title: Afferent neurotransmission mediated by hemichannels in mammalian taste cells.
abstract: 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.
authors.affiliation: Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia.
authors.forename: Roman A
authors.initials: RA
authors.lastname: Romanov
authors.forename: Olga A
authors.initials: OA
authors.lastname: Rogachevskaja
authors.forename: Marina F
authors.initials: MF
authors.lastname: Bystrova
authors.forename: Peihua
authors.initials: P
authors.lastname: Jiang
authors.forename: Robert F
authors.initials: RF
authors.lastname: Margolskee
authors.forename: Stanislav S
authors.initials: SS
authors.lastname: Kolesnikov
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D017630:Connexins / Q000378:metabolism; D004594:Electrophysiology; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000378:metabolism; D054799:Phospholipase C beta; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D050053:TRPM Cation Channels / Q000378:metabolism; D013650:Taste Buds / Q000502:physiology*; D015293:Transducin / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D017630:Connexins; D007527:Isoenzymes; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; D018048:Receptors, Purinergic P2; D050053:TRPM Cation Channels; C498617:Trpm5 protein, mouse; C075192:gustducin; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D015293:Transducin; D002118:Calcium