title: Cellular uptake of steroid carrier proteins--mechanisms and implications.
abstract: Steroid hormones are believed to enter cells solely by free diffusion through the plasma membrane. However, recent studies suggest the existence of cellular uptake pathways for carrier-bound steroids. Similar to the clearance of cholesterol via lipoproteins, these pathways involve the recognition of carrier proteins by endocytic receptors on the surface of target cells, followed by internalization and cellular delivery of the bound sterols. Here, we discuss the emerging concept that steroid hormones can selectively enter steroidogenic tissues by receptor-mediated endocytosis, and we discuss the implications of these uptake pathways for steroid hormone metabolism and action in vivo.
authors: Max-Delbrück-Center for Molecular Medicine, Berlin, Germany. willnow@mdc-berlin.de
authors: Thomas E
authors: TE
authors: Willnow
authors: Anders
authors: A
authors: Nykjaer
mesh_terms: D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D012739:Gonadal Steroid Hormones / Q000378:metabolism; D006801:Humans; D008074:Lipoproteins / Q000378:metabolism; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013256:Steroids / Q000378:metabolism*; D014807:Vitamin D / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D012739:Gonadal Steroid Hormones; D008074:Lipoproteins; D026561:Low Density Lipoprotein Receptor-Related Protein-2; D011956:Receptors, Cell Surface; D013256:Steroids; D014807:Vitamin D; D002784:Cholesterol