DOC2A and DOC2B are sensors for neuronal activity with unique calcium-dependent and kinetic properties
DOC2A and DOC2B are sensors for neuronal activity with unique calcium-dependent and kinetic properties
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DOI：
10.1111/j.1471-4159.2006.03755.x
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发表时间：
2006-05-01
影响因子：
4.7
通讯作者：
Verhage, M
中科院分区：
文献类型：
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作者：
Groffen, AJA;Friedrich, R;Verhage, M
细胞内钙浓度（[Ca2+](i)）升高至低于1 μ m的水平会改变突触传递并诱导短期可塑性。为了确定参与这一信号传导的钙传感器，我们研究了可溶性C2结构域蛋白，发现DOC2A和DOC2B都受到亚微摩尔钙水平的调节。荧光标记的DOC2A和DOC2B在[Ca2+](i)升高后易位到质膜。在共表达这两种亚型的细胞中，DOC2B易位先于DOC2A易位。DOC2A和DOC2B的半最大易位分别发生在450和175 nm[Ca2+](i)处。这种钙敏感性的巨大差异伴随着适度的动力学差异（分别为2.6 s和2.0 s）。DOC2异构体的钙敏感性可以通过预测其C2A结构域的拓扑结构来解释。同样，DOC2B中天冬氨酸D218和D220的中和改变了其钙亲和力。在神经元中，这两种DOC2亚型在动作电位序列中被可逆地招募到质膜上。与其较高的钙敏感性一致，DOC2B在较低的去极化频率下易位。海马体神经元苯乙烯染料摄取实验表明，DOC2B突变的过表达改变了突触活性。我们得出结论，DOC2A和DOC2B都受神经元活动的调节，并假设它们的钙依赖性易位可能调节突触活动。
Elevation of the intracellular calcium concentration ([Ca2+](i)) to levels below 1 mu m alters synaptic transmission and induces short-term plasticity. To identify calcium sensors involved in this signalling, we investigated soluble C2 domain-containing proteins and found that both DOC2A and DOC2B are modulated by submicromolar calcium levels. Fluorescent-tagged DOC2A and DOC2B translocated to plasma membranes after [Ca2+](i) elevation. DOC2B translocation preceded DOC2A translocation in cells co-expressing both isoforms. Half-maximal translocation occurred at 450 and 175 nm[Ca2+](i) for DOC2A and DOC2B, respectively. This large difference in calcium sensitivity was accompanied by a modest kinetic difference (halftimes, respectively, 2.6 and 2.0 s). The calcium sensitivity of DOC2 isoforms can be explained by predicted topologies of their C2A domains. Consistently, neutralization of aspartates D218 and D220 in DOC2B changed its calcium affinity. In neurones, both DOC2 isoforms were reversibly recruited to the plasma membrane during trains of action potentials. Consistent with its higher calcium sensitivity, DOC2B translocated at lower depolarization frequencies. Styryl dye uptake experiments in hippocampal neurones suggest that the overexpression of mutated DOC2B alters the synaptic activity. We conclude that both DOC2A and DOC2B are regulated by neuronal activity, and hypothesize that their calcium-dependent translocation may regulate synaptic activity.