Taste transduction

All taste pathways are proposed to converge on common elements that mediate a rise in intracellular Ca2+ followed by neurotransmitter release. Na+ salt depolarizes taste cells by passive influx of Na+ through the amiloride-sensitive Na+ channel (ENaC). Acids depolarize taste cells by a variety of mechanisms, including influx of protons (H+) through ENaC and a proton-gated cation channel (MDEG). Two putative umami receptors have been identified: a truncated variant of the metabotropic glutamate receptor mGluR4 and the heterodimer, T1R1 + T1R3. Umami receptors are coupled to a signaling pathway involving activation of PLCbeta2, production of IP3 and diacylglycerol, release of Ca2+ from intracellular stores and activation of a transient receptor potential channel, TRPM5. Bitter compounds, such as denatonium and PROP, activate particular T2R/TRB isoforms, which activate gustducin heterotrimers. Activated alpha-gustducin stimulates PDE to hydrolyze cAMP, whereas betagamma subunits activate PLCbeta2 to generate IP3, which leads to release of Ca2+ from internal stores. Artificial sweeteners activate GPCRs (T1R heterodimers) apparently linked via PLC to IP3 production and release of Ca2+ from intracellular stores. Sugars apparently activate GPCRs linked via AC to cAMP production which, in turn, may inhibit basolateral K+ channels through phosphorylation by cAMP-activated protein kinase A (PKA).

Organismal Systems; Sensory system

PMID:12581520

Zhang Y, Hoon MA, Chandrashekar J, Mueller KL, Cook B, Wu D, Zuker CS, Ryba NJ.

Coding of sweet, bitter, and umami tastes: different receptor cells sharing similar signaling pathways.

Cell 112:293-301 (2003)

PMID:12887980

Bigiani A, Ghiaroni V, Fieni F.

Channels as taste receptors in vertebrates.

Prog Biophys Mol Biol 83:193-225 (2003)

PMID:15738174

Kinnamon SC, Lin W, Ogura T, Ruiz C, Delay E.

Downstream signaling effectors for umami taste.

Chem Senses 30 Suppl 1:i31-i32 (2005)

PMID:16032395

Meyerhof W.

Elucidation of mammalian bitter taste.

Rev Physiol Biochem Pharmacol 154:37-72 (2005)

PMID:11696554

Margolskee RF.

Molecular mechanisms of bitter and sweet taste transduction.

J Biol Chem 277:1-4 (2002)

PMID:10981623

Gilbertson TA, Damak S, Margolskee RF.

The molecular physiology of taste transduction.

Curr Opin Neurobiol 10:519-27 (2000)

PMID:11738657

DeSimone JA, Lyall V, Heck GL, Feldman GM.

Acid detection by taste receptor cells.

Respir Physiol 129:231-45 (2001)

PMID:12091539

Lin W, Ogura T, Kinnamon SC.

Acid-activated cation currents in rat vallate taste receptor cells.

J Neurophysiol 88:133-41 (2002)

PMID:12736236

Feldman GM, Mogyorosi A, Heck GL, DeSimone JA, Santos CR, Clary RA, Lyall V.

Salt-evoked lingual surface potential in humans.

J Neurophysiol 90:2060-4 (2003)

PMID:8794107

Kinnamon SC, Margolskee RF.

Mechanisms of taste transduction.

Curr Opin Neurobiol 6:506-13 (1996)

PMID:12368808

Perez CA, Huang L, Rong M, Kozak JA, Preuss AK, Zhang H, Max M, Margolskee RF.

A transient receptor potential channel expressed in taste receptor cells.

Nat Neurosci 5:1169-76 (2002)

PMID:14637165

Kim MR, Kusakabe Y, Miura H, Shindo Y, Ninomiya Y, Hino A.

Regional expression patterns of taste receptors and gustducin in the mouse tongue.

Biochem Biophys Res Commun 312:500-6 (2003)

PMID:9146906

Uchida Y, Sato T.

Changes in outward K+ currents in response to two types of sweeteners in sweet taste transduction of gerbil taste cells.

Chem Senses 22:163-9 (1997)

PMID:16183910

Wettschureck N, Offermanns S.

Mammalian G proteins and their cell type specific functions.

Physiol Rev 85:1159-204 (2005)

PMID:16269362

Scott K.

Taste recognition: food for thought.

Neuron 48:455-64 (2005)

PMID:16436689

Damak S, Rong M, Yasumatsu K, Kokrashvili Z, Perez CA, Shigemura N, Yoshida R, Mosinger B Jr, Glendinning JI, Ninomiya Y, Margolskee RF.

Trpm5 null mice respond to bitter, sweet, and umami compounds.

Chem Senses 31:253-64 (2006)