title: Few things in life are "free": cellular uptake of steroid hormones by an active transport mechanism.
abstract: Conventional dogma holds that steroid hormones traverse cell membranes passively, owing to their lipophilic nature. The recently characterized protein megalin, however, functions as a transport protein on cell surfaces to carry steroids across the plasma membrane. Upon hydrolysis of steroid-associated binding globulins in lysosomes, free hormone is liberated and may exert its effects in the cell. Megalin-independent mechanisms of steroid uptake are likely important too, as the phenotypes of megalin-deficient mice do not completely mimic the phenotypes of androgen receptor- or estrogen receptor-null mice.
authors.affiliation: Departments of Pharmaceutical Chemistry and Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143-2280, USA.
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Lin
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Scanlan
mesh_terms: D000728:Androgens / Q000502:physiology*; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D004967:Estrogens / Q000502:physiology*; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000502:physiology*; D051379:Mice
chemical_list: D000728:Androgens; D004967:Estrogens; D026561:Low Density Lipoprotein Receptor-Related Protein-2