Subcellular localization of sigma-2 receptors in breast cancer cells using two-photon and confocal microscopy

Cancer Res. 2007 Jul 15;67(14):6708-16. doi: 10.1158/0008-5472.CAN-06-3803.

Abstract

Sigma-2 receptor agonists have been shown to induce cell death via caspase-dependent and caspase-independent pathways. Unfortunately, there is little information regarding the molecular function of sigma-2 receptors that can explain these results. In this study, two fluorescent probes, SW107 and K05-138, were used to study the subcellular localization of sigma-2 receptors by two-photon and confocal microscopy. The results indicate that sigma-2 receptors colocalize with fluorescent markers of mitochondria, lysosomes, endoplasmic reticulum, and the plasma membrane in both EMT-6 mouse and MDA-MB-435 human breast cancer cells. The fluorescent probe, K05-138, was internalized rapidly, reaching a plateau of fluorescent intensity at 5 min. The internalization of K05-138 was reduced approximately 40% by phenylarsine oxide, an inhibitor of endocytosis. These data suggest that sigma-2 ligands are internalized, in part, by an endocytotic pathway. The localization of sigma-2 receptors in several organelles known to have a role in both caspase-dependent and caspase-independent pathways of cell death supports the conclusions of previous studies suggesting that sigma-2 receptor ligands should be evaluated as potential cancer chemotherapeutic agents.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Arsenicals / chemistry
  • Breast Neoplasms / metabolism*
  • Caspases / metabolism
  • Endocytosis
  • Endoplasmic Reticulum / metabolism
  • Flow Cytometry
  • Fluorescent Dyes / pharmacology
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Kinetics
  • Ligands
  • Microscopy, Confocal
  • Models, Chemical
  • Photons
  • Receptors, sigma / biosynthesis*
  • Receptors, sigma / chemistry

Substances

  • Arsenicals
  • Fluorescent Dyes
  • Ligands
  • Receptors, sigma
  • sigma-2 receptor
  • oxophenylarsine
  • Caspases