The intrinsic ability of neurogenesis after stroke has been proven weak, which results in insufficient repair of injury in the nerve system. Recent studies suggest multiple microRNAs (miRNAs) are involved in the neuroremodeling process. Targeted miRNAs delivery for amplification of neurogenesis is promising in promoting the prognosis after ischemia. Here, we showed that modified exosomes, with rabies virus glycoprotein (RVG) fused to exosomal protein lysosome-associated membrane glycoprotein 2b (Lamp2b), could efficiently deliver miR-124 to the infarct site. Systemic administration of RVG-exosomes loaded with miR-124 promoted cortical neural progenitors to obtain neuronal identity and protect against ischemic injury by robust cortical neurogenesis. Our study suggests that RVG-exosomes can be utilized therapeutically for the targeted delivery of gene drugs to the brain, thus having great potential for clinical applications.

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Linear ubiquitination is a critical regulator of inflammatory signaling pathways. However, linearly ubiquitinated substrates and the biological significance of linear ubiquitination is incompletely understood. Here, we show that STAT1 has linear ubiquitination at Lys511 and Lys652 residues in intact cells, which inhibits STAT1 binding to the type-I interferon receptor IFNAR2, thereby restricting STAT1 activation and resulting in type-I interferon signaling homeostasis. Linear ubiquitination of STAT1 is removed rapidly by OTULIN upon type-I interferon stimulation, which facilitates activation of interferon-STAT1 signaling. Furthermore, viruses induce HOIP expression through the NF-κB pathway, which in turn increases linear ubiquitination of STAT1 and thereby inhibits interferon antiviral response. Consequently, HOIL-1L heterozygous mice have active STAT1 signaling and enhanced responses to type-I interferons. These findings demonstrate a linear ubiquitination-mediated switch between homeostasis and activation of type-I interferon signaling, and suggest potential strategies for clinical antiviral therapy.

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