The major surface‐metalloprotease of the parasitic protozoan, Leishmania, protects against antimicrobial peptide‐induced apoptotic killing

MM Kulkarni, WR McMaster, E Kamysz… - Molecular …, 2006 - Wiley Online Library
MM Kulkarni, WR McMaster, E Kamysz, W Kamysz, DM Engman, BS McGwire
Molecular microbiology, 2006Wiley Online Library
Human infection by the vector‐borne protozoan Leishmania is responsible for substantial
worldwide morbidity and mortality. The surface‐metalloprotease (leishmanolysin) of
Leishmania is a virulence factor which contributes to a variety of functions including evasion
of complement‐mediated parasite‐killing and host intramacrophage survival. We tested the
hypothesis that leishmanolysin serves to protect parasites from the cytolytic effects of various
antimicrobial peptides (AMPs) which are important components of the innate immune …
Summary
Human infection by the vector‐borne protozoan Leishmania is responsible for substantial worldwide morbidity and mortality. The surface‐metalloprotease (leishmanolysin) of Leishmania is a virulence factor which contributes to a variety of functions including evasion of complement‐mediated parasite‐killing and host intramacrophage survival. We tested the hypothesis that leishmanolysin serves to protect parasites from the cytolytic effects of various antimicrobial peptides (AMPs) which are important components of the innate immune system. We found that members of the α‐ and θ‐defensins, magainins and cathelicidins had substantially higher leishmanicidal activity against leishmanolysin‐knock out mutants of L. major. Using the magainin analogue, pexiganan, as a model peptide we show that AMP evasion is due to rapid and extensive peptide degradation by wild‐type parasites. Pexiganan‐treatment of knock out mutants induced disruption of surface‐membrane permeability and expression of features of apoptosis including smaller cell size, loss of mitochondrial membrane potential, exposure of surface phosphatidyl serine as well as induction of caspase 3/7 activity. These results demonstrate leishmanolysin as a virulence factor preventing AMP‐mediated apoptotic killing. This study serves as a platform for the dissection of the AMP‐mediated death pathways of Leishmania and demonstrates the potential that AMP evasion plays during host infection by this parasite.
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