RIPK3 promotes brain region-specific interferon signaling and restriction of tick-borne flavivirus infection

Abstract

Innate immune signaling in the central nervous system (CNS) exhibits many remarkable specializations that vary across cell types and CNS regions. In the setting of neuroinvasive flavivirus infection, neurons employ the immunologic kinase receptor-interacting kinase 3 (RIPK3) to promote an antiviral transcriptional program, independently of the traditional function of this enzyme in promoting necroptotic cell death. However, while recent work has established roles for neuronal RIPK3 signaling in controlling mosquito-borne flavivirus infections, including West Nile virus and Zika virus, functions for RIPK3 signaling in the CNS during tick-borne flavivirus infection have not yet been explored. Here, we use a model of Langat virus (LGTV) encephalitis to show that RIPK3 signaling is specifically required in neurons of the cerebellum to control LGTV replication and restrict disease pathogenesis. This effect did not require the necroptotic executioner molecule mixed lineage kinase domain like protein (MLKL), a finding similar to previous observations in models of mosquito-borne flavivirus infection. However, control of LGTV infection required a unique, region-specific dependence on RIPK3 to promote expression of key antiviral interferon-stimulated genes (ISG) in the cerebellum. This RIPK3-mediated potentiation of ISG expression was associated with robust cell-intrinsic restriction of LGTV replication in cerebellar granule cell neurons. These findings further illuminate the complex roles of RIPK3 signaling in the coordination of neuroimmune responses to viral infection, as well as provide new insight into the mechanisms of region-specific innate immune signaling in the CNS.

RIPK3 promotes neuronal survival by suppressing excitatory neurotransmission during CNS viral infection

“…Notably, Ripk3 -/neurons exhibited hundreds of differentially expressed genes (DEGs) compared to Ripk3 +/+ controls following infection with both viruses (Figure 1D-E). Gene ontology (GO) enrichment analysis of significant DEGs revealed overrepresentation of terms related to immune activation, especially immune cell chemotaxis, when comparing Ripk3 -/neurons to Ripk3 +/+ controls in both infection groups (Figure 1F-G), consistent with our previous work demonstrating a central for RIPK3 in promoting expression of chemokines and other innate immune genes in neurons during flavivirus infection [13][14][15] . To our surprise, however, these comparisons also revealed enrichment of GO terms associated with neurologic functions, including terms related to neurotransmission such as synaptic signaling, long-term potentiation, and neurotransmitter release (Figure 1H-I).…”

“…Extensive previous work has shown that neurons are resistant to programmed cell death 65 , including RIPK3-mediated necroptosis 10 . We and others have shown that the cell-death independent functions of RIPK3 are critical for host control of CNS viral infection through the well-established functions of this kinase in promoting immunological gene expression [13][14][15] . Here, our findings underscore an even more extensive role for RIPK3 in controlling neuronal biology during infection, including unexpected functions in regulating excitatory neurotransmission.…”

“…Primary cerebral cortical neurons were derived from E15 mouse embryos as previously described 15 . Neural tissue was harvested and processed using a Neural Tissue Dissociation Kit-T (Miltenyi, #130-093-231) using both male and female embryos.…”

UMP‐CMP kinase 2 inhibits ZIKV replication through activation of type I IFN signaling pathway

“…Many studies have reported that ISGs play critical roles to restrict ZIKV replication 27–33 . For example, Viperin has been reported to inhibit ZIKV RNA translation by activating ribosome collision‐dependent pathway 27 .…”

“…25 Many studies have reported that ISGs play critical roles to restrict ZIKV replication. [27][28][29][30][31][32][33] For example, Viperin has been reported…”