EVIDENCE FOR HETEROTRIMERIC G-PROTEINS IN SEA-ANEMONES

Cnidarians, one of the earliest lineages of metazoans, have clearly id entifiable organs and a simple nervous system. The simplicity of this system affords fords an opportunity to study electrical and chemical t ransmission in its earliest stage of development. In this study the se a anemone Actinia spp. was examined for the presence of heterotrimeric G proteins. The bacterial toxin Bordetella pertussis was able to aden osine diphosphate (ADP) ribosylate a membrane-associated protein with a molecular mass of approximately 39 kDa, suggesting the presence of G (alpha)-subunits. In support of this finding, mastoparan, a direct act ivator of G proteins, induced a rapid tentacle contraction in a dose-d ependent manner. Furthermore, antisera against conserved regions of al pha and beta-subunits of mammalian G proteins detected several candida te heterotrimeric G protein subunits. These three lines of evidence su pport the hypothesis that proteins involved in G-protein-coupled signa l transduction pathways are expressed and functional in sea anemones.