Circular RNA TRAPPC6B Inhibits Intracellular Mycobacterial Growth While Inducing Autophagy in Macrophages by Targeting microRNA-874-3p

Abstract

Background: Genetic and epigenetic mechanisms appear to regulate antimicrobial immunity against Mycobacterium tuberculosis (Mtb) infection. Methods: We assessed circular RNA TRAPPC6B (circTRAPPC6B) for antimicrobial immune functions and defined mechanisms whereby circTRAPPC6B regulates Mtb growth, autophagy and microRNA in macrophages. Findings: While Mtb infection of monocytes/macrophages resulted in a significantly decreased circTRAPPC6B level, circTRAPPC6B inhibited intracellular Mtb growth in macrophages. Whereas, circTRAPPC6B expression enhanced autophagy or autophagy-associated protein LC3-II production in Mtb-infected macrophages. The circTRAPPC6B-enhanced autophagy aggregation or sequestration was also observed in FISH analysis and confocal imaging. Mechanistically, circTRAPPC6B could target an inhibiting element miR-874-3p, as evidenced by bioinformatics, dual-luciferase reporter gene analysis, and pull-down assay, respectively. Notably, miR-874-3p prohibited autophagy via suppression of autophagy protein ATG16L1 expression by binding to its 3’-UTRin Mtb-infected macrophages and thus promoted intracellular Mtb growth. Concurrently, circTRAPPC6B enhanced autophagy in Mtb-infected macrophage by blocking the ability of miR-874-3p to inhibit ATG16L1. Thus, circTRAPPC6B can antagonize the ability of miR-874-3p to suppress ATG16L1 expression, and activate and enhance autophagy sequestration to restrict Mtb growth in macrophages. Interpretation: Our findings suggest that both circTRAPPC6B and miR-874 mechanisms can be explored as potential therapeutics against Mtb infection. Funding: This work was supported by the National Natural Science Foundation of China (881870016, 1570009 and 81273237), the Natural Science Foundation of Guangdong Province (2015A030313513 and 2020A1515010283), and the Science and Technology Innovation Fund of Guangdong Medical University (STIF201110, B2012078). Declaration of Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ethics Approval Statement: The protocol of using human blood samples in vitro was approved by the Institutional Review Boards for Human Donors’ Research and Institutional Biosafety Committees at Institut Pasteur of Shanghai, Guangdong Medical University, and Dongguan 6th Hospital (China). The protocols of using macaque spleen tissue samples and mycobacterium H37Rv strain were approved by the Institutional Review Boards for Biosafety Committee at the University of Illinois–Chicago College of Medicine (IL, USA). All studies complied with the guidelines of the Office for Human Research Protections. All patients and healthy controls provided written informed consent before initiation of study.