Tissue-Specific Upregulation of Drosophila Insulin Receptor (InR) Mitigates Poly(Q)-Mediated Neurotoxicity by Restoration of Cellular Transcription Machinery
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Polyglutamine [poly(Q)] disorders are a class of trinucleotide repeat expansion neurodegenerative disorders which are dominantly inherited and progressively acquired with age. This group of disorders entail the characteristic formation of protein aggregates leading to widespread loss of neurons in different regions of the brain. SCA3 and HD, the two most commonly occurring types of poly(Q) disorders were examined in the present study. With the aim of elucidating novel genetic modifiers of poly(Q) disorders, the Drosophila insulin receptor (InR) was identified as a potential suppressor of poly(Q)-induced neurotoxicity and degeneration. We demonstrate for the first time that targeted upregulation of InR could effectively mitigate poly(Q)-mediated neurodegeneration in fly models. A significant reduction in poly(Q)-mediated cellular stress and apoptosis was noted upon InR overexpression in poly(Q) background. We further reveal that targeted upregulation of InR causes a substantial reduction in poly(Q) aggregate formation with the residual inclusion bodies localised to the cytoplasm. We also demonstrate that InR achieves suppression of poly(Q) toxicity by replenishing the cellular pool of CREB binding protein and improving the histone acetylation status of the cell. This leads to restoration of the cellular transcriptional machinery which is otherwise severely compromised in poly(Q) disease conditions. Interestingly, there also appeared a possibility of autophagy-mediated rescue of poly(Q) phenotype due to upregulation of InR. Therefore, our study strongly suggests that modulation of the insulin signalling pathway could be an effective therapeutic intervention against poly(Q) disorders.
KeywordsDrosophila Poly(Q) InR Neurodegeneration
We are thankful to J. Troy Littleton (Massachusetts Institute of Technology, USA), Hugo Stocker (Institute for Molecular Systems Biology, Switzerland), Ernst Hafen (Institute for Molecular Systems Biology, Switzerland), Justin P. Kumar (Indiana University, Bloomington, USA) and T. Lilja (Stockholm University, USA) for providing different fly stocks and some antibodies used in this study. We also thank Bloomington Stock Center, USA, for providing some fly stocks. We also thank DST-FIST(L2) support to the department. We are grateful to Ms. Nabanita Sarkar for technical support.
This work was supported by research grants (No. BT/PR15492/MED/122/46/2016) from the Department of Biotechnology (DBT), Government of India, New Delhi, India, to S.S. KR is supported by the Senior Research Fellowship (Ref. No. Schs/SRF/AA/139/F-227/2013-14) from the University Grant Commission (UGC), New Delhi, India.
- 5.Ordway JM, Tallaksen-Greene S, Gutekunst CA, Bernstein EM, Cearley JA, Wiener HW, Dure LS, Lindsey R et al (1997) Ectopically expressed CAG repeats cause intranuclear inclusions and a progressive late onset neurological phenotype in the mouse. Cell 91(6):753–763PubMedPubMedCentralCrossRefGoogle Scholar
- 6.Wellington CL, Ellerby LM, Hackam AS, Margolis RL, Trifiro MA, Singaraja R, McCutcheon K, Salvesen GS et al (1998) Caspase cleavage of gene products associated with triplet expansion disorders generates truncated fragments containing the polyglutamine tract. J Biol Chem 273(15):9158–9167CrossRefGoogle Scholar
- 10.Taylor JP, Taye AA, Campbell C, Kazemi-Esfarjani P, Fischbeck KH, Min KT (2003) Aberrant histone acetylation, altered transcription, and retinal degeneration in a Drosophila model of polyglutamine disease are rescued by CREB-binding protein. Genes Dev 17(12):1463–1468. https://doi.org/10.1101/gad.1087503 PubMedPubMedCentralCrossRefGoogle Scholar
- 12.Ravikumar B, Vacher C, Berger Z, Davies JE, Luo S, Oroz LG, Scaravilli F, Easton DF et al (2004) Inhibition of mTOR induces autophagy and reduces toxicity of polyglutamine expansions in fly and mouse models of Huntington disease. Nat Genet 36(6):585–595. https://doi.org/10.1038/ng1362 CrossRefPubMedGoogle Scholar
- 14.Johnson-Farley NN, Travkina T, Cowen DS (2006) Cumulative activation of akt and consequent inhibition of glycogen synthase kinase-3 by brain-derived neurotrophic factor and insulin-like growth factor-1 in cultured hippocampal neurons. J Pharmacol Exp Ther 316(3):1062–1069. https://doi.org/10.1124/jpet.105.094433 PubMedCrossRefGoogle Scholar
- 18.Parisi F, Riccardo S, Daniel M, Saqcena M, Kundu N, Pession A, Grifoni D, Stocker H et al (2011) Drosophila insulin and target of rapamycin (TOR) pathways regulate GSK3 beta activity to control Myc stability and determine Myc expression in vivo. BMC Biol 9:65. https://doi.org/10.1186/1741-7007-9-65 PubMedPubMedCentralCrossRefGoogle Scholar
- 34.Branco J, Al-Ramahi I, Ukani L, Perez AM, Fernandez-Funez P, Rincon-Limas D, Botas J (2008) Comparative analysis of genetic modifiers in Drosophila points to common and distinct mechanisms of pathogenesis among polyglutamine diseases. Hum Mol Genet 17(3):376–390. https://doi.org/10.1093/hmg/ddm315 PubMedCrossRefGoogle Scholar
- 38.Fahrbach SE (2006) Structure of the mushroom bodies of the insect brain. Annu Rev Entomol 51:209–232. https://doi.org/10.1146/annurev.ento.51.110104.150954 PubMedCrossRefGoogle Scholar
- 40.Chou AH, Yeh TH, Kuo YL, Kao YC, Jou MJ, Hsu CY, Tsai SR, Kakizuka A et al (2006) Polyglutamine-expanded ataxin-3 activates mitochondrial apoptotic pathway by upregulating Bax and downregulating Bcl-xL. Neurobiol Dis 21(2):333–345. https://doi.org/10.1016/j.nbd.2005.07.011 PubMedCrossRefGoogle Scholar
- 50.Labbadia J, Morimoto RI (2015) The biology of proteostasis in aging and disease. Annu Rev Biochem 84:435–464. https://doi.org/10.1146/annurev-biochem-060614-033955 PubMedPubMedCentralCrossRefGoogle Scholar
- 59.Kabeya Y, Mizushima N, Ueno T, Yamamoto A, Kirisako T, Noda T, Kominami E, Ohsumi Y et al (2000) LC3, a mammalian homologue of yeast Apg8p, is localized in autophagosome membranes after processing. EMBO J 19(21):5720–5728. https://doi.org/10.1093/emboj/19.21.5720 PubMedPubMedCentralCrossRefGoogle Scholar
- 63.Ye L, Maji S, Sanghera N, Gopalasingam P, Gorbunov E, Tarasov S, Epstein O, Klein-Seetharaman J (2017) Structure and dynamics of the insulin receptor: implications for receptor activation and drug discovery. Drug Discov Today 22:1092–1102. https://doi.org/10.1016/j.drudis.2017.04.011 PubMedCrossRefGoogle Scholar
- 72.Nucifora FC Jr, Sasaki M, Peters MF, Huang H, Cooper JK, Yamada M, Takahashi H, Tsuji S et al (2001) Interference by huntingtin and atrophin-1 with cbp-mediated transcription leading to cellular toxicity. Science 291(5512):2423–2428. https://doi.org/10.1126/science.1056784 PubMedPubMedCentralCrossRefGoogle Scholar