Coupling of bitter receptor to phosphodiesterase through transducin in taste receptor cells.
The rod and cone transducins are specific G proteins originally thought to be present only in photoreceptor cells of the vertebrate retina. Transducins convert light stimulation of photoreceptor opsins into activation of cyclic GMP phosphodiesterase (reviewed in refs. 5-7). A transducin-like G protein, gustducin, has been identified and cloned from rat taste cells. We report here that rod transducin is also present in vertebrate taste cells, where it specifically activates a phosphodiesterase isolated from taste tissue. Furthermore, the bitter compound denatonium in the presence of taste-cell membranes activates transducin but not Gi. A peptide that competitively inhibits rhodopsin activation of transducin also blocks taste-cell membrane activation of transducin, arguing for the involvement of a seven-transmembrane-helix G-protein-coupled receptor. These results suggest that rod transducin transduces bitter taste by coupling taste receptor(s) to taste-cell phosphodiesterase. Phosphodieterase-mediated degradation of cyclic nucleotides may lead to taste-cell depolarization through the recently identified cyclic-nucleotide-suppressible conductance.
Ruiz-Avila
L
L
Roche Institute of Molecular Biology, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey, USA.
McLaughlin
S K
SK
Wildman
D
D
McKinnon
P J
PJ
Robichon
A
A
Spickofsky
N
N
Margolskee
R F
RF
D000818:Animals; D002417:Cattle; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012243:Rhodopsin / Q000378:metabolism; D013650:Taste Buds / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015293:Transducin / Q000378:metabolism*
D019204:GTP-Binding Proteins; D010727:Phosphoric Diester Hydrolases; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D012243:Rhodopsin; D015293:Transducin; C043414:denatonium