Evidence for γ-actin as a Z disc component in skeletal myofibers

• Published in: Experimental cell research Vol. 315; no. 2; pp. 218 - 225
• Main Authors: Papponen, Hinni, Kaisto, Tuula, Leinonen, Sanna, Kaakinen, Mika, Metsikkö, Kalervo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-01-2009
• Subjects: Actin Cytoskeleton - metabolism; Actins - genetics; Actins - metabolism; Animals; Cell Line; Dystroglycans - metabolism; Dystrophin; Female; Fluorescence Recovery After Photobleaching; GFP-actin; Muscle; Muscle Fibers, Skeletal - cytology; Muscle Fibers, Skeletal - metabolism; Myoblasts, Skeletal - cytology; Myoblasts, Skeletal - metabolism; Myofibrils - metabolism; Phalloidine - metabolism; Protein Isoforms - metabolism; Rats; Rats, Sprague-Dawley; Recombinant Fusion Proteins - metabolism; Sarcolemma; Sarcomeres - metabolism; Transduction, Genetic; Z disc; γ-actin; Sarcolemma; γ-actin; Muscle; GFP-actin; Dystrophin; Z disc
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/j.yexcr.2008.10.021

We investigated the targeting of the γ-actin isoform in skeletal myofibers. For this purpose we used expression vectors to produce green fluorescent protein (GFP-) as well as myc-tagged γ-actin in rat
flexor digitorum brevis myofibers. We found that the γ-actin fusion proteins accumulated into Z discs but not beneath the sarcolemma. Instead, the GFP-tagged skeletal muscle-specific α-actin isoform was preferentially incorporated into the pointed ends of thin contractile filaments. The localization pattern of the γ-actin fusion proteins was completely different from that of the dystrophin glycoprotein complex on the sarcolemma. The results emphasize the role of γ-actin as a Z disc component but fail to reveal an actin-based sub-sarcolemmal cytoskeleton in skeletal muscle cells.