The Ca-activated Cl channel and its control in rat olfactory receptor neurons.
The Ca-activated Cl channel and its control in rat olfactory receptor neurons.
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CA激活的CL通道及其在大鼠嗅觉受体神经元中的控制。
DOI：
10.1085/jgp.200308888
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发表时间：
2003-09
影响因子：
3.8
通讯作者：
Frings, Stephan
中科院分区：
文献类型：
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作者：
Reisert, Johannes;Bauer, Paul J;Yau, King-Wai;Frings, Stephan
气味剂通过cAMP信号级联激活嗅觉受体神经元（ORN）中的感觉传导，这导致非选择性环核苷酸门控（CNG）通道的开放。随后通过CNG通道的Ca 2+内流激活Cl通道，Cl通道用于放大转导信号。我们在这里调查的一些一般特性，这种钙激活的氯离子通道在大鼠，以及其功能与CNG通道的相互作用，通过使用从ORN树突状旋钮/纤毛切下的膜补丁。在生理浓度的外部二价阳离子，最大激活的Cl电流是CNG电流的2.30倍。Ca ~（2+）可通过cAMP开放的CNG通道激活离体膜片上的Cl通道。氯电流的大小取决于浴液中Ca缓冲的强度，这表明CNG和氯通道可能没有组织为局部转导体复合物的成分。同样地，Cl通道和Na/Ca交换器（其挤出Ca 2+）似乎在空间上分离。基于缓冲Ca 2+扩散理论，我们测定了Ca 2+扩散系数，并计算出膜上CNG和Cl通道密度分别为108和62 μm−2。这些密度，连同Ca 2+的扩散系数，表明一个给定的Cl通道被激活的Ca 2+源自多个CNG通道，从而允许低噪声放大的嗅觉受体电流。
Odorants activate sensory transduction in olfactory receptor neurons (ORNs) via a cAMP-signaling cascade, which results in the opening of nonselective, cyclic nucleotide–gated (CNG) channels. The consequent Ca2+ influx through CNG channels activates Cl channels, which serve to amplify the transduction signal. We investigate here some general properties of this Ca-activated Cl channel in rat, as well as its functional interplay with the CNG channel, by using inside-out membrane patches excised from ORN dendritic knobs/cilia. At physiological concentrations of external divalent cations, the maximally activated Cl current was ∼30 times as large as the CNG current. The Cl channels on an excised patch could be activated by Ca2+ flux through the CNG channels opened by cAMP. The magnitude of the Cl current depended on the strength of Ca buffering in the bath solution, suggesting that the CNG and Cl channels were probably not organized as constituents of a local transducisome complex. Likewise, Cl channels and the Na/Ca exchanger, which extrudes Ca2+, appear to be spatially segregated. Based on the theory of buffered Ca2+ diffusion, we determined the Ca2+ diffusion coefficient and calculated that the CNG and Cl channel densities on the membrane were ∼8 and 62 μm−2, respectively. These densities, together with the Ca2+ diffusion coefficient, demonstrate that a given Cl channel is activated by Ca2+ originating from multiple CNG channels, thus allowing low-noise amplification of the olfactory receptor current.