ATP release due to Thy-1-integrin binding induces P2X7-mediated calcium entry required for focal adhesion formation
ATP release due to Thy-1-integrin binding induces P2X7-mediated calcium entry required for focal adhesion formation
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DOI：
10.1242/jcs.073171
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发表时间：
2011-05-01
影响因子：
4
通讯作者：
Leyton, Lisette
中科院分区：
文献类型：
--
作者：
Henriquez, Mauricio;Herrera-Molina, Rodrigo;Leyton, Lisette
THY-1是一种丰富的哺乳动物糖蛋白，它与星形胶质细胞中的αvβ3整合素和Syndecan-4相互作用，从而触发涉及RhoA及其效应器p160ROCK的信号事件，从而增加星形胶质细胞与细胞外基质的黏附。该信号级联包括Rho上游蛋白激酶Cα的钙依赖激活；然而，促进黏附所需的细胞内钙瞬变的原因尚不清楚。嘌呤能的P2X7受体对星形胶质细胞的功能非常重要，当与其配体ATP结合时，它会形成巨大的非选择性阳离子孔道。因此，我们评估了Thy1诱导细胞黏附所需的细胞内钙是否源于ATP激活的P2X7受体介导的内流。结果表明，融合蛋白Thy-1-Fc诱导的黏附先于ATP的释放和细胞内钙的持续升高。用apyrase消除细胞外ATP，用EGTA螯合细胞外钙，或用氧化的ATP抑制P2X7，均分别阻断细胞内钙的增加和Thy-1刺激的黏附。此外，在整合素结合部位突变的Thy-1不会触发ATP的释放，而用特定的siRNA沉默P2X7可以阻断Thy-1诱导的黏附。这项研究首次证明了αvβ3整合素和P2X7受体之间的功能联系，并揭示了P2X7在Thy-1刺激的星形胶质细胞黏附所需的钙依赖信号中所起的重要作用，这是迄今尚未预料到的。
Thy-1, an abundant mammalian glycoprotein, interacts with alpha v beta 3 integrin and syndecan-4 in astrocytes and thus triggers signaling events that involve RhoA and its effector p160ROCK, thereby increasing astrocyte adhesion to the extracellular matrix. The signaling cascade includes calcium-dependent activation of protein kinase C alpha upstream of Rho; however, what causes the intracellular calcium transients required to promote adhesion remains unclear. Purinergic P2X7 receptors are important for astrocyte function and form large non-selective cation pores upon binding to their ligand, ATP. Thus, we evaluated whether the intracellular calcium required for Thy1- induced cell adhesion stems from influx mediated by ATP-activated P2X7 receptors. Results show that adhesion induced by the fusion protein Thy-1-Fc was preceded by both ATP release and sustained intracellular calcium elevation. Elimination of extracellular ATP with Apyrase, chelation of extracellular calcium with EGTA, or inhibition of P2X7 with oxidized ATP, all individually blocked intracellular calcium increase and Thy-1-stimulated adhesion. Moreover, Thy-1 mutated in the integrin-binding site did not trigger ATP release, and silencing of P2X7 with specific siRNA blocked Thy-1-induced adhesion. This study is the first to demonstrate a functional link between alpha v beta 3 integrin and P2X7 receptors, and to reveal an important, hitherto unanticipated, role for P2X7 in calcium-dependent signaling required for Thy-1-stimulated astrocyte adhesion.