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Haarer B, Aggeli D, Viggiano S, Burke DJ, Amberg DC. Novel interactions between actin and the proteasome revealed by complex haploinsufficiency. PLoS Genet 2011; 7:e1002288. [PMID: 21966278 PMCID: PMC3178594 DOI: 10.1371/journal.pgen.1002288] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 07/29/2011] [Indexed: 11/18/2022] Open
Abstract
Saccharomyces cerevisiae has been a powerful model for uncovering the landscape of binary gene interactions through whole-genome screening. Complex heterozygous interactions are potentially important to human genetic disease as loss-of-function alleles are common in human genomes. We have been using complex haploinsufficiency (CHI) screening with the actin gene to identify genes related to actin function and as a model to determine the prevalence of CHI interactions in eukaryotic genomes. Previous CHI screening between actin and null alleles for non-essential genes uncovered ∼240 deleterious CHI interactions. In this report, we have extended CHI screening to null alleles for essential genes by mating a query strain to sporulations of heterozygous knock-out strains. Using an act1Δ query, knock-outs of 60 essential genes were found to be CHI with actin. Enriched in this collection were functional categories found in the previous screen against non-essential genes, including genes involved in cytoskeleton function and chaperone complexes that fold actin and tubulin. Novel to this screen was the identification of genes for components of the TFIID transcription complex and for the proteasome. We investigated a potential role for the proteasome in regulating the actin cytoskeleton and found that the proteasome physically associates with actin filaments in vitro and that some conditional mutations in proteasome genes have gross defects in actin organization. Whole-genome screening with actin as a query has confirmed that CHI interactions are important phenotypic drivers. Furthermore, CHI screening is another genetic tool to uncover novel functional connections. Here we report a previously unappreciated role for the proteasome in affecting actin organization and function.
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Affiliation(s)
- Brian Haarer
- Department of Biochemistry and Molecular Biology, Upstate Medical University, State University of New York, Syracuse, New York, United States of America
| | - Dimitra Aggeli
- Department of Biochemistry and Molecular Biology, Upstate Medical University, State University of New York, Syracuse, New York, United States of America
| | - Susan Viggiano
- Department of Biochemistry and Molecular Biology, Upstate Medical University, State University of New York, Syracuse, New York, United States of America
| | - Daniel J. Burke
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Charlottesville, Virginia, United States of America
| | - David C. Amberg
- Department of Biochemistry and Molecular Biology, Upstate Medical University, State University of New York, Syracuse, New York, United States of America
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2
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Kawakami K, Kuroda M, Nishikawa A. Regulation of desmin expression in adult-type myogenesis and muscle maturation during Xenopus laevis metamorphosis. Zoolog Sci 2009; 26:389-97. [PMID: 19583497 DOI: 10.2108/zsj.26.389] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Isoforms of myosin heavy chain and tropomyosin convert during metamorphosis of Xenopus laevis with larval-to-adult remodeling of dorsal muscle (Nishikawa and Hayashi, 1994 , Dev. Biol. 165: 86-94). In the present study, other markers for muscle remodeling during metamorphosis were determined by SDS-PAGE analysis. The amounts of twelve muscle proteins changed remarkably during metamorphosis. Among these, a 54-kDa molecule was found to be desmin, and the relative content/total proteins decreased dramatically through metamorphosis. In hindlimb muscle, desmin content increased fourfold during prometamorphosis, when myoblast proliferation and fusion occurred. With further myotube maturation, this content decreased by 1/2 while that of muscle actin continued to increase. Thus, desmin up- and down-regulation in hindlimbs mark early and late phases of myogenesis, respectively. In tall muscle, the desmin content decreased continuously to (1/8) before and during metamorphosis, due to tall muscle growth and maturation. In dorsal muscle, three desmin changes occurred: a pre-metamorphic decrease, a transient increase at prometamorphosis, and a rapid decrease at the climax stage. Immunohistochemical analysis showed desmin+ cells to be present between young (adult-type) myotubes and replicating (PCNA+) cells in dorsal muscles, correlating the transient desmin upregulation in dorsal muscle with the initiation of adult-type myogenesis. After the upregulation, dorsal muscle desmin decreased to (1/8). This rapid down-regulation was replicated by administration of triiodothyronine (T3) to tadpoles, suggesting a significant role for T3 in dorsal muscle remodeling during metamorphosis. Collectively, these results show that analysis of desmin expression and PCNA-immunohistochemistry are good tools for determining the sites and timing of larval-to-adult muscle remodeling during Xenopus laevis metamorphosis.
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Affiliation(s)
- Kiyoshi Kawakami
- Department of Biological Science, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane 690-8504, Japan
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3
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Feist E, Brychcy M, Hausdorf G, Hoyer B, Egerer K, Dörner T, Kuckelkorn U, Burmester GR. Anti-proteasome autoantibodies contribute to anti-nuclear antibody patterns on human larynx carcinoma cells. Ann Rheum Dis 2006; 66:5-11. [PMID: 16815863 PMCID: PMC1798404 DOI: 10.1136/ard.2006.055152] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Autoantibodies to the 20S proteasome represent an unspecific but common serological phenomenon in patients with systemic autoimmune diseases. Interestingly, a high prevalence of these antibodies have been observed in patients with connective tissue diseases, where anti-nuclear antibodies (ANAs) serve as an important diagnostic screening test. OBJECTIVE To disclose interference of anti-proteasome antibodies with known ANA patterns. METHODS Anti-proteasome antibodies were isolated for comprehensive immunofluorescence analyses. The immunofluorescence pattern of human anti-proteasome antibodies was compared with a panel of monoclonal and polyclonal reference antibodies, and colocalisation was analysed using confocal microscopy. RESULTS Anti-proteasome antibodies clearly contributed to the ANA patterns of their respective serum samples from patients with different rheumatic disorders. In addition to the nuclear pattern, proteasomal staining was also detectable in the cytoplasm, at the endoplasmic reticulum and perinuclear regions showing features overlapping with other known autoantibodies such as those to mitochondria. The specificity of anti-proteasome antibodies was proved by competition experiments and by colocalisation with monoclonal reference antibodies in confocal microscopy. CONCLUSION In ANA diagnostics, interference of anti-proteasome antibodies will have to be taken into account, especially in the differentiation of anti-cytoplasmatic autoantibodies.
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Affiliation(s)
- E Feist
- Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin D-10117, Germany.
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4
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Ioudinkova E, Razin SV, Borunova V, De Conto F, Rynditch A, Scherrer K. RNA-dependent nuclear matrix contains a 33 kb globin full domain transcript as well as prosomes but no 26S proteasomes. J Cell Biochem 2005; 94:529-39. [PMID: 15543557 DOI: 10.1002/jcb.20306] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Previously, we have shown that in murine myoblasts prosomes are constituents of the nuclear matrix; a major part of the latter was found to be RNase sensitive. Here, we further define the RNA-dependent matrix in avian erythroblastosis virus (AEV) transformed erythroid cells in relation to its structure, presence of specific RNA, prosomes and/or proteasomes. These cells transcribe but do not express globin genes prior to induction. Electron micrographs show little difference in matrices treated with DNase alone or with both, DNase and RNase. In situ hybridization with alpha globin riboprobes shows that this matrix includes globin transcripts. Of particular interest is that, apparently, a nearly 35 kb long globin full domain transcript (FDT), including genes, intergenic regions and a large upstream domain is a part of the RNA-dependent nuclear matrix. The 23K-type of prosomes, previously shown to be co-localized with globin transcripts in the nuclear RNA processing centers, were found all over the nuclear matrix. Other types of prosomes show different distributions in the intact cell but similar distribution patterns on the matrix. Globin transcripts and at least 80% of prosomes disappear from matrices upon RNase treatment. Interestingly, the 19S proteasome modulator complex is insensitive to RNase treatment. Only 20S prosomes but not 26S proteasomes are thus part of the RNA-dependent nuclear matrix. We suggest that giant pre-mRNA and FDTs in processing, aligning prosomes and other RNA-binding proteins are involved in the organization of the dynamic nuclear matrix. It is proposed that the putative function of RNA within the nuclear matrix and, thus, the nuclear dynamic architecture, might explain the giant size and complex organization of primary transcripts and their introns.
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5
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Bassaglia Y, Cebrian J, Covan S, Garcia M, Foucrier J. Proteasomes are tightly associated to myofibrils in mature skeletal muscle. Exp Cell Res 2005; 302:221-32. [PMID: 15561103 DOI: 10.1016/j.yexcr.2004.08.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 08/07/2004] [Indexed: 10/26/2022]
Abstract
Proteasomes are the major actors of nonlysosomal cytoplasmic protein degradation. In particular, these large protein complexes (about 2500 kDa) are considered to be responsible for muscular degradation during skeletal muscle atrophy. Despite their unusual and important size, they are widely described as soluble and mobile in the cytoplasm. In mature skeletal muscle, we have previously observed a sarcomeric distribution of proteasomes, as revealed by the distribution of alpha1/p27K, a subunit of the 20S core-particle (prosome) of proteasome. Here, we extend these observations at the electron microscopic level in vivo. We also show that this sarcomeric pattern is dependent of the extension of the sarcomere. Using isolated myofibrils, we demonstrate that proteasomes are still attached to the myofibrils after the isolation procedure, and reproduce the observations made in vivo. In addition, the extraction of actin by gelsolin largely removes proteasomes from isolated myofibrils, but some of them are held in place after this extraction, showing a sarcomeric disposition in the absence of any detectable actin, and suggesting the existence of another molecular partner for these interactions. From these results, we conclude that most of detectable 20S proteasomes in skeletal muscle cells is tightly attached to the myofibrils.
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Affiliation(s)
- Yann Bassaglia
- Laboratoire CRRET, CNRS FRE 2412, Faculté des Sciences, Université Paris 12-Val de Marne, Créteil, France.
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6
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Riera L, Obach M, Navarro-Sabaté A, Duran J, Perales JC, Viñals F, Rosa JL, Ventura F, Bartrons R. Regulation of ubiquitous 6-phosphofructo-2-kinase by the ubiquitin-proteasome proteolytic pathway during myogenic C2C12 cell differentiation. FEBS Lett 2003; 550:23-9. [PMID: 12935880 DOI: 10.1016/s0014-5793(03)00808-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
6-Phosphofructo-2-kinase catalyzes the synthesis and degradation of fructose 2,6-bisphosphate, activator of phosphofructokinase-1 and inhibitor of fructose 1,6-bisphosphatase. These properties confer to this bifunctional enzyme a key role in the control of glycolysis and gluconeogenesis. Several mammalian isozymes generated by alternative splicing from four genes, designated pfkfb1-4, have been identified. The results presented in this study demonstrate the expression of the pfkfb3 gene in C2C12 cells and its downregulation during myogenic cell differentiation. We also show that the decrease of ubiquitous 6-phosphofructo-2-kinase isozyme levels, product of pfkfb3 gene, is due to its enhanced degradation through the ubiquitin-proteasome proteolytic pathway.
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Affiliation(s)
- Lluís Riera
- Unitat de Bioquímica i Biologia Molecular, Departament de Ciències Fisiològiques II, Campus de Bellvitge, Universitat de Barcelona, Feixa Llarga s/n, Pavelló de Govern, 4a planta E-08907 L'Hospitalet, Spain
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7
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Abstract
Proteasomes are present in the cytoplasm and in the nuclei of all eukaryotic cells, however their relative abundance within those compartments is highly variable. In the cytoplasm, proteasomes associate with the centrosomes, cytoskeletal networks and the outer surface of the endoplasmic reticulum (ER). In the nucleus, proteasomes are present throughout the nucleoplasm but are void from the nucleoli. Sometimes they associate with discrete subnuclear domains called the PML nuclear bodies (POD domains). PML bodies in the nucleus, and the pericentrosomal area of the cytoplasm may function as proteolytic centers of the cell, since they are enriched in components of the proteasome system. Under conditions of impaired proteolysis proteasomes and ubiquitinated proteins further accumulate at these locations, forming organized aggregates. In case of the pericentrosomal area those aggregates have been termed "aggresomes". Once formed, aggresomes can impair the function of the proteasome system, which may promote apoptosis. Under favorable conditions they can be cleared, probably by autophagy.
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8
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Foucrier J, Bassaglia Y, Grand MC, Rothen B, Perriard JC, Scherrer K. Prosomes form sarcomere-like banding patterns in skeletal, cardiac, and smooth muscle cells. Exp Cell Res 2001; 266:193-200. [PMID: 11339838 DOI: 10.1006/excr.2001.5212] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prosomes (20S proteasomes) constitute the catalytic core of the 26S proteasomes, but were first observed as factors associated with unstranslated mRNA. Recently, their RNase activity was discovered together with the fact that their proteolytic function is dispensable in adapted human cells. By indirect immunofluorescence using monoclonal antibodies, we demonstrate as a general phenomenon, regular intercalation of specific types of prosomes into the sarcomeric structure of all types of striated muscle. Surprisingly, in cultured smooth muscle cells without sarcomeric organization, some prosomes also form regular striations in extended projections of cytoplasmic regions. The significance of their sarcomeric distribution is not understood as yet, but the pattern we observe is very similar to that shown by others for muscle-specific mRNAs, identified by in situ hybridization, and that of the cognate proteins. A role of prosomes in the cotranslational assembly of the myofibrillar proteins is suggested, since prosomes organize into pseudo-sarcomeric patterns prior to formation de novo of the actin-myosin arrangement.
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MESH Headings
- Animals
- Body Patterning/physiology
- Cell Differentiation/physiology
- Cells, Cultured/cytology
- Cells, Cultured/metabolism
- Cysteine Endopeptidases/metabolism
- Cysteine Endopeptidases/ultrastructure
- Cytoskeleton/metabolism
- Cytoskeleton/ultrastructure
- Gene Expression Regulation, Developmental/physiology
- Heart/embryology
- Male
- Multienzyme Complexes/metabolism
- Multienzyme Complexes/ultrastructure
- Muscle Proteins/metabolism
- Muscle Proteins/ultrastructure
- Muscle, Skeletal/cytology
- Muscle, Skeletal/embryology
- Muscle, Skeletal/metabolism
- Muscle, Smooth/cytology
- Muscle, Smooth/embryology
- Muscle, Smooth/metabolism
- Myocardium/cytology
- Myocardium/metabolism
- Proteasome Endopeptidase Complex
- Rats
- Rats, Wistar
- Sarcomeres/metabolism
- Sarcomeres/ultrastructure
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Affiliation(s)
- J Foucrier
- CRRET-UPRESA 7053, Université Paris 12, Av. Général de Gaulle, F-94010 Créteil Cedex, France
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9
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De Conto F, Pilotti E, Razin SV, Ferraglia F, Géraud G, Arcangeletti C, Scherrer K. In mouse myoblasts nuclear prosomes are associated with the nuclear matrix and accumulate preferentially in the perinucleolar areas. J Cell Sci 2000; 113 ( Pt 13):2399-407. [PMID: 10852819 DOI: 10.1242/jcs.113.13.2399] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prosomes are the core of 26S proteasomes, although they were originally observed as 20S particles associated with cytoplasmic mRNPs. Here we show for the first time that prosomes are also genuine constituents of the nuclear matrix, chromatin and the nuclear RNP networks. Using mouse myoblasts we tested three monoclonal antibodies recognising the prosomal subunits p23K, p27K and p30K, and found that the corresponding prosome subclasses are characterised by a variable distribution pattern within the nuclei. Their presence on the nuclear matrix, and most abundantly in the perinucleolar area, is of particular importance. When myoblasts fuse into myotubes, the distribution pattern of certain types of prosomes on the nuclear matrix changes drastically. Surprisingly, DNA strongly interferes with the detection of prosomal antigens by immunofluorescence methods, whereas RNA, histones and other proteins soluble in 2 M NaCl have no such effect. This ‘masking’ of prosomes can be completely overcome by extensive or even mild digestion with DNase I or restriction enzymes. Many nuclear prosomes can be solubilized by combined treatment with 0.5% Triton X-100 and 2 M NaCl, and others can be released by digestion of DNA and/or RNA, and about 10–20% of nuclear prosomes remain tightly bound to the protein-based nuclear matrix.
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Affiliation(s)
- F De Conto
- Institut Jacques Monod - Université Paris 7, Tour 43, France
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10
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Arcangeletti C, De Conto F, Sütterlin R, Pinardi F, Missorini S, Géraud G, Aebi U, Chezzi C, Scherrer K. Specific types of prosomes distribute differentially between intermediate and actin filaments in epithelial, fibroblastic and muscle cells. Eur J Cell Biol 2000; 79:423-37. [PMID: 10928458 DOI: 10.1078/0171-9335-00059] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
First observed as components of non-translated mRNP complexes, prosomes harbour RNase and several proteinase activities; they are also the central constituent of the "Multicatalytic Proteinase (MCP) complexes" or "26S-proteasomes". In two recent publications (Arcangeletti et al., 1997b; De Conto et al., 1997) we have shown, by applying a new fixation technique, that these particles distribute differentially between the cytoskeletal networks of intermediate filament (IF) and actin types; previously they had been observed exclusively on the intermediate filaments. Here we further investigate the distribution of prosomes of several types, distinct by their subunit composition, between the IF of vimentin type and the actin network, as well as in the 3D space of the cell. It is shown that subtypes of prosomes occupy specific networks of the cytoskeleton, and that this pattern is specific for a given cell type. Confocal microscopy shows that prosome cytodistribution is not homogeneous in the 3D space: in the perinuclear area they colocalize most strongly with the IF, and more peripherally with the microfilament/stress fiber system; connections may exist between the two networks. Furthermore, new data indicate that the prosome-actin interaction may participate in the molecular structure of the stress fibers.
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11
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De Conto F, Razin SV, Geraud G, Arcangeletti C, Scherrer K. In the nucleus and cytoplasm of chicken erythroleukemic cells, prosomes containing the p23K subunit are found in centers of globin (pre-)mRNA processing and accumulation. Exp Cell Res 1999; 250:569-75. [PMID: 10413609 DOI: 10.1006/excr.1999.4556] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prosomes were originally identified as 20S particles associated with untranslated mRNA; they also constitute the core of the 26S proteasomes. The cellular distribution of three types of prosomes characterized by the presence of subunits with molecular masses of 23, 27, and 30 kDa was analyzed using an immunocytochemical approach on cultured chicken erythroblasts. The prosomes containing the p27K and p30K subunits were found in diffuse distribution in both nuclei and cytoplasm. In contrast, the prosomes containing the p23K subunit, although relatively rare in the nuclear space, were found concentrated in one or two large spots. Using in situ hybridization with an alpha(A)-globin gene-specific riboprobe we found that the p23K-type prosomes colocalize in the nucleus with centers of globin (pre-)mRNA processing, and of mRNA accumulation in the cytoplasm. This result suggests there is local coincidence of specific-type prosome function with processing and, possibly, transport of a particular kind of (pre-)mRNA.
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Affiliation(s)
- F De Conto
- Institut Jacques Monod, Université Paris 7, 2, Place Jussieu, Tour 43, Paris Cedex 05, 75251, France
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12
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Foucrier J, Grand MC, De Conto F, Bassaglia Y, Géraud G, Scherrer K, Martelly I. Dynamic distribution and formation of a para-sarcomeric banding pattern of prosomes during myogenic differentiation of satellite cells in vitro. J Cell Sci 1999; 112 ( Pt 7):989-1001. [PMID: 10198281 DOI: 10.1242/jcs.112.7.989] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myogenesis proceeds by fusion of proliferating myoblasts into myotubes under the control of various transcription factors. In adult skeletal muscle, myogenic stem cells are represented by the satellite cells which can be cultured and differentiate in vitro. This system was used to investigate the subcellular distribution of a particular type of prosomes at different steps of the myogenic process. Prosomes constitute the MCP core of the 26S proteasomes but were first observed as subcomplexes of the untranslated mRNPs; recently, their RNase activity was discovered. A monoclonal antibody raised against the p27K subunit showed that the p27K subunit-specific prosomes move transiently into the nucleus prior to the onset of myoblast fusion into myotubes; this represents possibly one of the first signs of myoblast switching into the differentiation pathway. Prior to fusion, the prosomes containing the p27K subunit return to the cytoplasm, where they align with the gradually formed lengthwise-running desmin-type intermediate filaments and the microfilaments, co-localizing finally with the actin bundles. The prosomes progressively form discontinuous punctate structures which eventually develop a pseudo-sarcomeric banding pattern. In myotubes just formed in vitro, the formation of this pattern seems to preceed that produced by the muscle-specific sarcomeric (alpha)-actin. Interestingly, this pattern of prosomes of myotubes in terminal in vitro differentiation was very similar to that of prosomes observed in vivo in foetal and adult muscle. These observations are discussed in relation to molecular myogenesis and prosome/proteasome function.
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Affiliation(s)
- J Foucrier
- CRRET, UPRESA-CNRS 7053, Université Paris 12, Av. du Général de Gaulle, France
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13
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Mykles DL. Intracellular proteinases of invertebrates: calcium-dependent and proteasome/ubiquitin-dependent systems. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 184:157-289. [PMID: 9697313 DOI: 10.1016/s0074-7696(08)62181-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cytosolic proteinases carry out a variety of regulatory functions by controlling protein levels and/or activities within cells. Calcium-dependent and ubiquitin/proteasome-dependent pathways are common to all eukaryotes. The former pathway consists of a diverse group of Ca(2+)-dependent cysteine proteinases (CDPs; calpains in vertebrate tissues). The latter pathway is highly conserved and consists of ubiquitin, ubiquitin-conjugating enzymes, deubiquitinases, and the proteasome. This review summarizes the biochemical properties and genetics of invertebrate CDPs and proteasomes and their roles in programmed cell death, stress responses (heat shock and anoxia), skeletal muscle atrophy, gametogenesis and fertilization, development and pattern formation, cell-cell recognition, signal transduction and learning, and photoreceptor light adaptation. These pathways carry out bulk protein degradation in the programmed death of the intersegmental and flight muscles of insects and of individuals in a colonial ascidian; molt-induced atrophy of crustacean claw muscle; and responses of brine shrimp, mussels, and insects to environmental stress. Selective proteolysis occurs in response to specific signals, such as in modulating protein kinase A activity in sea hare and fruit fly associated with learning; gametogenesis, differentiation, and development in sponge, echinoderms, nematode, ascidian, and insects; and in light adaptation of photoreceptors in the eyes of squid, insects, and crustaceans. Proteolytic activities and specificities are regulated through proteinase gene expression (CDP isozymes and proteasomal subunits), allosteric regulators, and posttranslational modifications, as well as through specific targeting of protein substrates by a diverse assemblage of ubiquitin-conjugases and deubiquitinases. Thus, the regulation of intracellular proteolysis approaches the complexity and versatility of transcriptional and translational mechanisms.
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Affiliation(s)
- D L Mykles
- Department of Biology, Colorado State University, Fort Collins 80523, USA
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14
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Abstract
Proteasomes are large multicatalytic proteinase complexes which are responsible for the selective degradation of cellular proteins and the production of peptides for antigen presentation. Proteasomes are localized both in the nucleus and in the cytoplasm, where some are associated with the endoplasmic reticulum membrane. Recent studies have shown differences in the localization of proteasome subpopulations, demonstrated the functional importance of endoplasmic reticulum-associated proteasomes and investigated the role of putative nuclear localization signals and tyrosine phosphorylation on proteasome transport into the nucleus.
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Affiliation(s)
- A J Rivett
- Department of Biochemistry, School of Medical Sciences, University of Bristol, UK.
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15
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Arcangeletti MC, Pinardi F, Missorini S, De Conto F, Conti G, Portincasa P, Scherrer K, Chezzi C. Modification of cytoskeleton and prosome networks in relation to protein synthesis in influenza A virus-infected LLC-MK2 cells. Virus Res 1997; 51:19-34. [PMID: 9381792 DOI: 10.1016/s0168-1702(97)00074-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Modifications of the cytoskeleton and protein synthesis were investigated in LLC-MK2 cells during infection by FPV/Ulster 73, an avian strain of influenza A virus. During infection, the cytoskeleton and the prosome networks undergo a dramatic reorganization, which seems to be at least temporally differentiated for each cytoskeletal system, i.e. microfilaments (MFs), microtubules (MTs), intermediate filaments (IFs). In order to evaluate the role of the three different cytoskeletal networks during FPV/Ulster infection, studies were carried out on cellular and virus-specific protein synthesis and viral production, using drugs which selectively affect individual cytoskeletal systems. Our data show that the perturbation of the IF system, but not that of the MFs or MTs, seems to have a strong inhibitory effect on virus production and cellular and viral protein synthesis. Furthermore, the dynamics of IFs and prosomes were investigated during viral infection and, at no time, dissociation of the prosome and IF networks was observed. Taken together, these results strongly support the idea that the interactions between the protein synthesis machinery, the cytoskeleton, and the prosomes are all affected by viral infection in a partially coordinated manner.
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Affiliation(s)
- M C Arcangeletti
- Istituto di Microbiologia, Università degli Studi di Parma, Italy
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16
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Arcangeletti C, Sütterlin R, Aebi U, De Conto F, Missorini S, Chezzi C, Scherrer K. Visualization of prosomes (MCP-proteasomes), intermediate filament and actin networks by "instantaneous fixation" preserving the cytoskeleton. J Struct Biol 1997; 119:35-58. [PMID: 9216087 DOI: 10.1006/jsbi.1997.3871] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A new "instantaneous" fixation/extraction procedure, yielding good preservation of intermediate filaments (IFs) and actin filaments when applied at 37 degrees C, has been explored to reexamine the relationships of the prosomes to the cytoskeleton. Prosomes are protein complexes of variable subunit composition, including occasionally a small RNA, which were originally observed as trans-acting factors in untranslated mRNPs. Constituting also the proteolytic core of the 26S proteasomes, they are also called "multicatalytic proteinase (MCP) complexes" or "20S-Proteasomes." In Triton X-100-extracted epithelial, fibroblastic, and muscle cells, prosome particles were found associated primarily with the IFs (Olink-Coux et al., 1994). Application of "instantaneous fixation" has now led to the new observation that a major fraction of prosome particles, composed of specific sets of subunits, is distributed in variable proportions between the IFs and the microfilament/ stress fiber system in PtK1 epithelial cells and human fibroblasts. Electron microscopy using gold-labeled antibodies confirms this dual localization on classical whole mounts and on cells exposed to instantaneous fixation. In contrast to the resistance of the prosome-IF association, a variable fraction of the prosome particles is released from the actin cytoskeleton by Triton X-100 when applied prior to fixation. Moreover, in vitro copolymerization of prosomes with G-actin made it possible to observe "ladder-like" filamentous structures in the electron microscope, in which the prosome particles, like the "rungs of a ladder," laterally crosslink two or more actin filaments in a regular pattern. These results demonstrate that prosomes are bound in the cell not only to IFs but also to the actin cytoskeleton and, furthermore, not only within large M(r) complexes (possibly mRNPs and/or 26S proteasomes), but also directly, as individual prosome particles.
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