Journal Article

Mitochondrial peroxiredoxin functions as crucial chaperone reservoir in Leishmania infantum

Helena Castro, Ursula Jakob, Tânia Cruz, Ana M. Tomás, Eric Tse, Filipa Teixeira, Philipp Koldewey, Daniel R. Southworth

2015

Overview

Significance Peroxiredoxins (Prxs) are highly abundant proteins, which serve two seemingly mutually exclusive roles as peroxidases and molecular chaperones. Little is known about the precise mechanism of Prxs’ activation as chaperone and the physiological significance of this second function. Here we demonstrate that in Leishmania infantum , reduced Prx provides a crucial, stress-specific chaperone reservoir, which is activated rapidly upon exposure to unfolding stress conditions. Once activated, Prx protects a wide range of different clients against protein unfolding. Clients are bound in the center of the decameric ring, providing experimental evidence for previous claims that Prxs serve as likely ancestors of chaperonins. Interference with client binding impairs Leishmania infectivity, providing compelling evidence for the in vivo importance of Prx’s chaperone function. Cytosolic eukaryotic 2-Cys-peroxiredoxins have been widely reported to act as dual-function proteins, either detoxifying reactive oxygen species or acting as chaperones to prevent protein aggregation. Several stimuli, including peroxide-mediated sulfinic acid formation at the active site cysteine, have been proposed to trigger the chaperone activity. However, the mechanism underlying this activation and the extent to which the chaperone function is crucial under physiological conditions in vivo remained unknown. Here we demonstrate that in the vector-borne protozoan parasite Leishmania infantum , mitochondrial peroxiredoxin (Prx) exerts intrinsic ATP-independent chaperone activity, protecting a wide variety of different proteins against heat stress-mediated unfolding in vitro and in vivo. Activation of the chaperone function appears to be induced by temperature-mediated restructuring of the reduced decamers, promoting binding of unfolding client proteins in the center of Prx’s ringlike structure. Client proteins are maintained in a folding-competent conformation until restoration of nonstress conditions, upon which they are released and transferred to ATP-dependent chaperones for refolding. Interference with client binding impairs parasite infectivity, providing compelling evidence for the in vivo importance of Prx’s chaperone function. Our results suggest that reduced Prx provides a mitochondrial chaperone reservoir, which allows L. infantum to deal successfully with protein unfolding conditions during the transition from insect to the mammalian hosts and to generate viable parasites capable of perpetuating infection.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Adenosine triphosphatase / ancestry / Animals / ATP / Binding sites / Biological Sciences / chaperonins / Enzymes / Eukaryotes / Heat tolerance / Leishmania infantum / Leishmania infantum - enzymology / Leishmania infantum - pathogenicity / Luciferases - metabolism / Mitochondria / Molecular Chaperones - metabolism / Parasites / pathogenicity / peroxiredoxin / Peroxiredoxins - metabolism / PNAS Plus / Protein Folding / protein unfolding / Proteins / Stress response / Virulence