KEGG   PATHWAY: ko04742
ko04742                     Pathway                                
Taste transduction
Five basic tastes are recognized by humans and most other animals - bitter, sweet, sour, salty and umami. In vertebrates, taste stimuli are detected by taste receptor cells (TRCs). At least three distinct cell types are found in mammalian taste buds : type I cells, type II cells, and type III cells. Type I cells express epithelial sodium channel (ENaC) and are considered to be the major mediator of perception of low salt. In type II cells, transduction of bitter, sweet and umami is mediated by a canonical PLC-beta/IP3-signaling cascade, which culminates in the opening of the TRPM5 ion channel. This produces a depolarization that may allow CALMH1 channels to open and release ATP, which serves as a neurotransmitter to activate closely associated nerve afferents expressing P2X2, P2X3 receptors and adjacent type III cells expressing P2Y4 receptors. Type II taste cells also secrete acetylcholine (ACh) that appears to stimulate muscarinic receptors, specifically M3, on the same or neighboring Type II cells. This muscarinic feedback augments taste-evoked release of ATP. In type III cells, sour taste is initiated when protons enter through apically located proton-selective ion channels: polycystic kidney disease 2-like 1 protein (PKD2L1) and polycystic kidney disease 1-like 3 protein (PKD1L3) channels. Weak acids may also activate sour cells by penetrating the cell membrane and leading to closure of resting K+ channels and membrane depolarization. Further, voltage-gated Ca2+ channels are activated and release vesicular serotonin (5-HT), norepinephrine (NE) and gamma-aminobutyric acid (GABA). 5-HT and GABA provide negative paracrine feedback onto receptor cells by activating 5-HT1A and GABAA, GABAB receptors, respectively. 5-HT also functions as a transmitter between presynaptic cells and the sensory afferent.
Organismal Systems; Sensory system
Pathway map
ko04742  Taste transduction

Other DBs
GO: 0050909
K04824  amiloride-sensitive sodium channel subunit alpha
K04825  amiloride-sensitive sodium channel subunit beta
K04827  amiloride-sensitive sodium channel subunit gamma
K01509  adenosinetriphosphatase [EC:3.6.1.-]
K04625  taste receptor type 1 member 2
K04626  taste receptor type 1 member 3
K19729  guanine nucleotide-binding protein G(t) subunit alpha 3
K07825  guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-3
K04547  guanine nucleotide-binding protein G(I)/G(S)/G(O) subunit gamma-13
K08044  adenylate cyclase 4 [EC:]
K08046  adenylate cyclase 6 [EC:]
K08048  adenylate cyclase 8 [EC:]
K04345  protein kinase A [EC:]
K05858  phosphatidylinositol phospholipase C, beta [EC:]
K04960  inositol 1,4,5-triphosphate receptor type 3
K04980  transient receptor potential cation channel subfamily M member 5
K04834  voltage-gated sodium channel type II alpha
K04836  voltage-gated sodium channel type III alpha
K04841  voltage-gated sodium channel type IX alpha
K19738  calcium homeostasis modulator protein 1
K05216  P2X purinoceptor 2
K05217  P2X purinoceptor 3
K04270  P2Y purinoceptor 1
K04271  P2Y purinoceptor 4
K04131  muscarinic acetylcholine receptor M3
K04624  taste receptor type 1 member 1
K04603  metabotropic glutamate receptor 1
K04607  metabotropic glutamate receptor 4
K08474  taste receptor type 2
K13755  calcium/calmodulin-dependent 3',5'-cyclic nucleotide phosphodiesterase [EC:]
K04990  polycystin 2L1
K04989  polycystin 1L3
K04916  potassium channel subfamily K member 5
K04957  hyperpolarization activated cyclic nucleotide-gated potassium channel 4
K04344  voltage-dependent calcium channel P/Q type alpha-1A
K04850  voltage-dependent calcium channel L type alpha-1C
K05175  gamma-aminobutyric acid receptor subunit alpha
K04615  gamma-aminobutyric acid type B receptor
K04153  5-hydroxytryptamine receptor 1
K04819  5-hydroxytryptamine receptor 3
K04828  acid-sensing ion channel 2
C00002  ATP
C00008  ADP
C00020  AMP
C00025  L-Glutamate
C00031  D-Glucose
C00076  Calcium cation
C00080  H+
C00089  Sucrose
C00095  D-Fructose
C00130  IMP
C00133  D-Alanine
C00144  GMP
C00149  (S)-Malate
C00158  Citrate
C00208  Maltose
C00238  Potassium cation
C00334  4-Aminobutanoate
C00547  L-Noradrenaline
C00575  3',5'-Cyclic AMP
C00740  D-Serine
C00780  Serotonin
C01245  D-myo-Inositol 1,4,5-trisphosphate
C01327  Hydrochloric acid
C01330  Sodium cation
C01451  Salicin
C01996  Acetylcholine
C02265  D-Phenylalanine
C06526  Quinine
C11045  Aspartame
C12283  Saccharin
C12284  Saccharin sodium anhydrous
C19378  Cyclamate
D08836  Acesulfame potassium (NF)
Liman ER, Zhang YV, Montell C
Peripheral coding of taste.
Neuron 81:984-1000 (2014)
Kinnamon SC, Finger TE
A taste for ATP: neurotransmission in taste buds.
Front Cell Neurosci 7:264 (2013)
Roper SD
Taste buds as peripheral chemosensory processors.
Semin Cell Dev Biol 24:71-9 (2013)
Kinnamon SC
Taste receptor signalling - from tongues to lungs.
Acta Physiol (Oxf) 204:158-68 (2012)
Kinnamon SC
Neurosensory transmission without a synapse: new perspectives on taste signaling.
BMC Biol 11:42 (2013)
Chaudhari N, Roper SD
The cell biology of taste.
J Cell Biol 190:285-96 (2010)
Vandenbeuch A, Kinnamon SC
Why do taste cells generate action potentials?
J Biol 8:42 (2009)
Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS
The receptors and cells for mammalian taste.
Nature 444:288-94 (2006)
Vandenbeuch A, Anderson CB, Parnes J, Enjyoji K, Robson SC, Finger TE, Kinnamon SC
Role of the ectonucleotidase NTPDase2 in taste bud function.
Proc Natl Acad Sci U S A 110:14789-94 (2013)
Taruno A, Vingtdeux V, Ohmoto M, Ma Z, Dvoryanchikov G, Li A, Adrien L, Zhao H, Leung S, Abernethy M, Koppel J, Davies P, Civan MM, Chaudhari N, Matsumoto I, Hellekant G, Tordoff MG, Marambaud P, Foskett JK
CALHM1 ion channel mediates purinergic neurotransmission of sweet, bitter and umami tastes.
Nature 495:223-6 (2013)
Gao N, Lu M, Echeverri F, Laita B, Kalabat D, Williams ME, Hevezi P, Zlotnik A, Moyer BD
Voltage-gated sodium channels in taste bud cells.
BMC Neurosci 10:20 (2009)
Zheng W, Hussein S, Yang J, Huang J, Zhang F, Hernandez-Anzaldo S, Fernandez-Patron C, Cao Y, Zeng H, Tang J, Chen XZ
A novel PKD2L1 C-terminal domain critical for trimerization and channel function.
Sci Rep 5:9460 (2015)
Shimada S, Ueda T, Ishida Y, Yamamoto T, Ugawa S
Acid-sensing ion channels in taste buds.
Arch Histol Cytol 69:227-31 (2006)
Dando R, Roper SD
Acetylcholine is released from taste cells, enhancing taste signalling.
J Physiol 590:3009-17 (2012)
Kaya N, Shen T, Lu SG, Zhao FL, Herness S
A paracrine signaling role for serotonin in rat taste buds: expression and localization of serotonin receptor subtypes.
Am J Physiol Regul Integr Comp Physiol 286:R649-58 (2004)
ko04020  Calcium signaling pathway

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