Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells
Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells
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DOI：
10.1152/jn.00835.2016
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发表时间：
2017-05-01
影响因子：
2.5
通讯作者：
Foskett, J. Kevin
中科院分区：
文献类型：
--
作者：
Ma, Zhongming;Saung, Wint Thu;Foskett, J. Kevin
味蕾II型细胞对尝味剂产生动作电位，通过电压门控calhm1相关离子通道触发非囊状ATP释放到味觉神经元。虽然CALHM1调节小鼠皮质神经元的兴奋性，但其在调节II型细胞兴奋性中的作用尚不清楚。在这项研究中，我们比较了从野生型（WT）和Calhm1敲除（KO）小鼠急性分离的单一鉴定的表达trpm5 - gfp的环颅乳头II型细胞的膜电导和动作电位。大电压门控向外电流的激活动力学在Calhm1 KO小鼠细胞中被加速，并且它们相关的非选择性尾电流，先前被证明与ATP释放高度相关，在Calhm1 KO细胞中完全不存在，这表明Calhm1对所有这些电流都有贡献。Calhm1缺失没有显著改变静息膜电位或输入电阻，也没有显著改变从动作电位估计或从稳态电压脉冲记录的Na+电流的振幅和动力学，或动作电位阈值、超调峰、后超极化和放电频率。然而，Calhm1的缺失减少了动作电位的半宽度，加速了瞬时外向电流的失活动力学，这表明Calhm1相关的电导在动作电位的复极化阶段被激活。CALHM1是II型味蕾细胞中ATP神经递质释放机制的重要离子通道组分。它对II型细胞静息膜性质和兴奋性的影响尚不清楚。先前与ATP释放相关的非选择性电压门控电流在缺乏CALHM1的细胞中不存在。Calhm1缺失对静息膜特性或电压门控的Na+和K+通道没有影响，但对动作电位动力学有轻微影响。
Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na+ currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials.NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na+ and K+ channels but contributed modestly to the kinetics of action potentials.