Mechanistic differences in actin bundling activity of two mammalian formins, FRL1 and mDia2
Mechanistic differences in actin bundling activity of two mammalian formins, FRL1 and mDia2
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DOI：
10.1074/jbc.m510923200
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发表时间：
2006-05-19
影响因子：
4.8
通讯作者：
Higgs, Henry N.
中科院分区：
文献类型：
--
作者：
Harris, Elizabeth S.;Rouiller, Isabelle;Higgs, Henry N.
形成蛋白是肌动蛋白动力学的调节剂，介导无分支肌动蛋白丝的组装。这些多结构域蛋白质由形成蛋白同源性2（FH 2）结构域的存在来定义。先前的工作已经表明，FH2结构域结合到细丝倒刺末端，并且随着细丝伸长在倒刺末端向前移动。在这里，我们报告说，两个FH2域，从哺乳动物FRL 1和mDia2，也束丝，而从mDia1的FH2域不能在类似的条件下。单独的FH2域足以用于捆绑。由FRL 1或mDia2制成的成束长丝处于平行和反平行取向。可能有助于捆绑的一种新性质是来自FRL 1和mDia2的二聚体FH2结构域解离和重组的能力。对于mDia1，未观察到此属性。FRL 1和mDia2之间的差异在于FRL 1介导的捆绑与倒刺末端结合竞争，而mDia2介导的捆绑则不是。FH2结构域中高度保守的异亮氨酸残基的突变不抑制FRL 1或mDia2的捆绑，但抑制倒刺末端活性。然而，这种突变的严重性在formin之间变化。对于mDia1和mDia2，突变强烈抑制倒刺末端结合的所有影响，但对FRL 1的影响要小得多。此外，我们的研究结果表明，Ile突变影响持续合成能力。两者合计，我们的数据表明，捆绑活动的FRL 1和mDia2，而产生表型相似的束，不同的机制细节。
Formin proteins are regulators of actin dynamics, mediating assembly of unbranched actin filaments. These multidomain proteins are defined by the presence of a Formin Homology 2 (FH2) domain. Previous work has shown that FH2 domains bind to filament barbed ends and move processively at the barbed end as the filament elongates. Here we report that two FH2 domains, from mammalian FRL1 and mDia2, also bundle filaments, whereas the FH2 domain from mDia1 cannot under similar conditions. The FH2 domain alone is sufficient for bundling. Bundled filaments made by either FRL1 or mDia2 are in both parallel and anti-parallel orientations. A novel property that might contribute to bundling is the ability of the dimeric FH2 domains from both FRL1 and mDia2 to dissociate and recombine. This property is not observed for mDia1. A difference between FRL1 and mDia2 is that FRL1-mediated bundling is competitive with barbed end binding, whereas mDia2-mediated bundling is not. Mutation of a highly conserved isoleucine residue in the FH2 domain does not inhibit bundling by either FRL1 or mDia2, but inhibits barbed end activities. However, the severity of this mutation varies between formins. For mDia1 and mDia2, the mutation strongly inhibits all effects of barbed end binding, but affects FRL1 much less strongly. Furthermore, our results suggest that the Ile mutation affects processivity. Taken together, our data suggest that the bundling activities of FRL1 and mDia2, while producing phenotypically similar bundles, differ in mechanistic detail.