Professor Rod Devenish
+61 - 3 9905 3782
+61 - 3 9902 9500
Autophagy - eating your way out of trouble!
All eukaryotic cells degrade (or turnover) parts of their internal structure including organelles by a process called autophagy
("self eating") that occurs in a specialized compartment of cells - the vacuole (in yeast) or the lysosome (in mammals). In yeast, autophagy is mainly involved in cellular homeostasis (removal of damaged organelles) and adaptation to starvation, but in multicellular organisms (mammals) it is involved in a variety of additional processes such as programmed cell death and development of different tissue-specific functions. Alterations in the levels of autophagy are linked to a growing number of pathological conditions including neurodegenerative diseases such Parkinson's, myopathies such as cardiomyopathic Danon's disease, some forms of cancer, and infection by pathogenic bacteria or viruses.
The turnover of mitochondria, the nucleus and other organelles by autophagy presumably serves as a means of quality control for organelle function. Mechanistically distinct forms of autophagy have been identified (see Figure 1). The molecular details and regulation of these processes and how they relate to organelle turnover are now becoming better understood, but we are a long way from having complete understanding. We are using fluorescent protein technology [Devenish et al.,2008; Mijaljia et al., 2011) together with other biochemical and molecular techniques, in yeast and mammalian cells to monitor turnover. This approach is providing new insights into the complex pathways and molecular mechanisms by which organelle autophagy occurs. We have established a ‘discovery pipeline' to systematically screen a number of different yeast gene libraries and identify the molecular components and networks required for the regulation of mitophagy. For example, using our "Rosella" fluorescent biosensor in yeast (Figure 2) we have uncovered OTP1, a gene involved in an early phase autophagy of mitochondria (mitophagy). Use of yeast as an experimental model first sparked the ‘explosion' of knowledge concerning mammalian autophagic processes and continues to contribute new findings and understanding to the field.
Autophagy as a host-cell response to bacterial infection.
Successful microbial pathogens have evolved strategies to avoid or subvert autophagy thereby ensuring their survival within cells. Together with colleagues in the ARC Centre of Excellence in Structural and Functional Microbial Genomics (Ben Adler and John Boyce) we are looking at the molecular mechanisms by which the soil bacterium, Burkholderia pseudomallei achieves the avoidance or subversion of autophagy. In humans infection leads to Melioidosis, a disease endemic in tropical and subtropical areas. It is also a significant pathogen in many animals. This intracellular pathogen can escape from phagosomes into the host cytoplasm, where it replicates and infects adjacent cells. We are investigating the role played by autophagic processes in the intracellular life-cycle of B. pseudomallei in phagocytic cell lines, using confocal microscopy, intracellular survival assays and in vivo infection models. Our results (Gong et al., 2011) show that an autophagy-related pathway, LC3-associated phagocytosis (LAP) provides a defence system for macrophage cells against invading B. pseudomallei. However LAP is relatively ineffective and most bacteria escape to the cytosol where they efficiently evade capture by canonical autophagy. Presumably various bacterial proteins act as effectors that interact with host cell trafficking factor(s) and contribute to modulation of host cell biology. We are seeking to identify such proteins and their functions during infection.
Project Areas for Prospective Students
1. Autophagy of organelles, focusing on mitochondrial and nucleus turnover.
2. Autophagy in infectious disease; how autophagy can be avoided or subverted in microbial infection of mammalian cells.
3. Developing new biosensors for accelerating autophagy research.
Mijaljica, D., Prescott, M. and Devenish, R.J. Nibbling within the nucleus: turnover of nuclear contents. Cellular and Molecular Life Sciences, 64,581-588 (2007).
Nowikovsky K., Reipert S., Devenish R.J. and Schweyen R.J. Mdm38 protein depletion causes loss of mitochondrial K+/H+ exchange activity, osmotic swelling and mitophagy. Cell Death and Differentiation, 14, 1647-1656 (2007).
Rosado, C., Mijaljica, D., Hatzinisiriou, I., Prescott, M., and Devenish, R.J: Rosella - a fluorescent pH-biosensor for reporting vacuolar turnover of cytosol and organelles in yeast. Autophagy, 4, 205-213 (2008).
Cullinane, M., Gong L., Li X, Lazar-Adler N., Tra, T., Wolvetang, E., Prescott, M., Boyce, J.D., Devenish, R.J. and Adler , B. Stimulation of autophagy suppresses the intracellular survival of Burkholderia pseudomallei in mammalian cell lines. Autophagy. 4, 744-753 (2008).
Devenish, R.J., Prescott, M., Turcic, K. and Mijaljica, D. Monitoring organelle turnover in yeast using fluorescent protein tags. Methods in Enzymology, 451, 109-131 (2008)
Gong, L., Cullinane, M., Treerat, J., Ramm, G., Prescott, M., Adler, B., Boyce, J.D. and Devenish, R.J. Recruitment of LC3 to Burkholderia pseudomallei-containing phagosomes stimulates bacterial killing but bacteria that escape the phagosome are highly resistant to uptake by autophagosomes. PLoS ONE, 6(3): e17852 (2011).
Mijaljica, D., Prescott, M. and Devenish, R.J. Microautophagy in mammalian cells: revisiting a forty year old conundrum. Autophagy 7: 673-682 (2011).
Mijaljica, D., Prescott, M. and Devenish, R.J. A Fluorescence Microscopy Assay for Monitoring Mitophagy in the Yeast Saccharomyces cerevisiae. Journal of Visualised Experiments (2011) Jul 18;(53). pii: 2779. (http://www.jove.com/details.php?id=2779)
D'Cruze, T., Gong, L., Treerat, P., Ramm, G., Boyce, J.D., Prescott, M., Adler, B. and Devenish, R.J. A role for the Burkholderia pseudomallei Type Three Secretion System cluster 1 bpscN gene in virulence. Infection and Immunity 79: 3659-3664 (2011).
Mijaljica, M., Rosado, C.J., Devenish, R.J. and Prescott, M. Biosensors for Monitoring Autophagy, Biosensors - Emerging Materials and Applications, Pier Andrea Serra (Ed.), ISBN: 978-953-307-328-6, InTech, Available online from July 25 (2011): http://www.intechopen.com/articles/show/title/biosensors-for-monitoring-autophagy.
Allwood, E.M., Devenish, R.J., Prescott, M., Adler, B. and Boyce, J.D. Strategies for intracellular survival of Burkholderia pseudomallei. Frontiers in Microbiology 2:170. doi: 10.3389/fmicb.2011.00170
Devenish RJ. Autophagy and the evasion of host defense: a new variation on the theme for Burkholderia cepacia? Autophagy, 7(11), 1269-1270 (2011). Editorial.
Tra, T., Gong, L., Kao, L-P., Li, X-L., Grandela, C., Devenish, R.J., Wolvetang, E. and Prescott, M. Autophagy in human embryonic stem cells. PLoS ONE 6: e27485 (2011).