Subcellular distribution of beta 2-adrenergic receptors delineated with quantitative ultrastructural autoradiography of radioligand binding sites.
Subcellular distribution of beta 2-adrenergic receptors delineated with quantitative ultrastructural autoradiography of radioligand binding sites.
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通过放射性配体结合位点的定量超微结构放射自显影描绘出 β2-肾上腺素能受体的亚细胞分布。
DOI：
10.1161/01.res.70.6.1320
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发表时间：
1992
影响因子：
20.1
通讯作者：
Liggett,SB
中科院分区：
文献类型：
--
作者：
Saffitz,JE;Liggett,SB
β-肾上腺素能受体在心血管系统的信号转导中起关键作用。β-肾上腺素能受体表达的调节取决于多种因素，包括受体蛋白的合成和降解速率以及受体在细胞表面和推定的细胞内区室之间的运输。为了表征β-肾上腺素能受体的亚细胞分布，并描绘肾上腺素能受体在稳态下驻留的细胞内室的超微结构，我们研究了转染人β 2-肾上腺素能受体基因的中国仓鼠成纤维细胞。这些细胞的β 2-肾上腺素能受体与亲脂性光活化拮抗剂[125 I]iodocyanopindolol diazarine共价标记，特异性放射性配体结合位点定位在定量电子显微镜放射自显影分辨率的超微结构水平。β 2-肾上腺素能受体的密度在质膜中比在任何其他隔室中大约100倍。大约50%的总细胞受体被确定在细胞表面上的一个明显的随机，非聚集分布，并没有与网格蛋白包被的坑或其他细胞表面结构的专业化。其余的受体分布在细胞内的膜室，包括光滑囊泡，粗面内质网，高尔基体，细胞器可能参与受体的合成，降解，或贩运的阶段。在基础状态下，β 2-肾上腺素能受体与包被的细胞内囊泡没有关联，所述囊泡是用于内化其细胞外配体的选定细胞表面受体的内吞途径的典型。这些结果是第一个严格量化β-肾上腺素能受体的亚细胞分布，并明确建立了大量细胞内受体的存在。
beta-Adrenergic receptors play a critical role in signal transduction in the cardiovascular system. Regulation of beta-adrenergic receptor expression depends on multiple factors, including rates of synthesis and degradation of receptor protein and trafficking of receptors between the cell surface and putative intracellular compartments. To characterize the subcellular distribution of beta-adrenergic receptors and to delineate the ultrastructure of intracellular compartments in which adrenergic receptors reside in the steady state, we studied Chinese hamster fibroblast cells transfected with the human beta 2-adrenergic receptor gene. beta 2-Adrenergic receptors of these cells were covalently labeled with the lipophilic photoactivatable antagonist [125I]iodocyanopindolol diazarine, and specific radioligand binding sites were localized at the ultrastructural level of resolution with quantitative electron microscopic autoradiography. The density of beta 2-adrenergic receptors was approximately 100-fold greater in the plasmalemma than in any other compartment. Approximately 50% of total cellular receptors were identified on the cell surface in an apparently random, nonclustered distribution and without association with clathrin-coated pits or other cell surface structural specializations. The remaining receptors were distributed among intracellular membranous compartments, including smooth vesicles, rough endoplasmic reticulum, and the Golgi apparatus, organelles presumably involved in stages of receptor synthesis, degradation, or trafficking. In the basal state, there was no association of beta 2-adrenergic receptors with coated intracellular vesicles typical of the endocytotic pathway of selected cell surface receptors that function to internalize their extracellular ligands. These results are the first to rigorously quantify the subcellular distribution of beta-adrenergic receptors and unequivocally establish the presence of a substantial pool of intracellular receptors.