Human taste cells express the G protein α-gustducin and neuron-specific enolase
Abstract Expression of the α-subunit of the taste-specific G protein α-gustducin and the glycolytic enzyme neuron-specific enolase (NSE) was investigated immunohistochemically in human circumvallate and foliate taste papillae. Immunofluorescence for α-gustducin was observed in taste cells of both types of papillae and exhibited two patterns of immunofluorescence, plasmalemmal and cytosolic. The plasmalemmal pattern showed intense immunofluorescence localized to the apical region, and was exhibited by most immunoreactive taste cells. In contrast, the cytosolic pattern, observed in one or two immunoreactive cells in a taste bud per section, showed immunofluorescence distributed throughout the cytoplasm. A subpopulation of α-gustducin-immunoreactive taste receptor cells, most of which exhibited the cytosolic pattern, also expressed NSE. Optical sectioning, using confocal laser scanning microscopy, demonstrated the highest level of expression of α-gustducin in the apical microvillar region of the taste cells in close apposition to the taste pore. These studies indicate conservation of epitopes of α-gustducin in humans and rats, and suggest that this G protein is associated with taste transduction in both rats and humans. The patterns of expression of α-gustducin, and coexpression with NSE, may correlate with specialized subtypes or developmental stages of taste receptor cells.