RESUMO
RNA helicases are ubiquitous enzymes that participate in almost all aspects of RNA processing, including RNA and RNA-protein complex remodelling. In trypanosomatids, which post-transcriptionally regulate gene expression, the formation of different kinds of ribonucleoprotein granules under stress conditions modulates the parasite's RNA metabolism. This paper describes the isolation of a putative DEVH-box RNA helicase produced by promastigotes of Leishmania braziliensis. Using a Cy3-labelled dT30 oligo, FISH showed the localization of this protein to mRNA granules under starvation stress conditions. The central region of the protein was shown to be responsible for this behaviour.
Assuntos
Grânulos Citoplasmáticos/enzimologia , Leishmania braziliensis/enzimologia , Leishmania braziliensis/genética , RNA Helicases/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Estrutura Secundária de Proteína , Transporte Proteico , RNA Helicases/química , RNA Helicases/genética , RNA Helicases/isolamento & purificação , RNA Mensageiro/metabolismo , Estresse Fisiológico/genéticaRESUMO
BACKGROUND: Trypanosoma cruzi, the etiological agent of Chagas' disease, is an obligate intracellular parasite which induces a CD8+ T cell immune response with secretion of cytokines and release of cytotoxic granules. Although an immune-suppressive effect of T. cruzi on the acute phase of the disease has been described, little is known about the capacity of CD8+ T cell from chronic chagasic patients to respond to a non-T. cruzi microbial antigen. METHODS: In the present paper, the frequency, phenotype and the functional activity of the CD8+ T cells specific from Flu-MP*, an influenza virus epitope, were determined in 13 chagasic patients and 5 healthy donors. RESULTS: The results show that Flu-MP* peptide specific CD8+ T cells were found with similar frequencies in both groups. In addition, Flu-MP* specific CD8+ T cells were distributed in the early or intermediate/late differentiation stages without showing enrichment of a specific sub-population. The mentioned Flu-MP* specific CD8+ T cells from chagasic patients were predominately TEM (CCR7- CD62L-), producing IL-2, IFNγ, CD107a/b and perforin, and did not present significant differences when compared with those from healthy donors. CONCLUSIONS: Our results support the hypothesis that there is no CD8+ T cell nonspecific immune-suppression during chronic Chagas disease infection. Nonetheless, other viral antigens must be studied in order to confirm our findings.