Expression of a Mitochondrial Peroxiredoxin Prevents Programmed Cell Death inLeishmania donovani

Abstract

Leishmania promastigote cells transmitted by the insect vector get phagocytosed by macrophages and convert into the amastigote form. During development and transformation, the parasites are exposed to various concentrations of reactive oxygen species, which can induce programmed cell death (PCD). We show that a mitochondrial peroxiredoxin (LdmPrx) protects Leishmania donovani from PCD. Whereas this peroxiredoxin is restricted to the kinetoplast area in promastigotes, it covers the entire mitochondrion in amastigotes, accompanied by dramatically increased expression. A similar change in the expression pattern was observed during the growth of Leishmania from the early to the late logarithmic phase. Recombinant LdmPrx shows typical peroxiredoxin-like enzyme activity. It is able to detoxify organic and inorganic peroxides and prevents DNA from hydroxyl radical-induced damage. Most notably, Leishmania parasites overexpressing this peroxiredoxin are protected from hydrogen peroxide-induced PCD. This protection is also seen in promastigotes grown to the late logarithmic phase, also characterized by high expression of this peroxiredoxin. Apparently, the physiological role of this peroxiredoxin is stabilization of the mitochondrial membrane potential and, as a consequence, inhibition of PCD through removal of peroxides.Leishmania parasites affect more than 12 million people worldwide, with an estimated 2 million new cases each year (WHO World Health Report, 2004, http://www.who.int/whr /en). Depending on the species involved, symptoms range from the self-healing cutaneous form (Leishmania major) to the fatal visceral form (L. donovani). The parasite is transmitted as the infective promastigote form from the gut of its insect vector, female phlebotomine flies of the genera Phlebotomus and Lutzomyia, to mammalian hosts. Promastigotes get phagocytosed by macrophages and convert into the amastigote form, which is able to survive and replicate within phagolysosomes. During phagocytosis of Leishmania promastigotes, the macrophages produce different reactive oxygen species (ROS) to kill the parasites. ROS readily react with proteins, DNA, and lipids and have been implicated in a wide variety of cell functions, such as signal transduction, redox homeostasis, apoptosis, aging, tumor progression, and pathogen infection (9,19,42,58). Numerous reports have shown that Leishmania parasites are susceptible to ROS-and RNS (reactive nitrogen species)-mediated toxicity (41, 57). In order to survive and establish an infection, they have to cope with these pro-oxidants. In Trypanosomatidae, it was shown that peroxiredoxins are the major antioxidant enzymes that can use different ROS and RNS like H 2 O 2 , hydroperoxides, and ONOO as substrates (56). Peroxiredoxins are found in a great variety of organisms, where they fulfill distinct functions, such as detoxification, signaling, or differentiation (25). In different members of the family Trypanosomatidae, cytosolic, as well as mitochondrial, peroxiredoxins were found (6,10,11,21). Peroxire...

Enzymatic Mechanism Controls Redox-mediated Protein-DNA Interactions at the Replication Origin of Kinetoplast DNA Minicircles

“…4 and 6). The intramitochondrial co-localization of a TXNPx isoform in C. fasciculata with the kDNA disk, in close proximity to UMSBP (41), similarly to its reported localization in L. infantum and L. major (35,43), is in accord with a potential functional role for TXNPx in kDNA metabolism, through its effect on the recognition of the kDNA minicircle replication origin.…”

Overexpression of MitochondrialLeishmania majorAscorbate Peroxidase Enhances Tolerance to Oxidative Stress-Induced Programmed Cell Death and Protein Damage

“…Several reports have shown that mitochondrial dysfunction or an imbalance of antioxidant homeostasis causes an increase in mitochondrion-generated ROS, which include H 2 O 2 , superoxide radical anions, singlet oxygen, and hydroxyl radicals. These species have all been implicated in apoptosis (16,26,28,41). Increasing evidence has been presented to support that ROS homeostasis regulates two major types of important physiological processes and exerts diverse functions within cells.…”

How pH Modulates the Dimer-Decamer Interconversion of 2-Cys Peroxiredoxins from the Prx1 Subfamily

“…Up-regulation of this protein has been associated with protection against apoptosis-like death (26) and resistance to miltefosine (27), a drug whose activity is linked to apoptosis and disturbance of lipiddependent cell signaling pathways (28). Moreover, Leishmania Prx1m confers thermotolerance to the parasite and displays in vitro chaperone activity, which seems to be crucial for virulence (29).…”