Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Small molecules enhance autophagy and reduce toxicity in Huntington's disease models

Abstract

The target of rapamycin proteins regulate various cellular processes including autophagy1, which may play a protective role in certain neurodegenerative and infectious diseases2. Here we show that a primary small-molecule screen in yeast yields novel small-molecule modulators of mammalian autophagy. We first identified new small-molecule enhancers (SMER) and inhibitors (SMIR) of the cytostatic effects of rapamycin in Saccharomyces cerevisiae. Three SMERs induced autophagy independently of rapamycin in mammalian cells, enhancing the clearance of autophagy substrates such as mutant huntingtin and A53T α-synuclein, which are associated with Huntington's disease and familial Parkinson's disease, respectively3,4,5. These SMERs, which seem to act either independently or downstream of the target of rapamycin, attenuated mutant huntingtin-fragment toxicity in Huntington's disease cell and Drosophila melanogaster models, which suggests therapeutic potential. We also screened structural analogs of these SMERs and identified additional candidate drugs that enhanced autophagy substrate clearance. Thus, we have demonstrated proof of principle for a new approach for discovery of small-molecule modulators of mammalian autophagy.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: SMERs 10, 18 and 28 enhance the clearance of mutant aggregate-prone proteins by autophagy in mammalian cell models of Huntington's and Parkinson's disease, independent of rapamycin.
Figure 2: SMERs 10, 18 and 28 induce autophagy in mammalian cells.
Figure 3: SMERs 10, 18 and 28 protect against neurodegeneration in D. melanogaster model of Huntington's disease.
Figure 4: Rapamycin and SMERs have additive protective effects on the clearance and toxicity of mutant aggregate-prone proteins.
Figure 5: Screen of chemical analogs of autophagy-inducing SMERs for their protective effects on the clearance and aggregation of mutant proteins.

References

  1. 1

    Klionsky, D.J. & Emr, S.D. Autophagy as a regulated pathway of cellular degradation. Science 290, 1717–1721 (2000).

    CAS  Article  Google Scholar 

  2. 2

    Rubinsztein, D.C., Gestwicki, J.E., Murphy, L.O. & Klionsky, D.J. Potential therapeutic applications of autophagy. Nat. Rev. Drug Discov. 6, 304–312 (2007).

    CAS  Article  Google Scholar 

  3. 3

    Ravikumar, B., Duden, R. & Rubinsztein, D.C. Aggregate-prone proteins with polyglutamine and polyalanine expansions are degraded by autophagy. Hum. Mol. Genet. 11, 1107–1117 (2002).

    CAS  Article  Google Scholar 

  4. 4

    Ravikumar, B. et al. Inhibition of mTOR induces autophagy and reduces toxicity of polyglutamine expansions in fly and mouse models of Huntington disease. Nat. Genet. 36, 585–595 (2004).

    CAS  Article  Google Scholar 

  5. 5

    Webb, J.L., Ravikumar, B., Atkins, J., Skepper, J.N. & Rubinsztein, D.C. α-synuclein is degraded by both autophagy and the proteasome. J. Biol. Chem. 278, 25009–25013 (2003).

    CAS  Article  Google Scholar 

  6. 6

    Sarkar, S. et al. Lithium induces autophagy by inhibiting inositol monophosphatase. J. Cell Biol. 170, 1101–1111 (2005).

    CAS  Article  Google Scholar 

  7. 7

    Rubinsztein, D.C. Lessons from animal models of Huntington's disease. Trends Genet. 18, 202–209 (2002).

    CAS  Article  Google Scholar 

  8. 8

    Sarkar, S., Davies, J.E., Huang, Z., Tunnacliffe, A. & Rubinsztein, D.C. Trehalose, a novel mTOR-independent autophagy enhancer, accelerates the clearance of mutant huntingtin and α-synuclein. J. Biol. Chem. 282, 5641–5652 (2007).

    CAS  Article  Google Scholar 

  9. 9

    Berger, Z. et al. Rapamycin alleviates toxicity of different aggregate-prone proteins. Hum. Mol. Genet. 15, 433–442 (2006).

    CAS  Article  Google Scholar 

  10. 10

    Gutierrez, M.G. et al. Autophagy is a defense mechanism inhibiting BCG and Mycobacterium tuberculosis survival in infected macrophages. Cell 119, 753–766 (2004).

    CAS  Article  Google Scholar 

  11. 11

    Nakagawa, I. et al. Autophagy defends cells against invading group A Streptococcus. Science 306, 1037–1040 (2004).

    CAS  Article  Google Scholar 

  12. 12

    Talloczy, Z., Virgin, H.W.T. & Levine, B. PKR-dependent autophagic degradation of herpes simplex virus type 1. Autophagy 2, 24–29 (2006).

    CAS  Article  Google Scholar 

  13. 13

    Sarbassov, D.D., Ali, S.M. & Sabatini, D.M. Growing roles for the mTOR pathway. Curr. Opin. Cell Biol. 17, 596–603 (2005).

    CAS  Article  Google Scholar 

  14. 14

    Huang, J. et al. Finding new components of the target of rapamycin (TOR) signaling network through chemical genetics and proteome chips. Proc. Natl. Acad. Sci. USA 101, 16594–16599 (2004).

    CAS  Article  Google Scholar 

  15. 15

    Mizushima, N. et al. Dissection of autophagosome formation using Apg5-deficient mouse embryonic stem cells. J. Cell Biol. 152, 657–668 (2001).

    CAS  Article  Google Scholar 

  16. 16

    Fenteany, G. et al. Inhibition of proteasome activities and subunit-specific amino-terminal threonine modification by lactacystin. Science 268, 726–731 (1995).

    CAS  Article  Google Scholar 

  17. 17

    Kabeya, Y. et al. LC3, a mammalian homologue of yeast Apg8p, is localized in autophagosome membranes after processing. EMBO J. 19, 5720–5728 (2000).

    CAS  Article  Google Scholar 

  18. 18

    Mizushima, N. Methods for monitoring autophagy. Int. J. Biochem. Cell Biol. 36, 2491–2502 (2004).

    CAS  Article  Google Scholar 

  19. 19

    Bampton, E.T.W., Goemans, C.G., Niranjan, D., Mizushima, N. & Tolkovsky, A.M. The dynamics of autophagy visualised in live cells: from autophagosome formation to fusion with endo/lysosomes. Autophagy 1, 23–36 (2005).

    CAS  Article  Google Scholar 

  20. 20

    Yamamoto, A. et al. Bafilomycin A1 prevents maturation of autophagic vacuoles by inhibiting fusion between autophagosomes and lysosomes in rat hepatoma cell line, H-4-II-E cells. Cell Struct. Funct. 23, 33–42 (1998).

    CAS  Article  Google Scholar 

  21. 21

    Ekstrom, P. & Kanje, M. Inhibition of fast axonal transport by erythro-9-[3-(2-hydroxynonyl)]adenine. J. Neurochem. 43, 1342–1345 (1984).

    CAS  Article  Google Scholar 

  22. 22

    Jackson, G.R. et al. Polyglutamine-expanded human huntingtin transgenes induce degeneration of Drosophila photoreceptor neurons. Neuron 21, 633–642 (1998).

    CAS  Article  Google Scholar 

  23. 23

    Marsh, J.L. & Thompson, L.M. Drosophila in the study of neurodegenerative disease. Neuron 52, 169–178 (2006).

    CAS  Article  Google Scholar 

  24. 24

    Schmelzle, T. & Hall, M.N. TOR, a central controller of cell growth. Cell 103, 253–262 (2000).

    CAS  Article  Google Scholar 

  25. 25

    Dantuma, N.P., Lindsten, K., Glas, R., Jellne, M. & Masucci, M.G. Short-lived green fluorescent proteins for quantifying ubiquitin/proteasome-dependent proteolysis in living cells. Nat. Biotechnol. 18, 538–543 (2000).

    CAS  Article  Google Scholar 

  26. 26

    Iwata, A., Riley, B.E., Johnston, J.A. & Kopito, R.R. HDAC6 and microtubules are required for autophagic degradation of aggregated huntingtin. J. Biol. Chem. 280, 40282–40292 (2005).

    CAS  Article  Google Scholar 

  27. 27

    Narain, Y., Wyttenbach, A., Rankin, J., Furlong, R.A. & Rubinsztein, D.C. A molecular investigation of true dominance in Huntington's disease. J. Med. Genet. 36, 739–746 (1999).

    CAS  Article  Google Scholar 

  28. 28

    Ryder, E. et al. The DrosDel collection: a set of P-element insertions for generating custom chromosomal aberrations in Drosophila melanogaster. Genetics 167, 797–813 (2004).

    CAS  Article  Google Scholar 

  29. 29

    Franceschini, N. in Information Processing in the Visual System of Drosophila (ed. Wehner, R.) 75–82 (Springer, Berlin, 1972).

    Google Scholar 

Download references

Acknowledgements

We thank T. Yoshimori (Japanese National Institute of Genetics) for the EGFP-LC3 construct, N. Mizushima (Tokyo Metropolitan Institute of Medical Science) for Atg5 and HA-Atg12 constructs, and wild-type and Atg5-deficient MEFs, A.M. Tolkovsky (University of Cambridge) for EGFP-LC3 HeLa stable cell line and N.P. Dantuma (Karolinska Institutet) for UbG76V-EGFP degron HeLa stable cell line. We thank the staff of the Broad Institute Chemical Biology Program (formerly the Institute for Chemistry and Chemical Biology), B. Ravikumar, A. Williams, L. Jahreiss and R. Walker (University of Cambridge) for technical assistance; and S. Haggarty for comments and discussion. This work was supported in part with federal funds from the US National Cancer Institute's Initiative for Chemical Genetics, National Institutes of Health, under Contract No. N01-CO-12400. We are grateful for a Wellcome Trust Senior Fellowship in Clinical Science (D.C.R.), an MRC programme grant, an EU Framework VI (EUROSCA) grant (D.C.R.) and the US National Institute of General Medicine Sciences GM38627 (S.L.S.) for additional funding. S.L.S. is an investigator at the Howard Hughes Medical Institute.

Author information

Affiliations

Authors

Contributions

S.S. and E.O.P. designed, performed and analyzed experiments and helped write the paper; S.I., S.P., A.C., R.L.M., J.A.W. and T.A.L. performed and analyzed experiments; C.J.O. designed and analyzed experiments; S.L.S. and D.C.R. designed and analyzed experiments and helped write the paper.

Corresponding authors

Correspondence to Stuart L Schreiber or David C Rubinsztein.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Fig. 1

Results of a small-molecule screen for suppressors (SMIRs) and enhancers (SMERs) of the cytostatic effects of rapamycin in yeast, and characterization, potency and selectivity of the identified SMIRs and SMERs. (PDF 185 kb)

Supplementary Fig. 2

Screen for the autophagy-inhibitory SMIRs and the autophagy-inducing SMERs in mammalian cell line. (PDF 48 kb)

Supplementary Fig. 3

The effect of SMERs 10, 18 and 28 on mTOR activity, Beclin-1/Atg6, Atg5, Atg7, Atg12, Atg5-Atg12 conjugation and proteasome activity. (PDF 59 kb)

Supplementary Methods (PDF 279 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Sarkar, S., Perlstein, E., Imarisio, S. et al. Small molecules enhance autophagy and reduce toxicity in Huntington's disease models. Nat Chem Biol 3, 331–338 (2007). https://doi.org/10.1038/nchembio883

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing