He Wei, Danilova Vicktoria, Zou Shiying, Hellekant Göran, Max Marianna, Margolskee Robert F, Damak Sami
Department of Physiology and Biophysics, Howard Hughes Medical Institute, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1677, New York, NY 10029, USA.
Chem Senses. 2002 Oct;27(8):719-27. doi: 10.1093/chemse/27.8.719.
The transduction of responses to bitter and sweet compounds utilizes guanine nucleotide binding proteins (G proteins) and their coupled receptors. Alpha-gustducin, a transducin-like G protein alpha-subunit, and rod alpha-transducin are expressed in taste receptor cells. Alpha-gustducin knockout mice have profoundly diminished behavioral and electrophysiological responses to many bitter and sweet compounds, although these mice retain residual responses to these compounds. Alpha-gustducin and rod alpha-transducin are biochemically indistinguishable in their in vitro interactions with retinal phosphodiesterase, rhodopsin and G protein betagamma-subunits. To determine if alpha-transducin can function in taste receptor cells and to compare the function of alpha-gustducin versus alpha-transducin in taste transduction in vivo, we generated transgenic mice that express alpha-transducin under the control of the alpha-gustducin promoter in the alpha-gustducin null background. Immunohistochemistry showed that the alpha-transducin transgene was expressed in about two-thirds of the alpha-gustducin lineage of taste receptor cells. Two-bottle preference tests showed that transgenic expression of rod alpha-transducin partly rescued responses to denatonium benzoate, sucrose and the artificial sweetener SC45647, but not to quinine sulfate. Gustatory nerve recordings showed a partial rescue by the transgene of the response to sucrose, SC45647 and quinine, but not to denatonium. These results demonstrate that alpha-transducin can function in taste receptor cells and transduce some taste cell responses. Our results also suggest that alpha-transducin and alpha-gustducin may differ, at least in part, in their function in these cells, although this conclusion must be qualified because of the limited fidelity of the transgene expression.
对苦味和甜味化合物的反应转导利用鸟嘌呤核苷酸结合蛋白（G蛋白）及其偶联受体。α-味导蛋白是一种类似转导蛋白的G蛋白α亚基，与视杆细胞α-转导蛋白一起在味觉受体细胞中表达。α-味导蛋白基因敲除小鼠对许多苦味和甜味化合物的行为和电生理反应显著减弱，不过这些小鼠对这些化合物仍保留残余反应。α-味导蛋白和视杆细胞α-转导蛋白在体外与视网膜磷酸二酯酶、视紫红质和G蛋白βγ亚基的相互作用在生化性质上无法区分。为了确定α-转导蛋白是否能在味觉受体细胞中发挥作用，并比较α-味导蛋白与α-转导蛋白在体内味觉转导中的功能，我们构建了在α-味导蛋白基因敲除背景下，由α-味导蛋白启动子控制表达α-转导蛋白的转基因小鼠。免疫组织化学显示，α-转导蛋白转基因在约三分之二的α-味导蛋白系味觉受体细胞中表达。双瓶偏好试验表明，视杆细胞α-转导蛋白的转基因表达部分挽救了对苯甲地那铵、蔗糖和人工甜味剂SC45647的反应，但对硫酸奎宁的反应未得到挽救。味觉神经记录显示，转基因部分挽救了对蔗糖、SC45647和奎宁的反应，但对苯甲地那铵的反应未得到挽救。这些结果表明，α-转导蛋白可以在味觉受体细胞中发挥作用并转导一些味觉细胞反应。我们的结果还表明，α-转导蛋白和α-味导蛋白在这些细胞中的功能可能至少部分存在差异，不过由于转基因表达的保真度有限，这一结论必须有所保留。
