Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2011;6(6):e20850. doi: 10.1371/journal.pone.0020850. Epub 2011 Jun 13.
The protein L-isoaspartyl-O-methyltransferase functions to initiate the repair of isomerized aspartyl and asparaginyl residues that spontaneously accumulate with age in a variety of organisms. Caenorhabditis elegans nematodes lacking the pcm-1 gene encoding this enzyme display a normal lifespan and phenotype under standard laboratory growth conditions. However, significant defects in development, egg laying, dauer survival, and autophagy have been observed in pcm-1 mutant nematodes when deprived of food and when exposed to oxidative stress. Interestingly, overexpression of this repair enzyme in both Drosophila and C. elegans extends adult lifespan under thermal stress. In this work, we show the involvement of the insulin/insulin-like growth factor-1 signaling (IIS) pathway in PCM-1-dependent lifespan extension in C. elegans. We demonstrate that reducing the levels of the DAF-16 downstream transcriptional effector of the IIS pathway by RNA interference reduces the lifespan extension resulting from PCM-1 overexpression. Using quantitative real-time PCR analysis, we show the up-regulation of DAF-16-dependent stress response genes in the PCM-1 overexpressor animals compared to wild-type and pcm-1 mutant nematodes under mild thermal stress conditions. Additionally, similar to other long-lived C. elegans mutants in the IIS pathway, including daf-2 and age-1 mutants, PCM-1 overexpressor adult animals display increased resistance to severe thermal stress, whereas pcm-1 mutant animals survive less long under these conditions. Although we observe a higher accumulation of damaged proteins in pcm-1 mutant nematodes, the basal level of isoaspartyl residues detected in wild-type animals was not reduced by PCM-1 overexpression. Our results support a signaling role for the protein L-isoaspartyl methyltransferase in lifespan extension that involves the IIS pathway, but that may be independent of its function in overall protein repair.
蛋白 L-异天冬氨酰-O-甲基转移酶的功能是启动修复在各种生物体中随年龄增长而自发积累的异构化天冬氨酸和天冬酰胺残基。缺乏编码该酶的 pcm-1 基因的秀丽隐杆线虫显示出在标准实验室生长条件下正常的寿命和表型。然而，在缺乏食物和暴露于氧化应激时，pcm-1 突变线虫在发育、产卵、 dauer 存活和自噬方面表现出显著缺陷。有趣的是，在果蝇和秀丽隐杆线虫中过度表达这种修复酶可以在热应激下延长成年寿命。在这项工作中，我们表明胰岛素/胰岛素样生长因子-1 信号通路（IIS）参与了 pcm-1 依赖的秀丽隐杆线虫寿命延长。我们证明，通过 RNA 干扰降低 IIS 通路下游的 DAF-16 转录效应物的水平会降低 pcm-1 过表达导致的寿命延长。使用定量实时 PCR 分析，我们显示在温和热应激条件下，与野生型和 pcm-1 突变线虫相比，pcm-1 过表达动物中 DAF-16 依赖性应激反应基因的上调。此外，与 IIS 通路中的其他长寿秀丽隐杆线虫突变体（包括 daf-2 和 age-1 突变体）类似，pcm-1 过表达的成年动物对严重热应激的抵抗力增强，而 pcm-1 突变体动物在这些条件下的存活时间较短。尽管我们观察到 pcm-1 突变线虫中受损蛋白的积累更高，但在野生型动物中，pcm-1 过表达并没有降低检测到的异天冬氨酸残基的基础水平。我们的结果支持蛋白 L-异天冬氨酰甲基转移酶在寿命延长中的信号作用，该作用涉及 IIS 通路，但可能与其在整体蛋白修复中的功能无关。
