COUPLING OF ATP-SENSITIVE K+ CHANNELS TO A1-RECEPTORS BY G-PROTEINS IN RAT VENTRICULAR MYOCYTES
COUPLING OF ATP-SENSITIVE K+ CHANNELS TO A1-RECEPTORS BY G-PROTEINS IN RAT VENTRICULAR MYOCYTES
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DOI：
10.1152/ajpheart.1990.259.3.h820
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发表时间：
1990-09-01
影响因子：
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通讯作者：
BROWN, AM
中科院分区：
文献类型：
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作者：
KIRSCH, GE;CODINA, J;BROWN, AM
ATP敏感性K ~+-（K ~+[ATP]）电流被认为是受GTP结合蛋白（G蛋白）调节的，但连接受体、G蛋白和通道的途径尚未确定。我们研究了新生大鼠心室肌细胞甲苯磺丁脲敏感性K+[ATP]电流的调节。将0.1mM ATP施加到膜斑的细胞内侧降低了K+ [ATP]通道活性，并且添加0.1mM的不可水解的GTP类似物鸟苷5“-O-（3-硫代三磷酸）（GTP γ S）恢复了活性。应用0.1mM细胞内GTP加上10 μ M细胞外腺苷或100 nM N6-环己基腺苷具有与GTP γ S相同的效果;因此K+[ATP]通道可以通过G蛋白偶联至腺苷受体。为了确定哪种G蛋白，我们应用G α。亚基，用GTP γ S预活化至膜斑的细胞质侧，并发现α i1、α i2和α i3模拟GTP γ S的作用，但不模拟α o或Gs的作用，这表明Gi α i和α i 1、α i 2和α i 3在细胞膜斑的细胞质侧具有相同的作用。通过膜界定的途径起作用。腺苷受体偶联可能对激活缺血肌肉中的K+[ATP]通道起重要作用。
ATP-sensitive K+-(K+[ATP]) current is thought to be regulated by GTP-binding proteins (G proteins), but the pathways that couple receptor, G protein, and channel have not been defined. We studied regulation of tolbutamide-sensitive K+[ATP] current in neonatal rat ventricular myocytes. Application of 0.1 mM ATP to the intracellular side of membrane patches reduced K+ [ATP] channel activity, and addition of the nonhydrolyzable GTP analogue guanosine 5''-O-(3-thiotriphosphate) (GTP.gamma.S) at 0.1 mM restored activity. Application of 0.1 mM intracellular GTP plus 10 .mu.M extracellular adenosine or 100 nM N6-cyclohexyladenosine had the same effect as GTP.gamma.S; hence K+[ATP] channels may be coupled to adenosine receptors via G proteins. To determine which G protein, we applied G.alpha. subunits, preactivated with GTP.gamma.S to the cytoplasmic side of membrane patches, and found that .alpha.i1, .alpha.i2 and .alpha.i3 mimicked the effect of GTP.gamma.S, but not .alpha.o or Gs, suggesting that Gi.alpha. acts via a membrane-delimited pathway. Adenosine receptor coupling may be important for activating K+[ATP] channels in ischemic muscle.