ABSTRACT Nociceptive pain is a protective response to harmful stimuli that is necessary to survival while nociplastic pain represents altered nociception arising from a sensitization of peripheral nociceptor neurons leading to subthreshold inputs eliciting a pain response. While studying a potential role for SARS-CoV-2 spike protein in pain, we identified Neuropilin 1 (NRP1) as a key receptor mediating the transduction of vascular endothelial growth factor-A (VEGFA) signaling to sensitize sensory neurons in models of nociplastic pain. In models of nerve injury pain, vascular endothelial growth factor-A (VEGFA) – an angiogenic factor – binds NRP1 and induces mechanical allodynia and thermal hyperalgesia. Pharmacological antagonism of NRP1 blocked VEGFA induced pain-like behaviors. This work demonstrated that NRP1 could be a novel therapeutic target with the potential to reverse chronic pain. Mechanistically, NRP1 sits upstream of a cytosolic protein – the collapsin response mediator protein 2 (CRMP2), a dual trafficking regulator of N-type voltage-gated calcium (CaV2.2) as well as voltage-gated sodium channels. We hypothesize that activation of the VEGFA/NRP1/CRMP2/ion channel pathway elicits sensitization of dorsal root ganglion neurons, consequently contributing to neuropathic pain states by enhancing excitatory synaptic input to dorsal spinal cord neurons. In this proposal, we test the hypothesis that interfering with VEGFA binding to NRP1 initiates an intracellular signaling cascade that, through CRMP2, leads to a decrease in sodium and calcium channel functional activity to decrease nociceptor activity culminating in reduced pain-like behaviors. We plan to test our hypothesis by using two chronic pain models to answer the following questions: 1. Does NRP1 signaling induce nociceptor sensitization and chronic hypersensitivity via CRMP2? 2. How does NRP1 signaling affect acute and chronic pain? 3. Are the anti-nociceptive effects of intrathecal NRP1inhibition mediated by targeting DRG neurons, microglia, or both? Completion of the proposed studies will allow: (i) validation of a novel target of chronic pain, (ii) use two chronic pain models to explore the breadth of applicability, and (iii) provide important information for development of a next generation of mechanism-based chronic pain medications. Overall, completion of these experiments will validate the role of NRP1 in nociceptive processing and will open opportunities for future therapeutic targeting of NRP1 for chronic pain treatment.

Project Narrative We identified a paradoxical anti-allodynic/anti-hyperalgesic function of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike protein via its binding to a surface receptor neuropilin 1 (NRP1) on sensory neurons. Specifically, we found that blocking NRP1 abolishes vascular endothelial growth factor A (VEGFA)- mediated increases in sensory neurons of CaV2.2 voltage-gated calcium and NaV1.7 voltage-gated sodium channels – two ion channels with genetically and clinically demonstrated links to chronic pain. Capitalizing on this progress, here we propose to use molecular, biochemical, neurophysiological, and functional (behavioral) assays to characterize the role of NRP1 in nociceptive processing that will open opportunities for future therapeutic targeting of NRP1 for persistent chronic pain treatment.