LIPID CONTROL OF G PROTEIN GATED K CHANNEL ACTIVITY

离子通道功能的分子研究主要集中在 蛋白质本身或它们与其他蛋白质的相互作用， 离子。 例如，G蛋白门控K通道（KG）被认为是 由GTP结合蛋白的β γ亚基直接激活 （Gbetagamma亚单位）。 KG通道激活的当前模型涉及 G蛋白亚基分离（使其具有活性）和相互作用 与通道子单元。我们的初步结果表明， γ亚单位/KG通道相互作用需要PIP 2的存在 在膜中，以显示其对通道活性的影响。 这一令人惊讶的结果直接伴随着其他效应 可归因于PIP 2，例如KG的MgATP依赖性致敏作用。 通道的门控内部钠离子和可能的MgATP依赖性 降低G蛋白对KG通道活性的刺激。 这些结果 以及最近两份有关内部整顿的报告 通道KATP和Na / Ca转运蛋白（但不对Na通道或 Na / K泵）预示着一个未开发的研究领域的潜力， 对膜蛋白的功能完整性至关重要。 我们的建议 旨在详细研究脂质的影响，特别是 磷脂对KG通道功能的影响。 概述的实验将 进一步测试PIP 2效应的分子基础和意义 对KG通道活性和G蛋白亚基KG的依赖性 通道激活的PIP 2的存在。已经提出 脂质效应本质上是静电效应。 我们将测试这个 假设，并寻求确定在通道中的基本残留物 序列构成与阴离子相互作用的位点 磷脂 磷脂酰肌醇循环的磷脂允许 脂质在信号传导中的动态参与。 我们相信，一个更好的 对KG通道功能的分子细节的理解， 通过这项研究将允许更成功地操纵这个心房 控制室上性心律失常。 例如，在一个示例中， 我们最近发现的心房肌MgATP依赖性敏化 KG通道（KACh）通过内部Na离子门控允许我们 表明洋地黄治疗导致心房细胞激活 KACh（由于它引起的Na积累），提供了一个重要的联系 这种药物对室上性心律的长期影响。

Molecular studies of ion channel function have primarily focused on the proteins themselves or on their interactions with other proteins or ions. G protein-gated K channels (KG) for example are thought to be directly activated by the betagamma subunits of GTP binding proteins (Gbetagamma subunits). Current models of KG channel activation involve G protein subunit separation (which renders them active) and interaction with the channel subunits. Our preliminary results suggest that the Gbetagamma subunit/KG channel interaction requires the presence of PIP2 in the membrane in order to manifest its effects on channel activity. This surprising result is accompanied by other effects directly attributable to PIP2, such as the MgATP-dependent sensitization of KG channels to gating by internal Na ions and possibly the MgATP-dependent rundown of G protein stimulation of KG channel activity. These results together with two recent reports on the related inwardly rectifying channel KATP and on the Na / Ca transporter (but not on Na channels or Na / K pumps) herald the potential of an unexplored area of research, crucial to the functional integrity of membrane proteins. Our proposal aims to study in detail the effects of lipids, and in particular phospholipids on KG channel function. The experiments outlined will test further the molecular basis and significance of the PIP2 effects on KG channel activity and the dependence of G protein subunit KG channel activation on the presence of PIP2. It has been proposed that the lipid effects are electrostatic in nature. We will test this hypothesis and seek to identify the basic residues in the channel sequence constituting sites of interaction with the anionic phospholipids. Phospholipids of the phosphoinositide cycle allow dynamic participation of lipids in signaling. We believe that a better appreciation of the molecular details of KG channel function afforded by this study will allow more successful manipulation of this atrial channel in the control of supraventricular arrhythmias. For example, our recent discovery of the MgATP-dependent sensitization of the atrial KG channel (KACh) to gating by internal Na ions allowed us to demonstrate that digitalis treatment causes atrial cells to activate KACh (due to the Na accumulation it causes), providing an important link to the long known effects of this drug on supraventricular rhythm.