Multiple roles for the first transmembrane domain of GABAA receptor subunits in neurosteroid modulation and spontaneous channel activity.
Multiple roles for the first transmembrane domain of GABAA receptor subunits in neurosteroid modulation and spontaneous channel activity.
复制标题
DOI：
10.1016/j.neulet.2010.02.058
复制
发表时间：
2010-04-12
影响因子：
2.5
通讯作者：
Bamber BA
中科院分区：
文献类型：
--
作者：
Baker C;Sturt BL;Bamber BA
神经类固醇通过变构调节突触和突触外 GABAA 受体发挥有效的生理作用。一些内源性神经类固醇，例如 3α, 21-二羟基-5β-pregnan-20-one (5α, 3α-THDOC)，通过与 α 亚基第一和第四跨膜 (TM) 结构域中的保守残基定义的结合袋相互作用，增强 GABAA 受体功能。其他药物，例如孕烯醇酮硫酸盐 (PS)，通过尚未确定的结合位点抑制 GABAA 受体功能。在这里，我们基于对 UNC-49 GABA 受体（一种来自秀丽隐杆线虫的 GABAA 样受体）的 PS 抑制的研究，研究了 PS 抑制哺乳动物 GABAA 受体的机制。在UNC-49中，TM1的19个残基片段可以发生突变，以在20倍的范围内增加或减少PS敏感性。令人惊讶的是，将这些 UNC-49 序列替换为哺乳动物 α1、β2 和 γ2 亚基并没有对所得嵌合受体的 PS 敏感性产生相应的影响。因此，该位点不太可能形成保守的 PS 结合袋。然而，我们观察到了一些有趣的意想不到的效果。首先，嵌合γ2亚基导致5α、3α-THDOC增强功效增加；其次，α6β2δ受体的自发门控被PS阻断，并被嵌合β2亚基减少；第三，嵌合β2亚基减少了5α,3α-THDOC对α6β2δ受体的直接激活。这些结果揭示了非α亚基在神经类固醇调节和直接激活中的新作用，并表明β亚基TM1结构域对于突触外GABAA受体的自发活动很重要。
Neurosteroids exert potent physiological effects by allosterically modulating synaptic and extrasynaptic GABAA receptors. Some endogenous neurosteroids, such as 3α, 21-dihydroxy-5β-pregnan-20-one (5α, 3α-THDOC), potentiate GABAA receptor function by interacting with a binding pocket defined by conserved residues in the first and fourth transmembrane (TM) domains of α subunits. Others, such as pregnenolone sulfate (PS), inhibit GABAA receptor function through as-yet unidentified binding sites. Here we investigate the mechanisms of PS inhibition of mammalian GABAA receptors, based on studies of PS inhibition of the UNC-49 GABA receptor, a GABAA-like receptor from Caenorhabditis elegans. In UNC-49, a 19 residue segment of TM1 can be mutated to increase or decrease PS sensitivity over a 20-fold range. Surprisingly, substituting these UNC-49 sequences into mammalian α1, β2, and γ2 subunits did not produce the corresponding effects on PS sensitivity of the resulting chimeric receptors. Therefore, it is unlikely that a conserved PS binding pocket is formed at this site. However we observed several interesting unexpected effects. First, chimeric γ2 subunits caused increased efficacy of 5α, 3α-THDOC potentiation; second, spontaneous gating of α6β2δ receptors was blocked by PS, and reduced by chimeric β2 subunits; and third, direct activation of α6β2δ receptors by 5α, 3α-THDOC was reduced by chimeric β2 subunits. These results reveal novel roles for non-α subunits in neurosteroid modulation and direct activation, and show that the β subunit TM1 domain is important for spontaneous activity of extrasynaptic GABAA receptors.
登录
查看更多内容
DOI：
10.1073/pnas.96.22.12905
发表时间：
1999-10-26
影响因子：
11.1
作者：
Mihalek, RM;Banerjee, PK;Homanics, GE
通讯作者：
Homanics, GE
影响因子：
7.3
作者：
Wardell, Bryan;Marik, Purba S.;Bamber, Bruce A.
通讯作者：
Bamber, Bruce A.
影响因子：
5.5
作者：
Akk, G;Bracamontes, J;Steinbach, JH
通讯作者：
Steinbach, JH
影响因子：
64.8
作者：
Brickley, SG;Revilla, V;Farrant, M
通讯作者：
Farrant, M
影响因子：
3.6
作者：
McCartney, Melissa R.;Deeb, Tarek Z.;Hales, Tim G.
通讯作者：
Hales, Tim G.