Structural elements in the Girk1 subunit that potentiate G protein-gated potassium channel activity
Structural elements in the Girk1 subunit that potentiate G protein-gated potassium channel activity
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DOI：
10.1073/pnas.1212019110
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发表时间：
2012-12-26
影响因子：
11.1
通讯作者：
Wickman, Kevin
中科院分区：
文献类型：
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作者：
Wydeven, Nicole;Young, Daniele;Wickman, Kevin
G蛋白门控的内向整流K+ (Girk/K(IR)3)通道介导多种神经递质对兴奋性细胞的抑制作用。Girk通道是由四种哺乳动物Girk亚基（Girk1至-4）的不同组合组成的四聚体。虽然Girk1不能形成功能性的同质通道，但其在心脏和神经元通道复合物中的存在与强大的通道活性相关。本研究利用GABA(B)受体和Girk1/Girk2异聚体作为模型系统，试图更好地理解Girk1的增强作用。在转染的细胞或海马神经元中，Girk1没有增加蛋白质水平或改变含有girk2的通道到细胞表面的运输，这表明其增强影响包括通道活性的增强。远端羧基末端结构域和通道核心的结构元素被确定为稳健通道活性的关键决定因素。在远端羧基末端区域，残基Q404被确定为受体诱导通道活性的关键决定因素。在Girk1核心中，孔(P)环中的三个独特残基（F137, A142, Y150）被确定为对受体依赖性和非受体依赖性通道活性的集体增强影响，至少在一定程度上通过增加平均打开时间和单通道电导来发挥其影响。有趣的是，Girk1 P-loop的增强作用被第二跨膜结构域的残基F162缓和。因此，Girk1中不连续的和有时相反的元件是受体依赖性和受体非依赖性异质通道活性的Girk1依赖性增强的基础。
G protein-gated inwardly rectifying K+ (Girk/K(IR)3) channels mediate the inhibitory effect of many neurotransmitters on excitable cells. Girk channels are tetramers consisting of various combinations of four mammalian Girk subunits (Girk1 to -4). Although Girk1 is unable to form functional homomeric channels, its presence in cardiac and neuronal channel complexes correlates with robust channel activity. This study sought to better understand the potentiating influence of Girk1, using the GABA(B) receptor and Girk1/Girk2 heteromer as a model system. Girk1 did not increase the protein levels or alter the trafficking of Girk2-containing channels to the cell surface in transfected cells or hippocampal neurons, indicating that its potentiating influence involves enhancement of channel activity. Structural elements in both the distal carboxyl-terminal domain and channel core were identified as key determinants of robust channel activity. In the distal carboxyl-terminal domain, residue Q404 was identified as a key determinant of receptor-induced channel activity. In the Girk1 core, three unique residues in the pore (P) loop (F137, A142, Y150) were identified as a collective potentiating influence on both receptor-dependent and receptor-independent channel activity, exerting their influence, at least in part, by enhancing mean open time and single-channel conductance. Interestingly, the potentiating influence of the Girk1 P-loop is tempered by residue F162 in the second membrane-spanning domain. Thus, discontinuous and sometime opposing elements in Girk1 underlie the Girk1-dependent potentiation of receptor-dependent and receptor-independent heteromeric channel activity.