英文医学精品课件：Golgi and Endosomes9.21

1、Protein Transport -Proteins move from the ER to VTC vesicular tubular carrier -Proteins move from the VTC to the Golgi -Proteins move from the Golgi to the cell surface,Moving Cargo through organelles Vesicles bud from one organelle Budding is controlled by coat proteins Coat proteins create vesicle

2、s Once vesicles form, coat proteins dissociate from the vesicle Vesicles are transported along microtubules via motors Tethering proteins link vesicles to acceptor organelles and cause fusion,The Golgi is the cellular sorting station Proteins are synthesized in the ER travel to the Cis-Golgi Protein

3、s travel from the Cis-Golgi to the Medial- Golgi Proteins travel from the Medial-Golgi to the Trans- Golgi From the Trans-Golgi, proteins are secreted or sent to lysosomes or endosomes,COPII vesicles move to the Vesicular Tubular Cluster (VTC) COPI vesicles move from the VTC to the ER, returning lip

4、id COPI vesicles move from the Golgi to the ER, returning lipid,COPI vesicles formed through activation of the Arf1 GTPase by its GEF Arf1 then recruits the Coatomer complex An Arf1 GAP hydrolyses the Arf1 GTP and Arf1 dissociates,COPII vesicles move to the Vesicular Tubular Cluster (WTC) COPI vesic

5、les move from the VTC to the ER, returning lipid COPI vesicles move from the Golgi to the ER, returning lipid,Sorting: different signals on proteins allow them to be sent to different organelles,Secretion is the default route for Golgi proteins (no signals are involved) Golgi vesicles bud into Secre

6、tory Granules (SG) SG condense and mature (acidify and increase Zn2+_,Insulin is synthesized as an inactive form (pro-insulin) Insulin must be modified during the secretion process,iSG=immature secretory granule mSG= mature secretory granule Proinsulin is found in iSG Insulin is found in the mSG,Gol

7、gi to Endosome/Lysosome system -Proteins destined for the Endosome or Lysosome are modified by the addition of a phosphate to a mannose sugar (M6P) -M6P receptors (M6PR) recognize these proteins -M6PR stimulates the assembly of clathrin around the protein and M6PR -Clathrin causes vesicles to form -

8、These vesicles move toe the endosome and the lysosome -Lysosomal proteins get degraded,Proteins have carbohydrate added and removed in the Golgi Specific carbohydrate signals (eg. M6P) signal for transport to specific organelles,Assembly of Clathrin Coated Vesicle M6PR binds to M6P containing protei

9、ns M6PR binds to Adaptin (AP-1) Adaptin recruits Clathrin Clathrin causes bud formation Dynamin causes bud to pinch off from Golgi membrane,Protein transport out of the Golgi is through Clathrin Coated Vesicle,Golgi to Endosome/Lysosome system -Proteins destined for the Endosome or Lysosome are modi

10、fied by the addition of a phosphate to a mannose sugar (M6P) -M6P receptors (M6PR) recognize these proteins -M6PR stimulates the assembly of clathrin around the protein and M6PR -Clathrin causes vesicles to form -These vesicles move toe the endosome and the lysosome -Lysosomal proteins get degraded,

11、Cells are not fully symmetrical, they are polarized Polarized=different composition at different places,Polarization is the net result of different sorting in the Golgi,Cell polarization derives from different transport from the Golgi,Cells bring in outside substances,Clathrin-mediated endocytosis:

12、brings in plasma membrane receptors during endocytosis Phagocytosis: Engulfment and destruction of bacteria,Phagocytosis -Cell recognizes bacterium -Cell engulfs bacterium via cytoskeletal remodeling -Engulfment creates a Phagosome -Phagosome fuses with a lysosome -Lysosome contains digestive enzyme

13、s,Cells bring in outside substances,Clathrin-mediated endocytosis: brings in plasma membrane receptors during endocytosis Phagocytosis: Engulfment and destruction of bacteria,Clathrin-mediated endocytosis: Internalization of plasma membrane receptors Membrane receptor binds AP2 (adaptor protein) AP2

14、 rectuirs clathrin triskeleon Clathrin assembly causes membrane deformation and coated pit formation Amphiphysins and dynamin assemble between the coated pit and membrane (stalk) Dynamin constriction causes vesicle to bud off Auxilin and Hsc70 bind to vesicle and cause clathrin release,Assembly of C

15、lathrin Coated Vesicle M6PR binds to M6P containing proteins M6PR binds to Adaptin (AP-1) Adaptin recruits Clathrin Clathrin causes bud formation Dynamin causes bud to pinch off from Golgi membrane,Clathrin-mediated endocytosis: Internalization of plasma membrane receptors Membrane receptor binds AP

16、2 (adaptor protein) AP2 rectuirs clathrin triskeleon Clathrin assembly causes membrane deformation and coated pit formation Amphiphysins and dynamin assemble between the coated pit and membrane (stalk) Dynamin constriction causes vesicle to bud off Auxilin and Hsc70 bind to vesicle and cause clathrin release,Endocytosed proteins go to either to the lysosome for degradation, back to the Golgi for further modif