Analysis for interaction between sweet receptor and taste modifiers

Gymnemic acid （GA）和gurmarin （Gur）被认为是哺乳动物甜味反应的选择性抑制剂。为了阐明甜味抑制作用的机制，我们研究了这些抑制剂对异种表达T1r2+T1r3的HEK293细胞反应的潜在影响。结果表明，与先前在人和小鼠中的研究类似，GA和Gur抑制了表达人和小鼠T1r2+T1r3的HEK293细胞对各种甜味剂的[Ca2+]i反应，并且这些作用分别被γ-和β-CD抑制。我们检测了小鼠/人嵌合体T1r2和T1r3的反应，以确定GA和Gur的相互作用位点。我们的研究结果表明，GA的主要作用靶点是人类T1r3的跨膜区，而Gur与小鼠T1r3的氨基末端区相互作用。我们的突变分析表明，菌株对Gur特异性敏感性的分子基础取决于小鼠T1r2氨基末端区域的一个位点。在我们的模型中，GA被预测会停靠在人类T1r3跨膜区域的结合口袋上，而Gur会停靠在小鼠T1r2和T1r3的氨基末端区域上

Gymnemic acid (GA) and gurmarin (Gur) are known as selective inhibitors for sweet taste responses in mammals. To clarify the mechanisms of sweet-suppressing effects, we examined potential effects of these inhibitors on HEK293 cell responses heterologously expressed T1r2+T1r3. The results showed that similar to previous studies in humans and mice, GA and Gur inhibited the [Ca2+]i responses of HEK293 cells expressing human and mouse T1r2+T1r3 to various sweeteners and these effects were inhibited by γ- and β-CD, respectevely. We examined the responses of mouse/human chimeras of T1r2 and T1r3 to identify the interaction sites for GA and Gur. Our results suggest that the main target for GA’s action is transmembrane region of human T1r3 and Gur interacts with amino terminal region of mouse T1r3. Our mutation analysis indicate that the molecular basis for strain-specific sensitivity to Gur depends on a site within amino terminal region of mouse T1r2. In our models, GA is predicted to dock to a binding pocket within the transmembrane region of human T1r3 and Gur docks with amino terminal regions of mouse T1r2 and T1r3