A neurosteroid potentiation site can be moved among GABAA receptor subunits
A neurosteroid potentiation site can be moved among GABAA receptor subunits
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DOI：
10.1113/jphysiol.2012.237255
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发表时间：
2012-11-01
影响因子：
5.5
通讯作者：
Steinbach, Joe Henry
中科院分区：
文献类型：
--
作者：
Bracamontes, John R.;Li, Ping;Steinbach, Joe Henry
内源性神经类固醇是GABAA受体活化的最有效和最有效的增强剂之一。已经提出，在α亚基的第一跨膜区（TM1区）中的保守的谷氨酰胺残基是增强神经类固醇的结合所需的。该残基的突变可以降低或消除类固醇增强功能的能力。然而，尚不清楚增强作用是否需要类固醇与α亚基相互作用。为了研究这个问题，我们突变了β 2中的同源残基，2L亚基的谷氨酰胺，并发现这些突变不能赋予增强的别孕烯醇酮（3a5aP）时，表达在受体含有无效的α 1亚基。然而，增强恢复时，整个TM1区从a1亚基转移到β 2或？2L亚基。当在α 1亚基中产生时，影响增强作用的TM1区域中的突变在转移的TM1区域中产生时具有类似的作用。此外，3a5aP对单通道动力学的影响对于野生型受体和具有移动的TM1区域的受体是相似的。这些结果支持类固醇结合在受体的跨膜区域的想法。观察结果与以前的工作是一致的，表明神经甾体增效作用是由影响受体作为一个整体，而不是一个单独的亚基或对亚基的行动介导的，此外还表明，该机制是独立的亚基与类固醇相互作用的性质。
Endogenous neurosteroids are among the most potent and efficacious potentiators of activation of GABAA receptors. It has been proposed that a conserved glutamine residue in the first membrane-spanning region (TM1 region) of the a subunits is required for binding of potentiating neurosteroids. Mutations of this residue can reduce or remove the ability of steroids to potentiate function. However, it is not known whether potentiation requires that a steroid interact with the a subunit, or not. To examine this question we mutated the homologous residue in the beta 2 and ?2L subunits to glutamine, and found that these mutations could not confer potentiation by allopregnanolone (3a5aP) when expressed in receptors containing ineffective a1 subunits. However, potentiation is restored when the entire TM1 region from the a1 subunit is transferred to the beta 2 or ?2L subunit. Mutations in the TM1 region that affect potentiation when made in the a1 subunit have similar effects when made in transferred TM1 region. Further, the effects of 3a5aP on single-channel kinetics are similar for wild-type receptors and receptors with moved TM1 regions. These results support the idea that steroids bind in the transmembrane regions of the receptor. The observations are consistent with previous work indicating that neurosteroid potentiation is mediated by an action that affects the receptor as a whole, rather than an individual subunit or pair of subunits, and in addition demonstrate that the mechanism is independent of the nature of the subunit that interacts with steroid.