Dihydropyridine receptor alpha subunits in normal and dysgenic muscle in vitro: expression of alpha 1 is required for proper targeting and distribution of alpha 2.
Dihydropyridine receptor alpha subunits in normal and dysgenic muscle in vitro: expression of alpha 1 is required for proper targeting and distribution of alpha 2.
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DOI：
10.1083/jcb.115.5.1345
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发表时间：
1991-12
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影响因子：
--
通讯作者：
Powell JA
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作者：
Flucher BE;Phillips JL;Powell JA
用免疫荧光标记的方法研究了骨骼肌二氢吡啶(DHP)受体α1和α2亚单位在培养的正常和异常(MDG)肌中的亚细胞分布。在正常肌管中，两个α亚基均定位于与T小管膜相关的纵向和横向T小管膜上。DHP受体富集区可能代表与肌浆网形成三联体连接的部位。在发育不良肌肉的培养中，α1亚基未被检测到，而α2亚基的分布模式异常。α亚基既没有形成簇，也没有分散地定位在T小管系统中。相反，α2广泛分布在T系统的部分区域、核周区的结构和质膜中。这些结果表明，两个α亚基之间的相互作用是α2亚基在T小管膜中正常分布所必需的。正常的非肌肉细胞与发育不良的肌管自发融合，导致异体核附近的α1多肽的区域表达，从而定义了多核肌肉细胞中T管膜蛋白的核结构域。此外，在含有外源“挽救”核的区域内恢复了α2多肽在细胞内的正常分布；这支持了DHP受体α1和α2亚单位之间的直接相互作用参与了连接T管膜的组织的想法。
We have studied the subcellular distribution of the alpha 1 and alpha 2 subunits of the skeletal muscle dihydropyridine (DHP) receptor with immunofluorescence labeling of normal and dysgenic (mdg) muscle in culture. In normal myotubes both alpha subunits were localized in clusters associated with the T-tubule membranes of longitudinally as well as transversely oriented T-tubules. The DHP receptor-rich domains may represent the sites where triad junctions with the sarcoplasmic reticulum are being formed. In cultures from dysgenic muscle the alpha 1 subunit was undetectable and the distribution patterns of the alpha 2 subunit were abnormal. The alpha subunit did not form clusters nor was it discretely localized in the T-tubule system. Instead, alpha 2 was found diffusely distributed in parts of the T-system, in structures in the perinuclear region and in the plasma membrane. These results suggest that an interaction between the two alpha subunits is required for the normal distribution of the alpha 2 subunit in the T-tubule membranes. Spontaneous fusion of normal non-muscle cells with dysgenic myotubes resulted in a regional expression of the alpha 1 polypeptide near the foreign nuclei, thus defining the nuclear domain of a T-tubule membrane protein in multi-nucleated muscle cells. Furthermore, the normal intracellular distribution of the alpha 2 polypeptide was restored in domains containing a foreign "rescue" nucleus; this supports the idea that direct interactions between the DHP receptor alpha 1 and alpha 2 subunits are involved in the organization of the junctional T-tubule membranes.