ATG16L1 | |||||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||||||||||||||||||||||||
Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
Aliases | ATG16L1 , autophagy related 16-like 1 (S. cerevisiae), APG16L, ATG16A, ATG16L, IBD10, WDR30, autophagy related 16 like 1 | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 610767 MGI: 1924290 HomoloGene: 41786 GeneCards: ATG16L1 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
|
Autophagy related 16 like 1 is a protein that in humans is encoded by the ATG16L1 gene. [5] This protein is characterized as a subunit of the autophagy-related ATG12- ATG5/ATG16 complex and is essentially important for the LC3 (ATG8) lipidation and autophagosome formation. This complex localizes to the membrane and is released just before or after autophagosome completion. [6]
Furthermore, ATG16L1 appears to have other autophagy-independent functions, e.g., intracellular membrane trafficking regulation and inflammation. [6] Autophagy in general plays a crucial role in pathways leading to innate and adaptive immunity activation. [7] That is why many autophagy-related proteins, including ATG16L1, their gene expression and its role in autoimmune diseases are studied in-depth nowadays.[ when? ]
Autophagy is the major intracellular degradation system delivering cytoplasmic components to lysosomes, and it accounts for degradation of most long-lived proteins and some organelles. Cytoplasmic constituents, including organelles, are sequestered into double-membraned autophagosomes, which subsequently fuse with lysosomes. ATG16L1 is a component of a large protein complex essential for autophagy. [8] [9] Several proteins which interact with ATG16L have been identified to reveal its function. It appears that ATGL16L has an important role not only in autophagy but also in xenophagy for example during a bacterial infection, in antigen presentation in human B cells, plasma membrane repair in mouse embryonic fibroblasts, hormone secretion and in alcohol-induced sedation response in Drosophila . [10]
ATG16L1 protein consists of three main domains - N-terminal region which contains an alpha-helix required for binding to ATG5 ubiquitin-folds, a middle region (coiled-coil domain, CCD), and a domain made of seven WD40 repeats, that forms a β-propeller, found in its C-terminal part. Polymorphisms and mutations in these domains are considered to be associated with several diseases. [11]
Due to present models, ATG16L1 is supposed to exist in ~800 kDa complexes which contain ATG12-ATG5 and several ATG16L1 dimers. These dimers are composed mostly of a CCD region of the protein and ATG5 binding site. The middle region is considered to be essential for the ATG16L1 function. Mice with CCD deletions exhibited phenotypic abnormalities as well as neonatal fatality, though non of these were observed in WD40 region deletion phenotype. Surprisingly, overexpression of CCD, as well as deletion, leads to an inhibition of autophagosome formation. [11]
ATG16L1 is expressed in the colon, intestinal cells, leukocytes and spleen. Recent studies have shown that mutations in the ATG16L1 gene may be linked to Crohn's disease. [12] [13] [14] A coding polymorphism in ATG16L1 gene is considered to be a risk factor for Crohn's disease development as well as ATG16L2. ATG16L1 appears to be an essential protein for the function of intestinal stem cells, morphological structure of intestinal cells and granule exocytosis pathway of the Paneth cells in animal models. [10]
Bacteria invasion leads to ATG16L1 recruiting by NOD1 and NOD2. This results in autophagy in RIP2/NF-κB independent manner. It is also known that NOD2 interacts with ATG16L, ATG5 and ATG7 and provides antibacterial immune response through autophagy induction and MHC class II antigen-specific CD4+ T cell responses. [15] It has also been shown that low levels of ATG16L1 result in lower ATG16L1-NOD2 complex formation, which is crucial for bacterial autophagy in the bacterial entry site. Inhibition of autophagy leads to a NOD2 signaling through RIP2 kinase and induction of cytokine responses. This promotes an increase in mRNA expression of highly potent pro-inflammatory cytokines as interkleukin-1 (IL-1β). [7] [16]
ATG16L1 also plays a role in viral infections. Through autophagy viral particles are delivered into the lysosome degradation pathway and interrogate with a specific type of pattern recognition receptor to initiate type I interferon (IFN-I) expression and viral clearance. Interestingly, ATG5-ATG12/ATG16L1 complex negatively regulates RIG-I-like receptor pathway and IFN-I expression. A mouse with a deletion in one of these genes appears to be resistant to virus replication. It is most likely due to an unregulated overexpression of IFN-I, which interferes with the virus life cycle. [6]
ATG16L2 is a related protein, which is also highly conserved (both ATG16L1 and 2 share 94 and 83% sequence identity). It has been shown that changes in ATG16L2 expression are correlated with Multiple Sclerosis (MS) and can be used as a serum biomarker of the disease and specifically for the prediction of relapse rates. Interestingly ATG16L2 mRNA expression was significantly reduced (~4-fold lower) in T cells isolated from the peripheral blood of MS patients in comparison to healthy age-matched controls, which may reflect their abnormal activation. [10]
Autophagy is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism. It allows the orderly degradation and recycling of cellular components. Although initially characterized as a primordial degradation pathway induced to protect against starvation, it has become increasingly clear that autophagy also plays a major role in the homeostasis of non-starved cells. Defects in autophagy have been linked to various human diseases, including neurodegeneration and cancer, and interest in modulating autophagy as a potential treatment for these diseases has grown rapidly.
Vojo Deretic, is distinguished professor and chair of the Department of Molecular Genetics and Microbiology at the University of New Mexico School of Medicine. Deretic was the founding director of the Autophagy, Inflammation and Metabolism (AIM) Center of Biomedical Research Excellence. The AIM center promotes autophagy research nationally and internationally.
Autophagy related 5 (ATG5) is a protein that, in humans, is encoded by the ATG5 gene located on Chromosome 6. It is an E3 ubi autophagic cell death. ATG5 is a key protein involved in the extension of the phagophoric membrane in autophagic vesicles. It is activated by ATG7 and forms a complex with ATG12 and ATG16L1. This complex is necessary for LC3-I conjugation to PE (phosphatidylethanolamine) to form LC3-II. ATG5 can also act as a pro-apoptotic molecule targeted to the mitochondria. Under low levels of DNA damage, ATG5 can translocate to the nucleus and interact with survivin.
Microtubule-associated proteins 1A/1B light chain 3B is a protein that in humans is encoded by the MAP1LC3B gene. LC3 is a central protein in the autophagy pathway where it functions in autophagy substrate selection and autophagosome biogenesis. LC3 is the most widely used marker of autophagosomes.
Microtubule-associated proteins 1A/1B light chain 3A is a protein that in humans is encoded by the MAP1LC3A gene. Two transcript variants encoding different isoforms have been found for this gene.
Cysteine protease ATG4B is an enzyme that in humans is encoded by the ATG4B gene.
Autophagy related 12 is a protein that in humans is encoded by the ATG12 gene.
WD repeat domain phosphoinositide-interacting protein 2 is a protein that in humans is encoded by the WIPI2 gene.
Autophagy-related protein 9A is a protein that in humans is encoded by the ATG9A gene.
ULK1 is an enzyme that in humans is encoded by the ULK1 gene.
Autophagy related 7 is a protein in humans encoded by ATG7 gene. Related to GSA7; APG7L; APG7-LIKE.
Cysteine protease ATG4A is an enzyme that in humans is encoded by the ATG4A gene.
Mitophagy is the selective degradation of mitochondria by autophagy. It often occurs to defective mitochondria following damage or stress. The process of mitophagy was first described over a hundred years ago by Margaret Reed Lewis and Warren Harmon Lewis. Ashford and Porter used electron microscopy to observe mitochondrial fragments in liver lysosomes by 1962, and a 1977 report suggested that "mitochondria develop functional alterations which would activate autophagy." The term "mitophagy" was in use by 1998.
Autophagy-related protein 8 (Atg8) is a ubiquitin-like protein required for the formation of autophagosomal membranes. The transient conjugation of Atg8 to the autophagosomal membrane through a ubiquitin-like conjugation system is essential for autophagy in eukaryotes. Even though there are homologues in animals, this article mainly focuses on its role in lower eukaryotes such as Saccharomyces cerevisiae.
AuTophaGy related 1 (Atg1) is a 101.7kDa serine/threonine kinase in S.cerevisiae, encoded by the gene ATG1. It is essential for the initial building of the autophagosome and Cvt vesicles. In a non-kinase role it is - through complex formation with Atg13 and Atg17 - directly controlled by the TOR kinase, a sensor for nutrient availability.
Autophagy-related protein 13 also known as ATG13 is a protein that in humans is encoded by the KIAA0652 gene.
Immunity-related GTPase family M protein (IRGM), also known as interferon-inducible protein 1 (IFI1), is an enzyme that in humans is encoded by the IRGM gene.
An autophagosome is a spherical structure with double layer membranes. It is the key structure in macroautophagy, the intracellular degradation system for cytoplasmic contents. After formation, autophagosomes deliver cytoplasmic components to the lysosomes. The outer membrane of an autophagosome fuses with a lysosome to form an autolysosome. The lysosome's hydrolases degrade the autophagosome-delivered contents and its inner membrane.
In molecular biology, autophagy related 3 (Atg3) is the E2 enzyme for the LC3 lipidation process. It is essential for autophagy. The super protein complex, the Atg16L complex, consists of multiple Atg12-Atg5 conjugates. Atg16L has an E3-like role in the LC3 lipidation reaction. The activated intermediate, LC3-Atg3 (E2), is recruited to the site where the lipidation takes place.
Rubicon is a protein that in humans is encoded by the RUBCN gene. Rubicon is one of the few known negative regulators of autophagy, a cellular process that degrades unnecessary or damaged cellular components. Rubicon is recruited to its sites of action through interaction with the small GTPase Rab7, and impairs the autophagosome-lysosome fusion step of autophagy through inhibition of PI3KC3-C2.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.