulated cells is partially phosphorylated at ser222 and ser733. Stimulation with phorbol 12-myristate 13-acetate induces the phosphorylation of thr360, ser364, thr574, and ser381 and increases the phosphorylation of ser222 and ser733."