Regulation of Telomere Length by Fatty Acid Elongase 3 in Yeast

Abstract

In this study, we investigated the roles of very long-chain fatty acid (VLCFA) synthesis by fatty acid elongase 3 (ELO3) in the regulation of telomere length and life span in the yeast Saccharomyces cerevisiae. Loss of VLCFA synthesis via deletion of ELO3 reduced telomere length, and reconstitution of the expression of wild type ELO3, and not by its mutant with decreased catalytic activity, rescued telomere attrition. Further experiments revealed that alterations of phytoceramide seem to be dispensable for telomere shortening in response to loss of ELO3. Interestingly, telomere shortening in elo3⌬ cells was almost completely prevented by deletion of IPK2 or KCS1, which are involved in the generation of inositol phosphates (IP4, IP5, and inositol pyrophosphates). Deletion of IPK1, which generates IP6, however, did not affect regulation of telomere length. Further data also suggested that elo3⌬ cells exhibit accelerated chronologic aging, and reduced replicative life span compared with wild type cells, and deletion of KCS1 helped recover these biological defects. Importantly, to determine downstream mechanisms, epistasis experiments were performed, and data indicated that ELO3 and YKU70/80 share a common pathway for the regulation of telomere length. More specifically, chromatin immunoprecipitation assays revealed that the telomere binding and protective function of YKu80p in vivo was reduced in elo3⌬ cells, whereas its non-homologues end-joining function was not altered. Deletion of KCS1 in elo3⌬ cells recovered the telomere binding and protective function of Ku, consistent with the role of KCS1 mutation in the rescue of telomere length attrition. Thus, these findings provide initial evidence of a possible link between Elo3-dependent VLCFA synthesis, and IP metabolism by KCS1 and IPK2 in the regulation of telomeres, which play important physiological roles in the control of senescence and aging, via a mechanism involving alterations of the telomere-binding/protection function of Ku.Very long-chain fatty acids (VLCFAs), 2 containing mainly 26 carbons in yeast, are synthesized from palmitoyl-CoA by microsomal fatty acid (FA) elongases (Elo1-3p) that catalyze the multistep chain elongation reactions (1-4). As summarized in Fig. 1A, the chain elongation, up to C24-FA, is catalyzed by both Elo2p and Elo3p, whereas elongation from C24-to C26-FA is exclusively catalyzed by Elo3p (2). Yeast sphingolipids contain predominantly C26-phytoceramide (5, 6) with hexacosanoic acid (C26-FA), which is a precursor for the synthesis of complex sphingolipids, such as inositol phosphorylceramide (IPC), mannosylinositol phosphorylceramide, and mannosyldiinositol phosphorylceramide. Null mutations of ELO3 (SUR4, YLR372W, SRE1, and VBM1), therefore, cause striking changes in the synthesis of sphingolipids and phosphatidylinositol/inositol phosphate metabolism (7-10), which are known to mediate diverse biological and signaling functions, including regulation of longevity, senescence, and telomere length (11-13).Telomeres are multifunction...

Inositol Polyphosphate Multikinase Is a Coactivator of p53-Mediated Transcription and Cell Death

“…It is the rate-limiting enzyme for the generation of higher inositol polyphosphate species such as inositol pyrophosphate (IP 7 ) (8–10), which has been shown to modulate insulin sensitivity (11), neutrophil function (12), chemotaxis and endocytosis (13, 14), and telomere maintenance (15, 16). In addition to its soluble IP 3 kinase activity, mammalian IPMK also has lipid kinase activity.…”

A Crucial Role of CXCL14 for Promoting Regulatory T Cells Activation in Stroke

“…PCCs subjected to 4-h of hypoxia were fixed with 1% formaldehyde for 20 minutes at 37˚C to allow for reversible cross-linkage57. The binding of HIF-1α to the promoter of CXCL14 (NCBI Accession number: NC_000005.9) was examined using a commercial kit for ChIP assay (Upstate Biotechnology).…”

The yeast sphingolipid signaling landscape

“…The reference lipids are: C26-alpha hydroxy phytoceramide-M(IP) 2 C (C26-αOH-M(IP) 2 C), C26-αOH-PHC, C18-DHS, C16-DHC and C16-PHC; these were used to establish the order of magnitude into which each lipid falls. Then the datasets of (Cerantola et al, 2007; Xue Li Guan, 2006) and (Klose et al, 2012) were integrated within the ceramide and sphingoid bases, and finally the datasets from (Aronova et al, 2008; Cowart and Hannun, 2007; Huang et al, 2012; Ponnusamy et al, 2008; Vionnet et al, 2010; Zhang et al, 2001) were integrated. The model data are plotted in the top of Figure 2.…”

“…However an additional clue is that the complex sphingolipid synthase csg1 Δ displayed reduced chronological lifespan in a screen for aging factors (Matecic et al, 2010), favoring ceramide over sphingoid bases in mediating the signal. Another intriguing link between sphingolipid production and aging is the involvement of the fatty acid elongase Elo3 in regulating telomere length (Askree et al, 2004; Ponnusamy et al, 2008), leading to shortened lifespan by way of a mechanism involving inositol phosphorylation. Together these phenotypes imply that a VLC ceramide regulates chronological lifespan.…”