GUST27 AND CLOSELY-RELATED G-PROTEIN-COUPLED RECEPTORS ARE LOCALIZED IN TASTE-BUDS TOGETHER WITH GI-PROTEIN ALPHA-SUBUNIT

Gustatory, like olfactory signalling is probably mediated by seven-tra nsmembrane receptors and coupling GTP-binding proteins (G proteins). W e investigated the expression of a subset of these receptors and the G i protein alpha-subunit by using their specific antibodies. Based on o ur previous finding that the mRNA for GUST27, one of these receptors, is expressed in rat lingual epithelia, we first prepared an antibody t o the synthetic nonapeptide, H . Ser-Tyr-Ser-Gln-Ile-Ala-Ser-Ser-Leu . OH which corresponds to the third intracellular domain of GUST27 and also to those of a subset of related receptors whose occurrence can be predicted by PCR. Immunohistochemical studies with rat circumvallate papillae indicated that the anti-GUST27 antibody reacted with many of the taste buds examined, with strong signals appearing in particular t aste cells. We then carried out a similar immunohistochemical experime nt with an antibody to the Gi protein alpha-subunit and found that thi s subunit is also expressed in taste buds as demonstrated in the case of gustducin and transducin. Taken together, these results strongly su ggest that GUST27 and closely related receptors, as well as Gi alpha p roteins, are involved in intracellular taste signal transduction.