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Calpain II expression is increased by changes in mechanical loading of muscle in vivo
Author(s) -
Spencer Melissa J.,
Lu Brandon,
Tidball James G.
Publication year - 1997
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(199701)64:1<55::aid-jcb9>3.0.co;2-z
Subject(s) - calpain , gene isoform , skeletal muscle , chemistry , calpastatin , endocrinology , in vivo , medicine , messenger rna , microbiology and biotechnology , biology , biochemistry , enzyme , gene
In the present investigation, we have tested the hypothesis that calpain expression or activity in skeletal muscle is influenced by changes in mechanical loading in vivo. Muscle unloading for 10 days produced no change in the concentrations of calpain I, or II, and no change in calpain activation, as assessed by measurements of the proportion of calpain I or II isoforms that exhibited autoproteolytic modifications. However, muscle reloading for 2 days produced a 90% increase in calpain II concentration per unit wet weight of muscle relative to ambulatory controls. Although no change in the activation index for calpain I or II was identified for reloaded muscle, this index is an expression of the proportion of the total mass of each calpain isoform that is autoproteolyzed. Thus, there is also approximately a 90% increase in autolyzed calpain II in muscle experiencing increased loading than in controls. Northern analysis shows that the concentration of mRNA for calpain II is increased in reloaded muscle, but no change in calpain II mRNA concentration in unloaded muscle. In situ reverse transcription polymerase chain reaction was used to confirm that nearly all calpain II mRNA in reloaded muscle is located in muscle fibers, with very little detectable calpain II mRNA in non‐muscle cells present in the tissue. Together, these findings show that increased muscle loading causes a selective increase in the expression of calpain II isoform, thereby indicating that its regulation is independent from other calpain isoforms. J. Cell. Biochem. 64:55–66. © 1997 Wiley‐Liss, Inc.