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Ca 2+ Overload and Sarcoplasmic Reticulum Instability in tric-a Null Skeletal Muscle *

Journal of Biological Chemistry, ISSN: 0021-9258, Vol: 285, Issue: 48, Page: 37370-37376
2010
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Article Description

The sarcoplasmic reticulum (SR) of skeletal muscle contains K +, Cl −, and H + channels may facilitate charge neutralization during Ca 2+ release. Our recent studies have identified trimeric intracellular cation (TRIC) channels on SR as an essential counter-ion permeability pathway associated with rapid Ca 2+ release from intracellular stores. Skeletal muscle contains TRIC-A and TRIC-B isoforms as predominant and minor components, respectively. Here we test the physiological function of TRIC-A in skeletal muscle. Biochemical assay revealed abundant expression of TRIC-A relative to the skeletal muscle ryanodine receptor with a molar ratio of TRIC-A/ryanodine receptor ∼5:1. Electron microscopy with the tric-a −/− skeletal muscle showed Ca 2+ overload inside the SR with frequent formation of Ca 2+ deposits compared with the wild type muscle. This elevated SR Ca 2+ pool in the tric-a −/− muscle could be released by caffeine, whereas the elemental Ca 2+ release events, e.g. osmotic stress-induced Ca 2+ spark activities, were significantly reduced likely reflecting compromised counter-ion movement across the SR. Ex vivo physiological test identified the appearance of “alternan” behavior with isolated tric-a −/− skeletal muscle, i.e. transient and drastic increase in contractile force appeared within the decreasing force profile during repetitive fatigue stimulation. Inhibition of SR/endoplasmic reticulum Ca 2+ ATPase function could lead to aggravation of the stress-induced alternans in the tric-a −/− muscle. Our data suggests that absence of TRIC-A may lead to Ca 2+ overload in SR, which in combination with the reduced counter-ion movement may lead to instability of Ca 2+ movement across the SR membrane. The observed alternan behavior with the tric-a −/− muscle may reflect a skeletal muscle version of store overload-induced Ca 2+ release that has been reported in the cardiac muscle under stress conditions.

Bibliographic Details

Zhao, Xiaoli; Yamazaki, Daiju; Park, Ki Ho; Komazaki, Shinji; Tjondrokoesoemo, Andoria; Nishi, Miyuki; Lin, Peihui; Hirata, Yutaka; Brotto, Marco; Takeshima, Hiroshi; Ma, Jianjie

American Society for Biochemistry & Molecular Biology (ASBMB)

Biochemistry, Genetics and Molecular Biology

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