Spatial calcium buffering in saccular hair cells
Spatial calcium buffering in saccular hair cells
复制标题
囊状毛细胞的空间钙缓冲
作者：
W. M. Roberts
细胞内钙结合蛋白在快速和高度局部化的Ca 2+信号传导中的潜在重要性知之甚少。在快速突触传递过程中，发生在专门的活性区，其中Ca 2+从通道扩散到神经递质释放位点仅几十纳米1，细胞质Ca 2+缓冲液必须非常快或以毫摩尔浓度存在，以拦截通往其靶点的显著部分的钙离子2 -5。因此，Ca 2+缓冲已被认为是不重要的快速exocytosis 1，6，7和另一个快速钙介导的过程，在毛细胞的电共振4，8。在这里，我提出相反的证据表明，在青蛙球囊的毛细胞中含有毫摩尔浓度的移动的细胞质钙缓冲液，捕获后几微秒内通过突触前钙离子通道进入Ca 2+，并进行它远离入口点。这种空间缓冲作用使突触前游离钙离子减少了60%，并可能将内部钙离子浓度超过1 μM的区域限制在每个突触部位的<250 nm范围内。因此，缓冲器可以影响电共振和突触传递。钙结合蛋白-D28 K或相关蛋白可作为移动的钙缓冲剂，其作用类似于其在跨肠上皮细胞转运Ca 2+中的功能。
THE potential importance of intracellular calcium-binding proteins in rapid and highly localized Ca2+ signalling is poorly understood. During fast synaptic transmission, which occurs at specialized active zones where Ca2+ diffuses only a few tens of nanometres from channels to neurotransmitter release sites1, a cytoplasmic Ca2+ buffer would have to be extremely fast or present in millimolar concentrations to intercept a significant fraction of the calcium ions en route to their targets2–5. Therefore, Ca2+ buffers have been presumed to be unimportant in fast exocytosis1,6,7 and another fast calcium-mediated process, electrical resonance in hair cells4,8. Here I present evidence to the contrary by showing that hair cells in the frog sacculus contain millimolar concentrations of a mobile cytoplasmic calcium buffer that captures Ca2+ within a few microseconds after it enters through presynaptic Ca2+ channels and carries it away from the point of entry. This spatial buffering reduces the presynaptic free Ca2+ by up to 60 per cent and probably restricts the region in which the internal calcium ion concentration exceeds 1 μM to within <250 nm of each synaptic site. The buffer can thus influence both electrical resonance and synaptic transmission. Calbindin-D28K or a related protein may serve as the mobile calcium buffer, an action similar to its function in transporting Ca2+ across intestinal epithelial cells.
28 kDa 钙结合蛋白-D 是雏鸡基底乳头中的主要钙结合蛋白。
DOI：
10.1073/pnas.85.10.3387
发表时间：
1988
影响因子：
11.1
作者：
Oberholtzer,JC;Buettger,C;Summers,MC;Matschinsky,FM
通讯作者：
Matschinsky,FM
Calbindin-D28K 是一种 1 α,25-二羟基维生素 D3 诱导的钙结合蛋白，以高亲和力结合 5 或 6 个 Ca2 离子。
DOI：
--
发表时间：
1990
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Leathers,VL;Linse,S;Forsén,S;Norman,AW
通讯作者：
Norman,AW