Work

Manipulation of cysteine cathepsins during Mycobacterium tubersulosis infection of human macrophages

Year: 2013

Type: dissertation

Abstract: Mycobacterium tuberculosis (Mtb), the main causative agent of tuberculosis, is among the world’s most ancient and most successful pathogens. Its success can be attributed to its ability to avoid phagosomal destruction, survive and proliferate inside its host cells, of which the most important are the human macrophages. Besides being able to block phagosome-lysosome fusion, Mtb is able to inhibit the expression of lysosomal hydrolases, such as cathepsins. Cathepsins are a major class of lysosomal enzymes which have various functions. One in particular, cathepsin S, has been deeply implicated in peptide processing for antigen presentation, assuming in this way an important role in mediating the innate and adaptive immune responses to external invaders in the human body. In this work we analyzed a putative cathepsin gene regulation mechanism employed by Mtb, making use of miRNAs, small RNAs which post-transcriptionally regulate gene expression. The first part of this work was dedicated to unraveling the effect of Mtb in the expression of cathepsin S and the candidate regulator miRNA-106b-5p (miR-106b-5p) in the context of macrophage infection. We have determined that miR-106b-5p is up-regulated, while cathepsin S is down-regulated during Mtb infection of macrophages, in contrast with the non-pathogenic M. smegmatis which seems to have no effect in either. Bioinformatics data point out that the cathepsin S gene (CtsS) is a target for miR-106b-5p. As such, in the second part of this thesis we experimentally tested this hypothesis. First, the transfection of THP-1 cell line with miR-106b-5p mimics resulted in a decrease of cathepsin S, but not as exacerbated as we expected. The same effect has been reported for proteins that were shown to be very stable along time. Secondly, by using luciferase expression vectors and subsequent luciferase activity assays, we showed that the mRNA of CtsS is indeed a target for miR-106b-5p. Altogether, our results indicate that Mtb inhibits cathepsin S expression via miR-106b-5p up-regulation, during macrophage infection.

Source: Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT)

Author: João Palma Neves Pombo

Language: English

Topic: Tuberculosis Research and Epidemiology

Subfield: Infectious Diseases

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green

Funder: Fundação para a Ciência e a Tecnologia

Awards: Papel do M. tuberculosis no controlo por microRNAs da filamentação de actina e outros sinais pró-inflamatórios em macrófagos infectados., Dissecação dos factores de tráfego intracelular envolvidos na morte /sobrevivência do M. tuberculosis em macrófagos humanos usando interferência por RNA.

OpenAlex ID: W179111937

Cites: 45

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Related to: 10