The ATG5 gene (Autophagy related 5 gene) is located on chromosome 6 and encodes the protein of the same name (ATG5 protein). The ATG5 protein is a key protein in the autophagic processing of the cell.
Autophagy is a process by which cells degrade and recycle damaged organelles or misfolded proteins. This "cellular waste" is disposed of when it is completely encased by a double membrane structure produced by the cell, the autophagosome. This autophagosome, along with its contents, fuses with the lysosome in a second step to form the autophagolysosome. In this cell vesicle, the delivered cellular waste is enzymatically degraded. This overall process requires concerted processing of an extensive network of proteins. One of the early steps in autophagosome assembly is the formation of a large multimeric complex called the ATG12-ATG5-ATG16 complex.
During autophagosome assembly, the autophagy protein ATG5is activated by ATG7 and forms a conglomerate with other autophagy proteins, ATG12 and ATG16L1. This complex formation is necessary for the conjugation of LC3-I (microtubule-associated proteins 1A/1B light chain 3B) and PE (phosphatidylethanolamine) to form LC3-II (LC3-phosphatidylethanolamine conjugate). The autophagy protein ATG5 may also act as a pro-apoptotic molecule targeting mitochondria.
At low levels of DNA damage, ATG5 can translocate to the nucleus and interact with survivin. Survivin is a so-called "multitasking protein" that plays a dual role in promoting cell proliferation and further in inhibiting apoptosis. ATG5 is further known to be regulated by various stress-induced transcription factors and protein kinases. Phosphorylation by various kinases is necessary to achieve its active conformation. ATG5 may also be regulated post-translationally by microRNA.