title: Negative feedback regulation of NF-κB-inducing kinase is proteasome-dependent but does not require cellular inhibitors of apoptosis.
abstract: Non-canonical NF-κB signaling is controlled by the precise regulation of NF-κB inducing kinase (NIK) stability. NIK is constitutively ubiquitylated by cellular inhibitor of apoptosis (cIAP) proteins 1 and 2, leading to its complete proteasomal degradation in resting cells. Following stimulation, cIAP-mediated ubiquitylation of NIK ceases and NIK is stabilized, allowing for inhibitor of κB kinase (IKK)α activation and non-canonical NF-κB signaling. Non-canonical NF-κB signaling is terminated by feedback phosphorylation of NIK by IKKα that promotes NIK degradation; however, the mechanism of active NIK protein turnover remains unknown. To address this question, we established a strategy to precisely distinguish between basal degradation of newly synthesized endogenous NIK and induced active NIK in stimulated cells. Using this approach, we found that IKKα-mediated degradation of signal-induced activated NIK occurs through the proteasome. To determine whether cIAP1 or cIAP2 play a role in active NIK turnover, we utilized a Smac mimetic (GT13072), which promotes degradation of these E3 ubiquitin ligases. As expected, GT13072 stabilized NIK in resting cells. However, loss of the cIAPs did not inhibit proteasome-dependent turnover of signal-induced NIK showing that unlike the basal regulatory mechanism, active NIK turnover is independent of cIAP1 and cIAP2. Our results therefore establish that the negative feedback control of IKKα-mediated NIK turnover occurs via a novel proteasome-dependent and cIAP-independent mechanism.
authors.affiliation: Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, United States.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Gray
authors.affiliation: Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, United States.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: McCorkell
authors.affiliation: PKPD Biosciences, 717 Constitution Drive, Suite 104, Exton, PA 19341, United States.
authors.forename: Srinivas K
authors.initials: SK
authors.lastname: Chunduru
authors.affiliation: Task Force for Global Health, 325 Swanton Way, Decatur, GA 30030, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: McKinlay
authors.affiliation: Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104, United States; Mari Lowe Center for Comparative Oncology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA 19104, United States. Electronic address: maym@vet.upenn.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: May
mesh_terms: D016475:3T3 Cells; D000818:Animals; D004789:Enzyme Activation; D025461:Feedback, Physiological / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000097782:NF-kappaB-Inducing Kinase
chemical_list: D051550:I-kappa B Kinase; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D000097782:NF-kappaB-Inducing Kinase
keywords: Bortezomib; NF-κB; NIK; Proteasome; Smac mimetic; cIAP