Comparative decline of the protein profiles of nebulin in response to denervation in skeletal muscle.
The sliding filament model of the sarcomere was developed more than half a century ago. This model, consisting only of thin and thick filaments, has been efficacious in elucidating many, but not all, features of skeletal muscle. Work during the 1980s revealed the existence of two additional filaments: the giant filamentous proteins titin and nebulin. Nebulin, a giant myofibrillar protein, acts as a protein ruler to maintain the lattice arrays of thin filaments and plays a role in signal transduction and contractile regulation. However, the change of nebulin and its effect on thin filaments in denervation-induced atrophic muscle remains unclear. The purpose of this study is to examine the content and pattern of nebulin, myosin heavy chain (MHC), actin, and titin in innervated and denervated tibialis anterior (TA) muscles of rats using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), densitometry and electron microscopic (EM) analyses. The results revealed that denervation induced muscle atrophy is accompanied by decreased nebulin content in a time-dependent manner. For instant, the levels of nebulin in denervated muscles were markedly (P < 0.05) decreased, about 24.6% and 40.2% in comparison with innervated muscle after denervation of 28 and 56 days, respectively. The nebulin/MHC, nebulin/actin, and nebulin/titin ratios were decreased, suggesting a concomitant reduction of nebulin in denervated muscle. Moreover, a western blotting assay proved that nebulin declined faster than titin on 28 and 56 days of denervated muscle. In addition, EM study revealed that the disturbed arrangements of myofilaments and a disorganized contractile apparatus were also observed in denervated muscle. Overall, the present study provides evidence that nebulin is more sensitive to the effect of denervation than MHC, actin, and titin. Nebulin decline indeed resulted in disintegrate of thin filaments and shortening of sarcomeres.
Department of Internal Medicine, Min-Sheng General Hospital, Taoyuan, Taiwan.
Jih-Hua
JH
Wei
Division of Cardiology, Department of Internal Medicine, College of Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
Nen-Chung
NC
Chang
Department of Nursing, Chang Gung University of Science and Technology, Taoyuan, Taiwan.
Sy-Ping
SP
Chen
Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India.
Pitchairaj
P
Geraldine
Department of Pharmacology and Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: tjaya_2002@yahoo.co.in.
Thanasekaran
T
Jayakumar
Department of Anatomy and Cell Biology, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: thfong@tmu.edu.tw.
Tsorng-Harn
TH
Fong
D000199:Actins / Q000032:analysis / Q000378:metabolism; D000818:Animals; D064211:Connectin / Q000032:analysis / Q000378:metabolism; D005355:Fibrosis; D008297:Male; D009121:Muscle Denervation / Q000009:adverse effects; D009124:Muscle Proteins / Q000032:analysis / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism* / Q000473:pathology; D009133:Muscular Atrophy / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D009210:Myofibrils / Q000378:metabolism / Q000473:pathology; D018995:Myosin Heavy Chains / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012518:Sarcomeres / Q000378:metabolism / Q000473:pathology
D000199:Actins; D064211:Connectin; D009124:Muscle Proteins; C035620:nebulin; D018995:Myosin Heavy Chains
Denervation; Electron microscopy; Muscle atrophy; Myofibrillar protein; Nebulin