C-terminal Modification of Osteopontin Inhibits Interaction with the αVβ3-Integrin
C-terminal Modification of Osteopontin Inhibits Interaction with the αVβ3-Integrin
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DOI：
10.1074/jbc.m111.277996
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发表时间：
2012-02-03
影响因子：
4.8
通讯作者：
Sorensen, Esben S.
中科院分区：
文献类型：
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作者：
Christensen, Brian;Klaning, Eva;Sorensen, Esben S.
骨桥蛋白(OPN)是一种含有整合素结合序列Arg-Gly-Asp的多功能磷酸化蛋白，通过它与多种整合素受体相互作用，如α(V)、β(3)-整合素。OPN存在于许多不同的亚型中，它们的磷酸化状态不同，可能与整合素有不同的相互作用。OPN的C-末端区域在哺乳动物中特别保守，这表明该区域具有重要的功能。在这项研究中，我们发现OPN极端C末端的修饰在与α(V)、β(3)-整合素的相互作用中起着重要的调节作用。研究表明，与磷酸化程度较低的形式相比，高度磷酸化的OPN通过α(V)β(3)-整合素促进细胞黏附的能力大大降低。高度磷酸化的OPN可以通过去磷酸化和蛋白水解性去除C末端来极大地增加细胞的附着。使用在N端或C端含有标签的重组表达的OPN，结果表明，C端的修饰显著降低了细胞通过α(V)β(3)整合素与OPN的黏附，而N端的修饰不影响结合。通过凝血酶和纤溶酶去除蛋白水解性C末端，可以恢复被抑制的α(V)β(3)整合素与OPN的结合。这些数据说明了一种新的机制，通过修改蛋白质高度保守的C-末端区域来调节OPN和α(V)β(3)整合素的相互作用。
Osteopontin (OPN) is a multifunctional phosphorylated protein containing the integrin binding sequence Arg-Gly-Asp through which it interacts with several integrin receptors, such as the alpha(V)beta(3)-integrin. OPN exists in many different isoforms differing in phosphorylation status that are likely to interact differently with integrins. The C-terminal region of OPN is particularly well conserved among mammalian species, which suggests an important functional role of this region. In this study, we show that modification of the extreme C terminus of OPN plays an important regulatory role for the interaction with the alpha(V)beta(3)-integrin. It is demonstrated that highly phosphorylated OPN has a much reduced capability to promote cell adhesion via the alpha(V)beta(3)-integrin compared with lesser phosphorylated forms. The cell attachment promoted by highly phosphorylated OPN could be greatly increased by both dephosphorylation and proteolytic removal of the C terminus. Using recombinantly expressed OPN containing a tag in the N or C terminus, it is shown that a modification in the C-terminal part significantly reduces the adhesion of cells to OPN via the alpha(V)beta(3)-integrin, whereas modification of the N terminus does not influence the binding. The inhibited binding of the alpha(V)beta(3)-integrin to OPN could be restored by proteolytic removal of the C terminus by thrombin and plasmin. These data illustrate a novel mechanism regulating the interaction of OPN and the alpha(V)beta(3)-integrin by modification of the highly conserved C-terminal region of the protein.