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Couly S, Yasui Y, Foncham S, Grammatikakis I, Lal A, Shi L, Su TP. Benzomorphan and non-benzomorphan agonists differentially alter sigma-1 receptor quaternary structure, as does types of cellular stress. Cell Mol Life Sci 2024; 81:14. [PMID: 38191696 PMCID: PMC10774196 DOI: 10.1007/s00018-023-05023-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/20/2023] [Accepted: 10/26/2023] [Indexed: 01/10/2024]
Abstract
Sigma-1 receptor (S1R) is a calcium-sensitive, ligand-operated receptor chaperone present on the endoplasmic reticulum (ER) membrane. S1R plays an important role in ER-mitochondrial inter-organelle calcium signaling and cell survival. S1R and its agonists confer resilience against various neurodegenerative diseases; however, the molecular mechanism of S1R is not yet fully understood. At resting state, S1R is either in a monomeric or oligomeric state but the ratio of these concentrations seems to change upon activation of S1R. S1R is activated by either cellular stress, such as ER-calcium depletion, or ligands. While the effect of ligands on S1R quaternary structure remains unclear, the effect of cellular stress has not been studied. In this study we utilize cellular and an in-vivo model to study changes in quaternary structure of S1R upon activation. We incubated cells with cellular stressors (H2O2 and thapsigargin) or exogenous ligands, then quantified monomeric and oligomeric forms. We observed that benzomorphan-based S1R agonists induce monomerization of S1R and decrease oligomerization, which was confirmed in the liver tissue of mice injected with (+)-Pentazocine. Antagonists block this effect but do not induce any changes when used alone. Oxidative stress (H2O2) increases the monomeric/oligomeric S1R ratio whereas ER calcium depletion (thapsigargin) has no effect. We also analyzed the oligomerization ability of various truncated S1R fragments and identified the fragments favorizing oligomerization. In this publication we demonstrate that quaternary structural changes differ according to the mechanism of S1R activation. Therefore, we offer a novel perspective on S1R activation as a nuanced phenomenon dependent on the type of stimulus.
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Affiliation(s)
- Simon Couly
- Cellular Pathobiology Section, Integrative Neuroscience Research Branch, Intramural Research Program, National Institute On Drug Abuse, NIH/DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA
| | - Yuko Yasui
- Cellular Pathobiology Section, Integrative Neuroscience Research Branch, Intramural Research Program, National Institute On Drug Abuse, NIH/DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA
| | - Semnyonga Foncham
- Cellular Pathobiology Section, Integrative Neuroscience Research Branch, Intramural Research Program, National Institute On Drug Abuse, NIH/DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA
| | - Ioannis Grammatikakis
- Regulatory RNAs and Cancer Section, Genetics Branch, Center for Cancer Research (CCR), National Cancer Institute (NCI), Bethesda, MD, 20892, USA
| | - Ashish Lal
- Regulatory RNAs and Cancer Section, Genetics Branch, Center for Cancer Research (CCR), National Cancer Institute (NCI), Bethesda, MD, 20892, USA
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, Molecular Targets and Medications Discovery Branch, National Institute On Drug Abuse, NIH/DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA
| | - Tsung-Ping Su
- Cellular Pathobiology Section, Integrative Neuroscience Research Branch, Intramural Research Program, National Institute On Drug Abuse, NIH/DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA.
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Kim M, Bezprozvanny I. Structure-Based Modeling of Sigma 1 Receptor Interactions with Ligands and Cholesterol and Implications for Its Biological Function. Int J Mol Sci 2023; 24:12980. [PMID: 37629160 PMCID: PMC10455549 DOI: 10.3390/ijms241612980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/15/2023] [Accepted: 08/17/2023] [Indexed: 08/27/2023] Open
Abstract
The sigma 1 receptor (S1R) is a 223-amino-acid-long transmembrane endoplasmic reticulum (ER) protein. The S1R plays an important role in neuronal health and it is an established therapeutic target for neurodegenerative and neuropsychiatric disorders. Despite its importance in physiology and disease, the biological function of S1R is poorly understood. To gain insight into the biological and signaling functions of S1R, we took advantage of recently reported crystal structures of human and Xenopus S1Rs and performed structural modeling of S1R interactions with ligands and cholesterol in the presence of the membrane. By combining bioinformatics analysis of S1R sequence and structural modelling approaches, we proposed a model that suggests that S1R may exist in two distinct conformations-"dynamic monomer" (DM) and "anchored monomer" (AM). We further propose that equilibrium between AM and DM conformations of S1R is essential for its biological function in cells, with AM conformation facilitating the oligomerization of S1R and DM conformation facilitating deoligomerization. Consistent with experimental evidence, our hypothesis predicts that increased levels of membrane cholesterol and S1R antagonists should promote the oligomeric state of S1R, but S1R agonists and pathogenic mutations should promote its deoligomerization. Obtained results provide mechanistic insights into signaling functions of S1R in cells, and the proposed model may help to explain neuroprotective effects of S1R modulators.
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Affiliation(s)
- Meewhi Kim
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Ilya Bezprozvanny
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
- Laboratory of Molecular Neurodegeneration, Peter the Great St Petersburg State Polytechnical University, 195251 St. Petersburg, Russia
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3
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Li J, Satyshur KA, Guo LW, Ruoho AE. Sphingoid Bases Regulate the Sigma-1 Receptor-Sphingosine and N, N'-Dimethylsphingosine Are Endogenous Agonists. Int J Mol Sci 2023; 24:3103. [PMID: 36834510 PMCID: PMC9962145 DOI: 10.3390/ijms24043103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/28/2023] [Accepted: 02/01/2023] [Indexed: 02/09/2023] Open
Abstract
Both bioactive sphingolipids and Sigma-1 receptor (S1R) chaperones occur ubiquitously in mammalian cell membranes. Endogenous compounds that regulate the S1R are important for controlling S1R responses to cellular stress. Herein, we interrogated the S1R in intact Retinal Pigment Epithelial cells (ARPE-19) with the bioactive sphingoid base, sphingosine (SPH), or the pain-provoking dimethylated SPH derivative, N,N'-dimethylsphingosine (DMS). As informed by a modified native gel approach, the basal and antagonist (BD-1047)-stabilized S1R oligomers dissociated to protomeric forms in the presence of SPH or DMS (PRE-084 as control). We, thus, posited that SPH and DMS are endogenous S1R agonists. Consistently, in silico docking of SPH and DMS to the S1R protomer showed strong associations with Asp126 and Glu172 in the cupin beta barrel and extensive van der Waals interactions of the C18 alkyl chains with the binding site including residues in helices 4 and 5. Mean docking free energies were 8.73-8.93 kcal/mol for SPH and 8.56-8.15 kcal/mol for DMS, and calculated binding constants were ~40 nM for SPH and ~120 nM for DMS. We hypothesize that SPH, DMS, and similar sphingoid bases access the S1R beta barrel via a membrane bilayer pathway. We further propose that the enzymatic control of ceramide concentrations in intracellular membranes as the primary sources of SPH dictates availability of endogenous SPH and DMS to the S1R and the subsequent control of S1R activity within the same cell and/or in cellular environments.
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Affiliation(s)
- Jing Li
- Department of Surgery, School of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | - Kenneth A. Satyshur
- Small Molecule Screening Facility, Carbone Cancer Center, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA
| | - Lian-Wang Guo
- Department of Surgery, School of Medicine, University of Virginia, Charlottesville, VA 22908, USA
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA
| | - Arnold E. Ruoho
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53705, USA
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4
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Chaperone-Dependent Mechanisms as a Pharmacological Target for Neuroprotection. Int J Mol Sci 2023; 24:ijms24010823. [PMID: 36614266 PMCID: PMC9820882 DOI: 10.3390/ijms24010823] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/26/2022] [Accepted: 12/27/2022] [Indexed: 01/05/2023] Open
Abstract
Modern pharmacotherapy of neurodegenerative diseases is predominantly symptomatic and does not allow vicious circles causing disease development to break. Protein misfolding is considered the most important pathogenetic factor of neurodegenerative diseases. Physiological mechanisms related to the function of chaperones, which contribute to the restoration of native conformation of functionally important proteins, evolved evolutionarily. These mechanisms can be considered promising for pharmacological regulation. Therefore, the aim of this review was to analyze the mechanisms of endoplasmic reticulum stress (ER stress) and unfolded protein response (UPR) in the pathogenesis of neurodegenerative diseases. Data on BiP and Sigma1R chaperones in clinical and experimental studies of Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease are presented. The possibility of neuroprotective effect dependent on Sigma1R ligand activation in these diseases is also demonstrated. The interaction between Sigma1R and BiP-associated signaling in the neuroprotection is discussed. The performed analysis suggests the feasibility of pharmacological regulation of chaperone function, possibility of ligand activation of Sigma1R in order to achieve a neuroprotective effect, and the need for further studies of the conjugation of cellular mechanisms controlled by Sigma1R and BiP chaperones.
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Kopanchuk S, Vavers E, Veiksina S, Ligi K, Zvejniece L, Dambrova M, Rinken A. Intracellular dynamics of the Sigma-1 receptor observed with super-resolution imaging microscopy. PLoS One 2022; 17:e0268563. [PMID: 35584184 PMCID: PMC9116656 DOI: 10.1371/journal.pone.0268563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 05/03/2022] [Indexed: 12/05/2022] Open
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.
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Affiliation(s)
| | - Edijs Vavers
- Latvian Institute of Organic Synthesis, Riga, Latvia
- Riga Stradins University, Riga, Latvia
| | - Santa Veiksina
- University of Tartu, Institute of Chemistry, Tartu, Estonia
| | - Kadri Ligi
- University of Tartu, Institute of Chemistry, Tartu, Estonia
| | | | - Maija Dambrova
- Latvian Institute of Organic Synthesis, Riga, Latvia
- Riga Stradins University, Riga, Latvia
| | - Ago Rinken
- University of Tartu, Institute of Chemistry, Tartu, Estonia
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6
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Sharma N, Patel C, Shenkman M, Kessel A, Ben-Tal N, Lederkremer GZ. The Sigma-1 receptor is an ER-localized type II membrane protein. J Biol Chem 2021; 297:101299. [PMID: 34648767 PMCID: PMC8561001 DOI: 10.1016/j.jbc.2021.101299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/06/2021] [Accepted: 10/06/2021] [Indexed: 11/10/2022] Open
Abstract
The Sigma-1 receptor (S1R) is a transmembrane protein with important roles in cellular homeostasis in normal physiology and in disease. Especially in neurodegenerative diseases, S1R activation has been shown to provide neuroprotection by modulating calcium signaling, mitochondrial function and reducing endoplasmic reticulum (ER) stress. S1R missense mutations are one of the causes of the neurodegenerative Amyotrophic Lateral Sclerosis and distal hereditary motor neuronopathies. Although the S1R has been studied intensively, basic aspects remain controversial, such as S1R topology and whether it reaches the plasma membrane. To address these questions, we have undertaken several approaches. C-terminal tagging with a small biotin-acceptor peptide and BirA biotinylation in cells suggested a type II membrane orientation (cytosolic N-terminus). However, N-terminal tagging gave an equal probability for both possible orientations. This might explain conflicting reports in the literature, as tags may affect the protein topology. Therefore, we studied untagged S1R using a protease protection assay and a glycosylation mapping approach, introducing N-glycosylation sites. Both methods provided unambiguous results showing that the S1R is a type II membrane protein with a short cytosolic N-terminal tail. Assessments of glycan processing, surface fluorescence-activated cell sorting, and cell surface biotinylation indicated ER retention, with insignificant exit to the plasma membrane, in the absence or presence of S1R agonists or of ER stress. These findings may have important implications for S1R-based therapeutic approaches.
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Affiliation(s)
- Neeraj Sharma
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Chaitanya Patel
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Marina Shenkman
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Amit Kessel
- School of Neurobiology, Biochemistry and Biophysics, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Nir Ben-Tal
- School of Neurobiology, Biochemistry and Biophysics, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Gerardo Z Lederkremer
- The Shmunis School of Biomedicine and Cancer Research, Cell Biology Division, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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7
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Zhemkov V, Ditlev JA, Lee WR, Wilson M, Liou J, Rosen MK, Bezprozvanny I. The role of sigma 1 receptor in organization of endoplasmic reticulum signaling microdomains. eLife 2021; 10:e65192. [PMID: 33973848 PMCID: PMC8112866 DOI: 10.7554/elife.65192] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/29/2021] [Indexed: 12/12/2022] Open
Abstract
Sigma 1 receptor (S1R) is a 223-amino-acid-long transmembrane endoplasmic reticulum (ER) protein. S1R modulates activity of multiple effector proteins and is a well-established drug target. However, signaling functions of S1R in cells are poorly understood. Here, we test the hypothesis that biological activity of S1R in cells can be explained by its ability to interact with cholesterol and to form cholesterol-enriched microdomains in the ER membrane. By performing experiments in reduced reconstitution systems, we demonstrate direct effects of cholesterol on S1R clustering. We identify a novel cholesterol-binding motif in the transmembrane region of human S1R. Mutations of this motif impair association of recombinant S1R with cholesterol beads, affect S1R clustering in vitro and disrupt S1R subcellular localization. We demonstrate that S1R-induced membrane microdomains have increased local membrane thickness and that increased local cholesterol concentration and/or membrane thickness in these microdomains can modulate signaling of inositol-requiring enzyme 1α in the ER. Further, S1R agonists cause disruption of S1R clusters, suggesting that biological activity of S1R agonists is linked to remodeling of ER membrane microdomains. Our results provide novel insights into S1R-mediated signaling mechanisms in cells.
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Affiliation(s)
- Vladimir Zhemkov
- Department of Physiology, UT Southwestern Medical Center at DallasDallasUnited States
| | - Jonathon A Ditlev
- Department of Biophysics, Howard Hughes Medical Institute, UT Southwestern Medical Center at DallasDallasUnited States
| | - Wan-Ru Lee
- Department of Physiology, UT Southwestern Medical Center at DallasDallasUnited States
| | - Mikaela Wilson
- Department of Physiology, UT Southwestern Medical Center at DallasDallasUnited States
| | - Jen Liou
- Department of Physiology, UT Southwestern Medical Center at DallasDallasUnited States
| | - Michael K Rosen
- Department of Biophysics, Howard Hughes Medical Institute, UT Southwestern Medical Center at DallasDallasUnited States
| | - Ilya Bezprozvanny
- Department of Physiology, UT Southwestern Medical Center at DallasDallasUnited States
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic UniversitySt. PetersburgRussian Federation
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8
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Shinoda Y, Haga Y, Akagawa K, Fukunaga K. Wildtype σ1 receptor and the receptor agonist improve ALS-associated mutation-induced insolubility and toxicity. J Biol Chem 2020; 295:17573-17587. [PMID: 33453999 PMCID: PMC7762949 DOI: 10.1074/jbc.ra120.015012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 10/10/2020] [Indexed: 12/12/2022] Open
Abstract
Genetic mutations related to ALS, a progressive neurological disease, have been discovered in the gene encoding σ-1 receptor (σ1R). We previously reported that σ1RE102Q elicits toxicity in cells. The σ1R forms oligomeric states that are regulated by ligands. Nevertheless, little is known about the effect of ALS-related mutations on oligomer formation. Here, we transfected NSC-34 cells, a motor neuronal cell line, and HEK293T cells with σ1R-mCherry (mCh), σ1RE102Q-mCh, or nontagged forms to investigate detergent solubility and subcellular distribution using immunocytochemistry and fluorescence recovery after photobleaching. The oligomeric state was determined using crosslinking procedure. σ1Rs were soluble to detergents, whereas the mutants accumulated in the insoluble fraction. Within the soluble fraction, peak distribution of mutants appeared in higher sucrose density fractions. Mutants formed intracellular aggregates that were co-stained with p62, ubiquitin, and phosphorylated pancreatic eukaryotic translation initiation factor-2-α kinase in NSC-34 cells but not in HEK293T cells. The aggregates had significantly lower recovery in fluorescence recovery after photobleaching. Acute treatment with σ1R agonist SA4503 failed to improve recovery, whereas prolonged treatment for 48 h significantly decreased σ1RE102Q-mCh insolubility and inhibited apoptosis. Whereas σ1R-mCh formed monomers and dimers, σ1RE102Q-mCh also formed trimers and tetramers. SA4503 reduced accumulation of the four types in the insoluble fraction and increased monomers in the soluble fraction. The σ1RE102Q insolubility was diminished by σ1R-mCh co-expression. These results suggest that the agonist and WT σ1R modify the detergent insolubility, toxicity, and oligomeric state of σ1RE102Q, which may lead to promising new treatments for σ1R-related ALS.
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Affiliation(s)
- Yasuharu Shinoda
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Yudai Haga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Koichiro Akagawa
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
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Voronin MV, Vakhitova YV, Seredenin SB. Chaperone Sigma1R and Antidepressant Effect. Int J Mol Sci 2020; 21:E7088. [PMID: 32992988 PMCID: PMC7582751 DOI: 10.3390/ijms21197088] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/17/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022] Open
Abstract
This review analyzes the current scientific literature on the role of the Sigma1R chaperone in the pathogenesis of depressive disorders and pharmacodynamics of antidepressants. As a result of ligand activation, Sigma1R is capable of intracellular translocation from the endoplasmic reticulum (ER) into the region of nuclear and cellular membranes, where it interacts with resident proteins. This unique property of Sigma1R provides regulation of various receptors, ion channels, enzymes, and transcriptional factors. The current review demonstrates the contribution of the Sigma1R chaperone to the regulation of molecular mechanisms involved in the antidepressant effect.
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Affiliation(s)
- Mikhail V. Voronin
- Department of Pharmacogenetics, FSBI “Zakusov Institute of Pharmacology”, Baltiyskaya Street 8, 125315 Moscow, Russia;
| | | | - Sergei B. Seredenin
- Department of Pharmacogenetics, FSBI “Zakusov Institute of Pharmacology”, Baltiyskaya Street 8, 125315 Moscow, Russia;
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10
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Abramyan AM, Yano H, Xu M, Liu L, Naing S, Fant AD, Shi L. The Glu102 mutation disrupts higher-order oligomerization of the sigma 1 receptor. Comput Struct Biotechnol J 2020; 18:199-206. [PMID: 32055286 PMCID: PMC7005341 DOI: 10.1016/j.csbj.2019.12.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 12/18/2019] [Accepted: 12/20/2019] [Indexed: 11/18/2022] Open
Abstract
The sigma 1 receptor (σ1R) is a unique endoplasmic reticulum membrane protein. Its ligands have been shown to possess therapeutic potential for neurological and substance use disorders among others. The E102Q mutation of σ1R has been found to elicit familial cases of amyotrophic lateral sclerosis (ALS). Despite reports of its downstream signaling consequences, the mechanistic details of the functional impact of E102Q at molecular level are not clear. Here, we investigate the molecular mechanism of the E102Q mutation with a spectrum of biochemical, biophysical, and pharmacological approaches. Our analysis of the interaction network of σ1R indicates that a set of residues near E102 is critical for the integrity of C-terminal ligand-binding domain. However, this integrity is not affected by the E102Q and E102A mutations, which is confirmed by the radioligand binding results. Instead, the E102 mutations disrupt the connection between the C-terminal domain and the N-terminal transmembrane helix (NT-helix). Results from bioluminescence resonance energy transfer and western blot assays demonstrate that these mutations destabilize higher-order σ1R oligomers, while our molecular dynamics simulations based on a σ1R crystal structure reveal a potential mechanism by which the mutations perturb the NT-helix dynamics. Thus, we propose that E102 is at a critical position in propagating the effects of ligand binding from the C-terminal domain to the NT-helix, while the latter may be involved in forming alternative oligomer interfaces, separate from the previously reported trimer interface. Together, these results provide the first account of the molecular mechanism of σ1R dysfunction caused by E102Q.
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Affiliation(s)
| | | | | | | | | | | | - Lei Shi
- Corresponding author at: Triad Technology Center, 333 Cassell Drive, Room 1121, Baltimore, MD 21224, USA.
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