Establishment of Ryudocan Null Mouse and ELISA for Blood Levels of Ryudocan

在纤维连接蛋白上形成局灶性黏附需要两个信号，即一个来自纤维连接蛋白的细胞结合域，一个来自肝素结合域。虽然整合素可以识别细胞结合结构域，但识别肝素结合结构域的细胞表面分子尚未确定。先前的报道表明，硫酸肝素蛋白多糖ryudocan （syndecan-4）是局灶粘连的一个组成部分，抗syndecan-4抗体可以促进局灶粘连的形成。因此，ryudocan是识别肝素结合结构域的候选者。为了研究syndecan-4在局灶黏附形成中的作用，我们建立了yudocan缺失小鼠。即使在琉球核（-/-）成纤维细胞中，也能形成局灶粘连，肌动蛋白纤维在局灶粘连处正常终止。然而，在细胞结合片段上培养的琉球can（-/-）成纤维细胞中，可溶形式的纤连蛋白肝素结合片段和抗琉球can抗体都不能促进局灶粘连的形成。因此，本研究揭示了可溶性形式的肝素结合片段需要琉球酶来形成局灶黏附，而固体形式的肝素结合片段不仅可以利用琉球酶，还可以利用一些未知的细胞表面分子。

Focal adhesion formation on fibronectin requires two signals, i.e. one from the cell-binding domain of fibronectin and one from the heparin-binding domain. While the cell-binding domain is recognized by integrins, the cell surface molecules that recognize the heparin-binding domain have not been identified. Previous reports have demonstrated that ryudocan (syndecan-4), a heparan sulfate proteoglycan, is a component of focal adhesions and that anti-syndecan-4 antibody can promote focal adhesion formation. Thus, ryudocan is a candidate that recognizes the heparin-binding domain. To study the role of syndecan-4 in focal adhesion formation, we generated ryudocan null mice. Even in ryudocan (-/-) fibroblasts, focal adhesions were formed and actin fibers terminated normally at focal adhesions. However, neither the fibronectin heparin-binding fragment in a soluble form nor anti-ryudocan antibody promoted focal adhesion formation in ryudocan (-/-) fibroblasts cultured on the cell-binding fragment, promoted focal adhesion formation. Thus, the present study has revealed that the heparin-binding fragment in a soluble form requires ryudocan for focal adhesion formation, whereas one in a solid form could utilize not only ryudocan but also some unidentified cell surface molecules.