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Calpain-3 is activated following eccentric exercise
Reply to Letter by Dr. Murphy and Dr. Lamb
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Dr. Robyn M. Murphy, Department of Zoology La Trobe University, Australia, Graham D Lamb, PhD
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r.murphy{at}latrobe.edu.au Dr. Robyn M. Murphy, et al.
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In a recent article by Lehti et al (2009) the effect of fatiguing exercise on the mRNA expression of a number of skeletal muscle proteins was examined. In the discussion it was stated that in a study conducted by our laboratory, calpain-3 mRNA was increased 24 h after a bout of eccentric exercise (Murphy et al., 2007). It needs to be pointed out that this was NOT a finding in that manuscript and there were no mRNA measurements made in that study. We in fact measured calpain-3 protein and reported the first physiological activation of calpain-3, which occurred 24 hours after the single bout of eccentric exercise in humans. These findings support a role for calpain-3 in sarcomeric remodeling following eccentric exercise. We used autolysis as a measure of calpain-3 activity because it is known that calpain-3 must be autolysed in order for it to become activated (Garcia Diaz et al., 2004). Recently, we have shown that calpain-3 is activated when in the presence of only ~ 200 nM Ca2+ for one hour, although it was not activated over the same period of time in the presence of ~ 50 nM Ca2+ (Murphy & Lamb, 2009) The finding of no change or as stated “a decreasing trend in calpain-3 mRNA expression was seen” two days after the exercise protocol (Lehti et al., 2009) is similar to that previously reported following eccentric exercise (Feasson et al., 2002). In the latter study, the authors pointed out that mRNA measurements are not necessarily indicative of enzyme activity and protein levels although some correlation between the mRNA and protein levels for m-calpain have been reported (Spencer et al., 1997). There is no evidence for such associations between mRNA, protein levels or protein activity for the skeletal muscle specific calpain-3. The previous findings (Feasson et al., 2002; Murphy et al., 2007; Lehti et al., 2009) might suggest that there is indeed no correlation between calpain-3 mRNA and protein levels and that if knowledge is to be obtained about the functional role of calpain-3 in skeletal muscle then autolysis of the full -length endogenously expressed protein needs to be measured. Feasson L, Stockholm D, Freyssenet D, Richard I, Duguez S, Beckmann JS & Denis C. (2002). Molecular adaptations of neuromuscular disease- associated proteins in response to eccentric exercise in human skeletal muscle. J Physiol 543, 297-306. Garcia Diaz BE, Moldoveanu T, Kuiper MJ, Campbell RL & Davies PL. (2004). Insertion Sequence 1 of Muscle-specific Calpain, p94, Acts as an Internal Propeptide. J Biol Chem 279, 27656-27666. Lehti M, Kivela R, Komi PV, Komulainen J, Kainulainen H & Kyrolainen H. (2009). Effects of fatiguing jumping exercise on mRNA expression of titin-complex proteins and calpains. J Appl Physiol. Jan 15, doi:10.1152/japplphysiol.90660.2008. Murphy RM, Goodman CA, McKenna MJ, Bennie J, Leikis M & Lamb GD. (2007). Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise. J Appl Physiol 103, 926-931. Murphy RM & Lamb GD. (2009). Endogenous calpain-3 activation is primarily governed by small increases in resting cytoplasmic [Ca2+] and is not dependent on stretch. J Biol Chem, In Press 14 January, doi:10.1074/jbc.M808655200 Spencer MJ, Lu B & Tidball JG. (1997). Calpain II expression is increased by changes in mechanical loading of muscle in vivo. J Cell Biochem 64, 55-66. |
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Maarit Lehti, PhD, LIKES Research Center for Sport and Health Sciences Finland, Riikka Kivelä, Paavo Komi, Jyrki Komulainen, Prof. Heikki Kainulainen, Prof. Heikki Kyröläinen
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maarit.lehti{at}likes.fi Maarit Lehti, PhD, et al.
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In their letter to editor Dr. Murphy and Dr. Lamb address erroneous citation of their article (2) in our paper (1) and highlight the importance of posttranscriptional regulation of calpain-3. The remark of Dr. Murphy and Dr. Lamb is justified. As a result of an unfortunate mistake, which occurred at the finishing and shortening phase of the discussion, factual content of text and reference (2) became erroneous. We apologize for the incident. Fortunately, the mistake did not change the essential content of our article (1). References 1. Lehti M, Kivela R, Komi PV, Komulainen J, Kainulainen H & Kyrolainen H. (2009). Effects of fatiguing jumping exercise on mRNA expression of titin-complex proteins and calpains. J Appl Physiol. Jan 15, doi:10.1152/japplphysiol.90660.2008. 2. Murphy RM, Goodman CA, McKenna MJ, Bennie J, Leikis M & Lamb GD. (2007). Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise. J Appl Physiol 103, 926-931. Maarit Lehti1 Riikka Kivelä1,2 Paavo Komi2 Jyrki Komulainen1,2 Heikki Kainulainen1,2 Heikki Kyröläinen2 1LIKES research Center for Sport and Heath Sciences, Rautpohjankatu 8, FIN-40700 Jyväskylä, Finland 2Neuromuscular Research Center, Department of Biology of Physical Activity, P.O: Box 35, FIN-40014 University of Jyväskylä, Finland |
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