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Membrane skeleton of innervated and denervated fast‐ and slow‐twitch muscle
Author(s) -
Williams McRae W.,
Resneck Wendy G.,
Bloch Robert J.
Publication year - 2000
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(200004)23:4<590::aid-mus19>3.0.co;2-z
Subject(s) - sarcolemma , spectrin , dystrophin , denervation , extensor digitorum longus muscle , soleus muscle , biology , endocrinology , medicine , skeletal muscle , anatomy , microbiology and biotechnology , chemistry , biochemistry , cytoskeleton , cell
Abstract We used confocal microscopy and immunoblotting to study membrane skeletal proteins of fast‐twitch (extensor digitorum longus) and slow‐twitch (soleus) muscles of the adult rat. In the extensor digitorum longus (EDL), β‐spectrin concentrates in costameres, whereas dystrophin is enriched at costameres but is also present in intercostameric regions. In the soleus, β‐spectrin and dystrophin underlie much of the sarcolemma, and intercostameric regions are difficult to detect. The EDL sarcolemma reorganizes following denervation to resemble soleus sarcolemma, but denervation does not significantly affect the latter. Consistent with these observations, soleus contains similar amounts of dystrophin but more β‐spectrin than EDL. Denervation increases β‐spectrin levels only in the EDL and dystrophin levels in both muscles. Denervation does not affect β‐fodrin, a β‐spectrin homolog expressed in embryonic myofibers. Thus, neuromuscular activity controls sarcolemmal organization and the levels of β‐spectrin and dystrophin, but not postnatal downregulation of β‐fodrin. The differences in organization of the sarcolemma may underlie the differential susceptibility of fast and slow myofibers to dystrophinopathies. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 590–599, 2000.