Behavioral Evidence for a Glucose Polymer Taste Receptor That Is Independent of the T1R2+3 Heterodimer in a Mouse Model
Behavioral Evidence for a Glucose Polymer Taste Receptor That Is Independent of the T1R2+3 Heterodimer in a Mouse Model
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DOI：
10.1523/jneurosci.2179-11.2011
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发表时间：
2011-09-21
影响因子：
5.3
通讯作者：
Spector, Alan C.
中科院分区：
文献类型：
--
作者：
Treesukosol, Yada;Smith, Kimberly R.;Spector, Alan C.
虽然很明显，由T1 R2和T1 R3蛋白形成的异二聚体作为甜味剂的主要味觉受体，但越来越多的证据表明，对葡萄糖聚合物的反应可能由不同的味觉受体介导。在这里，我们报告说，尽管T1 R2敲除（KO）和T1 R3敲除小鼠在短暂味觉测试的初始阶段对葡萄糖、麦芽糖和麦芽三糖的反应严重受损（5s试验，25分钟会话），它们随后随着麦芽糖和麦芽三糖浓度的变化而增加了它们的舔，这可能是由于将微弱的口头暗示与积极的摄食后结果相关联。有趣的是，即使在第一阶段，这些KO小鼠对葡萄糖聚合物混合物Polycose表现出相对正常的浓度依赖性舔体。重要的是，在T1 R2和T1 R3单KO小鼠中观察到的对糖的反应性的经验依赖性增加在T1 R2/3双KO小鼠中没有统计学显著性。然而，双KO小鼠在第一个测试阶段中仍然显示出对多糖的显著浓度依赖性反应，尽管舔率略低于WT小鼠的舔率，这可能是因为在多糖中发现的少量葡萄糖、麦芽糖和麦芽三糖增强了WT小鼠中的信号，或者因为T1 R2或T1 R3可能与另一种蛋白质异聚化以形成全功能的葡萄糖聚合物受体。这些发现提供了行为证据，葡萄糖聚合物，具有大于三个葡萄糖部分的最佳链长，刺激味觉受体的T1 R2 +3异二聚体的独立性。
Although it is clear that the heterodimer formed by the T1R2 and T1R3 proteins serves as the primary taste receptor for sweeteners, there is growing evidence that responses to glucose polymers may be mediated by a different taste receptor. Here we report that although T1R2 knockout (KO) and T1R3 KO mice displayed severely impaired responding to glucose, maltose, and maltotriose in an initial session of a brief-access taste test (5 s trials, 25 min sessions) relative to wild-type (WT) mice, they subsequently increased their licking as a function of concentration for maltose and maltotriose with continued testing, presumably due to associating weak oral cues with positive post-ingestive consequences. Interestingly, these KO mice displayed relatively normal concentration-dependent licking to Polycose, a mixture of glucose polymers, even in the first session. Importantly, the experience-dependent increase in responsiveness to the sugars observed with the T1R2 and T1R3 single KO mice was not statistically significant in the T1R2/3 double KO mice. The double KO mice, however, still displayed significant concentration-dependent responding to Polycose in the first test session, albeit lick rates were slightly lower than those seen for WT mice, perhaps because small amounts of glucose, maltose, and maltotriose found in Polycose were enhancing the signal in WT mice or because T1R2 or T1R3 can possibly heteromerize with another protein to form a fully functional glucose polymer receptor. These findings provide behavioral evidence that glucose polymers, with an optimal chain length greater than three glucose moieties, stimulate a taste receptor independent of the T1R2+3 heterodimer.