Edmonds B, Reyes R, Schwaller B, Roberts W M
Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403, USA.
Nat Neurosci. 2000 Aug;3(8):786-90. doi: 10.1038/77687.
To determine whether the concentrations of calcium-binding proteins present in some neurons and sensory cells are sufficient to influence presynaptic calcium signaling, we studied the predominant calcium-binding protein in a class of sensory hair cells in the frog ear. Based on antibody affinity and molecular weight, we identified this protein as calretinin. We measured its cytoplasmic concentration to be approximately 1.2 mM, sufficient to bind approximately 6 mM Ca2+. Calcium signaling was altered when the diffusible cytoplasmic components were replaced by an intracellular solution lacking any fast calcium buffer, and was restored by the addition of 1.2 mM exogenous calretinin to the intracellular solution. We conclude that calretinin, when present at millimolar concentration, can serve as a diffusionally mobile calcium buffer/transporter capable of regulating calcium signaling over nanometer distances at presynaptic sites.
为了确定某些神经元和感觉细胞中存在的钙结合蛋白浓度是否足以影响突触前钙信号传导，我们研究了蛙耳一类感觉毛细胞中的主要钙结合蛋白。基于抗体亲和力和分子量，我们将该蛋白鉴定为钙视网膜蛋白。我们测量其细胞质浓度约为1.2 mM，足以结合约6 mM Ca2+。当用缺乏任何快速钙缓冲剂的细胞内溶液替代可扩散的细胞质成分时，钙信号传导发生改变，并通过向细胞内溶液中添加1.2 mM外源性钙视网膜蛋白得以恢复。我们得出结论，当以毫摩尔浓度存在时，钙视网膜蛋白可作为一种能够在突触前位点调节纳米距离上钙信号传导的扩散移动性钙缓冲剂/转运体。
