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VIP21-Caveolin, a membrane protein constituent of the caveolar coat, oligomerizes in vivo and in vitro

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Item Type:Article
Title:VIP21-Caveolin, a membrane protein constituent of the caveolar coat, oligomerizes in vivo and in vitro
Creators Name:Monier, S. and Parton, R.G. and Vogel, F. and Behlke, J. and Henske, A. and Kurzchalia, T.V.
Abstract:VIP21-caveolin is a membrane protein, proposed to be a component of the striated coat covering the cytoplasmic surface of caveolae. To investigate the biochemical composition of the caveolar coat, we used our previous observation that VIP21-caveolin is present in large complexes and insoluble in the detergents CHAPS or Triton X-114. The mild treatment of these insoluble structures with sodium dodecyl sulfate leads to the detection of high molecular mass complexes of approximately 200, 400, and 600 kDa. The 400-kDa complex purified to homogeneity from dog lung is shown to consist exclusive of the two isoforms of VIP21-caveolin. Pulse-chase experiments indicate that the oligomers form early after the protein is synthesized in the endoplasmic reticulum (ER). VIP21-caveolin does indeed insert into the ER membrane through the classical translocation machinery. Its hydrophobic domain adopts an unusual loop configuration exposing the N- and C-flanking regions to the cytoplasm. Similar high molecular mass complexes can be produced from the in vitro-synthesized VIP21-caveolin. The complex formation occurs only if VIP21-caveolin isoforms are properly inserted into the membrane; formation is cytosol-dependent and does not involve a vesicle fusion step. We propose that high molecular mass oligomers of VIP21-caveolin represent the basic units forming the caveolar coat. They are formed in the ER and later, between the ER and the plasma membrane, these oligomers could associate into larger detergent-insoluble structures.
Keywords:Carrier Proteins, Caveolin 1, Caveolins, Cell Membrane, Cholic Acids, Cultured Cells, Detergents, Endoplasmic Reticulum, Kidney, Lung, Membrane Fusion, Membrane Proteins, Microsomes, Molecular Weight, Polyethylene Glycols, Post-Translational Protein Processing, Protein Conformation, Protein Sorting Signals, Sodium Dodecyl Sulfate, Solubility, Animals, Dogs
Source:Molecular Biology of the Cell
Publisher:American Society for Cell Biology
Page Range:911-927
Date:July 1995
Additional Information:Copyright (c) 1995 by The American Society for Cell Biology
Official Publication:http://www.molbiolcell.org/cgi/content/abstract/6/7/911
PubMed:View item in PubMed

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