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

Abstract

We previously identified a decapeptide from the model plant Arabidopsis thaliana, OSIP108, which is induced upon fungal pathogen infection. In this study, we demonstrated that OSIP108 interferes with biofilm formation of the fungal pathogen Candida albicans without affecting the viability or growth of C. albicans cells. OSIP108 displayed no cytotoxicity against various human cell lines. Furthermore, OSIP108 enhanced the activity of the antifungal agents amphotericin B and caspofungin in vitro and in vivo in a Caenorhabditis elegans-C. albicans biofilm infection model. These data point to the potential use of OSIP108 in combination therapy with conventional antifungal agents. In a first attempt to unravel its mode of action, we screened a library of 137 homozygous C. albicans mutants, affected in genes encoding cell wall proteins or transcription factors important for biofilm formation, for altered OSIP108 sensitivity. We identified 9 OSIP108-tolerant C. albicans mutants that were defective in either components important for cell wall integrity or the yeast-to-hypha transition. In line with these findings, we demonstrated that OSIP108 activates the C. albicans cell wall integrity pathway and that its antibiofilm activity can be blocked by compounds inhibiting the yeast-to-hypha transition. Furthermore, we found that OSIP108 is predominantly localized at the C. albicans cell surface. These data point to interference of OSIP108 with cell wall-related processes of C. albicans, resulting in impaired biofilm formation.

Structure-Activity Relationship Study of the Plant-Derived Decapeptide OSIP108 Inhibiting Candida albicans Biofilm Formation

“…Furthermore, OSIP108 synergistically interacts with amphotericin B and caspofungin against mature C. albicans biofilms (14). A preliminary structure-activity relationship study of OSIP108 showed that (i) the order of amino acid residues is important for antibiofilm activity, as a scrambled version (S-OSIP108) containing all amino acids of OSIP108 but in a randomized order showed no antibiofilm activity, (ii) OSIP108 containing all amino acids in the D-configuration (D-OSIP108) still exhibits antibiofilm activity, and (iii) cyclization of OSIP108 is not favorable for its antibiofilm activity (14). In this follow-up study, we performed a whole amino acid scan of OSIP108, in which every amino acid of OSIP108 was individually replaced by all 19 other common amino acids (190 OSIP108 analogues).…”

“…We previously identified the Arabidopsis thaliana-derived decapeptide OSIP108 (13), which specifically interferes with the biofilm formation process of C. albicans without affecting cell viability (14). The latter is an important characteristic to potentially limit the incidence of resistance.…”

“…The 190 peptide analogues of OSIP108 (MLCVLQGLRE) were ordered from Pepscan (Lelystad, The Netherlands) and were of crude purity, and the abilities to inhibit biofilm formation of C. albicans SC5314 (at 0.39 to 50 M) were assessed as described previously (14). BIC-2 values, i.e., the minimal peptide concentrations that reduced the metabolic activity of the biofilms by 50% (14), were determined relative to the growth control (0.5% dimethyl sulfoxide), and the fold change in the BIC-2, relative to the native OSIP108 peptide, was calculated.…”

Identification of survival-promoting OSIP108 peptide variants and their internalization in human cells

“…We previously showed that OSIP108 can also inhibit formation of Candida albicans biofilms (Delattin et al, 2014c). C. albicans is the predominant human fungal pathogen and accounts for 35% of invasive fungal infections (Lewis et al, 2013).…”

“…C. albicans cells can also grow as a surface-attached biofilm, e.g., on catheters and heart valves, thereby causing recurrent systemic infections (Cuéllar-Cruz et al, 2012;Mayer et al, 2013), which are in general resistant to most antimycotics (De Cremer et al, 2015;Delattin et al, 2014a). In the search for novel antibiofilm molecules, we previously identified OSIP108 as a new antibiofilm peptide (Delattin et al, 2014c). To get more insight into important amino acids that are linked to OSIP108's antibiofilm activity, we also performed a SAR using the same amino acid replacement scan (Delattin et al, 2014b).…”