G Protein βγ Complexes in Circumvallate Taste Cells Involved in Bitter Transduction

• Published in: Chemical senses 2000-08, Vol.25 (4), p.413-421
• Main Authors: Rössler, Patricia, Boekhoff, Ingrid, Tareilus, Erwin, Beck, Stefan, Breer, Heinz, Freitag, Joachim
• Format: Article
• Language: English
• Subjects: Biochemistry and metabolism; Biological and medical sciences; Central nervous system; Fundamental and applied biological sciences. Psychology; Vertebrates: nervous system and sense organs
• ISSN: 0379-864X; 1464-3553
• DOI: 10.1093/chemse/25.4.413

G protein βγ (Gβγ) complexes are considered to play an important role in second messenger signaling of phospholipase C (PLC). Monitoring the inositol 1,4,5-trisphosphate (IP3) response in circumvallate tissue homogenates upon stimulation with denatonium benzoate, it was demonstrated that a glutathione S-transferase–GRK3ct fusion protein—a Gβγ scavenger—attenuates the bitter tastant-induced second messenger reaction. Towards an identification of the Gβγ complex involved in rat bitter taste transduction, it was found that the G protein β3 subtype is specifically expressed in taste receptor cells of circumvallate papillae. Gβ3-specific antibodies blocked the denatonium benzoate-induced IP3 formation in a dose-dependent manner; the inhibitory effect was reversed by preincubation with the antigenic peptide. A less pronounced inhibition was observed using Gβ1-specific antibodies. Analyzing individual taste cells by single cell reverse transcriptase–polymerase chain reaction approaches, overlapping expression patterns for PLCβ2, Gαgust, Gβ3 and Gγ3 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 IP3 response is mediated by an activation of PLCβ2 via a Gβγ complex, possibly composed of Gβ3 as the predominant β subunit and Gγ3, and imply that multiple second messenger pathways may exist in individual taste receptor cells.