Afferent neurotransmission mediated by hemichannels in mammalian taste cells

EMBO J. 2007 Feb 7;26(3):657-67. doi: 10.1038/sj.emboj.7601526. Epub 2007 Jan 18.


In mammalian taste buds, ionotropic P2X receptors operate in gustatory nerve endings to mediate afferent inputs. Thus, ATP secretion represents a key aspect of taste transduction. Here, we characterized individual vallate taste cells electrophysiologically and assayed their secretion of ATP with a biosensor. Among electrophysiologically distinguishable taste cells, a population was found that released ATP in a manner that was Ca(2+) independent but voltage-dependent. Data from physiological and pharmacological experiments suggested that ATP was released from taste cells via specific channels, likely to be connexin or pannexin hemichannels. A small fraction of ATP-secreting taste cells responded to bitter compounds, indicating that they express taste receptors, their G-protein-coupled and downstream transduction elements. Single cell RT-PCR revealed that ATP-secreting taste cells expressed gustducin, TRPM5, PLCbeta2, multiple connexins and pannexin 1. Altogether, our data indicate that tastant-responsive taste cells release the neurotransmitter ATP via a non-exocytotic mechanism dependent upon the generation of an action potential.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Afferent Pathways / physiology
  • Animals
  • Calcium / metabolism
  • Cells, Cultured
  • Connexins / metabolism
  • Electrophysiology
  • Immunohistochemistry
  • Isoenzymes / metabolism
  • Membrane Proteins / metabolism*
  • Mice
  • Microscopy, Fluorescence
  • Nerve Tissue Proteins / metabolism
  • Phospholipase C beta
  • Receptors, Purinergic P2 / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / physiology*
  • TRPM Cation Channels / metabolism
  • Taste Buds / physiology*
  • Transducin / metabolism
  • Type C Phospholipases / metabolism


  • Connexins
  • Isoenzymes
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Panx1 protein, mouse
  • Receptors, Purinergic P2
  • TRPM Cation Channels
  • Trpm5 protein, mouse
  • gustducin
  • Adenosine Triphosphate
  • Type C Phospholipases
  • Phospholipase C beta
  • Transducin
  • Calcium