Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom.
J Neurosci. 2010 Sep 22;30(38):12856-67. doi: 10.1523/JNEUROSCI.2700-10.2010.
The α2δ subunits of voltage-gated calcium channels are important modulatory subunits that enhance calcium currents and may also have other roles in synaptogenesis. The antiepileptic and antiallodynic drug gabapentin (GBP) binds to the α2δ-1 and α2δ-2 isoforms of this protein, and its binding may disrupt the binding of an endogenous ligand, required for their correct function. We have shown previously that GBP produces a chronic inhibitory effect on calcium currents by causing a reduction in the total number of α2δ and α1 subunits at the cell surface. This action of GBP is likely to be attributable to a disruption of the trafficking of α2δ subunits, either to or from the plasma membrane. We studied the effect of GBP on the internalization of, and insertion into the plasma membrane of α2δ-2 using an α-bungarotoxin binding site-tagged α2δ-2 subunit, and a fluorescent derivative of α-bungarotoxin. We found that GBP specifically disrupts the insertion of α2δ-2 from post-Golgi compartments to the plasma membrane, and this effect was prevented by a mutation of α2δ-2 that abolishes its binding to GBP. The coexpression of the GDP-bound Rab11 S25N mutant prevented the GBP-induced decrease in α2δ-2 cell surface levels, both in cell lines and in primary neurons, and the GBP-induced reduction in calcium channel currents. In contrast, the internalization of α2δ-2 was unaffected by GBP. We conclude that GBP acts by preventing the recycling of α2δ-2 from Rab11-positive recycling endosomes to the plasma membrane.
电压门控钙通道的α2δ亚基是重要的调节亚基,可增强钙电流,在突触发生中可能还有其他作用。抗癫痫药和抗痛觉过敏药物加巴喷丁(GBP)与该蛋白的α2δ-1 和 α2δ-2 同工型结合,其结合可能会破坏其正确功能所需的内源性配体的结合。我们之前已经表明,GBP 通过减少细胞表面上的α2δ和α1 亚基的总数来产生对钙电流的慢性抑制作用。GBP 的这种作用可能归因于α2δ 亚基从质膜内向质膜外向或从质膜内向质膜内的运输中断。我们使用α-银环蛇毒素结合位点标记的α2δ-2 亚基和α-银环蛇毒素的荧光衍生物研究了 GBP 对α2δ-2 内化和插入质膜的影响。我们发现 GBP 特异性地破坏了从高尔基体后区室插入到质膜的α2δ-2 的插入,并且这种作用被一种消除其与 GBP 结合的α2δ-2 突变所阻止。GDP 结合的 Rab11 S25N 突变体的共表达可防止 GBP 诱导的α2δ-2 细胞表面水平降低,无论是在细胞系还是原代神经元中,以及 GBP 诱导的钙通道电流减少。相比之下,GBP 对α2δ-2 的内化没有影响。我们得出结论,GBP 通过防止α2δ-2 从 Rab11 阳性再循环内体再循环到质膜来发挥作用。