SARS-CoV-2 protein ORF3a is pathogenic in Drosophila and causes phenotypes associated with COVID-19 post-viral syndrome

ABSTRACT

Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/423533v2_ufig1.gif" ALT="Figure 1"> View larger version (31K) org.highwire.dtl.DTLVardef@1be5b38org.highwire.dtl.DTLVardef@56e061org.highwire.dtl.DTLVardef@1a52040org.highwire.dtl.DTLVardef@1e86751_HPS_FORMAT_FIGEXP M_FIG C_FIG SummaryInfections and neurodegenerative diseases induce neuroinflammation, but affected individuals often show a number of non-neural symptoms including muscle pain and muscle fatigue. The molecular pathways by which neuroinflammation causes pathologies outside the central nervous system (CNS) are poorly understood, so we developed three models to investigate the impact of neuroinflammation on muscle performance. We found that bacterial infection, COVID-like viral infection, and expression of a neurotoxic protein associated with Alzheimer' s disease promoted the accumulation of reactive oxygen species (ROS) in the brain. Excessive ROS induces the expression of the cytokine Unpaired 3 (Upd3) in insects, or its orthologue IL-6 in mammals, and CNS-derived Upd3/IL-6 activates the JAK/Stat pathway in skeletal muscle. In response to JAK/Stat signaling, mitochondrial function is impaired and muscle performance is reduced. Our work uncovers a brain-muscle signaling axis in which infections and chronic diseases induce cytokine-dependent changes in muscle performance, suggesting IL-6 could be a therapeutic target to treat muscle weakness caused by neuroinflammation.