Mutations of the GABA-A receptor α1 subunit M1 domain reveal unexpected complexity for modulation by neuroactive steroids
Mutations of the GABA-A receptor α1 subunit M1 domain reveal unexpected complexity for modulation by neuroactive steroids
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DOI：
10.1124/mol.108.048520
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发表时间：
2008-09-01
影响因子：
3.6
通讯作者：
Steinbach, Joe Henry
中科院分区：
文献类型：
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作者：
Akk, Gustav;Li, Ping;Steinbach, Joe Henry
神经活性类固醇是哺乳动物 GABA-A 受体最有效的调节剂之一。先前的工作提出，受体增强是由类固醇与 M4 跨膜结构域中的残基 α 1Asn407/Tyr410 和 M1 结构域中的残基 α 1Gln241 定义的位点相互作用介导的。我们研究了 M1 亚基 M1 结构域中的残基在神经活性类固醇调节大鼠 α 1 beta 2 gamma 2L GABA-A 受体中的作用。数据表明该区域对于增强神经活性类固醇的作用至关重要。含有α1Q241W或α1Q241L突变的受体对(3α,5α)-3-羟基孕-20-一(3α5αP)不敏感，尽管潜在机制不同。 α 1Q241S 突变体被 3 α 5 α P 增强，但增强的动力学模式因突变而改变。值得注意的是，α 1Q241L 突变对 (3 α,5 α)-3-羟甲基孕-20-one 的通道增强没有影响，但邻近残基 α 1Ser240 的突变阻止了通道调制。 C3 上缺乏氢键基团的类固醇 (5 alpha-pregnan-20-one) 增强了野生型受体，但对 alpha 1Q241L 突变体没有增强作用。这些发现与α1Ser240和α1Gln241残基塑造类固醇分子结合表面的模型一致。
Neuroactive steroids are among the most efficacious modulators of the mammalian GABA-A receptor. Previous work has proposed that receptor potentiation is mediated by steroid interactions with a site defined by the residues alpha 1Asn407/Tyr410 in the M4 transmembrane domain and residue alpha 1Gln241 in the M1 domain. We examined the role of residues in the M1 subunit M1 domain in the modulation of the rat alpha 1 beta 2 gamma 2L GABA-A receptor by neuroactive steroids. The data demonstrate that the region is critical to the actions of potentiating neuroactive steroids. Receptors containing the alpha 1Q241W or alpha 1Q241L mutations were insensitive to (3 alpha,5 alpha)-3-hydroxypregnan-20-one (3 alpha 5 alpha P), albeit with different underlying mechanisms. The alpha 1Q241S mutant was potentiated by 3 alpha 5 alpha P, but the kinetic mode of potentiation was altered by the mutation. It is noteworthy that the alpha 1Q241L mutation had no effect on channel potentiation by (3 alpha,5 alpha)-3-hydroxymethylpregnan-20-one, but mutation of the neighboring residue, alpha 1Ser240, prevented channel modulation. A steroid lacking an H-bonding group on C3 (5 alpha-pregnan-20-one) potentiated the wild-type receptor but not the alpha 1Q241L mutant. The findings are consistent with a model in which the alpha 1Ser240 and alpha 1Gln241 residues shape the surface to which steroid molecules bind.