Stevens D R, Seifert R, Bufe B, Müller F, Kremmer E, Gauss R, Meyerhof W, Kaupp U B, Lindemann B
Department of Physiology, Universität des Saarlandes, Homburg, Germany.
Nature. 2001 Oct 11;413(6856):631-5. doi: 10.1038/35098087.
Sour taste is initiated by protons acting at receptor proteins or channels. In vertebrates, transduction of this taste quality involves several parallel pathways. Here we examine the effects of sour stimuli on taste cells in slices of vallate papilla from rat. From a subset of cells, we identified a hyperpolarization-activated current that was enhanced by sour stimulation at the taste pore. This current resembled Ih found in neurons and cardio-myocytes, a current carried by members of the family of hyperpolarization-activated and cyclic-nucleotide-gated (HCN) channels. We show by in situ hybridization and immunohistochemistry that HCN1 and HCN4 are expressed in a subset of taste cells. By contrast, gustducin, the G-protein involved in bitter and sweet taste, is not expressed in these cells. Lowering extracellular pH causes a dose-dependent flattening of the activation curve of HCN channels and a shift in the voltage of half-maximal activation to more positive voltages. Our results indicate that HCN channels are gated by extracellular protons and may act as receptors for sour taste.
酸味是由质子作用于受体蛋白或通道引发的。在脊椎动物中，这种味觉品质的转导涉及多条平行途径。在此，我们研究了酸味刺激对大鼠轮廓乳头切片中味觉细胞的影响。从一部分细胞中，我们鉴定出一种超极化激活电流，该电流在味觉孔处受到酸味刺激时增强。这种电流类似于在神经元和心肌细胞中发现的Ih，是由超极化激活和环核苷酸门控（HCN）通道家族成员携带的电流。我们通过原位杂交和免疫组织化学表明，HCN1和HCN4在一部分味觉细胞中表达。相比之下，参与苦味和甜味的G蛋白味导素在这些细胞中不表达。降低细胞外pH值会导致HCN通道激活曲线呈剂量依赖性变平，且半数最大激活电压向更正的电压偏移。我们的结果表明，HCN通道由细胞外质子门控，可能作为酸味的受体。
