Zhang Y, Chou J H, Bradley J, Bargmann C I, Zinn K
Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
Proc Natl Acad Sci U S A. 1997 Oct 28;94(22):12162-7. doi: 10.1073/pnas.94.22.12162.
The nematode Caenorhabditis elegans exhibits behavioral responses to many volatile odorants. Chemotaxis toward one such odorant, diacetyl (butanedione), requires the function of a seven-transmembrane receptor protein encoded by the odr-10 gene. To determine directly whether ODR-10 protein is an odorant receptor, it is necessary to express the protein in a heterologous system and show that it responds to diacetyl by activation of a G protein signaling pathway. Here we demonstrate that human cells expressing ODR-10 on their surfaces exhibit a transient elevation in intracellular Ca2+ levels after diacetyl application. Volatile compounds that differ from diacetyl only by the addition of a methyl group (2,3-pentanedione) or the absence of a keto group (butanone) are not ODR-10 agonists. Behavioral responses to these compounds are not dependent on odr-10 function, so ODR-10 specificity in human cells resembles in vivo specificity. The apparent affinity of ODR-10 for diacetyl observed in human cells is consistent with the diacetyl concentration ranges that allow efficient nematode chemotaxis. ODR-10 expressed in human cells also responds to two anionic compounds, pyruvate and citrate, which are metabolic precursors used for diacetyl production by certain bacterial species. Ca2+ elevation in response to ODR-10 activation is due to release from intracellular stores.
线虫秀丽隐杆线虫对许多挥发性气味物质表现出行为反应。向一种这样的气味物质二乙酰（丁二酮）的趋化作用需要由odr - 10基因编码的七跨膜受体蛋白发挥功能。为了直接确定ODR - 10蛋白是否为气味受体，有必要在异源系统中表达该蛋白，并证明它通过激活G蛋白信号通路对二乙酰作出反应。在此我们证明，在其表面表达ODR - 10的人类细胞在施加二乙酰后细胞内Ca2 +水平会短暂升高。仅通过添加一个甲基（2,3 - 戊二酮）或缺少一个酮基（丁酮）而与二乙酰不同的挥发性化合物不是ODR - 10激动剂。对这些化合物的行为反应不依赖于odr - 10功能，因此人类细胞中ODR - 10的特异性类似于体内特异性。在人类细胞中观察到的ODR - 10对二乙酰的表观亲和力与允许线虫有效趋化的二乙酰浓度范围一致。在人类细胞中表达的ODR - 10也对两种阴离子化合物丙酮酸和柠檬酸盐有反应，它们是某些细菌物种用于生产二乙酰的代谢前体。响应ODR - 10激活的Ca2 +升高是由于从细胞内储存中释放。
