Junctophilin 1 and 2 Proteins Interact with the L-type Ca2+ Channel Dihydropyridine Receptors (DHPRs) in Skeletal Muscle
Junctophilin 1 and 2 Proteins Interact with the L-type Ca2+ Channel Dihydropyridine Receptors (DHPRs) in Skeletal Muscle
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DOI：
10.1074/jbc.m111.292755
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发表时间：
2011-12-23
影响因子：
4.8
通讯作者：
Sorrentino, Vincenzo
中科院分区：
文献类型：
--
作者：
Golini, Lucia;Chouabe, Christophe;Sorrentino, Vincenzo
亲结膜蛋白（JPs）将内质/肌浆网锚定在质膜上，从而促进横纹肌和神经元中连接膜复合物的组装。最近的研究表明，JPs也可能参与调节Ca2+稳态。在这里，我们报道了在骨骼肌中，JP1和JP2是一个复合体的一部分，除了ryanodine受体1 （RyR1）外，还包括caveolin 3和二氢吡啶受体（DHPR）。JPs与DHPR的相互作用由JP1和JP2中分别包含230-369和216-399氨基酸的区域介导。免疫荧光研究显示，与对照细胞相比，在JP1和JP2敲除的C2C12细胞中，DHPR和RyR信号的模式相当分散，并且具有较小的点。功能实验显示，在分化的C2C12细胞中，JPs的下调导致膜内电荷运动和l型Ca2+电流减少，同时质膜上dhpr数量减少，而固醇调节元件结合蛋白的Ca2+释放没有明显改变。综上所述，这些结果表明JP1和JP2可以促进DHPR与其他兴奋-收缩耦合机制蛋白的组装。
Junctophilins (JPs) anchor the endo/sarcoplasmic reticulum to the plasma membrane, thus contributing to the assembly of junctional membrane complexes in striated muscles and neurons. Recent studies have shown that JPs may be also involved in regulating Ca2+ homeostasis. Here, we report that in skeletal muscle, JP1 and JP2 are part of a complex that, in addition to ryanodine receptor 1 (RyR1), includes caveolin 3 and the dihydropyridine receptor (DHPR). The interaction between JPs and DHPR was mediated by a region encompassing amino acids 230-369 and amino acids 216-399 in JP1 and JP2, respectively. Immunofluorescence studies revealed that the pattern of DHPR and RyR signals in C2C12 cells knocked down for JP1 and JP2 was rather diffused and characterized by smaller puncta in contrast to that observed in control cells. Functional experiments revealed that down-regulation of JPs in differentiated C2C12 cells resulted in a reduction of intramembrane charge movement and the L-type Ca2+ current accompanied by a reduced number of DHPRs at the plasma membrane, whereas there was no substantial alteration in Ca2+ release from the sterol regulatory element-binding protein. Altogether, these results suggest that JP1 and JP2 can facilitate the assembly of DHPR with other proteins of the excitation-contraction coupling machinery.