A Buoyancy-Based Screen of Drosophila Larvae for Fat-Storage Mutants Reveals a Role for in Coupling Fat Storage to Nutrient Availability

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Obesity has a strong genetic component, but few of the genes that predispose to obesity are known. Genetic screens in invertebrates have the potential to identify genes and pathways that regulate the levels of stored fat, many of which are likely to be conserved in humans. To facilitate such screens, we have developed a simple buoyancy-based screening method for identifying mutant Drosophila larvae with increased levels of stored fat. Using this approach, we have identified 66 genes that when mutated increase organismal fat levels. Among these was a sirtuin family member, Sir2. Sirtuins regulate the storage and metabolism of carbohydrates and lipids by deacetylating key regulatory proteins. However, since mammalian sirtuins function in many tissues in different ways, it has been difficult to define their role in energy homeostasis accurately under normal feeding conditions. We show that knockdown of Sir2 in the larval fat body results in increased fat levels. Moreover, using genetic mosaics, we demonstrate that Sir2 restricts fat accumulation in individual cells of the fat body in a cell-autonomous manner. Consistent with this function, changes in the expression of metabolic enzymes in Sir2 mutants point to a shift away from catabolism. Surprisingly, although Sir2 is typically upregulated under conditions of starvation, Sir2 mutant larvae survive better than wild type under conditions of amino-acid starvation as long as sugars are provided. Our findings point to a Sir2-mediated pathway that activates a catabolic response to amino-acid starvation irrespective of the sugar content of the diet.

Vyšlo v časopise: A Buoyancy-Based Screen of Drosophila Larvae for Fat-Storage Mutants Reveals a Role for in Coupling Fat Storage to Nutrient Availability. PLoS Genet 6(11): e32767. doi:10.1371/journal.pgen.1001206
Kategorie: Research Article
prolekare.web.journal.doi_sk: https://doi.org/10.1371/journal.pgen.1001206

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Zdroje

1. AshrafiK

ChangFY

WattsJL

FraserAG

KamathRS

2003 Genome-wide RNAi analysis of Caenorhabditis elegans fat regulatory genes. Nature 421 268 272

2. McKayRM

McKayJP

AveryL

GraffJM

2003 C elegans: a model for exploring the genetics of fat storage. Dev Cell 4 131 142

3. GuoY

WaltherTC

RaoM

StuurmanN

GoshimaG

2008 Functional genomic screen reveals genes involved in lipid-droplet formation and utilization. Nature 453 657 661

4. PospisilikJA

SchramekD

SchnidarH

CroninSJ

NehmeNT

2010 Drosophila genome-wide obesity screen reveals hedgehog as a determinant of brown versus white adipose cell fate. Cell 140 148 160

5. DoaneWW

1960 Developmental physiology of the mutant female sterile(2)adipose of Drosophila melanogaster. I. Adult morphology, longevity, egg production, and egg lethality. J Exp Zool 145 1 21

6. SuhJM

ZeveD

McKayR

SeoJ

SaloZ

2007 Adipose is a conserved dosage-sensitive antiobesity gene. Cell Metab 6 195 207

7. GronkeS

MildnerA

FellertS

TennagelsN

PetryS

2005 Brummer lipase is an evolutionary conserved fat storage regulator in Drosophila. Cell Metab 1 323 330

8. GronkeS

BellerM

FellertS

RamakrishnanH

JackleH

2003 Control of fat storage by a Drosophila PAT domain protein. Curr Biol 13 603 606

9. HarbisonST

YamamotoAH

FanaraJJ

NorgaKK

MackayTF

2004 Quantitative trait loci affecting starvation resistance in Drosophila melanogaster. Genetics 166 1807 1823

10. LibertS

ZwienerJ

ChuX

VanvoorhiesW

RomanG

2007 Regulation of Drosophila life span by olfaction and food-derived odors. Science 315 1133 1137

11. ShirrasAD

BownesM

1989 cricklet: A locus regulating a number of adult functions of Drosophila melanogaster. Proc Natl Acad Sci U S A 86 4559 4563

12. TaniguchiCM

KondoT

SajanM

LuoJ

BronsonR

2006 Divergent regulation of hepatic glucose and lipid metabolism by phosphoinositide 3-kinase via Akt and PKClambda/zeta. Cell Metab 3 343 353

13. TeagueBD

ClarkAG

DoaneWW

1986 Developmental analysis of lipids from wild-type and adipose60 mutants of Drosophila melanogaster. J Exp Zool 240 95 104

14. SchwerB

VerdinE

2008 Conserved metabolic regulatory functions of sirtuins. Cell Metab 7 104 112

15. GuarenteL

2007 Sirtuins in aging and disease. Cold Spring Harb Symp Quant Biol 72 483 488

16. KongEC

AlloucheL

ChapotPA

VranizanK

MooreMS

Ethanol-regulated genes that contribute to ethanol sensitivity and rapid tolerance in Drosophila. Alcohol Clin Exp Res 34 302 316

17. GriswoldAJ

ChangKT

RunkoAP

KnightMA

MinKT

2008 Sir2 mediates apoptosis through JNK-dependent pathways in Drosophila. Proc Natl Acad Sci U S A 105 8673 8678

18. AstromSU

ClineTW

RineJ

2003 The Drosophila melanogaster sir2+ gene is nonessential and has only minor effects on position-effect variegation. Genetics 163 931 937

19. XieHB

GolicKG

2004 Gene deletions by ends-in targeting in Drosophila melanogaster. Genetics 168 1477 1489

20. RamadoriG

LeeCE

BookoutAL

LeeS

WilliamsKW

2008 Brain SIRT1: anatomical distribution and regulation by energy availability. J Neurosci 28 9989 9996

21. CakirI

PerelloM

LansariO

MessierNJ

VasletCA

2009 Hypothalamic Sirt1 regulates food intake in a rodent model system. PLoS ONE 4 e8322 doi:10.1371/journal.pone.0008322

22. SasakiT

KimHJ

KobayashiM

KitamuraYI

Yokota-HashimotoH

Induction of hypothalamic Sirt1 leads to cessation of feeding via agouti-related peptide. Endocrinology 151 2556 2566

23. NewmanBL

LundbladJR

ChenY

SmolikSM

2002 A Drosophila homologue of Sir2 modifies position-effect variegation but does not affect life span. Genetics 162 1675 1685

24. PurushothamA

SchugTT

XuQ

SurapureddiS

GuoX

2009 Hepatocyte-specific deletion of SIRT1 alters fatty acid metabolism and results in hepatic steatosis and inflammation. Cell Metab 9 327 338

25. ChenD

BrunoJ

EaslonE

LinSJ

ChengHL

2008 Tissue-specific regulation of SIRT1 by calorie restriction. Genes Dev 22 1753 1757

26. LombDJ

LaurentG

HaigisMC

2009 Sirtuins regulate key aspects of lipid metabolism. Biochim Biophys Acta 1804 1652 1657

27. AshaH

NagyI

KovacsG

StetsonD

AndoI

2003 Analysis of Ras-induced overproliferation in Drosophila hemocytes. Genetics 163 203 215

28. SuhJM

GaoX

McKayJ

McKayR

SaloZ

2006 Hedgehog signaling plays a conserved role in inhibiting fat formation. Cell Metab 3 25 34

29. AguilaJR

SuszkoJ

GibbsAG

HoshizakiDK

2007 The role of larval fat cells in adult Drosophila melanogaster. J Exp Biol 210 956 963

30. WalkerAK

YangF

JiangK

JiJY

WattsJL

Conserved role of SIRT1 orthologs in fasting-dependent inhibition of the lipid/cholesterol regulator SREBP. Genes Dev 24 1403 1417

31. MoynihanKA

GrimmAA

PluegerMM

Bernal-MizrachiE

FordE

2005 Increased dosage of mammalian Sir2 in pancreatic beta cells enhances glucose-stimulated insulin secretion in mice. Cell Metab 2 105 117

32. HallowsWC

LeeS

DenuJM

2006 Sirtuins deacetylate and activate mammalian acetyl-CoA synthetases. Proc Natl Acad Sci U S A 103 10230 10235

33. TulinA

NaumovaNM

MenonAK

SpradlingAC

2006 Drosophila poly(ADP-ribose) glycohydrolase mediates chromatin structure and SIR2-dependent silencing. Genetics 172 363 371

34. PalankerL

TennessenJM

LamG

ThummelCS

2009 Drosophila HNF4 regulates lipid mobilization and beta-oxidation. Cell Metab 9 228 239

35. BrittonJS

EdgarBA

1998 Environmental control of the cell cycle in Drosophila: nutrition activates mitotic and endoreplicative cells by distinct mechanisms. Development 125 2149 2158

36. PicardF

KurtevM

ChungN

Topark-NgarmA

SenawongT

2004 Sirt1 promotes fat mobilization in white adipocytes by repressing PPAR-gamma. Nature 429 771 776

37. FrescasD

ValentiL

AcciliD

2005 Nuclear trapping of the forkhead transcription factor FoxO1 via Sirt-dependent deacetylation promotes expression of glucogenetic genes. J Biol Chem 280 20589 20595

38. RodgersJT

LerinC

HaasW

GygiSP

SpiegelmanBM

2005 Nutrient control of glucose homeostasis through a complex of PGC-1alpha and SIRT1. Nature 434 113 118

39. DietzlG

ChenD

SchnorrerF

SuKC

BarinovaY

2007 A genome-wide transgenic RNAi library for conditional gene inactivation in Drosophila. Nature 448 151 156