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The N-terminal region of the human autophagy protein ATG16L1 contains a domain that folds into a helical structure consistent with formation of a coiled-coil.

ABSTRACT: Autophagy is a fundamental cellular process required for organelle degradation and removal of invasive pathogens. Autophagosome formation involves the recruitment of, and interaction between, multiple proteins produced from autophagy-related (ATG) genes. One of the key complexes in autophagosome formation is the ATG12-ATG5-ATG16L1 complex. ATG16L1 functions as a molecular scaffold mediating protein-protein interactions necessary for formation of the autophagosome in response to both classical and pathogen-related autophagy stimuli. The coiled-coil domain of the yeast ortholog, ATG16, exists as a homodimer both in solution and in the crystal form. The yeast and human orthologs show poor sequence identity. Here we have sought to determine the minimal boundaries of the human ATG16L1 coiled-coil domain and ascertain its oligomeric status in solution. Using a range of biochemical and biophysical techniques we show that the secondary structure of the human ATG16L1 coiled-coil has the expected helical composition and that the domain forms a homodimer in solution. We also observe extensive sequence conservation across vertebrates providing strong support for the crucial functional role of the ATG16L1 coiled-coil.

SUBMITTER: Parkhouse R

PROVIDER: S-EPMC3782427 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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The N-terminal region of the human autophagy protein ATG16L1 contains a domain that folds into a helical structure consistent with formation of a coiled-coil.

Parkhouse Rhiannon R Ebong Ima-Obong IO Robinson Carol V CV Monie Tom P TP

PloS one 20130924 9

Autophagy is a fundamental cellular process required for organelle degradation and removal of invasive pathogens. Autophagosome formation involves the recruitment of, and interaction between, multiple proteins produced from autophagy-related (ATG) genes. One of the key complexes in autophagosome formation is the ATG12-ATG5-ATG16L1 complex. ATG16L1 functions as a molecular scaffold mediating protein-protein interactions necessary for formation of the autophagosome in response to both classical an ...[more]

PMID: 24086718

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Project description:Macroautophagy/autophagy delivers damaged proteins and organelles to lysosomes for degradation, and plays important roles in maintaining tissue homeostasis by reducing tissue damage. The translocation of LC3 to the limiting membrane of the phagophore, the precursor to the autophagosome, during autophagy provides a binding site for autophagy cargoes, and facilitates fusion with lysosomes. An autophagy-related pathway called LC3-associated phagocytosis (LAP) targets LC3 to phagosome and endosome membranes during uptake of bacterial and fungal pathogens, and targets LC3 to swollen endosomes containing particulate material or apoptotic cells. We have investigated the roles played by autophagy and LAP in vivo by exploiting the observation that the WD domain of ATG16L1 is required for LAP, but not autophagy. Mice lacking the linker and WD domains, activate autophagy, but are deficient in LAP. The LAP-/- mice survive postnatal starvation, grow at the same rate as littermate controls, and are fertile. The liver, kidney, brain and muscle of these mice maintain levels of autophagy cargoes such as LC3 and SQSTM1/p62 similar to littermate controls, and prevent accumulation of SQSTM1 inclusions and tissue damage associated with loss of autophagy. The results suggest that autophagy maintains tissue homeostasis in mice independently of LC3-associated phagocytosis. Further deletion of glutamate E230 in the coiled-coil domain required for WIPI2 binding produced mice with defective autophagy that survived neonatal starvation. Analysis of brain lysates suggested that interactions between WIPI2 and ATG16L1 were less critical for autophagy in the brain, which may allow a low level of autophagy to overcome neonatal lethality. Abbreviations: CCD: coiled-coil domain; CYBB/NOX2: cytochrome b-245: beta polypeptide; GPT/ALT: glutamic pyruvic transaminase: soluble; LAP: LC3-associated phagocytosis; LC3: microtubule-associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; NOD: nucleotide-binding oligomerization domain; NADPH: nicotinamide adenine dinucleotide phosphate; RUBCN/Rubicon: RUN domain and cysteine-rich domain containing Beclin 1-interacting protein; SLE: systemic lupus erythematosus; SQSTM1/p62: sequestosome 1; TLR: toll-like receptor; TMEM: transmembrane protein; TRIM: tripartite motif-containing protein; UVRAG: UV radiation resistance associated gene; WD: tryptophan-aspartic acid; WIPI: WD 40 repeat domain: phosphoinositide interacting.

Project description:BACKGROUND: PcrV is a hydrophilic translocator of type three secretion system (TTSS) and a structural component of the functional translocon. C-terminal helix of PcrV is essential for its oligomerization at the needle tip. Conformational changes within PcrV regulate the effector translocation. PcrG is a cytoplasmic regulator of TTSS and forms a high affinity complex with PcrV. C-terminal residues of PcrG control the effector secretion. RESULT: Both PcrV and PcrG-PcrV complex exhibit elongated conformation like their close homologs LcrV and LcrG-LcrV complex. The homology model of PcrV depicts a dumbbell shaped structure with N and C-terminal globular domains. The grip of the dumbbell is formed by two long helices (helix-7 and 12), which show high level of conservation both structurally and evolutionary. PcrG specifically protects a region of PcrV extending from helix-12 to helix-7, and encompassing the C-terminal globular domain. This fragment ?PcrV(128-294) interacts with PcrG with high affinity, comparable to the wild type interaction. Deletion of N-terminal globular domain leads to the oligomerization of PcrV, but PcrG restores the monomeric state of PcrV by forming a heterodimeric complex. The N-terminal globular domain (?PcrV(1-127)) does not interact with PcrG but maintains its monomeric state. Interaction affinities of various domains of PcrV with PcrG illustrates that helix-12 is the key mediator of PcrG-PcrV interaction, supported by helix-7. Bioinformatic analysis and study with our deletion mutant ?PcrG(13-72) revealed that the first predicted intramolecular coiled-coil domain of PcrG contains the PcrV interaction site. However, 12?N-terminal amino acids of PcrG play an indirect role in PcrG-PcrV interaction, as their deletion causes 40-fold reduction in binding affinity and changes the kinetic parameters of interaction. ?PcrG(13-72) fits within the groove formed between the two globular domains of PcrV, through hydrophobic interaction. CONCLUSION: PcrG interacts with PcrV through its intramolecular coiled-coil region and masks the domains responsible for oligomerization of PcrV at the needle tip. Also, PcrG could restore the monomeric state of oligomeric PcrV. Therefore, PcrG prevents the premature oligomerization of PcrV and maintains its functional state within the bacterial cytoplasm, which is a pre-requisite for formation of the functional translocon.

Project description:BackgroundThe availability of the P. falciparum genome has led to novel ways to identify potential vaccine candidates. A new approach for antigen discovery based on the bioinformatic selection of heptad repeat motifs corresponding to alpha-helical coiled coil structures yielded promising results. To elucidate the question about the relationship between the coiled coil motifs and their sequence conservation, we have assessed the extent of polymorphism in putative alpha-helical coiled coil domains in culture strains, in natural populations and in the single nucleotide polymorphism data available at PlasmoDB.Methodology/principal findings14 alpha-helical coiled coil domains were selected based on preclinical experimental evaluation. They were tested by PCR amplification and sequencing of different P. falciparum culture strains and field isolates. We found that only 3 out of 14 alpha-helical coiled coils showed point mutations and/or length polymorphisms. Based on promising immunological results 5 of these peptides were selected for further analysis. Direct sequencing of field samples from Papua New Guinea and Tanzania showed that 3 out of these 5 peptides were completely conserved. An in silico analysis of polymorphism was performed for all 166 putative alpha-helical coiled coil domains originally identified in the P. falciparum genome. We found that 82% (137/166) of these peptides were conserved, and for one peptide only the detected SNPs decreased substantially the probability score for alpha-helical coiled coil formation. More SNPs were found in arrays of almost perfect tandem repeats. In summary, the coiled coil structure prediction was rarely modified by SNPs. The analysis revealed a number of peptides with strictly conserved alpha-helical coiled coil motifs.Conclusion/significanceWe conclude that the selection of alpha-helical coiled coil structural motifs is a valuable approach to identify potential vaccine targets showing a high degree of conservation.

Dataset Information

The N-terminal region of the human autophagy protein ATG16L1 contains a domain that folds into a helical structure consistent with formation of a coiled-coil.

Publications

The N-terminal region of the human autophagy protein ATG16L1 contains a domain that folds into a helical structure consistent with formation of a coiled-coil.

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