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Sun H, Li M, Li Y, Zheng N, Li J, Li X, Liu Y, Ji Q, Zhou L, Su J, Huang W, Liu Z, Liu P, Zou L. Gastrodin Improves the Activity of the Ubiquitin-Proteasome System and the Autophagy-Lysosome Pathway to Degrade Mutant Huntingtin. Int J Mol Sci 2024; 25:7709. [PMID: 39062952 PMCID: PMC11277377 DOI: 10.3390/ijms25147709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Revised: 07/09/2024] [Accepted: 07/11/2024] [Indexed: 07/28/2024] Open
Abstract
Gastrodin (GAS) is the main chemical component of the traditional Chinese herb Gastrodia elata (called "Tianma" in Chinese), which has been used to treat neurological conditions, including headaches, epilepsy, stroke, and memory loss. To our knowledge, it is unclear whether GAS has a therapeutic effect on Huntington's disease (HD). In the present study, we evaluated the effect of GAS on the degradation of mutant huntingtin protein (mHtt) by using PC12 cells transfected with N-terminal mHtt Q74. We found that 0.1-100 μM GAS had no effect on the survival rate of Q23 and Q74 PC12 cells after 24-48 h of incubation. The ubiquitin-proteasome system (UPS) is the main system that clears misfolded proteins in eukaryotic cells. Mutated Htt significantly upregulated total ubiquitinated protein (Ub) expression, decreased chymotrypsin-like, trypsin-like and caspase-like peptidase activity, and reduced the colocalization of the 20S proteasome with mHtt. GAS (25 μM) attenuated all of the abovementioned pathological changes, and the regulatory effect of GAS on mHtt was found to be abolished by MG132, a proteasome inhibitor. The autophagy-lysosome pathway (ALP) is another system for misfolded protein degradation. Although GAS downregulated the expression of autophagy markers (LC3II and P62), it increased the colocalization of LC3II with lysosomal associated membrane protein 1 (LAMP1), which indicates that ALP was activated. Moreover, GAS prevented mHtt-induced neuronal damage in PC12 cells. GAS has a selective effect on mHtt in Q74 PC12 cells and has no effect on Q23 and proteins encoded by other genes containing long CAGs, such as Rbm33 (10 CAG repeats) and Hcn1 (>30 CAG repeats). Furthermore, oral administration of 100 mg/kg GAS increased grip strength and attenuated mHtt aggregates in B6-hHTT130-N transgenic mice. This is a high dose (100 mg/kg GAS) when compared with experiments on HD mice with other small molecules. We will design more doses to evaluate the dose-response relationship of the inhibition effect of GAS on mHtt in our next study. In summary, GAS can promote the degradation of mHtt by activating the UPS and ALP, making it a potential therapeutic agent for HD.
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Affiliation(s)
- He Sun
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Miao Li
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Yunling Li
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (Y.L.); (W.H.)
| | - Na Zheng
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Jiaxin Li
- Department of Bioengineering, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China;
| | - Xiang Li
- Department of Medicinal Chemistry, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China;
| | - Yingying Liu
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Qianyun Ji
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Liping Zhou
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Jingwen Su
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China;
| | - Wanxu Huang
- Wuya College of Innovation, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (Y.L.); (W.H.)
| | - Zhongbo Liu
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China;
| | - Peng Liu
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
| | - Libo Zou
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; (H.S.); (M.L.); (N.Z.); (Y.L.); (Q.J.); (L.Z.)
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Lyu L, Chen Z, McCarty N. TRIM44 links the UPS to SQSTM1/p62-dependent aggrephagy and removing misfolded proteins. Autophagy 2021; 18:783-798. [PMID: 34382902 PMCID: PMC9037492 DOI: 10.1080/15548627.2021.1956105] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Until recently, the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy were considered to be two independent systems that target proteins for degradation by proteasomes or via lysosomes, respectively. Here, we report that TRIM44 (tripartite motif containing 44) is a novel link that connects the UPS system with the autophagy degradation pathway. Suppressing the UPS degradation pathway leads to TRIM44 upregulation, which further promotes aggregated protein clearance through the binding of K48 ubiquitin chains on proteins. TRIM44 expression activates autophagy via promoting SQSTM1/p62 oligomerization, which rapidly increases the rate of aggregate protein removal. Overall, our data reveal that TRIM44 is a newly identified link between the UPS system and the autophagy pathway. Delineating the cross-talk between these two degradation pathways may reveal new mechanisms of targeting aggregate-prone diseases, such as cancer and neurodegenerative disease. Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; ATG5: autophagy related 5; BB: B-box domain; BECN1: beclin1; BM: bone marrow; CC: coiled-coil domain; CFTR: cystic fibrosis transmembrane conductance regulator; CON: control; CQ: chloroquine; DOX: doxycycline; DSP: dithiobis(succinimidly propionate); ER: endoplasmic reticulum; FI: fluorescence intensity; FL: full length; HIF1A/HIF-1#x3B1;: hypoxia inducible factor 1 subunit alpha; HSC: hematopoietic stem cells; HTT: huntingtin; KD: knockdown; KD-CON: knockdown construct control; MM: multiple myeloma; MTOR: mechanistic target of rapamycin kinase; NP-40: nonidet P-40; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; OE: overexpression; OE-CON: overexpression construct control; PARP: poly (ADP-ribose) polymerase; SDS: sodium dodecyl sulfate; SQSTM1/p62: sequestosome 1; Tet-on: tetracycline; TRIM44: tripartite motif containing 44; UPS: ubiquitin-proteasome system; ZF: zinc-finger
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Affiliation(s)
- Lin Lyu
- Center for Stem Cell and Regenerative Disease, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM), the University of Texas-Health Science Center at Houston, Houston, Texas, USA
| | - Zheng Chen
- Center for Stem Cell and Regenerative Disease, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM), the University of Texas-Health Science Center at Houston, Houston, Texas, USA
| | - Nami McCarty
- Center for Stem Cell and Regenerative Disease, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM), the University of Texas-Health Science Center at Houston, Houston, Texas, USA
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Son M, Kaspar J, Ahn SJ, Burne RA, Hagen SJ. Threshold regulation and stochasticity from the MecA/ClpCP proteolytic system in Streptococcus mutans competence. Mol Microbiol 2018; 110:914-930. [PMID: 29873131 PMCID: PMC6281771 DOI: 10.1111/mmi.13992] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2018] [Indexed: 12/28/2022]
Abstract
Many bacterial species use the MecA/ClpCP proteolytic system to block entry into genetic competence. In Streptococcus mutans, MecA/ClpCP degrades ComX (also called SigX), an alternative sigma factor for the comY operon and other late competence genes. Although the mechanism of MecA/ClpCP has been studied in multiple Streptococcus species, its role within noisy competence pathways is poorly understood. S. mutans competence can be triggered by two different peptides, CSP and XIP, but it is not known whether MecA/ClpCP acts similarly for both stimuli, how it affects competence heterogeneity, and how its regulation is overcome. We have studied the effect of MecA/ClpCP on the activation of comY in individual S. mutans cells. Our data show that MecA/ClpCP is active under both XIP and CSP stimulation, that it provides threshold control of comY, and that it adds noise in comY expression. Our data agree quantitatively with a model in which MecA/ClpCP prevents adventitious entry into competence by sequestering or intercepting low levels of ComX. Competence is permitted when ComX levels exceed a threshold, but cell‐to‐cell heterogeneity in MecA levels creates variability in that threshold. Therefore, MecA/ClpCP provides a stochastic switch, located downstream of the already noisy comX, that enhances phenotypic diversity.
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Affiliation(s)
- M Son
- Department of Physics, University of Florida, Gainesville, FL 32611, USA
| | - J Kaspar
- Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA
| | - S J Ahn
- Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA
| | - R A Burne
- Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA
| | - S J Hagen
- Department of Physics, University of Florida, Gainesville, FL 32611, USA
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Cherak SJ, Turner RJ. Assembly pathway of a bacterial complex iron sulfur molybdoenzyme. Biomol Concepts 2018; 8:155-167. [PMID: 28688222 DOI: 10.1515/bmc-2017-0011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 05/10/2017] [Indexed: 11/15/2022] Open
Abstract
Protein folding and assembly into macromolecule complexes within the living cell are complex processes requiring intimate coordination. The biogenesis of complex iron sulfur molybdoenzymes (CISM) requires use of a system specific chaperone - a redox enzyme maturation protein (REMP) - to help mediate final folding and assembly. The CISM dimethyl sulfoxide (DMSO) reductase is a bacterial oxidoreductase that utilizes DMSO as a final electron acceptor for anaerobic respiration. The REMP DmsD strongly interacts with DMSO reductase to facilitate folding, cofactor-insertion, subunit assembly and targeting of the multi-subunit enzyme prior to membrane translocation and final assembly and maturation into a bioenergetic catalytic unit. In this article, we discuss the biogenesis of DMSO reductase as an example of the participant network for bacterial CISM maturation pathways.
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Liu J, Francis LI, Jonas K, Laub MT, Chien P. ClpAP is an auxiliary protease for DnaA degradation in Caulobacter crescentus. Mol Microbiol 2016; 102:1075-1085. [PMID: 27667502 DOI: 10.1111/mmi.13537] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2016] [Indexed: 11/28/2022]
Abstract
The Clp family of proteases is responsible for controlling both stress responses and normal growth. In Caulobacter crescentus, the ClpXP protease is essential and drives cell cycle progression through adaptor-mediated degradation. By contrast, the physiological role for the ClpAP protease is less well understood with only minor growth defects previously reported for ΔclpA cells. Here, we show that ClpAP plays an important role in controlling chromosome content and cell fitness during extended growth. Cells lacking ClpA accumulate aberrant numbers of chromosomes upon prolonged growth suggesting a defect in replication control. Levels of the replication initiator DnaA are elevated in ΔclpA cells and degradation of DnaA is more rapid in cells lacking the ClpA inhibitor ClpS. Consistent with this observation, ClpAP degrades DnaA in vitro while ClpS inhibits this degradation. In cells lacking Lon, the protease previously shown to degrade DnaA in Caulobacter, ClpA overexpression rescues defects in fitness and restores degradation of DnaA. Finally, we show that cells lacking ClpA are particularly sensitive to inappropriate increases in DnaA activity. Our work demonstrates an unexpected effect of ClpAP in directly regulating replication through degradation of DnaA and expands the functional role of ClpAP in Caulobacter.
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Affiliation(s)
- Jing Liu
- Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Laura I Francis
- Department of Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Kristina Jonas
- Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael T Laub
- Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Peter Chien
- Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
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Burmann BM, Hiller S. Chaperones and chaperone-substrate complexes: Dynamic playgrounds for NMR spectroscopists. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2015; 86-87:41-64. [PMID: 25919198 DOI: 10.1016/j.pnmrs.2015.02.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/19/2015] [Accepted: 02/19/2015] [Indexed: 05/20/2023]
Abstract
The majority of proteins depend on a well-defined three-dimensional structure to obtain their functionality. In the cellular environment, the process of protein folding is guided by molecular chaperones to avoid misfolding, aggregation, and the generation of toxic species. To this end, living cells contain complex networks of molecular chaperones, which interact with substrate polypeptides by a multitude of different functionalities: transport them towards a target location, help them fold, unfold misfolded species, resolve aggregates, or deliver them towards a proteolysis machinery. Despite the availability of high-resolution crystal structures of many important chaperones in their substrate-free apo forms, structural information about how substrates are bound by chaperones and how they are protected from misfolding and aggregation is very sparse. This lack of information arises from the highly dynamic nature of chaperone-substrate complexes, which so far has largely hindered their crystallization. This highly dynamic nature makes chaperone-substrate complexes good targets for NMR spectroscopy. Here, we review the results achieved by NMR spectroscopy to understand chaperone function in general and details of chaperone-substrate interactions in particular. We assess the information content and applicability of different NMR techniques for the characterization of chaperones and chaperone-substrate complexes. Finally, we highlight three recent studies, which have provided structural descriptions of chaperone-substrate complexes at atomic resolution.
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Affiliation(s)
- Björn M Burmann
- Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland.
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Base-CP proteasome can serve as a platform for stepwise lid formation. Biosci Rep 2015; 35:BSR20140173. [PMID: 26182356 PMCID: PMC4438304 DOI: 10.1042/bsr20140173] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 01/26/2015] [Indexed: 12/14/2022] Open
Abstract
26S proteasome, a major regulatory protease in eukaryotes, consists of a 20S proteolytic core particle (CP) capped by a 19S regulatory particle (RP). The 19S RP is divisible into base and lid sub-complexes. Even within the lid, subunits have been demarcated into two modules: module 1 (Rpn5, Rpn6, Rpn8, Rpn9 and Rpn11), which interacts with both CP and base sub-complexes and module 2 (Rpn3, Rpn7, Rpn12 and Rpn15) that is attached mainly to module 1. We now show that suppression of RPN11 expression halted lid assembly yet enabled the base and 20S CP to pre-assemble and form a base-CP. A key role for Regulatory particle non-ATPase 11 (Rpn11) in bridging lid module 1 and module 2 subunits together is inferred from observing defective proteasomes in rpn11–m1, a mutant expressing a truncated form of Rpn11 and displaying mitochondrial phenotypes. An incomplete lid made up of five module 1 subunits attached to base-CP was identified in proteasomes isolated from this mutant. Re-introducing the C-terminal portion of Rpn11 enabled recruitment of missing module 2 subunits. In vitro, module 1 was reconstituted stepwise, initiated by Rpn11–Rpn8 heterodimerization. Upon recruitment of Rpn6, the module 1 intermediate was competent to lock into base-CP and reconstitute an incomplete 26S proteasome. Thus, base-CP can serve as a platform for gradual incorporation of lid, along a proteasome assembly pathway. Identification of proteasome intermediates and reconstitution of minimal functional units should clarify aspects of the inner workings of this machine and how multiple catalytic processes are synchronized within the 26S proteasome holoenzymes. Defective proteasome 19S regulatory particles (RPs) were identified in rpn11f–m1, a proteasomal mutant with mitochondrial phenotypes. The Rpn11 subunit initiates assembly of a five-subunit lid module competent to integrate into pre-assembled base-20S core particle (CP), with subsequent recruitment of remaining lid subunits.
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Nyquist K, Martin A. Marching to the beat of the ring: polypeptide translocation by AAA+ proteases. Trends Biochem Sci 2013; 39:53-60. [PMID: 24316303 DOI: 10.1016/j.tibs.2013.11.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 11/28/2022]
Abstract
ATP-dependent proteases exist in all cells and are crucial regulators of the proteome. These machines consist of a hexameric, ring-shaped motor responsible for engaging, unfolding, and translocating protein substrates into an associated peptidase for degradation. Here, we discuss recent work that has established how the six motor subunits coordinate their ATP-hydrolysis and translocation activities. The closed topology of the ring and the rigidity of subunit/subunit interfaces cause conformational changes within a single subunit to drive motions in other subunits of the hexamer. This structural effect generates allostery between the ATP-binding sites, leading to a preferred order of binding and hydrolysis events among the motor subunits as well as a unique biphasic mechanism of translocation.
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Affiliation(s)
- Kristofor Nyquist
- QB3 Institute, University of California, Berkeley, CA 94720, USA; Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | - Andreas Martin
- QB3 Institute, University of California, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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Redelberger D, Genest O, Arabet D, Méjean V, Ilbert M, Iobbi-Nivol C. Quality control of a molybdoenzyme by the Lon protease. FEBS Lett 2013; 587:3935-42. [PMID: 24211448 DOI: 10.1016/j.febslet.2013.10.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 10/25/2013] [Accepted: 10/28/2013] [Indexed: 01/20/2023]
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Roberts DM, Personne Y, Ollinger J, Parish T. Proteases in Mycobacterium tuberculosis pathogenesis: potential as drug targets. Future Microbiol 2013; 8:621-31. [PMID: 23642117 DOI: 10.2217/fmb.13.25] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
TB is still a major global health problem causing over 1 million deaths per year. An increasing problem of drug resistance in the causative agent, Mycobacterium tuberculosis, as well as problems with the current lengthy and complex treatment regimens, lends urgency to the need to develop new antitubercular agents. Proteases have been targeted for therapy in other infections, most notably these have been successful as antiviral agents in the treatment of HIV infection. M. tuberculosis has a number of proteases with good potential as novel drug targets and developing drugs against these should result in agents that are effective against drug-resistant and drug-sensitive strains. In this review, the authors summarize the current status of proteases with potential as drug targets in this pathogen, particularly focusing on proteases involved in protein secretion (signal peptidases LepB and LspA), protein degradation and turnover (ClpP and the proteasome) and virulence (mycosins and HtrA).
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Affiliation(s)
- David M Roberts
- TB Discovery Research, Infectious Disease Research Institute, Seattle, WA, USA
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Ciechanover A, Stanhill A. The complexity of recognition of ubiquitinated substrates by the 26S proteasome. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:86-96. [PMID: 23872423 DOI: 10.1016/j.bbamcr.2013.07.007] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/02/2013] [Accepted: 07/08/2013] [Indexed: 02/03/2023]
Abstract
The Ubiquitin Proteasome System (UPS) was discovered in two steps. Initially, APF-1 (ATP-dependent proteolytic Factor 1) later identified as ubiquitin (Ub), a hitherto known protein of unknown function, was found to covalently modify proteins. This modification led to degradation of the tagged protein by - at that time - an unknown protease. This was followed later by the identification of the 26S proteasome complex which is composed of a previously identified Multi Catalytic Protease (MCP) and an additional regulatory complex, as the protease that degrades Ub-tagged proteins. While Ub conjugation and proteasomal degradation are viewed as a continued process responsible for most of the regulated proteolysis in the cell, the two processes have also independent roles. In parallel and in the years that followed, the hallmark signal that links the substrate to the proteasome was identified as an internal Lys48-based polyUb chain. However, since these initial findings were described, our understanding of both ends of the process (i.e. Ub-conjugation to proteins, and their recognition and degradation), have advanced significantly. This enabled us to start bridging the ends of this continuous process which suffered until lately from limited structural data regarding the 26S proteasomal architecture and the structure and diversity of the Ub chains. These missing pieces are of great importance because the link between ubiquitination and proteasomal processing is subject to numerous regulatory steps and are found to function improperly in several pathologies. Recently, the molecular architecture of the 26S proteasome was resolved in great detail, enabling us to address mechanistic questions regarding the various molecular events that polyubiquitinated (polyUb) substrates undergo during binding and processing by the 26S proteasome. In addition, advancement in analytical and synthetic methods enables us to better understand the structure and diversity of the degradation signal. The review summarizes these recent findings and addresses the extrapolated meanings in light of previous reports. Finally, it addresses some of the still remaining questions to be solved in order to obtain a continuous mechanistic view of the events that a substrate undergoes from its initial ubiquitination to proteasomal degradation. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- Aaron Ciechanover
- The David and Janet Polak Cancer and Vascular Biology Research Center, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
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Moitinho-Silva L, Kondo MY, Oliveira LCG, Okamoto DN, Paes JA, Machado MFM, Veronez CL, Motta G, Andrade SS, Juliano MA, Ferreira HB, Juliano L, Gouvea IE. Mycoplasma hyopneumoniae in vitro peptidase activities: identification and cleavage of kallikrein-kinin system-like substrates. Vet Microbiol 2013; 163:264-73. [PMID: 23421966 DOI: 10.1016/j.vetmic.2013.01.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 01/15/2013] [Accepted: 01/17/2013] [Indexed: 01/24/2023]
Abstract
Bacterial proteases are important for metabolic processes and pathogenesis in host organisms. The bacterial swine pathogen Mycoplasma hyopneumoniae has 15 putative protease-encoding genes annotated, but none of them have been functionally characterized. To identify and characterize peptidases that could be relevant for infection of swine hosts, we investigated the peptidase activity present in the pathogenic 7448 strain of M. hyopneumoniae. Combinatorial libraries of fluorescence resonance energy transfer peptides, specific inhibitors and pH profiling were used to screen and characterize endopeptidase, aminopeptidase and carboxypeptidase activities in cell lysates. One metalloendopeptidase, one serine endopeptidase, and one aminopeptidase were detected. The detected metalloendopeptidase activity, prominent at neutral and basic pH ranges, was due to a thimet oligopeptidase family member (M3 family), likely an oligoendopeptidase F (PepF), which cleaved the peptide Abz-GFSPFRQ-EDDnp at the F-S bond. A chymotrypsin-like serine endopeptidase activity, possibly a subtilisin-like serine protease, was prominent at higher pH levels, and was characterized by its preference for a Phe residue at the P1 position of the substrate. The aminopeptidase P (APP) activity showed a similar profile to that of human membrane-bound APP. Genes coding for these three peptidases were identified and their transcription was confirmed in the 7448 strain. Furthermore, M. hyopneumoniae cell lysate peptidases showed effects on kallikrein-kinin system-like substrates, such as bradykinin-derived substrates and human high molecular weight kininogen. The M. hyopneumoniae peptidase activities, here characterized for the first time, may be important for bacterial survival strategies and thus represent possible targets for drug development against M. hyopneumoniae swine infections.
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Affiliation(s)
- Lucas Moitinho-Silva
- Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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Kraut DA, Matouschek A. Proteasomal degradation from internal sites favors partial proteolysis via remote domain stabilization. ACS Chem Biol 2011; 6:1087-95. [PMID: 21815694 DOI: 10.1021/cb2002285] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The ubiquitin-proteasome system controls the concentrations of hundreds of regulatory proteins and removes misfolded and damaged proteins in eukaryotic cells. The proteasome recognizes ubiquitinated proteins and then engages its substrates at unstructured initiation regions. After initiation, it proceeds along the polypeptide chain, unraveling folded domains sequentially and degrading the protein completely. In vivo the proteasome can, and likely often does, initiate degradation at internal sites within its substrates, but it is not known how this affects the outcome of the degradation reaction. Here we find that domains flanking the initiation region can protect each other against degradation without interacting directly. The magnitude of this effect is related to the stability of both domains and can be tuned from complete degradation to complete protection of one domain. Partial proteasomal degradation has been observed in the cell in three signaling pathways and is associated with internal initiation. Thus, the basic biochemical mechanism of remote stabilization of protein domains is important in proteasome biology.
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Affiliation(s)
- Daniel A. Kraut
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Andreas Matouschek
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
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Abstract
AAA+ family proteolytic machines (ClpXP, ClpAP, ClpCP, HslUV, Lon, FtsH, PAN/20S, and the 26S proteasome) perform protein quality control and are used in regulatory circuits in all cells. These machines contain a compartmental protease, with active sites sequestered in an interior chamber, and a hexameric ring of AAA+ ATPases. Substrate proteins are tethered to the ring, either directly or via adaptor proteins. An unstructured region of the substrate is engaged in the axial pore of the AAA+ ring, and cycles of ATP binding/hydrolysis drive conformational changes that create pulses of pulling that denature the substrate and translocate the unfolded polypeptide through the pore and into the degradation chamber. Here, we review our current understanding of the molecular mechanisms of substrate recognition, adaptor function, and ATP-fueled unfolding and translocation. The unfolding activities of these and related AAA+ machines can also be used to disassemble or remodel macromolecular complexes and to resolubilize aggregates.
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Affiliation(s)
- Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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15
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Suskiewicz MJ, Sussman JL, Silman I, Shaul Y. Context-dependent resistance to proteolysis of intrinsically disordered proteins. Protein Sci 2011; 20:1285-97. [PMID: 21574196 DOI: 10.1002/pro.657] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Accepted: 05/05/2011] [Indexed: 01/08/2023]
Abstract
Intrinsically disordered proteins (IDPs), also known as intrinsically unstructured proteins (IUPs), lack a well-defined 3D structure in vitro and, in some cases, also in vivo. Here, we discuss the question of proteolytic sensitivity of IDPs, with a view to better explaining their in vivo characteristics. After an initial assessment of the status of IDPs in vivo, we briefly survey the intracellular proteolytic systems. Subsequently, we discuss the evidence for IDPs being inherently sensitive to proteolysis. Such sensitivity would not, however, result in enhanced degradation if the protease-sensitive sites were sequestered. Accordingly, IDP access to and degradation by the proteasome, the major proteolytic complex within eukaryotic cells, are discussed in detail. The emerging picture appears to be that IDPs are inherently sensitive to proteasomal degradation along the lines of the "degradation by default" model. However, available data sets of intracellular protein half-lives suggest that intrinsic disorder does not imply a significantly shorter half-life. We assess the power of available systemic half-life measurements, but also discuss possible mechanisms that could protect IDPs from intracellular degradation. Finally, we discuss the relevance of the proteolytic sensitivity of IDPs to their function and evolution.
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Affiliation(s)
- Marcin J Suskiewicz
- The Israel Structural Proteomics Center, Weizmann Institute of Science, Rehovot, Israel
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16
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Wang F, Mei Z, Qi Y, Yan C, Hu Q, Wang J, Shi Y. Structure and mechanism of the hexameric MecA-ClpC molecular machine. Nature 2011; 471:331-5. [PMID: 21368759 DOI: 10.1038/nature09780] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 12/22/2010] [Indexed: 11/09/2022]
Abstract
Regulated proteolysis by ATP-dependent proteases is universal in all living cells. Bacterial ClpC, a member of the Clp/Hsp100 family of AAA+ proteins (ATPases associated with diverse cellular activities) with two nucleotide-binding domains (D1 and D2), requires the adaptor protein MecA for activation and substrate targeting. The activated, hexameric MecA-ClpC molecular machine harnesses the energy of ATP binding and hydrolysis to unfold specific substrate proteins and translocate the unfolded polypeptide to the ClpP protease for degradation. Here we report three related crystal structures: a heterodimer between MecA and the amino domain of ClpC, a heterododecamer between MecA and D2-deleted ClpC, and a hexameric complex between MecA and full-length ClpC. In conjunction with biochemical analyses, these structures reveal the organizational principles behind the hexameric MecA-ClpC complex, explain the molecular mechanisms for MecA-mediated ClpC activation and provide mechanistic insights into the function of the MecA-ClpC molecular machine. These findings have implications for related Clp/Hsp100 molecular machines.
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Affiliation(s)
- Feng Wang
- Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China
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17
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Unfolding and translocation pathway of substrate protein controlled by structure in repetitive allosteric cycles of the ClpY ATPase. Proc Natl Acad Sci U S A 2011; 108:2234-9. [PMID: 21266546 DOI: 10.1073/pnas.1014278108] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clp ATPases are ring-shaped AAA+ motors in the degradation pathway that perform critical actions of unfolding and translocating substrate proteins (SPs) through narrow pores to deliver them to peptidase components. These actions are effected by conserved diaphragm-forming loops found in the central channel of the Clp ATPase hexamer. Conformational changes, that take place in the course of repetitive ATP-driven cycles, result in mechanical forces applied by the central channel loops onto the SP. We use coarse-grained simulations to elucidate allostery-driven mechanisms of unfolding and translocation of a tagged four-helix bundle protein by the ClpY ATPase. Unfolding is initiated at the tagged C-terminal region via an obligatory intermediate. The resulting nonnative conformation is competent for translocation, which proceeds on a different time scale than unfolding and involves sharp stepped transitions. Completion of the translocation process requires assistance from the ClpQ peptidase. These mechanisms contrast nonallosteric mechanical unfolding of the SP. In atomic force microscopy experiments, multiple unfolding pathways are available and large mechanical forces are required to unravel the SP relative to those exerted by the central channel loops of ClpY. SP threading through a nonallosteric ClpY nanopore involves simultaneous unfolding and translocation effected by strong pulling forces.
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18
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Sundar S, McGinness KE, Baker TA, Sauer RT. Multiple sequence signals direct recognition and degradation of protein substrates by the AAA+ protease HslUV. J Mol Biol 2010; 403:420-9. [PMID: 20837023 DOI: 10.1016/j.jmb.2010.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/02/2010] [Accepted: 09/03/2010] [Indexed: 11/25/2022]
Abstract
Proteolysis is important for protein quality control and for the proper regulation of many intracellular processes in prokaryotes and eukaryotes. Discerning substrates from other cellular proteins is a key aspect of proteolytic function. The Escherichia coli HslUV protease is a member of a major family of ATP-dependent AAA+ degradation machines. HslU hexamers recognize and unfold native protein substrates and then translocate the polypeptide into the degradation chamber of the HslV peptidase. Although a wealth of structural information is available for this system, relatively little is known about mechanisms of substrate recognition. Here, we demonstrate that mutations in the unstructured N-terminal and C-terminal sequences of two model substrates alter HslUV recognition and degradation kinetics, including changes in V(max). By introducing N- or C-terminal sequences that serve as recognition sites for specific peptide-binding proteins, we show that blocking either terminus of the substrate interferes with HslUV degradation, with synergistic effects when both termini are obstructed. These results support a model in which one terminus of the substrate is tethered to the protease and the other terminus is engaged by the translocation/unfolding machinery in the HslU pore. Thus, degradation appears to consist of discrete steps, which involve the interaction of different terminal sequence signals in the substrate with different receptor sites in the HslUV protease.
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Affiliation(s)
- Shankar Sundar
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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19
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Janska H, Piechota J, Kwasniak M. ATP-dependent proteases in biogenesis and maintenance of plant mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1071-5. [PMID: 20193658 DOI: 10.1016/j.bbabio.2010.02.027] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 02/22/2010] [Accepted: 02/22/2010] [Indexed: 01/02/2023]
Abstract
ATP-dependent proteases from three families have been identified experimentally in Arabidopsis mitochondria: four FtsH proteases (AtFtsH3, AtFtsH4, AtFtsH10, and AtFtsH11), two Lon proteases (AtLon1 and AtLon4), and one Clp protease (AtClpP2 with regulatory subunit AtClpX). In this review we discuss their submitochondrial localization, expression profiles and proposed functions, with special emphasis on their impact on plant growth and development. The best characterized plant mitochondrial ATP-dependent proteases are AtLon1 and AtFtsH4. It has been proposed that AtLon1 is necessary for proper mitochondrial biogenesis during seedling establishment, whereas AtFtsH4 is involved in maintaining mitochondrial homeostasis late in rosette development under short-day photoperiod.
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Affiliation(s)
- Hanna Janska
- Department of Biotechnology, University of Wroclaw, 51-148 Wroclaw, Poland.
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20
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The ubiquitin-interacting motifs of S5a as a unique upstream inhibitor of the 26S proteasome. Biochem Biophys Res Commun 2009; 388:723-6. [DOI: 10.1016/j.bbrc.2009.08.078] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 08/13/2009] [Indexed: 11/19/2022]
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21
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Mei Z, Wang F, Qi Y, Zhou Z, Hu Q, Li H, Wu J, Shi Y. Molecular determinants of MecA as a degradation tag for the ClpCP protease. J Biol Chem 2009; 284:34366-75. [PMID: 19767395 DOI: 10.1074/jbc.m109.053017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulated proteolysis by ATP-dependent proteases is universal in all living cells. In Bacillus subtilis, the degradation of the competence transcription factor ComK is mediated by a ternary complex involving the adaptor protein MecA and the ATP-dependent protease ClpCP. Here we demonstrate that a C-terminal, 98-amino acid domain of MecA (residues 121-218) serves as a non-recycling, degradation tag and targets a variety of fusion proteins to the ClpCP protease for degradation. MecA-(121-218) facilitates productive oligomerization of ClpC, stimulates the ATPase activity of ClpC, and allows the activated ClpC complex to stably associate with ClpP. Importantly, the ClpCP protease undergoes dynamic cycles of assembly and disassembly, which are triggered by association with MecA and the degradation of MecA, respectively.
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Affiliation(s)
- Ziqing Mei
- Ministry of Education Protein Science Laboratory, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
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22
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Sutter M, Striebel F, Damberger FF, Allain FHT, Weber-Ban E. A distinct structural region of the prokaryotic ubiquitin-like protein (Pup) is recognized by the N-terminal domain of the proteasomal ATPase Mpa. FEBS Lett 2009; 583:3151-7. [PMID: 19761766 DOI: 10.1016/j.febslet.2009.09.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/04/2009] [Accepted: 09/08/2009] [Indexed: 10/20/2022]
Abstract
The mycobacterial ubiquitin-like protein Pup is coupled to proteins, thereby rendering them as substrates for proteasome-mediated degradation. The Pup-tagged proteins are recruited by the proteasomal ATPase Mpa (also called ARC). Using a combination of biochemical and NMR methods, we characterize the structural determinants of Pup and its interaction with Mpa, demonstrating that Pup adopts a range of extended conformations with a short helical stretch in its C-terminal portion. We show that the N-terminal coiled-coil domain of Mpa makes extensive contacts along the central region of Pup leaving its N-terminus unconstrained and available for other functional interactions.
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Affiliation(s)
- Markus Sutter
- ETH Zurich, Institute of Molecular Biology and Biophysics, Zurich, Switzerland
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23
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Abstract
The proteasome is an intricate molecular machine, which serves to degrade proteins following their conjugation to ubiquitin. Substrates dock onto the proteasome at its 19-subunit regulatory particle via a diverse set of ubiquitin receptors and are then translocated into an internal chamber within the 28-subunit proteolytic core particle (CP), where they are hydrolyzed. Substrate is threaded into the CP through a narrow gated channel, and thus translocation requires unfolding of the substrate. Six distinct ATPases in the regulatory particle appear to form a ring complex and to drive unfolding as well as translocation. ATP-dependent, degradation-coupled deubiquitination of the substrate is required both for efficient substrate degradation and for preventing the degradation of the ubiquitin tag. However, the proteasome also contains deubiquitinating enzymes (DUBs) that can remove ubiquitin before substrate degradation initiates, thus allowing some substrates to dissociate from the proteasome and escape degradation. Here we examine the key elements of this molecular machine and how they cooperate in the processing of proteolytic substrates.
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Affiliation(s)
- Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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24
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Kolygo K, Ranjan N, Kress W, Striebel F, Hollenstein K, Neelsen K, Steiner M, Summer H, Weber-Ban E. Studying chaperone-proteases using a real-time approach based on FRET. J Struct Biol 2009; 168:267-77. [PMID: 19591940 DOI: 10.1016/j.jsb.2009.07.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 06/24/2009] [Accepted: 07/06/2009] [Indexed: 11/25/2022]
Abstract
Chaperone-proteases are responsible for the processive breakdown of proteins in eukaryotic, archaeal and bacterial cells. They are composed of a cylinder-shaped protease lined on the interior with proteolytic sites and of ATPase rings that bind to the apical sides of the protease to control substrate entry. We present a real-time FRET-based method for probing the reaction cycle of chaperone-proteases, which consists of substrate unfolding, translocation into the protease and degradation. Using this system we show that the two alternative bacterial ClpAP and ClpXP complexes share the same mechanism: after initial tag recognition, fast unfolding of substrate occurs coinciding with threading through the chaperone. Subsequent slow substrate translocation into the protease chamber leads to formation of a transient compact substrate intermediate presumably close to the chaperone-protease interface. Our data for ClpX and ClpA support the mechanical unfolding mode of action proposed for these chaperones. The general applicability of the designed FRET system is demonstrated here using in addition an archaeal PAN-proteasome complex as model for the more complex eukaryotic proteasome.
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Affiliation(s)
- Kristina Kolygo
- ETH Zürich, Institute of Molecular Biology & Biophysics, Switzerland
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25
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Zhang F, Hu M, Tian G, Zhang P, Finley D, Jeffrey PD, Shi Y. Structural insights into the regulatory particle of the proteasome from Methanocaldococcus jannaschii. Mol Cell 2009; 34:473-84. [PMID: 19481527 DOI: 10.1016/j.molcel.2009.04.021] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2009] [Revised: 03/08/2009] [Accepted: 04/17/2009] [Indexed: 10/20/2022]
Abstract
Eukaryotic proteasome consists of a core particle (CP), which degrades unfolded protein, and a regulatory particle (RP), which is responsible for recognition, ATP-dependent unfolding, and translocation of polyubiquitinated substrate protein. In the archaea Methanocaldococcus jannaschii, the RP is a homohexameric complex of proteasome-activating nucleotidase (PAN). Here, we report the crystal structures of essential elements of the archaeal proteasome: the CP, the ATPase domain of PAN, and a distal subcomplex that is likely the first to encounter substrate. The distal subcomplex contains a coiled-coil segment and an OB-fold domain, both of which appear to be conserved in the eukaryotic proteasome. The OB domains of PAN form a hexameric ring with a 13 A pore, which likely constitutes the outermost constriction of the substrate translocation channel. These studies reveal structural codes and architecture of the complete proteasome, identify potential substrate-binding sites, and uncover unexpected asymmetry in the RP of archaea and eukaryotes.
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Affiliation(s)
- Fan Zhang
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
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26
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Butler JS, Mitrea DM, Mitrousis G, Cingolani G, Loh SN. Structural and thermodynamic analysis of a conformationally strained circular permutant of barnase. Biochemistry 2009; 48:3497-507. [PMID: 19260676 DOI: 10.1021/bi900039e] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Circular permutation of a protein covalently links its original termini and creates new ends at another location. To maintain the stability of the permuted structure, the termini are typically bridged by a peptide long enough to span the original distance between them. Here, we take the opposite approach and employ a very short linker to introduce conformational strain into a protein by forcing its termini together. We join the N- and C-termini of the small ribonuclease barnase (normally 27.2 A distant) with a single Cys residue and introduce new termini at a surface loop, to create pBn. Compared to a similar variant permuted with an 18-residue linker, permutation with a single amino acid dramatically destabilizes barnase. Surprisingly, pBn is folded at 10 degrees C and possesses near wild-type ribonuclease activity. The 2.25 A X-ray crystal structure of pBn reveals how the barnase fold is able to adapt to permutation, partially defuse conformational strain, and preserve enzymatic function. We demonstrate that strain in pBn can be relieved by cleaving the linker with a chemical reagent. Catalytic activity of both uncleaved (strained) pBn and cleaved (relaxed) pBn is proportional to their thermodynamic stabilities, i.e., the fraction of folded molecules. The stability and activity of cleaved pBn are dependent on protein concentration. At concentrations above approximately 2 microM, cleaving pBn is predicted to increase the fraction of folded molecules and thus enhance ribonuclease activity at 37 degrees C. This study suggests that introducing conformational strain by permutation, and releasing strain by cleavage, is a potential mechanism for engineering an artificial zymogen.
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Affiliation(s)
- James S Butler
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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27
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Bacterial ubiquitin-like modifier Pup is deamidated and conjugated to substrates by distinct but homologous enzymes. Nat Struct Mol Biol 2009; 16:647-51. [PMID: 19448618 DOI: 10.1038/nsmb.1597] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Accepted: 04/02/2009] [Indexed: 11/08/2022]
Abstract
In analogy to ubiquitin in eukaryotes, the bacterial protein Pup is attached to lysine residues of substrate proteins, thereby targeting them for proteasomal degradation. It has been proposed that, before its attachment, Pup is modified by deamidation of its C-terminal glutamine to glutamate. Here we have identified Dop (locus tag Rv2112) as the specific deamidase of Pup in Mycobacterium tuberculosis. Deamidation requires ATP as a cofactor but not its hydrolysis. Furthermore, we provide experimental evidence that PafA (locus tag Rv2097) ligates deamidated Pup to the proteasomal substrate proteins FabD and PanB. This formation of an isopeptide bond requires hydrolysis of ATP to ADP, suggesting that deamidated Pup is activated for conjugation via phosphorylation of its C-terminal glutamate. By combining these enzymes, we have reconstituted the complete bacterial ubiquitin-like modification pathway in vitro, consisting of deamidation and ligation steps catalyzed by Pup deamidase (Dop) and Pup ligase (PafA).
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28
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Zhang F, Wu Z, Zhang P, Tian G, Finley D, Shi Y. Mechanism of substrate unfolding and translocation by the regulatory particle of the proteasome from Methanocaldococcus jannaschii. Mol Cell 2009; 34:485-96. [PMID: 19481528 PMCID: PMC5226943 DOI: 10.1016/j.molcel.2009.04.022] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Revised: 03/08/2009] [Accepted: 04/17/2009] [Indexed: 11/30/2022]
Abstract
In the archaebacterium Methanocaldococcus jannaschii (M. jannaschii), the proteasomal regulatory particle (RP), a homohexameric complex of proteasome-activating nucleotidase (PAN), is responsible for target protein recognition, followed by unfolding and translocation of the bound protein into the core particle (CP) for degradation. Guided by structure-based mutagenesis, we identify amino acids and structural motifs that are essential for PAN function. Key residues line the axial channel of PAN, defining the apparent pathway of substrate translocation. Subcomplex II of PAN, comprising the ATPase domain, associates with the CP and drives ATP-dependent unfolding of the substrate protein, whereas the distal subcomplex I forms the entry port of the substrate translocation channel. A linker segment between subcomplexes I and II is essential for PAN function, implying functional and perhaps mechanical coupling between these domains. Sequence conservation suggests that the principles of PAN function are likely to apply to the proteasomal RP of eukaryotes.
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Affiliation(s)
- Fan Zhang
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
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29
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Jaubert M, Hannibal L, Fardoux J, Giraud E, Verméglio A. Identification of novel genes putatively involved in the photosystem synthesis of Bradyrhizobium sp. ORS 278. PHOTOSYNTHESIS RESEARCH 2009; 100:97-105. [PMID: 19452262 DOI: 10.1007/s11120-009-9433-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 05/04/2009] [Indexed: 05/27/2023]
Abstract
In aerobic anoxygenic phototrophs, oxygen is required for both the formation of the photosynthetic apparatus and an efficient cyclic electron transfer. Mutants of Bradyrhizobium sp. ORS278 affected in photosystem synthesis were selected by a bacteriochlorophyll fluorescence-based screening. Out of the 9,600 mutants of a random Tn5 insertion library, 50 clones, corresponding to insertions in 28 different genes, present a difference in fluorescence intensity compared to the WT. Besides enzymes and regulators known to be involved in photosystem synthesis, 14 novel components of the photosynthesis control are identified. Among them, two genes, hsIU and hsIV, encode components of a protein degradation complex, probably linked to the renewal of photosystem, an important issue in Bradyrhizobia which have to deal with harmful reactive oxygen species. The presence of homologs in non-photosynthetic bacteria for most of the regulatory genes identified during study suggests that they could be global regulators, as the RegA-RegB system.
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Affiliation(s)
- Marianne Jaubert
- Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, CIRAD, AGRO-M, INRA, UM2. TA A-82/J, Campus de Baillarguet, 34398, Montpellier Cedex 5, France
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30
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Affiliation(s)
- Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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31
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Rousseau E, Kojima R, Hoffner G, Djian P, Bertolotti A. Misfolding of proteins with a polyglutamine expansion is facilitated by proteasomal chaperones. J Biol Chem 2008; 284:1917-29. [PMID: 18986984 PMCID: PMC2615503 DOI: 10.1074/jbc.m806256200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Deposition of misfolded proteins with a polyglutamine expansion is a hallmark of Huntington disease and other neurodegenerative disorders. Impairment of the proteolytic function of the proteasome has been reported to be both a cause and a consequence of polyglutamine accumulation. Here we found that the proteasomal chaperones that unfold proteins to be degraded by the proteasome but also have non-proteolytic functions co-localized with huntingtin inclusions both in primary neurons and in Huntington disease patients and formed a complex independently of the proteolytic particle. Overexpression of Rpt4 or Rpt6 facilitated aggregation of mutant huntingtin and ataxin-3 without affecting proteasomal degradation. Conversely, reducing Rpt6 or Rpt4 levels decreased the number of inclusions in primary neurons, indicating that endogenous Rpt4 and Rpt6 facilitate inclusion formation. In vitro reconstitution experiments revealed that purified 19S particles promote mutant huntingtin aggregation. When fused to the ornithine decarboxylase destabilizing sequence, proteins with expanded polyglutamine were efficiently degraded and did not aggregate. We propose that aggregation of proteins with expanded polyglutamine is not a consequence of a proteolytic failure of the 20S proteasome. Rather, aggregation is elicited by chaperone subunits of the 19S particle independently of proteolysis.
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Affiliation(s)
- Erwann Rousseau
- MRC Laboratory of Molecular Biology, Hills Rd., Cambridge CB2 0QH, United Kingdom
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32
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The N-terminal domain of MyoD is necessary and sufficient for its nuclear localization-dependent degradation by the ubiquitin system. Proc Natl Acad Sci U S A 2008; 105:15690-5. [PMID: 18836078 DOI: 10.1073/pnas.0808373105] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
A growing number of proteins, including the myogenic transcription factor MyoD, are targeted for proteasomal degradation after N-terminal ubiquitination (NTU) where the first ubiquitin moiety is conjugated to the N-terminal residue rather than to an internal lysine. NTU might be essential in targeting both lysine-containing and naturally occurring lysine-less proteins such as p16(INK4a) and p14(ARF); however, the mechanisms that underlie this process are largely unknown. Specifically, the recognition motif(s) in the target substrates and the ubiquitin ligase(s) that catalyze NTU are still obscure. Here we show that the N-terminal domain of MyoD is critical for its degradation and that its destabilizing effect depends on nuclear localization of the protein. Deletion of the first 15 aa of MyoD blocked completely its lysine-independent degradation. Importantly, transfer of the first 30 N-terminal residues of MyoD to GFP destabilized this otherwise stable protein, and, here too, targeting for degradation depended on localization of the protein to the nucleus. Deletion of the N-terminal domain of lysine-less MyoD did not abolish completely ubiquitination of the protein, suggesting that this domain may be required for targeting the protein also in a postubiquitination step. Interestingly, NTU is evolutionarily conserved: in the yeast Saccharomyces cerevisiae lysine-less (LL) MyoD is degraded in a ubiquitin-, N-terminal domain-, and nuclear localization-dependent manner. Taken together, our data suggest that a short N-terminal segment of MyoD is necessary and sufficient to render MyoD susceptible for ubiquitin- and nuclear-dependent degradation.
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33
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Xia Z, Turner GC, Hwang CS, Byrd C, Varshavsky A. Amino acids induce peptide uptake via accelerated degradation of CUP9, the transcriptional repressor of the PTR2 peptide transporter. J Biol Chem 2008; 283:28958-68. [PMID: 18708352 DOI: 10.1074/jbc.m803980200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple pathways link expression of PTR2, the transporter of di- and tripeptides in the yeast Saccharomyces cerevisiae, to the availability and quality of nitrogen sources. Previous work has shown that induction of PTR2 by extracellular amino acids requires, in particular, SSY1 and PTR3. SSY1 is structurally similar to amino acid transporters but functions as a sensor of amino acids. PTR3 acts downstream of SSY1. Expression of the PTR2 peptide transporter is induced not only by amino acids but also by dipeptides with destabilizing N-terminal residues. These dipeptides bind to UBR1, the ubiquitin ligase of the N-end rule pathway, and allosterically accelerate the UBR1-dependent degradation of CUP9, a transcriptional repressor of PTR2. UBR1 targets CUP9 through its internal degron. Here we demonstrate that the repression of PTR2 by CUP9 requires TUP1 and SSN6, the corepressor proteins that form a complex with CUP9. We also show that the induction of PTR2 by amino acids is mediated by the UBR1-dependent acceleration of CUP9 degradation that requires both SSY1 and PTR3. The acceleration of CUP9 degradation is shown to be attained without increasing the activity of the N-end rule pathway toward substrates with destabilizing N-terminal residues. We also found that GAP1, a general amino acid transporter, strongly contributes to the induction of PTR2 by Trp. Although several aspects of this complex circuit remain to be understood, our findings establish new functional links between the amino acids-sensing SPS system, the CUP9-TUP1-SSN6 repressor complex, the PTR2 peptide transporter, and the UBR1-dependent N-end rule pathway.
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Affiliation(s)
- Zanxian Xia
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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Xia Z, Webster A, Du F, Piatkov K, Ghislain M, Varshavsky A. Substrate-binding sites of UBR1, the ubiquitin ligase of the N-end rule pathway. J Biol Chem 2008; 283:24011-28. [PMID: 18566452 DOI: 10.1074/jbc.m802583200] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Substrates of a ubiquitin-dependent proteolytic system called the N-end rule pathway include proteins with destabilizing N-terminal residues. N-recognins, the pathway's ubiquitin ligases, contain three substrate-binding sites. The type-1 site is specific for basic N-terminal residues (Arg, Lys, and His). The type-2 site is specific for bulky hydrophobic N-terminal residues (Trp, Phe, Tyr, Leu, and Ile). We show here that the type-1/2 sites of UBR1, the sole N-recognin of the yeast Saccharomyces cerevisiae, are located in the first approximately 700 residues of the 1,950-residue UBR1. These sites are distinct in that they can be selectively inactivated by mutations, identified through a genetic screen. Mutations inactivating the type-1 site are in the previously delineated approximately 70-residue UBR motif characteristic of N-recognins. Fluorescence polarization and surface plasmon resonance were used to determine that UBR1 binds, with a K(d) of approximately 1 microm, to either type-1 or type-2 destabilizing N-terminal residues of reporter peptides but does not bind to a stabilizing N-terminal residue such as Gly. A third substrate-binding site of UBR1 targets an internal degron of CUP9, a transcriptional repressor of peptide import. We show that the previously demonstrated in vivo dependence of CUP9 ubiquitylation on the binding of cognate dipeptides to the type-1/2 sites of UBR1 can be reconstituted in a completely defined in vitro system. We also found that purified UBR1 and CUP9 interact nonspecifically and that specific binding (which involves, in particular, the binding by cognate dipeptides to the UBR1 type-1/2 sites) can be restored either by a chaperone such as EF1A or through macromolecular crowding.
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Affiliation(s)
- Zanxian Xia
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract
How do chaperones operate in cells? For some major chaperones it is clear what they do, though mostly not how they do it. Hsp60, 70 and 100 families carry out folding, unfolding or disaggregation of proteins. Regarding mechanisms of action, we have the clearest picture of the ATP-driven mechanism of the bacterial Hsp60s, and structures of full-length Hsp70 and 90 family members are beginning to give insights into their allosteric mechanisms. Recent advances are giving an improved understanding of the nature of chaperone interactions with their non-native substrate proteins. There have also been significant advances in understanding the engagement of chaperones in preventing the formation of toxic aggregates in degenerative disease and the relationship of protein quality control to complex biological processes such as ageing.
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