Multifaceted Roles of microRNAs in Host-Bacterial Pathogen Interaction

Abstract

MicroRNAs (miRNAs) are a well-characterized class of small noncoding RNAs that act as major posttranscriptional regulators of gene expression. Accordingly, miRNAs have been associated with a wide range of fundamental biological processes and implicated in human diseases. During the past decade, miRNAs have also been recognized for their role in the complex interplay between the host and bacterial pathogens, either as part of the host response to counteract infection or as a molecular strategy employed by bacteria to subvert host pathways for their own benefit. Importantly, the characterization of downstream miRNA targets and their underlying mechanisms of action has uncovered novel molecular factors and pathways relevant to infection. In this article, we review the current knowledge of the miRNA response to bacterial infection, focusing on different bacterial pathogens, including Salmonella enterica, Listeria monocytogenes, Mycobacterium spp., and Helicobacter pylori, among others.

FIGURE 1

Overview of the canonical miRNA biogenesis pathway. miRNA genes are transcribed as pri-miRNAs by RNA polymerase II. The main proteins involved in the multistep miRNA processing are indicated. Repression of target gene expression occurs through inhibition of translation and mRNA degradation.

FIGURE 2

Regulation of miRNAs upon infection by bacterial pathogens impacts multiple crucial host cell functions. miRNA modulation upon infection has been shown to be an integral part of the host response or a mechanism exploited by bacteria to promote infection.

FIGURE 3

Mycobacterium spp.-induced miRNA changes have a strong impact on autophagy. The autophagic flux is controlled by multiple miRNAs that are regulated as a consequence of mycobacterial infection. Most studies report that miRNA modulation inhibits specific steps of the autophagy pathway, thus impairing bacterial degradation.