Exocytosis and Endocytosis Notes PDF

Exocytosis and Endocytosis Notes Exocytosis and Vesicle Transport: 1. SNARE Proteins: Provide energy for membrane fusion during exocytosis. 2. Rabs/GAPs: Bind to specific effectors to aid in vesicle docking. 3. Golgi Apparatus (Exocytosis): Sorts proteins for different vesicles. 4. TGN (Trans-Golgi...

Exocytosis and Endocytosis Notes Exocytosis and Vesicle Transport: 1. SNARE Proteins: Provide energy for membrane fusion during exocytosis. 2. Rabs/GAPs: Bind to specific effectors to aid in vesicle docking. 3. Golgi Apparatus (Exocytosis): Sorts proteins for different vesicles. 4. TGN (Trans-Golgi Network): Sorts and packages proteins for transport. 5. GTPase Activating Protein (GAP): Activates GTPase involved in vesicle transport. 6. Glycosphingolipid: Anchors proteins to lipid rafts, assisting in membrane organization. 7. Chemical Messenger: Triggers the fusion of secretory vesicles in regulated exocytosis. 8. Clathrin-Coated Vesicles: Help recycle vesicle components back to the membrane after release. 9. Clathrin: Forms a 'coat' around vesicles, helping to mediate vesicle budding. 10. Pinching: Is not part of regulated exocytosis. Types of Exocytosis: 1. Constitutive Exocytosis: Occurs continuously in cells and does not require specific signals. 2. Kinesin & Dynein: Motor proteins that transport vesicles along microtubules. Endocytosis (Module 17): 1. Receptor-Mediated Endocytosis: Involves clathrin-coated pits. 2. Clathrin-Coated Vesicles: Fuse with early endosomes for material sorting. 3. Polarized Epithelial Cells: Endocytosis occurs from both the basolateral and apical domains. 4. Adaptins: Bind to clathrin coat and receptor proteins in vesicles to mediate cargo sorting. 5. Transferrin: Ligand recycled back into its receptor after delivering iron to the early endosome. 6. Triskelion (Clathrin): Clathrin forms an assembly on the membrane. 7. COPI: Involved in retrograde transport (Golgi to ER). 8. COPII: Involved in exocytosis (ER to Golgi). Other Processes: 1. Actin Polymerization (Phagocytosis): Triggered by binding of ligands. 2. Transcytosis: Transfer of compounds across polarized cells. 3. Caveolar Endocytosis (Clathrin-Independent): Uses caveolae to uptake materials. 4. Caveolae: Small invaginations that mediate clathrin-independent endocytosis. 5. Accessory Proteins: Assist in recruiting clathrin and bending the membrane during vesicle formation. Quiz 25: Endocytosis Steps (Complete) 1. Initiation of Coat Assembly: Cargo and SNARE proteins begin to gather and form a coat. 2. Budding: Membrane curvature increases as vesicle forms. 3. Scission: Severing occurs, often mediated by coat or accessory proteins. 4. Uncoating: Coat may be recycled for future vesicles. 5. Tethering: Naked vesicle is tethered by Rab-GTP or effectors. 6. Docking: Vesicle SNAREs assemble to complete the fusion process. Additionally: - RAB Proteins: The docking and tethering process requires RAB to bind to specific effectors. - Adaptor Protein: Mediates the binding between the coat and transmembrane proteins (including cargo receptors).