The Electrogenic Sodium Bicarbonate Cotransporter NBCe1 Is a High-Affinity Bicarbonate Carrier in Cortical Astrocytes
The Electrogenic Sodium Bicarbonate Cotransporter NBCe1 Is a High-Affinity Bicarbonate Carrier in Cortical Astrocytes
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DOI：
10.1523/jneurosci.2377-13.2014
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发表时间：
2014-01-22
影响因子：
5.3
通讯作者：
Deitmer, Joachim W.
中科院分区：
文献类型：
--
作者：
Theparambil, Shefeeq M.;Ruminot, Ivan;Deitmer, Joachim W.
电致碳酸氢钠共转运体NBCe1 （SLC4A4）是细胞内H+的强大调节剂，也是许多细胞类型中重要的碱基载体。我们使用野生型（WT）和NBCe1缺陷（NBCe1- ko）小鼠，在广角共聚焦显微镜下，利用H+敏感染料BCECF[2',7' -双-（羧乙基）-5-（和6）-羧荧光素]监测细胞内H+，研究了NBCe1在培养和原位皮层星形胶质细胞中的作用。将0.1-3 mM HCO3-加入o -2气体、hepe -缓冲的生理盐水溶液中，WT星形胶质细胞内H+浓度降低，K-m为0.65 mM HCO3-，但NBCe1-KO星形胶质细胞内H+浓度缓慢升高(1)。在非洲爪蟾卵母细胞中异种表达的人nbce1可以通过添加1-3mM的HCO3-激活，甚至可以通过在名义上不含CO2/HCO3的盐水溶液中添加残余的HCO3-激活。我们的研究结果表明，NBCe1在皮质星形胶质细胞中介导了令人惊讶的高表观碳酸氢盐敏感性，这表明NBCe1可能在这些细胞中广泛的碳酸氢盐浓度下起作用。
The electrogenic sodium bicarbonate cotransporter NBCe1 (SLC4A4) is a robust regulator of intracellular H+ and a significant base carrier in many cell types. Using wild-type (WT) and NBCe1-deficient (NBC-KO) mice, we have studied the role of NBCe1 in cortical astrocytes in culture and in situ by monitoring intracellular H+ using the H+-sensitive dye BCECF [2',7' -bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein] in wide-field and confocal microscopy. Adding 0.1-3 mM HCO3- to an O-2-gassed, HEPES-buffered saline solution lowered the intracellular H+ concentration with a K-m of 0.65 mM HCO3- in WT astrocytes, but slowly raised [H+](1) in NBCe1-KO astrocytes. HumanNBCe1 heterologously expressed in Xenopus oocytes could be activated by adding 1-3mM HCO3-, and even by residual HCO3- in a nominally CO2/HCO3--free saline solution. Our results demonstrate a surprisingly high apparent bicarbonate sensitivity mediated by NBCe1 in cortical astrocytes, suggesting that NBCe1 may operate over a wide bicarbonate concentration in these cells.