Comprehensive study on G protein α-subunits in taste bud cells, with special reference to the occurrence of Gαi2 as a major Gα species

Previous studies have identified many cDNA species that encode a variety of G protein α -subunits occurring in taste buds. These include the cDNA encoding a taste-bud-specific Gα , gustducin (Ggust). Here we carried out comprehensive analyses of Gα 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 Gα cDNAs, including a splice variant of Gα s, among which Ggust ,G α s, Gα i2 and Gα i3 cDNAs were shown to be major species. In situ hybridization and immunohistochemistry showed that Gα i2, as well as Ggust, expressed in a subset of taste bud cells, and the frequency of Gα i2expression appears to be higher than that of Ggust. Southern analyses of the amplified cDNA from single cells showed that each taste bud cell expresses multiple Gα mRNA species. For example, some Gα i2-positive cells also express one or more other Gα species, including Gα s, Gα i3 and Ggust, and there is no apparent correlation in expression among the three Gα species.

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