AZI2 mediates TBK1 activation at unresolved selective autophagy cargo receptor complexes with implications for CD8 T-cell infiltration in breast cancer

Most breast cancers do not respond to immune checkpoint inhibitors and there is an urgent need to identify novel sensitization strategies. Herein, we uncovered that activation of the TBK-IFN pathway that is mediated by the TBK1 adapter protein AZI2 is a potent strategy for this purpose. Our initial observations showed that RB1CC1 depletion leads to accumulation of AZI2, in puncta along with selective macroautophagy/autophagy cargo receptors, which are both required for TBK1 activation. Specifically, disrupting the selective autophagy function of RB1CC1 was sufficient to sustain AZI2 puncta accumulation and TBK1 activation. AZI2 then mediates downstream activation of DDX3X, increasing its interaction with IRF3 for transcription of pro-inflammatory chemokines. Consequently, we performed a screen to identify inhibitors that can induce the AZI2-TBK1 pathway, and this revealed Lys05 as a pharmacological agent that induced pro-inflammatory chemokine expression and CD8+ T cell infiltration into tumors. Overall, we have identified a distinct AZI2-TBK1-IFN signaling pathway that is responsive to selective autophagy blockade and can be activated to make breast cancers more immunogenic.Abbreviations: AZI2/NAP1: 5-azacytidine induced 2; CALCOCO2: calcium binding and coiled-coil domain 2; DDX3X: DEAD-box helicase 3 X-linked; FCCP: carbonyl cyanide p-triflouromethoxyphenylhydrazone; a protonophore that depolarizes the mitochondrial inner membrane; ICI: immune checkpoint inhibitor; IFN: interferon; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SQSTM1/p62: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1.

AZI2 positively regulates the induction of type I interferon in influenza-trigger pediatric pneumonia

5-azacytidine-induced protein 2 (AZI2) is known to have a crucial role in antiviral innate immunity. This study aims to explore the roles of AZI2 in influenza-trigger pediatric pneumonia and its molecular mechanism. qPCR and immunoblotting assays were used to determine the levels of target genes and proteins. The lung infection mouse model was established by using PR8 H1N1 virus in AZI2 germline knockout (AZI2-/-) and wide-type (WT) mice. In addition, HEK293T cell-based luciferase reporter assays were used to investigate the regulatory effects of AZI2 on type I interferon. Immune precipitation and immunofluorescence staining were used to evaluate the interactions between AZI2 and TANK binding kinase 1 (TBK1). We observed an elevation in the expressions of IFN-I and AZI2 in peripheral blood mononuclear cells from the pneumonia patients with mild symptoms. Interestingly, AZI2 deficiency deteriorated the influenza-induced pathological symptoms in the lung as well as reduced the survival rate. It was further showed that AZI2 positively regulated the expressions of type I interferon, inflammatory cytokines, and IFN production-related genes. The molecular mechanism data revealed that AZI2 regulated the interactions between TBK1 and TANK. In summary, AZI2 positively regulates type I interferon production in influenza-induced pediatric pneumonia by promoting the interactions between TBK1 and TANK.

5-Azacytidine-induced protein 2 (AZI2) regulates bone mass by fine-tuning osteoclast survival

5-Azacytidine-induced protein 2 (AZI2) is a TNF receptor (TNFR)-associated factor family member-associated NF-κB activator-binding kinase 1-binding protein that regulates the production of IFNs. A previous in vitro study showed that AZI2 is involved in dendritic cell differentiation. However, the roles of AZI2 in immunity and its pleiotropic functions are unknown in vivo. Here we report that AZI2 knock-out mice exhibit normal dendritic cell differentiation in vivo. However, we found that adult AZI2 knock-out mice have severe osteoporosis due to increased osteoclast longevity. We revealed that the higher longevity of AZI2-deficient osteoclasts is due to an augmented activation of proto-oncogene tyrosine-protein kinase Src (c-Src), which is a critical player in osteoclast survival. We found that AZI2 inhibits c-Src activity by regulating the activation of heat shock protein 90 (Hsp90), a chaperone involved in c-Src dephosphorylation. Furthermore, we demonstrated that AZI2 indirectly inhibits c-Src by interacting with the Hsp90 co-chaperone Cdc37. Strikingly, administration of a c-Src inhibitor markedly prevented bone loss in AZI2 knock-out mice. Together, these findings indicate that AZI2 regulates bone mass by fine-tuning osteoclast survival.