Further characterization of the binding of human recombinant interleukin 2 to heparin and identification of putative binding sites
Further characterization of the binding of human recombinant interleukin 2 to heparin and identification of putative binding sites
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DOI：
10.1093/glycob/8.5.509
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发表时间：
1998-05-01
期刊：
影响因子：
4.3
通讯作者：
Rider, CC
中科院分区：
文献类型：
--
作者：
Najjam, S;Mulloy, B;Rider, CC
我们以前提供了令人信服的证据表明，人重组白细胞介素2（IL-2）结合的硫酸多糖肝素，高度硫酸化硫酸乙酰肝素和岩藻依聚糖，在这里，我们表明，IL-2的结合是依赖于肝素链的长度，但小至15聚体的片段保留结合活性。外源性肝素的加入对IL-2的体外生物学活性无影响，且可溶性IL-2受体α和β多肽不与肝素竞争结合IL-2，肝素结合的IL-2仍能被两种IL-2特异性单克隆抗体3 H9和H2-8识别，其抗原表位位于氨基末端区域。鼠IL-2不像其人对应物不能结合肝素，在位置Lys 43、Thr 51和Gln 126处具有单个氨基酸取代的人IL-2类似物不再结合肝素。相比之下，Arg 38 Ala类似物保留肝素的全部肝素结合活性。这些实验结果与分子模拟研究一起表明，人IL-2上存在两个假定的肝素结合位点，一个涉及四个碱性残基，Lys 48，Lys 49，Lys 54和His 55，另一个是包含Lys 43，Lys 64，Arg 81和Arg 83的不连续位点。这两个簇在鼠IL-2中都不完全保守。总的来说，我们的数据表明，人IL-2与肝素和硫酸乙酰肝素的结合不干扰IL-2/IL-2受体相互作用。因此，与糖胺聚糖的结合可能是将细胞因子以活性形式保持在组织中靠近其分泌位点的机制，从而有利于IL-2的旁分泌作用。
We have previously provided compelling evidence that human recombinant interleukin 2 (IL-2) binds to the sulfated polysaccharides heparin, highly sulfated heparan sulfate and fucoidan, Here we show that IL-2 binding is dependent on heparin chain length, but with fragments as small as 15-mers retaining binding activity. The addition of exogenous heparin has no effect on the in vitro biological activity of IL-2, In addition soluble IL-2 receptor alpha and beta polypeptides do not compete with heparin for the binding of IL-2, IL-2 bound by heparin is still recognized by two IL-2 specific monoclonal antibodies, 3H9 and H2-8, whose epitopes lie in the amino terminal region. Murine IL-2 unlike its human counterpart fails to bind to heparin, Human IL-2 analogs with single amino acid substitutions at positions Lys43, Thr51, and Gln126 analogs no longer bind to heparin, By contrast the Arg38Ala analog retains heparin full heparin binding activity. These experimental findings together with molecular modeling studies suggest two putative heparin binding sites on human IL-2, one involving four basic residues, Lys48, Lys49, Lys54, and His55, and the other being a discontinuous site comprising Lys43, Lys64, Arg81, and Arg83, Neither of these two clusters is completely conserved in murine IL-2. Overall our data suggest that the binding of human IL-2 to heparin and heparan sulfate does not interfere with IL-2/IL-2 receptor interactions. Therefore, binding to glycosaminoglycan may be a mechanism for retaining the cytokine in an active form close to its site of secretion in the tissue, thus favoring a paracrine role for IL-2.