研究發(fā)現(xiàn),，蚊子通過人體呼出的二氧化碳來尋找食物來源,。一旦它們叮咬在人身上,，就可以傳染很多危險(xiǎn)的傳染性疾病，如瘧疾,、黃熱病和腦膜炎等,。

??近期的《自然》雜志上發(fā)表了美國洛克菲勒大學(xué)Leslie  Vosshall實(shí)驗(yàn)室的一項(xiàng)最新研究成果，他們發(fā)現(xiàn)了果蠅體內(nèi)的兩種二氧化碳受體分子,，是昆蟲借以感受二氧化碳的基礎(chǔ),。這一發(fā)現(xiàn)對于抵御全球性的傳染性疾病有重要的意義。

??昆蟲對二氧化碳都很敏感,，它們利用二氧化碳來尋找食物來源和評估自己的周圍環(huán)境,。研究人員早已經(jīng)發(fā)現(xiàn)了昆蟲體內(nèi)能感受二氧化碳的神經(jīng)元西細(xì)胞，但是神經(jīng)元如何感受二氧化碳的分子機(jī)制一直還不清楚,。

??研究發(fā)現(xiàn)的Gr21a蛋白,，以前被發(fā)現(xiàn)在對二氧化碳感應(yīng)神經(jīng)元細(xì)胞中表達(dá),，后者位于果蠅的觸角上。因?yàn)樵谏n蠅體內(nèi),，化學(xué)感應(yīng)受體通常是一些不相關(guān)的蛋白一起相互作用,。該研究的第一作者Walton  Jones因此從研究味覺受體家族開始，他發(fā)現(xiàn)Gr63a蛋白同Gr21a蛋白在幼蟲和成年果蠅中都是共表達(dá)存在的,。進(jìn)一步檢測瘧疾蚊子發(fā)現(xiàn)與果蠅的同源基因GPRGR22和GPRGR24,，它們也在蚊子感受二氧化碳的觸須上共表達(dá)。

??通過分子生物學(xué)操作,，Jones最終證明Gr63a蛋白同Gr21a蛋白確實(shí)是果蠅神經(jīng)元感受二氧化碳所必須的分子,。只有Gr63a同Gr21a一起表達(dá)的時(shí)候，果蠅才可能感受到二氧化碳,，將Gr63a突變后,，果蠅對高濃度的二氧化碳都沒有表現(xiàn)出正常果蠅的規(guī)避行為。

英文原文：

Identification of carbon dioxide receptors in insects may help fight infectious disease

Carbon dioxide-sensitive neurons expressing Gr21a (green) and Gr63a (red), proteins that together (white) are necessary for carbon dioxide detection. The neurons target a specific region of the fly brain, which is dedicated to processing the smell of carbon dioxide.

Mosquitoes don’t mind morning breath. They use the carbon dioxide people exhale as a way to identify a potential food source. But when they bite, they can pass on a number of dangerous infectious diseases, such as malaria, yellow fever, and West Nile encephalitis. Now, reporting in today’s advance online publication in Nature, Leslie Vosshall’s laboratory at Rockefeller University has identified the two molecular receptors in fruit flies that help these insects detect carbon dioxide. The findings could prove to be important against the fight against global infectious disease.

"Insects are especially sensitive to carbon dioxide, using it to track food sources and assess their surrounding environment," says Vosshall, Chemers Family Associate Professor and head of the Laboratory of Neurogenetics and Behavior at Rockefeller. "The neurons in insects that respond to carbon dioxide were already known, but the molecular mechanism by which these neurons sense this gas was a mystery."

One protein, called Gr21a, was previously known to be expressed in the carbon dioxide responsive neurons, which are in the antennae of the fruit fly. Since in the fly, chemosensory receptors usually work together as a pair of unrelated proteins, Walton Jones, a former biomedical fellow and first author of the paper, began by looking for other members of the gustatory receptor family, and found that the Gr63a protein was always co-expressed with Gr21a, both in the larva and in the adult fly.

"I went on to look at the malaria mosquito and found two homologues of the fly genes, GPRGR22 and GPRGR24. They are also co-expressed in the mosquito’s maxillary palp, the appendage mosquitoes use to sense carbon dioxide," says Jones.

Using genetic manipulation, Jones was able to show that both Gr21a and Gr63a are all that is needed for a fly neuron to sense carbon dioxide. He took neurons that did not normally respond to carbon dioxide and found that only if he expressed both Gr21a and Gr63a together, those neurons now became excited by the gas. He also showed that when Gr63a is mutated, the mutant flies no longer respond to the high levels of carbon dioxide that wild type flies avoid.

These molecules are the first membrane-associated proteins that have been shown to sense a gas. All previously described gas sensors have been cytoplasmic. "Though we don’t know what other proteins might be involved in the signaling pathway, the identification of the carbon dioxide receptor provides a potential target for the design of inhibitors that would act as an insect repellent, "says Vosshall. "These inhibitors would help fight global infectious disease by reducing the attraction of blood-feeding insects to humans."