MicroRNA-17-5p Modulates Bacille Calmette-Guerin Growth in RAW264.7 Cells by Targeting ULK1.

Xiangguo Duan,Tao Zhang,Guangxian Xu,Shuqin Ding,Jun Wei,Hongpeng Liu,Chunxia Su,Klaus Roemer

doi:10.1371/journal.pone.0138011

Abstract

To explore the potential roles of miRNAs in controlling the survival of mycobacteria in macrophages, miR-17-5p in the regulation of Bacillus Calmette-Guérin(BCG)growth in the macrophage RAW264.7 cells was interrogated. Our results reveal that an infection of BCG shows a time-dependent up-regulation of miR-17-5p in RAW264.7 cells in early phase; importantly, excessive expression of miR-17-5p in these cells exhibits an increased propagation of intracellular BCG. Mechanistically, the Unc-51 like autophagy activating kinase 1 (ULK1), an initial molecular of autophagy are identified as novel target of miR-17-5p, the miR-17-5p is capable of targeting down-regulating the expression of ULK1 protein. In addition, an overexpression of miR-17-5p in RAW264.7 cells is correlated with repression of ULK1 and the autophagosome related proteins LC3I/II. These results imply that miR-17-5p may be able to arrest the maturation of mycobacterial phagosomes in part by targeting ULK1, subsequently reduces the ability of host cells to kill intracellular BCG.

Highlights

MicroRNAs are evolutionarily conserved, endogenous, single-stranded, noncoding RNA molecules with approximately of ~22 nt length of which function as post transcriptional regulators by pairing to the 3' untranslated region (UTR) of target mRNAs, subsequently inhibit the translations of mRNA [1,2,3]
We explore the potential role of miR-17-5p in alveolar macrophages in response to BCG infection, we found that the infection of BCG induces a up-regulation of miR-17-5p in macrophage RAW264.7 cells in early phase, and inhibition of miR-17 transcript increases the abundance of Unc-51 like autophagy activating kinase 1 (ULK1) and LC3I/II protein, and improves the capacity to kill the intracellular bacilli in macrophages
Alveolar macrophages are main targets of Mycobacterium tuberculosis (Mtb) infection, and the pattern of cell death of Mtb-infected alveolar macrophages has been recognized to play a central role in the pathogenesis of tuberculosis (TB) [32]

Summary

Introduction

MicroRNAs (miRNAsor miR) are evolutionarily conserved, endogenous, single-stranded, noncoding RNA molecules with approximately of ~22 nt length of which function as post transcriptional regulators by pairing to the 3' untranslated region (UTR) of target mRNAs, subsequently inhibit the translations of mRNA [1,2,3]. These studies suggest that the miRNAs and inflammatory signaling molecules can create a fine-tuned feedback loop to regulate immune responses in hosts. The miR-17-92 cluster has shown functions of oncogenes by regulating cell proliferation, apoptosis and development [14,15]. Owing to an increasingly appreciated importance of miRNA families, the functions of miR-17-92 cluster have been intensively characterized, by which these miRNAs have shown an essential role in tumorigenesis and normal development of organs including the heart, lungs, and immune system [16,17,18,19], and regulation of immune response to an pathogen infection [20,21]

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Results

Conclusion