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      Leishmania (Viannia) panamensis expresses a nuclease with molecular and biochemical features similar to the Endonuclease G of higher eukaryotes Translated title: Leishmania (Viannia) panamensis expresa una nucleasa molecular y bioquímicamente similar a la Endonucleasa G de eucariotas superiores

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          Abstract

          Objetivo: Caracterizar molecular y bioquímicamente la Endonucleasa G (EndoG) de Leishmania (Viannia) panamensis. Métodos: El gen de la putativa Endonucleasa G de L. (V.) panamensis fue amplificado, clonado y secuenciado. La proteína recombinante se produjo en un sistema de expresión heterólogo y la proteína activa se sometió a pruebas bioquímicas para determinar la preferencia de iones, temperatura y pH. Resultados: La rEndoG de L. (V.) panamensis muestra características bioquímicas similares a aquellas descritas en otros trypanosomatidos y en eucariotas superiores. Además, los análisis filogenéticos muestran una posible relación evolutiva con la Endonucleasa G de metazoos. Conclusiones: Leishmania (V.) panamensis posee un gen que codifica para una endonucleasa homóloga a la EndoG de otros organismos superiores, que se puede producir de forma recombinante en Escherichia coli y que es capaz de degradar ADN circular cerrado de doble cadena. Tiene una preferencia por los iones magnesio y manganeso para usarlos como cofactor y es inhibida por el potasio. Además, funciona en un amplio rango de pH y temperatura.

          Translated abstract

          Objective: To characterize the molecular and biochemical features of the Endonuclease G of Leishmania (Viannia) panamensis. Methods: The gene of the putative L. (V.) panamensis Endonuclease G was amplified, cloned, and sequenced. The recombinant protein was produced in a heterologous expression system and biochemical assays were run to determine its ion, temperature, and pH preferences. Results: The L. (V.) panamensis rENDOG has biochemical features similar to those found in other trypanosomatids and higher eukaryotes. In addition, phylogenetic analysis revealed a possible evolutionary relationship with metazoan ENDOG. Conclusions: L. (V.) panamensis has a gene that codifies an ENDOG homologous to those of higher organisms. This enzyme can be produced in Escherichia coli and is able to degrade covalently closed circular double-stranded DNA. It has a magnesium preference, can be inhibited by potassium, and is able to function within a wide temperature and pH range.

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          Endonuclease G is an apoptotic DNase when released from mitochondria.

          Nucleosomal fragmentation of DNA is a hallmark of apoptosis (programmed cell death), and results from the activation of nucleases in cells undergoing apoptosis. One such nuclease, DNA fragmentation factor (DFF, a caspase-activated deoxyribonuclease (CAD) and its inhibitor (ICAD)), is capable of inducing DNA fragmentation and chromatin condensation after cleavage by caspase-3 (refs 2,3,4). However, although transgenic mice lacking DFF45 or its caspase cleavage site have significantly reduced DNA fragmentation, these mice still show residual DNA fragmentation and are phenotypically normal. Here we report the identification and characterization of another nuclease that is specifically activated by apoptotic stimuli and is able to induce nucleosomal fragmentation of DNA in fibroblast cells from embryonic mice lacking DFF. This nuclease is endonuclease G (endoG), a mitochondrion-specific nuclease that translocates to the nucleus during apoptosis. Once released from mitochondria, endoG cleaves chromatin DNA into nucleosomal fragments independently of caspases. Therefore, endoG represents a caspase-independent apoptotic pathway initiated from the mitochondria.
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            A natural model of Leishmania major infection reveals a prolonged "silent" phase of parasite amplification in the skin before the onset of lesion formation and immunity.

            A model of Leishmania major infection in C57BL/6 mice has been established that combines two main features of natural transmission: low dose (100 metacyclic promastigotes) and inoculation into a dermal site (the ear dermis). The evolution of the dermal lesion could be dissociated into two distinct phases. The initial "silent" phase, lasting 4-5 wk, favored establishment of the peak load of parasites in the dermis in the absence of lesion formation or any overt histopathologic changes in the site. The second phase corresponds to the development of a lesion associated with an acute infiltration of neutrophils, macrophages, and eosinophils into the dermis and was coincident with the killing of parasites in the site. The onset of immunity/pathology was correlated with the appearance of cells staining for IL-12p40 and IFN-gamma in the epidermal compartment, and an expansion of T cells capable of producing IFN-gamma in the draining lymph node. Parasite growth was not enhanced over the first 4.5 wk in anti-CD4-treated mice, SCID mice, or C57BL/6 mice deficient in IL-12p40, IFN-gamma, CD40 ligand, or inducible NO synthase. These mice all failed to ultimately control infection in the site, but in some cases (anti-CD4 treated, IL-12p40-/-, CD40 ligand-/-, and SCID) high dermal parasite loads were associated with little or no pathology. These results extend to a natural infection model a role for Th1 cells in both acquired resistance and lesion formation, and document the remarkable avoidance of this response during a prolonged phase of parasite amplification in the skin.
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              Leishmania disease development depends on the presence of apoptotic promastigotes in the virulent inoculum.

              The obligate intracellular pathogen Leishmania major survives and multiplies in professional phagocytes. The evasion strategy to circumvent killing by host phagocytes and establish a productive infection is poorly understood. Here we report that the virulent inoculum of Leishmania promastigotes contains a high ratio of annexin A5-binding apoptotic parasites. This subpopulation of parasites is characterized by a round body shape, a swollen kinetoplast, nuclear condensation, and a lack of multiplication and represents dying or already dead parasites. After depleting the apoptotic parasites from a virulent population, Leishmania do not survive in phagocytes in vitro and lose their disease-inducing ability in vivo. TGF-beta induced by apoptotic parasites is likely to mediate the silencing of phagocytes and lead to survival of infectious Leishmania populations. The data demonstrate that apoptotic promastigotes, in an altruistic way, enable the intracellular survival of the viable parasites.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                cm
                Colombia Médica
                Colomb. Med.
                Facultad de Salud, Universidad del Valle, Cali, Colombia (Cali )
                1657-9534
                June 2011
                : 42
                : 2
                : 154-165
                Affiliations
                [1 ] Universidad de Antioquia Colombia
                [2 ] Universidad de Antioquia Colombia
                [3 ] Universidad de Antioquia Colombia
                [4 ] Universidad de Alcalá Spain
                [5 ] Universidad de Antioquia Colombia
                Article
                S1657-95342011000200004
                2915e893-e33b-43e4-b816-a54c2c44acce

                http://creativecommons.org/licenses/by/4.0/

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                SciELO Colombia

                Self URI (journal page): http://www.scielo.org.co/scielo.php?script=sci_serial&pid=1657-9534&lng=en
                Categories
                MEDICINE, GENERAL & INTERNAL

                Internal medicine
                Leishmania panamensis,Endonucleasa G,Caracterización molecular,Proteínas recombinantes,Renaturalización,Filogenia,Endonuclease G,Molecular characterization,Recombinant proteins,Refolding; Phylogeny

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