Inhibition of SPI1 by ADAP Regulates S100A8/A9 Signaling in Macrophages to Control the Development of Colitis.

Although the immune adaptor protein ADAP (adhesion and degranulation adaptor protein) plays a critical role in regulating macrophage inflammatory responses, its impact on intestinal inflammation remains elusive. This study reveals that ADAP-deficient mice have increased susceptibility to dextran sulfate sodium (DSS)-induced colitis and intestinal inflammation due to upregulation of S100A8/A9 expression (also known as MRP8 and MRP14, respectively) both in vivo and in vitro. Mechanistically, ADAP promotes proteasomal degradation of the transcription factor SPI1 (SPI-1 proto-oncogene) via the E3 ubiquitin ligase FBXW7 (F-box and WD repeat domain-containing 7)-mediated ubiquitination. ADAP deficiency increases SPI1 expression for transcription of the S100A8/A9 promoter. Blockade of SPI1 effectively prevents colitis-induced S100A8/A9 upregulation in macrophages. Thus, our findings highlight the potential link between ADAP and intestinal inflammation, while also paving the way for therapeutic interventions targeting the ADAP-SPI1-S100A8/A9 signaling axis in inflammatory colitis.