MOLECULAR-CLONING AND CHARACTERIZATION OF A LOBSTER G-ALPHA(S) PROTEIN EXPRESSED IN NEURONS OF OLFACTORY ORGAN AND BRAIN

We have isolated from an American lobster (Homarus americanus) olfacto ry organ cDNA library a clone, lobG alpha(s), with >70% identity to ma mmalian and arthropod G alpha(s) sequences. In genomic Southern blots, a fragment of lobG alpha(s) detected only one band, suggesting the lo bsters have a single G alpha(s) gene. In brain and olfactory organ, lo bG alpha(s) mRNA was expressed predominantly in neurons, including man y of the neuronal cell body clusters of the brain. G alpha(s) protein was also expressed broadly, appearing on western blots as a band of 51 .8 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory o rgan, and aesthetasc hairs. These results suggest that lobG alpha(s) p lays a role in a wide variety of signal transduction events. Its prese nce in the olfactory aesthetasc hairs, which are almost pure preparati ons of the outer dendrites of the olfactory receptor neurons, and the expression of lobG alpha(s) mRNA in the olfactory receptor neurons of the olfactory organ indicate that lobG alpha(s) may mediate olfactory transduction. That virtually all ORNs express lobG alpha(s) mRNA equal ly predicts that hyperpolarizing odor responses mediated by cyclic AMP are a property of all lobster olfactory receptor neurons.