The physiological roles and molecular basis of polarized localization of K+ channels in the vectorial transports of ions and water.

K 通道在离子和水的矢量传输中极化定位的生理作用和分子基础。

基本信息

批准号：
12144207
负责人：
KURACHI Yoshihisa
金额：
$ 94.27万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2005
项目状态：
已结题

项目摘要

We examined physiological roles of inwardly-rectifying K^+-channels in vectorial-transports of epithelia, by analyzing (1) polarized kralization of the channels in various cells, and (2) regulation of their function. We investigated Kir4.1 and Kir5.1 for (1) and, additionally, ATP-sensitive K^+-channels (K_<ATP>) and G-protein gated K^+-channels (K_G) for (2).(A) Specific localization of Kir4.1 and Kir5.1 and their functionWe found three multimers, Kir4.1-homomer, Kir5.1-homomer, and Kir41/5.1-heteromer, existed in vivo and differentially distributed in specific membrane domains of glia and epithelia. We further identified diversity of subunit-assembly and distribution functionally contributed to vectorial-transports of K^+.(a) In renal epithelia, the heteromer distributes at their basolateral membrane and acts as an "intracellular pH-sensor'.(b) In cochlea, the two homomers occur in distinct tissues and mediate K^+-circulation essential for hearing.(c) In brain astrocytes and retinal … More Muller cells, Kir4.1-homomer and Kir4.1/5.1-heteromer differentially distribute in pweicascular and perisynaptic processes and play distinct roles in K^+-buffering.(d) These channels are targeted to the membrane by dystrophin-associated protein-complex, and clustered in a microdomain called "lipid-raft' where they are functionally coupled to water channel AQP4.(B) Regulation of function of K_GCardiac K_G has a characteristic voltage-dependent gate-property called "relaxation". We identified its molecular basis as followings-(a) The relaxation is dramatically regulated by "RGS(Regulator of G-protein Signaling)".(b) This regulation involves PIP_3-inhibition of RGS and its reversal by Ca^<2+>/calmodulin.(c) PIP_3 and Ca^<2+>/calmoclulin competitively bind RGS and reciprocally regulate its action.(C) Structure and function of K_<ATP>, (Kir6.x+SUR)We established structure-model of SUR and explained mechanism of regulation of K_<ATP>, by intracellular ADP. Furthermore, we found that dimerization of two nucleotide-binding domains was essential for opening the channel-pore.We found that Ca^<2+> released to inside of nucleus by NADDP receptor-channel on nuclear envelope mediated transit of information from cytosol to nucleus. Less

我们通过分析（1）各种细胞中通道的极化kralation偏振kralization在矢量传输中的内向k^+通道的身体作用，以及（2）调节其功能。我们研究了（1）的Kir4.1和Kir5.1，此外，ATP敏感的K^+ - 通道（K_ <ATP>）和G蛋白Gated Gated Gated Gated Gated K^+ - 通道（K_G）（K_G）（k_g）（2）。 KIR41/5.1-螺态物存在于体内，分布在特定的神经胶质和上皮膜中。我们进一步确定了亚基组件和分布的多样性，在功能上有助于K^+。（a）在肾上皮中的矢量传输，其基底外侧膜上的异构体分布，并用作“ Cochlea的细胞内pH传感器”。星形胶质细胞和视网膜……更多的Muller细胞，Kir4.1-词素和Kir4.1/5.1-近距离分布在pWeicancular和pweicancular and Cerynaptic过程中分布不同，并在K^+缓冲中起着不同的作用。在功能上耦合到水通道AQP4。（b）k_gcardiac k_g功能的调节具有特征性的电压依赖性栅极 - 栅极式栅极，称为“弛豫”。我们将其分子基础确定为以下 - （a）松弛受“ RGS（G蛋白信号的调节剂）”的显着调节。（b）此调节涉及RGS的pip_3抑制RG，并由Ca^<2+>/Calsodulin ca逆转。（c）K_ <ATP>，（Kir6.x+SUR）的结构和功能，我们通过细胞内ADP建立了SUR的结构模型，并解释了K_ <ATP>调节的机理。此外，我们发现两个核厄当结合结构域的二聚化对于打开通道孔是至关重要的。我们发现，NADDP受体渠道释放到核核核通道上的CA^<2+>在核核中介导的信息从细胞溶胶到核的信息的传输。较少的