Evidence for gamma-actin as a Z disc component in skeletal myofibers.
We investigated the targeting of the gamma-actin isoform in skeletal myofibers. For this purpose we used expression vectors to produce green fluorescent protein (GFP-) as well as myc-tagged gamma-actin in rat flexor digitorum brevis myofibers. We found that the gamma-actin fusion proteins accumulated into Z discs but not beneath the sarcolemma. Instead, the GFP-tagged skeletal muscle-specific alpha-actin isoform was preferentially incorporated into the pointed ends of thin contractile filaments. The localization pattern of the gamma-actin fusion proteins was completely different from that of the dystrophin glycoprotein complex on the sarcolemma. The results emphasize the role of gamma-actin as a Z disc component but fail to reveal an actin-based sub-sarcolemmal cytoskeleton in skeletal muscle cells.
Papponen
Hinni
H
Institute of Biomedicine, Department of Anatomy and Cell Biology, P.O. Box 5000 (Aapistie 7), FIN-90014 University of Oulu, Finland.
Kaisto
Tuula
T
Leinonen
Sanna
S
Kaakinen
Mika
M
Metsikkö
Kalervo
K
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D049030:Dystroglycans / Q000378:metabolism; D005260:Female; D036681:Fluorescence Recovery After Photobleaching; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism*; D010590:Phalloidine / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism*; D014161:Transduction, Genetic
D000199:Actins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D049030:Dystroglycans; D010590:Phalloidine