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Alpha Actinin 2

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Georgine Faulkner – One of the best experts on this subject based on the ideXlab platform.

  • BPAG1 isoform-b: Complex distribution pattern in striated and heart muscle and association with plectin and α-Actinin
    Experimental cell research, 2009
    Co-Authors: Marie-france Steiner-champliaud, Georgine Faulkner, Yann Schneider, Bertrand Favre, Frédérique Paulhe, Silke Praetzel-wunder, Patryk Konieczny, Marianne Raith, Gerhard Wiche, Adijat Adebola
    Abstract:

    BPAG1-b is the major muscle-specific isoform encoded by the dystonin gene, which expresses various protein isoforms belonging to the plakin protein family with complex, tissue-specific expression profiles. Recent observations in mice with either engineered or spontaneous mutations in the dystonin gene indicate that BPAG1-b serves as a cytolinker important for the establishment and maintenance of the cytoarchitecture and integrity of striated muscle. Here, we studied in detail its distribution in skeletal and cardiac muscles and assessed potential binding partners. BPAG1-b was detectable in vitro and in vivo as a high molecular mass protein in striated and heart muscle cells, co-localizing with the sarcomeric Z-disc protein AlphaActinin2 and partially with the cytolinker plectin as well as with the intermediate filafilament protein desmin. Ultrastructurally, like AlphaActinin2, BPAG1-b was predominantly localized at the Z-discs, adjacent to desmin-containing structures. BPAG1-b was able to form complexes with both plectin and AlphaActinin2, and its NH(2)-terminus, which contains an actin-binding domain, directly interacted with that of plectin and AlphaActinin. Moreover, the protein level of BPAG1-b was reduced in muscle tissues from plectin-null mutant mice versus wild-type mice. These studies provide new insights into the role of BPAG1-b in the cytoskeletal organization of striated muscle.

  • Solution structure of ZASP PDZ domain; implications for sarcomere ultrastructure and enigma family redundancy.
    Structure (London England : 1993), 2004
    Co-Authors: R. Andrew Atkinson, Georgine Faulkner, Remo Guerrini, Geoff Kelly, Catherine Joseph, Steven R. Martin, Frederick W. Muskett, Alberto Pallavicini, Annalisa Pastore
    Abstract:

    Z band alternately spliced PDZ-containing protein (ZASP) is a sarcomere Z disk protein expressed in human cardiac and skeletal muscle that is thought to be involved in a dominant familial dilated cardiomyopathy. The N-terminal PDZ domain of ZASP interacts with the C terminus of AlphaActinin2, the major component of the Z disk, probably by forming a ternary complex with titin Z repeats. We have determined the structure of ZASP PDZ by NMR and showed that it is a classical class 1 PDZ domain that recognizes the carboxy-terminal sequence of an AlphaActinin2 calmodulin-like domain with micromolar affinity. We also characterized the role of each component in the ternary complex ZASP/AlphaActinin2/titin, showing that the AlphaActinin2/ZASP PDZ interaction involves a binding surface distinct from that recognized by the titin Z repeats. ZASP PDZ structure was used to model other members of the enigma family by homology and to predict their abilities to bind AlphaActinin2.

  • Telethonin protein expression in neuromuscular disorders.
    Biochimica et biophysica acta, 2002
    Co-Authors: Mariz Vainzof, Alan H Beggs, Georgine Faulkner, Eloisa S. Moreira, Oscar T. Suzuki, Georgio Valle, Olli Carpén, Alberto F. Ribeiro, Edmar Zanoteli, Juliana Gurgel-gianneti
    Abstract:

    Telethonin is a 19-kDa sarcomeric protein, localized to the Z-disc of skeletal and cardiac muscles. Mutations in the telethonin gene cause limb-girdle muscular dystrophy type 2G (LGMD2G). We investigated the sarcomeric integrity of muscle fibers in LGMD2G patients, through double immunofluorescence analysis for telethonin with three sarcomeric proteins: titin, AlphaActinin2, and myotilin and observed the typical cross striation pattern, suggesting that the Z-line of the sarcomere is apparently preserved, despite the absence of telethonin. Ultrastructural analysis confirmed the integrity of the sarcomeric architecture. The possible interaction of telethonin with other proteins responsible for several forms of neuromuscular disorders was also analyzed. Telethonin was clearly present in the rods in nemaline myopathy (NM) muscle fibers, confirming its localization to the Z-line of the sarcomere. Muscle from patients with absent telethonin showed normal expression for the proteins dystrophin, sarcoglycans, dysferlin, and calpain-3. Additionally, telethonin showed normal localization in muscle biopsies from patients with LGMD2A, LGMD2B, sarcoglycanopathies, and Duchenne muscmuscular dystrophy (DMD). Therefore, the primary deficiency of calpain-3, dysferlin, sarcoglycans, and dystrophin do not seem to alter telethonin expression.

Hofmann Franz – One of the best experts on this subject based on the ideXlab platform.

  • Abstract 17124: Myoscape Controls Cardiomyocyte Calcium Cycling and Contractile Function in vivo via Regulation of L-type Calcium Channel Surface Expression
    Circulation, 2014
    Co-Authors: Matthias Eden, Benjamin Meder, Mirko Voelkers, Rainer Will, Montatip Poomvanicha, Katrin Domes, Alexander Bernt, Christophe Heymes, Wolfgang Rottbauer, Hofmann Franz
    Abstract:

    Alterations in cardiomyocyte calcium cycling have been shown to play a major role in the pathophysiology of contractile dysfunction, hypertrophy and the progression of heart failure. The L-type Ca2+channel controls calcium entry and subsequent calcium-induced calcium release. Here we report a novel muscle enriched protein termed Myoscape which directly interacts with the distal C-terminus of the L-type Ca2+channel (LTCC) and cardiac AlphaActinin 2. Knockdown of Myoscape in adult rat ventricular cardiomyocytes (ARVCMs) leads to a decrease in global calcium transients, with smaller Ca2+ amplitudes (n=4, p

  • abstract 17124 myoscape controls cardiomyocyte calcium cycling and contractile function in vivo via regulation of l type calcium channel surface expression
    Circulation, 2014
    Co-Authors: Matthias Eden, Benjamin Meder, Mirko Voelkers, Rainer Will, Montatip Poomvanicha, Katrin Domes, Alexander Bernt, Christophe Heymes, Wolfgang Rottbauer, Hofmann Franz
    Abstract:

    Alterations in cardiomyocyte calcium cycling have been shown to play a major role in the pathophysiology of contractile dysfunction, hypertrophy and the progression of heart failure. The L-type Ca2+channel controls calcium entry and subsequent calcium-induced calcium release. Here we report a novel muscle enriched protein termed Myoscape which directly interacts with the distal C-terminus of the L-type Ca2+channel (LTCC) and cardiac AlphaActinin 2. Knockdown of Myoscape in adult rat ventricular cardiomyocytes (ARVCMs) leads to a decrease in global calcium transients, with smaller Ca2+ amplitudes (n=4, p<0.001), lower diastolic Ca2+content and a prolonged time to peak. Consistently, analysis of single LTCC currents in ARVCM confirmed a significant reduction upon Myoscape ablation. Conversely, overexpression of Myoscape significantly increases global Ca2+transients and enhances LTCC currents. Moreover, overexpression of Myoscape almost completely restores decreased LTCC currents in failing ARVCMs. As a functional consequence, knockdown of Myoscape significantly reduced contractility of ARVCM, as assessed by fractional shortening measurements (n=3, p<0.001). Myoscape knockout mice develop reduced fractional shortening after 8 weeks which progresses to advanced cardiomyopathy after one year follow up (FS 51.7% ±4.2. vs. 33.3%±3.7, n=10). After 4 weeks of aortic constriction Myoscape null mice showed deteriorated contractile function with ventricular dilatation, enhanced fibrosis and increased pulmonary blood congestion as compared to wildtype mice. Myoscape KO’s showed increased heart weight to tibia length ratios and developed significantly exaggerated cardiomyocyte hypertrophy. Mechanistically, myoscape KO mice showed significantly reduced L-Type Ca2+currents, cell capacity and current densities (pA/pF 3.72±0.4 vs. 2.48±0.2) without affection of CDI and CDF. Instead, loss of Myoscape leads to reduced plasma membrane content of LTCC and its stabilizing agent Alpha Actinin 2 in vitro and in vivo, as assessed by surface membrane biotinylation assays and confocal immunofluorescence microscopy. Taken together, we have identified a novel modulator of cardiomyocyte L-type calcium channels and contractile function.

Alan H Beggs – One of the best experts on this subject based on the ideXlab platform.

  • Cell Membrane Expression of Cardiac Sodium Channel Nav1.5 Is Modulated by α-Actinin2 Interaction
    Biochemistry, 2010
    Co-Authors: Rahima Ziane, Alan H Beggs, Hai Huang, Behzad Moghadaszadeh, Georges Levesque, Mohamed Chahine
    Abstract:

    Cardiac sodium channel Na(v)1.5 plays a critical role in heart excitability and conduction. The molecular mechanism that underlies the expression of Na(v)1.5 at the cell membrane is poorly understood. Previous studies demonstrated that cytoskeleton proteins can be involved in the regulation of cell surface expression and localization of several ion channels. We performed a yeast two-hybrid screen to identify Na(v)1.5-associated proteins that may be involved in channel function and expression. We identified AlphaActinin2 as an interacting partner of the cytoplasmic loop connecting domains III and IV of Na(v)1.5 (Na(v)1.5/LIII-IV). Co-immunoprecipitation and His(6) pull-down assays confirmed the physical association between Na(v)1.5 and AlphaActinin2 and showed that the spectrin-like repeat domain is essential for binding of AlphaActinin2 to Na(v)1.5. Patch-clamp studies revealed that the interaction with AlphaActinin2 increases sodium channel density without changing their gating properties. Consistent with these findings, coexpression of AlphaActinin2 and Na(v)1.5 in tsA201 cells led to an increase in the level of expression of Na(v)1.5 at the cell membrane as determined by cell surface biotinylation. Lastly, immunostaining experiments showed that AlphaActinin2 was colocalized with Na(v)1.5 along the Z-lines and in the plasma membrane. Our data suggest that AlphaActinin2, which is known to regulate the functional expression of the potassium channels, may play a role in anchoring Na(v)1.5 to the membrane by connecting the channel to the actin cytoskeleton network.

  • Dynamic regulation of endothelial NOS mediated by competitive interaction with α-Actinin-4 and calmodulin
    FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2008
    Co-Authors: Yukio Hiroi, Alan H Beggs, Zhongmin Guo, James K. Liao
    Abstract:

    AlphaActinins are critical components of the actin cytoskeleton. Here we show that AlphaActinins serve another important biological function by binding to and competitively inhibiting calcium-dependent activation of endothelial NOS (eNOS). AlphaActinin2 was found to associate with eNOS in a yeast two-hybrid screen. In vascular endothelial cells, which only express AlphaActinin-1 and -4, AlphaActinin-4 interacted and colocalized with eNOS. Addition of AlphaActinin-4 directly inhibited eNOS recombinant protein, and overexpression of AlphaActinin-4 inhibited eNOS activity in eNOS-transfected COS-7 cells and bovine aortic endothelial cells (BAECs). In contrast, knockdown of AlphaActinin-4 by siRNA increased eNOS activity in BAECs. The AlphaActinin-4-binding site on eNOS was mapped to a central region comprising the calmodulin-binding domain, and the eNOS-binding site on AlphaActinin-4 was mapped to the fourth spectrin-like rod domain, R4. Treatment of endothelial cells with a calcium ionophore, A23187, decreased AlphaActinin-4-eNOS interaction, leading to translocation of AlphaActinin-4 from plasma membrane to cytoplasm. Indeed, addition of calmodulin displaced AlphaActinin-4 binding to eNOS and increased eNOS activity. These findings indicate that eNOS activity in vascular endothelial cells is tonically and dynamically regulated by competitive interaction with AlphaActinin-4 and calmodulin.

  • Telethonin protein expression in neuromuscular disorders.
    Biochimica et biophysica acta, 2002
    Co-Authors: Mariz Vainzof, Alan H Beggs, Georgine Faulkner, Eloisa S. Moreira, Oscar T. Suzuki, Georgio Valle, Olli Carpén, Alberto F. Ribeiro, Edmar Zanoteli, Juliana Gurgel-gianneti
    Abstract:

    Telethonin is a 19-kDa sarcomeric protein, localized to the Z-disc of skeletal and cardiac muscles. Mutations in the telethonin gene cause limb-girdle muscular dystrophy type 2G (LGMD2G). We investigated the sarcomeric integrity of muscle fibers in LGMD2G patients, through double immunofluorescence analysis for telethonin with three sarcomeric proteins: titin, AlphaActinin2, and myotilin and observed the typical cross striation pattern, suggesting that the Z-line of the sarcomere is apparently preserved, despite the absence of telethonin. Ultrastructural analysis confirmed the integrity of the sarcomeric architecture. The possible interaction of telethonin with other proteins responsible for several forms of neuromuscular disorders was also analyzed. Telethonin was clearly present in the rods in nemaline myopathy (NM) muscle fibers, confirming its localization to the Z-line of the sarcomere. Muscle from patients with absent telethonin showed normal expression for the proteins dystrophin, sarcoglycans, dysferlin, and calpain-3. Additionally, telethonin showed normal localization in muscle biopsies from patients with LGMD2A, LGMD2B, sarcoglycanopathies, and Duchenne muscular dystrophy (DMD). Therefore, the primary deficiency of calpain-3, dysferlin, sarcoglycans, and dystrophin do not seem to alter telethonin expression.

Matthias Eden – One of the best experts on this subject based on the ideXlab platform.

  • Abstract 17124: Myoscape Controls Cardiomyocyte Calcium Cycling and Contractile Function in vivo via Regulation of L-type Calcium Channel Surface Expression
    Circulation, 2014
    Co-Authors: Matthias Eden, Benjamin Meder, Mirko Voelkers, Rainer Will, Montatip Poomvanicha, Katrin Domes, Alexander Bernt, Christophe Heymes, Wolfgang Rottbauer, Hofmann Franz
    Abstract:

    Alterations in cardiomyocyte calcium cycling have been shown to play a major role in the pathophysiology of contractile dysfunction, hypertrophy and the progression of heart failure. The L-type Ca2+channel controls calcium entry and subsequent calcium-induced calcium release. Here we report a novel muscle enriched protein termed Myoscape which directly interacts with the distal C-terminus of the L-type Ca2+channel (LTCC) and cardiac AlphaActinin 2. Knockdown of Myoscape in adult rat ventricular cardiomyocytes (ARVCMs) leads to a decrease in global calcium transients, with smaller Ca2+ amplitudes (n=4, p

  • abstract 17124 myoscape controls cardiomyocyte calcium cycling and contractile function in vivo via regulation of l type calcium channel surface expression
    Circulation, 2014
    Co-Authors: Matthias Eden, Benjamin Meder, Mirko Voelkers, Rainer Will, Montatip Poomvanicha, Katrin Domes, Alexander Bernt, Christophe Heymes, Wolfgang Rottbauer, Hofmann Franz
    Abstract:

    Alterations in cardiomyocyte calcium cycling have been shown to play a major role in the pathophysiology of contractile dysfunction, hypertrophy and the progression of heart failure. The L-type Ca2+channel controls calcium entry and subsequent calcium-induced calcium release. Here we report a novel muscle enriched protein termed Myoscape which directly interacts with the distal C-terminus of the L-type Ca2+channel (LTCC) and cardiac AlphaActinin 2. Knockdown of Myoscape in adult rat ventricular cardiomyocytes (ARVCMs) leads to a decrease in global calcium transients, with smaller Ca2+ amplitudes (n=4, p<0.001), lower diastolic Ca2+content and a prolonged time to peak. Consistently, analysis of single LTCC currents in ARVCM confirmed a significant reduction upon Myoscape ablation. Conversely, overexpression of Myoscape significantly increases global Ca2+transients and enhances LTCC currents. Moreover, overexpression of Myoscape almost completely restores decreased LTCC currents in failing ARVCMs. As a functional consequence, knockdown of Myoscape significantly reduced contractility of ARVCM, as assessed by fractional shortening measurements (n=3, p<0.001). Myoscape knockout mice develop reduced fractional shortening after 8 weeks which progresses to advanced cardiomyopathy after one year follow up (FS 51.7% ±4.2. vs. 33.3%±3.7, n=10). After 4 weeks of aortic constriction Myoscape null mice showed deteriorated contractile function with ventricular dilatation, enhanced fibrosis and increased pulmonary blood congestion as compared to wildtype mice. Myoscape KO’s showed increased heart weight to tibia length ratios and developed significantly exaggerated cardiomyocyte hypertrophy. Mechanistically, myoscape KO mice showed significantly reduced L-Type Ca2+currents, cell capacity and current densities (pA/pF 3.72±0.4 vs. 2.48±0.2) without affection of CDI and CDF. Instead, loss of Myoscape leads to reduced plasma membrane content of LTCC and its stabilizing agent Alpha Actinin 2 in vitro and in vivo, as assessed by surface membrane biotinylation assays and confocal immunofluorescence microscopy. Taken together, we have identified a novel modulator of cardiomyocyte L-type calcium channels and contractile function.

Kathryn N North – One of the best experts on this subject based on the ideXlab platform.

  • The evolution of skeletal muscle performance: gene duplication and divergence of human sarcomeric α-Actinins
    BioEssays : news and reviews in molecular cellular and developmental biology, 2010
    Co-Authors: Monkol Lek, Kate G. R. Quinlan, Kathryn N North
    Abstract:

    In humans, there are two skeletal muscle AlphaActinins, encoded by ACTN2 and ACTN3, and the ACTN3 genotype is associated with human athletic performance. Remarkably, approximately 1 billion people worldwide are deficient in AlphaActinin-3 due to the common ACTN3 R577X polymorphism. The AlphaActinins are an ancient family of actinbinding proteins with structural, signalling and metabolic functions. The skeletal muscle AlphaActinins diverged approximately 250-300 million years ago, and ACTN3 has since developed restricted expression in fast muscle fibres. Despite ACTN2 and ACTN3 retaining considerable sequence similarity, it is likely that following duplication there was a divergence in function explaining why AlphaActinin2 cannot completely compensate for the absence of AlphaActinin-3. This paper focuses on the role of skeletal muscle AlphaActinins, and how possible changes in functions between these duplicates fit in the context of gene duplication paradigms.

  • Mechanisms underlying intranuclear rod formation.
    Brain : a journal of neurology, 2007
    Co-Authors: Ana Domazetovska, Sandra T. Cooper, Majid Ghoddusi, Edna C. Hardeman, Biljana Ilkovski, Laurie S Minamide, Peter W Gunning, James R Bamburg, Kathryn N North
    Abstract:

    Specific mutations within the Alpha-skeletal actin gene (ACTA1) result in intranuclear rod myopathy (IRM), characterized by rod-like aggregates containing actin and AlphaActinin2 inside the nucleus of muscle cells. The mechanism leading to formation of intranuclear aggregates containing sarcomeric proteins and their impact on cell function and contribution to disease pathogenesis is unknown. In this study, we transfected muscle and non-muscle cells with mutants of Alpha-skeletal actin (Val163Leu, Val163Met) associated with intranuclear rod myopathy. By live-cell imaging we demonstrate that nuclear aggregates of actin form within the nuclear compartment, rather than entering the nucleus after formation in the cytoplasm, and are highly motile and dynamic structures. Thus, the nuclear environment supports the polymerization of actin and the movement and coalescence of the polymerized actin into larger structures. We show that the organization of actin within these aggregates is influenced by the binding of AlphaActinin, and that AlphaActinin is normally present in the nucleus of muscle and non-muscle cells. Furthermore, we demonstrate that, under conditions of cell stress (cytoskeletal disruption and ATP depletion), WT skeletal actin forms aggregates within the nucleus that are similar in morphology to those formed by the mutant actin, suggesting a common pathogenic mechanism for aggregate formation. Finally, we show that the presence of intranuclear actin aggregates significantly decreases the mitotic index and hence impacts on the function of the cell. Intranuclear aggregates thus likely contribute to the pathogenesis of muscle weakness in intranuclear rod myopathy.

  • C2C12 Co‐culture on a fibroblast substratum enables sustained survival of contractile, highly differentiated myotubes with peripheral nuclei and adult fast myosin expression
    Cell motility and the cytoskeleton, 2004
    Co-Authors: Sandra T. Cooper, Adam Maxwell, Eddy Kizana, Majid Ghoddusi, Edna C. Hardeman, Ian E. Alexander, David G. Allen, Kathryn N North
    Abstract:

    We describe a simple culture method for obtaining highly differentiated clonal C2C12 myotubes using a feeder layer of confluent fibroblasts, and document the expression of contractile protprotein expression and aspects of myofibre morphology using this system. Traditional culture methods using collagen– or laminin-coated tissue-culture plastic typically results in a cyclic pattern of detachment and reformation of myotubes, rarely producing myotubes of a mature adult phenotype. C2C12 co-culture on a fibroblast substratum facilitates the sustained culture of contractile myotubes, resulting in a mature sarcomeric register with evidence for peripherally migrating nuclei. Immunoblot analysis demonstrates that desmin, tropomyosin, sarcomeric actin, AlphaActinin2 and slow myosin are detected throughout myogenic differentiation, whereas adult fast myosin heavy chain isoforms, members of the dystrophin-associated complex, and AlphaActinin-3 are not expressed at significant levels until >6 days of differentiation, coincident with the onset of contractile activity. Electrical stimstimulation of mature myotubes reveals typical and reproducible calcium transients, demonstrating functional maturation with respect to calcium handling proteins. Immunocytochemical staining demonstrates a well-defined sarcomeric register throughout the majority of myotubes (70-80%) and a striated staining pattern is observed for desmin, indicating alignment of the intermediate filafilament network with the sarcomeric register. We report that culture volume affects the fusion index and rate of sarcomeric development in developing myotubes and propose that a fibroblast feeder layer provides an elastic substratum to support contractile activity and likely secretes growth factors and extracellular matrix proteins that assist myotube development.