Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle

Balázs Kiss, Eun Jeong Lee, Weikang Ma, Frank W. Li, Paola Tonino, Srboljub M. Mijailovich, Thomas C. Irving, Hendrikus "Henk" Granzier

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Nebulin is a giant sarcomeric protein that spans along the actin filament in skeletal muscle, from the Z-disk to near the thin filament pointed end. Mutations in nebulin cause muscle weakness in nemaline myopathy patients, suggesting that nebulin plays important roles in force generation, yet little is known about nebulin's influence on thin filament structure and function. Here, we used small-angle X-ray diffraction and compared intact muscle deficient in nebulin (using a conditional nebulin-knockout, Neb cKO) with control (Ctrl) muscle. When muscles were activated, the spacing of the actin subunit repeat (27 Å) increased in both genotypes; when converted to thin filament stiffness, the obtained value was 30 pN/nm in Ctrl muscle and 10 pN/nm in Neb cKO muscle; that is, the thin filament was approximately threefold stiffer when nebulin was present. In contrast, the thick filament stiffness was not different between the genotypes. A significantly shorter left-handed (59 Å) thin filament helical pitch was found in passive and contracting Neb cKO muscles, as well as impaired tropomyosin and troponin movement. Additionally, a reduced myosin mass transfer toward the thin filament in contracting Neb cKO muscle was found, suggesting reduced crossbridge interaction. We conclude that nebulin is critically important for physiological force levels, as it greatly stiffens the skeletal muscle thin filament and contributes to thin filament activation and cross-bridge recruitment.

Original languageEnglish (US)
Pages (from-to)10369-10374
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number41
DOIs
StatePublished - Oct 9 2018

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Skeletal Muscle
Muscles
Nemaline Myopathies
Genotype
Tropomyosin
Troponin
nebulin
Muscle Weakness
Myosins
Actin Cytoskeleton
X-Ray Diffraction
Actins
Mutation
Proteins

Keywords

  • Muscle biology
  • Physiology
  • Skeletal myopathy
  • X-ray diffraction

ASJC Scopus subject areas

  • General

Cite this

Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle. / Kiss, Balázs; Lee, Eun Jeong; Ma, Weikang; Li, Frank W.; Tonino, Paola; Mijailovich, Srboljub M.; Irving, Thomas C.; Granzier, Hendrikus "Henk".

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 115, No. 41, 09.10.2018, p. 10369-10374.

Research output: Contribution to journalArticle

Kiss, Balázs ; Lee, Eun Jeong ; Ma, Weikang ; Li, Frank W. ; Tonino, Paola ; Mijailovich, Srboljub M. ; Irving, Thomas C. ; Granzier, Hendrikus "Henk". / Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle. In: Proceedings of the National Academy of Sciences of the United States of America. 2018 ; Vol. 115, No. 41. pp. 10369-10374.
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AU - Tonino, Paola

AU - Mijailovich, Srboljub M.

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AB - Nebulin is a giant sarcomeric protein that spans along the actin filament in skeletal muscle, from the Z-disk to near the thin filament pointed end. Mutations in nebulin cause muscle weakness in nemaline myopathy patients, suggesting that nebulin plays important roles in force generation, yet little is known about nebulin's influence on thin filament structure and function. Here, we used small-angle X-ray diffraction and compared intact muscle deficient in nebulin (using a conditional nebulin-knockout, Neb cKO) with control (Ctrl) muscle. When muscles were activated, the spacing of the actin subunit repeat (27 Å) increased in both genotypes; when converted to thin filament stiffness, the obtained value was 30 pN/nm in Ctrl muscle and 10 pN/nm in Neb cKO muscle; that is, the thin filament was approximately threefold stiffer when nebulin was present. In contrast, the thick filament stiffness was not different between the genotypes. A significantly shorter left-handed (59 Å) thin filament helical pitch was found in passive and contracting Neb cKO muscles, as well as impaired tropomyosin and troponin movement. Additionally, a reduced myosin mass transfer toward the thin filament in contracting Neb cKO muscle was found, suggesting reduced crossbridge interaction. We conclude that nebulin is critically important for physiological force levels, as it greatly stiffens the skeletal muscle thin filament and contributes to thin filament activation and cross-bridge recruitment.

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