Functional expression of rat ABCG2 on the luminal side of brain capillaries and its enhancement by astrocyte-derived soluble factor(s)
Functional expression of rat ABCG2 on the luminal side of brain capillaries and its enhancement by astrocyte-derived soluble factor(s)
复制标题
DOI：
10.1111/j.1471-4159.2004.02537.x
复制
发表时间：
2004-08-01
影响因子：
4.7
通讯作者：
Terasaki, T
中科院分区：
文献类型：
--
作者：
Hori, S;Ohtsuki, S;Terasaki, T
本研究的目的是阐明ATP结合盒G2（ABCG 2）转运体在大鼠血脑屏障（BBB）的表达、转运特性及其调控。从大鼠脑毛细血管组分中克隆了ABCG 2的大鼠同源物（rABCG 2）。在rABCG 2转染的HEK 293细胞中，rABCG 2被检测为通过二硫键桥接的糖蛋白复合物，可能是同源二聚体。该蛋白转运米托蒽醌和BODIPY-哌唑嗪。在大鼠脑毛细血管组分中，rABCG 2蛋白也被检测为糖基化和二硫键连接的复合物。免疫组织化学分析显示，rABCG 2主要定位于大鼠脑毛细血管的管腔侧，表明rABCG 2参与脑-血外排转运。对于调节研究，使用条件永生化的大鼠脑毛细血管内皮细胞（TR-BBB 13）、星形胶质细胞（TR-AST 4）和周细胞（TR-PCT 1）细胞系作为体外BBB模型。用TR-AST 4细胞的条件培养基处理TR-BBB 13细胞后，Ko 143（ABCG 2特异性抑制剂）敏感的转运活性和rABCG 2 mRNA水平显著增加，而TR-PCT 1细胞的条件培养基没有影响。这些结果表明，大鼠脑毛细血管表达功能性rABCG 2蛋白，并且该蛋白的转运活性被星形胶质细胞衍生的可溶性因子上调，同时伴随着rABCG 2 mRNA的诱导。
The purpose of the present study was to clarify the expression, transport properties and regulation of ATP-binding cassette G2 (ABCG2) transporter at the rat blood-brain barrier (BBB). The rat homologue of ABCG2 (rABCG2) was cloned from rat brain capillary fraction. In rABCG2-transfected HEK293 cells, rABCG2 was detected as a glycoprotein complex bridged by disulfide bonds, possibly a homodimer. The protein transported mitoxantrone and BODIPY-prazosin. In rat brain capillary fraction, rABCG2 protein was also detected as a glycosylated and disulfide-linked complex. Immunohistochemical analysis revealed that rABCG2 was localized mainly on the luminal side of rat brain capillaries, suggesting that rABCG2 is involved in brain-to-blood efflux transport. For the regulation study, conditionally immortalized rat brain capillary endothelial (TR-BBB13), astrocyte (TR-AST4) and pericyte (TR-PCT1) cell lines were used as an in vitro BBB model. Following treatment of TR-BBB13 cells with conditioned medium of TR-AST4 cells, the Ko143 (an ABCG2-specific inhibitor)-sensitive transport activity and rABCG2 mRNA level were significantly increased, whereas conditioned medium of TR-PCT1 cells had no effect. These results suggest that rat brain capillaries express functional rABCG2 protein and that the transport activity of the protein is up-regulated by astrocyte-derived soluble factor(s) concomitantly with the induction of rABCG2 mRNA.