雷亚尔1
兰尼定受体
骨骼肌
内质网
化学
生物物理学
细胞生物学
细胞内
环偶氮酸
钙螯合素
生物化学
生物
内分泌学
作者
Luke Pearce,Aldo Meizoso-Huesca,Crystal Seng,Cédric R. Lamboley,Daniel P. Singh,Bradley S. Launikonis
摘要
Store-operated Ca2+ entry (SOCE) is critical to cell function. In skeletal muscle, SOCE has evolved alongside excitation-contraction coupling (EC coupling); as a result, it displays unique properties compared to SOCE in other cells. The plasma membrane of skeletal muscle is mostly internalized as the tubular system, with the tubules meeting the sarcoplasmic reticulum (SR) terminal cisternae, forming junctions where the proteins that regulate EC coupling and SOCE are positioned. In this review, we describe the properties and roles of SOCE based on direct measurements of Ca2+ influx during SR Ca2+ release and leak. SOCE is activated immediately and locally as the [Ca2+ ] of the junctional SR terminal cisternae ([Ca2+ ]jSR ) depletes. [Ca2+ ]jSR changes rapidly and steeply with increasing activity of the SR ryanodine receptor isoform 1 (RyR1). The high fidelity of [Ca2+ ]jSR with RyR1 activity probably depends on the SR Ca2+ -buffer calsequestrin that is located immediately behind RyR1 inside the SR. This arrangement provides in-phase activation and deactivation of SOCE with a large dynamic range, allowing precise grading of SOCE flux. The in-phase activation of SOCE as the SR partially depletes traps Ca2+ in the cytoplasm, preventing net Ca2+ loss. Mild presentation of RyR1 leak can occur under physiological conditions, providing fibre Ca2+ redistribution without changing fibre Ca2+ content. This condition preserves normal contractile function at the same time as increasing basal metabolic rate. However, higher RyR1 leak drives excess cytoplasmic and mitochondrial Ca2+ load, setting a deleterious intracellular environment that compromises the function of the skeletal muscle.
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