Cell fractionation and electron microscope studies of kidney folate-binding protein.
Cell fractionation and electron microscope studies of kidney folate-binding protein.
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肾叶酸结合蛋白的细胞分级和电子显微镜研究。
DOI：
10.1152/ajpcell.1991.260.2.c338
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Selhub,J
中科院分区：
文献类型：
--
作者：
Hjelle,JT;Christensen,EI;Carone,FA;Selhub,J
用细胞分级分离和不同电镜技术观察了近曲小管中叶酸结合蛋白（FBP）和[~ 3 H]叶酸的亚细胞分布。兔近端小管的细胞分级显示，FBP分布成两种模式：50%的FBP分布与丙氨酰氨基肽酶活性（刷状缘），其余的FBP分布与细胞器的密度较低，没有表现出大毛地黄皂苷诱导的位移到更大的密度。将[3 H]叶酸输注到肾脏中，然后分离和分离近端小管，显示[3 H]叶酸从重（刷状缘）模式向较轻细胞器模式的时间依赖性转变。电镜免疫细胞化学显示，大鼠肾脏近曲小管细胞的刷状缘、内吞内陷、内吞空泡和致密的顶小管内均可见FBP。大鼠肾脏EM放射自显影10分钟后静脉输注的[3 H]叶酸显示，标记显着集中在刷状缘，内吞囊泡，和溶酶体。这些数据支持了在肾脏中FBP介导的叶酸转运过程中受体介导的内吞作用的机制。
The subcellular distribution of folate-binding protein (FBP) and [3H]folate in the proximal tubule was examined using cell fractionation and different electron microscope (EM) techniques. Cell fractionation of rabbit proximal tubules revealed that FBP distributed into two modes: 50% of FBP distributed with alanylaminopeptidase activity (brush border), and the remaining FBP distributed with organelles of lower density that did not show a large digitonin-induced shift to greater density. Infusion of [3H]folate into the kidney followed by isolation and fractionation of the proximal tubules revealed a time-dependent shift of [3H]folate from the heavy (brush border) mode to the lighter organelle mode. By EM immunocytochemistry, rat kidney FBP locates in the brush border, endocytic invaginations, endocytic vacuoles, and dense apical tubules of proximal tubule cells. EM autoradiography of rat kidney 10 min after intravenous infusion of [3H]folate revealed that the label was significantly concentrated only in the brush border, endocytic vesicles, and lysosomes. These data support a mechanism of receptor-mediated endocytosis for the process of FBP-mediated folate transport in the kidney.