PDF(Pubmed)
Abstract：
Following prolonged activity blockade, amplitudes of miniature excitatory postsynaptic currents (mEPSCs) increase, a form of plasticity termed \"homeostatic synaptic plasticity.\" We previously showed that a presynaptic protein, the small GTPase Rab3A, is required for full expression of the increase in miniature endplate current amplitudes following prolonged blockade of action potential activity at the mouse neuromuscular junction in vivo (Wang et al., 2011), but it is unknown whether this form of Rab3A-dependent homeostatic plasticity shares any characteristics with central synapses. We show here that homeostatic synaptic plasticity of mEPSCs is impaired in mouse cortical neuron cultures prepared from Rab3A-/- and mutant mice expressing a single point mutation of Rab3A, Rab3A Earlybird mice. To determine if Rab3A is involved in the well-established homeostatic increase in postsynaptic AMPA-type receptors (AMPARs), we performed a series of experiments in which electrophysiological recordings of mEPSCs and confocal imaging of synaptic AMPAR immunofluorescence were assessed within the same cultures. We found that Rab3A was required for the increase in synaptic AMPARs following prolonged activity blockade, but the increase in mEPSC amplitudes was not always accompanied by an increase in postsynaptic AMPAR levels, suggesting other factors may contribute. Finally, we demonstrate that Rab3A is acting in neurons because only selective loss of Rab3A in neurons, not glia, disrupted the homeostatic increase in mEPSC amplitudes. This is the first demonstration that neuronal Rab3A is required for homeostatic synaptic plasticity and that it does so partially through regulation of the surface expression of AMPA receptors.
摘要：
在长时间的活动封锁之后，微型兴奋性突触后电流（mEPSC）的振幅增加，一种称为“稳态突触可塑性”的可塑性形式。“我们之前证明了一种突触前蛋白，小GTPaseRab3A,在体内小鼠神经肌肉接头处的动作电位活性被长期阻断后，微型终板电流幅度的增加是完全表达所必需的（Wang等人。,2011),但目前尚不清楚这种形式的依赖Rab3A的稳态可塑性是否与中枢突触具有任何特征。我们在这里表明，mEPSCs的稳态突触可塑性在从Rab3A-/-和表达Rab3A单点突变的突变小鼠制备的小鼠皮质神经元培养物中受损，Rab3AEarlybird小鼠。为了确定Rab3A是否参与突触后AMPARA型受体（AMPAR）的稳态增加，我们进行了一系列实验,在相同培养物中评估mEPSC的电生理记录和突触AMPAR免疫荧光的共聚焦成像.我们发现，在长时间的活动阻断后，突触AMPAR的增加需要Rab3A，但是mEPSC振幅的增加并不总是伴随着突触后AMPAR水平的增加，暗示其他因素可能有贡献。最后,我们证明Rab3A在神经元中起作用，因为只有神经元中Rab3A的选择性丧失，不是胶质,破坏了mEPSC振幅的稳态增加。这是首次证明神经元Rab3A是稳态突触可塑性所必需的，并且部分地通过调节AMPA受体的表面表达来实现。
