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The importance of subfragment 2 and C ‐terminus of myosin heavy chain for thick filament assembly in skeletal muscle cells
Author(s) -
Ojima Koichi,
Oe Mika,
Nakajima Ikuyo,
Shibata Masahiro,
Muroya Susumu,
Chikuni Koichi,
Hattori Akihito,
Nishimura Takanori
Publication year - 2015
Publication title -
animal science journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.606
H-Index - 38
eISSN - 1740-0929
pISSN - 1344-3941
DOI - 10.1111/asj.12310
Subject(s) - myosin , heavy meromyosin , myofibril , protein filament , sarcomere , myosin head , biophysics , actin , chemistry , meromyosin , skeletal muscle , microbiology and biotechnology , anatomy , biology , biochemistry , myosin light chain kinase , myocyte
In skeletal muscle cells, myofibrillar proteins are highly organized into sarcomeres in which thick filaments interdigitate with thin filaments to generate contractile force. The size of thick filaments, which consist mainly of myosin molecules, is strictly controlled. However, little is known about the mechanisms by which myosin molecules assemble into thick filaments. Here, we assessed the ability of each domain of myosin heavy chain (Myh) to form thick filaments. We showed that exogenously expressed subfragment 2 ( S2 ) + light meromyosin ( LMM ) of Myh was efficiently incorporated into thick filaments in muscle cells, although neither solely expressed S2 nor LMM targeted to thick filaments properly. In nonmuscle COS7 cells, S2 + LMM formed more enlarged filaments/speckles than LMM . These results suggest that Myh filament formation is induced by S2 accompanying LMM . We further examined the effects of Myh C ‐terminus on thick filament assembly. C ‐terminal deletion mutants were incorporated not into entire thick filaments but rather into restricted regions of thick filaments. Our findings suggest that the elongation of myosin filaments to form thick filaments is regulated by S2 as well as C ‐terminus of LMM .