Function of Partially Duplicated Human α7 Nicotinic Receptor Subunit CHRFAM7A Gene POTENTIAL IMPLICATIONS FOR THE CHOLINERGIC ANTI-INFLAMMATORY RESPONSE
Function of Partially Duplicated Human α7 Nicotinic Receptor Subunit CHRFAM7A Gene POTENTIAL IMPLICATIONS FOR THE CHOLINERGIC ANTI-INFLAMMATORY RESPONSE
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DOI：
10.1074/jbc.m110.180067
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发表时间：
2011-01-07
影响因子：
4.8
通讯作者：
Montiel, Carmen
中科院分区：
文献类型：
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作者：
de Lucas-Cerrillo, Ana M.;Constanza Maldifassi, M.;Montiel, Carmen
神经元α 7烟碱受体亚基基因（CHRNA 7）在人类基因组中部分重复，与新的FAM 7A基因形成杂合基因（CHRFAM 7A）。已在脑、免疫细胞和HL-60细胞系中鉴定了杂交基因转录本dup alpha 7，尽管其翻译和功能仍不清楚。本研究克隆了dup alpha 7 cDNA，并在GH4 C1细胞和非洲爪蟾卵母细胞中表达，以研究表达蛋白的模式和功能作用。我们的结果表明，dup α 7转录本在HL-60细胞中天然翻译，并在GH4 C1细胞和卵母细胞中异源表达。将dup α 7 mRNA注射到卵母细胞中不能产生功能性受体，但是当以α 7/dup α 7的比例为5：1、2：1、1：1、1：5和1：10共同注射α 7 mRNA时，它分别使对照卵母细胞（仅α 7）中产生的尼古丁诱导的α 7电流减少26、53、75、93和94%。这种效应主要是由于到达卵母细胞膜的功能性α 7受体的数量减少，如从α-银环蛇毒素结合和荧光共聚焦测定推断的。另外两个发现开启了这样一种可能性，即在体外观察到的dup alpha 7对alpha 7受体活性的显性负效应可以外推到体内情况。(i)与α 7 mRNA相比，基础dup α 7 mRNA水平在人类大脑皮层中是实质性的，并且在巨噬细胞中更高。(ii)巨噬细胞中的dup α 7 mRNA水平被IL-1 β、LPS和尼古丁下调。因此，dup α 7可以调节α 7受体介导的突触传递和胆碱能抗炎反应。
The neuronal alpha 7 nicotinic receptor subunit gene (CHRNA7) is partially duplicated in the human genome forming a hybrid gene (CHRFAM7A) with the novel FAM7A gene. The hybrid gene transcript, dup alpha 7, has been identified in brain, immune cells, and the HL-60 cell line, although its translation and function are still unknown. In this study, dup alpha 7 cDNA has been cloned and expressed in GH4C1 cells and Xenopus oocytes to study the pattern and functional role of the expressed protein. Our results reveal that dup alpha 7 transcript was natively translated in HL-60 cells and heterologously expressed in GH4C1 cells and oocytes. Injection of dup alpha 7 mRNA into oocytes failed to generate functional receptors, but when co-injected with alpha 7 mRNA at alpha 7/dup alpha 7 ratios of 5:1, 2:1, 1:1, 1:5, and 1: 10, it reduced the nicotine-elicited alpha 7 current generated in control oocytes (alpha 7 alone) by 26, 53, 75, 93, and 94%, respectively. This effect is mainly due to a reduction in the number of functional alpha 7 receptors reaching the oocyte membrane, as deduced from alpha-bungarotoxin binding and fluorescent confocal assays. Two additional findings open the possibility that the dominant negative effect of dup alpha 7 on alpha 7 receptor activity observed in vitro could be extrapolated to in vivo situations. (i) Compared with alpha 7 mRNA, basal dup alpha 7 mRNA levels are substantial in human cerebral cortex and higher in macrophages. (ii) dup alpha 7 mRNA levels in macrophages are down-regulated by IL-1 beta, LPS, and nicotine. Thus, dup alpha 7 could modulate alpha 7 receptor-mediated synaptic transmission and cholinergic anti-inflammatory response.