FUNCTIONAL EXPRESSION OF OLFACTORY-ADRENERGIC RECEPTOR CHIMERAS AND INTRACELLULAR RETENTION OF HETEROLOGOUSLY EXPRESSED OLFACTORY RECEPTORS

Replacing the G-protein-coupling domains of the beta(2)-adrenergic rec eptor with homologous domains of putative olfactory receptors produced chimeric receptors which were able to stimulate pigment dispersion in Xenopus melanophores, a G-protein-mediated pathway. A multiple replac ement chimera containing the second, third and C-terminal cytoplasmic domains of receptor OR5 elevated cyclic adenosine 3':5'-monophosphate (cAMP) and suppressed production of inositol phosphates. Co-expression of G alpha(olf) did not alter the strength of response of this chimer a. A novel rat olfactory receptor cDNA (U131) was isolated and sequenc ed. Expression of U131 and OR5 constructs containing an N-terminal epi tope-tag or C-terminal fusion to green fluorescent protein occurred in an intracellular network but not in the plasma membrane of heterologo us cells. Similarly treated beta(2)-adrenergic receptors were function al and were observed in the plasma membrane and the intracellular netw ork. These results demonstrate that the putative cytoplasmic domains o f olfactory receptors are capable of functional interaction with heter ologous G-proteins of the G alpha(s) subtype. Instead, the absence of these receptors from the plasma membrane of heterologous cells appears to explain our inability to determine if odorants can activate the ol factory receptor clones. We hypothesize that the olfactory receptors h ave requirements for maturation and targeting to the plasma membrane t hat are different from most other G-protein-coupled receptors. (C) 199 7 Elsevier Science B.V.