Citrullination Alters the Antibacterial and Anti-Inflammatory Functions of the Host Defense Peptide Canine Cathelicidin K9CATH In Vitro

Abstract K9CATH is the sole cathelicidin in canines (dogs) and exhibits broad antimicrobial activity against both Gram-positive Gram-negative bacteria. also modulates inflammatory responses binds to LPS. These activities depend on secondary structure a net-positive charge of peptide. Peptidylarginine deiminases (PAD) convert cationic peptidyl arginine neutral citrulline. Thus, we hypothesized that citrullination biologically relevant modification peptide would reduce antibacterial LPS-binding K9CATH. Recombinant PAD2 PAD4 citrullinated various extents circular dichroism spectroscopy revealed native exhibited similar α-helical structures. Notably, reduced its bactericidal activity, abolished ability permeabilize membrane bacteria hemolytic capacity. Electron microscopy showed did not cause any morphological changes bacteria, whereas caused clear alterations integrity, concordant with rapid effect. Finally, impaired capacity inhibit LPS-mediated release proinflammatory molecules from mouse canine macrophages. In conclusion, attenuates properties K9CATH, demonstrating importance net positive for lysis effects suggests means regulate activities.