Kounnas M Z, Haudenschild C C, Strickland D K, Argraves W S
Biochemistry Department, J. H. Holland Laboratory, American Red Cross, Rockville, MD 20855.
In Vivo. 1994 May-Jun;8(3):343-51.
In this study we have immunologically examined the expression of the structurally and functionally related receptors, LRP and gp330, and their associated 39 kDa protein (RAP) in tissues of the embryonic mouse. One aim was to determine whether these proteins were coordinantly expressed. The data reveals that gp330 is expressed on the apical surfaces of many specialized absorptive epithelia most prominently, choroid plexus, ependyma, metanephric tubules, ear, thyroid, pericardium, and intestine. LRP was detected in all epithelia expressing gp330 with the exception of the epicardium and metanephric tubule epithelium. However, the subcellular pattern of LRP deposition in polarized epithelium was distinct from the apical pattern of gp330, perhaps indicating that LRP was either sequestered intracellularly or distributed basolaterally. The pattern of LRP expression in tissues of the mouse embryo was however much wider than that of gp330. Prominent expression of LRP was observed in skin, myocardium, mesenchyme, liver, pancreas, and marginal regions of the brain. In the developing liver, LRP was not detected in day 10.5 but was detected in megacaryocyte-like cells of 12.5 day and in hepatocytes of 14.5 day embryonic liver. RAP was observed to be coexpressed with either or both of the receptors but its subcellular pattern of distribution coincided with that of LRP. The coexpression of gp330 and LRP in epithelial cells and the observation that gp330 staining was always localized apically while LRP was distributed basolaterally or sequestered intracellularly suggests that these receptors have distinct functions in polarized epithelial cells.
在本研究中，我们通过免疫学方法检测了结构和功能相关的受体——低密度脂蛋白受体相关蛋白（LRP）和 gp330，以及它们相关的 39 kDa 蛋白（RAP）在胚胎小鼠组织中的表达情况。目的之一是确定这些蛋白是否协同表达。数据显示，gp330 最显著地表达于许多特化的吸收性上皮细胞的顶端表面，如脉络丛、室管膜、后肾管、耳、甲状腺、心包和肠道。除心外膜和后肾管上皮外，在所有表达 gp330 的上皮细胞中均检测到 LRP。然而，LRP 在极化上皮细胞中的亚细胞沉积模式与 gp330 的顶端模式不同，这可能表明 LRP 要么被隔离在细胞内，要么分布在基底外侧。然而，小鼠胚胎组织中 LRP 的表达模式比 gp330 要广泛得多。在皮肤、心肌、间充质、肝脏、胰腺和脑边缘区域观察到 LRP 的显著表达。在发育中的肝脏中，第 10.5 天时未检测到 LRP，但在第 12.5 天的巨核细胞样细胞和第 14.5 天胚胎肝脏的肝细胞中检测到了 LRP。观察到 RAP 与其中一种或两种受体共表达，但其亚细胞分布模式与 LRP 一致。gp330 和 LRP 在上皮细胞中的共表达，以及 gp330 染色总是定位于顶端而 LRP 分布在基底外侧或被隔离在细胞内的观察结果表明，这些受体在极化上皮细胞中具有不同的功能。
