Antimicrobial Protegrin-1 Forms Amyloid-Like Fibrils with Rapid Kinetics Suggesting a Functional Link

• Published in: Biophysical journal 2011-04, Vol.100 (7), p.1775-1783
• Main Authors: Jang, Hyunbum, Arce, Fernando Teran, Mustata, Mirela, Ramachandran, Srinivasan, Capone, Ricardo, Nussinov, Ruth, Lal, Ratnesh
• Format: Article
• Language: English
• Subjects: adenosine monophosphate; Adsorption; Aluminum Silicates - chemistry; Alzheimer's disease; amyloid; Amyloid - metabolism; Amyloid - ultrastructure; antibiotics; Antimicrobial Cationic Peptides - chemistry; Antimicrobial Cationic Peptides - metabolism; antimicrobial peptides; atomic force microscopy; cell membranes; Cells; Computer Simulation; cytotoxicity; hydrophilicity; image analysis; Kinetics; Lipid Bilayers; Membranes; mica; Microscopy, Atomic Force; molecular dynamics; Molecular structure; Morphology; Peptides; Protein; Protein Structure, Secondary; Proteins; Reaction kinetics; Time Factors
• ISSN: 0006-3495; 1542-0086; 1542-0086
• DOI: 10.1016/j.bpj.2011.01.072

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 (Aβ1–42) 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 Aβ1–42 fibrils. Real-time AFM imaging of fibril growth suggests that PG-1 fibril growth follows a relatively fast kinetics compared to the Aβ1–42 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.