Environmental Control of Astrocyte Pathogenic Activities in CNS Inflammation.

Genome-wide studies have identified genetic variants linked to neurologic diseases. Environmental factors also play important roles, but no methods are available for their comprehensive investigation. We developed an approach that combines genomic data, screens in a novel zebrafish model, computational modeling, perturbation studies, and multiple sclerosis (MS) patient samples to evaluate the effects of environmental exposure on CNS inflammation. We found that the herbicide linuron amplifies astrocyte pro-inflammatory activities by activating signaling via sigma receptor 1, inositol-requiring enzyme-1α (IRE1α), and X-box binding protein 1 (XBP1). Indeed, astrocyte-specific shRNA- and CRISPR/Cas9-driven gene inactivation combined with RNA-seq, ATAC-seq, ChIP-seq, and study of patient samples suggest that IRE1α-XBP1 signaling promotes CNS inflammation in experimental autoimmune encephalomyelitis (EAE) and, potentially, MS. In summary, these studies define environmental mechanisms that control astrocyte pathogenic activities and establish a multidisciplinary approach for the systematic investigation of the effects of environmental exposure in neurologic disorders.

Potassium and Calcium Channel Complexes as Novel Targets for Cancer Research.

The intracellular Ca2+ concentration is mainly controlled by Ca2+ channels. These channels form complexes with K+ channels, which function to amplify Ca2+ flux. In cancer cells, voltage-gated/voltage-dependent Ca2+ channels and non-voltage-gated/voltage-independent Ca2+ channels have been reported to interact with K+ channels such as Ca2+-activated K+ channels and voltage-gated K+ channels. These channels are activated by an increase in cytosolic Ca2+ concentration or by membrane depolarization, which induces membrane hyperpolarization, increasing the driving force for Ca2+ flux. These complexes, composed of K+ and Ca2+ channels, are regulated by several molecules including lipids (ether lipids and cholesterol), proteins (e.g. STIM), receptors (e.g. S1R/SIGMAR1), and peptides (e.g. LL-37) and can be targeted by monoclonal antibodies, making them novel targets for cancer research.

Conduction block and temporal dispersion in a SIGMAR1-related neuropathy.

The distal hereditary motor neuropathies (dHMN) encompass a group of peripheral nervous system disorders characterized by progressive distal predominant weakness and wasting, usually in a length-dependent pattern. The classical neurophysiological pattern is a motor axonal neuropathy with chronic distal denervation/reinnervation on needle examination. Conduction block (CB) and temporal dispersion (TD) are electrophysiological features classically associated with acquired demyelinating neuropathies. Although they have rarely been reported in hereditary neuropathies, to date they have not been described in dHMN. We report a sporadic case of a patient with neurophysiological criteria consistent with multifocal motor neuropathy with CB (MMN) refractory to immunomodulation. WES revealed a homozygous nonsense pathogenic variant in sigma nonopioid intracellular receptor-1 gene (SIGMAR1). SIGMAR1-related disorders have been reported with distinctive features suggesting it is not a typical length-dependent neuropathy. Nevertheless, CB and TD are unexpected and as far as we have known not been described previously in such patients. This case expands the neurophysiological spectrum of this disease and alerts clinicians to this acquired demyelinating motor neuropathy mimic.

Distal hereditary motor neuronopathy of the Jerash type is caused by a novel SIGMAR1 c.500A>T missense mutation.

BACKGROUND: Distal hereditary motor neuronopathies (dHMN) are a group of genetic disorders characterised by motor neuron degeneration leading to muscle weakness that are caused by mutations in various genes. HMNJ is a distinct form of the disease that has been identified in patients from the Jerash region of Jordan. Our aim was to identify and characterise the genetic cause of HMNJ. METHODS: We used whole exome and Sanger sequencing to identify a novel genetic variant associated with the disease and then carried out immunoblot, immunofluorescence and apoptosis assays to extract functional data and clarify the effect of this novel SIGMAR1 mutation. Physical and neurological examinations were performed on selected patients and unaffected individuals in order to re-evaluate clinical status of patients 20 years after the initial description of HMNJ as well as to evaluate new and previously undescribed patients with HMNJ. RESULTS: A homozygous missense mutation (c.500A>T, N167I) in exon 4 of the SIGMAR1 gene was identified, cosegregating with HMNJ in the 27 patients from 7 previously described consanguineous families and 3 newly ascertained patients. The mutant SIGMAR1 exhibits reduced expression, altered subcellular distribution and elevates cell death when expressed. CONCLUSION: In conclusion, the homozygous SIGMAR1 c.500A>T mutation causes dHMN of the Jerash type, possibly due to a significant drop of protein levels. This finding is in agreement with other SIGMAR1 mutations that have been associated with autosomal recessive dHMN with pyramidal signs; thus, our findings further support that SIGMAR1 be added to the dHMN genes diagnostic panel.

Recessive distal motor neuropathy with pyramidal signs in an Omani kindred: underlying novel mutation in the SIGMAR1 gene.

BACKGROUND AND PURPOSE: Distal hereditary motor neuropathy (dHMN) due to sigma non-opioid intracellular receptor 1 (SIGMAR1) gene mutation (OMIM 601978.0003) is a rare neuromuscular disorder characterized by prominent amyotrophic distal limb weakness and co-existing pyramidal signs initially described in a Chinese family recently. We report an extended consanguineous Omani family segregating dHMN with pyramidal signs in an autosomal recessive pattern and describe a novel mutation in the SIGMAR1 gene underlying this motor phenotype. We also provide an update on the reported phenotypic profile of SIGMAR1 mutations. METHODS: We utilized homozygosity mapping and whole-exome sequencing of leucocyte DNA obtained from three affected members of an Omani family who manifested with a length-dependent motor neuropathy and pyramidal signs. RESULTS: We identified a novel C>T transition at nucleotide position 238 (c.238C>T) in exon 2 of the SIGMAR1 gene. Sanger sequencing and segregation analysis confirmed the presence of two copies of the variant in the affected subjects, unlike the unaffected healthy parents/sibling who carried, at most, a single copy. The T allele is predicted to cause a truncating mutation (p.Gln80*), probably flagging the mRNA for nonsense-mediated decay leading to a complete loss of function, thereby potentially contributing to the disease process. CONCLUSIONS: Our finding expands the spectrum of SIGMAR1 mutations causing recessive dHMN and indicates that this disorder is pan-ethnic. SIGMAR1 mutation should be included in the diagnostic panel of a dHMN, especially if there are co-existing pyramidal signs and autosomal recessive inheritance.

In silico analysis of SIGMAR1 variant (rs4879809) segregating in a consanguineous Pakistani family showing amyotrophic lateral sclerosis without frontotemporal lobar dementia.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. It has been found to be associated with frontotemporal lobar degeneration (FTLD). In the present study, we have described homozygosity mapping and gene sequencing in a consanguineous autosomal recessive Pakistani family showing non-juvenile ALS without signs of FTLD. Gene mapping was carried out in all recruited family members using microsatellite markers, and linkage was established with sigma non-opioid intracellular receptor 1 (SIGMAR1) gene at chromosome 9p13.2. Gene sequencing of SIGMAR1 revealed a novel 3'-UTR nucleotide variation c.672*31A>G (rs4879809) segregating with disease in this family. The C9ORF72 repeat region in intron 1, previously implicated in a related phenotype, was excluded through linkage, and further confirmation of exclusion was obtained by amplifying intron 1 of C9ORF72 with multiple primers in affected individuals and controls. In silico analysis was carried out to explore the possible role of 3'-UTR variant of SIGMAR1 in ALS. The Regulatory RNA motif and Element Finder program revealed disturbance in miRNA (hsa-miR-1205) binding site due to this variation. ESEFinder analysis showed new SRSF1 and SRSF1-IgM-BRCA1 binding sites with significant scores due to this variation. Our results indicate that the 3'-UTR SIGMAR1 variant c.672*31A>G may have a role in the pathogenesis of ALS in this family.

The role of SIGMAR1 gene mutation and mitochondrial dysfunction in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) patients exhibit diverse pathologies such as endoplasmic reticulum (ER) stress and mitochondrial dysfunction in motor neurons. Five to ten percent of patients have familial ALS, a form of the disease caused by mutations in ALS-related genes, while sporadic forms of the disease occur in 90-95% of patients. Recently, it was reported that familial ALS patients exhibit a missense mutation in SIGMAR1 (c.304G > C), which encodes sigma-1 receptor (Sig-1R), substituting glutamine for glutamic acid at amino acid residue 102 (p.E102Q). Expression of that mutant Sig-1R(E102Q) protein reduces mitochondrial ATP production, inhibits proteasome activity and causes mitochondrial injury, aggravating ER stress-induced neuronal death in neuro2A cells. In this issue, we discuss mechanisms underlying mitochondrial impairment seen in ALS motor neurons and propose that therapies that protect mitochondria might improve the quality of life (QOL) of ALS patients and should be considered for clinical trials.

Targeted siRNA Screens Identify ER-to-Mitochondrial Calcium Exchange in Autophagy and Mitophagy Responses in RPE1 Cells.

Autophagy is an important stress response pathway responsible for the removal and recycling of damaged or redundant cytosolic constituents. Mitochondrial damage triggers selective mitochondrial autophagy (mitophagy), mediated by a variety of response factors including the Pink1/Parkin system. Using human retinal pigment epithelial cells stably expressing autophagy and mitophagy reporters, we have conducted parallel screens of regulators of endoplasmic reticulum (ER) and mitochondrial morphology and function contributing to starvation-induced autophagy and damage-induced mitophagy. These screens identified the ER chaperone and Ca2+ flux modulator, sigma non-opioid intracellular receptor 1 (SIGMAR1), as a regulator of autophagosome expansion during starvation. Screens also identified phosphatidyl ethanolamine methyl transferase (PEMT) and the IP3-receptors (IP3Rs) as mediators of Parkin-induced mitophagy. Further experiments suggested that IP3R-mediated transfer of Ca2+ from the ER lumen to the mitochondrial matrix via the mitochondrial Ca2+ uniporter (MCU) primes mitochondria for mitophagy. Importantly, recruitment of Parkin to damaged mitochondria did not require IP3R-mediated ER-to-mitochondrial Ca2+ transfer, but mitochondrial clustering downstream of Parkin recruitment was impaired, suggesting involvement of regulators of mitochondrial dynamics and/or transport. Our data suggest that Ca2+ flux between ER and mitochondria at presumed ER/mitochondrial contact sites is needed both for starvation-induced autophagy and for Parkin-mediated mitophagy, further highlighting the importance of inter-organellar communication for effective cellular homeostasis.

Blocking Sigmar1 exacerbates methamphetamine-induced hypertension.

AIM: Methamphetamine (METH) chronic exposure is an important risk factor for hypertension development. However, the mechanisms behind METH-induced hypertension remain unclear. Therefore, we aimed to reveal the potential mechanisms underlying METH-induced hypertension. METHODS AND RESULTS: We structured the mouse hypertension model by METH, and observed that METH-treated mice have presented vascular remodeling (large-and small-size arteries) with collagen deposit around the vessel and increasing blood pressure (BP) and Sigma1 receptor (Sigmar1) in vascular tissue. We hypothesized that Sigmar1 is crucial in METH-induced hypertension and vascular remodeling. Sigmar1 knockout (KO) mice and antagonist (BD1047) pretreated mice exposed to METH for six-week showed higher BP and more collagen deposited around vessels than wild-type (WT) mice exposed to METH for six-week, in contrast, mice pretreated with Sigmar1 agonist (PRE-084) had unchanged BP and perivascular collagen despite the six-week METH exposure. Furthermore, we found that METH exposure induced vascular smooth muscle cells (VSMCs) and mesenchymal stem cells to differentiate into the myofibroblast-like cell and secrete collagen into surrounding vessels. Mechanically, Sigmar1 can suppress the COL1A1 expression by blocking the classical fibrotic TGF-ß/Smad2/3 signaling pathway in METH-exposed VSMCs and mesenchymal stem cells. CONCLUSION: Our results suggest that Sigmar1 is involved in METH-induced hypertension and vascular fibrosis by blocking the activation of the TGF-ß/Smad2/3 signaling pathway. Accordingly, Sigmar1 may be a novel therapeutic target for METH-induced hypertension and vascular fibrosis.

SigmaR1 shapes rough endoplasmic reticulum membrane sheets.

Rough endoplasmic reticulum (ER) sheets are a fundamental domain of the ER and the gateway into the secretory pathway. Although reticulon proteins stabilize high-curvature ER tubules, it is unclear whether other proteins scaffold the flat membranes of rough ER sheets. Through a proteomics screen using ER sheet-localized RNA-binding proteins as bait, we identify the sigma-1 receptor (SigmaR1) as an ER sheet-shaping factor. High-resolution live cell imaging and electron tomography assign SigmaR1 as an ER sheet-localized factor whose levels determine the amount of rough ER sheets in cells. Structure-guided mutagenesis and in vitro reconstitution on giant unilamellar vesicles further support a mechanism whereby SigmaR1 oligomers use their extended arrays of amphipathic helices to bind and flatten the lumenal leaflet of ER membranes to oppose membrane curvature and stabilize rough ER sheets.

The Sigma-1 Receptor Exacerbates Cardiac Dysfunction Induced by Obstructive Nephropathy: A Role for Sexual Dimorphism.

The Sigma-1 Receptor (Sigmar1) is a stress-activated chaperone and a promising target for pharmacological modulation due to its ability to induce multiple cellular responses. Yet, it is unknown how Sigmar1 is involved in cardiorenal syndrome type 4 (CRS4) in which renal damage results in cardiac dysfunction. This study explored the role of Sigmar1 and its ligands in a CRS4 model induced by unilateral ureteral obstruction (UUO) in male and female C57BL/6 mice. We evaluated renal and cardiac dysfunction markers, Sigmar1 expression, and cardiac remodeling through time (7, 12, and 21 days) and after chronically administering the Sigmar1 agonists PRE-084 (1 mg/kg/day) and SA4503 (1 mg/kg/day), and the antagonist haloperidol (2 mg/kg/day), for 21 days after UUO using colorimetric analysis, RT-qPCR, histology, immunohistochemistry, enzyme-linked immunosorbent assay, RNA-seq, and bioinformatics. We found that obstructive nephropathy induces Sigmar1 expression in the kidneys and heart, and that Sigmar1 stimulation with its agonists PRE-084 and SA4503 aggravates cardiac dysfunction and remodeling in both sexes. Still, their effects are significantly more potent in males. Our findings reveal essential differences associated with sex in the development of CRS4 and should be considered when contemplating Sigmar1 as a pharmacological target.

Unraveling the CLCC1 interactome: Impact of the Asp25Glu variant and its interaction with SigmaR1 at the Mitochondrial-Associated ER Membrane (MAM).

The endoplasmic reticulum (ER) plays an indispensable role in cellular processes, including maintenance of calcium homeostasis, and protein folding, synthesized and processing. Disruptions in these processes leading to ER stress and the accumulation of misfolded proteins can instigate the unfolded protein response (UPR), culminating in either restoration of balanced proteostasis or apoptosis. A key player in this intricate balance is CLCC1, an ER-resident chloride channel, whose essential role extends to retinal development, regulation of ER stress, and UPR. The importance of CLCC1 is further underscored by its interaction with proteins localized to mitochondria-associated endoplasmic reticulum membranes (MAMs), where it participates in UPR induction by MAM proteins. In previous research, we identified a p.(Asp25Glu) pathogenic CLCC1 variant associated with retinitis pigmentosa (RP) (CLCC1 hg38 NC_000001.11; NM_001048210.3, c.75C > A; UniprotKB Q96S66). In attempt to decipher the impact of this variant function, we leveraged liquid chromatography-mass spectrometry (LC-MS) to identify likely CLCC1-interacting proteins. We discovered that the CLCC1 interactome is substantially composed of proteins that localize to ER compartments and that the Asp25Glu variant results in noticeable loss and gain of specific protein interactors. Intriguingly, the analysis suggests that the CLCC1Asp25Glu mutant protein exhibits a propensity for increased interactions with cytoplasmic proteins compared to its wild-type counterpart. To corroborate our LC-MS data, we further scrutinized two novel CLCC1 interactors, Calnexin and SigmaR1, chaperone proteins that localize to the ER and MAMs. Through microscopy, we demonstrate that CLCC1 co-localizes with both proteins, thereby validating our initial findings. Moreover, our results reveal that CLCC1 co-localizes with SigmaR1 not merely at the ER, but also at MAMs. These findings reinforce the notion of CLCC1 interacting with MAM proteins at the ER-mitochondria interface, setting the stage for further exploration into how these interactions impact ER or mitochondria function and lead to retinal degenerative disease when impaired.

SIGMAR1/Sigma-1 receptor: a key regulator in stabilizing and translating LC3B mRNA for autophagosome formation.

Macroautophagy/autophagy degrades and recycles cellular constituents via the lysosome to maintain cellular homeostasis. Our study identified the endoplasmic reticulum (ER)-resident SIGMAR1 (sigma non-opioid intracellular receptor 1) as a critical regulator of the biosynthesis of Atg8-family proteins that leads to the lipidation that is essential during autophagosome formation. We demonstrate that SIGMAR1 stabilizes MAP1LC3B/LC3B and GABARAP mRNAs, promoting their localized translation proximal to the ER for efficient lipidation. Using single-molecule fluorescence in situ hybridization/smFISH and co-immunoprecipitation, we found that SIGMAR1 directly binds to a conserved region in the 3' UTR of LC3B mRNA, facilitating its translation, efficient lipidation, and proper integration into the phagophore membrane. Cells lacking SIGMAR1 show reduced levels of many Atg8-family proteins and impaired autophagic flux. Our model suggests that SIGMAR1-mediated localized translation of Atg8-family proteins at the ER promotes efficient autophagosome formation, in contrast to recruiting preexisting cytosolic Atg8-family proteins to the lipidation machinery. Elucidating the role of SIGMAR1 in autophagy may provide better therapeutic strategies to prevent or treat autophagy-dependent neurodegenerative diseases, particularly given the highly druggable nature of SIGMAR1.

Deletion of Sigmar1 leads to increased arterial stiffness and altered mitochondrial respiration resulting in vascular dysfunction.

Sigmar1 is a ubiquitously expressed, multifunctional protein known for its cardioprotective roles in cardiovascular diseases. While accumulating evidence indicate a critical role of Sigmar1 in cardiac biology, its physiological function in the vasculature remains unknown. In this study, we characterized the expression of Sigmar1 in the vascular wall and assessed its physiological function in the vascular system using global Sigmar1 knockout (Sigmar1-/-) mice. We determined the expression of Sigmar1 in the vascular tissue using immunostaining and biochemical experiments in both human and mouse blood vessels. Deletion of Sigmar1 globally in mice (Sigmar1-/-) led to blood vessel wall reorganizations characterized by nuclei disarray of vascular smooth muscle cells, altered organizations of elastic lamina, and higher collagen fibers deposition in and around the arteries compared to wildtype littermate controls (Wt). Vascular function was assessed in mice using non-invasive time-transit method of aortic stiffness measurement and flow-mediated dilation (FMD) of the left femoral artery. Sigmar1-/- mice showed a notable increase in arterial stiffness in the abdominal aorta and failed to increase the vessel diameter in response to reactive-hyperemia compared to Wt. This was consistent with reduced plasma and tissue nitric-oxide bioavailability (NOx) and decreased phosphorylation of endothelial nitric oxide synthase (eNOS) in the aorta of Sigmar1-/- mice. Ultrastructural analysis by transmission electron microscopy (TEM) of aorta sections showed accumulation of elongated shaped mitochondria in both vascular smooth muscle and endothelial cells of Sigmar1-/- mice. In accordance, decreased mitochondrial respirometry parameters were found in ex-vivo aortic rings from Sigmar1 deficient mice compared to Wt controls. These data indicate a potential role of Sigmar1 in maintaining vascular homeostasis.

Genetic and in silico analysis of Indian sporadic young onset patient with amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is an old onset devastating neurodegenerative disorder. Young-onset ALS cases especially sporadic ones who are between 25 and 45 years are rarely affected by the disease. Despite the identification of numerous candidate genes associated with ALS, the etiology of the disease remains elusive due to extreme genetic and phenotypic variability. The advent of affordable whole exome sequencing (WES) has opened new avenues for unraveling the disease's pathophysiology better. METHODS AND RESULTS: We aimed to determine the genetic basis of an Indian-origin, young onset sporadic ALS patient with very rapid deterioration of the disease course without any cognitive decline who was screened for mutations in major ALS candidate genes by WES. Variants detected were reconfirmed by Sanger sequencing. The clinicopathological features were investigated and two heterozygous missense variants were identified: R452W, not previously associated with ALS, present in one of the four conserved C terminal domains in ANXA11 and R208W in SIGMAR1, respectively. Both of these variants were predicted to be damaging by pathogenicity prediction tools and various in silico methods. CONCLUSION: Our study revealed two potentially pathogenic variants in two ALS candidate genes. The genetic makeup of ALS patients from India has been the subject of a few prior studies, but none of them examined ANXA11 and SIGMAR1 genes so far. These results establish the framework for additional research into the pathogenic processes behind these variations that result in sporadic ALS disease and further our understanding of the genetic makeup of Indian ALS patients.

Amiodarone Advances the Apoptosis of Cardiomyocytes by Repressing Sigmar1 Expression and Blocking KCNH2-related Potassium Channels.

BACKGROUND: Heart failure (HF) is the ultimate transformation result of various cardiovascular diseases. Mitochondria-mediated cardiomyocyte apoptosis has been uncovered to be associated with this disorder. OBJECTIVE: This study mainly delves into the mechanism of the anti-arrhythmic drug amiodarone on mitochondrial toxicity of cardiomyocytes. METHODS: The viability of H9c2 cells treated with amiodarone at 0.5, 1, 2, 3, and 4 µM was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and Sigmar1 expression was examined by quantitative real-time PCR (qRTPCR). After transfection, the viability, apoptosis, reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), and potassium voltage-gated channel subfamily H member 2 (KCNH2) expression in H9c2 cells were assessed by MTT, flow cytometry, ROS assay kit, mitochondria staining kit, and Western blot. RESULTS: Amiodarone at 1-4 µM notably weakened H9c2 cell viability with IC50 value of 2.62 ± 0.43 µM. Amiodarone at 0.5-4 µM also evidently suppressed the Sigmar1 level in H9c2 cells. Amiodarone repressed H9c2 cell viability and KCNH2 level and triggered apoptosis, ROS production and mitochondrial depolarization, while Sigmar1 upregulation reversed its effects. Moreover, KCNH2 silencing neutralized the combined modulation of amiodarone and Sigmar1 up-regulation on H9c2 cell viability, apoptosis, and ROS production. CONCLUSION: Amiodarone facilitates the apoptosis of H9c2 cells by restraining Sigmar1 expression and blocking KCNH2-related potassium channels.

Sigma-1 receptor exerts protective effects on ameliorating nephrolithiasis by modulating endoplasmic reticulum-mitochondrion association and inhibiting endoplasmic reticulum stress-induced apoptosis in renal tubular epithelial cells.

Oxalate-induced damage to renal tubular epithelial cells (RTECs) is an essential factor in the incident kidney stone, but the specific mechanism is unclear. Recent research has pinpointed interacting areas within the endoplasmic reticulum and mitochondria, called mitochondria-associated membranes (MAMs). These studies have linked endoplasmic reticulum stress (ERS) and oxidative imbalance to kidney disease development. The sigma-1 receptor (S1R), a specific protein found in MAMs, is involved in various physiological processes, but its role in oxalate-induced kidney stone formation remains unclear. In this study, we established cellular and rat models of oxalate-induced kidney stone formation to elucidate the S1R's effects against ERS and apoptosis and its mechanism in oxalate-induced RTEC injury. We found that oxalate downregulated S1R expression in RTECs and escalated oxidative stress and ERS, culminating in increased apoptosis. The S1R agonist dimemorfan up-regulated S1R expression and mitigated ERS and oxidative stress, thereby reducing apoptosis. This protective effect was mediated through S1R inhibition of the CHOP pathway. Animal experiments demonstrated that S1R's activation attenuated oxalate-induced kidney injury and alleviated kidney stone formation. This is the first study to establish the connection between S1R and kidney stones, suggesting S1R's protective role in inhibiting ERS-mediated apoptosis to ameliorate kidney stone formation.

The involvement of SigmaR1K142 degradation mediated by ERAD in neural senescence linked with CdCl2 exposure.

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Due to its uncertain pathogenesis, there is currently no treatment available for AD. Increasing evidences have linked cellular senescence to AD, although the mechanism triggering cellular senescence in AD requires further exploration. To investigate the involvement of cellular senescence in AD, we explored the effects of cadmium chloride (CdCl2) exposure, one of the potential environmental risk factors for AD, on neuron senescence in vivo and in vitro. ß-amyloid (Aß) and tubulin-associated protein (tau) pathologies were found to be enhanced by CdCl2 exposure in the in vitro models, while p53/p21/Rb cascade-related neuronal senescence pathways were activated. Conversely, the use of melatonin, a cellular senescence inhibitor, or a cadmium ion chelator suppressed CdCl2-induced neuron senescence, along with the Aß and tau pathologies. Mechanistically, CdCl2 exposure activated the suppressor enhancer Lin-12/Notch 1-like (SEL1L)/HMG-CoA reductase degradation 1 (HRD1)-regulated endoplasmic reticulum-associated degradation (ERAD), which enhanced the ubiquitin degradation of sigma-1 receptor (SigmaR1) by specifically recognizing its K142 site, resulting in the activation of the p53/p21/Rb pathway via the induction of Ca2+ dyshomeostasis and mitochondrial dysfunction. In the in vivo models, the administration of the SigmaR1 agonist ANAVEX2-73 rescues neurobehavioral inhibition and alleviates cellular senescence and AD-like pathology in the brain tissue of CdCl2-exposed mice. Consequently, the present study revealed a novel senescence-associated regulatory route for the SEL1L/HRD1/SigmaR1 axis that affects the pathological progression of CdCl2 exposure-associated AD. CdCl2 exposure activated SEL1L/HRD1-mediated ERAD and promoted the ubiquitinated degradation of SigmaR1, activating p53/p21/Rb pathway-regulated neuronal senescence. The results of the present study suggest that SigmaR1 may function as a neuroprotective biomarker of neuronal senescence, and pharmacological activation of SigmaR1 could be a promising intervention strategy for AD therapy.

Multi-Omics Analysis Reveals the Role of Sigma-1 Receptor in a Takotsubo-like Cardiomyopathy Model.

Takotsubo syndrome (TTS) is a stress-induced cardiomyopathy that presents with sudden onset of chest pain and dyspneic and cardiac dysfunction as a result of extreme physical or emotional stress. The sigma-1 receptor (Sigmar1) is a ligand-dependent molecular chaperone that is postulated to be involved in various processes related to cardiovascular disease. However, the role of Sigmar1 in TTS remains unresolved. In this study, we established a mouse model of TTS using wild-type and Sigmar1 knockout mice to investigate the involvement of Sigmar1 in TTS development. Our results revealed that Sigmar1 knockout exacerbated cardiac dysfunction, with a noticeable decrease in ejection fraction (EF) and fractional shortening (FS) compared to the wild-type model. In terms of the gut microbiome, we observed regulation of Firmicutes and Bacteroidetes ratios; suppression of probiotic Lactobacillus growth; and a rise in pathogenic bacterial species, such as Colidextribacter. Metabolomic and transcriptomic analyses further suggested that Sigmar1 plays a role in regulating tryptophan metabolism and several signaling pathways, including MAPK, HIF-1, calcium signaling, and apoptosis pathways, which may be crucial in TTS pathogenesis. These findings offer valuable insight into the function of Sigmar1 in TTS, and this receptor may represent a promising therapeutic target for TTS.

SIGMAR1 variants in ALS-PD complex cases: a case report of a novel mutation and literature review.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons, with occasional involvement of the extrapyramidal system. Mutations in the sigma non-opioid intracellular receptor 1 (SIGMAR1) gene have been identified as one of the causes of ALS. Here, we present a case of a 49-year-old man diagnosed with ALS-Parkinson's disease (PD) complex. The patient exhibited bradykinesia and tremor, and whole-exome sequencing revealed homozygous mutations in the SIGMAR1 gene (c.446-2A > T). In addition, we conducted an investigation into the clinical and molecular phenotype of previously reported variants of SIGMAR1 associated with ALS. This case report aims to raise awareness among physicians regarding atypical phenotypes of amyotrophic lateral sclerosis and to encourage further research on the factors leading to SIGMAR1 mutations in patients.