Dynamic equilibrium between vesicular stomatitis virus glycoprotein monomers and trimers in the Golgi and at the cell surface.
Previous studies have shown that trimers of the vesicular stomatitis virus glycoprotein (VSV G protein) are in rapid equilibrium with monomeric subunits after folding and assembly in the endoplasmic reticulum (ER). To determine whether G protein trimers were in equilibrium with monomers in other cellular compartments, we studied heterotrimer formation between VSV G protein and a mutant G protein (G mu protein) containing a 3-amino-acid cytoplasmic domain replacing the normal 29-amino-acid domain. The G mu protein is transported from the ER much more slowly than G protein, although both G and G mu proteins form trimers rapidly in the ER. In coexpression experiments, we observed that VSV G protein molecules exited the ER about sixfold faster than G mu protein molecules, and we observed no heterotrimer formation in the ER, probably because of rapid reassortment of the mutant and wild-type trimers. However, heterotrimer formation between the two proteins was observed after long chase periods that allowed time for trimers of the mutant protein to reach the plasma membrane and reassort with the G protein subunits. Additional studies showed that heterotrimers of the two proteins could form in the Golgi or in the ER if exit of the G protein from either compartment was blocked.
Zagouras
P
P
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510.
Rose
J K
JK
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000918:Antibody Specificity; D001692:Biological Transport; D020126:Brefeldin A; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D003517:Cyclopentanes / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism*; D006596:Hexosaminidases / Q000494:pharmacology; D008562:Membrane Glycoproteins; D009154:Mutation; D004856:Postural Balance; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D014721:Vesicular stomatitis Indiana virus / Q000187:drug effects / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*
D000914:Antibodies, Viral; D003517:Cyclopentanes; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D020126:Brefeldin A; D006596:Hexosaminidases