The Alternative Polyadenylation Factor CFIm25 Orchestrates Macrophage Antibacterial Immunity by Amplifying TAB2-Mediated MAPK and NF-κB Signaling During Salmonella Infection

Abstract

Macrophage antimicrobial programs are regulated not only by transcriptional networks but also by RNA processing mechanisms affecting signal transduction and effector responses. One such mechanism, alternative polyadenylation (APA), determines mRNA fate by changing the length of the 3' UTR. However, our understanding of the impact of APA on antibacterial functions and how we can manipulate it to influence infection outcomes remains limited. In this study, we identify the APA regulator CFIm25 (NUDT21) as a promoter of macrophage defense against Salmonella enterica serovar Typhimurium (STM). STM infection is known to drive macrophages toward an M2-like immunosuppressive state conducive to bacterial survival. Concurrent with this transition, the CFIm25 level is reduced, and the 3 UTRs of CFIm25 targets encoding key immune proteins, such as TAB2 and TBL1XR1, are lengthened, suggesting a role for APA changes in the response to STM. Overexpression of CFIm25 in infected macrophages blocks these Salmonella-induced 3 UTR changes, leading to greater mRNA and protein expression. Significantly, the increase in CFIm25 suppresses infection, thereby creating a more antimicrobial intracellular environment, improving macrophage survival, and reducing M2 properties that support bacterial replication. Specifically, CFIm25 enhances production of the antibacterial peptide LL-37, increases reactive oxygen species and nitric oxide levels, suppresses arginase activity and lactate production, and stimulates release of pro-inflammatory cytokines while inhibiting anti-inflammatory cytokines. Depletion studies show TAB2 mediates CFIm25s antibacterial effects by activating both MAPK and NF-kB pathways. Our findings highlight APA regulation as a potential target for boosting immune defenses and developing treatments for chronic bacterial infections.