Identification of the growth hormone-releasing peptide binding site in CD36: a photoaffinity cross-linking study
Identification of the growth hormone-releasing peptide binding site in CD36: a photoaffinity cross-linking study
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DOI：
10.1042/bj20040036
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发表时间：
2004-09-01
影响因子：
4.1
通讯作者：
Ong, H
中科院分区：
文献类型：
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作者：
Demers, A;McNicoll, N;Ong, H
GHRP（生长激素释放肽）是一类小型合成肽，已知通过与 G 蛋白偶联受体（称为 GHS-R）结合来刺激 GH 释放。我们发现海沙瑞林（GHRP 的六肽成员）与另一种被称为 CD36 的蛋白质结合，CD36 是一种在多种组织中表达的清道夫受体，包括单核细胞/巨噬细胞和内皮微血管系统。 CD36 参与巨噬细胞对 oxLDL（氧化低密度脂蛋白）的内吞作用，并通过与内皮细胞结合来调节血小板反应蛋白-1 引发的血管生成。为了定义 CD36 上海沙瑞林的结合域，对 CD36 进行共价光标记，然后对光配体-受体复合物进行酶促和化学降解。对应于 CD36-(Asn(132)-Glu(177)) 序列的 8 kDa 光标记片段已被鉴定为海沙瑞林结合位点。用 CNBr 对该片段进行化学裂解导致游离配体的释放，表明 Met(169) 是受体结合口袋内配体的接触点。我们得出结论，CD36 上海沙瑞林的结合域与 oxLDL 的结合域重叠，对应于 CD36 的残基 Gln(155)-Lys(183)。因此，海沙瑞林可能会干扰巨噬细胞对 CD36 介导的修饰脂蛋白的摄取。这可能至少部分有助于 GHRP 在载脂蛋白 E 缺陷小鼠中的抗动脉粥样硬化作用。
The GHRPs (growth hormone-releasing peptides) are a class of small synthetic peptides known to stimulate GH release through binding of a G-protein-coupled receptor (designated GHS-R). We have found that hexarelin, a hexapeptide member of the GHRPs, binds to another protein identified as CD36, a scavenger receptor that is expressed in various tissues, including monocytes/macrophages and the endothelial microvasculature. CD36 is involved in the endocytosis of oxLDL (oxidized low-density lipoprotein) by macrophages, and in the modulation of angiogenesis elicited by thrombospondin-1 through binding to endothelial cells. To define the binding domain for hexarelin on CD36, covalent photolabelling of CD36 followed by enzymic and chemical degradation of the photoligand-receptor complex was performed. A 8 kDa photolabelled fragment corresponding to the CD36-(Asn(132)-Glu(177)) sequence has been identified as the hexarelin-binding site. Chemical cleavage of this fragment with CNBr resulted in the release of the free ligand, suggesting that Met(169) is the contact point for the ligand within the receptor binding pocket. We conclude that the binding domain for hexarelin on CD36 overlaps with that for oxLDL, which corresponds to residues Gln(155)-Lys(183) of CD36. Hence hexarelin might interfere with the CD36-mediated uptake of modified lipoproteins by macrophages. This may contribute, at least in part, to the anti-atherosclerotic effect of GHRPs in apolipoprotein E-deficient mice.