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Entry
map04742                    Pathway                                

Name
Taste transduction
Description
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.
Class
Organismal Systems; Sensory system
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Taste transduction
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Reference
  Authors
Liman ER, Zhang YV, Montell C
  Title
Peripheral coding of taste.
  Journal
Neuron 81:984-1000 (2014)
Reference
  Authors
Kinnamon SC, Finger TE
  Title
A taste for ATP: neurotransmission in taste buds.
  Journal
Front Cell Neurosci 7:264 (2013)
Reference
  Authors
Roper SD
  Title
Taste buds as peripheral chemosensory processors.
  Journal
Semin Cell Dev Biol 24:71-9 (2013)
Reference
  Authors
Kinnamon SC
  Title
Taste receptor signalling - from tongues to lungs.
  Journal
Acta Physiol (Oxf) 204:158-68 (2012)
Reference
  Authors
Kinnamon SC
  Title
Neurosensory transmission without a synapse: new perspectives on taste signaling.
  Journal
BMC Biol 11:42 (2013)
Reference
  Authors
Chaudhari N, Roper SD
  Title
The cell biology of taste.
  Journal
J Cell Biol 190:285-96 (2010)
Reference
  Authors
Vandenbeuch A, Kinnamon SC
  Title
Why do taste cells generate action potentials?
  Journal
J Biol 8:42 (2009)
Reference
  Authors
Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS
  Title
The receptors and cells for mammalian taste.
  Journal
Nature 444:288-94 (2006)
Reference
  Authors
Vandenbeuch A, Anderson CB, Parnes J, Enjyoji K, Robson SC, Finger TE, Kinnamon SC
  Title
Role of the ectonucleotidase NTPDase2 in taste bud function.
  Journal
Proc Natl Acad Sci U S A 110:14789-94 (2013)
Reference
  Authors
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
  Title
CALHM1 ion channel mediates purinergic neurotransmission of sweet, bitter and umami tastes.
  Journal
Nature 495:223-6 (2013)
Reference
  Authors
Gao N, Lu M, Echeverri F, Laita B, Kalabat D, Williams ME, Hevezi P, Zlotnik A, Moyer BD
  Title
Voltage-gated sodium channels in taste bud cells.
  Journal
BMC Neurosci 10:20 (2009)
Reference
  Authors
Zheng W, Hussein S, Yang J, Huang J, Zhang F, Hernandez-Anzaldo S, Fernandez-Patron C, Cao Y, Zeng H, Tang J, Chen XZ
  Title
A novel PKD2L1 C-terminal domain critical for trimerization and channel function.
  Journal
Sci Rep 5:9460 (2015)
Reference
  Authors
Shimada S, Ueda T, Ishida Y, Yamamoto T, Ugawa S
  Title
Acid-sensing ion channels in taste buds.
  Journal
Arch Histol Cytol 69:227-31 (2006)
Reference
  Authors
Dando R, Roper SD
  Title
Acetylcholine is released from taste cells, enhancing taste signalling.
  Journal
J Physiol 590:3009-17 (2012)
Reference
  Authors
Kaya N, Shen T, Lu SG, Zhao FL, Herness S
  Title
A paracrine signaling role for serotonin in rat taste buds: expression and localization of serotonin receptor subtypes.
  Journal
Am J Physiol Regul Integr Comp Physiol 286:R649-58 (2004)
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