Neuronal regulation of the stress response in C.elegans: Role of the neurotransmitter tyramine

Abstract

Faced with physiological or environmental challenges, isolated cells and unicellular organisms can trigger the stress response autonomously. However, this response should be coordinated in multicellular organisms, as uncoordinated responses in individual cells may be harmful for survival. Recent studies in C.elegans showed that the systemic regulation of starvation and heat shock cellular responses depend on neurons which sense amino acids and ambient temperature, respectively. In both cases, the identity of the neurohormonal signalling that modulates these cellular responses are unknown. By analyzing the C.elegans neuronal wiring diagram we found that the circuits implied in both stress responses converge in one tyraminergic neuron called RIM. We evaluated the heat shock and starvation resistance of C.elegans strains deficient on tyramine synthesis as well as in null mutants of the currently known tyramine receptors. We determined a higher stress resistance in these mutants compared with wild-type animals. We also quantified the lipid profile of these strains in the absence and presence of exogenous tyramine. Our results suggest that under prosperous conditions a basal level of tyramine is released but this signal must be repressed in order to mount a coordinated stress response when the environmental conditions become adverse. This study contributes to a better understanding of the neurohormonal signalling that controls the stress response in multicellular organisms.