β Ca2+/CaM-dependent kinase type II triggers upregulation of GluA1 to coordinate adaptation to synaptic inactivity in hippocampal neurons
β Ca2+/CaM-dependent kinase type II triggers upregulation of GluA1 to coordinate adaptation to synaptic inactivity in hippocampal neurons
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DOI：
10.1073/pnas.1018022108
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发表时间：
2011-01-11
影响因子：
11.1
通讯作者：
Tsien, Richard W.
中科院分区：
文献类型：
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作者：
Groth, Rachel D.;Lindskog, Maria;Tsien, Richard W.
在海马神经元培养中，长时间阻断AMPA受体导致突触后GluA1表达增加，突触前囊泡池大小和周转率增加，这是一种超越简单突触缩放的适应性变化。作为一种分子机制，突触不活跃时，β-钙/钙调素依赖的第二类激动型蛋白(β-CaMKII)的表达增加。在这里，我们开始阐明βCaMKII在适应的各种表现中的作用。通过慢病毒介导的shRNA表达下调βCaMKII可以阻止突触静止诱导的GluA1增加，CaM激酶抑制剂KN-93的处理也是如此，但不能阻止非活性类似物KN-92的处理。这些结果表明，在AMPA受体阻断的刺激下，βCaMKII的上调促进了GluA1表达的增加。事实上，转导βCaMKII，但不是激酶死亡的突变体，增加了树突上GluA1的表达，并提高了小泡翻转(SYT-Ab摄取)，模拟了突触两侧突触不活跃的影响。在βCaMKII升高的细胞中，突触活性阻断的解除揭示了微小的兴奋性突触后电流频率的增加，这种电流可以被PhTx阻断GluA1受体迅速和完全抑制。这种微小频率的增加涉及到真正的突触前增强，而不仅仅是突触数量的增加。这一发现表明，通过GluA1受体的钙离子流动可能触发逆行信使的急性释放。综上所述，我们的结果表明，突触不活跃诱导的βCaMKII表达增加启动了一系列事件，最终导致突触传递中突触前和突触后的协调适应。
Prolonged AMPA-receptor blockade in hippocampal neuron cultures leads to both an increased expression of GluA1 postsynaptically and an increase in vesicle pool size and turnover rate presynaptically, adaptive changes that extend beyond simple synaptic scaling. As a molecular correlate, expression of the beta Ca2+/CaM-dependent kinase type II (beta CaMKII) is increased in response to synaptic inactivity. Here we set out to clarify the role of beta CaMKII in the various manifestations of adaptation. Knockdown of beta CaMKII by lentiviral-mediated expression of shRNA prevented the synaptic inactivity-induced increase in GluA1, as did treatment with the CaM kinase inhibitor KN-93, but not the inactive analog KN-92. These results demonstrate that, spurred by AMPA-receptor blockade, up-regulation of beta CaMKII promotes increased GluA1 expression. Indeed, transfection of beta CaMKII, but not a kinase-dead mutant, increased GluA1 expression on dendrites and elevated vesicle turnover (Syt-Ab uptake), mimicking the effect of synaptic inactivity on both sides of the synapse. In cells with elevated beta CaMKII, relief of synaptic-activity blockade uncovered an increase in the frequency of miniature excitatory postsynaptic currents that could be rapidly and fully suppressed by PhTx blockade of GluA1 receptors. This increased mini frequency involved a genuine presynaptic enhancement, not merely an increased abundance of synapses. This finding suggests that Ca2+ flux through GluA1 receptors may trigger the acute release of a retrograde messenger. Taken together, our results indicate that synaptic inactivity-induced increases in beta CaMKII expression set in motion a series of events that culminate in coordinated pre- and postsynaptic adaptations in synaptic transmission.