Autophagic-related cell death of Trypanosoma brucei induced by bacteriocin AS-48

Abstract

The parasitic protozoan Trypanosoma brucei is the causative agent of human African trypanosomiasis (sleeping sickness) and nagana. Current drug therapies have limited efficacy, high toxicity and/or are continually hampered by the appearance of resistance. Antimicrobial peptides have recently attracted attention as potential parasiticidal compounds. Here, we explore circular bacteriocin AS-48's ability to kill clinically relevant bloodstream forms of T. brucei gambiense, T. brucei rhodesiense and T. brucei brucei. AS-48 exhibited excellent anti-trypanosomal activity in vitro (EC50 = 1–3 nM) against the three T. brucei subspecies, but it was innocuous to human cells at 104-fold higher concentrations. In contrast to its antibacterial action, AS-48 does not kill the parasite through plasma membrane permeabilization but by targeting intracellular compartments. This was evidenced by the fact that vital dye internalization-prohibiting concentrations of AS-48 could kill the parasite at 37 °C but not at 4 °C. Furthermore, AS-48 interacted with the surface of the parasite, at least in part via VSG, its uptake was temperature-dependent and clathrin-depleted cells were less permissive to the action of AS-48. The bacteriocin also caused the appearance of myelin-like structures and double-membrane autophagic vacuoles. These changes in the parasite's ultrastructure were confirmed by fluorescence microscopy as AS-48 induced the production of EGFP-ATG8.2-labeled autophagosomes. Collectively, these results indicate AS-48 kills the parasite through a mechanism involving clathrin-mediated endocytosis of VSG-bound AS-48 and the induction of autophagic-like cell death. As AS-48 has greater in vitro activity than the drugs currently used to treat T. brucei infection and does not present any signs of toxicity in mammalian cells, it could be an attractive lead compound for the treatment of sleeping sickness and nagana.

Control of Propionibacterium acnes by natural antimicrobial substances: Role of the bacteriocin AS-48 and lysozyme

“…acnes , encourages us to propose it as a novel and useful candidate for its further pharmacological development against this bacterium. Available experimental data confirm that AS-48 is an amphipathic peptide characterized by a significant proportion of hydrophobic amino acid residues and rich in positively charged residues (8 lysines and 2 arginines), which selectively binds to fluid membranes with a large proportions of anionic phospholipids, as the bacterial membranes, while it leaves intact the rest of normal eukaryotic cell membranes, in which uncharged lipids predominate at the host cell surface 26 , 45 , being some trypanosomides ( Leishmania and Trypanosoma brucei ) the exception 28 , 46 . Moreover, the AS-48 selectivity for the cell membrane leads to a permeabilization that allows rapid movement of small molecules.…”

Circular and Leaderless Bacteriocins: Biosynthesis, Mode of Action, Applications, and Prospects

“…A few select bacteriocins showed some potential as antiviral agents, as plant growth promoters, and as anti-cancer agents ( Drider et al, 2016 ). Recently, it was reported that enterocin AS-48 showed promising bioactivity against the protozoan parasites of the genera Leishmania ( Abengózar et al, 2017 ) and Trypanosoma ( Martínez-García et al, 2018 ).…”

Insights into Chagas treatment based on the potential of bacteriocin AS-48

“…In both cases, the negative surface charge of the parasites has been related to the potent effect of AS-48. Although both parasites are from the same family, different action mechanisms have been described in each one (Abengózar et al, 2017; Martínez-García et al, 2018). The activity of AS-48 against T. brucei is the highest described until now, and it is because the high efficiency in the internalization of AS-48 by the flagellar pocket of the parasite.…”