Effects of the NIK aly mutation on NF-kappa B activation by the Epstein-Barr virus latent infection membrane protein, lymphotoxin beta receptor, and CD40

Homozygosity for the aly point mutation in NF-kappaB-inducing kinase (NIK) results in alymphoplasia in mice, a phenotype similar to that of homozygosi ty for deletion of the lymphotoxin beta receptor (LT betaR), We now find th at NF-kappaB activation by Epstein-Barr virus latent membrane protein 1 (LM P1) or by an LMP1 transmembrane domain chimera with the LT betaR signaling domain in human embryonic kidney 293 cells is selectively inhibited by a wi ld type dominant negative NIK comprised of amino acids 624-947 (DN-NIK) and not by aly DN-NIK. In contrast, LMP1/CD40 is inhibited by both wild type ( wt) and aly DN-NIK. LMP1, an LMP1 transmembrane domain chimera with the LT betaR signaling domain, and LMP1/CD40 activate NF-kappaB in wt or aly murin e embryo fibroblasts, Although wt and aly NIK do not differ in their in vit ro binding to tumor necrosis factor receptor-associated factor 1, 2, 3, or 6 or in their in vivo association with tumor necrosis factor receptor-assoc iated factor 2 and differ marginally in their very poor binding to I kappaB kinase beta (IKK beta), only wt NIK is able to bind to IKK alpha. These da ta are compatible with a model in which activation of NF-kappaB by LMP1 and LT betaR is mediated by an interaction of NIK or a NIK-like kinase with IK K alpha that is abrogated by the aly mutation. On the other hand, CD40 medi ates NF-kappaB activation through a kinase that inter acts with a different component of the IKK complex.