Localization of the Ca2+‐dependent proteinases and their inhibitor in normal, fasted, and denervated rat skeletal muscle

Toshihide Kumamoto, William C. Kleese, Jinyang Cong, Darrel E. Goll, Paul R. Pierce, Ronald E. Allen

    Research output: Contribution to journalArticlepeer-review

    99 Scopus citations


    Immunofluorescence and immunogold localization studies show that the two Ca2+‐dependent proteinases (μ‐calpain for the micromolar Ca2+‐requiring proteinase and m‐calpain for the millimolar Ca2+‐requiring proteinase) and their protein inhibitor (calpastatin) are located exclusively intracellularly in normal rat soleus muscle. Quantitative immunogold studies indicate that binding of antibodies to both calpains and to calpastatin is approximately two times greater at the Z‐disk of myofibrils than it is at the I‐band or A‐band regions. Mitochondria and nuclei in muscle cells contain both calpains and calpastatin at concentrations approximately one‐tenth and one‐fifth, respectively, of the concentration at the Z‐disk, as estimated by antibody binding. Very little calpain or calpastatin was seen in the cytoplasmic intermyofibrillar spaces, and most of the calpain and calpastatin in muscle cells is associated with intracellular structures. Immunofluorescence results suggest that concentration of m‐calpain but not μ‐calpain or calpastatin is, in some instances, slightly higher near the intracellular surface of the plasma membrane than elsewhere in the muscle cell. Most m‐calpain, however, is distributed throughout the interior of mature rat skeletal muscle cells. Denervation, or fasting and refeeding increases the concentration of the calpains and calpastatin in the muscle cell but does not change their distribution. Some μ‐and m‐calpain and calpastatin is found extracellularly in denervated soleus muscle or soleus muscle from fasting rats, but the extracellular calparns and calpastatin seem to originate from “leakage” of these proteins out of the cell because serum creatine kinase levels are much higher than normal in denervated or fasting rats.

    Original languageEnglish (US)
    Pages (from-to)60-77
    Number of pages18
    JournalAnatomical Record
    Issue number1
    StatePublished - Jan 1992

    ASJC Scopus subject areas

    • Anatomy
    • Agricultural and Biological Sciences (miscellaneous)


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