P Cottin

Université Bordeaux 1, Talence, Aquitaine, France

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Publications (66)195.57 Total impact

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    ABSTRACT: Peroxiredoxin IV (Prx IV), a member of the peroxiredoxin family, has been shown to be involved in cell protection against radiation. Peroxiredoxins are also overexpressed and involved in the progression of several tumours. Calpains have been shown to be over-activated in alveolar rhabdomyosarcoma (ARMS). The present study focused on the possible cross-regulations between Prx IV and calpains in ARMS cells. Prx IV abundance was quantified by Western blot analysis in ARMS cells and compared with non-malignant LHCN-M2 cells. Its abundance is quantified in ARMS cells treated or untreated with calpain inhibitors moreover its mRNA expression is also quantified by real-time RT-PCR in these cells. The study showed that Prx IV is overexpressed by five times in ARMS cells when compared to non-malignant myoblasts. Moreover, the inhibition of calpains using chemical inhibitors led to a decrease in Prx IV abundance (64.32 ± 8.25 and 76.79 ± 4.60 for the precursor and secretable forms, respectively, with calpain inhibitor III treatment). It is the first time that a Prx IV calpain-dependent up-regulation is revealed. In summary, calpains may be implied in the tumour phenotype of ARMS cells especially through Prx IV regulation and may, thus, represent a potential therapeutic target to stop progression of ARMS tumour.
    Anticancer research 12/2010; 30(12):5085-9. · 1.71 Impact Factor
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    ABSTRACT: Aging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern. Although sarcopenia is well documented, the molecular mechanisms of this condition still remain unclear. The calcium-dependent proteolytic system is composed of calcium-dependent cysteine proteases named calpains. Calpains are involved in a large number of physiological processes such as muscle growth and differentiation, and pathological conditions such as muscular dystrophies. The aim of this study was to determine the involvement of this proteolytic system in the phenotype associated with sarcopenia by identifying key proteins (substrates or regulators) interacting with calpains during muscle aging. Immunoprecipitations coupled with proteomic analyses and protein identification by mass spectrometry have been undertaken. Reverse co-immunoprecipitation, cellular colocalisation by confocal microscopy and calpain-dependent in vitro proteolysis of several of the identified proteins have been also carried out. We identified ATP synthase subunit alpha and alpha actinin 3 as key partners of calpains during muscle aging. Such interactions would suggest that calpains are implicated in many processes altered during aging including cytoskeletal disorganisation and mitochondrial dysfunction.
    Biochimie 12/2010; 92(12):1923-33. · 3.14 Impact Factor
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    ABSTRACT: Rhabdomyosarcoma (RMS) are soft-tissue sarcoma commonly encountered in childhood. RMS cells can acquire invasive behavior and form metastases. The metastatic dissemination implicates many proteases among which are mu-calpain and m-calpain. Study of calpain expression and activity underline the deregulation of calpain activity in RMS. Analysis of kinetic characteristics of RMS cells, compared to human myoblasts LHCN-M2 cells, shows an important migration velocity in RMS cells. One of the major results of this study is the positive linear correlation between calpain activity and migration velocity presenting calpains as a marker of tumor aggressiveness. The RMS cytoskeleton is disorganized. Specifying the role of mu- and m-calpain using antisense oligonucleotides led to show that both calpains up-regulate alpha- and beta-actin in ARMS cells. Moreover, the invasive behavior of these cells is higher than that of LHCN-M2 cells. However, it is similar to that of non-treated LHCN-M2 cells, when calpains are inhibited. In summary, calpains may be involved in the anarchic adhesion, migration and invasion of RMS. The direct relationship between calpain activity and migration velocities or invasive behavior indicates that calpains could be considered as markers of tumor aggressiveness and as potential targets for limiting development of RMS tumor as well as their metastatic behavior.
    Experimental Cell Research 02/2010; 316(9):1587-99. · 3.56 Impact Factor
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    ABSTRACT: Calpain 3 is a calcium-dependent cysteine protease that is primarily expressed in skeletal muscle and is implicated in limb girdle muscular dystrophy type 2A. To date, its best characterized function is located within the sarcomere, but this protease is found in other cellular compartments, which suggests that it exerts multiple roles. Here, we present evidence that calpain 3 is involved in the myogenic differentiation process. In the course of in vitro culture of myoblasts to fully differentiated myotubes, a population of quiescent undifferentiated "reserve cells" are maintained. These reserve cells are closely related to satellite cells responsible for adult muscle regeneration. In the present work, we observe that reserve cells express higher levels of endogenous Capn3 mRNA than proliferating myoblasts. We show that calpain 3 participates in the establishment of the pool of reserve cells by decreasing the transcriptional activity of the key myogenic regulator MyoD via proteolysis independently of the ubiquitin-proteasome degradation pathway. Our results identify calpain 3 as a potential new player in the muscular regeneration process by promoting renewal of the satellite cell compartment.
    Journal of Biological Chemistry 02/2010; 285(17):12670-83. · 4.65 Impact Factor
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    ABSTRACT: The reduced regenerative potential of muscle fibres, most likely due to a decreased number and/or function of satellite cells, could play a significant role in the progression of muscle ageing. Accumulation of reactive oxygen species has been clearly correlated to sarcopenia and could contribute to the impairment of satellite cell function. In this work we have investigated the effect of oxidative stress generated by hydrogen peroxide in cultured human skeletal muscle satellite cells. We specifically focused on the activity and regulation of calpains. These calcium-dependent proteases are known to regulate many transduction pathways including apoptosis and play a critical role in satellite cell function. In our experimental conditions, which induce an increase in calcium concentration, protein oxidation and apoptotic cell death, a significant up-regulation of calpain expression and activity were observed and ATP synthase, a major component of the respiratory chain, was identified as a calpain target. Interestingly we were able to protect the cells from these H(2)O(2)-induced effects and prevent calpain up-regulation with a natural antioxidant extracted from pine bark (Oligopin). These data strongly suggest that oxidative stress could impair satellite cell functionality via calpain-dependent pathways and that an antioxidant such as Oligopin could prevent apoptosis and calpain activation.
    Experimental Cell Research 08/2009; 316(1):115-25. · 3.56 Impact Factor
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    ABSTRACT: A novel extracellular β-fructosidase produced by Bacillus stearothermophilus has been identified and purified. The purified enzyme, obtained by using successive QEAE Sepharose fast flow and Sephacryl S300 HR columns, has a 600 kDa relative molecular weight (Mr) and is composed of 60 kDa subunits indicating a multimeric structure. The pH and temperature for optimal activity are 6.5 and 65°C respectively, the enzyme being thermostable at this temperature. The apparent Km values for sucrose and inulin are 3.56 mmol l-1 and 1 mmol l-1 respectively, the total invertase/total inulinase ratio being 4.
    Letters in Applied Microbiology 06/2008; 19(6):410 - 413. · 1.63 Impact Factor
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    ABSTRACT: The calcium-dependent proteolytic system is composed of cysteine proteases named calpains. They are ubiquitous or tissue-specific enzymes. The two best characterised isoforms are the ubiquitously expressed mu- and m-calpains. Besides its regulation by calcium, calpain activity is tightly controlled by calpastatin, the specific endogenous inhibitor, binding to phospholipids, autoproteolysis and phosphorylation. Calpains are responsible for limited proteolytic events. Among the multitude of substrates identified so far are cytoskeletal and membrane proteins, enzymes and transcription factors. Calpain activity is involved in a large number of physiological and pathological processes. In this review, we will particularly focus on the implication of the calcium-dependent proteolytic system in relation to muscle physiology. Because of their ability to remodel cytoskeletal anchorage complexes, calpains play a major role in the regulation of cell adhesion, migration and fusion, three key steps of myogenesis. Calcium-dependent proteolysis is also involved in the control of cell cycle. In muscle tissue, in particular, calpains intervene in the regeneration process. Another important class of calpain substrates belongs to apoptosis regulating factors. The proteases may thus play a role in muscle cell death, and as a consequence in muscle atrophy. The relationships between calcium-dependent proteolysis and muscle dysfunctions are being further developed in this review with a particular emphasis on sarcopenia.
    Biochimie 03/2008; 90(2):359-68. · 3.14 Impact Factor
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    ABSTRACT: Aging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern with high socio-economics implications. Although sarcopenia is well documented, the aetiology of this condition still remains poorly understood. Calpains are ubiquitous proteases regulated in part by a specific inhibitor, calpastatin. They are well known to have major implications in muscle growth and differentiation. The aim of the present study was to determine if this proteolytic system could be involved in the phenotype associated with sarcopenia. Calpains and calpastatin levels, subcellular distributions and activities were compared between muscles from 3 and 24 months old rats. Altogether, the results we obtained showed an overall increase in calpain activities associated with muscle aging. These findings suggest that the calcium-dependent proteolytic system is indeed involved in sarcopenia.
    Experimental Gerontology 12/2007; 42(11):1088-98. · 3.91 Impact Factor
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    ABSTRACT: Caveolae are specialised RAFTs (detergent-resistant membrane microdomains enriched in cholesterol and glycosphingolipids). Caveolin, the main caveolae protein, is essential to the organisation of proteins and lipids, and interacts with numerous mediating proteins through a 'Caveolin Scalfolding Domain'. Consequently, caveolae play a major role in signal transduction and appear to be veritable signalling platforms. In muscle cells, caveolae are essential for fusion and differentiation, and are also implicated in a type of muscular dystrophy (LGMD1C). In a preceding work, we demonstrated the presence of active milli-calpain (m-calpain) in myotube caveolae. Calpains are calcium-dependent proteases involved in several cellular processes, including myoblast fusion and migration, PKC-mediated intracellular signalling and remodelling of the cytoskeleton. For the first time, we have proved the cholesterol-dependent localisation of m-calpain in the caveolae of C(2)C(12) myotubes. Calpain-dependent caveolae involvement in myoblast fusion was also strongly suggested. Furthermore, eight differentially expressed caveolae associated proteins were identified by 2-DE and LC-MS/MS analyses using an m-calpain antisense strategy. This proteomic study also demonstrates the action of m-calpain on vimentin, desmin and vinculin in myotube caveolae and suggests m-calpain's role in several mitochondrial pathways.
    PROTEOMICS 10/2007; 7(18):3289-98. · 4.13 Impact Factor
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    ABSTRACT: Recent research carried out in our laboratory has shown that IGF-1, TGF-beta1, and insulin were able to strongly stimulate myoblast migration by increasing milli-calpain expression and activity. However, the signalling pathways involved in these phenomena remain unknown. The aim of this study was to identify the signalling pathway(s) responsible for the effects of IGF-1, TGF-beta1, and insulin on myoblast migration and on milli-calpain expression and activity. For this purpose, wound healing assays were carried out in the presence of growth factors with or without specific inhibitors of ERK/MAP kinase and PI3K/Akt pathways. The results clearly showed that the inhibition of the ERK/MAP kinase pathway prevents the effects of growth factors on myoblast migration. Secondly, the expression and the activity of milli-calpain were studied in cells treated with growth factor, alone or with ERK/MAP kinase inhibitor. The results demonstrated that the up-regulation of milli-calpain expression and activity was mediated by the ERK/MAP kinase pathway. Finally, the possible implication of MyoD and myogenin, myogenic regulatory factors able to regulate milli-calpain expression, was studied. Taken together our results clearly showed that the ERK/MAP kinase signalling pathway is responsible for the effects of the three growth factors on myoblast migration and on milli-calpain expression and activity. On the opposite, the PI3K/Akt signalling pathway, MyoD and myogenin seem to be not implicated in these phenomena.
    The International Journal of Biochemistry & Cell Biology 02/2007; 39(6):1177-89. · 4.15 Impact Factor
  • Neuromuscular Disorders - NEUROMUSCULAR DISORD. 01/2007; 17(9):792-792.
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    ABSTRACT: The calcium-dependent proteolytic system is a large family of well-conserved ubiquitous and tissue-specific proteases, known as calpains, and an endogenous inhibitor, calpastatin. Ubiquitous calpains are involved in many physiological phenomena, such as the cell cycle, muscle cell differentiation, and cell migration. This study investigates the regulation of crucial steps of cell motility, myoblast adhesion and spreading, by calpains. Inhibition of each ubiquitous calpain isoform by antisense strategy pinpointed the involvement of each of these proteases in myoblast adhesion and spreading. Moreover, the actin cytoskeleton and microtubules were observed in transfected cells, demonstrating that each ubiquitous calpain could be involved in the actin fiber organization. C2C12 cells with reduced mu- or m-calpain levels have a rounded morphology and disorganized stress fibers, but no modification in the microtubule cytoskeleton. Antisense strategy directed against MARCKS, a calpain substrate during C2C12 migration, showed that this protein could play a role in stress fiber polymerization. A complementary proteomic analysis using C2C12 cells over-expressing calpastatin indicated that two proteins were under-expressed, while six, which are involved in the studied phenomena, were overexpressed after calpain inhibition. The possible role of these proteins in adhesion, spreading, and migration was discussed.
    Cell Motility and the Cytoskeleton 05/2006; 63(4):193-207. · 4.19 Impact Factor
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    ABSTRACT: Previous research in our laboratory has already shown the importance of the role played by ubiquitous calpains during myoblast migration. The aim of this study was to investigate calpain expression during myoblast migration and, to enhance this phenomenon via calpain stimulation. Ubiquitous calpains are members of a large family of calcium-dependent cysteine proteases. They play an important role in numerous biological and pathological phenomena, such as signal transduction, apoptosis, cell-cycle regulation, cell spreading, adhesion, invasion, myogenesis, and motility. Myoblast migration is a crucial step in myogenesis, as it is necessary for myoblast alignment and fusion to form myotubes. This study started by examining changes in calpain expression during migration, then investigated the possibility of activating myoblast migration via the stimulation of calpain expression and/or activity. The migration rate of myoblasts overexpressing mu- or milli-calpain was quantified. The results showed that calpain overexpression dramatically inhibited myoblast migration. Growth-factor treatments were then used to enhance myoblast migration. The results showed that treatment with IGF-1, TGF-beta1, or insulin induced a major increase in migration and caused a significant increase in m-calpain expression and activity. The increase in migration was totally inhibited by adding calpeptin, a calpain-specific inhibitor. These findings suggest that milli-calpain is involved in growth factor-mediated migration.
    The International Journal of Biochemistry & Cell Biology 02/2006; 38(12):2049-63. · 4.15 Impact Factor
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    ABSTRACT: We have previously shown that calpain promotes myoblast fusion by acting on protein kinase C-alpha and the cytosolic phosphorylated form of MARCKS. In other cell types, various isoforms of calpain, PKC alpha and MARCKS were found associated with caveolae. These vesicular invaginations of the plasma membrane are essential for myoblast fusion and differentiation. We have isolated caveolae from myoblasts and studied the presence of calpain isoforms and their possible effects on signalling mediated by caveolae-associated PKC. Our results show that milli-calpain co-localizes with myoblast caveolae. Futhermore we provide evidence, using a calcium ionophore and a specific inhibitor of calpains (calpastatin peptide), that milli-calpain reduces the PKC alpha and MARCKS content in these structures. Purified milli-calpain causes the appearance of the active catalytic fragment of PKC alpha (PKM), without having an effect on MARCKS. Addition of phorbol myristate acetate, an activator of PKC, induces tranlocation of PKC alpha towards caveolae and results in a significant reduction of MARCKS associated with caveolae. This phenomenon is not observed when a PKC alpha inhibitor is added at the same time. We conclude that the presence of biologically active milli-calpain within myoblast caveolae induces, in a PKC alpha-dependent manner, MARCKS translocation towards the cytosol. Such a localised signalling event may be essential for myoblast fusion and differentiation.
    The International Journal of Biochemistry & Cell Biology 10/2005; 37(9):1900-10. · 4.15 Impact Factor
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    ABSTRACT: MARCKS (myristoylated alanine-rich C kinase substrate) is a major cytoskeletal protein substrate of PKC (protein kinase C) whose cellular functions are still unclear. However numerous studies have implicated MARCKS in the stabilization of cytoskeletal structures during cell differentiation. The present study was performed to investigate the potential role of Ca(2+)-dependent proteinases (calpains) during myogenesis via proteolysis of MARCKS. It was first demonstrated that MARCKS is a calpain substrate in vitro. Then, the subcellular expression of MARCKS was examined during the myogenesis process. Under such conditions, there was a significant decrease in MARCKS expression associated with the appearance of a 55 kDa proteolytic fragment at the time of intense fusion. The addition of calpastatin peptide, a specific calpain inhibitor, induced a significant decrease in the appearance of this fragment. Interestingly, MARCKS proteolysis was dependent of its phosphorylation by the conventional PKCalpha. Finally, ectopic expression of MARCKS significantly decreased the myoblast fusion process, while reduced expression of the protein with antisense oligonucleotides increased the fusion. Altogether, these data demonstrate that MARCKS proteolysis is necessary for the fusion of myoblasts and that cleavage of the protein by calpains is involved in this regulation.
    Biochemical Journal 10/2004; 382(Pt 3):1015-23. · 4.65 Impact Factor
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    ABSTRACT: Several studies have already demonstrated that micro- and milli-calpains (CAPN 1-CAPN 2), calcium-dependent intracellular cysteine-proteases are involved in many biological phenomenon including muscle growth and development. More particularly, recent studies have demonstrated that milli-calpain is implicated in myoblast fusion. Moreover, in primary muscle cells, these proteases do not appear simultaneously throughout muscle cell differentiation. Because micro- and milli-calpains do not have the same intracellular localization, it appears likely that these two calcium-dependent proteases have different biological roles during muscle cell differentiation. The goal of this study is to determine the role of micro-calpain. We therefore, have developed a muscle cell line in which micro-calpain is over-expressed, using the inducible Tet Regulated Expression System. The outcome is observed by following the behavior of different proteins, considered to be potential substrates of the protease. The present study shows important decreases in the expression level of ezrin (68%), vimentin (64%) and caveolin 3 (76%) whereas many other cytoskeletal proteins remain remarkably stable. Concerning the myogenic transcription factors, only the level of myogenin decreased (59%) after the over-expression of micro-calpain. Ultra structural studies have shown that the myofibrils formed near the cell periphery are normally oriented, lying along the longitudinal axis. This regularity is lost progressively towards the cell center where the cytoskeleton presented an increasing disorganization. All these results indicate that micro-calpain is involved in regulation pathway of myogenesis via at least its action on ezrin, vimentin, caveolin 3 and myogenin, a muscle transcription factor.
    The International Journal of Biochemistry & Cell Biology 05/2004; 36(4):728-43. · 4.15 Impact Factor
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    ABSTRACT: Cell migration is a fundamental cellular function particularly during skeletal muscle development. Ubiquitous calpains are well known to play a pivotal role during muscle differentiation, especially at the onset of fusion. In this study, the possible positive regulation of myoblast migration by calpains, a crucial step required to align myoblasts to permit them to fuse, was investigated. Inhibition of calpain activity by different pharmacological inhibitors argues for the involvement of these proteinases during the migration of myoblasts. Moreover, a clonal cell line that fourfold overexpresses calpastatin, the endogenous inhibitor of calpains, and that exhibits deficient calpain activities was obtained. The results showed that the migratory capacity of C2C12 and fusion into multinucleated myotubes were completely prevented in these clonal cells. Calpastatin-overexpressing myoblasts unable to migrate were characterized by rounded morphology, the loss of membrane extensions, the disorganization of stress fibers and exhibited a major defect in new adhesion formation. Surprisingly, the proteolytic patterns of desmin, talin, vinculin, focal adhesion kinase (FAK) and ezrin, radixin, moesin (ERM) proteins are the same in calpastatin-overexpressing myoblasts as compared to control cells. However, an important accumulation of myristoylated alanine-rich C kinase substrate (MARCKS) was observed in cells showing a reduced calpain activity, suggesting that the proteolysis of this actin-binding protein is calpain-dependent and could be involved in both myoblast adhesion and migration.
    Experimental Cell Research 02/2004; 292(1):187-200. · 3.56 Impact Factor
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    ABSTRACT: Calpains, also called calcium activated neutral cysteine proteases are presently known to play pivotal roles in physiological and biological phenomena such as signal transduction, cell spreading and motility, apoptosis, regulation of cell cycle and regulation of muscle cell differentiation. Concerning this last point, calpains have been shown to play a crucial role during the earlier myogenesis. In this study we have analyzed the involvement of calpains during an important step of myogenesis: myoblast migration. Our findings show that myoblast migration was drastically reduced when the expression of micro- and m-calpain was decreased. We have also observed that MARCKS (myristoylated alanine rich C kinase substrate), a protein localized at focal adhesion sites, was significantly accumulated when the expression levels of calpains were decreased. Also, using phorbol myristate acetate, (an activator of PKC) and plasmids carrying the full-length cDNA of MARCKS or a cDNA fragment lacking the phosphorylation site domain, we demonstrated that normal myoblast migration is dependent on MARCKS phosphorylation and localization.
    Biology of the Cell 01/2004; 95(9):615-23. · 3.49 Impact Factor
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    ABSTRACT: We investigated the status and the regulation of the cyclin-dependent kinases (CDK) inhibitor p27(Kip1) in a choroidal melanoma tumor-derived cell line (OCM-1). By contrast to normal choroidal melanocytes, the expression level of p27(Kip1) was low in these cells and the mitogen-activated protein (MAP) kinase pathway was constitutively activated. Genetic or chemical inhibition of this pathway induced p27(Kip1) accumulation, whereas MAP kinase reactivation triggered a down-regulation of p27(Kip1) that could be partially reversed by calpain inhibitors. In good accordance, ectopic expression of the cellular calpain inhibitor calpastatin led to an increase of endogenous p27(Kip1) expression. In vitro, p27(Kip1) was degraded by calpains, and OCM-1 cell extracts contained a calcium-dependent p27(Kip1) degradation activity. MAP kinase inhibition partially inhibited both calpain activity and calcium-dependent p27(Kip1) degradation by cellular extracts. Immunofluorescence labeling and subcellular fractionation revealed that p27(Kip1) was in part localized in the cytoplasmic compartment of OCM-1 cells but not of melanocytes, and accumulated into the nucleus upon MAP kinase inhibition. MAP kinase activation triggered a cytoplasmic translocation of the protein, as well as a change in its phosphorylation status. This CRM-1-dependent cytoplasmic translocation was necessary for MAP kinase- and calpain-dependent degradation. Taken together, these data suggest that in tumor-derived cells, p27(Kip1) could be degraded by calpains through a MAP kinase-dependent process, and that abnormal cytoplasmic localization of the protein, probably linked to modifications of its phosphorylation state, could be involved in this alternative mechanism of degradation.
    Journal of Biological Chemistry 05/2003; 278(14):12443-51. · 4.65 Impact Factor
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    ABSTRACT: The calcium-activated cysteine protease m-calpain plays a pivotal role during the earlier stages of myogenesis, particularly during fusion. The enzyme is a heterodimer, encoded by the genes capn2, for the large subunit, and capn4, for the small subunit. To study the regulation of m-calpain, the DNA sequence upstream of capn2 was analyzed for promoter elements, revealing the existence of five consensus-binding sites (E-box) for several myogenic regulatory factors and one binding site for myocyte enhancer factor-2 (MEF-2). Transient transfections with reporter gene constructs containing the E-box revealed that MyoD presents a high level of transactivation of reporter constructs containing this region, in particular the sequences including the MEF-2/E4-box. In addition, over-expression of various myogenic factors demonstrated that MyoD and myogenin with much less efficiency, can up-regulate capn2, both singly and synergistically, while Myf5 has no effect on synthesis of the protease. Experiments with antisense oligonucleotides directed against each myogenic factor revealed that MyoD plays a specific and pivotal role during capn2 regulation, and cannot be replaced wholly by myogenin and Myf5.
    Journal of Molecular Biology 03/2003; 326(2):453-65. · 3.91 Impact Factor