The Human Antimicrobial Peptides Dermcidin and LL-37 Show Novel Distinct Pathways in Membrane Interactions

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Mammals utilize antimicrobial peptides (AMPs) to combat microbial infections.
• AMPs often function by disrupting bacterial cell membranes.
• Existing mechanistic models (barrel stave, toroidal, carpet) for AMP-induced pore formation are simplified and lack in vivo/in vitro relevance.

Purpose of the Study:

• To challenge and refine existing AMP membrane interaction models.
• To investigate the structure-based mechanisms of human cathelicidin (LL-37) and dermcidin (DCD) in membrane disruption.
• To compare the distinct membrane targeting strategies of LL-37 and DCD.

Main Methods:

• Structure-based investigation of LL-37 and DCD interactions with membranes.
• Analysis of peptide assembly and pore formation at atomic resolution.
• Comparison of observed mechanisms with established barrel stave, toroidal, and carpet models.

Main Results:

• Dermcidin (DCD) forms a hexameric pre-channel complex in solution, deviating from the barrel stave model.
• Human cathelicidin (LL-37) forms oligomers and fibril-like structures on membranes.
• LL-37 also assembles into transmembrane pores, exhibiting a deviation from the toroidal pore model.

Conclusions:

• LL-37 and DCD exhibit unique, complex membrane interaction and pore-forming mechanisms.
• These findings necessitate refinement of current simplified models for antimicrobial peptide action.
• Understanding these specific mechanisms provides insights into innate immunity and potential therapeutic strategies.