Partial cloning of putative G-proteins modulating mechanotransduction in the ciliate Stentor

Signal transduction systems known to utilize G-proteins in higher eukaryote s undoubtedly evolved prior to the development of metazoa. Pharmacological evidence indicates that the ciliates Paramecium, Stentor, and Tetrahymena a ll utilize signaling systems similar to those found in mammals. However, th ere has been relatively little direct evidence for the existence of G-prote ins in ciliates. Since highly conserved heterotrimeric G-proteins form the basis of receptor-coupled signal transduction systems in a wide variety of metazoa, it is of interest to know if these important signaling molecules w ere early to evolve and are present and functionally important in a wide va riety of unicellular organisms. We have previously shown that mechanotransd uction in Stentor is modulated by opiates in a manner that may involve pert ussis toxin-sensitive G-proteins. Here we utilize drugs known to interact w ith G-proteins to further test for the involvement of these important signa ling molecules in Stentor mechanotransduction. We present behavioral and el ectrophysiological data demonstrating that putative G-proteins in Stentor d ecrease mechanical sensitivity by modulating the mechanotransduction proces s. In addition, we report the partial cloning of 4 G-protein alpha -subunit s from Stentor. We confirm that these clones are of Stentor origin and are transcribed. Furthermore, we employ antisense oligodeoxynucleotide-mediated knockout to demonstrate that these ciliate G-proteins exert a modulatory i nfluence on Stentor behavior, and that a G(i)/G(o)-like clone mediates the inhibitory action of beta -endorphin on mechanotransduction.