Molecular mechanism of Caenorhabditis elegans insulin-like peptides that regulate diapause and longevity positively or negatively

为了应对不利的生长条件，线虫秀丽隐杆线虫停止发育并进入滞育阶段。秀丽隐杆线虫利用滞育诱导信息素作为化学介质来检测种群过剩。秀丽隐杆线虫胰岛素/胰岛素样生长因子-I信号通路（insulin/insulin-like growth factor-I signaling，IIS）不仅通过受体β-2调控幼虫滞育，还调控成虫寿命。最近，据报道，ins-7 RNAi敲低导致寿命延长。在我们之前的研究中，我们鉴定了胰岛素样基因ins-17和ins-18，并破坏它们以阐明它们的生理功能。在上述信息素的存在下，这些基因破坏引起幼虫滞育的显着减少。相比之下，干扰对寿命的影响一直是模糊的。在上述背景下，我们试图表征滞育诱导信息素。此外，我们还阐明了这些胰岛素样基因在滞育诱导中的生理功能。 ...更多信息 我们首先对滞育诱导信息素进行了化学和生物学表征。我们尝试了包括HPLC在内的几种色谱方法来纯化信息素。虽然提纯尚未完成，但信息素似乎是一种中性或碱性化合物，分子量约为1，000。非常有趣的是，粗糙的信息素以剂量依赖的方式延长了寿命。此外，寿命的延长依赖于转录因子INS-2下游的INS-16，这表明信息素通过IIS途径调节成年人的寿命。接下来，我们破坏了胰岛素样基因ins-7和ins-11。正如预期的那样，缺乏ins-7的突变动物显示出延长的寿命。该动物还发现，在信息素的存在下，幼虫滞育增加。相反，ins-11基因的破坏对幼虫滞育和成虫寿命没有影响。然后，为了阐明ins基因的冗余功能，我们将基因破坏的动物杂交。ins-11、ins-17和ins-18基因的缺失抑制了ins-7基因引起的幼虫滞育，表明ins-11、ins-17和ins-18基因具有与ins-7相反的功能。而且，只有ins-18的破坏取消了ins-7引起的寿命延长，表明只有ins-18在寿命调节中具有与ins-7相反的功能。简而言之，INS-7作为受体INS-2的激动剂发挥作用，INS-11、INS-17和INS-18作为幼虫滞育的拮抗剂发挥作用。另一方面，就成年寿命而言，只有INS-18作为α-2的拮抗剂起作用。少

In a response to unfavorable growth conditions, the nematode Caenorhabditis elegans ceases development and enters a diapause stage. C.elegans utilizes the diapause-inducing pheromone as a chemical mediator to detect overpopulation. The insulin/insulin-like growth factor-I signaling (IIS) pathway of C.elegans regulates not only larval diapause but also adult lifespan via the receptor DAF-2. Recently, it was reported that ins-7 RNAi knockdown causes an extended lifespan. In our previous study, we identified insulin-like genes ins-17 and ins-18 and disrupted them to elucidate their physiological functions. In the presence of the pheromone described above, these gene-disruptions caused a significant decrease in larval diapause. In contrast, effect of the disruptions on lifespan has been ambiguous. Under the background described above, we attempted to characterize the diapause-inducing pheromone. In addition, we elucidated physiological functions of these insulin-like genes in diapause-indu … More cing and lifespan-extending conditions.We first characterized the diapause-inducing pheromone chemically and biologically. We tried purifying the pheromone with several chromatographic methods including HPLC. Although the purification has not yet completed, the pheromone seems a neutral or basic compound of which molecular weight is around 1,000. Quite interestingly, the crude pheromone caused an extended lifespan in a dose-dependent manner. In addition, the lifespan extension depended on the transcription factor DAF-16 downstream of DAF-2, suggesting that the pheromone regulates adult lifespan via the IIS pathway.Next, we disrupted insulin-like genes ins-7 and ins-11. As expected, the mutant animal lacking ins-7 showed an extended lifespan. The animal also revealed an increase in larval diapause in the presence of the pheromone. In contract, the gene-disruption of ins-11 showed no influence in larval diapause and adult lifespan. Then in order to elucidate redundant function of ins genes, we crossed the gene-disrupted animals. Disruption of ins-11, ins-17, or ins-18 suppressed the larval diapause caused by that of ins-7, indicating that ins-11, -17, and -18 genes have an opposite function to ins-7. Moreover, only disruption of ins-18 canceled the lifespan extension caused by that of ins-7, indicating that only ins-18 has an opposite function to ins-7 in lifespan regulation. In short, INS-7 functions as an agonist to the receptor DAF-2, and INS-11, -17, and -18 function as an antagonist in terms of larval diapause. On the other hand, only INS-18 functions as an antagonist to DAF-2 in terms of adult lifespan. Less