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Mechanisms regulating the function of adaptor protein 2 complex during endocytosis
Zounarová, Apolena ; Macůrková, Marie (advisor) ; Pleskot, Roman (referee)
Adaptor protein complex 2 (AP2) mediates the interaction of clathrin with the plasma membrane and thus enables the clathrin-coated vesicle formation. AP2 is also responsible for cargo recognition and it recognizes cargo either directly using endocytic motifs YxxΦ or [DE]xxxL[LI] in the cytosolic domains of cargo or indirectly via additional adaptor proteins from which β-arrestin and ARH are the best-known. The binding sites for endocytic motifs are located in the core of AP2 complex and, similarly to the clathrin-binding site, they are blocked by autoinhibitory mechanism in the inactive cytosolic form of AP2. Therefore, binding of endocytic motifs and clathrin must be preceded by conformational change of AP2 complex which is triggered by membrane-bound phosphatidylinositol-4,5-bisphosphates and greatly facilitated by phosphorylation at Thr156 by AAK1 kinase. AP2 is also important for later stages of endocytosis during which it recruits proteins responsible for membrane curvature, fission, and eventual disassembly of clathrin coat. Repeated association of AP2 with the plasma membrane is prevented by the protein NECAP, but the mechanism of inactivation is still poorly understood.
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Endocytosis in plants
Svitáková, Lenka ; Krtková, Jana (advisor) ; Hála, Michal (referee)
Endocytosis is a process typical for eukaryotic cells. It is a mechanism that ensures invagination of the plasma membrane which leads to the creation of a membrane vesicle with specifically selected cargo. The vesicle is then internalized by the cell. Endocytosis has a crucial role in plant growth and development not only thanks to the reception of nutrients from the extracellular space but also by having a huge impact on the membrane composition which influences cellular signalling. There are few types of endocytosis known in plants. They differ from each other by the molecular machinery which ensures their process. The most studied type in plants is the clathrin-mediated endocytosis. Clathrin-coated vesicle formation proceeds through five stages. However, there are less details known about it in plant cells than in animal cells. In the first part of my bachelor thesis I describe recent knowledge of this topic and the most important participants in this process. I also mention the mechanisms of regulations that plant cells use to coordinate clathrin-mediated endocytosis. In the second part I summarize recently discovered types of endocytosis in plants that are independent from clathrin. These are endocytosis associated with microdomains and fluid- phase endocytosis. The details of these endocytic...
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The role of endocytosis in Wnt signaling pathway
Matějů, Daniel ; Libusová, Lenka (advisor) ; Doubravská, Lenka (referee)
Endocytosis and cell signaling are tightly connected processes. This connection is most obvious at the level of endocytosis of signaling receptors and ligands. For many years, endocytosis of signaling receptors was considered as a negative feedback loop mechanism, which desensitizes the cell after prolonged stimulation by ligand. Now it is evident that the situation is more complex and endocytosis can affect cell signaling both negatively and positively. In this thesis, I will summarize how Wnt signaling can be affected by endocytosis of receptors and ligands of this signaling pathway. Wnt signaling is one of the most important and intensively studied signaling pathways in the metazoan development. Several possible roles of endocytosis in Wnt signaling were uncovered in recent years, some of them unique among other signaling pathways. Understanding the relationship between endocytosis and Wnt signaling will thus help not only to deepen the knowledge of Wnt signaling but also to shed light on the possible roles of endocytosis in regulation of cell signaling in general.
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