title: σ-1 receptor at the mitochondrial-associated endoplasmic reticulum membrane is responsible for mitochondrial metabolic regulation.
abstract: The mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) is a small section of the outer mitochondrial membrane tethered to the ER by lipid and protein filaments. One such MAM protein is the σ-1 receptor, which contributes to multiple signaling pathways. We found that short interfering RNA-mediated knockdown of σ-1 reduced pregnenolone synthesis by 95% without affecting expression of the inner mitochondrial membrane resident enzyme, 3-β-hydroxysteroid dehydrogenase 2. To explore the underlying mechanism of this effect, we generated a series of σ-receptor ligands: 5,6-dimethoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-1), 3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-5), and 6-methoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl) propyl)benzofuran-2-carboxamide (KSCM-11) specifically bound to σ-1 in the nanomolar range, whereas KSCM-5 and KSCM-11 also bound to σ-2. Treatment of cells with the KSCM ligands led to decreased cell viability, with KSCM-5 having the most potent effect followed by KSCM-11. KSCM-1 increased σ-1 expression by 4-fold and progesterone synthesis, whereas the other compounds decreased progesterone synthesis. These differences probably are caused by ligand molecular structure. For example, KSCM-1 has two methoxy substituents at C-5 and C-6 of the benzofuran ring, whereas KSCM-11 has one at C-6. KSCM ligands or σ-1 knockdown did not alter the expression of ER resident enzymes that synthesize steroids. However, coimmunoprecipitation of the σ-1 receptor pulled down voltage-dependent anion channel 2 (VDAC2), whose expression was enhanced by KSCM-1. VDAC2 plays a key role in cholesterol transport into the mitochondria, suggesting that the σ-1 receptor at the MAM coordinates with steroidogenic acute regulatory protein for cholesterol trafficking into the mitochondria for metabolic regulation.
authors.affiliation: Department of Natural Sciences, College of Science and Technology, Savannah State University, Savannah, GA, USA.
authors.forename: Karla-Sue C
authors.initials: KS
authors.lastname: Marriott
authors.forename: Manoj
authors.initials: M
authors.lastname: Prasad
authors.forename: Veena
authors.initials: V
authors.lastname: Thapliyal
authors.forename: Himangshu S
authors.initials: HS
authors.lastname: Bose
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism; D008024:Ligands; D008297:Male; D051379:Mice; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism*; D015394:Molecular Structure; D010880:Piperidines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011284:Pregnenolone / Q000096:biosynthesis*; D011485:Protein Binding; D017480:Receptors, sigma / Q000235:genetics / Q000378:metabolism*; D000097605:Sigma-1 Receptor
chemical_list: D001572:Benzofurans; D002784:Cholesterol; D008024:Ligands; D010880:Piperidines; D011284:Pregnenolone; D017480:Receptors, sigma; D000097605:Sigma-1 Receptor; C577636:3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide; C577635:5,6-dimethoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide; C577637:6-methoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide