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Kathryn N North - One of the best experts on this subject based on the ideXlab platform.
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why is Alpha Actinin 3 deficiency so common in the general population the evolution of athletic performance
Twin Research and Human Genetics, 2008Co-Authors: Kathryn N NorthAbstract:'We can now explain how this common genetic variation influences athletic performance as well as why it has become so common in the general population. There is a fascinating link between factors that influence survival in ancient humans and the factors that contribute to athletic abilities in modern man.' The human ACTN3 gene encodes the protein Alpha-Actinin-3, a component of the contractile apparatus in fast skeletal muscle fibers. In 1999, we identified a common polymorphism in ACTN3 (R577X) that results in absence of Alpha-Actinin-3 in more than one billion people worldwide, despite the ACTN3 gene being highly conserved during human evolution. In 2003, we demonstrated that ACTN3 genotype influences elite athletic performance, and the association between ACTN3 genotype and skeletal muscle performance has since been replicated in athletes and non-athlete cohorts. We have also studied the evolution of the R577X allele during human evolution and demonstrated that the null (X) allele has undergone strong, recent positive selection in Europeans and Asian populations. We have developed an Actn3 knockout mouse model that replicates Alpha-Actinin-3 deficiency in humans and has already provided insight into the role of Alpha-Actinin-3 in the regulation of skeletal muscle metabolism, fibre size, muscle mass and contractile properties. In particular, mouse muscle lacking Alpha-Actinin-3 uses energy more efficiently, with the fast fibers displaying metabolic and contractile properties of slow oxidative fibers. While this favors endurance activities, the trade off is that the muscle cannot generate the rapid contractions needed to excel in sprinting. We propose that the shift towards more efficient aerobic muscle metabolism associated with Alpha-Actinin-3 deficiency also underlies the adaptive benefit of the 577X allele. Our future studies will focus on the effect of ACTN3 genotype on response to exercise and ageing, and the onset and severity of muscle disease phenotype.
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udp n acetylglucosamine 2 epimerase n acetylmannosamine kinase gne binds to Alpha Actinin 1 novel pathways in skeletal muscle
PLOS ONE, 2008Co-Authors: Shira Amsili, Hagit Zer, Stephan Hinderlich, Sabine Krause, Michal Beckercohen, Daniel G Macarthur, Kathryn N North, Stella MitranirosenbaumAbstract:Hereditary inclusion body myopathy (HIBM) is a rare neuromuscular disorder caused by mutations in GNE, the key enzyme in the biosynthetic pathway of sialic acid. While the mechanism leading from GNE mutations to the HIBM phenotype is not yet understood, we searched for proteins potentially interacting with GNE, which could give some insights about novel putative biological functions of GNE in muscle. We used a Surface Plasmon Resonance (SPR)-Biosensor based assay to search for potential GNE interactors in anion exchanged fractions of human skeletal muscle primary culture cell lysate. Analysis of the positive fractions by in vitro binding assay revealed Alpha-Actinin 1 as a potential interactor of GNE. The direct interaction of the two proteins was assessed in vitro by SPR-Biosensor based kinetics analysis and in a cellular environment by a co-immunoprecipitation assay in GNE overexpressing 293T cells. Furthermore, immunohistochemistry on stretched mouse muscle suggest that both GNE and Alpha-Actinin 1 localize to an overlapping but not identical region of the myofibrillar apparatus centered on the Z line. The interaction of GNE with Alpha-Actinin 1 might point to its involvement in Alpha-Actinin mediated processes. In addition these studies illustrate for the first time the expression of the non-muscle form of Alpha-Actinin, Alpha-Actinin 1, in mature skeletal muscle tissue, opening novel avenues for its specific function in the sarcomere. Although no significant difference could be detected in the binding kinetics of Alpha-Actinin 1 with either wild type or mutant GNE in our SPR biosensor based analysis, further investigation is needed to determine whether and how the interaction of GNE with Alpha-Actinin 1 in skeletal muscle is relevant to the putative muscle-specific function of Alpha-Actinin 1, and to the muscle-restricted pathology of HIBM.
Margaret J. Wheelock - One of the best experts on this subject based on the ideXlab platform.
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characterization of the interactions of Alpha catenin with Alpha Actinin and beta catenin plakoglobin
Journal of Cell Science, 1997Co-Authors: J E Nieset, Amy Redfield L Redfield, K A Knudsen, K R Johnson, Fang Jin, Margaret J. WheelockAbstract:Cadherins are calcium-dependent, cell surface glycoproteins involved in cell-cell adhesion. To function in cell-cell adhesion, the transmembrane cadherin molecule must be associated with the cytoskeleton via cytoplasmic proteins known as catenins. Three catenins, Alpha-catenin, beta-catenin and gamma-catenin (also known as plakoglobin), have been identified. beta-catenin or plakoglobin is associated directly with the cadherin; Alpha-catenin binds to beta-catenin/plakoglobin and serves to link the cadherin/catenin complex to the actin cytoskeleton. The domains on the cadherin and betacatenin/plakoglobin that are responsible for protein-protein interactions have been mapped. However, little is known about the molecular interactions between Alpha-catenin and beta-catenin/plakoglobin or about the interactions between Alpha-catenin and the cytoskeleton. In this study we have used the yeast two-hybrid system to map the domains on Alpha-catenin that allow it to associate with beta-catenin/plakoglobin and with Alpha-Actinin. We also identify a region on Alpha-Actinin that is responsible for its interaction with Alpha-catenin. The yeast two-hybrid data were confirmed with biochemical studies.
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interaction of Alpha Actinin with the cadherin catenin cell cell adhesion complex via Alpha catenin
Journal of Cell Biology, 1995Co-Authors: K A Knudsen, Alejandro Peralta Soler, K R Johnson, Margaret J. WheelockAbstract:Cadherins are Ca(2+)-dependent, cell surface glycoproteins involved in cell-cell adhesion. Extracellularly, transmembrane cadherins such as E-, P-, and N-cadherin self-associate, while intracellularly they interact indirectly with the actin-based cytoskeleton. Several intracellular proteins termed catenins, including Alpha-catenin, beta-catenin, and plakoglobin, are tightly associated with these cadherins and serve to link them to the cytoskeleton. Here, we present evidence that in fibroblasts Alpha-Actinin, but not vinculin, colocalizes extensively with the N-cadherin/catenin complex. This is in contrast to epithelial cells where both cytoskeletal proteins colocalize extensively with E-cadherin and catenins. We further show that Alpha-Actinin, but not vinculin, coimmunoprecipitates specifically with Alpha- and beta-catenin from N- and E-cadherin-expressing cells, but only if Alpha-catenin is present. Moreover, we show that Alpha-Actinin coimmunoprecipitates with the N-cadherin/catenin complex in an actin-independent manner. We therefore propose that cadherin/catenin complexes are linked to the actin cytoskeleton via a direct association between Alpha-Actinin and Alpha-catenin.
Tadaomi Takenawa - One of the best experts on this subject based on the ideXlab platform.
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Alpha Actinin and vinculin are pip2 binding proteins involved in signaling by tyrosine kinase
Journal of Biological Chemistry, 1994Co-Authors: Kiyoko Fukami, Takeshi Endo, M Imamura, Tadaomi TakenawaAbstract:Western blot analysis of Balb/c 3T3 cell lysates by an antibody specific to phosphatidylinositol 4,5-bisphosphate (PIP2) showed that several proteins exist in a PIP2-bound form. Among them, two proteins, 100 and 115 kDa in molecular mass, were detected as PIP2 abundant proteins. These were identified as Alpha-Actinin and vinculin by their antibodies. In Balb/c 3T3 cells, Alpha-Actinin in the cytoskeleton contains PIP2, while Alpha-Actinin in cytosol does not. The levels of PIP2 bound to Alpha-Actinin decrease in response to platelet-derived growth factor (PDGF). Similarly, PIP2 bound to vinculin is decreased upon stimulation with PDGF. By immunofluorescent staining, PIP2 was found to be present densely in the central areas around nuclei, microfilament bundles, and focal contacts, where Alpha-Actinin and vinculin are distributed. PDGF stimulation decreases the intensity of PIP2 staining in these areas. In this paper we suggest that tyrosine kinase-activated phospholipase C hydrolyzes PIP2 bound to Alpha-Actinin and vinculin, leading to the simultaneous generation of second messengers and reorganization of the cytoskeleton.
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Requirement of phosphatidylinositol 4,5-bisphosphate for Alpha-Actinin function.
Nature, 1992Co-Authors: Kiyoko Fukami, Takeshi Endo, Kiyoshi Furuhashi, Masaki Inagaki, Sadashi Hatano, Tadaomi TakenawaAbstract:Inositol phospholipid turnover is enhanced during mitogenic stimulation of cells by growth factors and the breakdown of phosphatidylinositol 4,5-bisphosphate (PtdInsP2) may be important in triggering cell proliferation. PtdInsP2 also binds actin-binding proteins to regulate their activity, but it is not yet understood how this control is achieved. The protein Alpha-Actinin from striated muscle contains large amounts of endogenous PtdInsP2, whereas that from smooth muscle has only a little but will bind exogenously added PtdInsP2. In vitro Alpha-Actinin binds to F-actin and will crosslink actin filaments, increasing the viscosity of F-actin solutions. We report here that Alpha-Actinin from striated muscle is an endogenous PtdInsP2-bound protein and that the specific interaction between Alpha-Actinin and PtdInsP2 regulates the F-actin-gelating activity of Alpha-Actinin. Although the F-actin-gelating activity of Alpha-Actinin from smooth muscle is much reduced compared with that from striated muscle, exogenous PtdInsP2 can enhance the activity of smooth muscle Alpha-Actinin to the level seen in striated muscles. These results show that PtdInsP2 is present in striated muscle Alpha-Actinin and that it is necessary for Alpha-Actinin to realize its maximum gelating activity.
Gunther Gerisch - One of the best experts on this subject based on the ideXlab platform.
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Selection of Dictyostelium mutants defective in cytoskeletal proteins: use of an antibody that binds to the ends of Alpha-Actinin rods.
The EMBO Journal, 2018Co-Authors: E. Wallraff, M. Modersitzki, D. Rieger, Mary Schleicher, Gerald Isenberg, Gunther GerischAbstract:A monoclonal antibody, mAb 47-19-2, was used to study the subunit topology of the rod-shaped Alpha-Actinin molecules of Dictyostelium discoideum and to screen for mutants defective in the production of Alpha-Actinin. Electron microscopy of rotary-shadowed Alpha-Actinin-antibody complexes showed binding of mAb 47-19-2 to both ends of the Alpha-Actinin rods and cleavage of the rods into its subunits, indicating that the two subunits of Alpha-Actinin extend in an anti-parallel mode through the whole length of the rod. The antibody binding sites were located in close proximity to the sites responsible for actin cross-linking, which is consistent with the blocking activity of the antibody. In a mutant, HG1130, no antibody label was detected in colony blots, and by immunoblotting of mutant proteins separated by SDS-PAGE, only trace amounts of Alpha-Actinin were found. The mutant showed normal binding of antibodies directed against the actin-binding proteins severin and capping protein. The mutation responsible for the Alpha-Actinin defect was recessive and located on linkage group I of the genetic map of D. discoideum. HG1130 cells grew on bacteria at a normal rate and also axenically like cells of the parent strain AX2. After starvation the mutant cells expressed the contact site A glycoprotein, a marker of the aggregation-competent stage, and reacted chemotactically to cyclic AMP. The aggregation patterns and fruiting bodies of the mutant appeared to be normal. Patching and capping on the surface of HG1130 cells was induced by antibodies against the contact site A glycoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)
Lee H Sweeney - One of the best experts on this subject based on the ideXlab platform.
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sarcomeric Alpha Actinin defective in vinculin binding causes z line expansion and nemaline like body formation in cultured chick myotubes
Experimental Cell Research, 2009Co-Authors: Zhiqian Zhang, Howard Holtzer, Lawrence T Bish, Lee H SweeneyAbstract:The Z-line in each striated muscle has a precisely defined width that corresponds to muscle fiber type, and it can enlarge several fold in nemaline myopathy. To explore the mechanism(s) underlying Z-line width and structure maintenance, a series of sarcomeric-Alpha-Actinin mutants tagged with myc-epitope was transfected into cultured chick myotubes. By double-staining transfected myotubes with myc and myofibrillar protein antibodies, we found that Alpha-Actinin mutants with deletion of the region from the beginning of the fourth spectrin repeat to the start of the EF-hands resulted in expansion of Z-line width, often displayed a doublet staining pattern, and resulted in formation of nemaline-like bodies in older myotubes under fluorescence microscope. Yeast-two hybridization analysis demonstrated that this region was involved in vinculin binding, and for vinculin to bind Alpha-Actinin, residues 1-116 and 258-323 were required. Hence, we have defined a critical region of s-Alpha-Actinin that affects the width and integrity of the Z-line. This region is at least involved in the interaction with vinculin.