Barone V, Bertocchini F, Bottinelli R, Protasi F, Allen P D, Franzini Armstrong C, Reggiani C, Sorrentino V
DIBIT, San Raffaele Scientific Institute, Milan, Italy.
FEBS Lett. 1998 Jan 30;422(2):160-4. doi: 10.1016/s0014-5793(98)00003-9.
Skeletal muscle contraction is triggered by the release of Ca2+ from the sarcoplasmic reticulum through the type 1 ryanodine receptor (RyR1). Recently it has been shown that also the type 3 isoform of ryanodine receptor (RyR3), which is expressed in some mammalian skeletal muscles, may participate in the regulation of skeletal muscle contraction. Here we report the generation and the characterization of double mutant mice carrying a targeted disruption of both the RyR1 and the RyR3 genes (RyR1-/-;RyR3-/-). Skeletal muscles from mice homozygous for both mutations are unable to contract in response to caffeine and to ryanodine. In addition, they show a very poor capability to develop tension when directly activated with micromolar [Ca2+]i after membrane permeabilization which indicates either poor development or degeneration of the myofibrils. This was confirmed by biochemical analysis of contractile proteins. Electron microscopy confirms small size of myofibrils and shows complete absence of feet (RyRs) in the junctional SR.
骨骼肌收缩是由钙离子（Ca2+）从肌浆网通过1型兰尼碱受体（RyR1）释放而触发的。最近研究表明，在一些哺乳动物骨骼肌中表达的3型兰尼碱受体（RyR3）亚型也可能参与骨骼肌收缩的调节。在此，我们报告了携带RyR1和RyR3基因靶向缺失的双突变小鼠（RyR1-/-;RyR3-/-）的产生及特性。两个突变均为纯合子的小鼠的骨骼肌对咖啡因和兰尼碱无收缩反应。此外，在用微摩尔浓度的细胞内钙离子（[Ca2+]i）直接激活使其膜透化后，它们产生张力的能力非常差，这表明肌原纤维发育不良或退化。收缩蛋白的生化分析证实了这一点。电子显微镜检查证实肌原纤维尺寸小，并显示连接肌浆网中完全没有足突（RyRs）。
