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Siu Sylvia Lee

Publications and source records attributed to Siu Sylvia Lee.

10 recordsLinked to original sources
PubMed2006

The 14-3-3 protein FTT-2 regulates DAF-16 in Caenorhabditis elegans.

The Caenorhabditis elegans daf-2/insulin-like signaling pathway is critical for regulating development, longevity, metabolism and stress resistance. We identified the 14-3-3 protein FTT-2 to be a new regulatory component of this pathway. We found that RNAi knock down of ftt-2 specifically enhanced the daf-2-mediated dauer formation phenotype. Furthermore, ftt-2 knock down caused the nuclear accumulation of DAF-16/FOXO, the forkhead transcription factor that is the major downstream effecter of daf-2/insulin-like signaling, and enhanced the transcriptional activities of DAF-16. In contrast to ftt-2, RNAi knock down of par-5/ftt-1, the only other gene predicted to encode a 14-3-3 protein in C. elegans, did not show any notable effect on dauer formation, DAF-16 localization, or DAF-16 downstream gene transcription, underscoring the functional specification of FTT-2 and PAR-5 despite their high sequence homology. Using co-immunoprecipitation, we revealed that FTT-2 formed a complex with GFP-fused DAF-16 in C. elegans. Our results indicate that FTT-2 binds to DAF-16 in C. elegans and regulates DAF-16 by sequestering it in the cytoplasm. A similar mechanism of regulation of FOXO by 14-3-3zeta has been reported in mammalian cells, highlighting the high degree of conservation of the daf-2/insulin-like signaling pathway.

Animals↗
PubMed2006

p38 MAPK regulates expression of immune response genes and contributes to longevity in C. elegans.

The PMK-1 p38 mitogen-activated protein kinase pathway and the DAF-2-DAF-16 insulin signaling pathway control Caenorhabditis elegans intestinal innate immunity. pmk-1 loss-of-function mutants have enhanced sensitivity to pathogens, while daf-2 loss-of-function mutants have enhanced resistance to pathogens that requires upregulation of the DAF-16 transcription factor. We used genetic analysis to show that the pathogen resistance of daf-2 mutants also requires PMK-1. However, genome-wide microarray analysis indicated that there was essentially no overlap between genes positively regulated by PMK-1 and DAF-16, suggesting that they form parallel pathways to promote immunity. We found that PMK-1 controls expression of candidate secreted antimicrobials, including C-type lectins, ShK toxins, and CUB-like genes. Microarray analysis demonstrated that 25% of PMK-1 positively regulated genes are induced by Pseudomonas aeruginosa infection. Using quantitative PCR, we showed that PMK-1 regulates both basal and infection-induced expression of pathogen response genes, while DAF-16 does not. Finally, we used genetic analysis to show that PMK-1 contributes to the enhanced longevity of daf-2 mutants. We propose that the PMK-1 pathway is a specific, indispensable immunity pathway that mediates expression of secreted immune response genes, while the DAF-2-DAF-16 pathway appears to regulate immunity as part of a more general stress response. The contribution of the PMK-1 pathway to the enhanced lifespan of daf-2 mutants suggests that innate immunity is an important determinant of longevity.

Animals↗
PubMed2006

Whole genome RNAi screens for increased longevity: important new insights but not the whole story.

This article discusses the pros and cons of using RNAi screening to identify longevity genes in Caenorhabditis elegans. The discussion will focus on the results of two large-scale longevity RNAi screens that were recently published. The two screens revealed largely non-overlapping sets of candidate longevity genes. The possible reasons for such differences and their implications will be discussed.

Aging↗
PubMed2005

Interfering with longevity.

Several recent studies have highlighted how RNA interference has advanced aging-related research in Caenorhabditis elegans. Two new genome-wide RNAi-based screens together identified more than 100 new candidate longevity genes. RNAi has also greatly facilitated the functional validation of several large-scale gene expression profiling studies. Furthermore, RNAi is flexible and can be administered at different times throughout life; this feature has been exploited to analyze the temporal requirement of genes in life-span determination.

Animals↗
PubMed2005

A systematic RNAi screen for longevity genes in C. elegans.

We report here the first genome-wide functional genomic screen for longevity genes. We systematically surveyed Caenorhabditis elegans genes using large-scale RNA interference (RNAi), and found that RNAi inactivation of 89 genes extend C. elegans lifespan. Components of the daf-2/insulin-like signaling pathway are recovered, as well as genes that regulate metabolism, signal transduction, protein turnover, and gene expression. Many of these candidate longevity genes are conserved across animal phylogeny. Genetic interaction analyses with the new longevity genes indicate that some act upstream of the daf-16/FOXO transcription factor or the sir2.1 protein deacetylase, and others function independently of daf-16/FOXO and sir2.1, and might define new pathways to regulate lifespan.

Animals↗
PubMed2004

Come one, come all.

Aging is a complex process that involves the gradual functional decline of many different tissues and cells. Gene expression microarray analysis provides a comprehensive view of the gene expression signature associated with age and is particularly valuable for understanding the molecular mechanisms that contribute to the aging process. However, because of the stochastic nature of the aging process, animals of the same chronological age often manifest great physiological differences. Therefore, profiling the gene expression pattern of a large population of aging animals risks either exaggerating or masking the changes in gene expression that correspond to physiological aging. In a recent paper, Golden and Melov surveyed the gene expression profiles of individual aging Caenorhabditis elegans, hoping to circumvent the problem of variability among worms of the same chronological age. This initial analysis of age-dependent gene expression in individual aging worms is an important step toward deciphering the molecular basis of physiological aging.

Aging↗
PubMed2003

DAF-16 target genes that control C. elegans life-span and metabolism.

Signaling from the DAF-2/insulin receptor to the DAF-16/FOXO transcription factor controls longevity, metabolism, and development in disparate phyla. To identify genes that mediate the conserved biological outputs of daf-2/insulin-like signaling, we used comparative genomics to identify 17 orthologous genes from Caenorhabditis and Drosophila, each of which bears a DAF-16 binding site in the promoter region. One-third of these DAF-16 downstream candidate genes were regulated by daf-2/insulin-like signaling in C. elegans, and RNA interference inactivation of the candidates showed that many of these genes mediate distinct aspects of daf-16 function, including longevity, metabolism, and development.

Animals↗
PubMed2003

Selective PDZ protein-dependent stimulation of phosphatidylinositol 3-kinase by the adenovirus E4-ORF1 oncoprotein.

While PDZ domain-containing proteins represent cellular targets for several different viral oncoproteins, including human papillomavirus E6, human T-cell leukemia virus type 1 Tax, and human adenovirus E4-ORF1, the functional consequences for such interactions have not been elucidated. Here we report that, at the plasma membrane of cells, the adenovirus E4-ORF1 oncoprotein selectively and potently stimulates phosphatidylinositol 3-kinase (PI3K), triggering a downstream cascade of events that includes activation of both protein kinase B and p70S6-kinase. This activity of E4-ORF1 could be abrogated by overexpression of its PDZ-protein targets or by disruption of its PDZ domain-binding motif, which was shown to mediate complex formation between E4-ORF1 and PDZ proteins at the plasma membrane of cells. Furthermore, E4-ORF1 mutants unable to activate the PI3K pathway failed to transform cells in culture or to promote tumors in animals, and drugs that block either PI3K or p70S6-kinase inhibited E4-ORF1-induced transformation of cells. From these results, we propose that the transforming and tumorigenic potentials of the adenovirus E4-ORF1 oncoprotein depend on its capacity to activate PI3K through a novel PDZ protein-dependent mechanism of action.

Adenovirus E4 Proteins↗
PubMed2002

A systematic RNAi screen identifies a critical role for mitochondria in C. elegans longevity.

We report a systematic RNA interference (RNAi) screen of 5,690 Caenorhabditis elegans genes for gene inactivations that increase lifespan. We found that genes important for mitochondrial function stand out as a principal group of genes affecting C. elegans lifespan. A classical genetic screen identified a mutation in the mitochondrial leucyl-tRNA synthetase gene (lrs-2) that impaired mitochondrial function and was associated with longer-lifespan. The long-lived worms with impaired mitochondria had lower ATP content and oxygen consumption, but differential responses to free-radical and other stresses. These data suggest that the longer lifespan of C. elegans with compromised mitochrondria cannot simply be assigned to lower free radical production and suggest a more complex coupling of metabolism and longevity.

Adenosine Triphosphate↗