Effects of histatin 5 and derived peptides on Candida albicans

Abstract

Three anti-microbial peptides were compared with respect to their killing activity against Candida albicans and their ability to disturb its cellular and internal membranes. Histatin 5 is an anti-fungal peptide occurring naturally in human saliva, while dhvar4 and dhvar5 are variants of its active domain, with increased anti-microbial activity. dhvar4has increased amphipathicity compared with histatin 5, whereas dhvar5has amphipathicity comparable with that of histatin 5. All three peptides caused depolarization of the cytoplasmic and/or mitochondrial membrane, indicating membranolytic activity. For the variant peptides both depolarization and killing occurred at a faster rate. With FITC-labelled peptides, no association with the cytoplasmic membrane was observed, contradicting the formation of permanent transmembrane multimeric peptide pores. Instead, the peptides were internalized and act on internal membranes, as demonstrated with mitochondrion- and vacuole-specific markers. In comparison with histatin 5, the variant peptides showed a more destructive effect on mitochondria. Entry of the peptides and subsequent killing were dependent on the metabolic state of the cells. Blocking of the mitochondrial activity led to complete protection against histatin 5 activity, whereas that of dhvar4 was hardly affected and that of dhvar5 was affected only intermediately.

Histatin 5 Uptake by Candida albicans Utilizes Polyamine Transporters Dur3 and Dur31 Proteins

“…Substitution of functionally nonessential residues of Hst 5 with proline to disrupt any secondary structure resulted in unaltered candidacidal activity (10), showing that the degree of the amphipathic molecular moment is not involved in its fungicidal activity. Furthermore, synthetic variants of Hst 5 with increased (dhvar4) and decreased (dhvar5) amphipathic features both killed C. albicans (11). Comparison with amphipathic peptides that translocated across and disrupted liposome membranes showed that Hst 5 did not interact with model membranes (12).…”

The human salivary peptide histatin 5 exerts its antifungal activity through the formation of reactive oxygen species

“…Structural analysis has revealed that histatins differ from amphipathic membrane-active peptides by virtue of their reluctance to rapidly adopt helical structures in moderately hydrophobic environments and the weak amphipathicity of their ␣-helical structures (8,9). The interaction of histatin 5 with liposome vesicles, mitochondria, or C. albicans blastoconidia does not result in a massive disintegration and depolarization of the membranes such as is achieved with strongly amphipathic peptides (9)(10)(11). The general consensus therefore is that the ultimate events in histatin-provoked cell death are not restricted to direct membrane effects.…”

Candida albicans biofilm formation on peptide functionalized polydimethylsiloxane

“…Their effects on cytoplasmatic membranes are limited and permeabilization of the microbial membrane is a secondary effect rather than the primary cause of their antimicrobial activity (Ruissen et al 2001(Ruissen et al , 2002Den 20 Hertog et al 2005, Welling et al 2007. The most potent anti-Candida member of this family is Hst 5 and analysis of its sequence showed the presence of lysine and arginine residues (Helmerhorst et al 1997).…”