α-conotoxins ImI and ImII target distinct regions of the human α7 nicotinic acetylcholine receptor and distinguish human nicotinic receptor subtypes
α-conotoxins ImI and ImII target distinct regions of the human α7 nicotinic acetylcholine receptor and distinguish human nicotinic receptor subtypes
复制标题
DOI：
10.1021/bi048918g
复制
发表时间：
2004-12-28
期刊：
影响因子：
2.9
通讯作者：
Olivera, BM
中科院分区：
文献类型：
--
作者：
Ellison, M;Gao, F;Olivera, BM
Conus肽α -conotoxin ImI （α -ImI）和ImII （α -ImII）在其初级序列的11个残基中只有3个不同，但它们通过靶向不同的位点抑制人类α - 7烟碱乙酰胆碱受体（nAChR）。α 7 nAChR经典配体结合位点两侧的突变强烈影响α - imi的拮抗作用，但对α - imii不起作用。突变对α - imi结合和功能拮抗的影响可以通过α - imi的核磁共振结构与α - 7 nAChR配体结合域的同源模型的计算对接来解释。α - imii的独特结合位点通过其对嵌合受体的减弱拮抗作用进一步证明，在嵌合受体中，α - 7 nAChR的跨膜结构域和干预连接体被5 -羟色胺3型受体的相应序列所取代（5HT(3)）。这两种毒素还能区分人类烟碱受体的不同亚型；α - imii最能阻断人α 7和α 1beta1deltaepsilon受体亚型，而α - imi最能阻断人α 3beta2亚型。总的来说，这些数据表明，虽然α - imi以亚型选择性的方式靶向经典的竞争性配体结合位点，但α - imii是同质α 7 nAChRs中一个新的抑制位点的探针。
The Conus peptides alpha-conotoxin ImI (alpha-ImI) and ImII (alpha-ImII differ by only three of 11 residues in their primary sequences and yet are shown to inhibit the human alpha7 nicotinic acetylcholine receptor (nAChR) by targeting different sites. Mutations at both faces of the classical ligand binding site of the alpha7 nAChR strongly affect antagonism by alpha-ImI but not alpha-ImII. The effects of the mutations on alpha-ImI binding and functional antagonism are explained by computational docking of the NMR structure of alpha-ImI to a homology model of the ligand binding domain of the alpha7 nAChR. A distinct binding site for alpha-ImII is further demonstrated by its weakened antagonism for a chimeric receptor in which the membrane-spanning domains and intervening linkers of the alpha7 nAChR are replaced with the corresponding sequence from the serotonin type-3 receptor (5HT(3)). The two toxins also discriminate between different subtypes of human nicotinic receptors; alpha-ImII most strongly blocks the human alpha7 and alpha1beta1deltaepsilon receptor subtypes, while alpha-ImI most potently blocks the human alpha3beta2 subtype. Collectively, the data show that while alpha-ImI targets the classical competitive ligand binding site in a subtype selective manner, alpha-ImII is a probe of a novel inhibitory site in homomeric alpha7 nAChRs.