1
|
Mavlyutov TA, Yang H, Epstein ML, Ruoho AE, Yang J, Guo LW. APEX2-enhanced electron microscopy distinguishes sigma-1 receptor localization in the nucleoplasmic reticulum. Oncotarget 2017; 8:51317-51330. [PMID: 28881650 PMCID: PMC5584251 DOI: 10.18632/oncotarget.17906] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 05/04/2017] [Indexed: 12/03/2022] Open
Abstract
The sigma-1 receptor (Sig1R) is an endoplasmic reticulum chaperonin that is attracting tremendous interest as a potential anti-neurodegenerative target. While this membrane protein is known to reside in the inner nuclear envelope (NE) and influences transcription, apparent Sig1R presence in the nucleoplasm is often observed, seemingly contradicting its NE localization. We addressed this confounding issue by applying an antibody-free approach of electron microscopy (EM) to define Sig1R nuclear localization. We expressed APEX2 peroxidase fused to Sig1R-GFP in a Sig1R-null NSC34 neuronal cell line generated with CRISPR-Cas9. APEX2-catalyzed gold/silver precipitation markedly improved EM clarity and confirmed an apparent intra-nuclear presence of Sig1R. However, serial sectioning combined with APEX2-enhanced EM revealed that Sig1R actually resided in the nucleoplasmic reticulum (NR), a specialized nuclear compartment formed via NE invagination into the nucleoplasm. NR cross-sections also indicated Sig1R in ring-shaped NR membranes. Thus, this study distinguishes Sig1R in the NR which could otherwise appear localized in the nucleoplasm if detected with low-resolution methods. Our finding is important for uncovering potential Sig1R regulations in the nucleus.
Collapse
Affiliation(s)
- Timur A Mavlyutov
- Department of Surgery, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, WI 53705, USA
| | - Huan Yang
- Department of Surgery, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, WI 53705, USA
| | - Miles L Epstein
- Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA
| | - Arnold E Ruoho
- Department of Neuroscience, University of Wisconsin, Madison, WI 53706, USA
| | - Jay Yang
- Department of Anesthesiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, WI 53705, USA
| | - Lian-Wang Guo
- Department of Surgery, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, WI 53705, USA.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI 53705, USA.,Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.,Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| |
Collapse
|