In innervated skeletal muscle fibers, dystrophin and β-dystroglycan form rib-like structures (costameres) that appear as predominantly transverse stripes over Z and M lines. Here, we show that the orientation of these stripes becomes longitudinal in denervated muscles and transverse again in denervated electrically stimulated muscles. Skeletal muscle fibers express nonneural (muscle) agrin whose function is not well understood. In this work, a single application of ≥10 nM purified recombinant muscle agrin into denervated muscles preserved the transverse orientation of costameric proteins that is typical for innervated muscles, as did a single application of ≥1 μM neural agrin. At lower concentration, neural agrin induced acetylcholine receptor aggregates, which colocalized with longitudinally oriented β-dystroglycan, dystrophin, utrophin, syntrophin, rapsyn, and β2-laminin in denervated unstimulated fibers and with the same but transversely oriented proteins in innervated or denervated stimulated fibers. The results indicate that costameres are plastic structures whose organization depends on electrical muscle activity and/or muscle agrin.
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25 June 2001
Article|
June 25 2001
Muscle Activity and Muscle Agrin Regulate the Organization of Cytoskeletal Proteins and Attached Acetylcholine Receptor (Achr) Aggregates in Skeletal Muscle Fibers
Gabriela Bezakova,
Gabriela Bezakova
aDepartment of Physiology, University of Oslo, 0317 Oslo, Norway
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Terje Lømo
Terje Lømo
aDepartment of Physiology, University of Oslo, 0317 Oslo, Norway
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Gabriela Bezakova
aDepartment of Physiology, University of Oslo, 0317 Oslo, Norway
Terje Lømo
aDepartment of Physiology, University of Oslo, 0317 Oslo, Norway
Abbreviations used in this paper: AChE, acetylcholine esterase; AChR, acetylcholine receptor; NMJ, neuromuscular junction; SOL, soleus; Rh-BuTx, TRITC-α-bungarotoxin.
Received:
February 27 2001
Revision Requested:
May 11 2001
Accepted:
May 15 2001
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 2001 The Rockefeller University Press
2001
The Rockefeller University Press
J Cell Biol (2001) 153 (7): 1453–1464.
Article history
Received:
February 27 2001
Revision Requested:
May 11 2001
Accepted:
May 15 2001
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Citation
Gabriela Bezakova, Terje Lømo; Muscle Activity and Muscle Agrin Regulate the Organization of Cytoskeletal Proteins and Attached Acetylcholine Receptor (Achr) Aggregates in Skeletal Muscle Fibers. J Cell Biol 25 June 2001; 153 (7): 1453–1464. doi: https://doi.org/10.1083/jcb.153.7.1453
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