Actin filaments as dynamic reservoirs for Drp1 recruitment.
Actin filaments as dynamic reservoirs for Drp1 recruitment.
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DOI：
10.1091/mbc.e16-03-0193
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发表时间：
2016-10-15
影响因子：
3.3
通讯作者：
Higgs HN
中科院分区：
文献类型：
--
作者：
Hatch AL;Ji WK;Merrill RA;Strack S;Higgs HN
肌动蛋白刺激线粒体分裂蛋白Drp 1的寡聚化和线粒体积累。drp 1结合肌动蛋白丝在一个不寻常的动态方式，强烈影响鸟嘌呤核苷酸。Drp 1是一个动力蛋白家族GT3，被招募到线粒体和过氧化物酶体，在那里它寡聚化并驱动膜分裂。线粒体Drp 1募集的调节尚未完全了解。我们以前表明，Drp 1直接结合肌动蛋白丝，肌动蛋白聚合是必要的线粒体Drp 1寡聚化在哺乳动物。在这里，我们显示Drp 1/肌动蛋白相互作用显示不寻常的属性，受几个因素的影响。在饱和状态下，只有一部分Drp 1结合肌动蛋白丝，未结合的Drp 1显著增加肌动蛋白结合的Drp 1的解离速率。GDP和GTP分别加速和减速Drp 1/肌动蛋白结合动力学。肌动蛋白对Drp 1 GTP水解具有双相作用，在低肌动蛋白：Drp 1比率下增加，但在高比率下返回基线。Drp 1也束丝。束具有降低的动力学，但遵循与单丝相同的趋势。Drp 1优先纳入束在较高的离子强度。我们在U2 OS细胞胞液中测得Drp 1的浓度约为0.5 μM，表明此处测得的肌动蛋白结合亲和力（Kd = 0.6 μM）在生理相关范围内。Drp 1以高度动态的方式结合肌动蛋白丝的能力为肌动蛋白丝提供了潜在的可能性，可以作为线粒体分裂的寡聚化能力Drp 1的水库。
Actin stimulates oligomerization and mitochondrial accumulation of Drp1, a mitochondrial fission protein. Drp1 binds actin filaments in an unusually dynamic manner that is strongly influenced by guanine nucleotide. Drp1 is a dynamin-family GTPase recruited to mitochondria and peroxisomes, where it oligomerizes and drives membrane fission. Regulation of mitochondrial Drp1 recruitment is not fully understood. We previously showed that Drp1 binds actin filaments directly, and actin polymerization is necessary for mitochondrial Drp1 oligomerization in mammals. Here we show the Drp1/actin interaction displays unusual properties that are influenced by several factors. At saturation, only a fraction Drp1 binds actin filaments, and the off-rate of actin-bound Drp1 is significantly increased by unbound Drp1. GDP and GTP accelerate and decelerate Drp1/actin binding dynamics, respectively. Actin has a biphasic effect on Drp1 GTP hydrolysis, increasing at low actin:Drp1 ratio but returning to baseline at high ratio. Drp1 also bundles filaments. Bundles have reduced dynamics but follow the same trends as single filaments. Drp1 preferentially incorporates into bundles at higher ionic strength. We measure Drp1 concentration to be ∼0.5 μM in U2OS cell cytosol, suggesting the actin-binding affinity measured here (Kd = 0.6 μM) is in the physiologically relevant range. The ability of Drp1 to bind actin filaments in a highly dynamic manner provides potential for actin filaments to serve as reservoirs of oligomerization-competent Drp1 that can be accessed for mitochondrial fission.