title: Solubilization and photoaffinity labeling identification of glucocorticoid binding peptides in endoplasmic reticulum from rat liver.
abstract: Steroid-binding proteins unrelated to the classical nuclear receptors have been proposed to play a role in non-genomic effects of steroid hormones. We have previously described that the low-affinity glucocorticoid binding protein (LAGS), present in the endoplasmic reticulum of the male rat liver, has pharmacological and biochemical properties different from those of nuclear receptors. The LAGS is under multihormonal regulation and binds glucocorticoids, progestins, and synthetic steroids but is unable to bind either estradiol, testosterone, or triamcinolone acetonide. In this study, we have solubilized the LAGS and investigated their pharmacological and hydrodynamic properties and their peptide composition. We found that LAGS is an integral protein bound to the endoplasmic reticulum. CHAPS provided its optimal solubilization without changes in its pharmacological properties. Hydrodynamic properties of LAGS showed that it has a molecular mass of at least 135 kDa. SDS-PAGE of covalently-labeled LAGS showed that [3H]dexamethasone binds two peptides of 53 and 37 kDa, respectively. Thus, the LAGS appears as an oligomeric protein under multihormonal regulation. The availability of solubilized LAGS and the fact that it can be induced in vivo represent major steps toward purification and understanding the functional significance of this unique steroid-binding protein.
authors.affiliation: Pharmacology Section, Department of Clinical Sciences, Health Sciences Center, Instituto Canario de Investigación Sobre el Cáncer (ICIC), University of Las Palmas de Gran Canaria, Dr. Pasteur s/n, Canary Islands, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Pérez-Machín
authors.forename: Luis
authors.initials: L
authors.lastname: Henríquez-Hernández
authors.forename: Octavio
authors.initials: O
authors.lastname: Pérez-Luzardo
authors.forename: Eva
authors.initials: E
authors.lastname: Betancor-Hernández
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Tabares-Domínguez
authors.forename: Carlos
authors.initials: C
authors.lastname: Mateos-Díaz
authors.forename: Javier
authors.initials: J
authors.lastname: Novoa-Mogollón
authors.forename: B N
authors.initials: BN
authors.lastname: Díaz-Chico
authors.forename: Leandro
authors.initials: L
authors.lastname: Fernández
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D003902:Detergents / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism; D008027:Light; D008099:Liver / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D017830:Octoxynol; D010455:Peptides / Q000737:chemistry; D011092:Polyethylene Glycols / Q000494:pharmacology; D011372:Progestins / Q000378:metabolism; D011485:Protein Binding; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013256:Steroids / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013739:Testosterone / Q000378:metabolism; D013997:Time Factors; D014222:Triamcinolone Acetonide / Q000378:metabolism; D014867:Water
chemical_list: D003902:Detergents; D005938:Glucocorticoids; D010455:Peptides; D011372:Progestins; D013256:Steroids; D014867:Water; D011092:Polyethylene Glycols; D013739:Testosterone; D004958:Estradiol; D003907:Dexamethasone; D017830:Octoxynol; C010615:Nonidet P-40; D014222:Triamcinolone Acetonide