HUMAN BLOOD-BRAIN-BARRIER INSULIN-LIKE GROWTH-FACTOR RECEPTOR
HUMAN BLOOD-BRAIN-BARRIER INSULIN-LIKE GROWTH-FACTOR RECEPTOR
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DOI：
10.1016/s0026-0495(98)90007-5
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发表时间：
1988-02-01
影响因子：
9.8
通讯作者：
ROSENFELD, RG
中科院分区：
文献类型：
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作者：
DUFFY, KR;PARDRIDGE, WM;ROSENFELD, RG
胰岛素样生长因子（IGF）-1和IGF-2可能是中枢神经系统重要的调节分子。脑中IGF的可能来源包括从头合成或循环IGF通过脑毛细血管内皮壁（即血脑屏障（BBB））的受体介导的转胞吞机制从血液转运到脑中。在本研究中，使用分离的人脑毛细血管作为人BBB的体外模型系统，并评估IGF-1或IGF-2与该制剂结合的特征。IGF-2在37 ° C下的总结合。C超过130%每毫克蛋白质，是三倍以上的IGF-1的总结合。在37度。C不饱和结合等于总结合，表明在生理温度下内吞作用是限速的。在4 ℃进行的结合研究比膜结合更大程度地减缓了内吞作用，并且可检测到IGF-1或IGF-2的特异性结合。任一肽的Scatchard图是线性的，IGF-1和IGF-2结合的摩尔解离常数为2.1 ± 0.1。0.4和1.1 .+-。0.1 nmol/L。超生理浓度的猪胰岛素抑制IGF-1（ED 50 = 2 μ g/mL）和IGF-2（ED 50 = 0.5 μ g/mL）的结合。使用二琥珀酰亚胺辛二酸酯（DSS）进行125 I-IGF-1、125 I-IGF-2和125 I-胰岛素与分离的人脑毛细血管的亲和交联。这些研究揭示了IGF-1和IGF-2的141 kd结合位点，以及胰岛素的133 kd结合位点。未检测到IGF-2的高分子量结合位点。总之，这些研究表明，1型IGF受体存在于分离的人脑毛细血管上，结合两种IGF，对IGF-2的亲和力略高。该受体对IGF-2的活性是IFG-1的三倍，与人脑和CSF中IGF-2的浓度（相对于IGF-1）高得多相平行。这些结果与人BBB IGF受体是循环肽，特别是IGF-2的转运系统的假设一致。
Insulin-like growth factor (IGF)-1 and IGF-2, may be important regulatory molecules in the CNS. Possible origins of IGFs in brain include either de novo synthesis or transport of circulating IGFs from blood into brain via receptor mediated transcytosis mechanisms at the brain capillary endothelial wall, ie, the blood-brain barrier (BBB). In the present studies, isolated human brain capillaries are used as an in vitro model system of the human BBB and the characteristics of IGF-1 or IGF-2 binding to this preparation were assessed. The total binding of IGF-2 at 37.degree. C exceeded 130% per mg protein and was threefold greater than the total binding of IGF-1. However, at 37.degree. C nonsaturable binding equaled total binding, suggesting that endocytosis is rate limiting at physiologic temperatures. Binding studies performed at 4.degree.C slowed endocytosis to a greater extent than membrane binding, and specific binding of either IGF-1 or IGF-2 was detectable. Scatchard plots for either peptide were linear and the molar dissociation constant of IGF-1 and IGF-2 binding was 2.1 .+-. 0.4 and 1.1 .+-. 0.1 nmol/L, respectively. Superphysiologic concentrations of porcine insulin inhibited the binding of both IGF-1 (ED50 = 2 .mu.g/mL) and IGF-2 (ED50 = 0.5 .mu.g/mL). Affinity cross linking of 125I-IGF-1, 125I-IGF-2, and 125I-insulin to isolated human brain capillaries was performed using dissucinimidylsuberate (DSS). These studies revealed a 141 kd binding site for both IGF-1 and IGF-2, and a 133 kd binding site for insulin. No high molecular weight binding site for IGF-2 was detected. In conclusion, these studies suggest that a type 1 IGF receptor is present on isolated human brain capillaries that binds both IGFs, with a slightly higher affinity for IGF-2. The threefold greater activity of this receptor for IGF-2 relative to IFG-1 parallels the much higher concentration of IGF-2 in human brain and CSF (relative to IGF-1). These results are consistent with the hypothesis that the human BBB IGF receptor is a transport system for the circulating peptides, particularly for IGF-2.