Taste Cells of the Type III Employ CASR to Maintain Steady Serotonin Exocytosis at Variable Ca 2+ in the Extracellular Medium

Type III taste cells are the only taste bud cells which express voltage-gated (VG) Ca channels and employ Ca -dependent exocytosis to release neurotransmitters, particularly serotonin. The taste bud is a tightly packed cell population, wherein extracellular Ca is expected to fluctuate markedly due t...

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Published inCells (Basel, Switzerland) Vol. 11; no. 8
Main Authors Cherkashin, Aleksandr P, Rogachevskaja, Olga A, Kabanova, Natalia V, Kotova, Polina D, Bystrova, Marina F, Kolesnikov, Stanislav S
Format Journal Article
LanguageEnglish
Published Switzerland 18.04.2022
Subjects
Calcium - metabolism
Exocytosis
HEK293 Cells
Humans
Receptors, Calcium-Sensing
Serotonin
Taste
voltage-gated Ca2+ channels
taste cells
extracellular Ca2+-sensing receptor
serotonin biosensor
serotonin secretion
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Summary:Type III taste cells are the only taste bud cells which express voltage-gated (VG) Ca channels and employ Ca -dependent exocytosis to release neurotransmitters, particularly serotonin. The taste bud is a tightly packed cell population, wherein extracellular Ca is expected to fluctuate markedly due to the electrical activity of taste cells. It is currently unclear whether the Ca entry-driven synapse in type III cells could be reliable enough at unsteady extracellular Ca . Here we assayed depolarization-induced Ca signals and associated serotonin release in isolated type III cells at varied extracellular Ca . It turned out that the same depolarizing stimulus elicited invariant Ca signals in type III cells irrespective of bath Ca varied within 0.5-5 mM. The serotonin release from type III cells was assayed with the biosensor approach by using HEK-293 cells co-expressing the recombinant 5-HT4 receptor and genetically encoded cAMP sensor Pink Flamindo. Consistently with the weak Ca dependence of intracellular Ca transients produced by VG Ca entry, depolarization-triggered serotonin secretion varied negligibly with bath Ca . The evidence implicated the extracellular Ca -sensing receptor in mediating the negative feedback mechanism that regulates VG Ca entry and levels off serotonin release in type III cells at deviating Ca in the extracellular medium.
ISSN:2073-4409