title: Cholesterol loading induces a block in the exit of VSVG from the TGN.
abstract: Recent work from our laboratory demonstrated that increased cellular cholesterol content affects the structure of the Golgi apparatus. We have now investigated the functional consequences of the cholesterol-induced vesiculation of the Golgi apparatus and the role of actin for these changes. The results showed that cholesterol-induced vesiculation and dispersion of the Golgi apparatus is a reversible process and that reversal can be inhibited by cytochalasin D, an actin-disrupting reagent. Furthermore, electron microscopy revealed that jasplakinolide, which stabilizes actin filaments, prevented the dispersion, but not the vesiculation of the Golgi cisternae. Importantly, the different Golgi markers seemed to be separated even after vesiculation. To investigate whether transport through the different steps of the exocytic pathway was affected in cholesterol-treated cells, we visualized ER to plasma membrane transport by using ts045-VSVG-GFP. In COS-1 cells expressing ts045-VSVG-GFP increased cholesterol levels did not affect transport of VSVG into the vesiculated Golgi apparatus. However, increased levels of cholesterol resulted in retention of the nascent G protein in vesicles with the TGN-marker TGN46. Biotinylation of cell surface molecules to quantify arrival of VSVG at the plasma membrane confirmed that cholesterol treatment inhibited export of the VSVG protein. In conclusion, the data show that transport of VSVG into/through a vesiculated Golgi is feasible, but that cholesterol loading inhibits exit of VSVG from the vesicles containing TGN markers. Furthermore, the data illustrate the importance of actin filaments for Golgi structure.
authors: Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway.
authors: Ming
authors: M
authors: Ying
authors: Stine
authors: S
authors: Grimmer
authors: Tore-Geir
authors: TG
authors: Iversen
authors: Bo
authors: B
authors: Van Deurs
authors: Kirsten
authors: K
authors: Sandvig
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D015415:Biomarkers; D019921:Biotinylation; D019556:COS Cells; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D003505:Cyclodextrins / Q000737:chemistry / Q000378:metabolism; D047630:Depsipeptides; D005089:Exocytosis / Q000502:physiology*; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism*; D047392:beta-Cyclodextrins; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000199:Actins; D000970:Antineoplastic Agents; D015415:Biomarkers; D003505:Cyclodextrins; D047630:Depsipeptides; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D010456:Peptides, Cyclic; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C057531:jasplakinolide; D002784:Cholesterol