- 學位論文
模擬被clathrin蛋白質覆蓋的板塊狀胞吞作用
Modeling Endocytosis of a Clathrin-Coated Plaque
摘要
在胞吞作用的初期，clathrin 蛋白質會在細胞膜上聚集並形成晶格，這個晶格會離開細胞膜並形成一個運輸囊泡，藉此細胞外的物質以及被clathrin 晶格覆蓋的細胞膜就會被運輸進細胞內。clathrin 晶格有兩種截然不同的形狀，一種是彎曲的＂坑＂，另一種是平板狀的＂板塊＂。實驗上發現，板塊只會出現在細胞膜跟基板交界的內面，它們會在基板上停留幾分鐘然後進入細胞，除此之外，它們生長以及離開基板的過程都需要肌動蛋白網絡。根據這些結果我們建立一個理論模型。在此模型中，一旦板塊離開基底，肌動蛋白網絡的能量就會下降。我們發現，當肌動蛋白網絡長得大，系統的自由能就會隨著板塊的高度上升而單調下降，被肌動蛋白網絡擠壓的板塊就會被抬離基底。我們也發現，相較於小的板塊，大的板塊在基板上停留的時間比較久。
並列摘要
In the early stage of clathrin mediated endocytosis, clathrin proteins aggregate and form a lattice on the cell membrane, which then pinches off and becomes a traffic vesicle. In this way, extracellular materials and an area of membrane are delivered into the cell. There are two distinct shapes of clathrin lattices, one is curved ``coated pit", the other one is flat ``coated plaque''. Experimental works indicate that a clathrin plaque only grows on the ventral membrane of a cell which is adhered to the substrate. The plaque-coated membrane stays on the substrate for several minutes before being internalized. The growth of the actin network around a plaque is also essential for the formation and internalization of the plaque. From these fact we build a model in which the release of the elastic free energy of the growing actin network lead to the detachment of the clathrin plaque from the substrate. We find that a plaque is compressed by the growing actin network and tends to internalize when the growing actin network reaches a critical size. We also find that a large plaque is relatively stable and live longer than a small plaque.