title: The Sigma-2 Receptor and Progesterone Receptor Membrane Component 1 are Different Binding Sites Derived From Independent Genes.
abstract: The sigma-2 receptor (S2R) is a potential therapeutic target for cancer and neuronal diseases. However, the identity of the S2R has remained a matter of debate. Historically, the S2R has been defined as (1) a binding site with high affinity to 1,3-di-o-tolylguanidine (DTG) and haloperidol but not to the selective sigma-1 receptor ligand (+)-pentazocine, and (2) a protein of 18-21 kDa, as shown by specific photolabeling with [(3)H]-Azido-DTG and [(125)I]-iodoazido-fenpropimorph ([(125)I]-IAF). Recently, the progesterone receptor membrane component 1 (PGRMC1), a 25 kDa protein, was reported to be the S2R (Nature Communications, 2011, 2:380). To confirm this identification, we created PGRMC1 knockout NSC34 cell lines using the CRISPR/Cas9 technology. We found that in NSC34 cells devoid of or overexpressing PGRMC1, the maximum [(3)H]-DTG binding to the S2R (Bmax) as well as the DTG-protectable [(125)I]-IAF photolabeling of the S2R were similar to those of wild-type control cells. Furthermore, the affinities of DTG and haloperidol for PGRMC1 (KI = 472 μM and 350 μM, respectively), as determined in competition with [(3)H]-progesterone, were more than 3 orders of magnitude lower than those reported for the S2R (20-80 nM). These results clarify that PGRMC1 and the S2R are distinct binding sites expressed by different genes.
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Uyen B
authors: UB
authors: Chu
authors: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Timur A
authors: TA
authors: Mavlyutov
authors: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Ming-Liang
authors: ML
authors: Chu
authors: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Huan
authors: H
authors: Yang
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Amanda
authors: A
authors: Schulman
authors: Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, United States.
authors: Christophe
authors: C
authors: Mesangeau
authors: Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, United States.
authors: Christopher R
authors: CR
authors: McCurdy
authors: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States; McPherson Eye Research Institute, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Lian-Wang
authors: LW
authors: Guo
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.
authors: Arnold E
authors: AE
authors: Ruoho
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D015870:Gene Expression; D055786:Gene Knockout Techniques; D023061:Gene Order; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011374:Progesterone / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D011980:Receptors, Progesterone / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017480:Receptors, sigma / Q000235:genetics* / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; C115296:PGRMC1 protein, human; D011980:Receptors, Progesterone; D017480:Receptors, sigma; C106107:sigma-2 receptor; D011374:Progesterone
keywords: Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 knockout; Progesterone receptor membrane component-1 (PGRMC1); Sigma-2 receptor (S2R); [125I]-Iodoazido-fenpropimorph ([125I]-IAF); [3H]-1,3-Di-o-tolylguanidine ([3H]-DTG)