RIPK3-dependent suppression of excitotoxicity during neuronal flavivirus infection

Abstract While neurons were previously believed to be immunologically inert, recent advances have redefined our understanding of the intrinsic immunological activity of this cell type. Notably, neurons exhibit robust innate immune responses to viral infection, often employing adaptations of antiviral processes that reflect their unique cell biology. We and others recently described one such adaptation, in which activation of receptor interacting protein kinase-3 (RIPK3) in neurons during flavivirus infection does not result in necroptotic cell death, the canonical function of this protein. Instead, neuronal RIPK3 activation drives a cell death-independent transcriptional program that includes a broad variety of antiviral and immunoregulatory genes. However, while roles for RIPK3 in coordinating neuronal inflammatory responses are now established, the potential impact of RIPK3 activation on other features of neuronal cell biology, including neurotransmission, remain unexplored. In preliminary experiments, we have shown that RIPK3 activation following neuronal Zika virus infection supports expression of a broad class of genes involved in synapse regulation, including neurotransmitter receptor trafficking and internalization. We also show that increased neuronal cell death and animal mortality in neuron cultures and mice lacking RIPK3 can be rescued by pharmacologic blockade of the ionotropic glutamate receptor NMDAR. We thus hypothesize that RIPK3 protects neuronal viability during Zika virus infection via suppression of NMDAR-dependent excitotoxic cell death. We will test this idea using an innovative combination of pharmacogenetics, imaging, molecular biology, and electrophysiological approaches. If successful, these studies will define a new, pro-survival function for a canonical cell death protein in neurons, as well as bring new clarity to the impact of innate immune signaling on neurotransmission.