title: Reduction of DILP2 in Drosophila triages a metabolic phenotype from lifespan revealing redundancy and compensation among DILPs.
abstract: The insulin/IGF-like signalling (IIS) pathway has diverse functions in all multicellular organisms, including determination of lifespan. The seven insulin-like peptides (DILPs) in Drosophila are expressed in a stage- and tissue-specific manner. Partial ablation of the median neurosecretory cells (mNSCs) in the brain, which produce three DILPs, extends lifespan, reduces fecundity, alters lipid and carbohydrate metabolism and increases oxidative stress resistance. To determine if reduced expression of DILPs is causal in these effects, and to investigate possible functional diversification and redundancy between DILPs, we used RNA interference to lower specifically the transcript and protein levels of dilp2, the most highly expressed of the mNSC-derived DILPs. We found that DILP2 was limiting only for the increased whole-body trehalose content associated with mNSC-ablation. We observed a compensatory increase in dilp3 and 5 mRNA upon dilp2 knock down. By manipulation of dfoxo and dInR, we showed that the increase in dilp3 is regulated via autocrine insulin signaling in the mNSCs. Our study demonstrates that, despite the correlation between reduced dilp2 mRNA levels and lifespan-extension often observed, DILP2 reduction is not sufficient to extend lifespan. Nor is the increased trehalose storage associated with reduced IIS sufficient to extend lifespan. To understand the normal regulation of expression of the dilps and any functional diversification between them will require independent control of the expression of different dilps.
authors.affiliation: UCL Institute of Healthy Ageing, GEE, University College London, London, UK.
authors.forename: Susan
authors.initials: S
authors.lastname: Broughton
authors.forename: Nazif
authors.initials: N
authors.lastname: Alic
authors.forename: Cathy
authors.initials: C
authors.lastname: Slack
authors.forename: Timothy
authors.initials: T
authors.lastname: Bass
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Ikeya
authors.forename: Giovanna
authors.initials: G
authors.lastname: Vinti
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Tommasi
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Driege
authors.forename: Ernst
authors.initials: E
authors.lastname: Hafen
authors.forename: Linda
authors.initials: L
authors.lastname: Partridge
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006003:Glycogen / Q000378:metabolism; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D008136:Longevity / Q000235:genetics*; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D010641:Phenotype; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D014199:Trehalose / Q000097:blood
chemical_list: C111892:DIAP2 protein, Drosophila; D029721:Drosophila Proteins; D051034:Inhibitor of Apoptosis Proteins; D012333:RNA, Messenger; D006003:Glycogen; D014199:Trehalose