Comprehensive study on G protein alpha-subunits in taste bud cells, with special reference to the occurrence of G alpha i2 as a major G alpha species

Previous stud ies have identified many cDNA species that encode a variety o f G protein alpha-subunits occurring in taste buds. These include the cDNA encoding a taste-bud-specific G alpha, gustducin (G(gust)) Here we carried out comprehensive analyses of G alpha species that occur in the taste buds of rat circumvallate papillae and also in their single cells isolated from the taste buds. Reverse transcriptase-polymerase chain reaction showed the presence of 10 kinds of G alpha cDNAs, including a splice variant of G alph a s, among which G(gust), G alpha s, G alpha i2 and G alpha i3 cDNAs were s hown to be major species. In situ hybridization and immunohistochemistry sh owed that G alpha i2, as well as G(gust), expressed in a subset of taste bu d cells, and the frequency of G alpha i2-expression appears to be higher th an that of G(gust) Southern ana lyses of the amplified cDNA from single tel ls showed that each taste bud cell expresses multiple G alpha mRNA species. For example, some G alpha i2-positive cells also express one or more other G alpha species, including G alpha s, G alpha i3 and G(gust), and there is no apparent correlation in expression among the three G alpha species.