Essay On Autophagy

Autophagy, first described by Christian De Duve in 1956 as ‘self-eating’, is a subcellular process by which cell digests its own components within the lysosome. After decades research on autophagy, it has been defined as different subtypes. For example, microautophagy---by which cell directly engulfs cytoplasmic material into the lysosome; chaperon mediated autophagy (CMA) --- a hsc70 dependent selective pathway for autophagy; macroautophagy --- the main autophagy pathway used to degrade the obsolete organelles and aggregated proteins. Although these pathways carry different mechanisms for sequestrating and delivering substrates, the final destinations of the digestion remain the same --- lysosome. Until now, lysosome digestion has been considered as a destroy machinery for unnecessary cell constituents and recycling factory for basic metabolites, but it is now also playing an important role in maintaining cellular homeostasis and giving out signal of nutrient status by sensing the amino acid from the lysosome lumen.

With protein aggregates and superfluous organelles interior, autophagosome starts to fuse with lysosome and expose them to the hydrolases for degradation and releasing after digestion. Other than acting alone, lysosomal pathway also cooperates with other membrane dynamics such as endocytosis in which endosome carrying the cargo fuses with autophagosome and end trafficking in lysosome. All these subcellular processes and interactions build up the “autophagy-lysosome network” which keep monitoring the cellular environment and help maintaining regular cell activity. Not surprisingly, autophagy-lysosome system has been reported to be involved in many diseases including cancer, metabolic disease and neurodegenerative