title: Cholesterol transporter caveolin-1 transits the lipid bilayer during intracellular cycling.
abstract: Caveolin-1, a major protein of cell surface invaginations called caveolae, is currently believed to cycle between the plasma membrane and intracellular compartments via the endocytotic pathway, at least for part of its itinerary. We studied the distribution of caveolin-1 in cell membranes, using ultrathin cryosections and freeze-fracture immunolabeling and found this protein not only in the cytoplasmic leaflet of the plasma membrane, but also in the exoplasmic leaflet of all intracellular membranes. This sidedness implies that caveolin-1 switches from one membrane leaflet to the other somewhere on its way through the cell and rules out the classic mechanism of endocytotic membrane budding and fusion for caveolin-1 intracellular trafficking. Underlying the sidedness of caveolin-1 may be a fundamental, hitherto unrecognized, mechanism by which proteins transit membranes.
authors.affiliation: University Children's Hospital, Münster, Germany. robenek@uni-muenster.de
authors.forename: Mirko J
authors.initials: MJ
authors.lastname: Robenek
authors.forename: Karin
authors.initials: K
authors.lastname: Schlattmann
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Zimmer
authors.forename: Gabriele
authors.initials: G
authors.lastname: Plenz
authors.forename: David
authors.initials: D
authors.lastname: Troyer
authors.forename: Horst
authors.initials: H
authors.lastname: Robenek
mesh_terms: D000818:Animals; D051242:Caveolin 1; D022461:Caveolins / Q000032:analysis / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002784:Cholesterol / Q000378:metabolism; D007425:Intracellular Membranes / Q000737:chemistry / Q000648:ultrastructure; D008051:Lipid Bilayers / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000032:analysis / Q000378:metabolism; D008954:Models, Biological; D021381:Protein Transport
chemical_list: D051242:Caveolin 1; D022461:Caveolins; D008051:Lipid Bilayers; D026901:Membrane Transport Proteins; D002784:Cholesterol