MOLECULAR-CLONING OF A PUTATIVE TETRODOTOXIN-RESISTANT RAT-HEART NA+ CHANNEL ISOFORM
MOLECULAR-CLONING OF A PUTATIVE TETRODOTOXIN-RESISTANT RAT-HEART NA+ CHANNEL ISOFORM
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DOI：
10.1073/pnas.86.20.8170
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发表时间：
1989-10-01
影响因子：
11.1
通讯作者：
KAISER, MW
中科院分区：
文献类型：
--
作者：
ROGART, RB;CRIBBS, LL;KAISER, MW
哺乳动物心脏中的电压门控Na+通道不同于神经和骨骼肌中的电压门控Na+通道。一个主要区别是河豚毒素（TTX）抗性心脏Na+通道被1-10 μ M TTX阻断，而TTX敏感性神经Na+通道被纳摩尔浓度的TTX阻断。我们构建了一个cDNA文库，从6日龄大鼠心脏，其中只有低亲和力[3 H]石房蛤毒素受体，对应于TTX耐Na+通道，被检测到。我们分离了几个重叠的cDNA克隆，其包含7542个核苷酸并编码整个α。心脏特异性Na+通道亚型（命名为大鼠心脏I）的亚基以及几个大鼠脑I Na+通道cDNA克隆。衍生的氨基酸序列的大鼠心脏I是高度同源的，但不同的形式，以前的Na+通道克隆。RNA酶保护研究表明，相应的mRNA种类是丰富的新生和成年大鼠的心脏，但在大脑或受神经支配的骨骼肌检测不到。骨骼肌失神经支配后出现相同的mRNA种类，可能解释了新的TTX抗性Na+通道的表达。因此，这种心脏特异性Na+通道克隆似乎编码一种独特的TTX抗性同种型，并且是哺乳动物Na+通道多基因家族的另一个成员，在新生儿心脏和失神经骨骼肌中发现。
Voltage-gated Na+ channels in mammalian heart differ from those in nerve and skeletal muscle. One major difference is that tetrodotoxin (TTX)-resistant cardiac Na+ channels are blocked by 1-10 .mu.M TTX, whereas TTX-sensitive nerve Na+ channels are blocked by nanomolar TTX concentrations. We constructed a cDNA library from 6-day-old rat hearts, where only low-affinity [3H]saxitoxin receptors, corresponding to TTX-resistant Na+ channels, were detected. We isolated several overlapping cDNA clones encompassing 7542 nucleotides and encoding the entire .alpha. subunit of a cardiac-specific Na+ channel isoform (designated rat heart I) as well as several rat brain I Na+ channel cDNA clones. The derived amino acid sequence of rat heart I was highly homologous to, but distinct form, previous Na+ channel clones. RNase protection studies showed that the corresponding mRNA species is abundant in newborn and adult rat hearts, but not detectable in brain or innervated skeletal muscle. The same mRNA species appears upon denerva tion of skeletal muscle, likely accounting for expression of new TTX-resistant Na+ channels. Thus, this cardiac-specific Na+ channel clone appears to encode a distinct TTX-resistant isoform and is another member of the mammalian Na+ channel multigene family, found in newborn heart and denervated skeletal muscles.