Autophagy (macroautophagy, constitutive autophagy, selective autophagy, chaperone-mediated autophagy, mitophagy) is the process of cellular breakdown of non longer required intracellular organelles or proteins. Mitophagy is specifically the breakdown of damaged mitochondria. Chaperone-mediated autophagy (CMA) is how many proteins marked for breakdown are delivered to the lysosome. Microautophagy involves direct uptake of cytoplasmic materials at the lysosome surface by invagination of the lysosome membrane. In macroautophagy, which is perhaps best characterised, some cytoplasm is engulfed by a double-membrane phagophore that expands into a cytosolic vesicle called an autophagosome, and then this autophagosome fuses with a lysosome to form an autolysosome, which degrades the macromolecules in the pinched off cytoplasm.
The formation of autophagosomes is initiated in mammalian cells primarily by the Unc51-like kinase 1 (ULK1) complex. Mammalian target of rapamycin (mTOR) complex 1 is the classic inhibitor of this. The class III phosphatidylinositol 3-kinase (PtdIns3K)/Vps34 complex can also initiate autophagy.Elongation and maturation of the autophagosomes involves two ubiquitin-like conjugation systems, the microtubule-associated protein 1 light chain 3 (LC3) system and the Atg12 system. Multiple proteins are involved
Autophagy is essential for neuron survival and dysregulation is present is several neurodegenerative disease such as Parkinsons disease where proteins, such as α-synuclein, leucine-rich repeat kinase 2, Parkin and mitochondrial serine/threonine-protein kinase PINK1 are involved in autophagy.
- ↑ Li J, Li S, Zhang L, Ouyang L, Liu B. Deconvoluting the complexity of autophagy and Parkinson's disease for potential therapeutic purpose. Oncotarget. 2015 Sep 22.(Epub ahead of print)
- ↑ Zhang H, Duan C, Yang H. Defective autophagy in Parkinson's disease: lessons from genetics. Molecular neurobiology. 2015 Feb; 51(1):89-104.(Link to article – subscription may be required.)