Subcellular localization of sigma-2 receptors in breast cancer cells using two-photon and confocal microscopy
Chenbo Zeng1, Suwanna Vangveravong, Jinbin Xu
1Department of Radiology, Division of Radiological Sciences, Washington University School of Medicine, 510 S. Kingshighway Boulevard, St. Louis, MO 63110, USA.
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.
Insights
Sigma-2 receptors are found in multiple cell organelles, including mitochondria and lysosomes. This localization supports their role in cancer cell death pathways and potential use as chemotherapy agents.
Area of Science:
- Cell Biology
- Molecular Pharmacology
- Cancer Research
Background:
- Sigma-2 receptor agonists induce cancer cell death through caspase-dependent and -independent pathways.
- The precise molecular function and localization of sigma-2 receptors remain largely uncharacterized.
- Understanding sigma-2 receptor localization is crucial for elucidating their role in cell death.
Purpose of the Study:
- To investigate the subcellular localization of sigma-2 receptors using fluorescent probes.
- To determine the cellular uptake mechanisms of sigma-2 receptor ligands.
- To provide molecular insights into sigma-2 receptor-mediated cell death.
Main Methods:
- Utilized two-photon and confocal microscopy to visualize sigma-2 receptor localization.
- Employed fluorescent probes SW107 and K05-138 for imaging.
- Investigated ligand internalization using phenylarsine oxide, an endocytosis inhibitor.
Main Results:
- Sigma-2 receptors colocalize with mitochondria, lysosomes, endoplasmic reticulum, and plasma membrane markers in breast cancer cells.
- The fluorescent probe K05-138 showed rapid internalization, reaching a plateau within 5 minutes.
- Phenylarsine oxide reduced K05-138 internalization by approximately 40%, indicating partial endocytosis involvement.
Conclusions:
- Sigma-2 receptors are distributed across multiple subcellular organelles involved in cell death.
- Sigma-2 receptor ligands are internalized, at least partially, via endocytosis.
- The observed localization supports the evaluation of sigma-2 receptor ligands as potential cancer therapeutics.
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