EST12 regulates Myc expression and enhances anti-mycobacterial inflammatory response via RACK1-JNK-AP1-Myc immune pathway

Abstract

c-Myc (Myc) is a well-known transcription factor that regulates many essential cellular processes. Myc has been implicated in regulating anti-mycobacterial responses. However, its precise mechanism in modulating mycobacterial immunity remains elusive. Here, we found that a secreted Rv1579c (early secreted target with molecular weight 12 kDa, named EST12) protein, encoded by virulent <i>Mycobacterium tuberculosis</i> (<i>M.tb</i>) H37Rv region of deletion (RD)3, induces early expression and late degradation of Myc protein. Interestingly, EST12-induced Myc was further processed by K48 ubiquitin proteasome degradation in E3 ubiquitin ligase FBW7 dependent manner. EST12 protein activates JNK-AP1-Myc signaling pathway, promotes Myc binding to the promoters of IL-6, TNF-α and iNOS, then induces the expression of pro-inflammatory cytokines (IL-6 and TNF-α)/inducible nitric oxide synthase (iNOS)/nitric oxide (NO) to increase mycobacterial clearance in a RACK1 dependent manner, and these effects are impaired by both Myc and JNK inhibitors. Macrophages infected with EST12-deficiency strain (H37RvΔEST12) displayed less production of iNOS, IL-6 and TNF-α. In conclusion, EST12 regulates Myc expression and enhances anti-mycobacterial inflammatory response <i>via</i> RACK1-JNK-AP1-Myc immune pathway. Our finding provides new insights into <i>M.tb</i>-induced immunity through Myc.