Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA.
Mol Biol Cell. 2010 Aug 15;21(16):2905-15. doi: 10.1091/mbc.E10-06-0494. Epub 2010 Jun 29.
We used the dendritic nucleation hypothesis to formulate a mathematical model of the assembly and disassembly of actin filaments at sites of clathrin-mediated endocytosis in fission yeast. We used the wave of active WASp recruitment at the site of the patch formation to drive assembly reactions after activation of Arp2/3 complex. Capping terminated actin filament elongation. Aging of the filaments by ATP hydrolysis and gamma-phosphate dissociation allowed actin filament severing by cofilin. The model could simulate the assembly and disassembly of actin and other actin patch proteins using measured cytoplasmic concentrations of the proteins. However, to account quantitatively for the numbers of proteins measured over time in the accompanying article (Sirotkin et al., 2010, MBoC 21: 2792-2802), two reactions must be faster in cells than in vitro. Conditions inside the cell allow capping protein to bind to the barbed ends of actin filaments and Arp2/3 complex to bind to the sides of filaments faster than the purified proteins in vitro. Simulations also show that depolymerization from pointed ends cannot account for rapid loss of actin filaments from patches in 10 s. An alternative mechanism consistent with the data is that severing produces short fragments that diffuse away from the patch.
我们利用树突状成核假说，构建了裂殖酵母网格蛋白介导内吞作用位点处肌动蛋白丝组装和解聚的数学模型。我们利用斑块形成部位处活跃的 WASp 募集波来驱动 Arp2/3 复合物激活后的组装反应。封端蛋白终止肌动蛋白丝的延伸。ATP 水解和γ-磷酸基团解离导致肌动蛋白丝老化，从而被肌动蛋白丝切割蛋白切断。该模型可以使用测量的细胞质蛋白浓度来模拟肌动蛋白和其他肌动蛋白斑块蛋白的组装和拆卸。然而，为了定量解释伴随文章（Sirotkin 等人，2010 年，《Molecular Biology of the Cell》21: 2792-2802）中随时间测量的蛋白数量，有两个反应必须在细胞内比在体外更快。细胞内的条件允许封端蛋白结合到肌动蛋白丝的游离端，以及 Arp2/3 复合物结合到肌动蛋白丝的侧面，这比体外纯化的蛋白快。模拟还表明，从尖端解聚不能解释在 10 秒内从斑块中快速损失肌动蛋白丝。一个与数据一致的替代机制是，切割产生的短片段从斑块扩散开。
