title: Subcellular localization of sigma-2 receptors in breast cancer cells using two-photon and confocal microscopy.
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.
authors.affiliation: Department of Radiology, Division of Radiological Sciences, Washington University School of Medicine, 510 S. Kingshighway Boulevard, St. Louis, MO 63110, USA.
authors.forename: Chenbo
authors.initials: C
authors.lastname: Zeng
authors.forename: Suwanna
authors.initials: S
authors.lastname: Vangveravong
authors.forename: Jinbin
authors.initials: J
authors.lastname: Xu
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Chang
authors.forename: Richard S
authors.initials: RS
authors.lastname: Hotchkiss
authors.forename: Kenneth T
authors.initials: KT
authors.lastname: Wheeler
authors.forename: Duanwen
authors.initials: D
authors.lastname: Shen
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Zhuang
authors.forename: Hank F
authors.initials: HF
authors.lastname: Kung
authors.forename: Robert H
authors.initials: RH
authors.lastname: Mach
mesh_terms: D001152:Arsenicals / Q000737:chemistry; D001943:Breast Neoplasms / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007700:Kinetics; D008024:Ligands; D018613:Microscopy, Confocal; D008956:Models, Chemical; D017785:Photons; D017480:Receptors, sigma / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D001152:Arsenicals; D005456:Fluorescent Dyes; D008024:Ligands; D017480:Receptors, sigma; C106107:sigma-2 receptor; C029341:oxophenylarsine; D020169:Caspases