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Boshoff A. Chaperonin: Co-chaperonin Interactions. Subcell Biochem 2023; 101:213-246. [PMID: 36520309 DOI: 10.1007/978-3-031-14740-1_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Co-chaperonins function together with chaperonins to mediate ATP-dependent protein folding in a variety of cellular compartments. Chaperonins are evolutionarily conserved and form two distinct classes, namely, group I and group II chaperonins. GroEL and its co-chaperonin GroES form part of group I and are the archetypal members of this family of protein folding machines. The unique mechanism used by GroEL and GroES to drive protein folding is embedded in the complex architecture of double-ringed complexes, forming two central chambers that undergo conformational rearrangements that enable protein folding to occur. GroES forms a lid over the chamber and in doing so dislodges bound substrate into the chamber, thereby allowing non-native proteins to fold in isolation. GroES also modulates allosteric transitions of GroEL. Group II chaperonins are functionally similar to group I chaperonins but differ in structure and do not require a co-chaperonin. A significant number of bacteria and eukaryotes house multiple chaperonin and co-chaperonin proteins, many of which have acquired additional intracellular and extracellular biological functions. In some instances, co-chaperonins display contrasting functions to those of chaperonins. Human HSP60 (HSPD) continues to play a key role in the pathogenesis of many human diseases, in particular autoimmune diseases and cancer. A greater understanding of the fascinating roles of both intracellular and extracellular Hsp10 on cellular processes will accelerate the development of techniques to treat diseases associated with the chaperonin family.
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Affiliation(s)
- Aileen Boshoff
- Biotechnology Innovation Centre, Rhodes University, Makhanda/Grahamstown, South Africa.
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2
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Timperio AM, Egidi MG, Zolla L. Proteomics applied on plant abiotic stresses: role of heat shock proteins (HSP). J Proteomics 2008; 71:391-411. [PMID: 18718564 DOI: 10.1016/j.jprot.2008.07.005] [Citation(s) in RCA: 249] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 07/14/2008] [Accepted: 07/15/2008] [Indexed: 10/21/2022]
Abstract
The most crucial function of plant cell is to respond against stress induced for self-defence. This defence is brought about by alteration in the pattern of gene expression: qualitative and quantitative changes in proteins are the result, leading to modulation of certain metabolic and defensive pathways. Abiotic stresses usually cause protein dysfunction. They have an ability to alter the levels of a number of proteins which may be soluble or structural in nature. Nowadays, in higher plants high-throughput protein identification has been made possible along with improved protein extraction, purification protocols and the development of genomic sequence databases for peptide mass matches. Thus, recent proteome analysis performed in the vegetal Kingdom has provided new dimensions to assess the changes in protein types and their expression levels under abiotic stress. As reported in this review, specific and novel proteins, protein-protein interactions and post-translational modifications have been identified, which play a role in signal transduction, anti-oxidative defence, anti-freezing, heat shock, metal binding etc. However, beside specific proteins production, plants respond to various stresses in a similar manner by producing heat shock proteins (HSPs), indicating a similarity in the plant's adaptive mechanisms; in plants, more than in animals, HSPs protect cells against many stresses. A relationship between ROS and HSP also seems to exist, corroborating the hypothesis that during the course of evolution, plants were able to achieve a high degree of control over ROS toxicity and are now using ROS as signalling molecules to induce HSPs.
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Affiliation(s)
- Anna Maria Timperio
- Department of Environmental Sciences, University of Tuscia, Largo dell'Università snc, 01100 Viterbo, Italy
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3
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Bota DA, Davies KJ. Protein degradation in mitochondria: implications for oxidative stress, aging and disease: a novel etiological classification of mitochondrial proteolytic disorders. Mitochondrion 2005; 1:33-49. [PMID: 16120267 DOI: 10.1016/s1567-7249(01)00005-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2001] [Accepted: 03/16/2001] [Indexed: 01/12/2023]
Abstract
The mitochondrial genome encodes just a small number of subunits of the respiratory chain. All the other mitochondrial proteins are encoded in the nucleus and produced in the cytosol. Various enzymes participate in the activation and intramitochondrial transport of imported proteins. To finally take their place in the various mitochondrial compartments, the targeting signals of imported proteins have to be cleaved by mitochondrial processing peptidases. Mitochondria must also be able to eliminate peptides that are internally synthesized in excess, as well as those that are improperly assembled, and those with abnormal conformation caused by mutation or oxidative damage. Damaged mitochondrial proteins can be removed in two ways: either through lysosomal autophagy, that can account for at most 25-30% of the biochemically estimated rates of average mitochondrial catabolism; or through an intramitochondrial proteinolytic pathway. Mitochondrial proteases have been extensively studied in yeast, but evidence in recent years has demonstrated the existence of similar systems in mammalian cells, and has pointed to the possible importance of mitochondrial proteolytic enzymes in human diseases and ageing. A number of mitochondrial diseases have been identified whose mechanisms involve proteolytic dysfunction. Similar mechanisms probably play a role in diminished resistance to oxidative stress, and in the aging process. In this paper we review current knowledge of mammalian mitochondrial proteolysis, under normal conditions and in several disease states, and we propose an etiological classification of human diseases characterized by a decline or loss of function of mitochondrial proteolytic enzymes.
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Affiliation(s)
- D A Bota
- Ethel Percy Andrus Gerontology Center and Division of Molecular Biology, University of Southern California, Los Angeles, CA-90089-0191, USA
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4
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Maupin-Furlow JA, Kaczowka SJ, Ou MS, Wilson HL. Archaeal proteasomes: proteolytic nanocompartments of the cell. ADVANCES IN APPLIED MICROBIOLOGY 2002; 50:279-338. [PMID: 11677686 DOI: 10.1016/s0065-2164(01)50008-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- J A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700, USA
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5
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Gillette TG, Huang W, Russell SJ, Reed SH, Johnston SA, Friedberg EC. The 19S complex of the proteasome regulates nucleotide excision repair in yeast. Genes Dev 2001; 15:1528-39. [PMID: 11410533 PMCID: PMC312714 DOI: 10.1101/gad.869601] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Previous studies suggest that the amino-terminal ubiquitin-like (ubl) domain of Rad23 protein can recruit the proteasome for a stimulatory role during nucleotide excision repair in the yeast Saccharomyces cerevisiae. In this report, we show that the 19S regulatory complex of the yeast proteasome can affect nucleotide excision repair independently of Rad23 protein. Strains with mutations in 19S regulatory subunits (but not 20S subunits) of the proteasome promote partial recovery of nucleotide excision repair in vivo in rad23 deletion mutants, but not in other nucleotide excision repair-defective strains tested. In addition, a strain that expresses a temperature-degradable ATPase subunit of the 19S regulatory complex manifests a dramatically increased rate of nucleotide excision repair in vivo. These data indicate that the 19S regulatory complex of the 26S proteasome can negatively regulate the rate of nucleotide excision repair in yeast and suggest that Rad23 protein not only recruits the 19S regulatory complex, but also can mediate functional interactions between the 19S regulatory complex and the nucleotide excision repair machinery. The 19S regulatory complex of the yeast proteasome functions in nucleotide excision repair independent of proteolysis.
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Affiliation(s)
- T G Gillette
- Laboratory of Molecular Pathology, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9072, USA
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6
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Russell SJ, Johnston SA. Evidence that proteolysis of Gal4 cannot explain the transcriptional effects of proteasome ATPase mutations. J Biol Chem 2001; 276:9825-31. [PMID: 11152478 DOI: 10.1074/jbc.m010889200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Gal system of Saccharomyces cerevisiae is a paradigm for eukaryotic gene regulation. Expression of genes required for growth on galactose is regulated by the transcriptional activator Gal4. The activation function of Gal4 has been localized to 34 amino acids near the C terminus of the protein. The gal4D allele of GAL4 encodes a truncated protein in which only 14 amino acids of the activation domain remain. Expression of GAL genes is dramatically reduced in gal4D strains and these strains are unable to grow on galactose as the sole carbon source. Overexpression of gal4D partially relieves the defect in GAL gene expression and allows growth on galactose. A search for extragenic suppressors of gal4D identified recessive mutations in the SUG1 and SUG2 genes, which encode ATPases of the 19S regulatory complex of the proteasome. The proteasome is responsible for the ATP-dependent degradation of proteins marked for destruction by the ubiquitin system. It has been commonly assumed that effects of SUG1 and SUG2 mutations on transcription are explained by alterations in the proteolysis of gal4D protein. We have investigated this assumption. Surprisingly, we find that SUG1 and SUG2 alleles that are unable to suppress gal4D cause a larger increase in gal4D protein levels than do suppressing alleles. In addition, mutations in genes encoding subunits of the proteolytic 20S sub-complex of the proteasome increase the levels of gal4D protein but do not rescue its transcriptional activity. Therefore, an alteration in the proteolysis of gal4D by the proteasome cannot explain the effects of mutations in SUG1 and SUG2 on expression of GAL genes. These findings suggest that the 19S regulatory complex may play a more direct role in transcription.
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Affiliation(s)
- S J Russell
- Department of Internal Medicine, Biochemistry and Molecular Biology Graduate Program, University of Texas Southwestern Medical Center, Dallas 75390-8573, USA
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7
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Abstract
OBJECTIVE To review present knowledge of intracellular mechanisms and molecular regulation of muscle cachexia. SUMMARY BACKGROUND DATA Muscle cachexia, mainly reflecting degradation of myofibrillar proteins, is an important clinical feature in patients with severe injury, sepsis, and cancer. The catabolic response in skeletal muscle may result in muscle wasting and weakness, delaying or preventing ambulation and rehabilitation in these patients and increasing the risk for pulmonary complications. RESULTS Muscle cachexia, induced by severe injury, sepsis, and cancer, is associated with increased gene expression and activity of the calcium/calpain- and ubiquitin/proteasome-proteolytic pathways. Calcium/calpain-regulated release of myofilaments from the sarcomere is an early, and perhaps rate-limiting, component of the catabolic response in muscle. Released myofilaments are ubiquitinated in the N-end rule pathway, regulated by the ubiquitin-conjugating enzyme E2(14k) and the ubiquitin ligase E3 alpha, and degraded by the 26S proteasome. CONCLUSIONS An understanding of the mechanisms regulating muscle protein breakdown is important for the development of therapeutic strategies aimed at treating or preventing muscle cachexia in patients with severe injury, sepsis, cancer, and perhaps other catabolic conditions as well.
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Affiliation(s)
- P O Hasselgren
- Department of Surgery, University of Cincinnati, Cincinnati, Ohio 45267-0558, USA.
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8
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Protein Metabolism in Surgery. Surgery 2001. [DOI: 10.1007/978-3-642-57282-1_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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9
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Hoppert M, Mayer F. Principles of macromolecular organization and cell function in bacteria and archaea. Cell Biochem Biophys 2000; 31:247-84. [PMID: 10736750 DOI: 10.1007/bf02738242] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Structural organization of the cytoplasm by compartmentation is a well established fact for the eukaryotic cell. In prokaryotes, compartmentation is less obvious. Most prokaryotes do not need intracytoplasmic membranes to maintain their vital functions. This review, especially dealing with prokaryotes, will point out that compartmentation in prokaryotes is present, but not only achieved by membranes. Besides membranes, the nucleoid, multienzyme complexes and metabolons, storage granules, and cytoskeletal elements are involved in compartmentation. In this respect, the organization of the cytoplasm of prokaryotes is similar to that in the eukaryotic cell. Compartmentation influences properties of water in cells.
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Affiliation(s)
- M Hoppert
- Abteilung Strukfurelle Mikrobiologie, Georg-August-Universitat, Göttingen, Germany.
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10
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Russell SJ, Reed SH, Huang W, Friedberg EC, Johnston SA. The 19S regulatory complex of the proteasome functions independently of proteolysis in nucleotide excision repair. Mol Cell 1999; 3:687-95. [PMID: 10394357 DOI: 10.1016/s1097-2765(01)80001-0] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The 26S proteasome degrades proteins targeted by the ubiquitin pathway, a function thought to explain its role in cellular processes. The proteasome interacts with the ubiquitin-like N terminus of Rad23, a nucleotide excision repair (NER) protein, in Saccharomyces cerevisiae. Deletion of the ubiquitin-like domain causes UV radiation sensitivity. Here, we show that the ubiquitin-like domain of Rad23 is required for optimal activity of an in vitro NER system. Inhibition of proteasomal ATPases diminishes NER activity in vitro and increases UV sensitivity in vivo. Surprisingly, blockage of protein degradation by the proteasome has no effect on the efficiency of NER. This establishes that the regulatory complex of the proteasome has a function independent of protein degradation.
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Affiliation(s)
- S J Russell
- Department of Medicine and Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235, USA
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11
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Gardrat F, Fraigneau B, Montel V, Raymond J, Azanza JL. Effect of high hydrostatic pressures on 20S proteasome activity. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:900-6. [PMID: 10411654 DOI: 10.1046/j.1432-1327.1999.00470.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The 20S proteasome is the catalytic core of the ubiquitin proteolytic pathway, which is implicated in many cellular processes. The cylindrical structure of this complex consists of four stacked rings of seven subunits each. The central cavity is formed by two beta catalytic subunit rings in which protein substrates are progressively degraded. The 20S proteasome is isolated in a latent form which can be activated in vitro by various chemical and physical treatments. In this study, the effects of high hydrostatic pressures on 20S proteasome enzymatic activity were investigated. When proteasomes were subjected to increasing hydrostatic pressures, a progressive loss of peptidase activities was observed between 75 and 150 MPa. The inactivation also occurred when proteasomes were pressurized in the presence of synthetic peptide substrates; this may be the result of the dissociation of the 20S particle into its subunits under pressure, as was shown by PAGE. Pressurized proteasomes also lost their caseinolytic activity. In contrast, in the presence of casein, the pressure-induced inactivation and the dissociation of the 20S particles were prevented. In addition, in comparison to that observed at atmospheric pressure, their caseinolytic activity was increased under pressure. Following depressurization, the caseinolytic activity returned to basal levels but was further enhanced following an additional pressurization treatment. Thus, the structure of the 20S particle exhibits a certain degree of plasticity. This pressure-induced activation of the 20S proteasome is discussed in relation to its hollow structure, its currently accepted proteolytic mechanism and the general effect of high pressures on the biochemical reactions and structures of biopolymers.
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Affiliation(s)
- F Gardrat
- Laboratoire de Biochimie et Technologie des Aliments (ISTAB), Talence, France
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12
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Corydon TJ, Bross P, Holst HU, Neve S, Kristiansen K, Gregersen N, Bolund L. A human homologue of Escherichia coli ClpP caseinolytic protease: recombinant expression, intracellular processing and subcellular localization. Biochem J 1998; 331 ( Pt 1):309-16. [PMID: 9512494 PMCID: PMC1219353 DOI: 10.1042/bj3310309] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have recently cloned a human cDNA (hClpP) with significant sequence similarity to the ATP-dependent Escherichia coli ClpP protease [Bross, Andresen, Knudsen, Kruse and Gregersen (1995) FEBS Lett. 377, 249-252]. In the present study, synthesis, intracellular processing and subcellular localization of hClpP have been analysed in intact cells and in a cell-free system. Using pulse-labelling/immunoprecipitation of Chang cells transfected with the hClpP cDNA, we observed two major bands with apparent molecular masses of approx. 39 and 37 kDa. A pulse-chase experiment showed that these bands were converted into one mature-enzyme band with a molecular mass of approx. 32 kDa that was stable for at least 24 h. The 37 kDa band co-migrated with a band produced upon expression of full-length hClpP in E. coli, and the 32 kDa band co-migrated with the product of E. coli-expressed hClpP in which the 56 N-terminal residues had been deleted, indicating that the 37 kDa moiety represents the precursor and that approx. 56 residues are cleaved off during maturation. The processing of hClpP in intact cells was dependent on mitochondrial membrane potential. These results were confirmed in an import assay system using in vitro transcription and translation directed by the hClpP cDNA and isolated rat liver mitochondria. No protease activity towards a series of fluorogenic peptides could be observed in extracts of Chang cells overexpressing hClpP, indicating that the protease may not be active without co-factors. Immunofluorescence studies using confocal-laser-scanning microscopy showed co-localization of the hClpP and the mitochondrially located Hsp60 (heat-shock protein 60). Taken together, the results reported here show that hClpP is localized inside mitochondria and that the trafficking and processing of hClpP resembles the typical biogenesis pathway for nuclear-encoded mitochondrial proteins.
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Affiliation(s)
- T J Corydon
- Institute for Human Genetics, Wilhelm Meyers Allé, Arhus University, 8000 Arhus C, Denmark
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13
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Abstract
Cytoplasmic proteases, although necessary for proper cell functioning, must be strictly regulated. In fact, they resemble chaperones, ancient protein folding devices. These molecules recognise exposed hydrophobic regions of unfolded or denatured proteins. For most substances it is not known how the cell chooses between the refolding and proteolytic pathways. In Escherichia coli, however, a carboxy-terminal proteolysis tag and binding site for the chaperone DnaK have recently been identified.
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Affiliation(s)
- C Herman
- University of California at San Francisco, Department of Stomatology, Box 0512, 513 Parnassus Avenue, Room S-534, San Francisco, CA 94143, USA.
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14
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Abstract
The NFkappaB1 gene encodes two functionally distinct proteins termed p50 and p105. p50 corresponds to the N terminus of p105 and with p65 (RelA) forms the prototypical NF-kappaB transcription factor complex. In contrast, p105 functions as a Rel-specific inhibitor (IKB) and has been proposed to be the precursor of p50. Our studies now demonstrate that p50 is generated by a unique cotranslational processing event involving the 26S proteasome, whereas cotranslational folding of sequences near the C terminus of p50 abrogates proteasome processing and leads to p105 production. These results indicate that p105 is not the precursor of p50 and reveal a novel mechanism of gene regulation that ensures the balanced production and independent function of the p50 and p105 proteins.
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Affiliation(s)
- L Lin
- Gladstone Institute of Virology and Immunology, Department of Microbiology and Immunology, University of California, San Francisco 94141, USA
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15
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Abstract
The knowledge accumulated about the biochemistry of the synapsis in the last decades completely changes the notion of brain processing founded exclusively over an electrical mechanism, toward that supported by a complex chemical message exchange occurring both locally, at the synaptic site, as well as at other localities, depending on the solubility of the involved chemical substances in the extracellular compartment. These biochemical transactions support a rich symbolic processing of the information both encoded by the genes and provided by actual data collected from the surrounding environment, by means of either special molecular or cellular receptor systems. In this processing, molecules play the role of symbols and chemical affinity shared by them specifies the syntax for symbol manipulation in order to process and to produce chemical messages. In this context, neurons are conceived as message-exchanging agents. Chemical strings are produced and stored at defined places, and ionic currents are used to speed up message delivery. Synaptic transactions can no longer be assumed to correspond to a simple process of propagating numbers powered by a factor measuring the presynaptic capacity to influence the postsynaptic electrical activity, but they must be modeled by more powerful formal tools supporting both numerical and symbolic calculations. It is proposed here that formal language theory is the adequate mathematical tool to handle such symbolic processing. The purpose of the present review is therefore: (a) to discuss the relevant and recent literature about trophic factors, signal transduction mechanisms, neuromodulators and neurotransmitters in order (b) to point out the common features of these correlated processes; and (c) to show how they may be organized into a formal model supported by the theory of fuzzy formal languages (d) to model the brain as a distributed intelligent problem solver.
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Affiliation(s)
- A F Rocha
- RANI-Research on Artificial and Natural Intelligence, UNICAMP Brazil, Jundiaí, Brazil.
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16
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Abstract
The proteasome is the most complex eukaryotic macromolecular assembly yet seen in fine detail. The structure reveals completely unexpected mechanisms by which the proteasome neatly chops up unwanted proteins for disposal or display to the immune system.
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17
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Hasselgren PO, Fischer JE. The ubiquitin-proteasome pathway: review of a novel intracellular mechanism of muscle protein breakdown during sepsis and other catabolic conditions. Ann Surg 1997; 225:307-16. [PMID: 9060588 PMCID: PMC1190682 DOI: 10.1097/00000658-199703000-00011] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
SUMMARY BACKGROUND DATA Patients with sepsis and other catabolic conditions, such as severe trauma, cancer, and fasting, suffer significant loss of body protein, the majority of which originates from skeletal muscle. Recent evidence suggests that muscle protein breakdown during sepsis is caused by upregulated activity in the ubiquitin-proteasome pathway and is associated with increased expression of the ubiquitin gene. PURPOSE The purpose of the study was to review the role of the ubiquitin-proteasome pathway in the regulation of muscle proteolysis during sepsis and other catabolic conditions. REVIEW Proteins that are degraded by the ubiquitin-proteasome mechanism are first conjugated to ubiquitin, a 76-amino-acid, highly conserved residue. Ubiquitinated proteins are recognized by the 26S proteasome, which is a large proteolytic complex consisting of the 19S cap complex and the 20S proteasome. The 20S proteasome is a cylindrical particle composed of four stacked rings, making it look like a barrel. The rings form a "tunnel" in which the target proteins are hydrolyzed, after which ubiquitin is released to be reused in the proteolytic pathway. A unique feature of the ubiquitin-proteasome proteolytic pathway is its energy dependency. CONCLUSIONS An understanding of the molecular regulation of protein metabolism in patients with sepsis and other catabolic conditions is important because it may form the basis for improved treatment in the future.
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Affiliation(s)
- P O Hasselgren
- Department of Surgery, University of Cincinnati, Ohio 45267-0558, USA
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18
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Bureau JP, Olink-Coux M, Brouard N, Bayle-Julien S, Huesca M, Herzberg M, Scherrer K. Characterization of prosomes in human lymphocyte subpopulations and their presence as surface antigens. Exp Cell Res 1997; 231:50-60. [PMID: 9056411 DOI: 10.1006/excr.1996.3453] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Prosomes, also called "multicatalytic proteinase" (MCP) or "proteasomes," are a new type of ubiquitous RNP particle present in some archeobacteria and in all eukaryotic cells tested from yeast to human. They were discovered as subcomplexes of untranslated messenger-ribonucleoproteins (mRNP) and later found to have a MCP activity putatively involved in antigen processing. Being composed of variable sets of characteristic proteins and associating small RNAs (pRNA), families of individual "mosaic" prosome particles seem to characterize the differentiation type and physiological state of individual cells and tissues. Here, prosomes from human lymphocytes, isolated and characterized biochemically and by Western blot analysis, were found to differ in their subunit composition compared to other human prosomes. Surprisingly, prosomal antigens were discovered at the outer surface of blood cells monitored by flow cytometry with monoclonal antibodies to individual prosomal proteins. It was observed that human T and B lymphocytes have variable and characteristic prosomal antigens at their surface according to their CD classification. Interestingly, the lymphocyte subpopulations most strongly labeled by the anti-p25K and anti-p27K mAbs were the NK and B cells.
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Affiliation(s)
- J P Bureau
- Faculté de Médecine, Université Montpellier 1, Nimes, 30900, France
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19
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Abstract
L-lysine monohydrochloride (LMH) is widely available to the public as a nonprescription oral supplement. Most of the pharmaceutical-grade product is used as a suppressant of recurrent herpes simplex infections. Recent publications indicate the possibility of other therapeutic uses, e.g., in cardiovascular disease and osteoporosis. These and other potential applications are surveyed and evaluated in this review with suggestions for further study. Data on toxicity are reviewed and recommendations made regarding safety of chronic dosage levels.
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Affiliation(s)
- N W Flodin
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile 36688, USA
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20
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Rohrwild M, Pfeifer G, Santarius U, Müller SA, Huang HC, Engel A, Baumeister W, Goldberg AL. The ATP-dependent HslVU protease from Escherichia coli is a four-ring structure resembling the proteasome. NATURE STRUCTURAL BIOLOGY 1997; 4:133-9. [PMID: 9033594 DOI: 10.1038/nsb0297-133] [Citation(s) in RCA: 153] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
HslVU is a new two-component protease in Escherichia coli composed of the proteasome-related peptidase HslIV and the ATPase HsIU. We have used electron microscopy and image analysis to examine the structural organization of HslV and HslU homo-oligomers and the active HslVU enzyme. Electron micrographs of HslV reveal ring-shaped particles, and averaging of top views reveal six-fold rotational symmetry, in contrast to other beta-type proteasome subunits, which form rings with seven-fold symmetry. Side views of HslV show two rings stacked together, thus, HslV behaves as dodecamer. The ATPase HslU forms ring-shaped particles in the presence of ATP, AMP-PNP or ADP, suggesting that nucleotide binding, but not hydrolysis, is required for oligomerization. Subunit crosslinking, STEM mass estimation, and analysis of HslU top views indicate that HslU exists both as hexameric and heptameric rings. With AMP-PNP present, maximal proteolytic activity is observed with a molar ratio of HslU to HslV subunits of 1:1, and negative staining electron microscopy shows that HslV and HsIU form cylindrical four-ring structures in which the HsIV dodecamer is flanked at each end by a HslU ring.
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Affiliation(s)
- M Rohrwild
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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21
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Tiao G, Hobler S, Wang JJ, Meyer TA, Luchette FA, Fischer JE, Hasselgren PO. Sepsis is associated with increased mRNAs of the ubiquitin-proteasome proteolytic pathway in human skeletal muscle. J Clin Invest 1997; 99:163-8. [PMID: 9005983 PMCID: PMC507782 DOI: 10.1172/jci119143] [Citation(s) in RCA: 184] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Previous studies provided evidence that sepsis-induced muscle proteolysis in experimental animals is caused by increased ubiquitin-proteasome-dependent protein breakdown. It is not known if a similar mechanism accounts for muscle proteolysis in patients with sepsis. We determined mRNA levels for ubiquitin and the 20 S proteasome subunit HC3 by Northern blot analysis in muscle tissue from septic (n = 7) and non-septic (n = 11) patients. Plasma and muscle amino acid concentrations and concentrations in urine of 3-methylhistidine (3-MH), creatinine, and cortisol were measured at the time of surgery to assess the catabolic state of the patients. A three- to fourfold increase in mRNA levels for ubiquitin and HC3 was noted in muscle tissue from the septic patients concomitant with increased muscle levels of phenylalanine and 3-MH and reduced levels of glutamine. Total plasma amino acids were decreased by approximately 30% in the septic patients. The 3-MH/creatinine ratio in urine was almost doubled in septic patients. The cortisol levels in urine were higher in septic than in control patients but this difference did not reach statistical significance. The results suggest that sepsis is associated with increased mRNAs of the ubiquitin-proteasome pathway in human skeletal muscle.
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Affiliation(s)
- G Tiao
- Department of Surgery, University of Cincinnati and Shriners Burns Institute, Ohio 45267, USA
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22
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Abstract
Proteolysis is essential for many aspects of plant physiology and development. It is responsible for cellular housekeeping and the stress response by removing abnormal/misfolded proteins, for supplying amino acids needed to make new proteins, for assisting in the maturation of zymogens and peptide hormones by limited cleavages, for controlling metabolism, homeosis, and development by reducing the abundance of key enzymes and regulatory proteins, and for the programmed cell death of specific plant organs or cells. It also has potential biotechnological ramifications in attempts to improve crop plants by modifying protein levels. Accumulating evidence indicates that protein degradation in plants is a complex process involving a multitude of proteolytic pathways with each cellular compartment likely to have one or more. Many of these have homologous pathways in bacteria and animals. Examples include the chloroplast ClpAP protease, vacuolar cathepsins, the KEX2-like proteases of the secretory system, and the ubiquitin/26S proteasome system in the nucleus and cytoplasm. The ubiquitin-dependent pathway requires that proteins targeted for degradation become conjugated with chains of multiple ubiquitins; these chains then serve as recognition signals for selective degradation by the 26S proteasome, a 1.5 MDa multisubunit protease complex. The ubiquitin pathway is particularly important for developmental regulation by selectively removing various cell-cycle effectors, transcription factors, and cell receptors such as phytochrome A. From insights into this and other proteolytic pathways, the use of phosphorylation/dephosphorylation and/or the addition of amino acid tags to selectively mark proteins for degradation have become recurring themes.
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Affiliation(s)
- R D Vierstra
- Department of Horticulture, University of Wisconsin-Madison 53706, USA
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23
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Fischer JE. 1996 Jonathan E. Rhoads Lecture. Mechanism, mechanism, mechanism. JPEN J Parenter Enteral Nutr 1996; 20:319-24. [PMID: 8887899 DOI: 10.1177/0148607196020005319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- J E Fischer
- Department of Surgery, University of Cincinnati Medical Center, OH 45267-0558, USA
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24
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Yang Y, Sempé P, Peterson PA. Molecular mechanisms of class I major histocompatibility complex antigen processing and presentation. Immunol Res 1996; 15:208-33. [PMID: 8902577 DOI: 10.1007/bf02918250] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The presentation of antigenic peptides by class I major histocompatibility complex molecules plays a central role in the cellular immune response, since immune surveillance for detection of viral infections or malignant transformations is achieved by CD8+ T lymphocytes which inspect peptides, derived from intracellular proteins, bind to class I molecules on the surface of most cells. The transporter associated with antigen processing selectively translocates cytoplasmically derived peptides of appropriate sequence and length into the lumen of the endoplasmic reticulum where they associate with newly synthesized class I molecules. The translocated peptides are generated by multicatalytic and multisubunit proteasomes which degrade cytoplasmic proteins in a ATP-ubiquitin-dependent manner. This review discusses our current molecular understanding of class I antigen processing and presentation.
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Affiliation(s)
- Y Yang
- R.W. Johnson Pharmaceutical Research Institute, Scripps Research Institute, La Jolla, Calif 92037, USA
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25
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Huang J, Kwong J, Sun EC, Liang TJ. Proteasome complex as a potential cellular target of hepatitis B virus X protein. J Virol 1996; 70:5582-91. [PMID: 8764072 PMCID: PMC190518 DOI: 10.1128/jvi.70.8.5582-5591.1996] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Although the biological importance of hepatitis B virus X protein (HBX) in the life cycle of hepatitis B virus has been well established, the cellular and molecular basis of its function remains largely undefined. Despite the association of multiple activities with HBX, none of them appear to provide a unifying hypothesis regarding the true biological function of HBX. Identification and characterization of cellular targets of HBX remain an essential goal in the elucidation of the molecular mechanisms of HBX. Using the Saccharomyces cerevisiae two-hybrid system, we have identified and characterized a novel subunit of the proteasome complex (XAPC7) that interacts specifically with HBX. We also showed that HBX binds specifically to XAPC7 in vitro. Mutagenesis studies have defined the domains of interaction to be critical for the function of HBX. Furthermore, overexpression of XAPC7 appeared to activate transcription by itself and antisense expression of XAPC7 was able to block transactivation by HBX. Therefore, the proteasome complex is possibly a functional target of HBX in cells.
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Affiliation(s)
- J Huang
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, 02114, USA
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26
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Abstract
Most approaches to information pay attention only to the 'positive' or constructive side ('presence') of this phenomenon: its composition, construction rules, emergence, effective activity, etc. However, the 'negative' or degrading aspects ('absences', disappearance of activity) are equally important within most biologico-informational processes. In fact, protein degradation can be put on a par with protein synthesis concerning its functionality and sophistication. By taking into account recent integrative discoveries in the molecular biology of the cell (signalling system, cell cycle, apoptosis, protein degradation, enzyme function) a wider approach encompassing both the 'presence' and 'absence' aspects seems possible. The overall dynamics which emerges--involving symmetry breaking and symmetry restoration by means of information processing mechanisms--may be extrapolated to neuronal and socio-economic realms too. Interestingly, the phenomenon of 'absence' can also be pinpointed, at least as a metaphor, within the internal structure of natural numbers.
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Affiliation(s)
- P C Marijuán
- Departamento Ingenieria Eléctrica y Electrónica, C.P.S. Universidad de Zaragoza, Spain
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27
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Abstract
Nascent polypeptide chains are in a dangerous situation as soon as they leave their place of birth, the channel of the large ribosomal subunit: more than 20 different pathways for the degradation of proteins exist in cells. Chaperones protect and guide the young protein molecules and support their correct foldings. Targeting signals direct the proteins to the organelles of their destination. The lysosome is the site of random degradation, while the proteasome is highly selective. Although these two organelles provide the most important pathways for the degradation of long- and short-lived proteins, other pathways with roles in deciding the fate of cellular proteins must also be considered.
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Affiliation(s)
- P Bohley
- Physiologisch-Chemisches Institut der Universität, Tübingen
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28
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Sighting the cellular shredder. NATURE STRUCTURAL BIOLOGY 1995; 2:427-8. [PMID: 7664100 DOI: 10.1038/nsb0695-427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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