Serendipitous Hinge Modulation Hypothetically Reprograms Caerin 1.1-LC Antibacterial Mechanism and Gram-Negative...

Area of Science:

• Biochemistry
• Microbiology
• Drug Discovery

Background:

• The diminishing efficacy of current antibiotics necessitates the development of novel antimicrobial agents.
• Antimicrobial peptides (AMPs) are emerging as promising candidates for next-generation antibiotics due to their broad-spectrum activity.
• Drug-resistant bacteria pose a significant global health threat, driving research into alternative therapeutic strategies.

Purpose of the Study:

• To identify and characterize novel antimicrobial peptides from natural sources.
• To investigate the structure-activity relationships of antimicrobial peptides, focusing on hinge structures.
• To design and synthesize analogues with improved antibacterial efficacy and reduced toxicity.

Main Methods:

• Isolation and identification of the antimicrobial peptide Caerin 1.1-LC from Litoria caerulea skin secretions.
• Structure-activity relationship studies involving the design of peptide analogues with D-isomers.
• Evaluation of antibacterial activity against Gram-negative bacteria and assessment of haemolytic activity.
• Mechanism of action studies, including membrane potential and ATP disruption assays.
• In vivo efficacy testing in infected larval models and in vitro lipopolysaccharide (LPS) neutralisation assays.

Main Results:

• A novel antimicrobial peptide, Caerin 1.1-LC, was identified.
• Incorporation of D-isomers into the hinge region enhanced antibacterial activity 8-fold against Gram-negative bacteria.
• Haemolytic activity was significantly reduced, improving the therapeutic index by 56-fold.
• The mechanism of action shifted from membrane disruption to a cell-penetrating-like mechanism, involving membrane potential depolarisation and ATP disruption.
• In vivo studies confirmed the therapeutic potential of the D-analogue.

Conclusions:

• Hinge structures are critical for the biological activity of Caerin-family antimicrobial peptides.
• Strategic modification of hinge structures offers a viable approach for optimising peptide-based antibacterial agents.
• The developed D-analogue represents a promising novel antibacterial agent with a significantly improved therapeutic index.