title: Release of soluble resident as well as secretory proteins from HepG2 cells by partial permeabilization of rough-endoplasmic-reticulum membranes.
abstract: Secretory proteins migrate from the rough endoplasmic reticulum (ER) to the Golgi complex at different rates. Selective retention of specific proteins to rough-ER membrane constituents could explain this phenomenon. We have permeabilized HepG2 cells with low concentrations of saponin. Release of newly synthesized proteins was studied after brief labelling in the presence of [35S]methionine. The efflux of several secretory proteins was studied at various saponin concentrations; a 2-fold higher saponin concentration was required to release transferrin compared with that required to release albumin and orosomucoid. Glucosidase II, a soluble resident protein of the ER, is released at the same saponin concentration as albumin. Saponin did not destroy the membrane skeleton structure; at the concentrations used, the integral membrane protein G of vesicular-stomatitis virus remained fully associated with the cells.
authors.affiliation: Laboratory of Cell Biology, University of Utrecht, Medical School, The Netherlands.
authors.forename: G J
authors.initials: GJ
authors.lastname: Strous
authors.forename: P
authors.initials: P
authors.lastname: Van Kerkhof
mesh_terms: D000418:Albumins / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism* / Q000648:ultrastructure; D009363:Neoplasm Proteins / Q000378:metabolism*; D010539:Permeability; D012503:Saponins / Q000494:pharmacology; D012995:Solubility; D014168:Transferrin / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
chemical_list: D000418:Albumins; D009363:Neoplasm Proteins; D012503:Saponins; D014168:Transferrin