Human antimicrobial peptide histatin 5 is a cell‐ penetrating peptide targeting mitochondrial ATP synthesis inLeishmania

Abstract

Histatin 5 (Hst5) is a human salivary antimicrobial peptide that targets fungal mitochondria. In the human parasitic protozoa Leishmania, the mitochondrial ATP production is essential, as it lacks the bioenergetic switch between glycolysis and oxidative phosphorylation described in some yeasts. On these premises, Hst5 activity was assayed on both stages of its life cycle, promastigotes and amastigotes (LC(50)=7.3 and 14.4 microM, respectively). In a further step, its lethal mechanism was studied. The main conclusions drawn were as follows: 1) Hst5 causes limited and temporary damage to the plasma membrane of the parasites, as assessed by electron microscopy, depolarization, and entrance of the vital dye SYTOX Green; 2) Hst5 translocates into the cytoplasm of Leishmania in an achiral receptor-independent manner with accumulation into the mitochondrion, as shown by confocal microscopy; and 3) Hst5 produces a bioenergetic collapse of the parasite, caused essentially by the decrease of mitochondrial ATP synthesis through inhibition of F(1)F(0)-ATPase, with subsequent fast ATP exhaustion. By using the Hst5 enantiomer, it was found that the key steps of its lethal mechanism involved no chiral recognition. Hst5 thus constitutes the first leishmanicidal peptide with a defined nonstereospecific intracellular target. The prospects of its development, by its own or as a carrier molecule for other leishmanicidal molecules, into a novel anti-Leishmania drug with a preferential subcellular accumulation are discussed.

Primaquine revisited six decades after its discovery

“…Thus, electrostatic interactions between the positively charged drug and the negatively charged headgroups seem to be the initial step of drug interaction with the protozoan cell surface, after which hydrophobic interactions between the drug's aromatic ring and the phospholipid's inner core of alkyl chains take place, leading to drug insertion [43]. So it seems that sitamaquine exerts its anti-protozoan action in a fashion similar to that of antimicrobial peptides, many of them also reported as promising leishmanicidal agents [231][232][233]. …”

Neuropeptides kill African trypanosomes by targeting intracellular compartments and inducing autophagic-like cell death

“…7,20 Human histatin-5 translocates across the plasma membrane of the trypanosomatid Leishmania in a non-lethal manner and, once inside the cell, targets mitochondria and kills the parasite. 21 Alternatively, trypanolysis mediated by TNF-a and human apolipoprotein-1 (apo-L1) requires uptake and processing of both factors. Although none of these possibilities can be completely excluded, our data suggest that neuropeptides exert their trypanolytic activity through an unusual mechanism that involves peptide uptake by the parasite, disruption of lysosome integrity and cytosolic accumulation of glycolytic enzymes.…”

“…This mechanism also differs from that described for human histatin, which translocates across the plasma membrane through the entire surface of the parasite in a non-lethal manner by inducing cell membrane depolarization. 21 Once endocytosed, neuropeptides initially followed normal delivery pathways in T. brucei, being trafficked from endosome network to lysosome, where they seem to disrupt the endosomal-lysosomal vesicles. Other trypanolytic factors, such as TNF-a and apo-L1, bind to the flagellar pocket, internalize through endocytic vesicles and ultimately localize into large lysosome-like vesicles, where they form ionpermeable channels that induce osmotic swelling of the lysosome until the parasite is lysed.…”

Efficacy of Synthetic Peptides RP-1 and AA-RP-1 against Leishmania Species In Vitro and In Vivo

“…Development of microbial resistance to HDPs is considered to be uncommon or less likely than to conventional antibiotics, ostensibly reflecting the significant changes in structure and phospholipid composition that would be necessary to prevent peptide interactions (18). The diversity of HDPs and their targets has been well documented, and many specific peptides have been demonstrated to have both in vitro and in vivo antiprotozoan activity in prior studies (1,29,30), including plant HDPs (3), various animal-derived HDPs (4,9,15,22,26,33,34), human salivary HDPs (24), and defensin-, magainin-, and cathelicidin-type HDPs (12,21,25).…”