SEB-3, a CRF receptor-like GPCR, regulates locomotor activity states, stress responses and ethanol tolerance in Caenorhabditis elegans.

The CRF (corticotropin-releasing factor) system is a key mediator of the stress response. Alterations in CRF signaling have been implicated in drug craving and ethanol consumption. The development of negative reinforcement via activation of brain stress systems has been proposed as a mechanism that contributes to alcohol dependence. Here, we isolated a gain-of-function allele of seb-3, a CRF receptor-like GPCR in Caenorhabditis elegans, providing an in vivo model of a constitutively activated stress system. We also characterized a loss-of-function allele of seb-3 and showed that SEB-3 positively regulates a stress response that leads to an enhanced active state of locomotion, behavioral arousal and tremor. SEB-3 also contributed to acute tolerance to ethanol and to the development of tremor during ethanol withdrawal. Furthermore, we found that a specific CRF(1) receptor antagonist reduced acute functional tolerance to ethanol in mice. These findings demonstrate functional conservation of the CRF system in responses to stress and ethanol in vertebrates and invertebrates.

Ethanol preference in C. elegans.

Caenorhabditis elegans senses multiple environmental stimuli through sensory systems and rapidly changes its behaviors for survival. With a simple and well-characterized nervous system, C. elegans is a suitable animal model for studying behavioral plasticity. Previous studies have shown acute neurodepressive effects of ethanol on multiple behaviors of C. elegans similar to the effect of ethanol on other organisms. Caenorhabditis elegans also develops ethanol tolerance during continuous exposure to ethanol. In mammals, chronic ethanol exposure leads to ethanol tolerance as well as increased ethanol consumption. Ethanol preference is associated with the development of tolerance and may lead to the development of ethanol dependence. In this study, we show that C. elegans is a useful model organism for studying chronic effects of ethanol, including the development of ethanol preference. We designed a behavioral assay for testing ethanol preference after prolonged ethanol exposure. Despite baseline aversive responses to ethanol, animals show ethanol preference after 4 h of pre-exposure to ethanol and exhibit significantly enhanced preference for ethanol after a lifetime of ethanol exposure. The cat-2 and tph-1 mutant animals have defects in the synthetic enzymes for dopamine and serotonin, respectively. These mutants are deficient in the development of ethanol preference, indicating that dopamine and serotonin are required for this form of behavioral plasticity.

A deubiquitinating enzyme, UCH/CeUBP130, has an essential role in the formation of a functional microtubule-organizing centre (MTOC) during early cleavage in C. elegans.

BACKGROUND: Deubiquitinating enzymes generate monomeric ubiquitin in protein degradation pathways and are known to be important for the early development in many organisms. RESULTS: RNA interference experiments targeted for a UBP homologue, UCH/CeUBP130, in C. elegans resulted in cell division defective embryos. Immunostaining localized UCH/CeUBP130 in the sperm and at the microtubule-organizing centre (MTOC) during early cleavage. Furthermore, the embryonic lethal phenotype was rescued by mating with wild-type males. CONCLUSIONS: Since it is known that the MTOC in the fertilized embryo is contributed by sperm asters in C. elegans, we suggest that UCH/CeUBP130 and ubiquitin protein degradation pathways may be involved in microtubule-based sperm aster formation. Therefore UCH/CeUBP130 is necessary for the formation of a functional MTOC in the fertilized embryo of C. elegans.