Anti-MIB2 monoclonal antibody, clone 4B8

Neuroinflammation plays a critical role in ischemia-induced brain injury. Mib2, an E3 ubiquitin ligase, has been reported to regulate Notch signaling and participate in the peripheral immune system. However, the roles of Mib2 in the nervous system are not well characterized. In this study, we show that Mib2 is involved in lipopolysaccharide (LPS)- and oxygen-glucose deprivation (OGD)-induced microglial activation. Mechanistically, Mib2 interacts with the IKK complex and regulates the activation of NF-kappa B signaling, thus modulating Notch1 transcription in the microglia. Furthermore, we generated a microglia-specific Mib2 knockout mice and found that microglia-specific deletion of Mib2 significantly alleviates ischemia-induced neuroinflammation and brain injury. Taken together, our results reveal a critical role of Mib2 in microglial activation and ischemia-induced brain injury, thus providing a potential target for the treatment of stroke.

Notch signaling regulates lineage decisions at multiple stages of lymphocyte development, and Notch activation requires the endocytosis of Notch ligands in the signal-sending cells. Four E3 ubiquitin ligases, Mind bomb (Mib) 1, Mib2, Neuralized (Neur) 1, and Neur2, regulate the Notch ligands to activate Notch signaling, but their roles in lymphocyte development have not been defined. We show that Mib1 regulates T and marginal zone B (MZB) cell development in the lymphopoietic niches. Inactivation of the Mib1 gene, but not the other E3 ligases, Mib2, Neur1, and Neur2, abrogated T and MZB cell development. Reciprocal bone marrow (BM) transplantation experiments revealed that Mib1 in the thymic and splenic niches is essential for T and MZB cell development. Interestingly, when BM cells from transgenic Notch reporter mice were transplanted into Mib1-null mice, the Notch signaling was abolished in the double-negative thymocytes. In addition, the endocytosis of DII1 was impaired in the Mib1-null microenvironment. Moreover, the block in T cell development and the failure of DII1 endocytosis were also observed in coculture system by Mib1 knockdown. Our study reveals that Mib1 is the essential E3 ligase in T and MZB cell development, through the regulation of Notch ligands in the thymic and splenic microenvironments.