ISSN:
1432-2013
Keywords:
Calcium adenosinetriphosphatase Calsequestrin Dihydropyridine receptor Excitation–contraction coupling Fast-to-slow muscle transition Myosin heavy chain isoforms Ryanodine receptor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract. Since chronic low-frequency stimulation of fast-twitch muscle fibers has a profound effect on all major functional elements of skeletal muscle, we analyzed the potential changes in the levels of Ca2+-regulatory membrane proteins during fast-to-slow transformation. In this study we show that, in addition to isoform-switching in myosin heavy chains, electrostimulation triggers a decline in fast isoforms and an increase in slow/cardiac isoforms of Ca2+-ATPase and calsequestrin. The levels of excitation–contraction coupling elements, such as the ryanodine receptor, the dihydropyridine receptor, triadin and sarcalumenin, decreased sharply following stimulation. In contrast, levels of Na+/K+-ATPase and calreticulin increased in the microsomal fraction. Crosslinking studies have revealed that in normal and stimulated muscle the Ca2+-ATPase isoforms exist predominantly as oligomeric structures, and that the central elements of excitation–contraction coupling also form large triad complexes. Changes in the levels and pattern of isoform expression of the muscle membrane proteins studied here suggest that these biochemical alterations reflect molecular adaptations to changed demands in ion homeostasis and signal transduction in muscle that exhibits enhanced contractile activity. Overall, these findings support the physiological concept that there are muscle fiber-type specific differences in the fine-tuning of the excitation–contraction–relaxation cycle, as well as the idea that mature skeletal muscle fibers exhibit a high degree of plasticity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004249900115
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