Intracellular dynamics of the Sigma-1 receptor observed with super-resolution imaging microscopy

PLoS One. 2022 May 18;17(5):e0268563. doi: 10.1371/journal.pone.0268563. eCollection 2022.

Abstract

Sigma-1 receptor (Sig1R) is an endoplasmic reticulum (ER)-related membrane protein, that forms heteromers with other cellular proteins. As the mechanism of action of this chaperone protein remains unclear, the aim of the present study was to detect and analyze the intracellular dynamics of Sig1R in live cells using super-resolution imaging microscopy. For that, the Sig1R-yellow fluorescent protein conjugate (Sig1R-YFP) together with fluorescent markers of cell organelles were transfected into human ovarian adenocarcinoma (SK-OV-3) cells with BacMam technology. Sig1R-YFP was found to be located mainly in the nuclear envelope and in both tubular and vesicular structures of the ER but was not detected in the plasma membrane, even after activation of Sig1R with agonists. The super-resolution radial fluctuations approach (SRRF) performed with a highly inclined and laminated optical sheet (HILO) fluorescence microscope indicated substantial overlap of Sig1R-YFP spots with KDEL-mRFP, slight overlap with pmKate2-mito and no overlap with the markers of endosomes, peroxisomes, lysosomes, or caveolae. Activation of Sig1R with (+)-pentazocine caused a time-dependent decrease in the overlap between Sig1R-YFP and KDEL-mRFP, indicating that the activation of Sig1R decreases its colocalization with the marker of vesicular ER and does not cause comprehensive translocations of Sig1R in cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Microscopy*
  • Pentazocine
  • Receptors, sigma* / metabolism
  • Sigma-1 Receptor

Substances

  • Receptors, sigma
  • Pentazocine

Grants and funding

SV- Estonian Research Council grant (PSG230) EV- European Regional Development Fund Project No. 1.1.1.2/VIAA/2/18/376 "Sigma chaperone protein as a novel drug target" AR, EV - COST action CA 18133 ERNEST. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.