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Serotonin-induced stereospecific formation and bioactivity of the eicosanoid 17,18-epoxyeicosatetraenoic acid in the regulation of pharyngeal pumping of C. elegans

Item Type:Article
Title:Serotonin-induced stereospecific formation and bioactivity of the eicosanoid 17,18-epoxyeicosatetraenoic acid in the regulation of pharyngeal pumping of C. elegans
Creators Name:Zhou, Y., Rothe, M., Schunck, W.H., Ruess, L. and Menzel, R.
Abstract:17,18-Epoxyeicosatetraenoic acid (17,18-EEQ), the most abundant eicosanoid generated by cytochrome P450 (CYP) enzymes in C. elegans, is a potential signaling molecule in the regulation of pharyngeal pumping activity of this nematode. As a chiral molecule, 17,18-EEQ can exist in two stereoisomers, the 17(R),18(S)- and 17(S),18(R)-EEQ enantiomers. Here we tested the hypothesis that 17,18-EEQ may function as a second messenger of the feeding-promoting neurotransmitter serotonin and stimulates pharyngeal pumping and food uptake in a stereospecific manner. Serotonin treatment of wildtype worms induced a more than twofold increase of free 17,18-EEQ levels. As revealed by chiral lipidomics analysis, this increase was almost exclusively due to an enhanced release of the (R,S)-enantiomer of 17,18-EEQ. In contrast to the wildtype strain, serotonin failed to induce 17,18-EEQ formation as well as to accelerate pharyngeal pumping in mutant strains defective in the serotonin SER-7 receptor. However, the pharyngeal activity of the ser-7 mutant remained fully responsive to exogenous 17,18-EEQ administration. Short term incubations of well-fed and starved wildtype nematodes showed that both racemic 17,18-EEQ and 17(R),18(S)-EEQ were able to increase pharyngeal pumping frequency and the uptake of fluorescence-labeled microspheres, while 17(S),18(R)-EEQ and also 17,18-dihydroxyeicosatetraenoic acid (17,18-DHEQ, the hydrolysis product of 17,18-EEQ) were ineffective. Taken together, these results show that serotonin induces 17,18-EEQ formation in C. elegans via the SER-7 receptor and that both the formation of this epoxyeicosanoid and its subsequent stimulatory effect on pharyngeal activity proceed with high stereospecificity confined to the (R,S)-enantiomer.
Keywords:Caenorhabditis elegans Proteins, Cytochrome P-450 Enzyme System, Eicosanoids, Serotonin, Animals, Caenorhabditis elegans
Source:Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
ISSN:1388-1981
Publisher:Elsevier
Volume:1868
Number:5
Page Range:159304
Date:May 2023
Official Publication:https://doi.org/10.1016/j.bbalip.2023.159304
PubMed:View item in PubMed

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