Myosin substitution rate is affected by the amount of cytosolic myosin in cultured muscle cells

Koichi Ojima, Emi Ichimura, Yuya Yasukawa, Mika Oe, Susumu Muroya, Takahiro Suzuki, Jun Ichi Wakamatsu, Takanori Nishimura

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4 Citations (Scopus)


In striated muscles, approximately 300 myosin molecules form a single thick filament in myofibrils. Each myosin is continuously displaced by another myosin to maintain the thick filament structure. Our previous study using a fluorescence recovery after photobleaching (FRAP) technique showed that the myosin replacement rate is decreased by inhibition of protein synthesis, but myosin is still exchangeable. This result prompted us to examine whether myosin in the cytoplasm is involved in myosin replacement in myofibrils. To address this, FRAP was measured in green fluorescent protein (GFP)-tagged myosin heavy chain 3 (Myh3) expressing myotubes that were treated with streptolysin-O (SLO), which forms pores specifically in the plasma membrane to induce leakage of cytoplasmic proteins. Our biochemical data demonstrated that the cytoplasmic myosin content was reduced in SLO-permeabilized semi-intact myotubes. Furthermore, FRAP experiments showed a sluggish substitution rate of GFP-Myh3 in SLO-permeabilized myotubes. Taken together, these results demonstrate that the myosin substitution rate is significantly reduced by a decreased amount of myosin in the cytoplasm and that cytoplasmic myosin contributes to myosin replacement in myofibrils.

Original languageEnglish
Pages (from-to)1788-1793
Number of pages6
JournalAnimal Science Journal
Issue number11
Publication statusPublished - Nov 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences(all)


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