title: Inositol hexakisphosphate (IP6) generated by IP5K mediates cullin-COP9 signalosome interactions and CRL function.
abstract: The family of cullin-RING E3 Ligases (CRLs) and the constitutive photomorphogenesis 9 (COP9) signalosome (CSN) form dynamic complexes that mediate ubiquitylation of 20% of the proteome, yet regulation of their assembly/disassembly remains poorly understood. Inositol polyphosphates are highly conserved signaling molecules implicated in diverse cellular processes. We now report that inositol hexakisphosphate (IP6) is a major physiologic determinant of the CRL-CSN interface, which includes a hitherto unidentified electrostatic interaction between the N-terminal acidic tail of CSN subunit 2 (CSN2) and a conserved basic canyon on cullins. IP6, with an EC50 of 20 nM, acts as an intermolecular "glue," increasing cullin-CSN2 binding affinity by 30-fold, thereby promoting assembly of the inactive CRL-CSN complexes. The IP6 synthase, Ins(1,3,4,5,6)P5 2-kinase (IPPK/IP5K) binds to cullins. Depleting IP5K increases the percentage of neddylated, active Cul1 and Cul4A, and decreases levels of the Cul1/4A substrates p27 and p21. Besides dysregulating CRL-mediated cell proliferation and UV-induced apoptosis, IP5K depletion potentiates by 28-fold the cytotoxic effect of the neddylation inhibitor MLN4924. Thus, IP5K and IP6 are evolutionarily conserved components of the CRL-CSN system and are potential targets for cancer therapy in conjunction with MLN4924.
authors.affiliation: The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205;
authors.forename: Paul C
authors.initials: PC
authors.lastname: Scherer
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China;
authors.forename: Yan
authors.initials: Y
authors.lastname: Ding
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China;
authors.forename: Zhiqing
authors.initials: Z
authors.lastname: Liu
authors.affiliation: The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205;
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: Howard Hughes Medical Institute, Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195;
authors.forename: Haibin
authors.initials: H
authors.lastname: Mao
authors.affiliation: Department of Pharmacology and Molecular Science, Lieber Institute for Brain Development, The Johns Hopkins University School of Medicine, Baltimore, MD 21205;
authors.forename: James C
authors.initials: JC
authors.lastname: Barrow
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06511;
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
authors.affiliation: Howard Hughes Medical Institute, Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195;
authors.forename: Ning
authors.initials: N
authors.lastname: Zheng
authors.affiliation: The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06511; Department of Psychiatry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205 ssnyder@jhmi.edu raofeng@nibs.ac.cn.
authors.forename: Solomon H
authors.initials: SH
authors.lastname: Snyder
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China; ssnyder@jhmi.edu raofeng@nibs.ac.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D000075686:COP9 Signalosome Complex; D020134:Catalytic Domain; D044842:Cullin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D010833:Phytic Acid / Q000096:biosynthesis*; D054730:Protein Interaction Domains and Motifs; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053722:Receptors, Interleukin-17
chemical_list: D000075686:COP9 Signalosome Complex; D044842:Cullin Proteins; D046912:Multiprotein Complexes; D010447:Peptide Hydrolases; D017856:Phosphotransferases (Phosphate Group Acceptor); D010833:Phytic Acid; D044767:Ubiquitin-Protein Ligases; C408922:IL17RB protein, human; D053722:Receptors, Interleukin-17; C584471:CULL-RING ligase, human; C099438:inositol hexakisphosphate kinase
keywords: COP9 signalosome; CRL; IP5K; cullin RING E3 ligases; inositol hexakisphosphate