Both NF-κB and c-Jun are activated by cytokines such as TNF-α and by stresses such as UV irradiation. A key step in the activation of NF-κB is the phosphorylation of its inhibitor, IκBα, by a ubiquitination-inducible multiprotein kinase complex (IκBα kinase). A central kinase in the c-Jun activation pathway is mitogen-activated protein kinase/ERK kinase kinase-1 (MEKK1). Here, we show that MEKK1 induces the site-specific phosphorylation of IκBα in vivo and, most strikingly, can directly activate the IκBα kinase complex in vitro. Thus, MEKK1 is a critical component of both the c- Jun and NF-κB stress response pathways. Since the IκBα kinase complex can be independently activated by ubiquitination or MEKK1-dependent phosphorylation, it may be an integrator of multiple signal transduction pathways leading to the activation of NF-κB.
ASJC Scopus subject areas
- General Biochemistry, Genetics and Molecular Biology