Molecular cloning of a lobster G(β) subunit and G(β) expression in olfactory receptor neuron dendrites and brain neuropil

We have isolated from the olfactory organ of the American lobster (Homarus americanus) two cDNA clones with homology to β subunits of G proteins. LobG(β1) contained a complete open reading frame that predicted an amino acid sequence with >80% identity to G(β) sequences from other species. LobG(β2) was a fragment of an open reading frame whose predicted amino acid sequence had 65-69% identity to other G(β) sequences. LobG(β2) mRNA was not detectable in the brain, eye plus eyestalk, leg, dactyl, olfactory organ, or tail muscle. In contrast, lobG(β1) was expressed in all these tissues as a single mRNA species of 6.4 kb and a protein of 37 kD. In the brain and olfactory organ, G(β) immunoreactivity was almost exclusively confined to neurites: the neuropil regions of the brain and the outer dendrites of the olfactory receptor neurons. Coimmunoprecipitation revealed that lobster G(β) interacted with both G(αs) and G(αq). LobG(β1) is likely to be involved in a wide range of signaling events including olfactory transduction and synaptic transmission in the brain.