Graham G J, Wilkinson P C, Nibbs R J, Lowe S, Kolset S O, Parker A, Freshney M G, Tsang M L, Pragnell I B
The Beatson Institute for Cancer Research, CRC Beatson Laboratories, Glasgow, UK.
EMBO J. 1996 Dec 2;15(23):6506-15.
We have studied the role of proteoglycans in the function of Macrophage Inflammatory Protein-1 alpha (MIP-1alpha), a member of the proteoglycan binding chemokine family. Sequence and peptide analysis has identified a basic region within MIP-1alpha which appears to be the major determinant of proteoglycan binding and we have now produced a mutant of MIP-1alpha lacking the basic charges on two of the amino acids within this proteoglycan binding site. This mutant (Hep Mut) appears to have lost the ability to bind to proteoglycans. Bioassay of Hep Mut indicates that it has retained stem cell inhibitory properties but has a compromised activity as a monocyte chemoattractant, thus suggesting uncoupling of these two properties of MIP-1alpha. Receptor studies have indicated that the inactivity of Hep Mut on human monocytes correlates with its inability to bind to CCR1, a cloned human MIP-1alpha receptor. In addition, studies using proteoglycan deficient cells transfected with CCR1 have indicated that the proteoglycan binding site in MIP-1alpha is a site that is also involved in the docking of MIP-1alpha to the monocyte receptor. The site for interaction with the stem cell receptor must therefore be distinct, suggesting that MIP-1alpha utilizes different receptors for these two different biological processes.
我们研究了蛋白聚糖在巨噬细胞炎性蛋白-1α（MIP-1α）功能中的作用，MIP-1α是蛋白聚糖结合趋化因子家族的一员。序列和肽分析已确定MIP-1α内的一个碱性区域，该区域似乎是蛋白聚糖结合的主要决定因素，我们现在制备了一种MIP-1α突变体，该突变体在这个蛋白聚糖结合位点的两个氨基酸上缺少碱性电荷。这种突变体（Hep Mut）似乎失去了与蛋白聚糖结合的能力。对Hep Mut的生物测定表明，它保留了干细胞抑制特性，但作为单核细胞趋化剂的活性受损，因此表明MIP-1α的这两种特性解偶联。受体研究表明，Hep Mut对人单核细胞无活性与其无法结合克隆的人MIP-1α受体CCR1有关。此外，使用转染了CCR1的蛋白聚糖缺陷细胞的研究表明，MIP-1α中的蛋白聚糖结合位点也是MIP-1α与单核细胞受体对接所涉及的位点。因此，与干细胞受体相互作用的位点必然不同，这表明MIP-1α在这两个不同的生物学过程中利用不同的受体。
