Stress granules (SGs) are nonmembranous organelles that are dynamically assembled and disassembled in response to various stressors. Under stressed conditions, polyadenylated mRNAs and translation factors are sequestrated in SGs to promote global repression of protein synthesis. It has been previously demonstrated that SG formation enhances cell survival and stress resistance. However, the physiological role of SGs in organismal aging and longevity regulation remains unclear. In this study, we used TIAR‐1::GFP and GTBP‐1::GFP as markers to monitor the formation of SGs in Caenorhabditis elegans. We found that, in addition to acute heat stress, SG formation could also be triggered by dietary changes, such as starvation and dietary restriction (DR). We found that HSF‐1 is required for the SG formation in response to acute heat shock and starvation but not DR, whereas the AMPK‐eEF2K signaling is required for starvation and DR‐induced SG formation but not heat shock. Moreover, our data suggest that this AMPK‐eEF2K pathway‐mediated SG formation is required for lifespan extension by DR, but dispensable for the longevity by reduced insulin/IGF‐1 signaling. Collectively, our findings unveil a novel role of SG formation in DR‐induced longevity.

The nematode Caenorhabditis elegans has emerged as a popular model system for studying the regulation of lipid metabolism. Therefore, it is critical to develop a method for determining fat storage in individual worms. Oil Red O (ORO) staining has been validated as an accurate assessment for major fat storage in C. elegans. Here, we describe an optimized protocol for ORO staining of C. elegans and provide detailed instructions for quantifying the intensity of ORO signal in images acquired by light microscopy., [摘要]线虫秀丽隐杆线虫已成为研究脂质代谢调控的流行模型系统。因此，重要的是开发一种方法用于determin荷兰国际集团在个别蠕虫脂肪储存。油红 O (ORO) 染色已被验证为对秀丽隐杆线虫中主要脂肪储存的准确评估。在这里，我们描述了一种优化的线虫ORO 染色方案，并提供了量化光学显微镜图像中 ORO 信号强度的详细说明。[背景]最近，人们对研究脂质代谢和能量稳态之间的相互作用越来越感兴趣。秀丽隐杆线虫已被证明是一个强大的遗传系统，用于阐明复杂的生理机制和识别新的遗传途径。脂质代谢是真核生物中高度保守的过程。脂代谢途径的许多哺乳动物基因在秀丽隐杆线虫中的功能相似（Ashrafi ，2007；Jones and Ashrafi ，2009）。此外，已经在哺乳动物系统中证实了在线虫中鉴定的几种脂质调节途径（McKay等人，2003 年；Suh等人，2007 年）。上述特征使秀丽隐杆线虫成为研究脂肪积累和分布调节的绝佳动物模型。要了解调节脂肪代谢的分子机制，需要对蠕虫中的脂肪积累水平进行精确评估。各种方法已被应用于可视化和测量秀丽隐杆线虫中的脂肪含量（Yen等人，2010 年；Barros等人，2012 年）。其中，固定蠕虫的油红 O (ORO)染色已被证明是评估线虫脂肪储存的准确方法（O'Rourke等，2009；Zhang等，2010）。ORO 是一种脂溶性二唑染料，可检测中性脂质和胆固醇酯，但不能检测生物膜（Ramirez-Zacarias等，1992）。在这里，我们展示了多聚甲醛固定的 ORO 染色协议。该方法很容易应用，因为它只需要标准的实验室和计算机设备。作为应用程序的一个示例，我们包含了野生型 N2、daf-2(e1370)突变体和eat-2(ad 1 116)突变体中脂肪含量的可视化和量化数据。

Heat shock factor–1 (HSF-1) is a master regulator of stress responses across taxa. Overexpression of HSF-1 or genetic ablation of its conserved negative regulator, heat shock factor binding protein 1 (HSB-1), results in robust life-span extension in Caenorhabditis elegans. Here, we found that increased HSF-1 activity elevates histone H4 levels in somatic tissues during development, while knockdown of H4 completely suppresses HSF-1–mediated longevity. Moreover, overexpression of H4 is sufficient to extend life span. Ablation of HSB-1 induces an H4-dependent increase in micrococcal nuclease protection of both nuclear chromatin and mitochondrial DNA (mtDNA), which consequently results in reduced transcription of mtDNA-encoded complex IV genes, decreased respiratory capacity, and a mitochondrial unfolded protein response–dependent life-span extension. Collectively, our findings reveal a previously unknown role of HSB-1/HSF-1 signaling in modulation of mitochondrial function via mediating histone H4-dependent regulation of mtDNA gene expression and concomitantly acting as a determinant of organismal longevity.

Dietary restriction (DR) is known to promote autophagy to exert its longevity effect. While SAMS-1 (S-adenosyl methionine synthetase-1) has been shown to be a key mediator of the DR response, little is known about the roles of S-adenosyl methionine (SAM) and SAM-dependent methyltransferase in autophagy and DR-induced longevity. In this study, we show that DR and SAMS-1 repress the activity of SET-2, a histone H3K4 methyltransferase, by limiting the availability of SAM. Consequently, the reduced H3K4me3 levels promote the expression and activity of two transcription factors, HLH-30/TFEB and PHA-4/FOXA, which both regulate the transcription of autophagy-related genes. We then find that HLH-30/TFEB and PHA-4/FOXA act collaboratively on their common target genes to mediate the transcriptional response of autophagy-related genes and consequently the lifespan of the animals. Our study thus shows that the SAMS-1-SET-2 axis serves as a nutrient-sensing module to epigenetically coordinate the activation of HLH-30/TFEB and PHA-4/FOXA transcription factors to control macroautophagy/autophagy and longevity in response to DR.

Aging is the dominant risk factor for most chronic diseases. Development of antiaging interventions offers the promise of preventing many such illnesses simultaneously. Cellular stress resistance is an evolutionarily conserved feature of longevity. Here, we identify compounds that induced resistance to the superoxide generator paraquat (PQ), the heavy metal cadmium (Cd), and the DNA alkylator methyl methanesulfonate (MMS). Some rescue compounds conferred resistance to a single stressor, while others provoked multiplex resistance. Induction of stress resistance in fibroblasts was predictive of longevity extension in a published large-scale longevity screen in Caenorhabditis elegans, although not in testing performed in worms and flies with a more restricted set of compounds. Transcriptomic analysis and genetic studies implicated Nrf2/SKN-1 signaling in stress resistance provided by two protective compounds, cardamonin and AEG 3482. Small molecules identified in this work may represent attractive tools to elucidate mechanisms of stress resistance in mammalian cells.

S‐adenosylmethionine (SAM), generated from methionine and ATP by S‐adenosyl methionine synthetase (SAMS), is the universal methyl group donor required for numerous cellular methylation reactions. In Caenorhabditis elegans , silencing sams‐1 , the major isoform of SAMS, genetically or via dietary restriction induces a robust mitochondrial unfolded protein response (UPR ^mt ) and lifespan extension. In this study, we found that depleting SAMS‐1 markedly decreases mitochondrial SAM levels. Moreover, RNAi knockdown of SLC‐25A26, a carrier protein responsible for transporting SAM from the cytoplasm into the mitochondria, significantly lowers the mitochondrial SAM levels and activates UPR ^mt , suggesting that the UPR ^mt induced by sams‐1 mutations might result from disrupted mitochondrial SAM homeostasis. Through a genetic screen, we then identified a putative mitochondrial tRNA methyltransferase TRMT‐10C.2 as a major downstream effector of SAMS‐1 to regulate UPR ^mt and longevity. As disruption of mitochondrial tRNA methylation likely leads to impaired mitochondrial tRNA maturation and consequently reduced mitochondrial translation, our findings suggest that depleting mitochondrial SAM level might trigger UPR ^mt via attenuating protein translation in the mitochondria. Together, this study has revealed a potential mechanism by which SAMS‐1 regulates UPR ^mt and longevity.