Ion Channel Regulation By Signal Transduction Pathways

我们重点研究了三种特异性离子通道：CaV1.2，Kv11.1，BKca。 CaV1.2通道显示由二氢吡啶、蛋白磷酸化和钙调节的模式门控。我们已经从单通道记录中获得了新的证据，即二氢吡啶通过改变它们对磷酸化的敏感性来调节通道活性。此外，钙通过通道蛋白的去磷酸化抑制通道活性。 人类ether-a-go-go相关基因1 hERG 1的多态性与心律失常相关由hERG 1编码的Kv11.1通道对于垂体的节律性兴奋性也是必不可少的，其中它们通过涉及磷脂酰肌醇3-激酶（PI 3 K）和Ser/Thr定向蛋白磷酸酶PP 5的信号转导级联由甲状腺激素调节。在这里，我们表明，hERG 1的多态性在密码子897，这是作为一个苏氨酸而不是赖氨酸阅读，创建一个新的磷酸化位点的Akt蛋白激酶的Kv11.1通道蛋白。因此，通过PI 3 K信号级联的激素信号传导（其通常通过PP 5介导的去磷酸化刺激K897通道）通过Akt介导的磷酸化抑制T897通道。因此，在具有T897多态性的人类中，Kv11.1的激素调节被预测为延长心肌细胞的QT间期。对人类离子通道基因中单核苷酸多态性的系统生物信息学搜索确定了15个额外的候选人，这些候选人被预测会产生或破坏推定的磷酸化位点。蛋白质磷酸化的变化可能代表遗传变异对人类健康及其与环境相互作用的影响的一般机制。 BKca钾通道由KCNMA 1基因编码，调节内分泌细胞和神经末梢的动作电位时程。无脊椎动物模式生物中乙醇对运动协调作用的遗传研究已经确定BKca通道是乙醇作用的重要靶点。其他研究已经确定Gs-cAMP-PKA信号系统作为乙醇作用的靶标。因此，我们在模式遗传生物C.优雅我们确定了ceBKca上的PKA位点;当它突变时，蠕虫对高达500 mM的乙醇不敏感！通过在ce神经元中靶向表达哺乳动物抑制蛋白来抑制Ser/Thr蛋白磷酸酶PP 1也阻止了乙醇破坏运动。我们已经证实了这种依赖性的乙醇行动对PP 1活性在大鼠海马切片，其中乙醇抑制LTP对CA 1锥体树突。与Birnbaumer博士的小组合作，TRPC通道参与了响应于通过Gq偶联受体的信号传导的钙进入。

We have focused on three specific ion channels: CaV1.2, Kv11.1, BKca. CaV1.2 channels show modal gating that is regulated by dihydropyridine, protein phosphorylatiion, and calcium. We have obtained new evidence from single channel recordings that dihydropyridines modulate channel activity by altering their susceptibility to phosphorylation. Furthermore, calcium inhibits channel activity through dephosphorylation of the channel protein. Polymorphisms in the human ether-a-go-go-related gene 1, hERG1, are associated with cardiac arrhythmias. The Kv11.1 channels encoded by hERG1 are also essential for rhythmic excitability of the pituitary, where they are regulated by thyroid hormone through a signal transduction cascade involving the phosphatidylinositol 3-kinase (PI3K) and the Ser/Thr-directed protein phosphatase, PP5. Here we show that the hERG1 polymorphism at codon 897, which is read as a Thr instead of a Lys, creates a new phosphorylation site for the Akt protein kinase on the Kv11.1 channel protein. Consequently hormonal signaling through the PI3K signaling cascade, which normally stimulates K897 channels through PP5-mediated dephosphorylation, inhibits T897 channels through Akt-mediated phosphorylation. Thus, hormonal regulation of Kv11.1 in humans with the T897 polymorphism is predicted to prolong the QT interval of cardiac myocytes. A systematic bioinformatics search for single nucleotide polymorphisms in human ion channel genes identified fifteen additional candidates for such "phosphorylopathies," which are predicted to create or destroy putative phosphorylation sites. Changes in protein phosphorylation might represent a general mechanism for the effects of genetic variation on human health and its interaction with the environment. The BKca potassium channels, which are encoded by the KCNMA1 gene (slo) and regulate action potential duration in endocrine cells and nerve terminals. Genetic studies of ethanol action on locomotor coordination in invertebrate model organisms have identified BKca channels as a prominent target of ethanol action. Other studies have identified the Gs-cAMP-PKA signaling system as a target of ethanol action. Therefore, we have studied the mechanism of BKca regulation by ethanol in a model genetic organism, C. elegans. We identified the PKA site on ceBKca; when it was mutated the worms were impervious to ethanol up t o 500 mM ! Inhibition of the Ser/Thr protein phosphatase PP1 by targeted expression of a mammalian inhibitor protein in ce neurons also prevented ethanol from disrupting locomotion. We have confirmed this dependence of ethanol action on PP1 activity in rat hippocampal slices, in which ethanol inhibits LTP on CA1 pyramidal dendrites. In collaboration with Dr. Birnbaumer's group, TRPC channels have been implicated in calcium entry in response to signaling through Gq coupled receptors.