Toll-like receptors (TLRs) are key pattern recognition receptors that mediate innate immune responses to infection. However, uncontrolled TLR activation can lead to severe inflammatory disorders such as septic shock. The molecular mechanisms through which TLR responses are regulated are not fully understood. Here, we demonstrate an essential function of S100A10 in TLR signaling. S100A10 was constitutively expressed in macrophages, but was significantly downregulated upon TLR activation. S100A10-deficient macrophages were hyperresponsive to TLR stimulation, and S100A10-deficient mice were more sensitive to endotoxin-induced lethal shock and Escherichia coli -induced abdominal sepsis. Mechanistically, S100A10 regulated macrophage inflammatory responses by interfering with the appropriate recruitment and activation of the receptor-proximal signaling components and eventually inhibited TLR-triggered downstream signaling. These findings expand our understanding of TLR signaling and establish S100A10 as an essential negative regulator of TLR function and a potential therapeutic target for treating inflammatory diseases.

TNFAIP8-like 2 (TIPE2) is a negative regulator of immune receptor signaling that maintains immune homeostasis. Dysregulated TIPE2 expression has been observed in several types of human immunological disorders. However, how TIPE2 expression is regulated remains to be determined. We report in this study that the SCF b-TrCP E3 ubiquitin ligase regulates TIPE2 protein abundance by targeting it for ubiquitination and subsequent degradation via the 26S proteasome. Silencing of either cullin-1 or b-TrCP1 resulted in increased levels of TIPE2 in immune cells. TAK1 phosphorylated the Ser 3 in the noncanonical degron motif of TIPE2 to trigger its interaction with b-TrCP for subsequent ubiquitination and degradation. Importantly, the amount of TIPE2 protein in immune cells determined the strength of TLR 4-induced signaling and downstream gene expression. Thus, our study has uncovered a mechanism by which SCF b-TrCP E3 ubiquitin ligase regulates TLR responses.

Tumor necrosis factor-α-induced protein 8 (TNFAIP8 or TIPE) is a member of the TNFAIP8 family. While TIPE was broadly considered to be pro-cancerous, its precise roles in carcinogenesis especially those of the intestinal tract are not clear. Here, we show that genetic deletion of TIPE in mice exacerbated chemical-induced colitis and colitis-associated colon cancer. Loss of TIPE exacerbated inflammatory responses and inflammation-associated dysbiosis, leading to the activation of NF-κB and STAT3, and it also accelerated dysplasia, DNA damage and proliferation of intestinal epithelial cells. We further show that colon microbiota were essential for increased tumor growth and progression in Tipe−/− mice. The tumor suppressive function of TIPE originated primarily from the non-hematopoietic compartment. Importantly, TIPE was downregulated in human colorectal cancers, and patients with low levels of Tipe mRNA were associated with reduced survival. These results indicate that TIPE serves as an important modulator of colitis and colitis-associated colon cancer.

Although increasing evidence links the gut microbiota with the development of colorectal cancer, the molecular mechanisms for microbiota regulation of tumorigenesis are not fully understood. Here, we found that a member of the TNFα-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) was significantly upregulated in murine intestinal tumors and in human colorectal cancer, and colorectal cancer with high expression of Tipe2 mRNA associated with reduced survival time of patients. Consistent with these findings, TIPE2 deficiency significantly inhibited the development of colorectal cancer in mice treated with azoxymethane/dextran sodium sulfate and in Apcmin/+ mice. TIPE2 deficiency attenuated the severity of colitis by successfully resolving and restricting colonic inflammation and protected colonic myeloid cells from death during colitis. Transplantation of TIPE2-deficient bone marrow into wild-type mice successfully dampened the latter's tumorigenic phenotype, indicating a hematopoietic-specific role for TIPE2. Mechanistically, restricting the expansion of Enterobacteriaceae/Escherichia coli (E. coli) decreased intestinal inflammation and reduced the incidence of colonic tumors. Collectively, these data suggest that hematopoietic TIPE2 regulates intestinal antitumor immunity by regulation of gut microbiota. TIPE2 may represent a new therapeutic target for treating colorectal cancer.

Supplementary Data from Tumor Necrosis Factor-α–Induced Protein 8-Like 2 Fosters Tumor-Associated Microbiota to Promote the Development of Colorectal Cancer