σ-1 receptor at the mitochondrial-associated endoplasmic reticulum membrane is responsible for mitochondrial metabolic regulation

J Pharmacol Exp Ther. 2012 Dec;343(3):578-86. doi: 10.1124/jpet.112.198168. Epub 2012 Aug 24.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzofurans / chemical synthesis
  • Benzofurans / chemistry
  • Benzofurans / pharmacology*
  • Blotting, Western
  • Cell Line
  • Cholesterol / metabolism*
  • Dose-Response Relationship, Drug
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism*
  • Gene Knockdown Techniques
  • Leydig Cells / drug effects
  • Leydig Cells / metabolism
  • Ligands
  • Male
  • Mice
  • Mitochondrial Membranes / drug effects
  • Mitochondrial Membranes / metabolism*
  • Molecular Structure
  • Piperidines / chemical synthesis
  • Piperidines / chemistry
  • Piperidines / pharmacology*
  • Pregnenolone / biosynthesis*
  • Protein Binding
  • Receptors, sigma / genetics
  • Receptors, sigma / metabolism*
  • Sigma-1 Receptor

Substances

  • 3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide
  • 5,6-dimethoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide
  • 6-methoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide
  • Benzofurans
  • Ligands
  • Piperidines
  • Receptors, sigma
  • Pregnenolone
  • Cholesterol