Inhibits NF-kappa-B activation by blocking the interaction of RIPK1 with its downstream effector NEMO/IKBKG. Forms a ternary complex with NFKB1 and MAP3K8 but appears to function upstream of MAP3K8 in the TLR4 signaling pathway that regulates MAP3K8 activation. Involved in activation of the MEK/ERK signaling pathway during innate immune response; this function seems to be stimulus- and cell type specific. Required for stability of MAP3K8. Involved in regulation of apoptosis in endothelial cells; promotes TEK agonist-stimulated endothelial survival. May act as transcriptional coactivator when translocated to the nucleus. Enhances CHUK-mediated NF-kappa-B activation involving NF-kappa-B p50-p65 and p50-c-Rel complexes. Interacts with STK11/LKB1, TNFAIP3, IKBKG, NFKB1, MAP3K8, TEK, RIPK1, CHUK, IKBKB and SMARCD1. Interacts with polyubiquitin (By similarity). Ubiquitously expressed in all tissues examined. In vitro phosphorylated by CHUK. Ubiquitinated; undergoes 'Lys-48'-linked polyubiquitination probably leading to constitutive proteasomal degradation which can be impaired by IKK-A/CHUK or IKBKB probably involving deubiquitination.