Helical antimicrobial peptides assemble into protofibril scaffolds that present ordered dsDNA to TLR9

• Published in: Nature communications Vol. 10; no. 1; p. 1012
• Main Authors: Lee, Ernest Y., Zhang, Changsheng, Di Domizio, Jeremy, Jin, Fan, Connell, Will, Hung, Mandy, Malkoff, Nicolas, Veksler, Veronica, Gilliet, Michel, Ren, Pengyu, Wong, Gerard C. L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04-03-2019; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 13/21; 631/250/256/2516; 631/250/262/2106/2108; 631/45/535/1261; 631/92/610; acute inflammation; Amplification; Anti-Infective Agents - chemistry; Anti-Infective Agents - immunology; Anti-Infective Agents - pharmacology; Antiinfectives and antibacterials; Antimicrobial agents; Antimicrobial Cationic Peptides - chemistry; Antimicrobial Cationic Peptides - pharmacology; Antimicrobial peptides; Autoimmune diseases; BASIC BIOLOGICAL SCIENCES; Cell Death - drug effects; Cell Membrane - drug effects; Computer Simulation; Deoxyribonucleic acid; DNA; DNA - chemistry; DNA - immunology; Humanities and Social Sciences; Humans; Immune system; Immunologic Factors - chemistry; Immunologic Factors - immunology; Immunomodulation; Inflammation; Ligands; Macrophages - drug effects; Models, Molecular; Molecular modelling; multidisciplinary; Mutants; nucleic acids; Peptides; Protein Conformation, alpha-Helical - physiology; Proteins; SAXS; Scaffolds; Scattering, Radiation; Science; science & technology - other topics; Science (multidisciplinary); Small angle X ray scattering; Superhelical DNA; TLR9 protein; Toll-Like Receptor 9 - chemistry; Toll-Like Receptor 9 - immunology; Toll-like receptors; X-Ray Diffraction; X-ray scattering
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08868-w

Amphiphilicity in ɑ-helical antimicrobial peptides (AMPs) is recognized as a signature of potential membrane activity. Some AMPs are also strongly immunomodulatory: LL37-DNA complexes potently amplify Toll-like receptor 9 (TLR9) activation in immune cells and exacerbate autoimmune diseases. The rules governing this proinflammatory activity of AMPs are unknown. Here we examine the supramolecular structures formed between DNA and three prototypical AMPs using small angle X-ray scattering and molecular modeling. We correlate these structures to their ability to activate TLR9 and show that a key criterion is the AMP’s ability to assemble into superhelical protofibril scaffolds. These structures enforce spatially-periodic DNA organization in nanocrystalline immunocomplexes that trigger strong recognition by TLR9, which is conventionally known to bind single DNA ligands. We demonstrate that we can “knock in” this ability for TLR9 amplification in membrane-active AMP mutants, which suggests the existence of tradeoffs between membrane permeating activity and immunomodulatory activity in AMP sequences.
Amphihelical antimicrobial peptides (AMPs) are bactericidal host defense factors, but their function as immunomodulators is emerging. Here the authors show that several AMPs organize DNA into periodic nanocrystals by self-assembling into superhelical protofibril scaffolds, which potentiates DNA sensing by TLR9.