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, doi: 10.1152/ajpcell.00291.2005.

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Title µ- Calpain and calpain-3 are not autolyzed with exhaustive exercise in humans
Author(s) Murphy, Robyn M.
Snow, RodORCID iD for Snow, Rod orcid.org/0000-0002-4796-6916
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
Keyword(s) Ca2+
dependent proteases
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
DOI 10.1152/ajpcell.00291.2005
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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