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

Karla-Sue C Marriott1, Manoj Prasad, Veena Thapliyal

  • 1Department of Natural Sciences, College of Science and Technology, Savannah State University, Savannah, GA, USA.

The Journal of Pharmacology and Experimental Therapeutics
|August 28, 2012
PubMed

Insights

The σ-1 receptor at the mitochondria-associated ER membrane (MAM) regulates steroid synthesis. New ligands reveal its role in cholesterol transport and metabolic regulation.

Area of Science:

  • Cell Biology
  • Neuroscience
  • Endocrinology

Background:

  • The mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) is crucial for cellular signaling and lipid metabolism.
  • The σ-1 receptor is a MAM protein involved in various signaling pathways, including steroidogenesis.
  • Understanding the σ-1 receptor's function in steroid synthesis requires investigating its interactions and regulatory mechanisms.

Purpose of the Study:

  • To elucidate the role of the σ-1 receptor in regulating pregnenolone and progesterone synthesis.
  • To explore the mechanism by which σ-1 receptor ligands affect steroidogenic pathways.
  • To investigate the interaction of the σ-1 receptor with other proteins involved in mitochondrial cholesterol transport.

Main Methods:

  • Short interfering RNA (siRNA) was used to knock down σ-1 receptor expression.
  • Novel σ-1 receptor ligands (KSCM-1, KSCM-5, KSCM-11) were synthesized and characterized for binding affinity.
  • Cell viability assays, steroid synthesis measurements, coimmunoprecipitation, and Western blotting were performed.

Main Results:

  • Knockdown of σ-1 receptor significantly reduced pregnenolone synthesis by 95%.
  • KSCM ligands exhibited differential effects on σ-1 receptor expression, cell viability, and progesterone synthesis.
  • KSCM-1 increased σ-1 receptor expression and progesterone synthesis, while KSCM-5 and KSCM-11 decreased progesterone synthesis and cell viability.
  • The σ-1 receptor was found to coimmunoprecipitate with voltage-dependent anion channel 2 (VDAC2), an essential protein for mitochondrial cholesterol transport.

Conclusions:

  • The σ-1 receptor plays a critical role in regulating steroidogenesis, particularly pregnenolone synthesis.
  • σ-1 receptor ligands can modulate steroid synthesis and cell viability through distinct mechanisms.
  • The σ-1 receptor at the MAM likely coordinates with VDAC2 and steroidogenic acute regulatory protein to regulate cholesterol transport into mitochondria for steroid metabolic regulation.

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