Early Secreted Antigen ESAT-6 of Mycobacterium Tuberculosis Promotes Apoptosis of Macrophages via Targeting the MicroRNA155-SOCS1 Interaction

Abstract

Background: The early secreted antigenic target 6-kDa protein (ESAT-6) of Mycobacterium tuberculosis (Mtb) not only acts as a key player for virulence but also exhibits a strong immunotherapeutic potential against Mtb. However, little is known about the molecular basis for its potential in immunotherapy. The present study was designed to unravel the role of miRNA-155 in ESAT-6-mediated enhancement of host immunity and apoptosis in macrophages. Methods: Lentivirus-mediated miR-155 sponge and miR-155 and SOCS1 overexpression vectors were developed in macrophages. TLR2- or p65-specific siRNA knockdown was employed to silence TLR2 or p65. Quantitative polymerase chain reaction and western blotting analyses were performed to determine mRNA and protein expression levels, respectively. Macrophage apoptosis was analyzed by flow cytometry. Results: ESAT-6 significantly increased miR-155 expression, which was dependent on TLR2/NF-κB activation in macrophages. Induced expression of miRNA-155 was required for the ESAT-6-mediated protective immune response and macrophage apoptosis. ESAT-6 promoted macrophage apoptosis by targeting the miR-155-SOCS1 pathway. The differential expression levels of TLR2, BIC, and SOCS1 were involved in regulating the immune response in human peripheral blood mononuclear cells of patients with active tuberculosis (TB) and latent TB (LTB). Conclusion: ESAT-6 promotes apoptosis of macrophages via targeting the miRNA155-SOCS1 interaction.

MiR-155–regulated molecular network orchestrates cell fate in the innate and adaptive immune response to Mycobacterium tuberculosis

“…Previous studies examining the role of miR-155 in regulating macrophage responses to mycobacteria in vitro have generated widely varying results. This discordance is likely due to the use of macrophage-like cell lines instead of primary macrophages, avirulent bacillus Calmette-Guérin instead of virulent Mtb, and widely differing in vitro experimental conditions (24)(25)(26)(27)(28). A recent study demonstrated that miR-155 −/− mice are more susceptible to Mtb infection during the late chronic stage of infection (18); however, the mechanism underlying this effect was not explored.…”

“…To assess the role of miRNAs in the regulation of the innate immune response, we characterized the transcriptional response of bone marrow-derived macrophages (BMMs) at 4,8,24, and 48 h following infection with Mtb and selected 3,473 differentially expressed genes based on the following criteria: Benjamini-Hochberg corrected Student's t test P value ≤ 0.05 and fold-change ≥ 2 (Fig. S1).…”

“…The 3,473 genes significantly differentially expressed (Benjamini-Hochberg corrected Student's t test P value ≤ 0.05 and fold-change ≥ 2) between 0 h and each time point (4,8,24, and 48 h) were used for gene regulatory network construction (Table S1). The gene regulatory network was constructed using the cMonkey biclustering algorithm (7,32) that trained biclusters that correlate with miRNA-mediated regulation using the FIRM (6).…”

MicroRNA-155-5p in pathogenesis of cancer

“…Показано, что у человека измене-ние пути TLR2→miR-155→SOCS1 связано с формиро-ванием иммунного ответа с участием мононуклеарных клеток периферической крови [8]. У больных туберку-лезом белок ESAT-6 (early secreted antigenic target 6-kDa protein), продуцируемый Mycobacterium tuberculosis (Mtb) снижает иммунорективность, воздействуя на данный путь, что приводит к усилению апоптоза макрофагов [27].…”

Zymosan-a Protects the Hematopoietic System from Radiation-Induced Damage by Targeting TLR2 Signaling Pathway

“…Toll-like receptors(TLRs) have an essential role in the progress of innate immune responses [10-13]. In 2008, Burdelya et al reported that the agonist of TLR5 exerted strong radioprotective effects on mice [14].…”