Hendrich Jan, Van Minh Alexandra Tran, Heblich Fay, Nieto-Rostro Manuela, Watschinger Katrin, Striessnig Jörg, Wratten Jack, Davies Anthony, Dolphin Annette C
Laboratory for Cellular and Molecular Neuroscience, Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom.
Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3628-33. doi: 10.1073/pnas.0708930105. Epub 2008 Feb 25.
The mechanism of action of the antiepileptic and antinociceptive drugs of the gabapentinoid family has remained poorly understood. Gabapentin (GBP) binds to an exofacial epitope of the alpha(2)delta-1 and alpha(2)delta-2 auxiliary subunits of voltage-gated calcium channels, but acute inhibition of calcium currents by GBP is either very minor or absent. We formulated the hypothesis that GBP impairs the ability of alpha(2)delta subunits to enhance voltage-gated Ca(2+)channel plasma membrane density by means of an effect on trafficking. Our results conclusively demonstrate that GBP inhibits calcium currents, mimicking a lack of alpha(2)delta only when applied chronically, but not acutely, both in heterologous expression systems and in dorsal root-ganglion neurons. GBP acts primarily at an intracellular location, requiring uptake, because the effect of chronically applied GBP is blocked by an inhibitor of the system-L neutral amino acid transporters and enhanced by coexpression of a transporter. However, it is mediated by alpha(2)delta subunits, being prevented by mutations in either alpha(2)delta-1 or alpha(2)delta-2 that abolish GBP binding, and is not observed for alpha(2)delta-3, which does not bind GBP. Furthermore, the trafficking of alpha(2)delta-2 and Ca(V)2 channels is disrupted both by GBP and by the mutation in alpha(2)delta-2, which prevents GBP binding, and we find that GBP reduces cell-surface expression of alpha(2)delta-2 and Ca(V)2.1 subunits. Our evidence indicates that GBP may act chronically by displacing an endogenous ligand that is normally a positive modulator of alpha(2)delta subunit function, thereby impairing the trafficking function of the alpha(2)delta subunits to which it binds.
加巴喷丁类抗癫痫和抗伤害感受药物的作用机制一直未被充分理解。加巴喷丁（GBP）与电压门控钙通道的α(2)δ-1和α(2)δ-2辅助亚基的胞外表位结合，但GBP对钙电流的急性抑制作用很轻微或不存在。我们提出了一个假设，即GBP通过影响转运过程来损害α(2)δ亚基增强电压门控Ca(2+)通道质膜密度的能力。我们的结果确凿地表明，GBP抑制钙电流，仅在长期应用而非急性应用时，在异源表达系统和背根神经节神经元中模拟缺乏α(2)δ的情况。GBP主要作用于细胞内位点，需要摄取，因为长期应用GBP的作用被系统-L中性氨基酸转运体抑制剂阻断，并因转运体的共表达而增强。然而，它是由α(2)δ亚基介导的，α(2)δ-1或α(2)δ-2中的突变消除GBP结合可阻止这种作用，而对于不结合GBP的α(2)δ-3则未观察到这种作用。此外，GBP和α(2)δ-2中阻止GBP结合的突变均会破坏α(2)δ-2和Ca(V)2通道的转运，并且我们发现GBP会降低α(2)δ-2和Ca(V)2.1亚基的细胞表面表达。我们的证据表明，GBP可能通过取代通常是α(2)δ亚基功能正向调节剂的内源性配体而长期发挥作用，从而损害其结合的α(2)δ亚基的转运功能。
