Spontaneous and voltage-activated Ca2+ release in adult mouse skeletal muscle fibres expressing the type3 ryanodine receptor
Spontaneous and voltage-activated Ca2+ release in adult mouse skeletal muscle fibres expressing the type3 ryanodine receptor
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DOI：
10.1113/jphysiol.2007.145862
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发表时间：
2008-01-15
影响因子：
5.5
通讯作者：
Jacquemond, Vincent
中科院分区：
文献类型：
--
作者：
Legrand, Claude;Giacomello, Erniliana;Jacquemond, Vincent
3型ryanodine受体（RyR3）是一种在多种细胞类型中表达的钙释放通道，其生理特性和作用仍然是一个谜。在体内，我们使用GFP-RyR3 DNA构建体强迫RyR3在成年小鼠骨骼肌纤维中的表达。GFP荧光在肌纤维的空间限制区域内发现，在那里它表现出与肌节相关的带状模式，与接合肌浆网膜内或附近的定位一致。免疫染色证实在gfp阳性区域存在RyR3和RyR1。在与钙指示剂fluo-3微注射的90%的ryr3阳性纤维中，我们检测到细胞内Ca2+的重复自发瞬态升高，当纤维被固定在-80 mV电压时，这种升高持续存在。这些Ca2+瞬态基本上局限于RyR3表达区。它们的范围从广泛的局部事件到传播Ca2+波，在某些情况下与局部收缩活动有关。当在ryr3表达区测量fluo-3或rhod-2荧光时施加电压钳去极化时，没有检测到电压诱发的“火花样”基本Ca2+释放事件。然而，在ryr3表达区域内，全局电压激活的Ca2+释放表现出一个突出的早期峰值。表达GFP-RyR1结构的肌肉纤维也进行了测量；阳性纤维也产生了局部带状模式的GFP荧光，但表现出自发Ca2+释放。结果表明，RyR3是电压无关的Ca2+释放活性的一个非常有效的来源。相反，我们没有发现证据表明它可以促进分化哺乳动物骨骼肌中离散电压激活的Ca2+释放事件的产生。
The physiological properties and role of the type 3 ryanodine receptor (RyR3), a calcium release channel expressed in a wide variety of cell types, remain mysterious. We forced, in vivo, the expression of RyR3 in adult mouse skeletal muscle fibres using a GFP-RyR3 DNA construct. GFP fluorescence was found within spatially restricted regions of muscle fibres where it exhibited a sarcomere-related banded pattern consistent with a localization within or near the junctional sarcoplasmic reticulum membrane. Inummostaining confirmed the presence of RyR3 together with RyR1 within the GFP-positive areas. In similar to 90% of RyR3-positive fibres microinjected with the calcium indicator fluo-3, we detected repetitive spontaneous transient elevations of intracellular Ca2+ that persisted when fibres were voltage-clamped at -80 mV. These Ca2+ transients remained essentially confined to the RyR3 expression region. They ranged from wide local events to propagating Ca2+ waves and were in some cases associated with local contractile activity. When voltage-clamp depolarizations were applied while fluo-3 or rhod-2 fluorescence was measured within the RyR3-expressing region, no voltage-evoked 'spark-like' elementary Ca2+ release event could be detected. Still global voltage-activated Ca2+ release exhibited a prominent early peak within the RyR3-expressing regions. Measurements were also taken from muscles fibres expressing a GFP-RyR1 construct; positive fibres also yielded a local banded pattern of GFP fluorescence but exhibited no spontaneous Ca2+ release. Results demonstrate that RyR3 is a very potent source of voltage-independent Ca2+ release activity. Conversely we find no evidence that it could contribute to the production of discrete voltage-activated Ca2+ release events in differentiated mammalian skeletal muscle.