Cysteine Proteinases and Cell Death cascade in Leishmania parasites

• Unité de recherche: COST
• Numéro de projet: C09.0042
• Titre du projet anglais: Cysteine Proteinases and Cell Death cascade in Leishmania parasites

Mots-clé (Anglais)

cell death; metacaspase; synthetic peptide; anti leishmanial drugs

Programme de recherche (Anglais)

COST-Action BM0802 - Life or death of protozoan parasites

Description succincte (Anglais)

In protozoan parasites, molecular mechanisms implicated in the cell death (CD) pathway are thus far poorly characterized. In the parasite Leishmania, anti-leishmania drugs, nitric oxide (NO) and hydrogen peroxide (H2O2) have been shown to induce defined cell death (CD) markers. These treatments induce CD together with processing of the metacaspase and the release of a lysosomal cathepsin B-like enzyme as executioner proteases in the CD cascade. In this proposal, we intend to characterize events in the CD cascade of Leishmania parasites with the aim to validate the relevance of the cathepsin B-like enzyme in relation to Leishmania metacaspase, to identify its substrates in physiological and stress situations and to determine the relationship between the CD cascade and the action of anti-leishmania drugs.

Partenaires et organisations internationales (Anglais)

BE, CH, DE, DK, ES, FR, GR, IL, IT, NL, PT, UK

Résumé des résultats (Abstract) (Anglais)

It is now admitted that single celled protozoan parasites undergo cell death in a regulated manner. Nevertheless, the molecular pathway underneath remains to be established. As trypanosomes do not encode caspases, the key mediators of programmed cell death in higher eukaryotes, we investigated the metacaspase protein (LmjMCA), which has been described as a caspase homologue that is mainly restricted to lower eukaryotes and plants. We showed that, in stress conditions, LmjMCA precursor forms were extensively processed into soluble forms containing the catalytic domain and this domain was sufficient to enhance sensitivity of parasites to hydrogen peroxide by impairing the mitochondrion function. We then tested different lengths of LmjMCA catalytic domain and found that the overexpression of the polypeptide corresponding to amino acids 136-218 was sufficient to sensitize L. major mitochondria to oxidative stress. These findings were used to synthesize an 83aa long peptide corresponding to the minimal metacaspase catalytic domain. We showed that the peptide was catalytically active in vitro and that it was able to participate in the cell death pathway in vivo. We also showed that our active peptide was able to enter infected cells and could eliminate parasites present in macrophages or in parasite induced lesions. Therefore, based on a peptide implicated in the cell death of parasites, we could conclude that metacaspase could be a valuable tool to prevent the formation of lesions or to reduce the severity of the disease. Potentially, this approach could be used for other pathogens expressing metacaspase such as Plasmodium or pathogenic fungi.

Références bases de données (Anglais)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C09.0042