Laboratoire Physiologie Cellulaire de la Synapse, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5091, Bordeaux Neuroscience Institute, University of Bordeaux, 33076 Bordeaux, France.
J Neurosci. 2009 Dec 9;29(49):15499-510. doi: 10.1523/JNEUROSCI.2724-09.2009.
The properties of synaptic receptors determine their mode of action at presynaptic and postsynaptic loci. Here, we investigated the atypical biophysical properties of GluK3-containing kainate receptors, which contribute to presynaptic facilitation at hippocampal mossy fiber synapses. We show, using fast glutamate applications on outside-out patches and kinetic modeling, that the low sensitivity of GluK3 receptors for glutamate is attributable to fast desensitization of partially bound receptors. Consequently, these receptors can only be activated by fast transients of high glutamate concentration. In addition, GluK3 receptors are very sensitive to voltage-dependent block by intracellular spermine that precludes activation of substantial currents at potentials positive to -50 mV. Two specific residues within the channel pore define this high-affinity site. Finally, GluK3 are calcium permeable in the same way as unedited GluK2 receptors. These receptors present unique properties among AMPA/kainate receptors that could reflect a specialized presynaptic function.
突触受体的性质决定了它们在突触前和突触后部位的作用方式。在这里，我们研究了包含 GluK3 的 kainate 受体的非典型生物物理特性，这些特性有助于海马苔藓纤维突触的突触前易化。我们使用在外部薄片上的快速谷氨酸应用和动力学建模表明，GluK3 受体对谷氨酸的低敏感性归因于部分结合受体的快速脱敏。因此，这些受体只能被高谷氨酸浓度的快速瞬态激活。此外，GluK3 受体对细胞内 spermine 的电压依赖性阻断非常敏感，这阻止了在 -50 mV 以上的电位下激活大量电流。通道孔内的两个特定残基定义了这个高亲和力位点。最后，GluK3 像未经编辑的 GluK2 受体一样，是钙可渗透的。这些受体在 AMPA/kainate 受体中具有独特的性质，这可能反映了一种特殊的突触前功能。
