Desmin filaments influence myofilament spacing and lateral compliance of slow skeletal muscle fibres
Johanna Balogh 1, Zhenlin Li 2, Denise Paulin 2 and Anders Arner 3*
1 Physiological Sciences, Lund Univ
2 University Paris VII, France
3 Physiological Sciences, Lund Univ and Physiology and Pharmacology, Karolinska Institute, Stockholm
* To whom correspondence should be addressed. E-mail: anders.arner{at}mphy.lu.se.
Submitted on March 19, 2004
Revised on April 30, 2004
Accepted on 29 October 2004
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Abstract |
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Intermediate filaments composed of desmin, interlink Z-disks and sarcolemma in skeletal muscle. Depletion of desmin results in lower active stress of smooth, cardiac and skeletal muscles. Structural functions of intermediate filaments in fast (psoas) and slow (soleus) skeletal muscle were examined using X-ray diffraction on permeabilized muscle from desmin deficient mice (Des-/-) and controls (Des+/+). To examine lateral compliance of sarcomeres and cells, filament distances and fibre width were measured during osmotic compression with dextran. Equatorial spacing (X-ray diffraction) of contractile filaments was wider in soleus Des-/- muscle compared to Des+/+, showing that desmin is important for maintaining lattice structure. Osmotic lattice compression was similar in Des-/- and Des+/+. In width measurements of single fibres and bundles, Des-/- soleus were more compressed by dextran compared to Des+/+, showing that intermediate filaments contribute to whole cell compliance. For psoas fibres, both filament distance and cell compliance were similar in Des-/- and Des+/+. We conclude that desmin is important for stabilising sarcomeres and maintaining cell compliance in slow skeletal muscle. Wider filament spacing in Des-/- soleus can however not explain the lower active stress, but might influence resistance to stretch, possibly minimising stretch-induced cell injury.
Key Words:
Desmin, intermediate filaments, skeletal muscle, soleus, transgenic mouse, x-ray diffraction
