title: Identification and pharmacological characterization of SRBP-2: a novel SR31747A-binding protein.
abstract: SR31747A is a sigma ligand with potent antiproliferative activity against tumor cells and for which three binding proteins have been identified to date: (a) SRBP-1 (also called sigma 1); (b) HIS; and (c) sigma 2. In this study, we characterized an additional SR31747A binding site, i.e., SRBP-2 (SR31747A-binding protein 2). Using an in silico screening approach, we identified this novel sequence, which exhibits 41% homology with HSI. The 1142-bp cDNA was found to encode a 206 amino acid protein not related to SRBP-1. Northern blot analysis of SRBP-2 mRNA expression revealed a single 1.1-kb transcript that was widely expressed in organs; the liver was particularly enriched, and the brain showed the lowest abundance. A murine homologue that exhibited a similar expression pattern was also characterized. Subcellular localization analysis using specific polyclonal antibodies revealed that SRBP-2 had the same nuclear membrane and endoplasmic reticulum localization as other members of the SR31747A-binding protein family. Considering SRBP-2-binding properties, pharmacological analysis clearly highlighted that SRBP-2 was distinct from sigma 2. Scatchard plot analysis revealed K(d) values of 10 and 3 nM for SR31747A and Tamoxifen, respectively. In contrast with HSI, the protein also did not exhibit detectable isomerase activity. When analyzing SRBP-2 expression in human breast cancer biopsies, we obtained evidence that SRBP-2 expression, together with SRBP-1 and HSI, may be of interest as a prognostic marker. These findings demonstrated that SRBP-2 represents an additional molecular target for SR31747A, which could help to understand the immunosuppressive and antiproliferative effects of the molecule.
authors.affiliation: Immunology-Oncology Department, Sanofi approximately Synthelabo, F-34184 Montpellier cedex 04 , France.
authors.forename: Hubert
authors.initials: H
authors.lastname: Vidal
authors.forename: Guillaume
authors.initials: G
authors.lastname: Mondesert
authors.forename: Sylvaine
authors.initials: S
authors.lastname: Galiègue
authors.forename: Dominique
authors.initials: D
authors.lastname: Carrière
authors.forename: Pascal-Henri
authors.initials: PH
authors.lastname: Dupuy
authors.forename: Pierre
authors.initials: P
authors.lastname: Carayon
authors.forename: Thérèse
authors.initials: T
authors.lastname: Combes
authors.forename: Estelle
authors.initials: E
authors.lastname: Bribes
authors.forename: Joëlle
authors.initials: J
authors.lastname: Simony-Lafontaine
authors.forename: Andrew
authors.initials: A
authors.lastname: Kramar
authors.forename: Gérard
authors.initials: G
authors.lastname: Loison
authors.forename: Pierre
authors.initials: P
authors.lastname: Casellas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D002352:Carrier Proteins / Q000032:analysis* / Q000235:genetics / Q000494:pharmacology; D005260:Female; D006801:Humans; D017403:In Situ Hybridization; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D008969:Molecular Sequence Data; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D011957:Receptors, Opioid; D017480:Receptors, sigma; D013251:Steroid Isomerases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000097605:Sigma-1 Receptor
chemical_list: D002352:Carrier Proteins; D012333:RNA, Messenger; D011957:Receptors, Opioid; D017480:Receptors, sigma; D013251:Steroid Isomerases; D000097605:Sigma-1 Receptor