An electron microscope autoradiographic study of the carbohydrate recognition systems in rat liver. II. Intracellular fates of the 125I- ligands
An electron microscope autoradiographic study of the carbohydrate recognition systems in rat liver. II. Intracellular fates of the 125I- ligands
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大鼠肝脏碳水化合物识别系统的电子显微镜放射自显影研究。
DOI：
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发表时间：
1979
影响因子：
7.8
通讯作者：
Hans Stukenbrok
中科院分区：
文献类型：
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作者：
A. L. Hubbard;Hans Stukenbrok
电子显微镜放射自显影和生物化学方法被用来研究细胞内的命运的几个125 I-糖蛋白，已知被特异性结合和内化的不同类型的细胞在肝脏中。在检查的最早时间（1- 2分钟），125 I-糖蛋白（ASGP）主要定位于肝细胞的窦状前沿着。放射自显影颗粒分布的分析表明：（a）约40- 60%的125 I-配体可归因于质膜;（B）一个重要的部分已被内化;然而（c）在溶酶体-高尔基体区存在很少的125 I-配体。4和15分钟之间的125 I-ASGPs给药后，有一个显着的重新分配放射自显影颗粒从质膜和外周细胞质（减少30%）的溶酶体高尔基体区域（增加30%）。在较长的时间（30分钟），有持续的125 I-ASGP引流到这个区域。次级溶酶体上的颗粒密度比可识别的高尔基体上的颗粒密度高60- 90倍，这清楚地表明溶酶体是125 I-ASGP的最终目的地。然而，不超过60%的总125 I-配体可以定位于肝细胞的富含溶酶体的区域，其余40%主要在中间细胞质中。当在肝脏中发现[125 I]-单碘酪氨酸（即，在内皮细胞中观察到的甘露糖和N-乙酰葡糖胺封端的糖蛋白（分别为己糖氨基- orosomucoid和无半乳糖-orosomucoid）的时间再分布表明，125 I-配体在它们最终驻留在致密体中（15分钟）之前驻留在巨胞饮囊泡中（1- 15分钟）。同样的125 I-配体也定位于类似次级溶酶体在枯否细胞的结构。“这些细胞器”的溶酶体性质是从[125 I]单碘酪氨酸在肝脏中的出现暗示的。125 I-β-葡萄糖醛酸苷酶在两种细胞类型中遵循相同的细胞内途径，但不降解。
Electron microscope autoradiographic and biochemical methods were used to study the intracellular fates of several 125I-glycoproteins, known to be specifically bound and internalized by the different cell types in the liver. At the earliest times examined (1--2 min), 125I- glycoproteins (ASGP) were localized predominantly along the sinusoidal front of hepatocytes. Analysis of the distribution of autoradiographic grains indicated that: (a) approximately 40--60% of the 125I-ligand could be ascribed to the plasmalemma; (b) a significant fraction had already been internalized; yet (c) very little 125I-ligand was present in the lysosome-Golgi region. Between 4 and 15 min after administration of 125I-ASGPs, there was a dramatic redistribution of autoradiographic grains from regions of the plasmalemma and peripheral cytoplasm (30% decrease) to the lysosome-Golgi region (30% increase). At longer times (30 min), there was continued drainage of 125I-ASGP into this region. The grain density over secondary lysosomes was 60--90 times higher than that over recognizable Golgi elements, clearly indicating that lysosomes were the ultimate destination of the 125I-ASGP. However, no more than 60% of the total 125I-ligand could be localized to lysosome- rich regions of the hepatocyte, with the remaining 40% primarily in the intermediate cytoplasm. Biochemical evidence for proteolysis of the internalized 125I-ASGP (presumably within lysosomes) was obtained when [125I]-mono-iodotyrosine was found in the liver (i.e., hepatocytes) at times later than 15 min. The temporal redistribution observed for mannose and N-acetylglucosamine-terminated glycoproteins (ahexosamino- orosomucoid and agalacto-orosomucoid, respectively) in endothelial cells indicated that the 125I-ligands resided in macropinocytic vesicles (1--15 min) before their ultimate residence in dense bodies (15 min). The same 125I-ligands were also localized to structures resembling secondary lysosomes in Kupffer cells. The lysosomal nature of "these organelles" was implied from the appearance of [125I]mono- iodotyrosine in the liver at later times. 125I-beta-glucuronidase followed the same intracellular pathway in both cell types but was not degraded.