Autophagy; Cell Biology; Lysosomes; Phagosomes; Protein Aggregates
Exploring how a cell consumes itself -- Macroautophagy is classically defined as a pathway for the nonspecific sequestration and degradation of cytosolic material when the cell is faced with persistent starvation. This cytosolic material is captured within a double-membraned vesicle (the autophagosome) which forms de novo and ultimately traffics the material to the lysosome for degradation (and release of valuable nutrients). However, this pathway can also be utilized as a stress response to a wide variety of specific cellular insults. The ability to capture and degrade specific cytoplasmic targets including protein aggregates, invading pathogens or even whole dysfunctional organelles forms the basis of the cell’s response to diseases ranging from neurodegeneration to cancer and heart disease. In each case, large cytoplasmic targets are identified and encapsulated newly-formed autophagosomes for delivery to the lysosome. How these targets are identified and how this organelle forms are the major foci of our laboratory.
Specialized Terms: Macroautophagy; Autophagy
Extensive Research Description
Faced with persistent starvation, the cell can “consume itself”. Macroautophagy is a pathway for the sequestration and ultimate delivery of cytosol to the lysosome for degradation and release of valuable nutrients. Interestingly, the same pathway can be highjacked to selectively dispose of cytosolic toxins ranging from protein inclusions to dying organelles, and thus macroautophagy has been linked to a range of diseases (neurodegeneration, heart disease, cancer, viral infection, etc.). However, despite this widespread translational interest, fundamental questions remain unanswered.
We are studying how the cell forms, de novo, a new organelle (the autophagosome) to sequester free cytosol. In particular, we are interested in what membranes are harvested for this purpose, how the autophagosome grows, how cargo is targeted to these membranes and how the cell carries out potentially complex membrane dynamics and intracellular fusion to effect the formation of the unique double-membrane structure of the autophagosome. Ultimately we expect that protein function and membrane architecture will be revealed by combining low resolution cell-based assays with high resolution imaging (electron cryo-microscopy) of both isolated organelles and reconstituted autophagosome mimetics, vesicles imbued with all the detail we currently possess about autophagosome proteomic character.
Lipidation of the LC3/GABARAP family of autophagy proteins relies on a membrane-curvature-sensing domain in Atg3.
Nath S, Dancourt J, Shteyn V, Puente G, Fong WM, Nag S, Bewersdorf J, Yamamoto A, Antonny B, Melia TJ. 2014. Lipidation of the LC3/GABARAP family of autophagy proteins relies on a membrane-curvature-sensing domain in Atg3. Nature Cell Biology, 16(5), p 415-424.
The Legionella effector RavZ inhibits host autophagy through irreversible Atg8 deconjugation.
Choy, A., J. Dancourt, B. Mugo, T.J. O'Connor, R.R. Isberg, T.J. Melia*, and C.R. Roy. 2012. The Legionella effector RavZ inhibits host autophagy through irreversible Atg8 deconjugation. Science, 338(6110): p. 1072-6.
SNARE proteins are required for macroautophagy.
Usha Nair, Anjali Jotwani, Jiefei Geng, Noor Gammoh, Diana Richerson, Wei-Lien Yen, Janice Griffith, Shanta Nag, Ke Wang, Tyler Moss, Fulvio Reggiori, Misuzu Baba, James A. McNew, Xuejun Jiang, Thomas J. Melia*, and Daniel J. Klionsky*. 2011. SNARE proteins are required for macroautophagy. Cell.
- Acetylation-Dependent Clearance of Soluble Mutant Huntingtin by Autophagy Jeong H., Then F., Melia, T., Mazzulli, J.R., Cui, L., Savas, J.N., Voisine, C., Tanese N., Hart A.C., Yamamoto, A. and Krainc, D. 2009. Acetylation-Dependent Clearance of Soluble Mutant Huntingtin by Autophagy. Cell 137, 60-72.
Selective activation of cognate SNAREpins by Sec1/Munc18 proteins.
Shen, J., Tareste, D.C., Paumet, F., Rothman, J.E., and Melia, T.J. 2007. Selective activation of cognate SNAREpins by Sec1/Munc18 proteins. Cell, 128, 183-195.
Full List of PubMed Publications
- Yu S, Melia TJ: The coordination of membrane fission and fusion at the end of autophagosome maturation. Curr Opin Cell Biol. 2017 Aug; 2017 Apr 29. PMID: 28463755
- Nguyen N, Shteyn V, Melia TJ: Sensing Membrane Curvature in Macroautophagy. J Mol Biol. 2017 Feb 17; 2017 Jan 11. PMID: 28088480
- Holland P, Knævelsrud H, Søreng K, Mathai BJ, Lystad AH, Pankiv S, Bjørndal GT, Schultz SW, Lobert VH, Chan RB, Zhou B, Liestøl K, Carlsson SR, Melia TJ, Di Paolo G, Simonsen A: HS1BP3 negatively regulates autophagy by modulation of phosphatidic acid levels. Nat Commun. 2016 Dec 22; 2016 Dec 22. PMID: 28004827
- Horenkamp FA, Kauffman KJ, Kohler LJ, Sherwood RK, Krueger KP, Shteyn V, Roy CR, Melia TJ, Reinisch KM: The Legionella Anti-autophagy Effector RavZ Targets the Autophagosome via PI3P- and Curvature-Sensing Motifs. Dev Cell. 2015 Sep 14; 2015 Sep 3. PMID: 26343456
- Dancourt J, Melia TJ: Lipidation of the autophagy proteins LC3 and GABARAP is a membrane-curvature dependent process. Autophagy. 2014 Aug; 2014 Jun 12. PMID: 24991828
- Nath S, Dancourt J, Shteyn V, Puente G, Fong WM, Nag S, Bewersdorf J, Yamamoto A, Antonny B, Melia TJ: Lipidation of the LC3/GABARAP family of autophagy proteins relies on a membrane-curvature-sensing domain in Atg3. Nat Cell Biol. 2014 May; 2014 Apr 20. PMID: 24747438
- Choy A, Dancourt J, Mugo B, O'Connor TJ, Isberg RR, Melia TJ, Roy CR: The Legionella effector RavZ inhibits host autophagy through irreversible Atg8 deconjugation. Science. 2012 Nov 23; 2012 Oct 25. PMID: 23112293
- Shi L, Shen QT, Kiel A, Wang J, Wang HW, Melia TJ, Rothman JE, Pincet F: SNARE proteins: one to fuse and three to keep the nascent fusion pore open. Science. 2012 Mar 16. PMID: 22422984
- Jotwani A, Richerson DN, Motta I, Julca-Zevallos O, Melia TJ: Approaches to the study of Atg8-mediated membrane dynamics in vitro. Methods Cell Biol. 2012. PMID: 22325599
- Xu Y, Melia TJ, Toomre DK: Using light to see and control membrane traffic. Curr Opin Chem Biol. 2011 Dec; 2011 Nov 10. PMID: 22079055
- Shi L, Kümmel D, Coleman J, Melia TJ, Giraudo CG: Dual roles of Munc18-1 rely on distinct binding modes of the central cavity with Stx1A and SNARE complex. Mol Biol Cell. 2011 Nov; 2011 Sep 7. PMID: 21900493
- Ji H, Coleman J, Yang R, Melia TJ, Rothman JE, Tareste D: Protein determinants of SNARE-mediated lipid mixing. Biophys J. 2010 Jul 21. PMID: 20643074
- Giraudo CG, Garcia-Diaz A, Eng WS, Chen Y, Hendrickson WA, Melia TJ, Rothman JE: Alternative zippering as an on-off switch for SNARE-mediated fusion. Science. 2009 Jan 23. PMID: 19164750