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Department of Molecular Cell Biology, Institute of Molecular
Biology, University of Copenhagen, Copenhagen, Denmark; Department of
General Physiology, Univeristy of Ulm, Ulm, Germany; and Institute of
Anatomy, University of Zürich-Irchel, Zürich,
Switzerland
Berchtold, Martin W.,
Heinrich Brinkmeier, and
Markus Müntener.
Calcium Ion in Skeletal Muscle: Its Crucial Role for Muscle
Function, Plasticity, and Disease. Physiol. Rev. 80: 1215-1265, 2000. Mammalian skeletal muscle shows an enormous
variability in its functional features such as rate of force
production, resistance to fatigue, and energy metabolism, with a wide
spectrum from slow aerobic to fast anaerobic physiology. In addition,
skeletal muscle exhibits high plasticity that is based on the potential
of the muscle fibers to undergo changes of their cytoarchitecture and composition of specific muscle protein isoforms. Adaptive changes of
the muscle fibers occur in response to a variety of stimuli such as,
e.g., growth and differentition factors, hormones, nerve signals, or
exercise. Additionally, the muscle fibers are arranged in compartments
that often function as largely independent muscular subunits. All
muscle fibers use Ca 2+ as their main regulatory and
signaling molecule. Therefore, contractile properties of muscle fibers
are dependent on the variable expression of proteins involved in
Ca 2+ signaling and handling. Molecular diversity of the
main proteins in the Ca 2+ signaling apparatus (the calcium
cycle) largely determines the contraction and relaxation properties of
a muscle fiber. The Ca 2+ signaling apparatus includes
1 ) the ryanodine receptor that is the sarcoplasmic reticulum
Ca 2+ release channel, 2 ) the troponin protein
complex that mediates the Ca 2+ effect to the myofibrillar
structures leading to contraction, 3 ) the Ca 2+
pump responsible for Ca 2+ reuptake into the sarcoplasmic
reticulum, and 4 ) calsequestrin, the Ca 2+
storage protein in the sarcoplasmic reticulum. In addition, a multitude
of Ca 2+ -binding proteins is present in muscle tissue
including parvalbumin, calmodulin, S100 proteins, annexins, sorcin,
myosin light chains, -actinin, calcineurin, and calpain. These
Ca 2+ -binding proteins may either exert an important role in
Ca 2+ -triggered muscle contraction under certain conditions
or modulate other muscle activities such as protein metabolism,
differentiation, and growth. Recently, several Ca 2+
signaling and handling molecules have been shown to be altered in
muscle diseases. Functional alterations of Ca 2+ handling
seem to be responsible for the pathophysiological conditions seen in
dystrophinopathies, Brody's disease, and malignant hyperthermia. These
also underline the importance of the affected molecules for correct
muscle performance.