University:
Kentucky State University
Course:
BIO 408 | Cell Biology
Academic year:

2019
Views:

494

Pages:

9
Author:

Sean Horton

Formation and Fusion of a Transport Vesicle right after budding Vesicular transport Coat disassembly in cytosol before reaching target membrane Vesicular docking & fusion 3 Coat Proteins Different coating proteins (clathrin, COPI and COPII) depending on:  The direction of movement  The budding location  The final destination 4 Formation of clathrin-coated vesicles 5 The role of ARF1 in COPI- and clathrin- coated vesicle formation 1. Activation of ARF1 by GEF 2. Recruitment of adaptor protein AP1 and then clathrin 3. Formation of ARF1-clathrinreceptor-cargo complex 4. Formation of vesicle 5. Budding and transport of vesicle 6. Inactivation of ARF1 by GTP hydrolysis and disassembly of coat 7. Vesicle fusion 1 2 3 6 Vesicular fusion • The formation of v-SNAREs-t-SNAREs complexes leads to membrane fusion. • GTP-binding Rab proteins function in several steps of vesicle trafficking. • Different combinations of Rab proteins mark different organelles and transport vesicles. • Effector proteins allow for specific interaction 7 The mechanism of fusion Docking Interaction of Rabs with effector proteins and SNAREs Fusion Tethering, hydrolysis of GTP, SNARE interactions Closer vesicletarget induces membrane instability Disassembly of SNARE complex needs energy (ATP) Exocytosis Exocysts are specific protein complexes (8 proteins) at which exocytosis occurs Exocysts protein interaction results in efficient targeting of the vesicle to a specific 9 location on plasma membrane. Clinical Application: Griscelli syndrome (GS) • A rare genetic condition • Type: GS1, GS2, GS3 • Mutations in MYO5A, RAB27A and MLPH genes that encode the MyoVA-Rab27a-Mlph protein complex that function in melanosome transport and fusion. • Pigmentary dilution of the skin, silver-grey hair, melanin clumps within hair shafts • Mature melanosomes accumulate in the center of melanocytes. 10