Mycobacterium tuberculosis Rv3248c Inhibits Type I Interferon Response and Promotes Intracellular Survival by Mediating Ubiquitin-Proteasome-Dependent Degradation of TBK1

Abstract

Mycobacterium tuberculosis (M. tb) is a leading cause of infectious disease mortality worldwide, and M. tb subverts host immunity to persist intracellularly. Type I interferon (IFN-I) modulates host defense during M. tb infection, but the mechanisms controlling their induction remain incompletely defined. In this research, a previously uncharacterized mycobacterial factor, M. tb Rv3248c, which regulates IFN-I response, was identified using pull-down and mass spectrometry. Overexpression of Rv3248c suppresses IFN-β expression in macrophages at both the transcriptional and protein levels. In addition, it also enhances intracellular bacterial load, whereas in bone marrow-derived macrophages (BMDMs) from Ifnar1^–/– C57BL/6 mice, the difference of bacterial load was no longer statistically significant, suggesting that Rv3248c enhances mycobacterial survival in IFN-I-dependent manner. Furthermore, the study shows that M. tb Rv3248c inhibits IFN-I response via the cGAS-STING pathway. Mechanistically, Rv3248c binds TANK-binding kinase 1 (TBK1) and promotes its ubiquitination-mediated proteasomal degradation. The N-terminal region of Rv3248c (amino acids 1–134) is required for TBK1 interaction and IFN-I inhibition. These findings identify a previously uncharacterized mechanism by which M. tb dampens the IFN-I response by targeting TBK1, highlighting Rv3248c as a contributor to pathogenesis and a potential therapeutic target.