Oertner Thomas G, Matus Andrew
Friedrich Miescher Institute, 4058 Basel, Switzerland.
Cell Calcium. 2005 May;37(5):477-82. doi: 10.1016/j.ceca.2005.01.016.
Most excitatory synapses in the brain are made on spines, small protrusions from dendrites that exist in many different shapes and sizes. Spines are highly motile, a process that reflects rapid rearrangements of the actin cytoskeleton inside the spine, and can also change shape and size over longer timescales. These different forms of morphological plasticity are regulated in an activity-dependent way, involving calcium influx through glutamate receptors and voltage-gated calcium channels. Many proteins regulating the turnover of filamentous actin (F-actin) are calcium-dependent and might transduce intracellular calcium levels into spine shape changes. On the other hand, the morphology of a spine might affect the function of the synapse residing on it. In particular, the induction of synaptic plasticity is known to require large elevations in the postsynaptic calcium concentration, which depend on the ability of the spine to compartmentalize calcium. Since the actin cytoskeleton is also known to anchor postsynaptic glutamate receptors, changes in the actin polymerization state have the potential to influence synaptic function in a number of ways. Here we review the most prominent types of changes in spine morphology in hippocampal pyramidal cells with regard to their calcium-dependence and discuss their potential impact on synaptic function.
大脑中大多数兴奋性突触都形成于树突棘上，树突棘是从树突伸出的小突起，有许多不同的形状和大小。树突棘具有高度的动态性，这一过程反映了树突棘内部肌动蛋白细胞骨架的快速重排，并且在较长时间尺度上也能改变形状和大小。这些不同形式的形态可塑性以活动依赖的方式受到调节，涉及通过谷氨酸受体和电压门控钙通道的钙内流。许多调节丝状肌动蛋白（F-肌动蛋白）周转的蛋白质是钙依赖性的，可能将细胞内钙水平转化为树突棘形状的变化。另一方面，树突棘的形态可能会影响位于其上的突触的功能。特别是，已知突触可塑性的诱导需要突触后钙浓度大幅升高，这取决于树突棘分隔钙的能力。由于肌动蛋白细胞骨架也已知能锚定突触后谷氨酸受体，肌动蛋白聚合状态的变化有可能以多种方式影响突触功能。在这里，我们回顾了海马锥体细胞中树突棘形态最显著的变化类型及其钙依赖性，并讨论它们对突触功能的潜在影响。
