1
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Noireterre A, Stutz F. Cdc48/p97 segregase: Spotlight on DNA-protein crosslinks. DNA Repair (Amst) 2024; 139:103691. [PMID: 38744091 DOI: 10.1016/j.dnarep.2024.103691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/30/2024] [Accepted: 05/01/2024] [Indexed: 05/16/2024]
Abstract
The ATP-dependent molecular chaperone Cdc48 (in yeast) and its human counterpart p97 (also known as VCP), are essential for a variety of cellular processes, including the removal of DNA-protein crosslinks (DPCs) from the DNA. Growing evidence demonstrates in the last years that Cdc48/p97 is pivotal in targeting ubiquitinated and SUMOylated substrates on chromatin, thereby supporting the DNA damage response. Along with its cofactors, notably Ufd1-Npl4, Cdc48/p97 has emerged as a central player in the unfolding and processing of DPCs. This review introduces the detailed structure, mechanism and cellular functions of Cdc48/p97 with an emphasis on the current knowledge of DNA-protein crosslink repair pathways across several organisms. The review concludes by discussing the potential therapeutic relevance of targeting p97 in DPC repair.
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Affiliation(s)
- Audrey Noireterre
- Department of Molecular and Cellular Biology, University of Geneva, Geneva 4 1211, Switzerland
| | - Françoise Stutz
- Department of Molecular and Cellular Biology, University of Geneva, Geneva 4 1211, Switzerland.
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2
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Saffert P, Enenkel C, Wendler P. Structure and Function of p97 and Pex1/6 Type II AAA+ Complexes. Front Mol Biosci 2017; 4:33. [PMID: 28611990 PMCID: PMC5447069 DOI: 10.3389/fmolb.2017.00033] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 05/05/2017] [Indexed: 12/16/2022] Open
Abstract
Protein complexes of the Type II AAA+ (ATPases associated with diverse cellular activities) family are typically hexamers of 80–150 kDa protomers that harbor two AAA+ ATPase domains. They form double ring assemblies flanked by associated domains, which can be N-terminal, intercalated or C-terminal to the ATPase domains. Most prominent members of this family include NSF (N-ethyl-maleimide sensitive factor), p97/VCP (valosin-containing protein), the Pex1/Pex6 complex and Hsp104 in eukaryotes and ClpB in bacteria. Tremendous efforts have been undertaken to understand the conformational dynamics of protein remodeling type II AAA+ complexes. A uniform mode of action has not been derived from these works. This review focuses on p97/VCP and the Pex1/6 complex, which both structurally remodel ubiquitinated substrate proteins. P97/VCP plays a role in many processes, including ER- associated protein degradation, and the Pex1/Pex6 complex dislocates and recycles the transport receptor Pex5 from the peroxisomal membrane during peroxisomal protein import. We give an introduction into existing knowledge about the biochemical and cellular activities of the complexes before discussing structural information. We particularly emphasize recent electron microscopy structures of the two AAA+ complexes and summarize their structural differences.
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Affiliation(s)
- Paul Saffert
- Department of Biochemistry, Institute of Biochemistry and Biology, University of PotsdamPotsdam, Germany
| | - Cordula Enenkel
- Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - Petra Wendler
- Department of Biochemistry, Institute of Biochemistry and Biology, University of PotsdamPotsdam, Germany
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3
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Cervi G, Magnaghi P, Asa D, Avanzi N, Badari A, Borghi D, Caruso M, Cirla A, Cozzi L, Felder E, Galvani A, Gasparri F, Lomolino A, Magnuson S, Malgesini B, Motto I, Pasi M, Rizzi S, Salom B, Sorrentino G, Troiani S, Valsasina B, O’Brien T, Isacchi A, Donati D, D’Alessio R. Discovery of 2-(Cyclohexylmethylamino)pyrimidines as a New Class of Reversible Valosine Containing Protein Inhibitors. J Med Chem 2014; 57:10443-54. [DOI: 10.1021/jm501313x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Giovanni Cervi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Paola Magnaghi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Daniela Asa
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Nilla Avanzi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Alessandra Badari
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Daniela Borghi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Michele Caruso
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Alessandra Cirla
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Liviana Cozzi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Eduard Felder
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Arturo Galvani
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Fabio Gasparri
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Antonio Lomolino
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Steven Magnuson
- Genentech Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Beatrice Malgesini
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Ilaria Motto
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Maurizio Pasi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Simona Rizzi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Barbara Salom
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Graziella Sorrentino
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Sonia Troiani
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Barbara Valsasina
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Thomas O’Brien
- Genentech Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Antonella Isacchi
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Daniele Donati
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
| | - Roberto D’Alessio
- Oncology, Nerviano Medical Sciences S.r.l., Viale Pasteur 10, 20014 Nerviano, Milan, Italy
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4
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Structural and biochemical properties of an extreme 'salt-loving' proteasome activating nucleotidase from the archaeon Haloferax volcanii. Extremophiles 2013; 18:283-93. [PMID: 24343376 DOI: 10.1007/s00792-013-0615-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/21/2013] [Indexed: 12/13/2022]
Abstract
In eukaryotes, the 26S proteasome degrades ubiquitinylated proteins in an ATP-dependent manner. Archaea mediate a form of post-translational modification of proteins termed sampylation that resembles ubiquitinylation. Sampylation was identified in Haloferax volcanii, a moderate halophilic archaeon that synthesizes homologs of 26S proteasome subunits including 20S core particles and regulatory particle triple-A ATPases (Rpt)-like proteasome-associated nucleotidases (PAN-A/1 and PAN-B/2). To determine whether sampylated proteins associate with the Rpt subunit homologs, PAN-A/1 was purified to homogeneity from Hfx. volcanii and analyzed for its subunit stoichiometry, nucleotide-hydrolyzing activity and binding to sampylated protein targets. PAN-A/1 was found to be associated as a dodecamer (630 kDa) with a configuration in TEM suggesting a complex of two stacked hexameric rings. PAN-A/1 had high affinity for ATP (K m of ~0.44 mM) and hydrolyzed this nucleotide with a specific activity of 0.33 ± 0.1 μmol Pi/h per mg protein and maximum at 42 °C. PAN-A1 was stabilized by 2 M salt with a decrease in activity at lower concentrations of salt that correlated with dissociation of the dodecamer into trimers to monomers. Binding of PAN-A/1 to a sampylated protein was demonstrated by modification of a far Western blotting technique (derived from the standard Western blot method to detect protein-protein interaction in vitro) for halophilic proteins. Overall, our results support a model in which sampylated proteins associate with the PAN-A/1 AAA+ ATPase in proteasome-mediated proteolysis and/or protein remodeling and provide a method for assay of halophilic protein-protein interactions.
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5
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Covalent and allosteric inhibitors of the ATPase VCP/p97 induce cancer cell death. Nat Chem Biol 2013; 9:548-56. [PMID: 23892893 DOI: 10.1038/nchembio.1313] [Citation(s) in RCA: 275] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 07/02/2013] [Indexed: 12/21/2022]
Abstract
VCP (also known as p97 or Cdc48p in yeast) is an AAA(+) ATPase regulating endoplasmic reticulum-associated degradation. After high-throughput screening, we developed compounds that inhibit VCP via different mechanisms, including covalent modification of an active site cysteine and a new allosteric mechanism. Using photoaffinity labeling, structural analysis and mutagenesis, we mapped the binding site of allosteric inhibitors to a region spanning the D1 and D2 domains of adjacent protomers encompassing elements important for nucleotide-state sensing and ATP hydrolysis. These compounds induced an increased affinity for nucleotides. Interference with nucleotide turnover in individual subunits and distortion of interprotomer communication cooperated to impair VCP enzymatic activity. Chemical expansion of this allosteric class identified NMS-873, the most potent and specific VCP inhibitor described to date, which activated the unfolded protein response, interfered with autophagy and induced cancer cell death. The consistent pattern of cancer cell killing by covalent and allosteric inhibitors provided critical validation of VCP as a cancer target.
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6
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Polucci P, Magnaghi P, Angiolini M, Asa D, Avanzi N, Badari A, Bertrand J, Casale E, Cauteruccio S, Cirla A, Cozzi L, Galvani A, Jackson PK, Liu Y, Magnuson S, Malgesini B, Nuvoloni S, Orrenius C, Sirtori FR, Riceputi L, Rizzi S, Trucchi B, O'Brien T, Isacchi A, Donati D, D'Alessio R. Alkylsulfanyl-1,2,4-triazoles, a new class of allosteric valosine containing protein inhibitors. Synthesis and structure-activity relationships. J Med Chem 2013; 56:437-50. [PMID: 23245311 DOI: 10.1021/jm3013213] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Valosine containing protein (VCP), also known as p97, is a member of AAA ATPase family that is involved in several biological processes and plays a central role in the ubiquitin-mediated degradation of misfolded proteins. VCP is an ubiquitously expressed, highly abundant protein and has been found overexpressed in many tumor types, sometimes associated with poor prognosis. In this respect, VCP has recently received a great deal of attention as a potential new target for cancer therapy. In this paper, the discovery and structure-activity relationships of alkylsulfanyl-1,2,4-triazoles, a new class of potent, allosteric VCP inhibitors, are described. Medicinal chemistry manipulation of compound 1, identified via HTS, led to the discovery of potent and selective inhibitors with submicromolar activity in cells and clear mechanism of action at consistent doses. This represents a first step toward a new class of potential anticancer agents.
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Affiliation(s)
- Paolo Polucci
- Nerviano Medical Sciences S.r.l., Oncology, Viale Pasteur 10, 20014 Nerviano (MI), Italy
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7
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Hensel A, Beck S, El Magraoui F, Platta HW, Girzalsky W, Erdmann R. Cysteine-dependent ubiquitination of Pex18p is linked to cargo translocation across the peroxisomal membrane. J Biol Chem 2011; 286:43495-505. [PMID: 22021076 DOI: 10.1074/jbc.m111.286104] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The peroxisomal matrix protein import is facilitated by cycling receptor molecules that shuttle between the cytosol and the peroxisomal membrane. In the yeast Saccharomyces cerevisiae, the import of proteins harboring a peroxisomal targeting signal of type II (PTS2) is mediated by the receptor Pex7p and its co-receptor Pex18p. Here we demonstrate that Pex18p undergoes two kinds of ubiquitin modifications. One of these ubiquitination events depends on lysines 13 and 20 and forces rapid Pex18p turnover by proteasomal degradation. A cysteine residue near the extreme Pex18p amino-terminus is required for the second type of ubiquitination. It turned out that this cysteine residue at position 6 is essential for the function of Pex18p in peroxisomal protein import but does not contribute to receptor-cargo association and binding to the peroxisomal import apparatus. However, in contrast to the wild-type protein, cysteine 6-mutated Pex18p is arrested in a membrane-protected state, whereas Pex7p is accessible in a protease protection assay. This finding indicates that Pex18p export is linked to cargo translocation, which supports the idea of an export-driven import of proteins into peroxisomes.
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Affiliation(s)
- Astrid Hensel
- Abteilung für Systembiochemie, Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany
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8
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Braun RJ, Zischka H. Mechanisms of Cdc48/VCP-mediated cell death — from yeast apoptosis to human disease. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1418-35. [DOI: 10.1016/j.bbamcr.2008.01.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Accepted: 01/16/2008] [Indexed: 10/22/2022]
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9
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Pye VE, Dreveny I, Briggs LC, Sands C, Beuron F, Zhang X, Freemont PS. Going through the motions: the ATPase cycle of p97. J Struct Biol 2006; 156:12-28. [PMID: 16621604 DOI: 10.1016/j.jsb.2006.03.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 03/01/2006] [Accepted: 03/03/2006] [Indexed: 12/12/2022]
Abstract
p97 (VCP, Cdc48), a type II AAA+ ATPase family member, is ubiquitous, essential, highly abundant, and involved in a diverse range of biological functions with roles in membrane fusion, endoplasmic-reticulum associated degradation, transcriptional activation, and cell cycle control. As such, dysfunction of this protein has serious pathological consequences and has been implicated in a variety of cancers and neurodegenerative diseases. p97 has a large number of adaptor proteins through which it transmits energy from ATPase activity to conformational changes which are then exerted onto target proteins. p97 has been studied by a variety of biochemical and structural techniques at various resolutions and stages throughout its ATPase cycle. From these studies, many models have been proposed and consequently a single model for p97's action cannot be suggested. Many questions about the mechanism of p97 still remain, including whether the protomers act in a concerted manner and crucially how the induced changes in p97 are transmitted to its adaptor proteins and target substrates. The elucidation of p97's mechanism is not only important in furthering our knowledge of this intriguing protein and its many functions, but subsequently in the development of potential therapies for diseases associated with p97 dysfunction.
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Affiliation(s)
- Valerie E Pye
- Division of Molecular Biosciences, Centre for Structural Biology, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
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10
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Summer H, Bruderer R, Weber-Ban E. Characterization of a new AAA+ protein from archaea. J Struct Biol 2006; 156:120-9. [PMID: 16584891 DOI: 10.1016/j.jsb.2006.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 01/23/2006] [Accepted: 01/26/2006] [Indexed: 10/24/2022]
Abstract
We investigated a new archaeal member of the AAA+ protein family (ATPases associated with various cellular activities) which is found in all methanogenic archaea and the sulphate-reducer Archaeoglobus fulgidus. These proteins cluster to COG1223 predicted to form a subgroup of the AAA+ ATPases. The gene from A. fulgidus codes for a protein of 40 kDa monomeric molecular weight, which we overexpressed in Escherichia coli and purified to homogeneity. The protein forms ring-shaped complexes with a diameter of 125A as determined by electron microscopy. Using sedimentation equilibrium analysis we demonstrate that it assembles into hexamers over a wide concentration range both in presence and absence of ATP. As suggested by homology to other members of the AAA+ family, the complex binds and hydrolyzes ATP. Michaelis-Menten analysis revealed a k(cat) of 118 min(-1) and a K(M) of 1.4 mM at 78 degrees C. This hyperthermophilic archaeal ATPase is stable to 86 degrees C and the ATPase activity is maximal at this temperature. The protein is most homologous to the AAA-domain of FtsH from bacteria, while the N-terminal domain shows predicted structural homology to members of the CDC48 family of AAA proteins. Possible roles of this new AAA+ protein are discussed.
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Affiliation(s)
- Heike Summer
- Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland
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11
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Maupin-Furlow JA, Humbard MA, Kirkland PA, Li W, Reuter CJ, Wright AJ, Zhou G. Proteasomes from Structure to Function: Perspectives from Archaea. Curr Top Dev Biol 2006; 75:125-69. [PMID: 16984812 DOI: 10.1016/s0070-2153(06)75005-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Insight into the world of proteolysis has expanded considerably over the past decade. Energy-dependent proteases, such as the proteasome, are no longer viewed as nonspecific degradative enzymes associated solely with protein catabolism but are intimately involved in controlling biological processes that span life to death. The proteasome maintains this exquisite control by catalyzing the precisely timed and rapid turnover of key regulatory proteins. Proteasomes also interplay with chaperones to ensure protein quality and to readjust the composition of the proteome following stress. Archaea encode proteasomes that are highly related to those of eukaryotes in basic structure and function. Investigations of archaeal proteasomes coupled with those of eukaryotes has greatly facilitated our understanding of the molecular mechanisms that govern regulated protein degradation by this elaborate nanocompartmentalized machine.
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Affiliation(s)
- Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida Gainesville, Florida 32611, USA
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12
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Rienties IM, Vink J, Borst JW, Russinova E, de Vries SC. The Arabidopsis SERK1 protein interacts with the AAA-ATPase AtCDC48, the 14-3-3 protein GF14lambda and the PP2C phosphatase KAPP. PLANTA 2005; 221:394-405. [PMID: 15592873 DOI: 10.1007/s00425-004-1447-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Accepted: 09/10/2004] [Indexed: 05/13/2023]
Abstract
Leucine-rich repeat (LRR)-containing transmembrane receptor-like kinases (RLKs) are important components of plant signal transduction. The Arabidopsis thaliana somatic embryogenesis receptor-like kinase 1 (AtSERK1) is an LRR-RLK proposed to participate in a signal transduction cascade involved in embryo development. By yeast two-hybrid screening we identified AtCDC48, a homologue of the mammalian AAA-ATPase p97 and GF14lambda, a member of the Arabidopsis family of 14-3-3 proteins as AtSERK1 interactors. In vitro, the AtSERK1 kinase domain is able to transphosphorylate and bind both AtCDC48 and GF14lambda. In yeast, AtCDC48 interacts with GF14lambda and with the PP2C phosphatase KAPP. In plant protoplasts AtSERK1 interacts with GF14lambda.
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Affiliation(s)
- Ingrid M Rienties
- Laboratory of Biochemistry, Department of Agrotechnology and Food Sciences, Wageningen University and Research Centre, Dreijenlaan 3, 6703, HA, Wageningen, The Netherlands
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13
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Yakushiji Y, Yamanaka K, Ogura T. Identification of a cysteine residue important for the ATPase activity of C. elegans fidgetin homologue. FEBS Lett 2005; 578:191-7. [PMID: 15581640 DOI: 10.1016/j.febslet.2004.11.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 11/02/2004] [Accepted: 11/03/2004] [Indexed: 11/21/2022]
Abstract
Based on the amino acid alignment, Caenorhabditis elegans F32D1.1 was identified to be a homologue of the mammalian fidgetin. We produced and purified the F32D1.1 protein by using a baculovirus-expression system. F32D1.1 has an ATPase activity, which is sensitive to N-ethylmaleimide. Km and Vmax for the ATPase activity of F32D1.1 were estimated to be 0.44 mM and 225 nmol/mg/min, respectively. When the cysteine at the position of 368 was mutated to alanine, the ATPase activity was greatly decreased; Vmax was decreased to one-sixth, while Km remained similar. These results suggest that the unique position of cysteine 368, located immediately downstream of the Walker A motif, plays an important role in the ATP hydrolysis process of C. elegans F32D1.1 protein.
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Affiliation(s)
- Yasufumi Yakushiji
- Division of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 862-0976, Japan
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14
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Huyton T, Pye VE, Briggs LC, Flynn TC, Beuron F, Kondo H, Ma J, Zhang X, Freemont PS. The crystal structure of murine p97/VCP at 3.6A. J Struct Biol 2004; 144:337-48. [PMID: 14643202 DOI: 10.1016/j.jsb.2003.10.007] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
p97/VCP is a member of the AAA ATPase family and has roles in both membrane fusion and ubiquitin dependent protein degradation. Here, we present a 3.6A crystal structure of murine p97 in which D2 domain has been modelled as poly-alanine and the remaining approximately 100 residues are absent. The resulting structure illustrates a head-to-tail packing arrangement of the two p97 AAA domains in a natural hexameric state with D1 ADP bound and D2 nucleotide free. The head-to-tail packing arrangement observed in this structure is in contrast to our previously predicted tail-to-tail packing model. The linker between the D1 and D2 domains is partially disordered, suggesting a flexible nature. Normal mode analysis of the crystal structure suggests anti-correlated motions and distinct conformational states of the two AAA domains.
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Affiliation(s)
- Trevor Huyton
- Department of Biological Sciences, Imperial College London, South Kensington SW7 2AZ, UK
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15
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Bhakat KK, Izumi T, Yang SH, Hazra TK, Mitra S. Role of acetylated human AP-endonuclease (APE1/Ref-1) in regulation of the parathyroid hormone gene. EMBO J 2004; 22:6299-309. [PMID: 14633989 PMCID: PMC291836 DOI: 10.1093/emboj/cdg595] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The human AP-endonuclease (APE1/Ref-1), a multifunctional protein central to repairing abasic sites and single-strand breaks in DNA, also plays a role in transcriptional regulation. Besides activating some transcription factors, APE1 is directly involved in Ca2+-dependent downregulation of parathyroid hormone (PTH) expression by binding to negative calcium response elements (nCaREs) present in the PTH promoter. Here we show that APE1 is acetylated both in vivo and in vitro by the transcriptional co-activator p300 which is activated by Ca2+. Acetylation at Lys6 or Lys7 enhances binding of APE1 to nCaRE. APE1 stably interacts with class I histone deacetylases (HDACs) in vivo. An increase in extracellular calcium enhances the level of acetylated APE1 which acts as a repressor for the PTH promoter. Moreover, chromatin immunoprecipitation (ChIP) assay revealed that acetylation of APE1 enhanced binding of the APE1-HDACs complex to the PTH promoter. These results indicate that acetylation of APE1 plays an important role in this key repair protein's action in transcriptional regulation.
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Affiliation(s)
- Kishor K Bhakat
- Sealy Center for Molecular Science and Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX 77555-1079, USA
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16
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You Z, Ishimi Y, Mizuno T, Sugasawa K, Hanaoka F, Masai H. Thymine-rich single-stranded DNA activates Mcm4/6/7 helicase on Y-fork and bubble-like substrates. EMBO J 2003; 22:6148-60. [PMID: 14609960 PMCID: PMC275434 DOI: 10.1093/emboj/cdg576] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2003] [Revised: 09/09/2003] [Accepted: 09/25/2003] [Indexed: 11/13/2022] Open
Abstract
The presence of multiple clusters of runs of asymmetric adenine or thymine is a feature commonly found in eukaryotic replication origins. Here we report that the helicase and ATPase activities of the mammalian Mcm4/6/7 complex are activated specifically by thymine stretches. The Mcm helicase is specifically activated by a synthetic bubble structure which mimics an activated replication origin, as well as by a Y-fork structure, provided that a single-stranded DNA region of sufficient length is present in the unwound segment or 3' tail, respectively, and that it carries clusters of thymines. Sequences derived from the human lamin B2 origin can serve as a potent activator for the Mcm helicase, and substitution of its thymine clusters with guanine leads to loss of this activation. At the fork, Mcm displays marked processivity, expected for a replicative helicase. These findings lead us to propose that selective activation by stretches of thymine sequences of a fraction of Mcm helicases loaded onto chromatin may be the determinant for selection of initiation sites on mammalian genomes.
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Affiliation(s)
- Zhiying You
- Department of Cell Biology, Tokyo Metropolitan Institute of Medical Science, 18-22 Honkomagome 3-chome, Bunkyo-ku, Tokyo 113-8613, Japan
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17
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Maupin-Furlow JA, Kaczowka SJ, Reuter CJ, Zuobi-Hasona K, Gil MA. Archaeal proteasomes: potential in metabolic engineering. Metab Eng 2003; 5:151-63. [PMID: 12948749 DOI: 10.1016/s1096-7176(03)00030-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Archaea are a valuable source of enzymes for industrial and scientific applications because of their ability to survive extreme conditions including high salt and temperature. Thanks to advances in molecular biology and genetics, archaea are also attractive hosts for metabolic engineering. Understanding how energy-dependent proteases and chaperones function to maintain protein quality control is key to high-level synthesis of recombinant products. In archaea, proteasomes are central players in energy-dependent proteolysis and form elaborate nanocompartments that degrade proteins into oligopeptides by processive hydrolysis. The catalytic core responsible for this proteolytic activity is the 20S proteasome, a barrel-shaped particle with a central channel and axial gates on each end that limit substrate access to a central proteolytic chamber. AAA proteins (ATPases associated with various cellular activities) are likely to play several roles in mediating energy-dependent proteolysis by the proteasome. These include ATP binding/hydrolysis, substrate binding/unfolding, opening of the axial gates, and translocation of substrate into the proteolytic chamber.
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Affiliation(s)
- Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida, Room 1052, Building 981, Gainesville, FL 32611-0700, USA.
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18
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Song C, Wang Q, Li CCH. ATPase activity of p97-valosin-containing protein (VCP). D2 mediates the major enzyme activity, and D1 contributes to the heat-induced activity. J Biol Chem 2003; 278:3648-55. [PMID: 12446676 DOI: 10.1074/jbc.m208422200] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 97-kDa valosin-containing protein (p97-VCP) plays a role in a wide variety of cellular activities, many of which are regulated by the ubiquitin-proteasome (Ub-Pr)-mediated degradation pathway. We previously demonstrated that VCP binds to multi-ubiquitin chains and may act as a molecular chaperone that targets the ubiquitinated substrates to the proteasome for degradation. In this report, we show that although the ubiquitin chain-binding activity, carried out by the N-terminal 200 residues (N domain), is necessary for the degradation of proteasome substrates, it is not sufficient. Using in vitro degradation assays, we demonstrated that the entire VCP molecule, consisting of the N domain and two ATPase domains D1 and D2, is required for mediating the Ub-Pr degradation. The ATPase activity of VCP requires Mg(2+), and is stimulated by high temperature. Under optimal conditions, VCP hydrolyzes ATP with a K(m) of approximately 0.33 mm and a V(max) of approximately 0.52 nmol P(i) min(-1) microg(-1). At a physiological temperature, mutation in D2 significantly inhibits the ATPase activity, while that in D1 has little effect. Interestingly, mutations in D1, but not D2, abolish the heat-stimulated ATPase activity. Thus, we provide the first demonstration that the ATPase activity of VCP is required for mediating the Ub-Pr degradation, that D2 accounts for the major ATPase activity, and that D1 contributes to the heat-induced activity.
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Affiliation(s)
- Changcheng Song
- Basic Research Program, SAIC-Frederick, National Cancer Institute, Frederick, Maryland 21702, USA
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19
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Abstract
The ATPase Cdc48 is required for membrane fusion and protein degradation. Recently it has been suggested that Cdc48 in a complex with Ufd1 and Npl4 acts as an ubiquitin-dependent chaperone. Here it is shown that recombinant Cdc48 alone can distinguish between the native and the non-native conformation of model substrates. First, Cdc48 prevents luciferase from aggregating following a heat shock. Second, it inhibits the aggregation of rhodanese upon dilution. Third, Cdc48 binds specifically to heat-denatured luciferase. These chaperone-like functions seem to be independent of ATPase activity. Furthermore, Cdc48 can act as a co-chaperone in the Hsc70-Hsp40 chaperone system. These results show that Cdc48 possesses chaperone-like activities and can functionally interact with Hsc70. Cdc48's ability to recognise denatured proteins can also be a source of unspecific binding in biochemical interaction experiments.
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Affiliation(s)
- Sven Thoms
- ZMBH, Center for Molecular Biology, Heidelberg University, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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20
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Abstract
The ubiquitin-proteasome pathway has a well-defined beginning and end. Target proteins are initially recognized by upstream components and tagged with polyubiquitin chains. The 26S proteasome then degrades these polyubiquitinated proteins. Until recently, it was not known what, if any, steps occurred between the initial polyubiquitination of target proteins and their final degradation. Several new papers investigating the function of the Cdc48-Ufd1-Npl4 complex indicate that there is indeed a middle to the ubiquitin-proteasome pathway. The Cdc48-Ufd1-Npl4 complex functions in the recognition of several polyubiquitin-tagged proteins and facilitates their presentation to the 26S proteasome for processive degradation or even more specific processing. The elucidation of Cdc48, Ufd1 and Npl4 action not only provides long-sought functions for these specific proteins, but illuminates a poorly understood part of the ubiquitin-proteasome pathway.
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Affiliation(s)
- Nathan W Bays
- Exelixis, Inc., 170 Harbor Way, South San Francisco, California 94080, USA
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21
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Rockel B, Jakana J, Chiu W, Baumeister W. Electron cryo-microscopy of VAT, the archaeal p97/CDC48 homologue from Thermoplasma acidophilum. J Mol Biol 2002; 317:673-81. [PMID: 11955016 DOI: 10.1006/jmbi.2002.5448] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
VAT (valosine containing protein-like ATPase from Thermoplasma acidophilum), an archaeal member of the AAA-family (ATPases associated with a variety of cellular activities) that possesses foldase as well as unfoldase-activity, forms homo-hexameric rings like its eukaryotic homologues p97 and CDC48. The VAT-monomer exhibits the tripartite domain architecture typical for type II AAA-ATPases: N-D1-D2, whereby N is the substrate binding N-terminal domain preceding domains D1 and D2, both containing AAA-modules. Recent 3-D reconstructions of VAT and p97 as obtained by electron microscopy suffer from weakly represented N-domains, probably a consequence of their flexible linkage to the hexameric core. Here we used electron cryo-microscopy and 3-D reconstruction of single particles in order to generate a 3-D model of VAT at 2.3 nm resolution. The hexameric core of the VAT-complex (diameter 13.2 nm, height 8.4 nm) encloses a central cavity and the substrate-binding N-domains are clearly arranged in the upper periphery. Comparison with the p97 3-D reconstruction and the recently determined crystal structure of p97-N-D1 suggests a tail-to-tail arrangement of D1 and D2 in VAT.
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Affiliation(s)
- Beate Rockel
- Max-Planck-Institut für Biochemie, Abteilung Molekulare Strukturbiologie, Am Klopferspitz 18 a, 82152 Martinsried, Germany.
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22
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Rape M, Hoppe T, Gorr I, Kalocay M, Richly H, Jentsch S. Mobilization of processed, membrane-tethered SPT23 transcription factor by CDC48(UFD1/NPL4), a ubiquitin-selective chaperone. Cell 2001; 107:667-77. [PMID: 11733065 DOI: 10.1016/s0092-8674(01)00595-5] [Citation(s) in RCA: 358] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The OLE pathway of yeast regulates the level of the ER-bound enzyme Delta9-fatty acid desaturase OLE1, thereby controlling membrane fluidity. A central component of this regulon is the transcription factor SPT23, a homolog of mammalian NF-kappaB. SPT23 is synthesized as an inactive, ER membrane-anchored precursor that is activated by regulated ubiquitin/proteasome-dependent processing (RUP). We now show that SPT23 dimerizes prior to processing and that the processed molecule, p90, retains its ubiquitin modification and initially remains tethered to its unprocessed, membrane-bound SPT23 partner. Subsequently, p90 is liberated from its partner for nuclear targeting by the activity of the chaperone-like CDC48(UFD1/NPL4) complex. Remarkably, this enzyme binds preferentially ubiquitinated substrates, suggesting that CDC48(UFD1/NPL4) is qualified to selectively remove ubiquitin conjugates from protein complexes.
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Affiliation(s)
- M Rape
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18a, 82152, Martinsried, Germany
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23
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Ruepp A, Rockel B, Gutsche I, Baumeister W, Lupas AN. The Chaperones of the archaeon Thermoplasma acidophilum. J Struct Biol 2001; 135:126-38. [PMID: 11580262 DOI: 10.1006/jsbi.2001.4402] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chaperonesare an essential component of a cell's ability to respond to environmental challenges. Chaperones have been studied primarily in bacteria, but in recent years it has become apparent that some classes of chaperones either are very divergent in bacteria relative to archaea and eukaryotes or are missing entirely. In contrast, a high degree of similarity was found between the chaperonins of archaea and those of the eukaryotic cytosol, which has led to the establishment of archaeal model systems. The archaeon most extensively used for such studies is Thermoplasma acidophilum, which thrives at 59 degrees C and pH 2. Here we review information on its chaperone complement in light of the recently determined genome sequence.
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Affiliation(s)
- A Ruepp
- Department of Molecular Structural Biology, Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, Martinsried, D-82152, Germany
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24
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Abstract
In eukaryotic cells, the majority of proteins are degraded via the ATP-dependent ubiquitin/26S proteasome pathway. The proteasome is the proteolytic component of the pathway. It is a very large complex with a mass of around 2.5 MDa, consisting of at least 62 proteins encoded by 31 genes. The eukaryotic proteasome has evolved from a simpler archaebacterial form, similar in structure but containing only three different peptides. One of these peptides is an ATPase belonging to the AAA (Triple-A) family of ATPASES: Gene duplication and diversification has resulted in six paralogous ATPases being present in the eukaryotic proteasome. While sequence analysis studies clearly show that the six eukaryotic proteasomal ATPases have evolved from the single archaebacterial proteasomal ATPase, the deep node structures of the phylogenetic constructions lack resolution. Incorporating physical data to provide support for alternative phylogenetic hypotheses, we have constructed a model of a possible evolutionary history of the proteasomal ATPASES:
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Affiliation(s)
- K Wollenberg
- Department of Genetics, North Carolina State University, Raleigh, NC 27695-7614
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25
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Rockel B, Guckenberger R, Gross H, Tittmann P, Baumeister W. Rotary and unidirectional metal shadowing of VAT: localization of the substrate-binding domain. J Struct Biol 2000; 132:162-8. [PMID: 11162738 DOI: 10.1006/jsbi.2000.4313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
AAA-ATPases have important roles in manifold cellular processes. VAT (valosine-containing protein-like ATPase of Thermoplasma acidophilum), a hexameric archaeal member of this family, has the tripartite domain structure N-D1-D2 that is characteristic of many members of this family. N, the N-terminal domain of 20.5 kDa, has been implicated in substrate binding. We have applied rotary and unidirectional shadowing to VAT and an N-terminally deleted mutant, VAT(Delta N), in order to map the location of this domain. For the analysis of data derived from unidirectionally shadowed samples we used a new approach combining eigenvector analysis with surface relief reconstruction. Averages of rotary shadowed particles as well as relief reconstructions map the N-terminal domains to the periphery of the hexameric complex and reveal their bipartite structure. Thus, this method appears to be well suited to study the conformational changes that occur during the functional cycle of the protein.
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Affiliation(s)
- B Rockel
- Abteilung Molekulare Strukturbiologie, Max-Planck-Institut für Biochemie, Am Klopferspitz 18a, 82152 Martinsried, Germany
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26
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Hirano T, Ishihara K, Hibi M. Roles of STAT3 in mediating the cell growth, differentiation and survival signals relayed through the IL-6 family of cytokine receptors. Oncogene 2000; 19:2548-56. [PMID: 10851053 DOI: 10.1038/sj.onc.1203551] [Citation(s) in RCA: 916] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Members of the IL-6 cytokine family are involved in a variety of biological responses, including the immune response, inflammation, hematopoiesis, and oncogenesis by regulating cell growth, survival, and differentiation. These cytokines use gp130 as a common receptor subunit. The binding of ligand to gp130 activates the JAK/STAT signal transduction pathway, where STAT3 plays a central role in transmitting the signals from the membrane to the nucleus. STAT3 is essential for gp130-mediated cell survival and G1 to S cell-cycle-transition signals. Both c-myc and pim have been identified as target genes of STAT3 and together can compensate for STAT3 in cell survival and cell-cycle transition. STAT3 is also required for gp130-mediated maintenance of the pluripotential state of proliferating embryonic stem cells and for the gp130-induced macrophage differentiation of M1 cells. Furthermore, STAT3 regulates cell movement, such as leukocyte, epidermal cell, and keratinocyte migration. STAT3 also appears to regulate B cell differentiation into antibody-forming plasma cells. Since the IL-6/gp130/STAT3 signaling pathway is involved in both B cell growth and differentiation into plasma cells it is likely to play a central role in the generation of plasma cell neoplasias. Oncogene (2000).
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Affiliation(s)
- T Hirano
- Division of Molecular Oncology C-7, Biomedical Research Center, Osaka University Graduate School of Medicine, 2-2 Yamada-oko, Suita, Osaka 565-0871, Japan
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27
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Brügger B, Nickel W, Weber T, Parlati F, McNew JA, Rothman JE, Söllner T. Putative fusogenic activity of NSF is restricted to a lipid mixture whose coalescence is also triggered by other factors. EMBO J 2000; 19:1272-8. [PMID: 10716927 PMCID: PMC305668 DOI: 10.1093/emboj/19.6.1272] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It has recently been reported that N-ethylmaleimide-sensitive fusion ATPase (NSF) can fuse protein-free liposomes containing substantial amounts of 1,2-dioleoylphosphatidylserine (DOPS) and 1, 2-dioleoyl-phosphatidyl-ethanolamine (DOPE) (Otter-Nilsson et al., 1999). The authors impart physiological significance to this observation and propose to re-conceptualize the general role of NSF in fusion processes. We can confirm that isolated NSF can fuse liposomes of the specified composition. However, this activity of NSF is resistant to inactivation by N-ethylmaleimide and does not depend on the presence of alpha-SNAP (soluble NSF-attachment protein). Moreover, under the same conditions, either alpha-SNAP, other proteins apparently unrelated to vesicular transport (glyceraldehyde-3-phosphate dehydrogenase or lactic dehydrogenase) or even 3 mM magnesium ions can also cause lipid mixing. In contrast, neither NSF nor the other proteins nor magnesium had any significant fusogenic activity with liposomes composed of a biologically occurring mixture of lipids. A straightforward explanation is that the lipid composition chosen as optimal for NSF favors non-specific fusion because it is physically unstable when formed into liposomes. A variety of minor perturbations could then trigger coalescence.
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Affiliation(s)
- B Brügger
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA
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28
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Wilson HL, Ou MS, Aldrich HC, Maupin-Furlow J. Biochemical and physical properties of the Methanococcus jannaschii 20S proteasome and PAN, a homolog of the ATPase (Rpt) subunits of the eucaryal 26S proteasome. J Bacteriol 2000; 182:1680-92. [PMID: 10692374 PMCID: PMC94466 DOI: 10.1128/jb.182.6.1680-1692.2000] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 20S proteasome is a self-compartmentalized protease which degrades unfolded polypeptides and has been purified from eucaryotes, gram-positive actinomycetes, and archaea. Energy-dependent complexes, such as the 19S cap of the eucaryal 26S proteasome, are assumed to be responsible for the recognition and/or unfolding of substrate proteins which are then translocated into the central chamber of the 20S proteasome and hydrolyzed to polypeptide products of 3 to 30 residues. All archaeal genomes which have been sequenced are predicted to encode proteins with up to approximately 50% identity to the six ATPase subunits of the 19S cap. In this study, one of these archaeal homologs which has been named PAN for proteasome-activating nucleotidase was characterized from the hyperthermophile Methanococcus jannaschii. In addition, the M. jannaschii 20S proteasome was purified as a 700-kDa complex by in vitro assembly of the alpha and beta subunits and has an unusually high rate of peptide and unfolded-polypeptide hydrolysis at 100 degrees C. The 550-kDa PAN complex was required for CTP- or ATP-dependent degradation of beta-casein by archaeal 20S proteasomes. A 500-kDa complex of PAN(Delta1-73), which has a deletion of residues 1 to 73 of the deduced protein and disrupts the predicted N-terminal coiled-coil, also facilitated this energy-dependent proteolysis. However, this deletion increased the types of nucleotides hydrolyzed to include not only ATP and CTP but also ITP, GTP, TTP, and UTP. The temperature optimum for nucleotide (ATP) hydrolysis was reduced from 80 degrees C for the full-length protein to 65 degrees C for PAN(Delta1-73). Both PAN protein complexes were stable in the absence of ATP and were inhibited by N-ethylmaleimide and p-chloromercuriphenyl-sulfonic acid. Kinetic analysis reveals that the PAN protein has a relatively high V(max) for ATP and CTP hydrolysis of 3.5 and 5.8 micromol of P(i) per min per mg of protein as well as a relatively low affinity for CTP and ATP with K(m) values of 307 and 497 microM compared to other proteins of the AAA family. Based on electron micrographs, PAN and PAN(Delta1-73) apparently associate with the ends of the 20S proteasome cylinder. These results suggest that the M. jannaschii as well as related archaeal 20S proteasomes require a nucleotidase complex such as PAN to mediate the energy-dependent hydrolysis of folded-substrate proteins and that the N-terminal 73 amino acid residues of PAN are not absolutely required for this reaction.
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Affiliation(s)
- H L Wilson
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700, USA
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29
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Shirogane T, Fukada T, Muller JM, Shima DT, Hibi M, Hirano T. Synergistic roles for Pim-1 and c-Myc in STAT3-mediated cell cycle progression and antiapoptosis. Immunity 1999; 11:709-19. [PMID: 10626893 DOI: 10.1016/s1074-7613(00)80145-4] [Citation(s) in RCA: 324] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The activation of STAT3 by the cytokine receptor gp130 is required for both the G1 to S cell cycle transition and antiapoptosis. We found that Pim-1 and Pim-2 are targets for the gp130-mediated STAT3 signal. Expression of a kinase-defective Pim-1 mutant attenuated gp130-mediated cell proliferation. Constitutive expression of Pim-1 together with c-myc, another STAT3 target, fully compensated for loss of the STAT3-mediated cell cycle progression, antiapoptosis, and bcl-2 expression. We also identified valosine-containing protein (VCP) as a target gene for the Pim-1-mediated signal. Expression of a mutant VCP led cells to undergo apoptosis. These results indicate that Pim-family proteins play crucial roles in gp130-mediated cell proliferation and explain the synergy between Pim and c-Myc proteins in cell proliferation and lymphomagenesis.
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Affiliation(s)
- T Shirogane
- Division of Molecular Oncology, Biomedical Research Center, Osaka University Graduate School of Medicine, Suita, Japan
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30
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Coles M, Diercks T, Liermann J, Gröger A, Rockel B, Baumeister W, Koretke KK, Lupas A, Peters J, Kessler H. The solution structure of VAT-N reveals a 'missing link' in the evolution of complex enzymes from a simple betaalphabetabeta element. Curr Biol 1999; 9:1158-68. [PMID: 10531028 DOI: 10.1016/s0960-9822(00)80017-2] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND The VAT protein of the archaebacterium Thermoplasma acidophilum, like all other members of the Cdc48/p97 family of AAA ATPases, has two ATPase domains and a 185-residue amino-terminal substrate-recognition domain, VAT-N. VAT shows activity in protein folding and unfolding and thus shares the common function of these ATPases in disassembly and/or degradation of protein complexes. RESULTS Using nuclear magnetic resonance (NMR) spectroscopy, we found that VAT-N is composed of two equally sized subdomains. The amino-terminal subdomain VAT-Nn (comprising residues Met1-Thr92) forms a double-psi beta-barrel whose pseudo-twofold symmetry is mirrored by an internal sequence repeat of 42 residues. The carboxy-terminal subdomain VAT-Nc (comprising residues Glu93-Gly185) forms a novel six-stranded beta-clam fold. Together, VAT-Nn and VAT-Nc form a kidney-shaped structure, in close agreement with results from electron microscopy. Sequence and structure analyses showed that VAT-Nn is related to numerous proteins including prokaryotic transcription factors, metabolic enzymes, the protease cofactors UFD1 and PrlF, and aspartic proteinases. These proteins map out an evolutionary path from simple homodimeric transcription factors containing a single copy of the VAT-Nn repeat to complex enzymes containing four copies. CONCLUSIONS Our results suggest that VAT-N is a precursor of the aspartic proteinases that has acquired peptide-binding activity while remaining proteolytically incompetent. We propose that the binding site of the protein is similar to that of aspartic proteinases, in that it lies between the psi-loops of the amino-terminal beta-barrel and that it coincides with a crescent-shaped band of positive charge extending across the upper face of the molecule.
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Affiliation(s)
- M Coles
- Institut für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85747, Garching, Germany
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31
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Karata K, Inagawa T, Wilkinson AJ, Tatsuta T, Ogura T. Dissecting the role of a conserved motif (the second region of homology) in the AAA family of ATPases. Site-directed mutagenesis of the ATP-dependent protease FtsH. J Biol Chem 1999; 274:26225-32. [PMID: 10473576 DOI: 10.1074/jbc.274.37.26225] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli FtsH is an ATP-dependent protease that belongs to the AAA protein family. The second region of homology (SRH) is a highly conserved motif among AAA family members and distinguishes these proteins in part from the wider family of Walker-type ATPases. Despite its conservation across the AAA family of proteins, very little is known concerning the function of the SRH. To address this question, we introduced point mutations systematically into the SRH of FtsH and studied the activities of the mutant proteins. Highly conserved amino acid residues within the SRH were found to be critical for the function of FtsH, with mutations at these positions leading to decreased or abolished ATPase activity. The effects of the mutations on the protease activity of FtsH correlated strikingly with their effects on the ATPase activity. The ATPase-deficient SRH mutants underwent an ATP-induced conformational change similar to wild type FtsH, suggesting an important role for the SRH in ATP hydrolysis but not ATP binding. Analysis of the data in the light of the crystal structure of the hexamerization domain of N-ethylmaleimide-sensitive fusion protein suggests a plausible mechanism of ATP hydrolysis by the AAA ATPases, which invokes an intermolecular catalytic role for the SRH.
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Affiliation(s)
- K Karata
- Department of Molecular Cell Biology, Institute of Molecular Embryology, Kumamoto University School of Medicine, Kumamoto 862-0976, Japan
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32
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Golbik R, Lupas AN, Koretke KK, Baumeister W, Peters J. The Janus face of the archaeal Cdc48/p97 homologue VAT: protein folding versus unfolding. Biol Chem 1999; 380:1049-62. [PMID: 10543442 DOI: 10.1515/bc.1999.131] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Members of the AAA family of ATPases have been implicated in chaperone-like activities. We used the archaeal Cdc48/p97 homologue VAT as a model system to investigate the effect of an AAA protein on the folding and unfolding of two well-studied, heterologous substrates, cyclophilin and penicillinase. We found that, depending on the Mg2+ concentration, VAT assumes two states with maximum rates of ATP hydrolysis that differ by an order of magnitude. In the low-activity state, VAT accelerated the refolding of penicillinase, whereas in the high-activity state, it accelerated its unfolding. Both reactions were ATP-dependent. In its interaction with cyclophilin, VAT was ATP-independent and only promoted refolding. The N-terminal domain of VAT, which lacks ATPase activity, also accelerated the refolding of cyclophilin but showed no effect on penicillinase. VAT appears to be structurally equivalent over its entire length to Sec18/NSF, suggesting that these results apply more broadly to group II AAA proteins.
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Affiliation(s)
- R Golbik
- Department of Biochemistry, Martin-Luther-University, Halle-Wittenberg, Halle, Germany
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33
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Rockel B, Walz J, Hegerl R, Peters J, Typke D, Baumeister W. Structure of VAT, a CDC48/p97 ATPase homologue from the archaeon Thermoplasma acidophilum as studied by electron tomography. FEBS Lett 1999; 451:27-32. [PMID: 10356978 DOI: 10.1016/s0014-5793(99)00431-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Valosine-containing protein-like ATPase from Thermoplasma acidophilum is a member of the superfamily of ATPases associated with a diversity of cellular activities and is closely related to CDC48 from yeast and p97 from higher eukaryotes and more distantly to N-ethylmaleimide-sensitive fusion protein. We have used electron tomography to obtain low-resolution (2-2.5 nm) three-dimensional maps of both the whole 500 kDa complex and the N-terminally truncated valosine-containing protein-like ATPase from T. acidophilum complex lacking the putative substrate binding domain.
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Affiliation(s)
- B Rockel
- Max-Planck-Institut für Biochemie, Abteilung für molekulare Strukturbiologie, Martinsried, Germany
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34
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Abstract
The hexameric ATPase p97/yeast Cdc48p has been implicated in a number of cellular events that are regulated during mitosis, including homotypic membrane fusion, spindle pole body function, and ubiquitin-dependent protein degradation. p97/Cdc48p contains two conserved consensus p34cdc2 kinase phosphorylation sites within its second ATP binding domain. This domain is likely to play a role in stabilising the hexameric form of the protein. We therefore investigated whether p97 could be phosphorylated by p34cdc2 kinase in vitro, and whether phosphorylation might influence the oligomeric status of p97. Monomeric, but not hexameric, p97 was phosphorylated by p34cdc2 kinase, as was the p97-associated protein p47. However, phosphorylation by p34cdc2 kinase did not impair subsequent re-hexamerisation of p97, implying that the phosphorylated residue(s) are not critical for interaction between p97 monomers. Moreover, p97 within both interphase and mitotic cytosols was almost exclusively hexameric, suggesting that the activity of p97 is not regulated during mitosis by influencing the extent of oligomerisation.
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Affiliation(s)
- P S Mayr
- School of Biological Sciences, University of Manchester, UK
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35
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Roggy JL, Bangs JD. Molecular cloning and biochemical characterization of a VCP homolog in African trypanosomes. Mol Biochem Parasitol 1999; 98:1-15. [PMID: 10029305 DOI: 10.1016/s0166-6851(98)00114-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Through reverse transcription-polymerase chain reaction using degenerate oligonucleotide primers, a VCP homolog was identified in African trypanosomes. Sequence analysis shows a 72 and 64% deduced amino acid identity, respectively, with mouse VCP and yeast Cdc48p. Southern analysis indicates tbVCP to have a single locus with two alleles. Antibodies generated against recombinant protein recognize a 95 kDa protein in whole cell lysates of both procyclic and bloodstream trypanosomes. There is an approximately four-fold greater expression of TbVCP protein in the procyclic stage of the trypanosome life cycle. Subcellular fractionation and immunofluorescence with anti-TbVCP antibodies indicate the majority of TbVCP to be cytoplasmically localized with a small subset associated with membranes. Sucrose velocity sedimentation and gel filtration size analysis studies suggest that TbVCP is a homohexameric particle as has been demonstrated with other VCP homologs. Also like other VCP homologs, TbVCP contains an NEM-inhibitable ATPase activity. This is the first characterization of an AAA (ATPases Associated with a variety of cellular Activities) family member in African trypanosomes.
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Affiliation(s)
- J L Roggy
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison Medical School, 53706, USA
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36
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Meyer HH, Kondo H, Warren G. The p47 co-factor regulates the ATPase activity of the membrane fusion protein, p97. FEBS Lett 1998; 437:255-7. [PMID: 9824302 DOI: 10.1016/s0014-5793(98)01232-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The highly conserved ATPase p97, a member of the AAA-ATPases, is found in a complex with its co-factor p47 in rat liver cytosol. Previously it had been shown that p97-mediated reassembly of Golgi cisternae from mitotic Golgi fragments requires p47 which mediates the binding of p97 to a Golgi t-SNARE (soluble N-ethylmaleimide-sensitive factor attachment factor receptor), syntaxin 5. Here we show that it also suppresses the ATPase activity of p97 by up to 85% in a dose-dependent and saturable manner suggesting that it has other roles in the membrane fusion cycle.
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Affiliation(s)
- H H Meyer
- Cell Biology Laboratory, Imperial Cancer Research Fund, London, UK
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37
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Fleming KG, Hohl TM, Yu RC, Müller SA, Wolpensinger B, Engel A, Engelhardt H, Brünger AT, Söllner TH, Hanson PI. A revised model for the oligomeric state of the N-ethylmaleimide-sensitive fusion protein, NSF. J Biol Chem 1998; 273:15675-81. [PMID: 9624162 DOI: 10.1074/jbc.273.25.15675] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The N-ethylmaleimide-sensitive fusion protein (NSF) is an ATPase that plays an essential role in intracellular membrane trafficking. Previous reports have concluded that NSF forms either a tetramer or a trimer in solution, and that assembly of the oligomer is essential for efficient activity in membrane transport reactions. However, in recent electron microscopic analyses NSF appears as a hexagonal cylinder similar in size to related ATPases known to be hexamers. We have therefore reevaluated NSF's oligomeric state using a variety of quantitative biophysical techniques. Sedimentation equilibrium and sedimentation velocity analytical ultracentrifugation, transmission electron microscopy with rotational image analysis, scanning transmission electron microscopy, and multiangle light scattering all demonstrate that, in the presence of nucleotide, NSF is predominantly a hexamer. Sedimentation equilibrium results further suggest that the NSF hexamer is held together by oligomerization of its D2 domains. The sedimentation coefficient, s20,w0, of 13.4 (+/-0. 1) S indicates that NSF has unusual hydrodynamic characteristics that cannot be solely explained by its shape. The demonstration that NSF is a hexameric oligomer highlights structural similarities between it and several related ATPases which act by switching the conformational states of their protein substrates in order to activate them for subsequent reactions.
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Affiliation(s)
- K G Fleming
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA
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38
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Babst M, Wendland B, Estepa EJ, Emr SD. The Vps4p AAA ATPase regulates membrane association of a Vps protein complex required for normal endosome function. EMBO J 1998; 17:2982-93. [PMID: 9606181 PMCID: PMC1170638 DOI: 10.1093/emboj/17.11.2982] [Citation(s) in RCA: 613] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Vps4p is an AAA-type ATPase required for efficient transport of biosynthetic and endocytic cargo from an endosome to the lysosome-like vacuole of Saccharomyces cerevisiae. Vps4p mutants that do not bind ATP or are defective in ATP hydrolysis were characterized both in vivo and in vitro. The nucleotide-free or ADP-bound form of Vps4p existed as a dimer, whereas in the ATP-locked state, Vps4p dimers assembled into a decameric complex. This suggests that ATP hydrolysis drives a cycle of association and dissociation of Vps4p dimers/decamers. Nucleotide binding also regulated the association of Vps4p with an endosomal compartment in vivo. This membrane association required the N-terminal coiled-coil motif of Vps4p, but deletion of the coiled-coil domain did not affect ATPase activity or oligomeric assembly of the protein. Membrane association of two previously uncharacterized class E Vps proteins, Vps24p and Vps32p/Snf7p, was also affected by mutations in VPS4. Upon inactivation of a temperature-conditional vps4 mutant, Vps24p and Vps32p/Snf7p rapidly accumulated in a large membrane-bound complex. Immunofluorescence indicated that both proteins function with Vps4p at a common endosomal compartment. Together, the data suggest that the Vps4 ATPase catalyzes the release (uncoating) of an endosomal membrane-associated class E protein complex(es) required for normal morphology and sorting activity of the endosome.
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Affiliation(s)
- M Babst
- Division of Cellular Molecular Medicine and Howard Hughes Medical Institute, University of California at San Diego, School of Medicine La Jolla, CA 92093-0668, USA
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39
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van Agthoven T, van Agthoven TL, Dekker A, van der Spek PJ, Vreede L, Dorssers LC. Identification of BCAR3 by a random search for genes involved in antiestrogen resistance of human breast cancer cells. EMBO J 1998; 17:2799-808. [PMID: 9582273 PMCID: PMC1170620 DOI: 10.1093/emboj/17.10.2799] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The antiestrogen tamoxifen is important in the treatment of hormone-dependent breast cancer, although development of resistance is inevitable. To unravel the molecular mechanisms of antiestrogen resistance, a search for involved genes was initiated. Retrovirus-mediated insertional mutagenesis was applied to human ZR-75-1 breast cancer cells. Infected cells were subjected to tamoxifen selection and a panel of resistant cell clones was established. Screening for a common integration site resulted in the identification of a novel gene designated BCAR3. Transfer of this locus by cell fusion or transfection of the BCAR3 cDNA to ZR75-1 and MCF-7 cells induces antiestrogen resistance. BCAR3 represents a putative SH2 domain-containing protein and is partly homologous to the cell division cycle protein CDC48.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antineoplastic Agents, Hormonal/pharmacology
- Base Sequence
- Binding Sites
- Breast Neoplasms/drug therapy
- Breast Neoplasms/genetics
- Cell Fusion
- Cloning, Molecular
- DNA, Complementary
- DNA, Neoplasm
- Drug Resistance, Neoplasm/genetics
- Estrogen Antagonists/pharmacology
- Female
- Gene Expression
- Humans
- Molecular Sequence Data
- Protein Biosynthesis
- RNA, Messenger
- Receptors, Cyclic AMP/genetics
- Sequence Homology, Amino Acid
- Tamoxifen/pharmacology
- Transcription, Genetic
- Tumor Cells, Cultured
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Affiliation(s)
- T van Agthoven
- Department of Molecular Biology, Daniel den Hoed Cancer Center, University Hospital Rotterdam, Rotterdam, The Netherlands
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40
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Wolf S, Nagy I, Lupas A, Pfeifer G, Cejka Z, Müller SA, Engel A, De Mot R, Baumeister W. Characterization of ARC, a divergent member of the AAA ATPase family from Rhodococcus erythropolis. J Mol Biol 1998; 277:13-25. [PMID: 9514743 DOI: 10.1006/jmbi.1997.1589] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A gene encoding a AAA ATPase was discovered in the 5' region of the second operon of 20 S proteasome subunits in the nocardioform actinomycete Rhodococcus erythropolis NI86/21. The gene was cloned and expressed in Escherichia coli. The protein, ARC (AAA ATPase forming Ring-shaped Complexes), is a divergent member of the AAA family. The deduced product of the arc gene is 591 residues long (66 kDa). The purified protein possesses a low, N-ethylmaleimide-sensitive ATPase activity and forms rings of six subunits, arranged symmetrically around a central opening or cavity. Two-dimensional crystals grown on lipid monolayers yielded images of the ATPase molecules in "end-on" orientation at 1.9 nm resolution.
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Affiliation(s)
- S Wolf
- Max-Planck-Institut für Biochemie, Am Klopferspitz 18a, Martinsried, D-82152, Germany
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41
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Madeo F, Schlauer J, Zischka H, Mecke D, Fröhlich KU. Tyrosine phosphorylation regulates cell cycle-dependent nuclear localization of Cdc48p. Mol Biol Cell 1998; 9:131-41. [PMID: 9436996 PMCID: PMC25228 DOI: 10.1091/mbc.9.1.131] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cdc48p from Saccharomyces cerevisiae and its highly conserved mammalian homologue VCP (valosin-containing protein) are ATPases with essential functions in cell division and homotypic fusion of endoplasmic reticulum vesicles. Both are mainly attached to the endoplasmic reticulum, but relocalize in a cell cycle-dependent manner: Cdc48p enters the nucleus during late G1; VCP aggregates at the centrosome during mitosis. The nuclear import signal sequence of Cdc48p was localized near the amino terminus and its function demonstrated by mutagenesis. The nuclear import is regulated by a cell cycle-dependent phosphorylation of a tyrosine residue near the carboxy terminus. Two-hybrid studies indicate that the phosphorylation results in a conformational change of the protein, exposing the nuclear import signal sequence previously masked by a stretch of acidic residues.
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Affiliation(s)
- F Madeo
- Physiologisch-chemisches Institut der Universität Tübingen, Germany
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42
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Madeo F, Schlauer J, Fröhlich KU. Identification of the regions of porcine VCP preventing its function in Saccharomyces cerevisiae. Gene 1997; 204:145-51. [PMID: 9434177 DOI: 10.1016/s0378-1119(97)00535-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cdc48p is essential for homotypic endoplasmic reticular fusion in Saccharomyces cerevisiae. It is localized at the endoplasmic reticulum during most of the cell division cycle but concentrates in the nucleus at the G1/S-transition. Its mammalian homologue VCP alternates between the endoplasmic reticulum and the centrosome in dependence of the cell cycle. Though Cdc48p and porcine VCP show a high sequence conservation--almost 70% of their amino acid residues are identical the VCP gene fails to complement a disruption of CDC48. Complementation studies with CDC48 and VCP gene hybrids show that an exchange of the central Cdc48p domain for the central VCP domain prevents a complementation of a CDC48 disruption, although this is the best conserved region between the two proteins. Protein chimeras containing the N-terminal part of VCP only complement a disruption of CDC48 when expressed at high levels. The respective yeast strain shows a nucleus devoid of Cdc48p. In contrast to VCP, Cdc48p contains an almost perfect nuclear targeting sequence in this region. Exchange of the C-terminal Cdc48p domain for the C-terminus of VCP leads to normal viability of the cell, even at low expression levels.
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Affiliation(s)
- F Madeo
- Physiologisch-chemisches Institut, Universität Tübingen, Germany
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43
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Abstract
The AAA protein family, a recently recognized group of Walker-type ATPases, has been subjected to an extensive sequence analysis. Multiple sequence alignments revealed the existence of a region of sequence similarity, the so-called AAA cassette. The borders of this cassette were localized and within it, three boxes of a high degree of conservation were identified. Two of these boxes could be assigned to substantial parts of the ATP binding site (namely, to Walker motifs A and B); the third may be a portion of the catalytic center. Phylogenetic trees were calculated to obtain insights into the evolutionary history of the family. Subfamilies with varying degrees of intra-relatedness could be discriminated; these relationships are also supported by analysis of sequences outside the canonical AAA boxes: within the cassette are regions that are strongly conserved within each subfamily, whereas little or even no similarity between different subfamilies can be observed. These regions are well suited to define fingerprints for subfamilies. A secondary structure prediction utilizing all available sequence information was performed and the result was fitted to the general 3D structure of a Walker A/GTPase. The agreement was unexpectedly high and strongly supports the conclusion that the AAA family belongs to the Walker superfamily of A/GTPases.
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Affiliation(s)
- A Beyer
- Institut für Physiologische Chemie, Medizinische Fakultät, Ruhr-Universität, Bochum, Germany.
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44
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Abstract
Among the hundreds of proteases characterized so far, most of which are monomeric or dimeric, there is a small group that form compartments through self-association and that segregate their proteolytic active sites to the interior of these compartments. Although few in number, they represent the main agents of intracellular protein breakdown. They belong to different hydrolase families but have converged towards the same barrel-shaped architecture. Frequently, they are coupled to chaperone-like ATPases of similar quaternary structure that regulate the access to the proteolytic compartments and appear to have been recruited from the same branch of P-loop NTPases.
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Affiliation(s)
- A Lupas
- Smithkline Beecham Pharmaceuticals, Collegeville, PA 19426-0989, USA.
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45
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Latterich M, Fröhlich KU, Schekman R. Membrane fusion and the cell cycle: Cdc48p participates in the fusion of ER membranes. Cell 1995; 82:885-93. [PMID: 7553849 DOI: 10.1016/0092-8674(95)90268-6] [Citation(s) in RCA: 308] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The fusion of endoplasmic reticulum (ER) membranes in yeast is an essential process required for normal progression of the nuclear cell cycle, karyogamy, and the maintenance of an intact organellar compartment. We showed previously that this process requires a novel fusion machinery distinct from the classic membrane docking/fusion machinery containing Sec17p (alpha-SNAP) and Sec18p (NSF). Here we show that Cdc48p, a cell-cycle protein with homology to Sec18p, is required in ER fusion. A temperature-sensitive cdc48 mutant is conditionally defective in ER fusion in vitro. Addition of purified Cdc48p restores the fusion of isolated cdc48 mutant ER membranes. We propose that Cdc48p is part of an evolutionarily conserved fusion/docking machinery involved in multiple homotypic fusion events.
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Affiliation(s)
- M Latterich
- Howard Hughes Medical Institute, University of California, Berkeley 94720, USA
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