Aromatic Residues in the Fourth Transmembrane-Spanning Helix M4 Are Important for GABAρ Receptor Function
Aromatic Residues in the Fourth Transmembrane-Spanning Helix M4 Are Important for GABAρ Receptor Function
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DOI：
10.1021/acschemneuro.7b00315
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发表时间：
2018-02-01
影响因子：
5
通讯作者：
Lummis, Sarah C. R.
中科院分区：
文献类型：
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作者：
Cory-Wright, James;Alqazzaz, Mona;Lummis, Sarah C. R.
GABA受体是五聚体配体门控离子通道（plgic） GABA(a)受体家族的一个亚家族。5个亚基各有4个跨膜α -螺旋（M1-M4），其中M4离中心孔最远。M4螺旋上的芳香族残基对plics中的受体组装很重要，也可能与邻近的脂质和/或邻近α螺旋和细胞外结构域的残基相互作用，以修饰或启用通道门控。本研究在HEK293细胞中使用位点定向诱变和随后的表达来检测M4受体芳香残基在GABA受体跨膜结构域中的作用，并使用荧光膜电位敏感染料探测功能参数。这些数据表明，M4中的许多芳香残基在受体功能中发挥作用，与其他残基的取代可以消除和/或改变功能参数。模型显示，这些残基可能与邻近的M1和M3 α螺旋中的残基和/或胞外区域的cys环中的残基相互作用。我们认为，许多这些芳香相互作用促成了“芳香拉链”，这使得M4和其他受体之间的相互作用对功能至关重要。因此，这些数据支持了其他研究，表明M4不是被动地“保护”其他跨膜螺旋免受脂质双分子层的影响，而是积极参与蛋白质的功能。
GABA rho receptors are a subfamily of the GABA(A) receptor family of pentameric ligand-gated ion channels (pLGICs). Each of the five subunits has four transmembrane alpha-helices (M1-M4), with M4 most distant from the central pore. Aromatic residues in this M4 helix are important for receptor assembly in pLGICs and also may interact with adjacent lipids and/or residues in neighboring alpha-helices and the extracellular domain to modify or enable channel gating. This study examines the role of M4 receptor aromatic residues in the GABA rho receptor transmembrane domain using site-directed mutagenesis and subsequent expression in HEK293 cells, probing functional parameters using a fluorescent membrane-potential-sensitive dye. The data indicate that many of the aromatic residues in M4 play a role in receptor function, as substitution with other residues can ablate and/or modify functional parameters. Modeling showed that these residues likely interact with residues in the adjacent M1 and M3 alpha-helices and/or residues in the Cys-loop in the extracellular domain. We suggest that many of these aromatic interactions contribute to an "aromatic zipper", which allows interactions between M4 and the rest of the receptor that are essential for function. Thus, the data support other studies showing that M4 does not play a passive role in "protecting" the other transmembrane helices from the lipid bilayer but is actively involved in the function of the protein.