Calreticulin mediates anesthetic sensitivity in Drosophila melanogaster

Background: Various species, e.g., Caenorbabditis elegans, Drosophila melanogaster, and mice, have been used to explore the mechanisms of action of general anesthetics in vivo. The authors isolated a Drosophila mutant, eth(as)311, that was hypersensitive to diethylether and characterized the calreticulin (crc) gene as a candidate of altered anesthetic sensitivity. Methods: Molecular analysis of crc included cloning and sequencing of the cDNA, Northern blotting, and in situ hybridization to accomplish the function of the gene and its mutation. For anesthetic phenotype assay, the 50% anesthetizing concentrations were determined for eth(as)311, revertants, and double-mutant strains (wild-type crc transgene plus eth(as)311). Results: Expression of the crc 1.4-kb transcript was lower in the mutant eth(as)311 than in the wild type at all developmental stages. The highest expression at 19 h after pupation was observed in the brain of the wild type but was still low in the mutant at that stage. The mutant showed resistance to isoflurane as well as hypersensitivity to diethylether, whereas it showed the wild phenotype to halothane. Both mutant phenotypes were restored to the wild type in the revertants and double-mutant strains. Conclusion: eth(as)311 is a mutation of low expression of the Drosophila calreticulin gene. The authors demonstrated that hypersensitivity to diethylether and resistance to isoflurane are associated with low expression of the gene. In Drosophila, calreticulin seems to mediate these anesthetic sensitivities, and it is a possible target for diethylether and isoflurane, although the predicted anesthetic targets based on many studies in vitro and in vivo are the membrane proteins, such as ion channels and receptors.