µ- Calpain and calpain-3 are not autolyzed with exhaustive exercise in humans

Murphy, Robyn M., Snow, Rod and Lamb, Graham D. 2006, µ- Calpain and calpain-3 are not autolyzed with exhaustive exercise in humans, American journal of physiology : cell physiology, vol. 290, no. 1, pp. C116-c122.

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Title µ- Calpain and calpain-3 are not autolyzed with exhaustive exercise in humans
Author(s) Murphy, Robyn M.
Snow, Rod
Lamb, Graham D.
Journal name American journal of physiology : cell physiology
Volume number 290
Issue number 1
Start page C116
End page c122
Publisher American Physiology Society
Place of publication Bethesda, Md.
Publication date 2006-01
ISSN 0363-6143
1522-1563
Keyword(s) Ca2+
dependent proteases
proteolysis
Summary µ-calpain and calpain-3 are Ca2+-dependent proteases found in skeletal muscle. Autolysis of calpains is observed using Western blot analysis as the cleaving of the full-length proteins to shorter products. Biochemical assays suggest that µ-calpain becomes proteolytically active in the presence of 2–200 µM Ca2+. Although calpain-3 is poorly understood, autolysis is thought to result in its activation, which is widely thought to occur at lower intracellular Ca2+ concentration levels ([Ca2+]i; ~1 µM) than the levels at which µ-calpain activation occurs. We have demonstrated the Ca2+-dependent autolysis of the calpains in human muscle samples and rat extensor digitorum longus (EDL) muscles homogenized in solutions mimicking the intracellular environment at various [Ca2+] levels (0, 2.5, 10, and 25 µM). Autolysis of calpain-3 was found to occur across a [Ca2+] range similar to that for µ-calpain, and both calpains displayed a seemingly higher Ca2+ sensitivity in human than in rat muscle homogenates, with ~15% autolysis observed after 1-min exposure to 2.5 µM Ca2+ in human muscle and almost none after 1- to 2-min exposure to the same [Ca2+]i level in rat muscle. During muscle activity, [Ca2+]i may transiently peak in the range found to autolyze µ-calpain and calpain-3, so we examined the effect of two types of exhaustive cycling exercise (30-s "all-out" cycling, n = 8; and 70% VO2 peak until fatigue, n = 3) on the amount of autolyzed µ-calpain or calpain-3 in human muscle. No significant autolysis of µ-calpain or calpain-3 occurred as a result of the exercise. These findings have shown that the time- and concentration-dependent changes in [Ca2+]i that occurred during concentric exercise fall near but below the level necessary to cause autolysis of calpains in vivo.
Language eng
Field of Research 060199 Biochemistry and Cell Biology not elsewhere classified
HERDC Research category C1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2006, American Physiological Society
Persistent URL http://hdl.handle.net/10536/DRO/DU:30008961

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