The Inflammation-associated Protein TSG-6 Cross-links Hyaluronan via Hyaluronan-induced TSG-6 Oligomers
The Inflammation-associated Protein TSG-6 Cross-links Hyaluronan via Hyaluronan-induced TSG-6 Oligomers
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DOI：
10.1074/jbc.m111.247395
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发表时间：
2011-07-22
影响因子：
4.8
通讯作者：
Richter, Ralf P.
中科院分区：
文献类型：
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作者：
Baranova, Natalia S.;Nileback, Erik;Richter, Ralf P.
肿瘤坏死因子刺激基因-6（TSG-6）是一种透明质酸（HA）结合蛋白，在炎症和排卵中起重要作用。TSG-6介导的HA交联已被提出作为一种功能机制（例如，G.用于调节白细胞粘附），但缺乏交联的直接证据，并且我们对其对HA超微结构的影响知之甚少。在这里，我们使用的聚合物和低聚物HA链，最终接枝到固体支持物的薄膜，并结合表面敏感的生物物理技术，以量化的结合TSG-6到HA膜和相关的结合形态变化。我们发现，全长TSG-6与明显的正协同性结合，并证明它可以在生理相关浓度下交联HA。我们的数据表明，全长TSG-6的合作结合产生HA诱导的蛋白质寡聚化和TSG-6寡聚体作为交联剂。相比之下，TSG-6的HA结合结构域（连接模块）单独结合而没有正协同性，并且比全长蛋白弱。Link模块和全长TSG-6都使HA膜冷凝和硬化，并且冷凝程度与TSG-6结构和HA之间的亲和力成比例。我们提出，缩合是蛋白质介导的HA交联的结果。我们的研究结果坚定地确立了TSG-6是一种有效的HA交联剂，因此可能对TSG-6的生物学功能（例如在炎症中）的机制理解具有重要意义。
Tumor necrosis factor-stimulated gene-6 (TSG-6) is a hyaluronan (HA)-binding protein that plays important roles in inflammation and ovulation. TSG-6-mediated cross-linking of HA has been proposed as a functional mechanism (e. g. for regulating leukocyte adhesion), but direct evidence for cross-linking is lacking, and we know very little about its impact on HA ultrastructure. Here we used films of polymeric and oligomeric HA chains, end-grafted to a solid support, and a combination of surface-sensitive biophysical techniques to quantify the binding of TSG-6 into HA films and to correlate binding to morphological changes. We find that full-length TSG-6 binds with pronounced positive cooperativity and demonstrate that it can cross-link HA at physiologically relevant concentrations. Our data indicate that cooperative binding of full-length TSG-6 arises from HA-induced protein oligomerization and that the TSG-6 oligomers act as cross-linkers. In contrast, the HA-binding domain of TSG-6 (the Link module) alone binds without positive cooperativity and weaker than the full-length protein. Both the Link module and full-length TSG-6 condensed and rigidified HA films, and the degree of condensation scaled with the affinity between the TSG-6 constructs and HA. We propose that condensation is the result of protein-mediated HA cross-linking. Our findings firmly establish that TSG-6 is a potent HA cross-linking agent and might hence have important implications for the mechanistic understanding of the biological function of TSG-6 (e.g. in inflammation).