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Tau expression in denervated rat muscles
Author(s) -
Nagao ShinIchiro,
Kumamoto Toshihide,
Masuda Tomoko,
Ueyama Hidetsugu,
Toyoshima Itaru,
Tsuda Tomiyasu
Publication year - 1999
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(199901)22:1<61::aid-mus10>3.0.co;2-y
Subject(s) - denervation , vacuole , atrophy , sarcoplasm , autophagy , medicine , endocrinology , muscle atrophy , soleus muscle , myocyte , biology , chemistry , skeletal muscle , microbiology and biotechnology , biochemistry , endoplasmic reticulum , apoptosis , cytoplasm
We studied whether denervation affects the expression of tau, in particular phosphorylated tau, and how it is degraded in rat soleus muscles. Immunoblot analysis showed a high molecular weight, approximately 110 kDa (big tau), in normal muscle. Tau levels increased significantly in denervated muscles treated with chloroquine (a lysosomotrophic agent) and in untreated ones, as compared to levels of similarly treated contralateral, innervated muscles. Most of the tau in the innervated and denervated muscles was phosphorylated. Immunohistochemically, tau and β‐tubulin colocated in the sarcoplasm of innervated, saline‐treated (intact) muscle, but the staining intensities were very weak. Both proteins, however, were expressed extensively in these areas in the denervated muscles from saline‐treated rats. In the denervated muscle of chloroquine‐treated rats there were numerous autophagic vacuoles in the sarcoplasm, and phosphorylated‐tau accumulation was marked within these vacuoles, indicative that tau first was taken into autophagic, vacuoles by nonselective autophagy then degraded via the lysosomal as well as the nonlysosomal calpain system. Our findings suggest that phosphorylated big tau accumulates with β‐tubulin in denervated muscular atrophy, possibly in order to maintain or preserve the integrity of the muscle fiber during progressive atrophy or regeneration. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 61–70, 1999