Department of Molecular Health Sciences, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1, Tanabe-Dori, Nagoya 467-8603, Japan.
Biochem Biophys Res Commun. 2013 Mar 29;433(1):127-32. doi: 10.1016/j.bbrc.2013.02.050. Epub 2013 Feb 26.
Staphylococcal superantigen-like protein (SSL), a family of exotoxins composed of 14 SSLs, exhibits no superantigenic activity despite of its structural similarity with superantigens. Several SSLs have been revealed to bind to host immune molecules such as IgA, IgG, complement and cell surface molecules expressed on immune cells, but the physiological function of SSL family has not been fully identified. In this study we attempted to isolate host target proteins of SSLs from human breast milk using SSLs-conjugated Sepharose. SSL8-conjugated Sepharose specifically recovered tenascin C (TNC), a multimodular and multifunctional extracellular matrix protein. Pull down analysis using SSL8-conjugated Sepharose and recombinant truncated fragments of TNC revealed that SSL8 interacts with fibronectin (FN) type III repeats 1-5 of TNC. The interaction of TNC with immobilized FN was attenuated, the scratch wound closure by HaCaT human keratinocytes was delayed and the inhibition of cell spreading on FN by TNC was recovered in the presence of SSL8. These findings suggest that SSL8 binds to TNC, thereby inhibits the TNC-FN interaction and motility of keratinocytes. The present study added a novel role of SSL family protein as an interrupting molecule against the function of extracellular matrix.
葡萄球菌超抗原样蛋白（SSL）是由 14 种 SSL 组成的外毒素家族，尽管其结构与超抗原相似，但不具有超抗原活性。已经发现一些 SSL 与宿主免疫分子如 IgA、IgG、补体和表达在免疫细胞上的细胞表面分子结合，但 SSL 家族的生理功能尚未完全确定。在这项研究中，我们试图使用 SSL 偶联的琼脂糖从人乳中分离 SSL 的宿主靶蛋白。SSL8 偶联的琼脂糖特异性回收 tenascin C（TNC），一种多功能的细胞外基质蛋白。使用 SSL8 偶联的琼脂糖和 TNC 的重组截短片段进行下拉分析表明，SSL8 与 TNC 的纤连蛋白（FN）III 型重复 1-5 相互作用。TNC 与固定化 FN 的相互作用减弱，HaCaT 人角质形成细胞的划痕伤口闭合延迟，TNC 恢复了 FN 上细胞铺展的抑制。这些发现表明 SSL8 与 TNC 结合，从而抑制 TNC-FN 相互作用和角质形成细胞的运动。本研究为 SSL 家族蛋白作为一种阻断细胞外基质功能的中断分子增添了新的作用。
