δ subunit susceptibility variants E177A and R220H associated with complex epilepsy alter channel gating and surface expression of α4β2δ GABAA receptors
δ subunit susceptibility variants E177A and R220H associated with complex epilepsy alter channel gating and surface expression of α4β2δ GABAA receptors
复制标题
DOI：
10.1523/jneurosci.2913-05.2006
复制
发表时间：
2006-02-01
影响因子：
5.3
通讯作者：
Macdonald, RL
中科院分区：
文献类型：
--
作者：
Feng, HJ;Kang, JQ;Macdonald, RL
大多数人类特发性全身性癫痫（IGEs）是多基因的，但几乎没有什么是已知的分子基础的任何复杂的癫痫。最近，两个GABA（A）受体δ亚基变异体（E177 A，R220 H）被认为是全身性癫痫伴热性惊厥和青少年肌阵挛性癫痫的易感等位基因。在人胚肾293 T细胞中，重组h α 1 β 2 δ（E177 A）和h α 1 β 2 δ（R220 H）受体电流降低，但电流降低的基础尚未确定。我们研究了使用h α 4 β 2 δ受体（一种生理上更相关的亚型，与癫痫发生有关）的这些变体产生的电流减少的机制基础，通过表征这些变体对受体细胞表面表达和单通道门控特性的影响。变体α 4 β 2 δ（R220H）受体的表达导致表面受体蛋白的减少，并且对于变体α 4 β 2 δ（E177A）受体观察到较小但显著的减少。对于两种变体，对于野生型和变体受体的混合群体，未观察到表面表达的显著改变。与野生型受体相比，α 4 β 2 δ（E177 A）和α 4 β 2 δ（R220 H）受体单通道电流的平均开放持续时间均显著降低。这些数据表明，δ（E177 A）和δ（R220 H）变体可能通过相似的细胞和分子机制导致IGE的去抑制，在异源性受影响的个体中，含δ亚基的GABA（A）受体通道开放持续时间的减少可能是导致IGE去抑制的主要原因。
Most human idiopathic generalized epilepsies (IGEs) are polygenic, but virtually nothing is known of the molecular basis for any of the complex epilepsies. Recently, two GABA(A) receptor delta subunit variants (E177A, R220H) were proposed as susceptibility alleles for generalized epilepsy with febrile seizures plus and juvenile myoclonic epilepsy. In human embryonic kidney 293T cells, recombinant h alpha 1 beta 2 delta(E177A) and h alpha 1 beta 2 delta(R220H) receptor currents were reduced, but the basis for the current reduction was not determined. We examined the mechanistic basis for the current reduction produced by these variants using the h alpha 4 beta 2 delta receptor, an isoform more physiologically relevant and linked to epileptogenesis, by characterizing the effects of these variants on receptor cell surface expression and single-channel gating properties. Expression of variant alpha 4 beta 2 delta(R220H) receptors resulted in a decrease in surface receptor proteins, and a smaller, but significant, reduction was observed for variant alpha 4 beta 2 delta(E177A) receptors. For both variants, no significant alterations of surface expression were observed for mixed population of wild-type and variant receptors. The mean open durations of alpha 4 beta 2 delta(E177A) and alpha 4 beta 2 delta(R220H) receptor single-channel currents were both significantly decreased compared to wild-type receptors. These data suggest that both delta(E177A) and delta(R220H) variants may result in disinhibition in IGEs by similar cellular and molecular mechanisms, and in heterozygously affected individuals, a reduction in channel open duration of delta subunit-containing GABA(A) receptors may be the major contributor to the