STIMULATORY AND INHIBITORY REGULATION OF CALCIUM-ACTIVATED POTASSIUM CHANNELS BY GUANINE NUCLEOTIDE-BINDING PROTEINS
STIMULATORY AND INHIBITORY REGULATION OF CALCIUM-ACTIVATED POTASSIUM CHANNELS BY GUANINE NUCLEOTIDE-BINDING PROTEINS
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DOI：
10.1073/pnas.89.22.11051
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发表时间：
1992-11-15
影响因子：
11.1
通讯作者：
KOTLIKOFF, MI
中科院分区：
文献类型：
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作者：
KUME, H;GRAZIANO, MP;KOTLIKOFF, MI
鸟嘌呤核苷酸结合蛋白（G蛋白）对膜离子通道的调节在许多组织中都有报道。这种调节已被证明涉及G蛋白对离子通道的膜界定刺激作用。我们现在表明，单一的钙激活钾通道（K（Ca）通道）在气道平滑肌细胞的刺激和抑制G蛋白在膜补丁。我们证明β-肾上腺素能激动剂异丙肾上腺素通过腺苷酸环化酶刺激性G蛋白的α亚基G（s）刺激通道活性，并且通过毒蕈碱激动剂乙酰甲胆碱的作用抑制通道开放，乙酰甲胆碱通过百日咳毒素敏感的G蛋白起作用。异丙肾上腺素刺激和乙酰甲胆碱抑制通道活性在相同的外向补丁时，GTP存在于细胞溶质表面的补丁。在由内而外的贴片中，当贴片移液管中含有异丙肾上腺素时，加入GTP和鸟苷5 '-[γ-硫代]三磷酸（GTP[γ S]）可增强通道活性，而当移液管中含有乙酰甲胆碱时，则可抑制通道活性。与这些结果一致，在存在GTP[gammaS]的情况下，G（s）的α亚基（α（s）.GTP[gammaS]复合物）以剂量依赖性方式打开K（Ca）通道，而在存在鸟苷5 '-[β-硫代]二磷酸的情况下，α（s）没有作用。相比之下，激活的α（i）或α（o）蛋白的应用并没有抑制通道活性的内面向外补丁，表明通道抑制比简单的α亚基/通道相互作用更复杂，类似于腺苷酸环化酶的复杂抑制性调节。这些结果表明，激素调节的K（Ca）通道与腺苷酸环化酶的调节有很大的特点，并表明一个单一的离子通道可以作为膜界定的刺激性和抑制性G蛋白的作用的调节目标。此外，它们证明了一种潜在的重要功能途径，通过该途径，β-肾上腺素能受体和其他G（s）-连接受体刺激平滑肌松弛，而不依赖于cAMP依赖性蛋白磷酸化。
The regulation of membrane ion channels by guanine nucleotide-binding proteins (G proteins) has been described in numerous tissues. This regulation has been shown to involve the membrane-delimited stimulatory action of G proteins on ion channels. We now show that single calcium-activated potassium channels (K(Ca) channels) in airway smooth muscle cells are both stimulated and inhibited by G proteins in membrane patches. We demonstrate that the beta-adrenergic agonist isoproterenol stimulates channel activity via the alpha subunit of the stimulatory G protein of adenylyl cyclase, G(s), and that channel opening is inhibited by the action of the muscarinic agonist methacholine, acting via a pertussis toxin-sensitive G protein. Isoproterenol stimulated and methacholine inhibited channel activity in the same outside-out patches when GTP was present at the cytosolic surface of the patch. In inside-out patches, addition of GTP and guanosine 5'-[gamma-thio] triphosphate (GTP[gammaS]) augmented channel activity when isoproterenol was included in the patch pipette, and inhibited channel activity when methacholine was included in the pipette. Consistent with these results, in the presence of GTP[gammaS], the alpha subunit of G(s) (alpha(s).GTP[gammaS] complex) opened K(Ca) channels in a dose-dependent manner, whereas in the presence of guanosine 5'-[beta-thio]diphosphate, alpha(s) had no effect. By contrast, application of activated alpha(i) or alpha(o) proteins did not inhibit channel activity in inside-out patches, indicating that channel inhibition is more complex than a simple alpha subunit/channel interaction, similar to the complex inhibitory regulation of adenylyl cyclase. These results suggest that hormonal regulation of K(Ca) channels shares substantial features with the regulation of adenylyl cyclase and demonstrate that a single ion channel may serve as the regulatory target for the membrane-delimited action of stimulatory and inhibitory G proteins. Moreover, they demonstrate a potentially important functional pathway by which beta-adrenergic and other G(s)-linked receptors stimulate relaxation of smooth muscle, independent of cAMP-dependent protein phosphorylation.