title: Riboflavin kinase couples TNF receptor 1 to NADPH oxidase.
abstract: Reactive oxygen species (ROS) produced by NADPH oxidase function as defence and signalling molecules related to innate immunity and various cellular responses. The activation of NADPH oxidase in response to plasma membrane receptor activation depends on the phosphorylation of cytoplasmic oxidase subunits, their translocation to membranes and the assembly of all NADPH oxidase components. Tumour necrosis factor (TNF) is a prominent stimulus of ROS production, but the molecular mechanisms by which TNF activates NADPH oxidase are poorly understood. Here we identify riboflavin kinase (RFK, formerly known as flavokinase) as a previously unrecognized TNF-receptor-1 (TNFR1)-binding protein that physically and functionally couples TNFR1 to NADPH oxidase. In mouse and human cells, RFK binds to both the TNFR1-death domain and to p22(phox), the common subunit of NADPH oxidase isoforms. RFK-mediated bridging of TNFR1 and p22(phox) is a prerequisite for TNF-induced but not for Toll-like-receptor-induced ROS production. Exogenous flavin mononucleotide or FAD was able to substitute fully for TNF stimulation of NADPH oxidase in RFK-deficient cells. RFK is rate-limiting in the synthesis of FAD, an essential prosthetic group of NADPH oxidase. The results suggest that TNF, through the activation of RFK, enhances the incorporation of FAD in NADPH oxidase enzymes, a critical step for the assembly and activation of NADPH oxidase.
authors.affiliation: Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Yazdanpanah
authors.forename: Katja
authors.initials: K
authors.lastname: Wiegmann
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tchikov
authors.forename: Oleg
authors.initials: O
authors.lastname: Krut
authors.forename: Carola
authors.initials: C
authors.lastname: Pongratz
authors.forename: Michael
authors.initials: M
authors.lastname: Schramm
authors.forename: Andre
authors.initials: A
authors.lastname: Kleinridders
authors.forename: Thomas
authors.initials: T
authors.lastname: Wunderlich
authors.forename: Hamid
authors.initials: H
authors.lastname: Kashkar
authors.forename: Olaf
authors.initials: O
authors.lastname: Utermöhlen
authors.forename: Jens C
authors.initials: JC
authors.lastname: Brüning
authors.forename: Stefan
authors.initials: S
authors.lastname: Schütze
authors.forename: Martin
authors.initials: M
authors.lastname: Krönke
mesh_terms: D000818:Animals; D002460:Cell Line; D003573:Cytochrome b Group / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts; D005486:Flavin Mononucleotide / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000096:biosynthesis / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000737:chemistry / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003573:Cytochrome b Group; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D047888:Receptors, Tumor Necrosis Factor, Type I; D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide; D009247:NADH, NADPH Oxidoreductases; C488842:Cybb protein, mouse; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C086986:CYBA protein, human; C515614:Cyba protein, mouse; D017853:Phosphotransferases (Alcohol Group Acceptor); C022532:riboflavin kinase