title: Antimicrobial protegrin-1 forms amyloid-like fibrils with rapid kinetics suggesting a functional link.
abstract: Protegrin-1 (PG-1) is an 18 residues long, cysteine-rich β-sheet antimicrobial peptide (AMP). PG-1 induces strong cytotoxic activities on cell membrane and acts as a potent antibiotic agent. Earlier we reported that its cytotoxicity is mediated by its channel-forming ability. In this study, we have examined the amyloidogenic fibril formation properties of PG-1 in comparison with a well-defined amyloid, the amyloid-β (Aβ(1-42)) peptide. We have used atomic force microscopy (AFM) and thioflavin-T staining to investigate the kinetics of PG-1 fibrils growth and molecular dynamics simulations to elucidate the underlying mechanism. AFM images of PG-1 on a highly hydrophilic surface (mica) show fibrils with morphological similarities to Aβ(1-42) fibrils. Real-time AFM imaging of fibril growth suggests that PG-1 fibril growth follows a relatively fast kinetics compared to the Aβ(1-42) fibrils. The AFM results are in close agreement with results from thioflavin-T staining data. Furthermore, the results indicate that PG-1 forms fibrils in solution. Significantly, in contrast, we do not detect fibrillar structures of PG-1 on an anionic lipid bilayer 2-dioleoyl-sn-glycero-3-phospho-L-serine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine; only small PG-1 oligomers can be observed. Molecular dynamics simulations are able to identify the presence of these small oligomers on the membrane bilayer. Thus, our current results show that cytotoxic AMP PG-1 is amyloidogenic and capable of forming fibrils. Overall, comparing β-rich AMPs and amyloids such as Aβ, in addition to cytotoxicity and amyloidogenicity, they share a common structural motif, and are channel forming. These combined properties support a functional relationship between amyloidogenic peptides and β-sheet-rich cytolytic AMPs, suggesting that amyloids channels may have an antimicrobial function.
authors.affiliation: Center for Cancer Research Nanobiology Program, National Cancer Institute-Frederick, SAIC-Frederick, Frederick, Maryland, USA.
authors.forename: Hyunbum
authors.initials: H
authors.lastname: Jang
authors.forename: Fernando Teran
authors.initials: FT
authors.lastname: Arce
authors.forename: Mirela
authors.initials: M
authors.lastname: Mustata
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Ramachandran
authors.forename: Ricardo
authors.initials: R
authors.lastname: Capone
authors.forename: Ruth
authors.initials: R
authors.lastname: Nussinov
authors.forename: Ratnesh
authors.initials: R
authors.lastname: Lal
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D000682:Amyloid / Q000378:metabolism* / Q000648:ultrastructure; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism*; D003198:Computer Simulation; D007700:Kinetics; D008051:Lipid Bilayers; D018625:Microscopy, Atomic Force; D017433:Protein Structure, Secondary; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D000682:Amyloid; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; C094880:protegrin-1; C011934:mica