Mikami A, Imoto K, Tanabe T, Niidome T, Mori Y, Takeshima H, Narumiya S, Numa S
Department of Medical Chemistry Kyoto University Faculty of Medicine, Japan.
Nature. 1989 Jul 20;340(6230):230-3. doi: 10.1038/340230a0.
In cardiac muscle, where Ca2+ influx across the sarcolemma is essential for contraction, the dihydropyridine (DHP)-sensitive L-type calcium channel represents the major entry pathway of extracellular Ca2+. We have previously elucidated the primary structure of the rabbit skeletal muscle DHP receptor by cloning and sequencing the complementary DNA. An expression plasmid carrying this cDNA, microinjected into cultured skeletal muscle cells from mice with muscular dysgenesis, has been shown to restore both excitation-contraction coupling and slow calcium current missing from these cells, so that a dual role for the DHP receptor in skeletal muscle transverse tubules is suggested. We report here the complete amino-acid sequence of the rabbit cardiac DHP receptor, deduced from the cDNA sequence. We also show that messenger RNA derived from the cardiac DHP receptor cDNA is sufficient to direct the formation of a functional DHP-sensitive calcium channel in Xenopus oocytes. Furthermore, higher calcium-channel activity is observed when mRNA specific for the polypeptide of relative molecular mass approximately 140,000 (alpha 2-subunit) associated with skeletal muscle DHP receptor is co-injected.
在心肌中，跨肌膜的Ca2+内流对收缩至关重要，二氢吡啶（DHP）敏感的L型钙通道是细胞外Ca2+的主要进入途径。我们之前通过对互补DNA进行克隆和测序，阐明了兔骨骼肌DHP受体的一级结构。已证明，将携带此cDNA的表达质粒显微注射到患有肌肉发育不全的小鼠的培养骨骼肌细胞中，可恢复这些细胞中缺失的兴奋-收缩偶联和慢钙电流，因此提示DHP受体在骨骼肌横管中具有双重作用。我们在此报告从cDNA序列推导出来的兔心脏DHP受体的完整氨基酸序列。我们还表明，源自心脏DHP受体cDNA的信使RNA足以指导非洲爪蟾卵母细胞中功能性DHP敏感钙通道的形成。此外，当与骨骼肌DHP受体相关的相对分子质量约为140,000的多肽（α2亚基）的特异性mRNA共注射时，可观察到更高的钙通道活性。
