Improved skeletal muscle Ca2+ regulation in vivo following contractions in mice overexpressing PGC-1α
Improved skeletal muscle Ca2+ regulation in vivo following contractions in mice overexpressing PGC-1α
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DOI：
10.1152/ajpregu.00032.2017
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发表时间：
2017-06-01
影响因子：
2.8
通讯作者：
Kano, Yutaka
中科院分区：
文献类型：
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作者：
Eshima, Hiroaki;Miura, Shinji;Kano, Yutaka
在骨骼肌中，静息细胞内 Ca2+ 浓度 ([Ca2+]i) 稳态受到跨肌膜、线粒体和肌浆网 (SR) 膜的 Ca2+ 转运的精细调节。在这三个系统中，线粒体在[Ca2+]i 调节中的相对重要性在体内骨骼肌中仍然知之甚少。我们测试了这样的假设：线粒体吸收 Ca2+ 的能力是决定肌肉静息和收缩后 [Ca2+]i 调节的主要因素。将麻醉的过氧化物酶体增殖物激活受体-γ共激活剂-1 α (PGC-1 α) 过表达（OE，增加线粒体模型）和野生型 (WT) 同窝小鼠的胫骨前肌在体内取出，并加载荧光探针 fura 2-AM 和 Rhod 2-AM Ca2+ 缓冲和线粒体 [Ca2+] 在休息和疲劳强直恢复期间进行评估电刺激引起的收缩（120 秒，100 Hz）。此外，还检查了静息状态下药理学抑制 SR（毒胡萝卜素）和线粒体 [羰基氰化物-4-（三氟甲氧基）苯腙 (FCCP)] 功能的影响。 WT 中的 [ Ca2+] i 在整个收缩后恢复期间保持升高（450 秒时 +6 +/- 1%），但在 PGC-1 α OE 中 [ Ca2+] i 在 150 秒内恢复到静息基线。在 WT 中，毒胡萝卜素立即显着增加静息 [Ca2+]i，而在 PGC-1 α OE 中，这种效应被延迟并显着减弱（WT，+12 +/- 3；PGC-1 α OE，毒胡萝卜素治疗后 600 秒时 + 1 +/- 2%，P < 0.05）。 FCCP 废除了 PGC-1 α OE 中 [ Ca2+] i 调节的这种改进。在收缩和毒胡萝卜素处理后，在 PGC-1 α OE 中观察到线粒体 [Ca2+] 积累。在 SR 中，PGC-1 α OE 下调 SR Ca2+ ATPase 1（Ca2+ 摄取）和小清蛋白（Ca2+ 缓冲）蛋白水平，而线粒体 Ca2+ 摄取相关蛋白（Mfn1、Mfn2 和线粒体 Ca2+ 单向转运蛋白）上调。这些数据表明，骨骼肌线粒体在疲劳性强直性收缩和休息后体内 [Ca2+]i 调节中发挥着迄今为止未被认识到的作用。
In skeletal muscle, resting intracellular Ca2+ concentration ([ Ca2+]i) homeostasis is exquisitely regulated by Ca2+ transport across the sarcolemmal, mitochondrial, and sarcoplasmic reticulum (SR) membranes. Of these three systems, the relative importance of the mitochondria in [ Ca2+] i regulation remains poorly understood in in vivo skeletal muscle. We tested the hypothesis that the capacity for Ca2+ uptake by mitochondria is a primary factor in determining [ Ca2+] i regulation in muscle at rest and following contractions. Tibialis anterior muscle of anesthetized peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1 alpha)-overexpressing (OE, increased mitochondria model) and wild-type (WT) littermate mice was exteriorized in vivo and loaded with the fluorescent probe fura 2-AM, and Rhod 2-AM Ca2+ buffering and mitochondrial [ Ca2+] were evaluated at rest and during recovery from fatiguing tetanic contractions induced by electrical stimulation (120 s, 100 Hz). In addition, the effects of pharmacological inhibition of SR (thapsigargin) and mitochondrial [ carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP)] function were examined at rest. [ Ca2+] i in WT remained elevated for the entire postcontraction recovery period (+6 +/- 1% at 450 s), but in PGC-1 alpha OE [ Ca2+] i returned to resting baseline within 150 s. Thapsigargin immediately and substantially increased resting [ Ca2+] i in WT, whereas in PGC-1 alpha OE this effect was delayed and markedly diminished (WT, +12 +/- 3; PGC-1 alpha OE, + 1 +/- 2% at 600 s after thapsigargin treatment, P < 0.05). FCCP abolished this improvement of [ Ca2+] i regulation in PGC-1 alpha OE. Mitochondrial [ Ca2+] accumulation was observed in PGC-1 alpha OE following contractions and thapsigargin treatment. In the SR, PGC-1 alpha OE downregulated SR Ca2+ ATPase 1 (Ca2+ uptake) and parvalbumin (Ca2+ buffering) protein levels, whereas mitochondrial Ca2+ uptake-related proteins (Mfn1, Mfn2, and mitochondrial Ca2+ uniporter) were upregulated. These data demonstrate a heretofore unappreciated role for skeletal muscle mitochondria in [ Ca2+] i regulation in vivo following fatiguing tetanic contractions and at rest.