Liman E R, Buck L B
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115.
Neuron. 1994 Sep;13(3):611-21. doi: 10.1016/0896-6273(94)90029-9.
Sensory transduction in olfactory neurons is mediated by intracellular cAMP, which directly gates a nonselective cation channel. A cDNA encoding a cyclic nucleotide-gated (CNG) ion channel subunit (rOCNC1) has been cloned previously from rat olfactory epithelium. However, differences between the functional properties of rOCNC1 and the native olfactory CNG channel suggest that the native channel could be composed of several distinct subunit types. Here, we report the cloning and characterization of a cDNA encoding a second olfactory CNG channel subunit (rOCNC2) that is 52% identical to rOCNC1 and that is expressed specifically in olfactory sensory neurons. Expression of rOCNC2 alone in Xenopus oocytes does not lead to detectable CNG currents. However, coexpression of rOCNC2 with rOCNC1 results in a CNG conductance that differs from that detected upon expression of rOCNC1 alone and more closely resembles the native conductance in several respects, including its sensitivity to cAMP. This suggests that the native olfactory CNG channel is a hetero-oligomer composed of rOCNC1 and rOCNC2 subunits.
嗅觉神经元中的感觉转导由细胞内的环磷酸腺苷（cAMP）介导，cAMP直接控制一个非选择性阳离子通道。先前已从大鼠嗅觉上皮中克隆出编码一种环核苷酸门控（CNG）离子通道亚基（rOCNC1）的cDNA。然而，rOCNC1的功能特性与天然嗅觉CNG通道之间的差异表明，天然通道可能由几种不同的亚基类型组成。在此，我们报告了另一种嗅觉CNG通道亚基（rOCNC2）的cDNA的克隆和特性分析，该亚基与rOCNC1有52%的同一性，且特异性表达于嗅觉感觉神经元中。单独在非洲爪蟾卵母细胞中表达rOCNC2不会产生可检测到的CNG电流。然而，rOCNC2与rOCNC1共表达会产生一种CNG电导，该电导与单独表达rOCNC1时检测到的电导不同，并且在几个方面更类似于天然电导，包括其对cAMP的敏感性。这表明天然嗅觉CNG通道是由rOCNC1和rOCNC2亚基组成的异源寡聚体。
