Antimicrobial Peptides Derived from the Immune Defense Protein CAP37 Inhibit TLR4 Activation by S100A9

Area of Science:

• Ophthalmology
• Immunology
• Molecular Biology

Background:

• Corneal abrasion is a common eye injury complicated by bacterial infection.
• Cationic antimicrobial protein of 37 kDa (CAP37) and its derived peptides promote corneal re-epithelialization and possess antibacterial properties.

Purpose of the Study:

• To elucidate the molecular mechanisms behind the wound-healing effects of CAP37 and its bioactive peptides.
• To identify CAP37 binding partners on corneal epithelial cells.
• To investigate the interaction of CAP37 and its peptides with identified receptors.

Main Methods:

• Ligand-receptor glycocapture using TriCEPS to identify CAP37 binding partners on human corneal epithelial cells (hTCEpi).
• ELISA assays to confirm binding interactions between CAP37, its peptides, and identified partners.
• Reporter cell lines to assess membrane receptor activation by CAP37 and its peptides.

Main Results:

• S100 calcium-binding protein A9 (S100A9) was identified as a binding partner for CAP37 and four derived peptides.
• CAP37 and S100A9-binding peptides interact with Toll-like receptor 4 (TLR4).
• CAP37 and peptides inhibited S100A9-induced TLR4 activation, with one peptide partially activating TLR4.

Conclusions:

• Identified a mechanism where CAP37 and its peptides may modulate inflammatory responses.
• The findings suggest a role for CAP37 in restraining inflammation and promoting corneal re-epithelialization after injury.