title: Primary longitudinal adhesion structures: plectin-containing precursors of costameres in differentiating human skeletal muscle cells.
abstract: Plectin is a high molecular mass protein (ca 530 kDa) that binds actin, intermediate filaments, and microtubules. Mutations of the human plectin gene cause epidermolysis bullosa simplex with muscular dystrophy. In mature human skeletal muscle, plectin is localized between neighboring myofibrils and between myofibrils and the sarcolemma, both at the level of Z-discs. In the present study we have analyzed plectin expression patterns with emphasis on its sarcolemmal localization during human skeletal muscle differentiation in vitro. In myoblasts plectin showed a cytoplasmic intermediate filament-like distribution, whereas in myotubes plectin is also found at the level of the sarcolemma. In particular, in early myotubes a specific plectin isoform colocalizes with the costameric proteins vinculin and beta1D integrin in longitudinally orientated structures which increased in number and longitudinal extension upon further maturation. In mature myotubes processes perpendicular to the parallel system of longitudinal structures became apparent. Subsequent to the occurrence of spontaneous myofibrillar contractions, the number of longitudinal streaks decreased, and plectin and other costameric proteins were found in an orderly cross-striated sarcolemmal lattice overlying myofibrillar Z-discs. Our study demonstrates that plectin is preassembled together with vinculin and beta1D integrin into primary longitudinal adhesion structures. After the occurrence of spontaneous contractions, these structures reorient and mature costameres are assembled.
authors.affiliation: Department of Neurology, University of Bonn, 53105 Bonn, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Schröder
authors.forename: Dirk
authors.initials: D
authors.lastname: Pacholsky
authors.forename: Jens
authors.initials: J
authors.lastname: Reimann
authors.forename: Jens
authors.initials: J
authors.lastname: Matten
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wiche
authors.forename: Dieter O
authors.initials: DO
authors.lastname: Fürst
authors.forename: Peter F M
authors.initials: PF
authors.lastname: van der Ven
mesh_terms: D002454:Cell Differentiation; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D051190:Plectin; D020033:Protein Isoforms / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D019012:Integrin beta1; D007381:Intermediate Filament Proteins; D008565:Membrane Proteins; C495332:PLEC protein, human; D051190:Plectin; D020033:Protein Isoforms; C109742:SLMAP protein, human; D016596:Vinculin