<b>Cholesterol taste avoidance in </b><b><i>Drosophila melanogaster</i></b>

The question as to whether animals taste cholesterol taste is not resolved. This study investigates whether the fruit fly, <i>Drosophila melanogaster</i>, is capable of detecting cholesterol through their gustatory system. We found that flies are indifferent to low levels of cholesterol and avoid higher levels. The avoidance is mediated by gustatory receptor neurons (GRNs), demonstrating that flies can taste cholesterol. The cholesterol responsive GRNs comprise a subset that also respond to bitter substances. Cholesterol detection depends on five ionotropic receptor (IR) family members, and disrupting any of these genes impairs the flies' ability to avoid cholesterol. Ectopic expressions of these IRs in GRNs reveals two classes of cholesterol receptors, each with three shared IRs and one unique subunit. Additionally, expressing cholesterol receptors in sugar-responsive GRNs confers attraction to cholesterol. This study reveals that flies can taste cholesterol, and that the detection depends on IRs in GRNs.动物能否通过味觉感知胆固醇这一科学问题尚未得到明确解答。本研究以黑腹果蝇（*Drosophila melanogaster*）为研究对象，探究其能否通过味觉系统感知胆固醇。我们发现果蝇对低浓度胆固醇无显著响应，而对高浓度胆固醇则表现出回避行为。该回避行为由味觉受体神经元（gustatory receptor neurons, GRNs）介导，这一结果证实果蝇确实能够感知胆固醇的味觉信号。响应胆固醇的味觉受体神经元存在一个亚群，该亚群同时也可被苦味物质激活。胆固醇的感知过程依赖于5种离子型受体（ionotropic receptor, IR）家族成员，敲除其中任意一种编码基因都会削弱果蝇回避胆固醇的能力。在味觉受体神经元中异位表达这些IR蛋白后，本研究鉴定出两类胆固醇受体：每一类均包含3个共享的IR亚基与1个独特的亚基。此外，若在响应糖类的味觉受体神经元中异位表达胆固醇受体，可使果蝇产生对胆固醇的趋向性。综上，本研究证实果蝇能够感知胆固醇的味觉信号，且该感知过程依赖于味觉受体神经元中的IR蛋白。