Abstract
BACKGROUND: In all animals, the nervous system senses microbial signals to influence host defense. Despite emerging as important sensors of infection to regulate immunity and inflammation, the mechanisms by which pain-sensing nociceptor neurons can detect infections are poorly defined. Using C. elegans as a tractable model host that shares many features with mammalian systems, we investigated nociceptor function during bacterial infection. RESULTS: In vivo intracellular Ca(2+) imaging of nociceptor ASH neurons revealed a drastic reduction in ASH responses to aversive stimuli in Staphylococcus aureus-infected animals compared to noninfected controls. Morphological examination showed that the ASH neurons lost integrity in the sensory processes that extend to the mouth, in a pathogen growth phase-dependent manner. Neighboring neurons did not exhibit this pathogen-induced neurodegeneration (PaIN) phenotype. Genetic analysis suggested that apoptosis, necrosis, ferroptosis, and autophagy are dispensable for the PaIN phenotype. In contrast, loss of the evolutionarily conserved stress-response transcription factor HLH-30/TFEB reduced the penetrance of ASH PaIN by about 50%. Moreover, infected animals showed defective ASH-mediated evasive behaviors, suggesting that the S. aureus-triggered drop in ASH activation and morphological degeneration are physiologically relevant. CONCLUSIONS: Collectively, these findings reveal that nociceptor neurons lose functional and morphological integrity during infection with S. aureus, with severe consequences for animal behavior. Because S. aureus is a critical human pathogen, the induction of nociceptor PaIN may have important implications for human health.