title: Nuclear factor-κB-inducing kinase (NIK) contains an amino-terminal inhibitor of apoptosis (IAP)-binding motif (IBM) that potentiates NIK degradation by cellular IAP1 (c-IAP1).
abstract: Activation of the noncanonical NF-κB pathway hinges on the stability of the NF-κB-inducing kinase (NIK), which is kept at low levels basally by a protein complex consisting of the E3 ubiquitin ligases cellular inhibitor of apoptosis 1 and 2 (c-IAP1/2) proteins and the tumor necrosis factor receptor-associated factors 2 and 3 (TRAF2/3). NIK is brought into close proximity to the c-IAPs through a TRAF2-TRAF3 bridge where TRAF2 recruits c-IAP1/2 and TRAF3 binds to NIK. However, it is not clear how the c-IAPs specifically recognize and ubiquitylate NIK in the complex. We have identified an IAP-binding motif (IBM) at the amino terminus of NIK. IBMs are utilized by a number of proapoptotic proteins to antagonize IAP function. Here, we utilize mutational studies to demonstrate that wild-type NIK is destabilized in the presence of c-IAP1, whereas the NIK IBM mutant is stable. NIK interacts with the second baculovirus IAP repeat (BIR2) domain of c-IAP1 via the IBM, and this interaction, in turn, provides substrate recognition for c-IAP1 mediated ubiquitylation and degradation of NIK. Furthermore, in the presence of the NIK IBM mutant, we observed an elevated processing of p100 to p52 followed by increased expression of NF-κB target genes. Together, these findings reveal the novel identification and function of the NIK IBM, which promotes c-IAP1-dependent ubiquitylation of NIK, resulting in optimal NIK turnover to ensure that noncanonical NF-κB signaling is off in the absence of an activating signal.
authors.affiliation: Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, and.
authors.forename: Sunhee
authors.initials: S
authors.lastname: Lee
authors.affiliation: Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, and.
authors.forename: Madhavi
authors.initials: M
authors.lastname: Challa-Malladi
authors.affiliation: Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, and; Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park, Smithville, Texas 78957.
authors.forename: Shawn B
authors.initials: SB
authors.lastname: Bratton
authors.affiliation: Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, and; Center for Molecular and Cellular Toxicology in the Division of Pharmacology and Toxicology, College of Pharmacy and The University of Texas at Austin, Austin, Texas 78712. Electronic address: Cww@austin.utexas.edu.
authors.forename: Casey W
authors.initials: CW
authors.lastname: Wright
mesh_terms: D001667:Binding, Competitive; D004795:Enzyme Stability; D057809:HEK293 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry / Q000502:physiology*; D054730:Protein Interaction Domains and Motifs; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D059748:Proteolysis; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination; D000097782:NF-kappaB-Inducing Kinase
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D017346:Protein Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; D000097782:NF-kappaB-Inducing Kinase; C494833:BIRC2 protein, human
keywords: E3 Ubiquitin Ligase; IBM; NF-kB Transcription Factor; NIK; TNF Receptor-associated Factor (TRAF); Ubiquitylation (Ubiquitination); X-linked Inhibitor Of Apoptosis Protein (XIAP); c-IAP