Identification of the PGRMC1 protein complex as the putative sigma-2 receptor binding site

• Published in: Nature communications Vol. 2; no. 1; p. 380
• Main Authors: Xu, Jinbin, Zeng, Chenbo, Chu, Wenhua, Pan, Fenghui, Rothfuss, Justin M, Zhang, Fanjie, Tu, Zhude, Zhou, Dong, Zeng, Dexing, Vangveravong, Suwanna, Johnston, Fabian, Spitzer, Dirk, Chang, Katherine C, Hotchkiss, Richard S, Hawkins, William G, Wheeler, Kenneth T, Mach, Robert H
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 05.07.2011
• Subjects: Animals; Binding sites; Biomarkers; Breast cancer; Cell growth; Cloning; Cytochrome; Fluorescence; Gene Knockdown Techniques; HeLa Cells; Humans; Immunohistochemistry; Ligands; Medicine; Membrane Proteins - genetics; Membrane Proteins - metabolism; Molecular Structure; Multiprotein Complexes - metabolism; Photoaffinity Labels - metabolism; Proteins; Rats; Receptors, Progesterone - genetics; Receptors, Progesterone - metabolism; Receptors, sigma - metabolism; Tumors; United States > US; Missouri
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms1386

The sigma-2 receptor, whose gene remains to be cloned, has been validated as a biomarker for tumour cell proliferation. Here we report the use of a novel photoaffinity probe, WC-21, to identify the sigma-2 receptor-binding site. WC-21, a sigma-2 ligand containing both a photoactive azide moiety and a fluorescein isothiocyanate group, irreversibly labels sigma-2 receptors in rat liver; the membrane-bound protein was identified as PGRMC1 (progesterone receptor membrane component 1). Immunocytochemistry reveals that both PGRMC1 and SW120, a fluorescent sigma-2 receptor ligand, colocalize with molecular markers of the endoplasmic reticulum and mitochondria in HeLa cells. Overexpression and knockdown of the PGRMC1 protein results in an increase and a decrease in binding of a sigma-2 selective radioligand, respectively. The identification of the putative sigma-2 receptor-binding site as PGRMC1 should stimulate the development of unique imaging agents and cancer therapeutics that target the sigma-2 receptor/PGRMC1 complex.