RESUMO
The trace element selenium is found in polypeptides as selenocysteine, the 21(st) amino acid that is co-translationally inserted into proteins at a UGA codon. In proteins, selenocysteine usually plays a role as an efficient redox catalyst. Trypanosomatids previously examined harbor a full set of genes encoding the machinery needed for selenocysteine biosynthesis and incorporation into three selenoproteins: SelK, SelT and, the parasite-specific, Seltryp. We investigated the selenoproteome of kinetoplastid species in recently sequenced genomes and assessed the in vivo relevance of selenoproteins for African trypanosomes. Database mining revealed that SelK, SelT and Seltryp genes are present in most kinetoplastids, including the free-living species Bodo saltans, and Seltryp was lost in the subgenus Viannia from the New World Leishmania. Homology and sinteny with bacterial sulfur dioxygenases and sulfur transferases suggest a putative role for Seltryp in sulfur metabolism. A Trypanosoma brucei selenocysteine synthase (SepSecS) null-mutant, in which selenoprotein synthesis is abolished, displayed similar sensitivity to oxidative stress induced by a short-term exposure to high concentrations of methylglyoxal or H2O2 to that of the parental wild-type cell line. Importantly, the infectivity of the SepSecS knockout cell line was not impaired when tested in a mouse infection model and compensatory effects via up-regulation of proteins involved in thiol-redox metabolism were not observed. Collectively, our data show that selenoproteins are not required for survival of African trypanosomes in a mammalian host and exclude a role for selenoproteins in parasite antioxidant defense and/or virulence. On this basis, selenoproteins can be disregarded as drug target candidates.
Assuntos
Kinetoplastida/metabolismo , Proteínas de Protozoários/genética , Selenocisteína/metabolismo , Selenoproteínas/genética , Transferases/genética , Trypanosoma brucei brucei/metabolismo , Animais , Mineração de Dados , Bases de Dados Genéticas , Deleção de Genes , Regulação da Expressão Gênica , Interações Hospedeiro-Parasita , Peróxido de Hidrogênio/farmacologia , Kinetoplastida/classificação , Kinetoplastida/efeitos dos fármacos , Kinetoplastida/crescimento & desenvolvimento , Camundongos , Filogenia , Proteoma/genética , Proteoma/metabolismo , Proteínas de Protozoários/metabolismo , Aldeído Pirúvico/farmacologia , Selenoproteínas/deficiência , Transferases/deficiência , Trypanosoma brucei brucei/classificação , Trypanosoma brucei brucei/efeitos dos fármacos , Trypanosoma brucei brucei/crescimento & desenvolvimento , Tripanossomíase Africana/parasitologia , Tripanossomíase Africana/patologiaRESUMO
From the clinical and genetic point of view, congenital muscular dystrophies (CMD) are a heterogenic group of diseases within neuromuscular pathologies. The best known forms are: merosin deficiency CMD, collagen VI deficiency CMD, LMNA-related CMD, selenoprotein-related CMD (SEPN1) and alpha-dystroglycan-related CMD. They present with a broad spectrum of clinical phenotypes. Most of them are transmitted by recessive autosomal inheritance. The initial manifestations very often begin in infancy or in the neonatal period. There are clinical suspicions of the existence of hypotonia and paresis, and they are characterised by a dystrophic pattern in the muscular biopsy (muscle replaced by fibroadipose tissue, with necrosis and cell regeneration). Advances in the understanding of the molecular pathogenesis of CMD have made it possible to make further progress in the classification of the different subtypes. The aim of this review is to comment on the advances made in recent years as regards the classification of CMD in terms of genetics, the proteins involved and their clinical presentation.
TITLE: Distrofias musculares congenitas en el niño.Las distrofias musculares congenitas (DMC) representan desde el punto de vista clinico y genetico un grupo heterogeneo de enfermedades dentro de la patologia neuromuscular. Las formas mas conocidas son: DMC por deficit de merosina, DMC por deficit de colageno VI, DMC relacionada con LMNA, DMC relacionada con selenoproteina (SEPN1) y las DMC vinculadas a los alfa-distroglicanos. Se presentan con un amplio espectro de fenotipos clinicos. En su mayoria son de herencia autosomica recesiva. Con mucha frecuencia las manifestaciones iniciales comienzan en la infancia o en el periodo neonatal. Se sospechan clinicamente por la existencia de hipotonia y paresia y se caracterizan por la existencia de un patron distrofico en la biopsia muscular (sustitucion de musculo por tejido fibroadiposo, con necrosis y regeneracion celular). Avances en la comprension de la patogenesis molecular de las DMC han permitido profundizar en la clasificacion de los diferentes subtipos. El objetivo de esta revision es comentar los avances de los ultimos años en cuanto a la clasificacion de las DMC en relacion a la genetica, las proteinas involucradas y su presentacion clinica.