Calbindin D28k targets myo-inositol monophosphatase in spines and dendrites of cerebellar Purkinje neurons
Calbindin D28k targets myo-inositol monophosphatase in spines and dendrites of cerebellar Purkinje neurons
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DOI：
10.1073/pnas.0407855102
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发表时间：
2005-04-19
影响因子：
11.1
通讯作者：
Eilers, J
中科院分区：
文献类型：
--
作者：
Schmidt, H;Schwaller, B;Eilers, J
Ca 2+结合蛋白calbindin D28 k（CB）对中枢神经系统的正常功能至关重要，但其具体功能作用在很大程度上尚不清楚。CB通常被描述为一个移动的Ca 2+缓冲器，它塑造了细胞Ca 2+信号的时空范围。然而，最近的生物化学数据表明，CB也具有Ca 2+传感器的特性，并激活肌醇单磷酸酶（IMPase），肌醇-1，4，5-三磷酸信号级联的关键酶，以及在治疗双相情感障碍中的情绪稳定药物的假定靶点。在这里，我们表明，CB相互作用与IMPase小脑浦肯野神经元，细胞类型众所周知，依赖于肌醇-1，4，5-三磷酸依赖性突触整合。定量的染料标记的CB与双光子荧光恢复后的光漂白的流动性显示，CB的很大一部分是固定在脊柱和树突，但不是在轴突。固定发生在几秒钟内，增加阈上突触活动，并可以缓解合成肽，类似于推定的CB-结合位点的IMP酶，表明CB结合固定的IMP酶。CB的表观扩散系数的测量意味着CB不与胞质IMPase相互作用，或者后者仅以微量存在于浦肯野神经元的棘状树突中。我们的研究结果表明，CB作为一个活动依赖性的传感器，靶向膜/cytochronon结合的IMPase在中枢神经元。
The Ca2+-binding protein calbindin D28k (CB) is vital for the normal function of the central nervous system but its specific functional role is largely unclear. CB is typically described as a mobile Ca2+ buffer that shapes the spatiotemporal extent of cellular Ca2+ signals. Recent biochemical data, however, indicate that CB also has characteristics of a Ca2+ sensor and activates myo-inositol monophosphatase (IMPase), a key enzyme of the inositol-1,4,5-trisphosphate signaling cascade and an assumed target of mood-stabilizing drugs in the treatment of bipolar disorder. Here, we show that CB interacts with IMPase in cerebellar Purkinje neurons, a cell type well known to rely on inositol-1,4,5-trisphosphate-dependent synaptic integration. Quantification of the mobility of dye-labeled CB with two-photon fluorescence recovery after photobleaching revealed that a substantial fraction of CB is immobilized in spines and dendrites, but not in axons. Immobilization occurs over several seconds, is increased by suprathreshold synaptic activity, and can be relieved by a synthetic peptide that resembles the putative CB-binding site of IMPase, indicating that CB binds to immobilized IMPase. Measurements of the apparent diffusion coefficients of CB imply that CB does not interact with cytosolic IMPase or that the latter is present only in minute amounts in the spiny dendrites of Purkinje neurons. Our results suggest that CB acts as an activity-dependent sensor that targets membrane/cytoskeleton-bound IMPase in central neurons.