Zn²⁺ has been shown to have a wide range of modulatory effects on neuronal AMPARs. However, the mechanism of modulation is largely unknown. Here we show that Zn²⁺ inhibits GluA2(Q) homomeric receptors in an activity- and voltage-dependent manner, indicating a pore block mechanism. The rate of inhibition is slow, in the hundreds of milliseconds at millimolar Zn²⁺ concentrations; hence, the inhibition is only observed in the residual nondesensitizing currents. Consequently, the inhibition is higher for GluA2 receptors in complex with auxiliary subunits 2 and 8 where the residual activation is larger. The extent of inhibition is also dependent on charge at site 607, the site that undergoes RNA editing in GluA2 subunits replacing glutamine to arginine, with the percent inhibition being lower and IC₅₀ being higher for the edited GluA2(R) relative to unedited GluA2(Q) and to GluA2(Q607E), a mutation observed in the genetic screen of a patient exhibiting developmental delays. We also show that Zn²⁺ inhibition is significant during rapid repetitive activity with pulses of millimolar concentrations of glutamate in both receptors expressed in HEK cells as well as in native receptors in cortical neurons of C57BL/6J mice of either sex, indicating a physiological relevance of this inhibition.

SIGNIFICANCE STATEMENT Zn²⁺ is present along with glutamate in synaptic vesicles and coreleased during synaptic transmission, modulating the postsynaptic ionotropic glutamate receptors. While Zn²⁺ inhibition of the NMDA subtype of the ionotropic glutamate receptors is well characterized, the mechanism of modulation of the AMPA subtype is much less known. Here we have systematically studied Zn²⁺ inhibition of AMPARs by varying calcium permeability, auxiliary subunits, and activation levels and show that Zn²⁺ inhibits AMPARs in an activity-dependent manner, opening up this pathway as a means to pharmacologically modulate the receptors.

Zn ²⁺已被证明对神经元AMPAR具有广泛的调节作用。但是，调制机制很大程度上未知。在这里，我们显示Zn ²⁺以活性和电压依赖性方式抑制GluA2（Q）同源受体，表明了孔阻断机制。抑制速率很慢，在毫摩尔的Zn ^2+上为数百毫秒浓度 因此，只能在残留的非脱敏电流中观察到抑制作用。因此，与GluA2受体结合的辅助活性较高的辅助亚基2和8的抑制作用更高。抑制的程度还取决于位点607的电荷，该位点在GluA2亚基中进行RNA编辑的位置将谷氨酰胺替换为精氨酸，相对于未编辑的GluA2（R），抑制的百分比更低，IC ₅₀更高。 Q）和GluA2（Q607E），这是在表现出发育延迟的患者的基因筛查中发现的突变。我们还表明Zn ²⁺在快速重复活动中，抑制作用很明显，在HEK细胞和两种性别的C57BL / 6J小鼠的皮质神经元中表达的两种受体中，都存在毫摩尔浓度的谷氨酸的脉冲，表明这种抑制作用的生理学意义。

重要声明Zn ²⁺与谷氨酸一起存在于突触小泡中，并在突触传递过程中共释放，从而调节突触后的离子型谷氨酸受体。尽管Zn ²⁺对离子型谷氨酸受体的NMDA亚型的抑制作用已得到很好的表征，但AMPA亚型的调节机制却鲜为人知。在这里，我们通过改变钙渗透性，辅助亚基和激活水平，系统研究了AMPAR的Zn ²⁺抑制作用，并表明Zn ²⁺以活性依赖的方式抑制AMPARs，开辟了这一途径，作为药理调节受体的一种途径。