Integrin αIIbβ3 Activation in Chinese Hamster Ovary Cells and Platelets Increases Clustering Rather than Affinity
Integrin αIIbβ3 Activation in Chinese Hamster Ovary Cells and Platelets Increases Clustering Rather than Affinity
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DOI：
10.1074/jbc.m109.057349
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发表时间：
2010-01-15
影响因子：
4.8
通讯作者：
Bunch, Thomas A.
中科院分区：
文献类型：
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作者：
Bunch, Thomas A.
在中国仓鼠卵巢细胞和人血小板中，整合素αIIIβ3亲和力调节通过Talin与β3胞浆尾部结合是一个普遍接受的模型来解释这种整合素的激活。这一模型的大部分证据来自多价配体的使用。这增加了被测量的激活是整合素聚集增加的可能性，而不是亲和力的增加。使用一种新开发的方法，在固定前只探测单价配体细胞表面的整合素，我没有发现中国仓鼠卵巢细胞中Talin头部片段增加了αIIIβ3整合素的亲和力，也没有观察到凝血酶刺激的人血小板亲和力增加。在这两种情况下，与多价配体的结合都会增加。这项检测确实报告了β3细胞质结构域的突变体(D723R)Mn2+或与多肽配体预先孵育所诱导的亲和力增加。这些结果与先前观察到的在果蝇和脊椎动物系统中Talin对整合素激活的影响之间的差异相一致，并为Talin调节人类血小板整合素活性提供了新的模式。
Integrin alpha III beta 3 affinity regulation by talin binding to the cytoplasmic tail of beta 3 is a generally accepted model for explaining activation of this integrin in Chinese hamster ovary cells and human platelets. Most of the evidence for this model comes from the use of multivalent ligands. This raises the possibility that the activation being measured is that of increased clustering of the integrin rather than affinity. Using a newly developed assay that probes integrins on the surface of cells with only monovalent ligands prior to fixation, I do not find increases in affinity of alpha III beta 3 integrins by talin head fragments in Chinese hamster ovary cells, nor do I observe affinity increases in human platelets stimulated with thrombin. Binding to a multivalent ligand does increase in both of these cases. This assay does report affinity increases induced by either Mn2+, a cytoplasmic domain mutant (D723R) in the cytoplasmic domain of beta 3, or preincubation with a peptide ligand. These results reconcile the previously observed differences between talin effects on integrin activation in Drosophila and vertebrate systems and suggest new models for talin regulation of integrin activity in human platelets.