Journal of Applied Physiology
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J Appl Physiol 99: 2239-2245, 2005. First published August 11, 2005; doi:10.1152/japplphysiol.00543.2005
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Temperature dependence of speed of actin filaments propelled by slow and fast skeletal myosin isoforms

R. Rossi,1 M. Maffei,1 R. Bottinelli,1,2 and M. Canepari1,2

1Department of Experimental Medicine, Human Physiology Unit, University of Pavia; and 2Interuniversity Institute of Myology, Pavia, Italy

Submitted 9 May 2005 ; accepted in final form 1 August 2005

It was shown that the temperature sensitivity of shortening velocity of skeletal muscles is higher at temperatures below physiological (10–25°C) than at temperatures closer to physiological (25–35°C) and is higher in slow than fast muscles. However, because intact muscles invariably express several myosin isoforms, they are not the ideal model to compare the temperature sensitivity of slow and fast myosin isoforms. Moreover, temperature sensitivity of intact muscles and single muscle fibers cannot be unequivocally attributed to a modulation of myosin function itself, as in such specimen myosin works in the structure of the sarcomere together with other myofibrillar proteins. We have used an in vitro motility assay approach in which the impact of temperature on velocity can be studied at a molecular level, as in such assays acto-myosin interaction occurs in the absence of sarcomere structure and of the other myofibrillar proteins. Moreover, the temperature modulation of velocity could be studied in pure myosin isoforms (rat type 1, 2A, and 2B and rabbit type 1 and 2X) that could be extracted from single fibers and in a wide range of temperatures (10–35°C) because isolated myosin is stable up to physiological temperature. The data show that, at the molecular level, the temperature sensitivity is higher at lower (10–25°C) than at higher (25–35°C) temperatures, consistent with experiments on isolated muscles. However, slow myosin isoforms did not show a higher temperature sensitivity than fast isoforms, contrary to what was observed in intact slow and fast muscles.

temperature sensitivity; in vitro motility


Address for reprint requests and other correspondence: M. Canepari, Dept. of Experimental Medicine, Human Physiology unit, Univ. of Pavia, Via Forlanini 6, 27100 Pavia, Italy (e-mail: canepari{at}unipv.it)




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M. Kawai, T. Kido, M. Vogel, R. H. A. Fink, and S. Ishiwata
Temperature change does not affect force between regulated actin filaments and heavy meromyosin in single-molecule experiments
J. Physiol., August 1, 2006; 574(3): 877 - 887.
[Abstract] [Full Text] [PDF]


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