G protein betagamma complexes in circumvallate taste cells involved in bitter transduction

• Published in: Chemical senses 2000-08, Vol.25 (4), p.413-421
• Main Authors: Rössler, P, Boekhoff, I, Tareilus, E, Beck, S, Breer, H, Freitag, J
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; DNA Primers; GTP-Binding Proteins - metabolism; GTP-Binding Proteins - physiology; Immunohistochemistry; Inositol 1,4,5-Trisphosphate - metabolism; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - physiology; Taste Buds - cytology; Taste Buds - metabolism; Taste Buds - physiology
• ISSN: 0379-864X; 1464-3553; 1464-3553
• DOI: 10.1093/chemse/25.4.413

G protein betagamma (Gbetagamma) complexes are considered to play an important role in second messenger signaling of phospholipase C (PLC). Monitoring the inositol 1,4,5-trisphosphate (IP(3)) response in circumvallate tissue homogenates upon stimulation with denatonium benzoate, it was demonstrated that a glutathione S-transferase-GRK3ct fusion protein-a Gbetagamma scavenger-attenuates the bitter tastant-induced second messenger reaction. Towards an identification of the Gbetagamma complex involved in rat bitter taste transduction, it was found that the G protein beta(3) subtype is specifically expressed in taste receptor cells of circumvallate papillae. Gbeta(3)-specific antibodies blocked the denatonium benzoate-induced IP(3) formation in a dose-dependent manner; the inhibitory effect was reversed by preincubation with the antigenic peptide. A less pronounced inhibition was observed using Gbeta(1)-specific antibodies. Analyzing individual taste cells by single cell reverse transcriptase-polymerase chain reaction approaches, overlapping expression patterns for PLCbeta(2), Galpha(gust), Gbeta(3) and Ggamma(3) could be demonstrated. Furthermore, the co-expression of all profiled signal transduction components in individual taste receptor cells could be detected. These data support the concept that the denatonium benzoate-induced IP(3) response is mediated by an activation of PLCbeta(2) via a Gbetagamma complex, possibly composed of Gbeta(3) as the predominant beta subunit and Ggamma(3), and imply that multiple second messenger pathways may exist in individual taste receptor cells.