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Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus

Mutagenesis studies to test the evolutionarily conserved oligomerization activity AIM2Hin in dsDNA binding.(a) The sequence alignment of AIM2Hin and p202HinB. The mutated side chains are indicated in red. (b) The crystal structure of dsDNA-bound AIM2Hin (coloured in ‘wheat;' PDB ID: 3RN2) aligned to the p202HinB tetramer structure (PDB ID: 4L5T); root mean squared deviation of alignment is 1.5 Å. The p202HinB protomers are coloured in green, yellow, pink and cyan, respectively. The mutated side chains are shown as spheres. AIM2 side chains are labelled in black and those of p202 are indicated in cyan. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL HIN200 mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2. (d) Binding of various AIM2Hin mutants were tested on FAM-dsDNA72 (5 nM) at 160 mM KCl. The determined KD values are listed in Supplementary Table 2.
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f4: Mutagenesis studies to test the evolutionarily conserved oligomerization activity AIM2Hin in dsDNA binding.(a) The sequence alignment of AIM2Hin and p202HinB. The mutated side chains are indicated in red. (b) The crystal structure of dsDNA-bound AIM2Hin (coloured in ‘wheat;' PDB ID: 3RN2) aligned to the p202HinB tetramer structure (PDB ID: 4L5T); root mean squared deviation of alignment is 1.5 Å. The p202HinB protomers are coloured in green, yellow, pink and cyan, respectively. The mutated side chains are shown as spheres. AIM2 side chains are labelled in black and those of p202 are indicated in cyan. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL HIN200 mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2. (d) Binding of various AIM2Hin mutants were tested on FAM-dsDNA72 (5 nM) at 160 mM KCl. The determined KD values are listed in Supplementary Table 2.

Mentions: In contrast to the dsDNA-binding HIN200 domains of related IFI16 (ref. 23), our dsDNA-binding studies suggest that AIM2Hin alone oligomerizes on dsDNA (Figs 1c and 2b,d,f). On the other hand, a murine ALR named p202 inhibits the activity of AIM2 by binding to AIM2Hin with its tetrameric second HIN200 domain (p202HinB); p202HinB does not bind dsDNA38. Several p202HinB side chains implicated in tetramerization38 are conserved in AIM2Hin (Fig. 4a,b). To test whether AIM2Hin uses similarly positioned side chains as p202HinB to cluster on dsDNA, we mutated the indicated side chains in Fig. 4a,b on both AIM2FL and isolated AIM2Hin. We found mutations distal to the dsDNA-binding surface significantly decreased dsDNA binding by both AIM2FL and AIM2Hin (Fig. 4c,d). These results not only support the idea that the oligomerization of AIM2Hin is important for dsDNA binding but also suggest that the oligomerization of AIM2Hin is an evolutionarily conserved feature.


Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Mutagenesis studies to test the evolutionarily conserved oligomerization activity AIM2Hin in dsDNA binding.(a) The sequence alignment of AIM2Hin and p202HinB. The mutated side chains are indicated in red. (b) The crystal structure of dsDNA-bound AIM2Hin (coloured in ‘wheat;' PDB ID: 3RN2) aligned to the p202HinB tetramer structure (PDB ID: 4L5T); root mean squared deviation of alignment is 1.5 Å. The p202HinB protomers are coloured in green, yellow, pink and cyan, respectively. The mutated side chains are shown as spheres. AIM2 side chains are labelled in black and those of p202 are indicated in cyan. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL HIN200 mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2. (d) Binding of various AIM2Hin mutants were tested on FAM-dsDNA72 (5 nM) at 160 mM KCl. The determined KD values are listed in Supplementary Table 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4525163&req=5

f4: Mutagenesis studies to test the evolutionarily conserved oligomerization activity AIM2Hin in dsDNA binding.(a) The sequence alignment of AIM2Hin and p202HinB. The mutated side chains are indicated in red. (b) The crystal structure of dsDNA-bound AIM2Hin (coloured in ‘wheat;' PDB ID: 3RN2) aligned to the p202HinB tetramer structure (PDB ID: 4L5T); root mean squared deviation of alignment is 1.5 Å. The p202HinB protomers are coloured in green, yellow, pink and cyan, respectively. The mutated side chains are shown as spheres. AIM2 side chains are labelled in black and those of p202 are indicated in cyan. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL HIN200 mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2. (d) Binding of various AIM2Hin mutants were tested on FAM-dsDNA72 (5 nM) at 160 mM KCl. The determined KD values are listed in Supplementary Table 2.
Mentions: In contrast to the dsDNA-binding HIN200 domains of related IFI16 (ref. 23), our dsDNA-binding studies suggest that AIM2Hin alone oligomerizes on dsDNA (Figs 1c and 2b,d,f). On the other hand, a murine ALR named p202 inhibits the activity of AIM2 by binding to AIM2Hin with its tetrameric second HIN200 domain (p202HinB); p202HinB does not bind dsDNA38. Several p202HinB side chains implicated in tetramerization38 are conserved in AIM2Hin (Fig. 4a,b). To test whether AIM2Hin uses similarly positioned side chains as p202HinB to cluster on dsDNA, we mutated the indicated side chains in Fig. 4a,b on both AIM2FL and isolated AIM2Hin. We found mutations distal to the dsDNA-binding surface significantly decreased dsDNA binding by both AIM2FL and AIM2Hin (Fig. 4c,d). These results not only support the idea that the oligomerization of AIM2Hin is important for dsDNA binding but also suggest that the oligomerization of AIM2Hin is an evolutionarily conserved feature.

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus