LL37 and hBD-3 elevate the β-1,3-exoglucanase activity of Candida albicans Xog1p, resulting in reduced fungal adhesion to plastic

Abstract

The opportunistic fungus Candida albicans causes oral thrush and vaginal candidiasis, as well as candidaemia in immunocompromised patients including those undergoing cancer chemotherapy, organ transplant and those with AIDS. We previously found that the AMPs (antimicrobial peptides) LL37 and hBD-3 (human β-defensin-3) inhibited C. albicans viability and its adhesion to plastic. For the present study, the mechanism by which LL37 and hBD-3 reduced C. albicans adhesion was investigated. After AMP treatment, C. albicans adhesion to plastic was reduced by up to ~60% and was dose-dependent. Our previous study indicated that LL37 might interact with the cell-wall β-1,3-exoglucanase Xog1p, which is involved in cell-wall β-glucan metabolism, and consequently the binding of LL37 or hBD-3 to Xog1p might cause the decrease in adhesion. For the present study, Xog1p(41-438)-6H, an N-terminally truncated, active, recombinant construct of Xog1p and Xog1p fragments were produced and used in pull-down assays and ELISA in vitro, which demonstrated that all constructs interacted with both AMPs. Enzymatic analyses showed that LL37 and hBD-3 enhanced the β-1,3-exoglucanase activity of Xog1p(41-438)-6H approximately 2-fold. Therefore elevated Xog1p activity might compromise cell-wall integrity and decrease C. albicans adhesion. To test this hypothesis, C. albicans was treated with 1.3 μM Xog1p(41-438)-6H and C. albicans adhesion to plastic decreased 47.7%. Taken together, the evidence suggests that Xog1p is one of the LL37/hBD-3 targets, and elevated β-1,3-exoglucanase activity reduces C. albicans adhesion to plastic.

Plant-Derived Decapeptide OSIP108 Interferes with Candida albicans Biofilm Formation without Affecting Cell Viability

“…The use of (antimicrobial) peptides from various natural sources as new antibiofilm agents as alternatives to antibiotics/ antimycotics has been increasingly studied during the last few years. For example, antibiofilm activity was reported for LL-37 (the major human cationic host defense peptide) against several Gram-negative and Gram-positive bacteria (38,39), as well as against C. albicans, where it interferes with adhesion (40,41). Moreover, the antibiofilm activity against C. albicans of synthetic antimicrobial peptides such as KSL-W and KABT-AMP has been reported (42,43).…”

Derivatives of the Mouse Cathelicidin-Related Antimicrobial Peptide (CRAMP) Inhibit Fungal and Bacterial Biofilm Formation

“…Wong and colleagues showed that LL13-37 permeabilizes the Candida cell membrane and induces the production of reactive oxygen species (20). LL-37 also inhibits adhesion of C. albicans to plastics and tissues by interacting with yeast cell wall carbohydrates (26) and elevating the ␤-1,3-exoglucanase activity of Xog1 (27). All these data point to potential activity of LL-37 against formation of C. albicans biofilms, as adhesion is an important step in this process.…”

Interplay between Candida albicans and the Antimicrobial Peptide Armory

“…The C. albicans cell wall ␤-1,3-exoglucanase Xog1 has been identified as a LL-37 receptor (10). Xog1-LL-37 interactions led to cell wall remodeling, and Xog1 enzyme activity was elevated, lowering C. albicans adhesion (10,11). Subsequent to cleavage by a serine protease, processed forms of LL-37 were found at the human skin surface (KS-30 and RK-31) (12).…”

“…Interestingly, unlike hBD1 and hBD2, hBD3 kills C. albicans by energy-independent mechanisms. In addition to LL-37, hBD3 elevates Xog1 activity, resulting in reduced C. albicans adherence (10). Cationic peptides derived from the N-terminal portion of human mucin MUC7 associate with the fungal plasma membrane but are also internalized to exert fungicidal activity (23).…”

“…Recently, an Hst 5-spermidine conjugate has been developed, which enhanced fungicidal activity compared to nonconjugated Hst 5 (83). It is known that Hst 5 utilizes the polyamine transporters Dur3 and Dur31 for its uptake in C. albicans (16); therefore, the Hst 5 peptide (Hst 5 with amino acids 4 to 15 [Hst 5 [4][5][6][7][8][9][10][11][12][13][14][15] ]) conjugated with a GGG linker and spermidine was rapidly taken up, leading to higher in vitro and in vivo candicidal activity than with nonconjugated Hst 5 (83). Collectively, these results suggest that the development and investigation of AMP conjugates could lead to promising new antifungals.…”