Properties of cyclic nucleotide-gated channels mediating olfactory transduction. Activation, selectivity, and blockage.
Properties of cyclic nucleotide-gated channels mediating olfactory transduction. Activation, selectivity, and blockage.
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DOI：
10.1085/jgp.100.1.45
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发表时间：
1992-07
影响因子：
3.8
通讯作者：
Lindemann, B
中科院分区：
文献类型：
--
作者：
Frings, S;Lynch, J W;Lindemann, B
嗅觉受体细胞感觉膜中的环状核苷酸门控通道（cng 通道）在气味剂诱导的胞质 cAMP 浓度增加后被激活，传导受体电流，引起受体神经元的电兴奋。我们使用从分离的嗅觉受体细胞上切下的内外膜片研究了青蛙和大鼠的 cng 通道的特性。通道由cAMP和cGMP激活，cAMP的激活常数为2.5-4.0 microM，cGMP的激活常数为1.0-1.8。剂量反应曲线的希尔系数为1.4-1.8，表明配体结合的协同性。对一价碱金属阳离子的选择性和 Na/Li 摩尔分数行为将该通道识别为非选择性阳离子通道，在孔中具有高场强的阳离子结合位点。胞质 pH 效应表明存在额外的可滴定基团，该基团在质子化时会抑制 cAMP 诱导的电流，表观 pK 为 5.0-5.2。 pH 值的影响不依赖于电压。几种 Ca2+ 通道阻滞剂也会阻断嗅觉 CNG 通道。阿米洛利、D 600 和地尔硫卓从胞浆侧抑制 cAMP 诱导的电流。抑制常数与电压相关，-60 mV 时的值分别为 0.1、0.3 和 1 mM，+60 mV 时的值分别为 0.03、0.02 和 0.2 mM。我们的结果表明青蛙和大鼠 cng 通道之间的功能相似，以及光感受器和其他组织的 cng 通道的显着差异。
Cyclic nucleotide-gated channels (cng channels) in the sensory membrane of olfactory receptor cells, activated after the odorant-induced increase of cytosolic cAMP concentration, conduct the receptor current that elicits electrical excitation of the receptor neurons. We investigated properties of cng channels from frog and rat using inside- out and outside-out membrane patches excised from isolated olfactory receptor cells. Channels were activated by cAMP and cGMP with activation constants of 2.5-4.0 microM for cAMP and 1.0-1.8 for cGMP. Hill coefficients of dose-response curves were 1.4-1.8, indicating cooperativity of ligand binding. Selectivity for monovalent alkali cations and the Na/Li mole-fraction behavior identified the channel as a nonselective cation channel, having a cation-binding site of high field strength in the pore. Cytosolic pH effects suggest the presence of an additional titratable group which, when protonated, inhibits the cAMP-induced current with an apparent pK of 5.0-5.2. The pH effects were not voltage dependent. Several blockers of Ca2+ channels also blocked olfactory cng channels. Amiloride, D 600, and diltiazem inhibited the cAMP-induced current from the cytosolic side. Inhibition constants were voltage dependent with values of, respectively, 0.1, 0.3, and 1 mM at -60 mV, and 0.03, 0.02, and 0.2 mM at +60 mV. Our results suggest functional similarity between frog and rat cng channels, as well as marked differences to cng channels from photoreceptors and other tissues.