Actin Binding of Ezrin Is Activated by Specific Recognition of PIP2-Functionalized Lipid Bilayers

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• 作者：Matthias Janke ; Alexander Herrig ; Judith Austermann ; Volker Gerke ; Claudia Steinem ; Andreas Janshoff
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：March 25, 2008
• 年：2008
• 卷：47
• 期：12
• 页码：3762 - 3769
• 全文大小：3929K
• 年卷期：v.47,no.12(March 25, 2008)
• ISSN：1520-4995

文摘

In a quantitative manner, we investigated the mechanism of switching ezrin from the dormant to the active, F-actin binding state by recognition of PIP₂. For this purpose, we established a novel in vitro model mimicking ezrin-mediated membrane−cytoskeleton attachment and compared the F-actin binding capability of ezrin that either had been coupled via a His tag to a lipid bilayer displaying Ni-NTA or had been bound to supported membranes containing PIP₂. Epifluorescence and colloidal probe microscopy (CPM) were employed to demonstrate ezrin’s conformational switch into an active conformation capable of binding F-actin. Epifluorescence images revealed attachment of fluorescently labeled F-actin solely to PIP₂-bound ezrin. For the first time, colloidal spheres equipped with an artificial cytoskeleton composed of firmly attached F-actin filaments were used to measure quantitatively the maximal adhesion forces and the work of adhesion of the ezrin−F-actin interface. We found that the work of adhesion between PIP₂-bound ezrin and F-actin is substantially larger than that measured between F-actin and ezrin bound to the membrane via the His tag. Collectively, these data indicate that activation of ezrin can occur as a consequence of PIP₂ binding and does not require additional cofactors.