Residues in the first transmembrane domain of the Caenorhabditis elegans GABAA receptor confer sensitivity to the neurosteroid pregnenolone sulfate
Residues in the first transmembrane domain of the Caenorhabditis elegans GABAA receptor confer sensitivity to the neurosteroid pregnenolone sulfate
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DOI：
10.1038/sj.bjp.0706719
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发表时间：
2006-05-01
影响因子：
7.3
通讯作者：
Bamber, Bruce A.
中科院分区：
文献类型：
--
作者：
Wardell, Bryan;Marik, Purba S.;Bamber, Bruce A.
1 GABA(A)受体是内源性和合成神经类固醇的靶标。神经类固醇对GABA(A)受体的作用所需的残基知之甚少。我们研究了孕烯醇酮硫酸酯(PS)对秀丽线虫UNC-49 GABA受体的抑制作用，UNC-49是哺乳动物GABA(A)受体的同源物。UNC-49C对PS敏感，但UNC-49B不敏感。通过分析嵌合受体和含有定点突变的受体，我们确定了PS抑制所需的两个区域。3第一个跨膜区的四个残基是大多数PS敏感性所必需的，但M2螺旋末端的带电胞外残基也起作用。值得注意的是，多一个M1残基的突变逆转了PS从抑制物到受体功能增强剂的作用。4突变M1结构域对抑制物印防己毒素的敏感性几乎没有影响，这表明这些残基可能是特异性地介导神经类固醇作用，而不是一般的变构调节。
1 The GABA(A) receptor is a target of endogenous and synthetic neurosteroids. Little is known about the residues required for neurosteroid action on GABA(A) receptors. We have investigated pregnenolone sulfate (PS) inhibition of the Caenorhabditis elegans UNC-49 GABA receptor, a close homolog of the mammalian GABA(A) receptor.2 The UNC-49 locus encodes two GABA receptor subunits, UNC-49B and UNC-49C. UNC-49C is sensitive to PS but UNC-49B is not sensitive. By analyzing chimeric receptors and receptors containing site-directed mutations, we identified two regions required for PS inhibition.3 Four residues in the first transmembrane domain are required for the majority of the sensitivity to PS, but a charged extracellular residue at the end of the M2 helix also plays a role. Strikingly, mutation of one additional M1 residue reverses the effect of PS from an inhibitor to an enhancer of receptor function.4 Mutating the M1 domain had little effect on sensitivity to the inhibitor picrotoxin, suggesting that these residues may mediate neurosteroid action specifically, and not allosteric regulation in general.