Liotta, D. C. | bioRxiv Science

bioRxiv2025

Discrete interneuron subsets participate in GluN1/GluN3A excitatory glycine receptor (eGlyR)-mediated regulation of hippocampal network activity throughout development and evolution.

Decades of studies implicating GluN3A N-methyl-D-aspartate receptor (NMDAR) subunits in physiological and pathological function have largely been interpreted through direct regulation of conventional glutamatergic NMDARs. However, emerging evidence indicates that GluN3A frequently assembles with GluN1 forming unconventional glutamate-insensitive NMDARs that operate as native excitatory glycine receptors (eGlyRs). Here we demonstrate that hippocampal somatostatin and neurogliaform interneurons (Sst-INs and NGFCs) express functional eGlyRs from early postnatal through adult ages. In the developing hippocampus eGlyR-mediated excitation of NGFCs with ambient glycine dramatically increases GABAergic tone, with consequences for the generation of giant depolarizing potentials (GDPs). In the mature hippocampus, eGlyR- mediated excitation of Sst-INs regulates sharp wave ripples (SWRs). Finally, we reveal evolutionary conservation of hippocampal Sst-IN eGlyRs and eGlyR- mediated SWR regulation in non-human primates confirming functional eGlyR availability for therapeutic potential in higher species. Our findings underscore that eGlyR mediated regulation of cell and circuit excitability through both cell autonomous and cell non-autonomous mechanisms must be considered to understand GluN3A roles in brain development, plasticity, and disease.

neuroscience↗

bioRxiv2025

Identification and Characterization of Novel Chikungunya Virus Polymerase Inhibitors

Chikungunya virus (CHIKV) and other alphaviruses in the Togaviridae family are positive-sense RNA viruses and major human pathogens, causing millions of infections worldwide. In humans, alphaviruses such as CHIKV, Mayaro and Ross River viruses typically cause arthritogenic disease characterized by debilitating arthralgia, joint inflammation, fever, and rash. Although a vaccine was recently approved for use against CHIKV, no vaccines are licensed against other alphaviruses. No antiviral treatments are available to prevent or treat infections by any alphavirus. To address this unmet need, we used a CHIKV nanoluciferase reporter virus to develop a high-throughput screening assay for novel small-molecule inhibitors. From this campaign, we identified several unique inhibitors of CHIKV replication. Mechanistic characterization of two inhibitors revealed that both target the nsP4 RNA-dependent RNA polymerase, while susceptibility profiling pinpointed unique nsP4 mutations that specifically confer resistance. In silico docking analyses indicated potential binding poses of the inhibitors near the polymerase active site. Collectively, these results define multiple chemotypes for further development and highlight novel molecular targets within nsP4 for CHIKV inhibition. IMPORTANCEChikungunya virus is a mosquito-borne pathogen that has caused millions of human infections worldwide, producing severe fever, rash, and long-lasting joint pain that can persist for months. Related viruses such as Mayaro and Ross River viruses also cause debilitating disease, yet no antiviral drugs are available to treat any infection caused by this family of viruses. In this study, we developed a high-throughput assay that allowed us to rapidly identify compounds capable of blocking chikungunya virus replication. We discovered new hit compounds that inhibit virus growth. In addition, we determined that two of the most promising hit candidates target the viral nsP4 polymerase. By identifying these novel inhibitors and characterizing both their mechanisms of action and resistance profiles, we have established the groundwork for future efforts to develop much needed therapies against chikungunya virus and related pathogens.

molecular biology↗