Dynamitin controls β2 integrin avidity by modulating cytoskeletal constraint on integrin molecules
Dynamitin controls β2 integrin avidity by modulating cytoskeletal constraint on integrin molecules
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DOI：
10.1074/jbc.m201525200
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发表时间：
2002-09-06
影响因子：
4.8
通讯作者：
Li, JX
中科院分区：
文献类型：
--
作者：
Jin, TQ;Li, JX
动力素是微管依赖性运动复合体的一个亚基，通过与MacMARCKS（巨噬细胞富集的肉豆蔻酰丙氨酸-水稻C激酶底物）结合参与细胞粘附。然而，尽管MacMARCKS和微管都调节β（2）整合素的活化，动力素如何参与细胞粘附尚不清楚。我们报道了dynamitin通过调节β 2整合素分子的横向移动性来调节β 2整合素对iC 3b的亲合力。使用单粒子追踪方法，我们发现在表达融合蛋白CFP（青色荧光蛋白）-动力素或CFP-MB（动力素的MacMARCKS结合域肽）的细胞中，整合素分子的迁移率比对照细胞增加了6倍，表明干扰动力素功能显著改变了β 2整合素分子的细胞骨架约束。进一步的机制研究表明，dynamitin的过表达刺激了内源性MacMARCKS蛋白的磷酸化，从而导致桩蛋白的酪氨酸磷酸化增强。动力素的这种作用与观察结果相关，即需要更高浓度的PKC抑制剂来阻断表达动力素的细胞中β 2整合素的迁移。虽然dynamitin作用于MacMARCKS磷酸化位点，但它位于RhoA的上游，因为它的作用被RhoA抑制剂阻断。因此，我们得出结论，dynamitin是细胞骨架约束的一部分，锁定β（2）整合素的非活性形式。
Dynamitin, a subunit of the microtubule-deperident motor complex, was implicated in cell adhesion by binding to MacMARCKS (Macrophage-enriched Myristoylated alanine-rice C kinase substrate). However, how dynamitin is involved in cell adhesion is unclear despite the fact that both MacMARCKS and microtubules regulate beta(2) integrin activation. We report that dynamitin regulates beta(2) integrin avidity toward iC3b by modulating the lateral mobility of beta(2) integrin molecules. Using the single particle tracking method, we found that integrin molecular mobility in cells expressing the fusion protein CFP (cyan fluorescent protein)-dynamitin or CFP-MB (the MacMARCKS binding domain peptide of dynamitin) increased 6-fold over the control cells, suggesting that disturbing dynamitin function dramatically altered the cytoskeletal constraint on beta(2) integrin molecules. Further mechanistic studies revealed that overexpression of dynamitin stimulated the phosphorylation of endogenous MacMARCKS protein, which lead to the enhanced tyrosine phosphorylation of paxillin. This effect of dynamitin correlates with the observation that higher concentration of PKC inhibitor is required to block beta(2) integrin mobility in dynamitin-expressing cells. Although dynamitin acts at the point of MacMARCKS phosphorylation, it is upstream of RhoA, because its effect was blocked by RhoA inhibitor. Thus, we conclude that dynamitin is a part of the cytoskeletal constraint that locks beta(2) integrin in the inactive form.