Human β-Defensin 4 with Non-Native Disulfide Bridges Exhibit Antimicrobial Activity

Abstract

Human defensins play multiple roles in innate immunity including direct antimicrobial killing and immunomodulatory activity. They have three disulfide bridges which contribute to the stability of three anti-parallel β-strands. The exact role of disulfide bridges and canonical β-structure in the antimicrobial action is not yet fully understood. In this study, we have explored the antimicrobial activity of human β-defensin 4 (HBD4) analogs that differ in the number and connectivity of disulfide bridges. The cysteine framework was similar to the disulfide bridges present in μ-conotoxins, an unrelated class of peptide toxins. All the analogs possessed enhanced antimicrobial potency as compared to native HBD4. Among the analogs, the single disulfide bridged peptide showed maximum potency. However, there were no marked differences in the secondary structure of the analogs. Subtle variations were observed in the localization and membrane interaction of the analogs with bacteria and Candida albicans, suggesting a role for disulfide bridges in modulating their antimicrobial action. All analogs accumulated in the cytosol where they can bind to anionic molecules such as nucleic acids which would affect several cellular processes leading to cell death. Our study strongly suggests that native disulfide bridges or the canonical β-strands in defensins have not evolved for maximal activity but they play important roles in determining their antimicrobial potency.

Antimicrobial activity of the indolicidin‐derived novel synthetic peptide In‐58

“…Given that indolicidin induces local thinning of the bilayer ; these formations are likely vesicles formed from phospholipids of the cell's membrane and containing part of the intracellular material. Similar images were obtained by confocal microscopy of E. coli treated with human beta‐defensins‐4 modified by introducing disulfide bridges .…”

Antimicrobial activity and structure of a consensus human β‐defensin and its comparison to a novel putative hBD10

“…Also, the proportion of hydrophobic groups in the surface is quite similar in most defensins, ranging from 45% to 65%. Thus, the ability of β‐defensins to interact with microbial membranes is determined more by the ratio of polar to hydrophobic residues on the peptide surface or by the total positive charge, rather than by their individual primary structures or three‐dimensional structures, with the β‐defensin fold or disulfide pattern not being mandatory for antimicrobial activity . Even though these common features are required for antimicrobial activity, structure analyses have failed to detect a common pattern of amino acidic residues for the distribution of polar and hydrophobic residues on the surface of β‐defensins .…”

“…Thus, the ability of β-defensins to interact with microbial membranes is determined more by the ratio of polar to hydrophobic residues on the peptide surface or by the total positive charge, rather than by their individual primary structures or three-dimensional structures, with the β-defensin fold or disulfide pattern not being mandatory for antimicrobial activity. 41,48,49,51,53,54 Even though these common features are required for antimicrobial activity, structure analyses have failed to detect a common pattern of amino acidic residues for the distribution of polar and hydrophobic residues on the surface of β-defensins. 41 However, minor differences in β-defensin structural features may be responsible for their specificity toward certain types of bacteria, fungi or protozoa.…”

A skewed pool of resident T cells triggers psoriasis-associated tissue responses in never-lesional skin from patients with psoriasis

“…Both CCL20 and HBD2 have antifungal properties, [40][41][42] and we next exposed whole skin biopsy specimens to fungal products. In line with our findings in primary keratinocytes, heat-killed C albicans increased CCL20 and DEFB4A/B expression in epidermis from NLP but not healthy epidermis (Fig 5, E).…”