Organelle turnover by autophagy

All eukaryotic cells turn over (degrade) parts of their internal structure, including organelles, by autophagy (?self eating?), a process that utilises a specialised compartment of cells; the vacuole in yeast and the lysosome in mammals. Defects in autophagy are increasingly being linked to pathological conditions, including neurodegenerative and muscle diseases and some forms of cancer. In addition, several studies report a role for autophagy as a mechanism for the removal of invading bacteria (e.g. Streptococcus pyogenes, Mycobacterium tuberculosis, Shigella flexneri, Listeria monocytogenes) and viruses (e.g. Epstein-Barr virus and herpes simplex virus) from mammalian cells. Organelle turnover is an essential process required for normal cellular homeostasis, growth and development. Recent studies show that organelle turnover can be a selective process involving new genes not yet fully characterised. Amongst these is OTP1, a gene specifically required for mitochondrial turnover in yeast.