Downregulation of Tra2α and Tra2β suppresses lipopolysaccharide-induced inflammation in macrophages by regulating MyD88 mRNA alternative splicing.

RNA binding proteins (RBPs) play a pivotal role in the posttranscriptional regulation of inflammatory processes. Transformer-2 (Tra2) is an evolutionarily conserved RBP that regulates mRNA alternative splicing, encoding two homologous proteins in vertebrates, Tra2α and Tra2β. Dysregulation of Tra2α or Tra2β may lead to the development of several inflammatory diseases. However, the roles of Tra2α and Tra2β in inflammation remain unclear. In the current research, the expression levels of Tra2α and Tra2β were upregulated in RAW264.7 macrophage cells stimulated by lipopolysaccharide (LPS). Downregulation of Tra2α or Tra2β inhibited the expression of inflammatory factors induced by LPS. Notably, combined suppression of Tra2α and Tra2β cooperatively reduced LPS-activated inflammation and suppressed the activation of NFκB and MAPK pathways. Myeloid differentiation primary response gene 88 (MyD88), a crucial adaptor in the TLR4 pathway, expresses splicing variants MyD88-L and MyD88-S, which exert pro-inflammatory and anti-inflammatory effects, respectively. We found that Tra2α and Tra2β proteins interacted with MyD88 mRNA. Moreover, downregulation of Tra2α and Tra2β promoted the expression of MyD88-S mRNA variants, thereby modulating the inflammatory response. Therefore, our findings demonstrated that Tra2α and Tra2β cooperatively regulated inflammation by modulating the alternative splicing of MyD88 in LPS-stimulated macrophages. These mechanistic insights into Tra2-mediated regulation of macrophage inflammation may provide novel therapeutic targets for treating inflammatory diseases.