Russian Journal of Biological Physics and Chemisrty Russian Journal of Biological Physics and Chemisrty АКТУАЛЬНЫЕ ВОПРОСЫ БИОЛОГИЧЕСКОЙ ФИЗИКИ И ХИМИИ 2499-9962 54137 Общая биофизика General biophysics Общая биофизика The invariance of potential depended Ca2+ influx at variable extracellular calcium in type III taste cell Инвариантность потенциал-зависимого входа Са2+ во вкусовых клетках типа III по отношению к внеклеточному Са2+ Черкашин А П Cherkashin A P Хохлов А А Khokhlov A A Колесников С С Kolesnikov S S Рогачевская О А Rogachevskaja O A o.rogachevskaja@gmail.com Институт биофизики клетки РАН ru Institute of Cell Biophysics, Russian Academy of Sciences ru Институт биофизики клетки РАН ru Institute of Cell Biophysics, Russian Academy of Sciences ru Институт биофизики клетки РАН ru Institute of Cell Biophysics, Russian Academy of Sciences ru Институт биофизики клетки РАН ru Institute of Cell Biophysics, Russian Academy of Sciences ru 25 06 2017 25 06 2017 2 1 147 151 20 06 2017 20 06 2017 https://rusjbpc.ru/en/nauka/article/54137/view

Вкусовые клетки типа III образуют классические химические синапсы, в которых выброс нейромедиатора инициируется повышением внутриклеточного Са2+ за счет входа внеклеточного Са2+ через потенциал-зависимые (ПЗ) Са2+ каналы. Плотность упаковки клеток во вкусовой почке такова, что межклеточное пространство на два порядка меньше внутриклеточного. В силу этого, концентрации экстраклеточных ионов, включая ионы Са2+, могут значительно варьировать при изменении электрической активности клеток вкусовой почки за счет перераспределения ионов между цитоплазмой и межклеточной средой. В этом случае, надежность работы синапса в клетках типа III требует существования механизма, который бы обеспечивал относительную стабильность выброса нейромедиаторов условиях вариабельности внеклеточного Са2+ в физиологически адекватном диапазоне концентраций. С целью частичной проверки идеи инвариантности нами анализировались внутриклеточные Са2+ сигналы, генерируемые вкусовыми клетками типа III в ответ на стимуляцию при разных концентрациях внеклеточного Са2+. Оказалось, что как ПЗ Са2+ токи в клетках типа III, так и внутриклеточные Са2+ сигналы, инициирующие в дальнейшем секрецию нейромедиатора, остаются инвариантными при варьировании внеклеточного Са2+ в физиологическом диапазоне. Показано, что ПЗ Са2+ токи инварианты по отношению к концентрации внеклеточного Са2+ в диапазоне 1-2 мМ наружного Са2+, а увеличение концентрации внутриклеточного Са2+, вызванное электрической или неинвазивной деполяризацией KCl, инвариантно в диапазоне 0.5-5 мМ Са2+ во внеклеточной среде. Эти данные подтверждают существование во вкусовых клетках типа III не ясного на настоящий момент механизма, который может обеспечивать инвариантность секреции нейромедиаторов посредством обеспечения стабильности внутриклеточных Са2+ сигналов при разной концентрации ионов Са2+ в межклеточном пространстве.

Type III tastecells form classical chemical synapses and release neurotransmitter is initiated by employing exocytosis that is triggered by Ca2+ ions entering through voltage-gated (VG) Са2+-channels. The density of cell packing in the taste bud is such that the intercellular space is two orders of magnitude smaller than the intracellular one and, therefore, the concentration of extracellular ions, including Ca2+ ions, can vary considerably when the electrical activity of the taste buds changes due to the redistribution of ions between the cytoplasm and external medium. If this is the case, then the reliability of the synapse in type III cells requires the existence of a mechanism that would ensure the independence of the release of the neurotransmitter from the concentration of extracellular Ca2+ in the physiologically relevant range, that is, an increase in the intracellular Ca2+ concentration should be invariant with respect to extracellular Ca2+. To examine this idea, we analyzed intracellular Ca2+ signals generated by type III taste cells in response to stimulation at different concentrations of extracellular Ca2+. As was found, both VG Ca2+ currents in type III cells and intracellular Ca2+ signals, which subsequently trigger the release of the neurotransmitter, and its secretion proper, remain invariant when the extracellular Ca2+ varies in the physiological range. It is shown that the Ca2+ current is invariant with respect to the concentration of extracellular Ca2+ in the 1-2 mM range of the bath Ca2+, and for the curve of depolarization- induced increase in the concentration of intracellular Ca2+ from the concentration of the bath Ca2+ plateau is in the range 0.5-5 mM Ca2+. These data confirm the existence in the taste cells of type III is not clear at the moment the mechanism that can ensure the invariance of the secretion of neurotransmitters by ensuring the stability of intracellular Ca2+ signals at different concentrations of Ca2+ ions in the extracellular environment.

 вкусовые клетки кальциевая сигнализация экстраклеточный Са2+ ПЗ Са2+-каналы taste cells calcium signalization extracellular Са2+ VG Са 2+-channels

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