Chemoreception of Marine Chemical Defenses

Abstract

Many marine organisms protect themselves from predators by concentrating triterpene glycosides in their tissue. It has been proposed that predatory fish response to triterpene glycoside formoside is mediated by chemoreceptors. RL-TGR, a co-receptor involved in triterpene glycoside signaling has been identified in zebrafish. However, the mechanism and scope of function of RL-TGR is not fully understood. Formoside form marine sponge E. formosus and thornasteroside A from sea star A. Planci were purified using reversed phase HPLC, and the structure characterized via 1H NMR spectroscopy. To test for a functional response, RL-TGR was expressed in HEK 293 cells along with β2AR, which was necessary for trafficking to the cell membrane. HEK 293 cells expressing RL-TGR were treated with formoside and thornasteroside A and the activity of RL-TGR was determined by measuring the changes in the cAMP levels in these cells. This study found no significant effect of either formoside or thornasteroside A on the cAMP production in cells expressing RL-TGR. Therefore, a functional response of RL-TGR to formoside and thornasteroside A was not observed in this study. Understanding the scope of chemical defenses and chemoreception in marine environments is crucial to expanding our knowledge of the structure and function of marine communities.