A Heterogeneous Mixture of F-Series Prostaglandins Promotes Sperm Guidance in the Caenorhabditis elegans Reproductive Tract

Abstract

The mechanisms that guide motile sperm through the female reproductive tract to oocytes are not well understood. We have shown that Caenorhabditis elegans oocytes synthesize sperm guiding F-series prostaglandins from polyunsaturated fatty acid (PUFA) precursors provided in yolk lipoprotein complexes. Here we use genetics and electrospray ionization tandem mass spectrometry to partially delineate F-series prostaglandin metabolism pathways. We show that omega-6 and omega-3 PUFAs, including arachidonic and eicosapentaenoic acids, are converted into more than 10 structurally related F-series prostaglandins, which function collectively and largely redundantly to promote sperm guidance. Disruption of omega-3 PUFA synthesis triggers compensatory up-regulation of prostaglandins derived from omega-6 PUFAs. C. elegans F-series prostaglandin synthesis involves biochemical mechanisms distinct from those in mammalian cyclooxygenase-dependent pathways, yet PGF2α stereoisomers are still synthesized. A comparison of F-series prostaglandins in C. elegans and mouse tissues reveals shared features. Finally, we show that a conserved cytochrome P450 enzyme, whose human homolog is implicated in Bietti's Crystalline Dystrophy, negatively regulates prostaglandin synthesis. These results support the model that multiple cyclooxygenase-independent prostaglandins function together to promote sperm motility important for fertilization. This cyclooxygenase-independent pathway for F-series synthesis may be conserved.

Gamete interactions require transmembranous immunoglobulin-like proteins with conserved roles during evolution

“…Therefore, when genes involved in the synthesis are mutated, spermatozoa become partly defective in their relocation from the uterus into the spermatheca. [18][19][20] These phenotypes seem similar to those of spe-9 and spe-45 mutants, resulting in the incomplete sperm recruitment into the spermatheca. Currently the sperm prostaglandin-receptor(s) is not known, but SPE-9 and/or SPE-45 could function in the prostaglandin binding to spermatozoa and/or subsequent sperm reaction(s).…”

Prostaglandin Extraction and Analysis in <em>Caenorhabditis elegans</em>

“…PGs is available in Figure 4 and Table 2 3,16 . MS/MS data for mammalian eicosanoids is available at www.lipidmaps.org.…”

“…We have demonstrated that C. elegans synthesizes F-series PGs that guide motile sperm to oocytes 3,6,16 . F-series PGs derived from 20-carbon PUFAs with three, four, and five double bonds, comprising the F1, F2, and F3 classes, respectively have been identified 3,16 .…”

“…F-series PGs derived from 20-carbon PUFAs with three, four, and five double bonds, comprising the F1, F2, and F3 classes, respectively have been identified 3,16 . These PGs are synthesized independent of cyclooxygenase enzymes, yet PGF 1α and PGF 2α stereoisomers are still generated.…”

“…In mammals, prostaglandins can be formed through cyclooxygenase enzyme-dependent and -independent pathways 10,15 . C. elegans synthesizes a wide array of prostaglandins independent of cyclooxygenases 6,16,17 . A large class of F-series prostaglandins has been identified, but the study of eicosanoids is at an early stage with ample room for new discoveries.…”