The chemokine receptor CCR2 mediates the binding and internalization of monocyte chemoattractant protein-1 along brain microvessels
The chemokine receptor CCR2 mediates the binding and internalization of monocyte chemoattractant protein-1 along brain microvessels
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DOI：
10.1523/jneurosci.21-23-09214.2001
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发表时间：
2001-12-01
影响因子：
5.3
通讯作者：
Pachter, JS
中科院分区：
文献类型：
--
作者：
Dzenko, KA;Andjelkovic, AV;Pachter, JS
来自该实验室的先前结果揭示了单核细胞趋化蛋白-1（MCP-1）沿着人脑微血管的高亲和力饱和结合位点的存在（Andjelkovic等，1999年第一季度; Andjelkovic和Pachter，2000），这表明CC趋化因子受体2（CCR 2）（该趋化因子的识别受体）由脑微血管内皮表达。为了测试CCR 2在介导MCP-1与脑微血管系统相互作用中的直接作用，我们评估了从野生型小鼠和从工程化以缺乏该受体的CCR 2（-/-）小鼠分离的小鼠脑微血管中的MCP-1结合活性。结果表明，与野生型对照相比，在从CCR 2（-/-）小鼠制备的微血管中MCP-1结合大大减弱。此外，来自野生型小鼠的微血管表现出MCP-1诱导的MCP-1结合下调和结合活性的恢复，这不依赖于从头蛋白质合成。此外，MCP-1被显示在野生型微血管内内化，但不在从CCR 2（-/-）小鼠获得的微血管内内化，另外证明了CCR 2对于MCP-1内吞是必须的。最后，观察到MCP-1的内化而不是转铁蛋白被小窝的破坏抑制。内化的MCP-1也与小窝蛋白-1（小窝的主要蛋白）共定位在某些位点，这意味着该趋化因子部分地通过非网格蛋白包被的囊泡被内吞。这些结果促使人们考虑MCP-1信号可能通过这种趋化因子与其同源受体CCR 2沿沿着脑微血管内皮细胞的高度特异性相互作用而跨越血脑屏障传递。
Previous results from this laboratory revealed the presence of high-affinity saturable binding sites for monocyte chemoattractant protein-1 (MCP-1) along human brain microvessels (Andjelkovic et al., 1999; Andjelkovic and Pachter, 2000), which suggested that CC chemokine receptor 2 (CCR2), the recognized receptor for this chemokine, was expressed by the brain microvascular endothelium. To test the role of CCR2 directly in mediating MCP-1 interactions with the brain microvasculature, we assessed MCP-1 binding activity in murine brain microvessels isolated from wild-type mice and from CCR2 (-/-) mice engineered to lack this receptor. Results demonstrate that MCP-1 binding is greatly attenuated in microvessels prepared from CCR2 (-/-) mice compared with wild-type controls. Moreover, microvessels from wild-type mice exhibited MCP-1-induced downmodulation in MCP-1 binding and a recovery of binding activity that was not dependent on de novo protein synthesis. Furthermore, MCP-1 was shown to be internalized within wild-type microvessels, but not within microvessels obtained from CCR2 (-/-) mice, additionally demonstrating that CCR2 is obligatory for MCP-1 endocytosis. Last, internalization of MCP-1, but not transferrin, was observed to be inhibited by disruption of caveolae. Internalized MCP-1 also colocalized at some sites with caveolin-1, a major protein of caveolae, implying that this chemokine is endocytosed, in part, via nonclathrin-coated vesicles. These results prompt consideration that MCP-1 signals may be relayed across the blood-brain barrier by highly specialized interactions of this chemokine with its cognate receptor, CCR2, along brain microvascular endothelial cells.