Endogenously Expressed Muscarinic Receptors in HEK293 Cells Augment Up-regulation of Stably Expressed α4β2 Nicotinic Receptors
Endogenously Expressed Muscarinic Receptors in HEK293 Cells Augment Up-regulation of Stably Expressed α4β2 Nicotinic Receptors
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DOI：
10.1074/jbc.m111.289546
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发表时间：
2011-11-18
影响因子：
4.8
通讯作者：
Kellar, Kenneth J.
中科院分区：
文献类型：
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作者：
Hussmann, Gregory P.;Yasuda, Robert P.;Kellar, Kenneth J.
尼古丁诱导的神经元烟碱受体（nAChR）上调已被发现和研究超过25年。其他nAChR配体也可以上调nAChR，但尚不清楚这些配体是否通过类似于尼古丁的机制诱导上调。在这项研究中，我们比较了上调由三种不同的烟碱激动剂和竞争性拮抗剂的几种不同的nAChR亚型在HEK293细胞中表达。尼古丁显著增加α 4 β 2 nAChR结合位点密度和β 2亚单位蛋白。卡巴胆碱，一种已知的nAChR和毒蕈碱受体激动剂，上调α 4 β 2 nAChR结合位点和亚基蛋白2倍以上的尼古丁。这种增加的上调被证明与内源性表达的毒蕈碱受体有关，并且这些毒蕈碱受体的刺激也与α 4和β 2 mRNA的2倍增加相关。这些细胞中的毒蕈碱受体活化似乎仅最低限度地影响CMV启动子活性（类似于1.2倍），这表明α 4和β 2 nAChR mRNA的增加可能不依赖于增强的转录。相反，其他机制可能有助于mRNA的增加，从而增加受体亚基和结合位点密度。这些研究证明了通过nAChR受体本身以外的机制和靶点在细胞模型中增加nAChR表达的可能性。
Nicotine-induced up-regulation of neuronal nicotinic receptors (nAChRs) has been known and studied for more than 25 years. Other nAChR ligands can also up-regulate nAChRs, but it is not known if these ligands induce up-regulation by mechanisms similar to that of nicotine. In this study, we compared up-regulation by three different nicotinic agonists and a competitive antagonist of several different nAChR subtypes expressed in HEK293 cells. Nicotine markedly increased alpha 4 beta 2 nAChR binding site density and beta 2 subunit protein. Carbachol, a known nAChR and muscarinic receptor agonist, up-regulated both alpha 4 beta 2 nAChR binding sites and subunit protein 2-fold more than did nicotine. This increased up-regulation was shown pharmacologically to involve endogenously expressed muscarinic receptors, and stimulation of these muscarinic receptors also correlated with a 2-fold increase in alpha 4 and beta 2 mRNA. Muscarinic receptor activation in these cells appears to affect CMV promoter activity only minimally (similar to 1.2 fold), suggesting that the increase in alpha 4 and beta 2 nAChR mRNA may not be dependent on enhanced transcription. Instead, other mechanisms may contribute to the increase in mRNA and a consequent increase in receptor subunits and binding site density. These studies demonstrate the possibility of augmentingn ChR expression in a cell model through mechanisms and targets other than the nAChR receptor itself.