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Qureshi BM, Behrmann E, Schöneberg J, Loerke J, Bürger J, Mielke T, Giesebrecht J, Noé F, Lamb TD, Hofmann KP, Spahn CMT, Heck M. It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods. Open Biol 2018; 8:180075. [PMID: 30068566 PMCID: PMC6119865 DOI: 10.1098/rsob.180075] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 07/06/2018] [Indexed: 12/21/2022] Open
Abstract
Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction-diffusion simulations. Gα* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of Gα* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 Gα* · PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that Gα* · PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of Gα* which binds with lower affinity, forming Gα* · PDE6 · Gα*. Reaction-diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of Gα* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated Gα* fails to activate the effector enzyme.
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Affiliation(s)
- Bilal M Qureshi
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Elmar Behrmann
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Johannes Schöneberg
- Department of Mathematics, Computer Science and Bioinformatics, Freie Universität Berlin, Berlin, Germany
| | - Justus Loerke
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Jörg Bürger
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Thorsten Mielke
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
- Microscopy and Cryo Electron Microscopy Group, Max-Planck Institut für Molekulare Genetik, Berlin, Germany
| | - Jan Giesebrecht
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Frank Noé
- Department of Mathematics, Computer Science and Bioinformatics, Freie Universität Berlin, Berlin, Germany
| | - Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2600, Australia
| | - Klaus Peter Hofmann
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
- Zentrum für Biophysik und Bioinformatik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Christian M T Spahn
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Martin Heck
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
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Qureshi BM, Behrmann E, Schöneberg J, Loerke J, Bürger J, Mielke T, Giesebrecht J, Noé F, Hofmann KP, Spahn CMT, Heck M. Asymmetric properties of rod cGMP Phosphodiesterase 6 (PDE6): structural and functional analysis. BMC Pharmacol Toxicol 2015. [PMCID: PMC4565112 DOI: 10.1186/2050-6511-16-s1-a76] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
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Budkevich TV, Giesebrecht J, Behrmann E, Loerke J, Ramrath DJF, Mielke T, Ismer J, Hildebrand PW, Tung CS, Nierhaus KH, Sanbonmatsu KY, Spahn CMT. Regulation of the mammalian elongation cycle by subunit rolling: a eukaryotic-specific ribosome rearrangement. Cell 2014; 158:121-31. [PMID: 24995983 DOI: 10.1016/j.cell.2014.04.044] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 02/24/2014] [Accepted: 04/18/2014] [Indexed: 11/15/2022]
Abstract
The extent to which bacterial ribosomes and the significantly larger eukaryotic ribosomes share the same mechanisms of ribosomal elongation is unknown. Here, we present subnanometer resolution cryoelectron microscopy maps of the mammalian 80S ribosome in the posttranslocational state and in complex with the eukaryotic eEF1A⋅Val-tRNA⋅GMPPNP ternary complex, revealing significant differences in the elongation mechanism between bacteria and mammals. Surprisingly, and in contrast to bacterial ribosomes, a rotation of the small subunit around its long axis and orthogonal to the well-known intersubunit rotation distinguishes the posttranslocational state from the classical pretranslocational state ribosome. We term this motion "subunit rolling." Correspondingly, a mammalian decoding complex visualized in substates before and after codon recognition reveals structural distinctions from the bacterial system. These findings suggest how codon recognition leads to GTPase activation in the mammalian system and demonstrate that in mammalia subunit rolling occurs during tRNA selection.
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Affiliation(s)
- Tatyana V Budkevich
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; Max-Planck Institut für Molekulare Genetik, Abteilung Vingron, AG Ribosomen, 14195 Berlin, Ihnestraße 73, Germany; Institute of Molecular Biology and Genetics, Group of Protein Biosynthesis, 03143 Kiev, Ukraine
| | - Jan Giesebrecht
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Elmar Behrmann
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Justus Loerke
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - David J F Ramrath
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Thorsten Mielke
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; Max-Planck Institut für Molekulare Genetik, UltraStrukturNetzwerk, 14195 Berlin, Ihnestraße 73, Germany
| | - Jochen Ismer
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Peter W Hildebrand
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Chang-Shung Tung
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, MK710, Los Alamos, NM 87545, USA
| | - Knud H Nierhaus
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; Max-Planck Institut für Molekulare Genetik, Abteilung Vingron, AG Ribosomen, 14195 Berlin, Ihnestraße 73, Germany
| | - Karissa Y Sanbonmatsu
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, MK710, Los Alamos, NM 87545, USA; New Mexico Consortium, 4200 West Jemez Road, Suite 301, Los Alamos, New Mexico 87544, USA
| | - Christian M T Spahn
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
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Abstract
As the resolution of cryo-EM reconstructions has improved to the subnanometer range, conformational and compositional heterogeneity have become increasing problems in cryo-EM, limiting the resolution of reconstructions. Since further purification is not feasible, the presence of several conformational states of ribosomal complexes in thermodynamic equilibrium requires methods for separating these states in silico. We describe a procedure for generating subnanometer resolution cryo-EM structures from large sets of projection images of ribosomal complexes. The incremental K-means-like method of unsupervised 3D sorting discussed here allows separation of classes in the dataset by exploiting intrinsic divisions in the data. The classification procedure is described in detail and its effectiveness is illustrated using current examples from our work. Through a good separation of conformational modes, higher resolution reconstructions can be calculated. This increases information gained from single states, while exploiting the coexistence of multiple states to gather comprehensive mechanistic insight into biological processes like ribosomal translocation.
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Affiliation(s)
- Justus Loerke
- Institut für medizinische Physik und Biophysik, Charité, Universitätsmedizin Berlin, Berlin, Germany
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Schuette JC, Murphy FV, Kelley AC, Weir JR, Giesebrecht J, Connell SR, Loerke J, Mielke T, Zhang W, Penczek PA, Ramakrishnan V, Spahn CMT. GTPase activation of elongation factor EF-Tu by the ribosome during decoding. EMBO J 2009; 28:755-65. [PMID: 19229291 PMCID: PMC2666022 DOI: 10.1038/emboj.2009.26] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Accepted: 01/14/2009] [Indexed: 11/09/2022] Open
Abstract
We have used single-particle reconstruction in cryo-electron microscopy to determine a structure of the Thermus thermophilus ribosome in which the ternary complex of elongation factor Tu (EF-Tu), tRNA and guanine nucleotide has been trapped on the ribosome using the antibiotic kirromycin. This represents the state in the decoding process just after codon recognition by tRNA and the resulting GTP hydrolysis by EF-Tu, but before the release of EF-Tu from the ribosome. Progress in sample purification and image processing made it possible to reach a resolution of 6.4 A. Secondary structure elements in tRNA, EF-Tu and the ribosome, and even GDP and kirromycin, could all be visualized directly. The structure reveals a complex conformational rearrangement of the tRNA in the A/T state and the interactions with the functionally important switch regions of EF-Tu crucial to GTP hydrolysis. Thus, the structure provides insights into the molecular mechanism of signalling codon recognition from the decoding centre of the 30S subunit to the GTPase centre of EF-Tu.
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Affiliation(s)
- Jan-Christian Schuette
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Berlin, Germany
| | - Frank V Murphy
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Ann C Kelley
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - John R Weir
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Jan Giesebrecht
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Berlin, Germany
| | - Sean R Connell
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Berlin, Germany
| | - Justus Loerke
- UltraStrukturNetzwerk, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Thorsten Mielke
- UltraStrukturNetzwerk, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Wei Zhang
- Department of Biochemistry and Molecular Biology, The University of Texas—Houston Medical School, Houston, TX, USA
| | - Pawel A Penczek
- Department of Biochemistry and Molecular Biology, The University of Texas—Houston Medical School, Houston, TX, USA
| | - V Ramakrishnan
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Christian M T Spahn
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Berlin, Germany
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Sixt SU, Adamzik M, Spyrka D, Saul B, Hakenbeck J, Wohlschlaeger J, Costabel U, Kloss A, Giesebrecht J, Dahlmann B, Peters J. Alveolar extracellular 20S proteasome in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2009; 179:1098-106. [PMID: 19286628 DOI: 10.1164/rccm.200802-199oc] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Repair mechanisms resulting in alveolar protein degradation in acute respiratory distress syndrome (ARDS) are largely unknown. OBJECTIVES To test whether the 20S proteasome is present and functional in the alveolar space in patients with ARDS. METHODS Proteasome antigenic concentration in bronchoalveolar lavage (BAL) supernatants was measured by ELISA in patients with ARDS (n = 64), acute lung injury (ALI) (n = 8), sarcoidosis (n = 13), and in healthy subjects (n = 8). Cleavage of specific fluorogenic substrates (+/-epoxomicin), I(125) albumin degradation rate, and gel filtration were used to quantify and characterize proteasomal activity. The presence of proteasomes was confirmed independently by electron microscopic techniques. MEASUREMENTS AND MAIN RESULTS Proteasome concentrations in patients with ARDS were markedly increased (1,069 +/- 1,194 ng/ml) in comparison to healthy subjects (60.8 +/- 49.8; P < 0.001), ALI (154 +/- 43; P = 0.006), and sarcoidosis (97.6 +/- 42.2; P = 0.037). All fluorogenic substrates were hydrolyzed (Suc-LLVY-AMC, 3.6 +/- 8.8 pkat/mg; BZ-VGR-AMC, 1.8 +/- 3.1; Suc-LLE-AMC, 1 +/- 1.7) by BAL supernatants of patients with ARDS, with inhibition by epoxomicin (P = 0.0001), and the majority of proteolytic activity was detected in BAL supernatant. Maximum hydrolyzing activity occurred at 660 kD and 20S proteasome was seen microscopically after purification and being released by pneumocytes type II. Proteasomal activity and albumin degradation rate in patients with ARDS were approximately 17-fold lower than in healthy subjects. Proteasomal activity in normal BAL was inhibited by BAL aliquots from patients with ARDS but not by denatured BAL, and returned to normal by purification. CONCLUSIONS For the first time, we identified extracellular, biologically active 20S proteasome in the alveolar space of patients with ARDS in concentrations much higher than in normal subjects or in those with ALI.
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Affiliation(s)
- Stephan Urs Sixt
- Klinik für Anästhesiologie und Intensivmedizin, Universitätsklinikum Essen, Hufelandstrasse 55, Essen, Germany.
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Connell SR, Takemoto C, Wilson DN, Wang H, Murayama K, Terada T, Shirouzu M, Rost M, Schüler M, Giesebrecht J, Dabrowski M, Mielke T, Fucini P, Yokoyama S, Spahn CMT. Structural basis for interaction of the ribosome with the switch regions of GTP-bound elongation factors. Mol Cell 2007; 25:751-64. [PMID: 17349960 DOI: 10.1016/j.molcel.2007.01.027] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 12/24/2006] [Accepted: 01/23/2007] [Indexed: 10/23/2022]
Abstract
Elongation factor G (EF-G) catalyzes tRNA translocation on the ribosome. Here a cryo-EM reconstruction of the 70S*EF-G ribosomal complex at 7.3 A resolution and the crystal structure of EF-G-2*GTP, an EF-G homolog, at 2.2 A resolution are presented. EF-G-2*GTP is structurally distinct from previous EF-G structures, and in the context of the cryo-EM structure, the conformational changes are associated with ribosome binding and activation of the GTP binding pocket. The P loop and switch II approach A2660-A2662 in helix 95 of the 23S rRNA, indicating an important role for these conserved bases. Furthermore, the ordering of the functionally important switch I and II regions, which interact with the bound GTP, is dependent on interactions with the ribosome in the ratcheted conformation. Therefore, a network of interaction with the ribosome establishes the active GTP conformation of EF-G and thus facilitates GTP hydrolysis and tRNA translocation.
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Affiliation(s)
- Sean R Connell
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Ziegelstrasse 5-9, 10117 Berlin, Germany
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Schüler M, Connell SR, Lescoute A, Giesebrecht J, Dabrowski M, Schroeer B, Mielke T, Penczek PA, Westhof E, Spahn CMT. Structure of the ribosome-bound cricket paralysis virus IRES RNA. Nat Struct Mol Biol 2006; 13:1092-6. [PMID: 17115051 DOI: 10.1038/nsmb1177] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Accepted: 10/31/2006] [Indexed: 02/05/2023]
Abstract
Internal ribosome entry sites (IRESs) facilitate an alternative, end-independent pathway of translation initiation. A particular family of dicistroviral IRESs can assemble elongation-competent 80S ribosomal complexes in the absence of canonical initiation factors and initiator transfer RNA. We present here a cryo-EM reconstruction of a dicistroviral IRES bound to the 80S ribosome. The resolution of the cryo-EM reconstruction, in the subnanometer range, allowed the molecular structure of the complete IRES in its active, ribosome-bound state to be solved. The structure, harboring three pseudoknot-containing domains, each with a specific functional role, shows how defined elements of the IRES emerge from a compactly folded core and interact with the key ribosomal components that form the A, P and E sites, where tRNAs normally bind. Our results exemplify the molecular strategy for recruitment of an IRES and reveal the dynamic features necessary for internal initiation.
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Affiliation(s)
- Martin Schüler
- Institut für Medizinische Physik und Biophysik, Charite-Universitätsmedizin Berlin, Ziegelstrasse 5-9, 10117-Berlin, Germany
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Stohwasser R, Salzmann U, Giesebrecht J, Kloetzel PM, Holzhütter HG. Kinetic evidences for facilitation of peptide channelling by the proteasome activator PA28. Eur J Biochem 2000; 267:6221-30. [PMID: 11012676 DOI: 10.1046/j.1432-1327.2000.01706.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The activation kinetics of constitutive and IFNgamma-stimulated 20S proteasomes obtained with homomeric (recPA28alpha, recPA28beta) and heteromeric (recPA28alphabeta) forms of recombinant 11S regulator PA28 was analysed by means of kinetic modelling. The activation curves obtained with increasing concentrations of the individual PA28 subunits (RecP28alpha/RecP28beta/RecP28alpha + RecP28beta) exhibit biphasic characteristics which can be attributed to a low-level activation by PA28 monomers and full proteasome activation by assembled activator complexes. The dissociation constants do not reveal significant differences between the constitutive and the immunoproteasome. Intriguingly, the affinity of the proteasome towards the recPA28alphabeta complex is about two orders of magnitude higher than towards the homomeric PA28alpha and PA28beta complexes. Striking similarities can been revealed in the way how PA28 mediates the kinetics of latent proteasomes with respect to three different fluorogenic peptides probing the chymotrypsin-like, trypsin-like and peptidylglutamyl-peptide hydrolyzing like activity: (a) positive cooperativity disappears as indicated by a lack of sigmoid initial parts of the kinetic curves, (b) substrate affinity is increased, whereby (c), the maximal activity remains virtually constant. As these kinetic features are independent of the peptide substrates, we conclude that PA28 exerts its activating influence on the proteasome by enhancing the uptake (and release) of shorter peptides.
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Affiliation(s)
- R Stohwasser
- Deutsches Institut für Ernährungsforschung, Abt. Präventiv-Medizinische Lebensmittelforschung, Bergholz-Rehbrücke, Bundesrepublik Deutschland.
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Stohwasser R, Giesebrecht J, Kraft R, Müller EC, Häusler KG, Kettenmann H, Hanisch UK, Kloetzel PM. Biochemical analysis of proteasomes from mouse microglia: induction of immunoproteasomes by interferon-gamma and lipopolysaccharide. Glia 2000; 29:355-65. [PMID: 10652445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The 20S proteasome is a multicatalytic threonine protease and serves to process peptides that are subsequently presented as antigenic epitopes by MHC class I molecules. In the brain, microglial cells are the major antigen presenting cells and they respond sensitive to pathologic events. We used cultured mouse microglia and a microglial cell line, the BV-2 line, as a model to study the correlation between microglial activation parameters and structural plasticity of the 20S/26S proteasome. Lipopolysaccharide (LPS)- or interferon-gamma (IFN-gamma)-stimulated microglia or BV-2 cells exhibit properties of activated microglia such as high levels of TNFalpha and IL-6 release. In response to IFN-gamma or LPS, three constitutive beta subunits (beta1/Delta, beta2/MC14, beta5/MB1) were replaced by the immunoproteasome subunits ibeta1/LMP2, ibeta2/MECL-1, and ibeta5/LMP7, indicating that activated microglia adapts its proteasomal subunit composition to the requirements of an optimized MHC class I epitope processing. Induction of immunoproteasomes in BV-2 cells was solely provoked by IFN-gamma, but not by LPS. Moreover, LPS (but not IFN-gamma) triggered the expression of a novel protein of approximately 50 kD as part of the proteasome activator PA700, that is the substrate-recognizing and unfolding unit of the 26S proteasome. These results indicate that both the 20S core protease as well as the proteasome activator PA700 are targets of modulatory subunit replacements or transient association of regulatory components in the course of microglial activation.
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Affiliation(s)
- R Stohwasser
- Paul-Ehrlich-Center of Experimental Medicine, Humboldt University Medical School, Institute of Biochemistry, Berlin, Germany.
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Stohwasser R, Giesebrecht J, Kraft R, M�ller EC, H�usler KG, Kettenmann H, Hanisch UK, Kloetzel PM. Biochemical analysis of proteasomes from mouse microglia: Induction of immunoproteasomes by interferon-? and lipopolysaccharide. Glia 2000. [DOI: 10.1002/(sici)1098-1136(20000215)29:4<355::aid-glia6>3.0.co;2-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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