Mutational analysis of dendritic Ca2+ kinetics in rodent Purkinje cells:: role of parvalbumin and calbindin D28k
Mutational analysis of dendritic Ca2+ kinetics in rodent Purkinje cells:: role of parvalbumin and calbindin D28k
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DOI：
10.1113/jphysiol.2002.035824
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发表时间：
2003-08-15
影响因子：
5.5
通讯作者：
Eilers, J
中科院分区：
文献类型：
--
作者：
Schmidt, H;Stiefel, KM;Eilers, J
利用高分辨率共聚焦钙离子成像技术对小脑浦肯野细胞（PC）棘状树突中攀爬纤维介导的钙瞬变动力学机制进行了定量研究。将小清蛋白（PV-/-）和小清蛋白/钙结合蛋白D-28 k无效突变体（PV/CB-/-）小鼠中的Ca 2+动力学与野生型（WT）动物中的反应进行比较。在WT中，树突状干中的Ca 2+瞬变的特征在于双指数衰减动力学，其不是由于缓冲的Ca 2+扩散或指示剂染料的饱和。PV-/-PC中的Ca 2+瞬变达到与WT中相同的峰值幅度，但衰减的双相性质不太明显，这种效应可归因于PV的缓慢结合动力学。相比之下，PV/CB-/-PC中的峰值幅度比WT中高约两倍，并且衰减变得接近双相。数值模拟表明，从一个单一的指数衰减PV/CB-/-的残留偏差是由于饱和的Ca 2+指示剂染料。此外，模拟暗示，未表征的内源性Ca 2+结合蛋白的影响是可以忽略不计的，缓冲扩散和染料饱和显着影响棘Ca 2+瞬变，但不是那些在树突轴，CB和PV都没有经历饱和的棘或树突在攀登纤维诱发的Ca 2+瞬变。钙结合蛋白的中等亲和力结合位点足够快以降低Ca 2+信号的峰值幅度。然而，类似于PV，CB的延迟结合导致双相Ca 2+衰减动力学。我们的研究结果表明，不同的动力学PV和CB的基础上突触诱发的钙瞬变的双相动力学的树突状细胞轴。
The mechanisms governing the kinetics of climbing fibre-mediated Ca2+ transients in spiny dendrites of cerebellar Purkinje cells (PCs) were quantified with high-resolution confocal Ca2+ imaging. Ca2+ dynamics in parvalbumin (PV-/-) and parvalbumin/calbindin D-28k null-mutant (PV/CB-/-) mice were compared with responses in wild-type (WT) animals. In the WT, Ca2+ transients in dendritic shafts were characterised by double exponential decay kinetics that were not due to buffered Ca2+ diffusion or saturation of the indicator dye. Ca2+ transients in PV-/- PCs reached the same peak amplitude as in the WT but the biphasic nature of the decay was less pronounced, an effect that could be attributed to PV's slow binding kinetics. In contrast, peak amplitudes in PV/CB-/- PCs were about two times higher than in the WT and the decay became nearly monophasic. Numerical simulations indicate that the residual deviation from a single exponential decay in PV/CB-/- is due to saturation of the Ca2+ indicator dye. Furthermore, the simulations imply that the effect of uncharacterised endogenous Ca2+ binding proteins is negligible, that buffered diffusion and dye saturation significantly affects spineous Ca2+ transients but not those in the dendritic shafts, and that neither CB nor PV undergoes saturation in spines or dendrites during climbing fibre-evoked Ca2+ transients. Calbindin's medium-affinity binding sites are fast enough to reduce the peak amplitude of the Ca2+ signal. However, similar to PV, delayed binding by CB leads to biphasic Ca2+ decay kinetics. Our results suggest that the distinct kinetics of PV and CB underlie the biphasic kinetics of synaptically evoked Ca2+ transients in dendritic shafts of PCs.