The II-III loop of the skeletal muscle dihydropyridine receptor is responsible for the bi-directional coupling with the ryanodine receptor
The II-III loop of the skeletal muscle dihydropyridine receptor is responsible for the bi-directional coupling with the ryanodine receptor
复制标题
DOI：
10.1074/jbc.274.31.21913
复制
发表时间：
1999-07-30
影响因子：
4.8
通讯作者：
Beam, KG
中科院分区：
文献类型：
--
作者：
Grabner, M;Dirksen, RT;Beam, KG
骨骼肌质膜上的二氢吡啶受体（DHPR）既是电压门控性钙通道，又是兴奋-收缩（EC）偶联的电压感受器。作为电压传感器，DHPR通过兰尼碱受体（RyR-1）的骨架亚型调节细胞内Ca 2+释放。与RyR-1的相互作用也反馈以增加由DHPR介导的Ca 2+电流。为了鉴定对于从RyR-1接收该信号重要的DHPR区域，我们在发育不良的肌管中表达了具有骨架（Sk）DHPR序列的嵌合体（SkLC），除了心脏（C）II-III环（L）。用绿色荧光蛋白（GFP）标记使得能够鉴定表达的肌管，表达GFP-SkLC或SkLC的基因缺陷型肌管缺乏EC偶联，并且具有非常小的Ca 2+电流。将短骨架片段（α（1 S）残基720-765）引入GFP-SkLC的心脏II-III环（替代α（1C）残基851-896）中恢复了EC偶联和Ca 2+电流密度，就像野生型骨架DHPR的那些一样。最近显示骨架序列的这一46个氨基酸的延伸能够将强的血管型EC偶联转移到另外的心脏DHPR（Nakai，J.，田边，T.，Konno，T.，亚当斯，B，和Beam，K.G.（1998）J. Biol. Chem，273，24983-24986）。因此，骨架II-III环的这一区段含有细胞型EC偶联和RyR-1介导的Ca 2+电流增强所需的基序。
The dihydropyridine receptor (DHPR) in the skeletal muscle plasmalemma functions as both voltage-gated Ca2+ channel and voltage sensor for excitation-contraction (EC) coupling. As voltage sensor, the DHPR regulates intracellular Ca2+ release via the skeletal isoform of the ryanodine receptor (RyR-1). Interaction with RyR-1 also feeds back to increase the Ca2+ current mediated by the DHPR, To identify regions of the DHPR important for receiving this signal from RyR-1, we expressed in dysgenic myotubes a chimera (SkLC) having skeletal (Sk) DHPR sequence except for a cardiac (C) II-III loop (L), Tagging with green fluorescent protein (GFP) enabled identification of expressing myotubes, Dysgenic myotubes expressing GFP-SkLC or SkLC lacked EC coupling and had very small Ca2+ currents. Introducing a short skeletal segment (alpha(1S) residues 720-765) into the cardiac II-III loop (replacing alpha(1C) residues 851-896) of GFP-SkLC restored both EC coupling and Ca2+ current densities like those of the wild type skeletal DHPR. This 46-amino acid stretch of skeletal sequence was recently shown to be capable of transferring strong, skeletal-type EC coupling to an otherwise cardiac DHPR (Nakai, J., Tanabe, T., Konno, T., Adams, B., and Beam, K.G. (1998) J. Biol. Chem, 273, 24983-24986), Thus, this segment of the skeletal II-III loop contains a motif required for both skeletal-type EC coupling and RyR-1-mediated enhancement of Ca2+ current.