Publisher Correction: Enhanced β-adrenergic signalling underlies an age-dependent beneficial metabolic effect of PI3K p110α inactivation in adipose tissue.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Publisher Correction: Enhanced β-adrenergic signalling underlies an age-dependent beneficial metabolic effect of PI3K p110α inactivation in adipose tissue.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

DAF-16/FoxO directly regulates an atypical AMP-activated protein kinase gamma isoform to mediate the effects of insulin/IGF-1 signaling on aging in Caenorhabditis elegans

The DAF-16/FoxO transcription factor controls growth, metabolism and aging in Caenorhabditis elegans. The large number of genes that it regulates has been an obstacle to understanding its function. However, recent analysis of transcript and chromatin profiling implies that DAF-16 regulates relatively few genes directly, and that many of these encode other regulatory proteins. We have investigated the regulation by DAF-16 of genes encoding the AMP-activated protein kinase (AMPK), which has ?, ? and ? subunits. C. elegans has 5 genes encoding putative AMP-binding regulatory ? subunits, aakg-1-5. aakg-4 and aakg-5 are closely related, atypical isoforms, with orthologs throughout the Chromadorea class of nematodes. We report that ?75% of total ? subunit mRNA encodes these 2 divergent isoforms, which lack consensus AMP-binding residues, suggesting AMP-independent kinase activity. DAF-16 directly activates expression of aakg-4, reduction of which suppresses longevity in daf-2 insulin/IGF-1 receptor mutants. This implies that an increase in the activity of AMPK containing the AAKG-4 ? subunit caused by direct activation by DAF-16 slows aging in daf-2 mutants. Knock down of aakg-4 expression caused a transient decrease in activation of expression in multiple DAF-16 target genes. This, taken together with previous evidence that AMPK promotes DAF-16 activity, implies the action of these two metabolic regulators in a positive feedback loop that accelerates the induction of DAF-16 target gene expression. The AMPK ? subunit, aakb-1, also proved to be up-regulated by DAF-16, but had no effect on lifespan. These findings reveal key features of the architecture of the gene-regulatory network centered on DAF-16, and raise the possibility that activation of AMP-independent AMPK in nutritionally replete daf-2 mutant adults slows aging in C. elegans. Evidence of activation of AMPK subunits in mammals suggests that such FoxO-AMPK interactions may be evolutionarily conserved

Ecologie de la bactérie Pseudomonas syringae dans les biofilms épilithiques

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<i>aakg-4</i> transcription is directly regulated by DAF-16/FoxO.

<p><b>A, B</b>) <i>aakg-4</i> but not <i>aakg-5</i> mRNA levels are increased in <i>daf-2</i> animals in a <i>daf-16</i> dependent manner. ^♦<i>p</i><0.05, compared to N2, *<i>p</i><0.05, compared to <i>daf-2</i>. Mean values from 4 trials. Error bars, standard deviation. <b>C</b>) DAF-16 binds to the promoter of <i>aakg-4</i> but not <i>aakg-5</i>. <i>aakg-4</i> peak 2 is positioned within 1 Kb of the transcriptional start site and contains two DAF-16 binding elements (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004109#pgen.1004109.s005" target="_blank">Figure S5</a>). One representative experiment is shown which contained 3 immuno-precipitation replicates from the same chromatin preparation (error bars show the standard deviation between them). The horizontal dotted line shows the % input from a negative control region (3′ of gene R11A5.4) that does not bind DAF-16 <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004109#pgen.1004109-Schuster1" target="_blank">[22]</a>. Statistical analysis of additional trials is presented in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004109#pgen.1004109.s021" target="_blank">Table S5</a>. A western blot showing the specificity of the DAF-16 antibody is shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004109#pgen.1004109.s004" target="_blank">Figure S4</a>. <b>D</b>) Confocal microscopy shows <i>Paakg-4::gfp</i> to be broadly expressed in <i>C. elegans</i>. Images show <i>Paakg-4::gfp</i> expression pattern in 1 day old hermaphrodites. (<b>i</b>) Whole worm expression pattern. (<b>ii</b>) <i>Paakg-4::gfp</i> is seen in tail sensory organs: phasmid sheath (PhaSh), socket cells (PhaSc) and neurons (PhaN), as well as in epithelial rectal cells (RectE), anal-depressor muscle (ADM), pre-anal ganglion rectal neurons (RectN), body wall muscles (BWM), posterior intestine (Int) and dorsal cord neuronal processes (DC). (<b>iii</b>) <i>Paakg-4::gfp</i> is expressed in vulval (VlvM), uterine muscles (UtM) and ventral cord processes (VC). (<b>iv</b>) Head expression mostly localizes to the ring ganglia (RingN) plus 6 pharyngeal neurons (PhxN). (<b>v</b>) It is also seen in amphid sensory organs including sheath (AmphSh), socket cells (AmphSc) and neurons (AmphN). <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004109#pgen.1004109.s026" target="_blank">Table S10</a> compares expression of <i>Paakg-4::gfp</i> with other AMPK subunits. <b>E</b>) Quantification of GFP fluorescence in worms expressing the <i>Paakg-4::gfp</i> reporter shows that fluorescence increased in <i>daf-2</i> animals dependent on <i>daf-16</i>. The same was also true for a second set of strains generated from a different extrachromosomal array. Means from 3 independent trials shown. Error bars, standard error. Animals contained the <i>wuEx256</i> transgene array. ^♦<i>p</i><0.01 compared to N2, *<i>p</i><0.001 compared to <i>daf-2</i>. <b>F</b>) <i>gfp</i> mRNA was increased in <i>daf-2</i> animals in a <i>daf-16</i>-dependent fashion. ^♦<i>p</i><0.05 compared to N2, *<i>p</i><0.01 compared to <i>daf-2</i>. Means from 3 independent trials shown. Error bars, standard deviation. Prior to transgene quantification animals were maintained at 15°C and then shifted to 25°C for 24 hr at the L4 stage.</p

Anthranilate fluorescence marks a calcium-propagated necrotic wave that promotes organismal death in C. elegans

For cells the passage from life to death can involve a regulated, programmed transition. In contrast to cell death, the mechanisms of systemic collapse underlying organismal death remain poorly understood. Here we present evidence of a cascade of cell death involving the calpain-cathepsin necrosis pathway that can drive organismal death in Caenorhabditis elegans. We report that organismal death is accompanied by a burst of intense blue fluorescence, generated within intestinal cells by the necrotic cell death pathway. Such death fluorescence marks an anterior to posterior wave of intestinal cell death that is accompanied by cytosolic acidosis. This wave is propagated via the innexin INX-16, likely by calcium influx. Notably, inhibition of systemic necrosis can delay stress-induced death. We also identify the source of the blue fluorescence, initially present in intestinal lysosome-related organelles (gut granules), as anthranilic acid glucosyl esters--not, as previously surmised, the damage product lipofuscin. Anthranilic acid is derived from tryptophan by action of the kynurenine pathway. These findings reveal a central mechanism of organismal death in C. elegans that is related to necrotic propagation in mammals--e.g., in excitotoxicity and ischemia-induced neurodegeneration. Endogenous anthranilate fluorescence renders visible the spatio-temporal dynamics of C. elegans organismal death