SERCA control of cell death and survival

SERCA-mediated endoplasmic reticulum stress facilitates hematopoietic stem cell mobilization

BACKGROUND

Hematopoietic stem cell (HSC) transplantation is widely recognized as an effective treatment for various malignant diseases. Enhancing HSC mobilization can improve transplantation outcomes and ultimately increase patient survival rates. Recent studies suggest that mild endoplasmic reticulum (ER) stress promotes HSC self-renewal, anti-apoptotic, and anti-aging capabilities. This led us to investigate whether inducing mild ER stress could facilitate HSC mobilization.

METHODS

The phenotype changes in cells treated with ER stress inducers and Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibitors were assessed using flow cytometry. The efficacy of these agents on HSC mobilization was evaluated in C57Bl/6 mice, with colony forming unit (CFU) assays used for quantification. Knockdown Jurkat cell lines were constructed to validate the role of SERCA in the mobilization mechanism. Molecular and protein expression levels associated with the pathway were analyzed through quantitative reverse-transcription PCR and western blotting.

RESULTS

Our findings revealed that BHQ, a SERCA inhibitor, efficiently enhanced HSC mobilization in vivo. Mechanistically, BHQ regulated the CaMKII-STAT3-CXCR4 pathway by suppressing SERCA activity. This inhibition led to a reduction in CXCR4 expression on the surface of HSCs, facilitating their migration from the bone marrow into peripheral circulation.

CONCLUSIONS

Our study provides novel insights into the role of the SERCA-ER stress pathway in HSC mobilization. By targeting SERCA activity with BHQ, we observed a significant enhancement in the mobilization of HSCs, facilitated by the modulation of the CaMKII-STAT3-CXCR4 signaling pathway. This research highlights the potential of utilizing mild ER stress as a strategy to promote HSC mobilization, with significant implications for improving stem cell-based therapies, including those used in HSC transplantation.

Emerging roles for microproteins as critical regulators of endoplasmic reticulum function and cellular homeostasis

The endoplasmic reticulum (ER) is a multifunctional organelle essential for key cellular processes including protein synthesis, calcium homeostasis, and the cellular stress response. It is composed of distinct domains, such as the rough and smooth ER, as well as membrane regions that facilitate direct communication with other organelles, enabling its diverse functions. While many well-characterized ER proteins contribute to these processes, recent studies have revealed a previously underappreciated class of small proteins that play critical regulatory roles. Microproteins, typically under 100 amino acids in length, were historically overlooked due to size-based biases in genome annotation and often misannotated as noncoding RNAs. Advances in ribosome profiling, mass spectrometry, and computational approaches have now enabled the discovery of numerous previously unrecognized microproteins, significantly expanding our understanding of the proteome. While some ER-associated microproteins, such as phospholamban and sarcolipin, were identified decades ago, newly discovered microproteins share similar fundamental characteristics, underscoring the need to refine our understanding of the coding potential of the genome. Molecular studies have demonstrated that ER microproteins play essential roles in calcium regulation, ER stress response, organelle communication, and protein translocation. Moreover, growing evidence suggests that ER microproteins contribute to cellular homeostasis and are implicated in disease processes, including cardiovascular disease and cancer. This review examines the shared and unique functions of ER microproteins, their implications for health and disease, and their potential as therapeutic targets for conditions associated with ER dysfunction.

Crosstalk between calcium and reactive oxygen species signaling in cancer revisited

The homeostasis of cellular reactive oxygen species (ROS) and calcium (Ca2+) are intricately linked. ROS signaling and Ca2+ signaling are reciprocally regulated within cellular microdomains and are crucial for transcription, metabolism and cell function. Tumor cells often highjack ROS and Ca2+ signaling mechanisms to ensure optimal cell survival and tumor progression. Expression and regulation of Ca2+ channels and transporters at the plasma membrane, endoplasmic reticulum, mitochondria and other endomembranes are often altered in tumor cells, and this includes their regulation by ROS and reactive nitrogen species (RNS). Likewise, alterations in cellular Ca2+ levels influence the generation and scavenging of oxidants and thus can alter the redox homeostasis of the cell. This interplay can be either beneficial or detrimental to the cell depending on the localization, duration and levels of ROS and Ca2+ signals. At one end of the spectrum, Ca2+ and ROS/RNS can function as signaling modules while at the other end, lethal surges in these species are associated with cell death. Here, we highlight the interplay between Ca2+ and ROS in cancer progression, emphasize the impact of redox regulation on Ca2+ transport mechanisms, and describe how Ca2+ signaling pathways, in turn, can regulate the cellular redox environment.

The juxtamembrane sequence of small ankyrin 1 mediates the binding of its cytoplasmic domain to SERCA1 and is required for inhibitory activity

Sarcoplasmic/endoplasmic reticulum Ca2+-ATPase1 (SERCA1) is responsible for the clearance of cytosolic Ca2+ in skeletal muscle. Due to its vital importance in regulating Ca2+ homeostasis, the regulation of SERCA1 has been intensively studied. Small ankyrin 1 (sAnk1, Ank1.5), a 17 kDa muscle-specific isoform of ANK1, binds to SERCA1 directly via both its transmembrane and cytoplasmic domains and inhibits SERCA1's ATPase activity. Here, we characterize the interaction between the cytoplasmic domain of sAnk1 (sAnk1(29-155)) and SERCA1. The binding affinity for sAnk1 (29-155) to SERCA1 was 444 nM by blot overlay, about 7-fold weaker than the binding of sAnk1(29-155) to obscurin, a giant protein of the muscle cytoskeleton. Site-directed mutagenesis identified K38, H39, and H41, in the juxtamembrane region, as residues likely to mediate binding to SERCA1. These residues are not required for obscurin binding. Residues R64-K73, which do contribute to obscurin binding, are also required for binding to SERCA1, but only the hydrophobic residues in this sequence are required, not the positively charged residues necessary for obscurin binding. Circular dichroism analysis of sAnk1(29-155) indicates that most mutants show significant structural changes, with the exception of those containing alanines in place of K38, H39 and H41. Although the cytoplasmic domain of sAnk1 does not inhibit SERCA1's Ca2+-ATPase activity, with or without mutations in the juxtamembrane sequence, the inhibitory activity of full-length sAnk1 requires the WT juxtamembrane sequence. We used these data to model sAnk1 and the sAnk1-SERCA1 complex. Our results suggest that, in addition to its transmembrane domain, sAnk1 uses its juxtamembrane sequence and perhaps part of its obscurin binding site to bind to SERCA1, and that this binding contributes to their robust association in situ, as well as regulation of SERCA1's activity.

Influences of lead-based perovskite nanoparticles exposure on early development of human retina

BACKGROUND

Lead-based perovskite nanoparticles (Pb-PNPs) are widely utilized in the photovoltaic industry. However, due to their poor stability and high water solubility, lead often gets released into the environment, which can negatively impact the development of the central nervous system (CNS). As an extension of the CNS, the effects and mechanisms of Pb-PNPs on human retinal development have remained elusive.

OBJECTIVES

We aimed to investigate the effects of Pb-PNPs on human retinal development.

METHODS

Human embryonic stem cell-derived three-dimensional floating retinal organoids (hEROs) were established to simulate early retinal development. Using immunofluorescence staining, biological-transmission electron microscopy analysis, inductively coupled plasma-mass spectrometry, two-dimensional element distribution detection, and RNA sequencing, we evaluated and compared the toxicity of CsPbBr3 nanoparticles (a representative substance of Pb-PNPs) and Pb(AC)2 and investigated the toxicity-reducing effects of SiO2 encapsulation.

RESULTS

Our findings revealed that CsPbBr3 nanoparticles exposure resulted in a concentration-dependent decrease in the area and thickness of the neural retina in hEROs. Additionally, CsPbBr3 nanoparticles exposure hindered cell proliferation and promoted cell apoptosis while suppressing the retinal ganglion cell differentiation, an alteration that further led to the disruption of retinal structure. By contrast, CsPbBr3 nanoparticles exposure to hEROs was slightly less toxic than Pb(AC)2. Mechanistically, CsPbBr3 nanoparticles exposure activated endoplasmic reticulum stress, which promoted apoptosis by up-regulating Caspase-3 and inhibited retinal ganglion cell development by down-regulating Pax6. Interestingly, after coating CsPbBr3 nanoparticles with silica, it exhibited lower toxicities to hEROs by alleviating endoplasmic reticulum stress.

CONCLUSION

Overall, our study provides evidence of Pb-PNPs-induced developmental toxicity in the human retina, explores the potential mechanisms of CsPbBr3 nanoparticles' developmental toxicity, and suggests a feasible strategy to reduce toxicity.

Molecular basis of the development of Parkinson's disease

Parkinson's disease is one of the most prevalent neurodegenerative motor disorders worldwide with postural instability, bradykinesia, resting tremor and rigidity being the most common symptoms of the disease. Despite the fact that the molecular mechanisms of Parkinson's disease pathogenesis have already been well described, there is still no coherent picture of the etiopathogenesis of this disease. According to modern concepts, neurodegeneration is induced mainly by oxidative stress, neuroinflammation, dysregulation of cerebral proteostasis, apoptotic dysregulation, and impaired autophagy. This review describes how various factors contribute to neurodegeneration in Parkinson's disease. Understanding the factors affecting fundamental cellular processes and responsible for disease progression may help develop therapeutic strategies to improve the quality of life of patients suffering from the disease. The review also discusses the role of calpains in the development of Parkinson's disease. It is known that α-synuclein is a substrate of calcium-dependent proteases of the calpain family. Truncated forms of α-synuclein are not only involved in the process of formation of the aggregates, but also increase their toxicity.

The Protective Effect of Nimodipine in Schwann Cells Is Related to the Upregulation of LMO4 and SERCA3 Accompanied by the Fine-Tuning of Intracellular Calcium Levels

Nimodipine is the current gold standard in the treatment of subarachnoid hemorrhage, as it is the only known calcium channel blocker that has been proven to improve neurological outcomes. In addition, nimodipine exhibits neuroprotective properties in vitro under various stress conditions. Furthermore, clinical studies have demonstrated a neuroprotective effect of nimodipine after vestibular schwannoma surgery. However, the molecular mode of action of nimodipine pre-treatment has not been well investigated. In the present study, using real-time cell death assays, we demonstrated that nimodipine not only reduces cell death induced by osmotic and oxidative stress but also protects cells directly at the time of stress induction in Schwann cells. Nimodipine counteracts stress-induced calcium overload and the overexpression of the Cav1.2 calcium channel. In addition, we found nimodipine-dependent upregulation of sarcoplasmic/endoplasmic reticulum calcium ATPase 3 (SERCA3) and LIM domain only 4 (LMO4) protein. Analysis of anti-apoptotic cell signaling showed an inhibition of the pro-apoptotic protein glycogen synthase kinase 3 beta (GSK3β). Nimodipine-treated Schwann cells exhibited higher levels of phosphorylated GSK3β at serine residue 9 during osmotic and oxidative stress. In conclusion, nimodipine prevents cell death by protecting cells from calcium overload by fine-tuning intracellular calcium signaling and gene expression.

The Impact of Calcium Overload on Cellular Processes: Exploring Calcicoptosis and Its Therapeutic Potential in Cancer

The key role of calcium in various physiological and pathological processes includes its involvement in various forms of regulated cell death (RCD). The concept of 'calcicoptosis' has been introduced as a calcium-induced phenomenon associated with oxidative stress and cellular damage. However, its definition remains controversial within the research community, with some considering it a general form of calcium overload stress, while others view it as a tumor-specific calcium-induced cell death. This review examines 'calcicoptosis' in the context of established RCD mechanisms such as apoptosis, necroptosis, ferroptosis, and others. It further analyzes the intricate relationship between calcium dysregulation and oxidative stress, emphasizing that while calcium overload often triggers cell death, it may not represent an entirely new type of RCD but rather an extension of known pathways. The purpose of this paper is to discuss the implications of this perspective for cancer therapy focusing on calcium-based nanoparticles. By investigating the connections between calcium dynamics and cell death pathways, this review contributes to the advancement of our understanding of calcicoptosis and its possible therapeutic uses.

The impact of 3-sulfo-taurolithocholic acid on ATPase activity in patients' colorectal cancer and normal colon tissues, and its hepatic effects in rodents

Colorectal cancer is influenced by genetic mutations, lifestyle factors, and diet, particularly high fat intake, which raises bile acid levels in the intestinal lumen. This study hypothesized that bile acids contribute to tumorigenesis by disrupting ion transport and ATPase activity in the intestinal mucosa. The effects of 3-sulfo-taurolithocholic acid (TLC-S) on ATPase activity were investigated in colorectal cancer samples from 10 patients, using adjacent healthy tissue as controls, and in rodent liver function. ATPase activity was measured spectrophotometrically by determining inorganic phosphorus (Pi) in postmitochondrial fractions. Ca2+ dynamics were assessed in isolated mouse hepatocytes with fluorescence imaging, and rat liver mitochondria were studied using polarographic methods to evaluate respiration and oxidative phosphorylation. TLC-S increased Na+/K+ ATPase activity by 1.5 times in colorectal cancer samples compared to controls (p ≤ 0.05). In healthy mucosa, TLC-S decreased Mg2+ ATPase activity by 3.6 times (p ≤ 0.05), while Mg2+ ATPase activity in cancer tissue remained unchanged. TLC-S had no significant effect on Ca2+ ATPase activity in healthy colon mucosa but showed a trend toward decreased activity in cancer tissue. In rat liver, TLC-S decreased Ca2+ ATPase and Na+/K+ ATPase activities while increasing basal Mg2+ ATPase activity (p ≤ 0.05). Additionally, TLC-S induced cytosolic Ca2+ signals in mouse hepatocytes, partially attenuated by NED-19, an NAADP antagonist (p ≤ 0.05). TLC-S also reduced the V3 respiration rate of isolated rat liver mitochondria during α-ketoglutarate oxidation. These findings suggest that TLC-S modulates ATPase activity differently in cancerous and healthy colon tissues, playing a role in colorectal cancer development. In rat liver, TLC-S affects mitochondrial activity and ATPase function, contributing to altered cytosolic calcium levels, providing insight into the mechanistic effects of bile acids on colorectal cancer and liver function.

S-acylation of Ca2+ transport proteins in cancer

Alterations in cellular calcium (Ca2+) signals have been causally associated with the development and progression of human cancers. Cellular Ca2+ signals are generated by channels, pumps, and exchangers that move Ca2+ ions across membranes and are decoded by effector proteins in the cytosol or in organelles. S-acylation, the reversible addition of 16-carbon fatty acids to proteins, modulates the activity of Ca2+ transporters by altering their affinity for lipids, and enzymes mediating this reversible post-translational modification have also been linked to several types of cancers. Here, we compile studies reporting an association between Ca2+ transporters or S-acylation enzymes with specific cancers, as well as studies reporting or predicting the S-acylation of Ca2+ transporters. We then discuss the potential role of S-acylation in the oncogenic potential of a subset of Ca2+ transport proteins involved in cancer.

Calcium Transport and Enrichment in Microorganisms: A Review

Calcium is a vital trace element for the human body, and its deficiency can result in a range of pathological conditions, including rickets and osteoporosis. Despite the numerous types of calcium supplements currently available on the market, these products are afflicted with a number of inherent deficiencies, such as low calcium content, poor aqueous solubility, and low human absorption rate. Many microorganisms, particularly beneficial microorganisms, including edible fungi, lactic acid bacteria, and yeast, are capable of absorbing and enriching calcium, a phenomenon that has been widely documented. This opens the door to the potential utilization of microorganisms as novel calcium enrichment carriers. However, the investigation of calcium-rich foods from microorganisms still faces many obstacles, including a poor understanding of calcium metabolic pathways in microorganisms, a relatively low calcium enrichment rate, and the slow growth of strains. Therefore, in order to promote the development of calcium-rich products from microorganisms, this paper provides an overview of the impacts of calcium addition on strain growth, calcium enrichment rate, antioxidant system, and secondary metabolite production. Additionally, it highlights calcium transport and enrichment mechanisms in microorganism cells and offers a detailed account of the progress made on calcium-binding proteins, calcium transport pathways, and calcium storage and release. This paper offers insights for further research on the relevant calcium enrichment in microorganism cells.

SERCA Modulators Reveal Distinct Signaling and Functional Roles of T Lymphocyte Ca2+ Stores

The allosteric SERCA (Sarcoplasmic/Endoplasmic Reticulum Ca2+-ATPase) activator CDN1163 has been recently added to the group of pharmacological tools for probing SERCA function. We chose to investigate the effects of the compound on T lymphocyte Ca2+ stores, using the well-described Jurkat T lymphocyte as a reliable cell system for Ca2+ signaling pathways. Our study identified the lowest concentrations of the SERCA inhibitors thapsigargin (TG) and 2,5-di-(tert butyl)-1,4-benzohydroquinone (tBHQ) capable of releasing Ca2+, permitting the differentiation of the TG-sensitive SERCA 2b Ca2+ store from the tBHQ-sensitive SERCA 3 Ca2+ store. We proceeded to test the effects of CDN1163 on Ca2+ stores, examining specific actions on the SERCA 2b and SERCA 3 Ca2+ pools using our low-dose SERCA blocker regimen. In contrast to previous work, we find CDN1163 exerts complex time-sensitive and SERCA isoform-specific actions on Ca2+ stores. Surprisingly, short-term exposure (0-30 min) to CDN1163 perturbs T cell Ca2+ stores by suppressing Ca2+ uptake with diminished Ca2+ release from the SERCA 2b-controlled store. Concomitantly, we find evidence for a SERCA-activating effect of CDN1163 on the SERCA-3 regulated store, given the observation of increased Ca2+ release inducible by low-dose tBHQ. Intriguingly, longer-term (>12 h) CDN1163 exposure reversed this pattern, with increased Ca2+ release from SERCA 2b-regulated pools yet decreased Ca2+ release responses from the tBHQ-sensitive SERCA 3 pool. Indeed, this remodeling of SERCA 2b Ca2+ stores with longer-term CDN1163 exposure also translated into the compound's ability to protect Jurkat T lymphocytes from TG but not tBHQ-induced growth suppression.

Newer mitochondrial dynamics and their role of calcium signalling in liver regeneration

Liver regeneration is a crucial process involved in cellular proliferation, differentiation, and tissue repair. Calcium signaling impact key pathways like hepatocyte growth factor-Met-tyrosine kinase (HGF-Met) transduction pathway, the epidermal growth factor receptor (EGFR) signaling and Ca-mediated nuclear SKHep1 cell proliferation pathway. Intracellular hepatocyte calcium stores are considered as base for the induction of ca-mediated regeneration process. Calcium signaling interplays with HGF, TGF-β, and NF-κB signaling, influence stem cell behavior and triggers MAPK cascade. The mitochondria calcium is impacting on liver rejuvenation by regulating apoptosis and cell division. In conclusion, it is stated that calcium-signaling holds promise for therapeutic liver interventions.

New Small-Molecule SERCA Inhibitors Enhance Treatment Efficacy in Lenvatinib-Resistant Papillary Thyroid Cancer

Papillary thyroid cancer (PTC) is one of the most treatable forms of cancer, with many cases being fully curable. However, resistance to anticancer drugs often leads to metastasis or recurrence, contributing to the failure of cancer therapy and, ultimately, patient mortality. The mechanisms underlying molecular differences in patients with metastatic or recurrent PTC, particularly those resistant to anticancer drugs through epigenetic reprogramming, remain poorly understood. Consequently, refractory PTC presents a critical challenge, and effective therapeutic strategies are urgently needed. Therefore, this study aimed to identify small-molecule inhibitors to enhance treatment efficacy in lenvatinib-resistant PTC. We observed an increase in sarco/endoplasmic reticulum calcium ATPase (SERCA) levels in patient-derived lenvatinib-resistant PTC cells compared with lenvatinib-sensitive ones, highlighting its potential as a therapeutic target. We subsequently identified two SERCA inhibitors [candidates 40 (isoflurane) and 42 (ethacrynic acid)] through in silico screening. These candidates demonstrated significant tumor shrinkage in a xenograft tumor model and reduced cell viability in patient-derived lenvatinib-resistant PTC cells when used in combination with lenvatinib. Our findings have potential clinical value for the development of new combination therapies to effectively target highly malignant, anticancer drug-resistant cancers.

Calotropin attenuates ischemic heart failure after myocardial infarction by modulating SIRT1/FOXD3/SERCA2a pathway

Heart failure (HF) represents the terminal stage of cardiovascular diseases, with limited therapeutic options currently available. Calotropin (CAL), a cardenolide isolated from Calotropis gigantea, exhibits a similar chemical structure and inhibitory effect on Na+/K+-ATPase to digoxin, a positive inotropic drugs used in heart failure treatment. However, the specific effect of calotropin in ischemic HF (IHF) remains unknown. The objective of this study is to assess the anti-HF effect and clarify its underlying mechanisms. The left anterior descending (LAD) artery ligation on Male Sprague-Dawley (SD) rats was used to construct ischemic HF model. Daily administration of CAL at 0.05 mg/kg significantly enhanced ejection fraction (EF) and fractional shortening (FS), while inhibiting cardiac fibrosis in IHF rats. CAL reduced the OGD/R-induced H9c2 cell injury. Furthermore, CAL upregulated the expression of SERCA2a and SIRT1. The cardioprotective effect of CAL against IHF was abrogated in the presence of the SIRT1 inhibitor EX527. Notably, we identified FOXD3 as a pivotal transcription factor mediating CAL-induced SERCA2a regulation. CAL promoted the deacetylation and nuclear translocation of FOXD3 in a SIRT1-dependent manner. In conclusion, our study explores a novel mechanism of calotropin for improving cardiac dysfunction in ischemic heart failure by regulating SIRT1/FOXD3/SERCA2a pathway.

Transcriptome analysis of porcine oocytes during postovulatory aging

Decreased oocyte quality is a significant contributor to the decline in female fertility that accompanies aging in mammals. Oocytes rely on mRNA stores to support their survival and integrity during the protracted period of transcriptional dormancy as they await ovulation. However, the changes in mRNA levels and interactions that occur during porcine oocyte maturation and aging remain unclear. In this study, the mRNA expression profiles of porcine oocytes during the GV, MII, and aging (24 h after the MII stage) stages were explored by transcriptome sequencing to identify the key genes and pathways that affect oocyte maturation and postovulatory aging. The results showed that 10,929 genes were coexpressed in porcine oocytes during the GV stage, MII stage, and aging stage. In addition, 3037 genes were expressed only in the GV stage, 535 genes were expressed only in the MII stage, and 120 genes were expressed only in the aging stage. The correlation index between the GV and MII stages (0.535) was markedly lower than that between the MII and aging stages (0.942). A total of 3237 genes, which included 1408 upregulated and 1829 downregulated genes, were differentially expressed during porcine oocyte postovulatory aging (aging stage vs. MII stage). Key functional genes, including ATP2A1, ATP2A3, ATP2B2, NDUFS1, NDUFA2, NDUFAF3, SREBF1, CYP11A1, CYP3A29, GPx4, CCP110, STMN1, SPC25, Sirt2, SYCP3, Fascin1/2, PFN1, Cofilin, Tmod3, FLNA, LRKK2, CHEK1/2, DDB1/2, DDIT4L, and TONSL, and key molecular pathways, such as the calcium signaling pathway, MAPK signaling pathway, TGF-β signaling pathway, PI3K/Akt signaling pathway, FoxO signaling pathway, gap junctions, and thermogenesis, were found in abundance during porcine postovulatory aging. These genes are mainly involved in the regulation of many biological processes, such as oxidative stress, calcium homeostasis, mitochondrial function, and lipid peroxidation, during porcine oocyte postovulatory aging. These results contribute to a more in-depth understanding of the biological changes, key regulatory genes and related biological pathways that are involved in oocyte aging and provide a theoretical basis for improving the efficiency of porcine embryo production in vitro and in vivo.

SARS-CoV-2 envelope protein alters calcium signaling via SERCA interactions

The clinical management of severe COVID-19 cases is not yet well resolved. Therefore, it is important to identify and characterize cell signaling pathways involved in virus pathogenesis that can be targeted therapeutically. Envelope (E) protein is a structural protein of the virus, which is known to be highly expressed in the infected host cell and is a key virulence factor; however, its role is poorly characterized. The E protein is a single-pass transmembrane protein that can assemble into a pentamer forming a viroporin, perturbing Ca2+ homeostasis. Because it is structurally similar to regulins such as, for example, phospholamban, that regulate the sarco/endoplasmic reticulum calcium ATPases (SERCA), we investigated whether the SARS-CoV-2 E protein affects the SERCA system as an exoregulin. Using FRET experiments we demonstrate that E protein can form oligomers with regulins, and thus can alter the monomer/multimer regulin ratio and consequently influence their interactions with SERCAs. We also confirm that a direct interaction between E protein and SERCA2b results in a decrease in SERCA-mediated ER Ca2+ reload. Structural modeling of the complexes indicates an overlapping interaction site for E protein and endogenous regulins. Our results reveal novel links in the host-virus interaction network that play an important role in viral pathogenesis and may provide a new therapeutic target for managing severe inflammatory responses induced by SARS-CoV-2.

Mitochondrial calcium uniporter complex: Unveiling the interplay between its regulators and calcium homeostasis

The mitochondrial calcium uniporter complex (MCUc), serving as the specific channel for calcium influx into the mitochondrial matrix, is integral to calcium homeostasis and cellular integrity. Given its importance, ongoing research spans various disease models to understand the properties of the MCUc in pathophysiological contexts, but reported a different conclusion. Therefore, this review delves into the profound connection between MCUc-mediated calcium transients and cellular signaling pathways, mitochondrial dynamics, metabolism, and cell death. Additionally, we shed light on the recent advancements concerning the structural intricacies and auxiliary components of the MCUc in both resting and activated states. Furthermore, emphasis is placed on novel extrinsic and intrinsic regulators of the MCUc and their therapeutic implications across a spectrum of diseases. Meanwhile, we employed molecular docking simulations and identified candidate traditional Chinese medicine components with potential binding sites to the MCUc, potentially offering insights for further research on MCUc modulation.

Calcium signaling crosstalk between the endoplasmic reticulum and mitochondria, a new drug development strategies of kidney diseases

Calcium (Ca2+) acts as a second messenger and constitutes a complex and large information exchange system between the endoplasmic reticulum (ER) and mitochondria; this process is involved in various life activities, such as energy metabolism, cell proliferation and apoptosis. Increasing evidence has suggested that alterations in Ca2+ crosstalk between the ER and mitochondria, including alterations in ER and mitochondrial Ca2+ channels and related Ca2+ regulatory proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), inositol 1,4,5-trisphosphate receptor (IP3R), and calnexin (CNX), are closely associated with the development of kidney disease. Therapies targeting intracellular Ca2+ signaling have emerged as an emerging field in the treatment of renal diseases. In this review, we focused on recent advances in Ca2+ signaling, ER and mitochondrial Ca2+ monitoring methods and Ca2+ homeostasis in the development of renal diseases and sought to identify new targets and insights for the treatment of renal diseases by targeting Ca2+ channels or related Ca2+ regulatory proteins.

Heat stress induces calcium dyshomeostasis to subsequent cognitive impairment through ERS-mediated apoptosis via SERCA/PERK/eIF2α pathway

Heat exposure is an environmental stressor that has been associated with cognitive impairment. However, the neural mechanisms that underlie this phenomenon have yet to be extensively investigated. The Morris water maze test was utilized to assess cognitive performance. RNA sequencing was employed to discover the primary regulators and pathological pathways involved in cognitive impairment caused by heat. Before heat exposure in vivo and in vitro, activation of the sarco/endoplasmic reticulum (SR/ER) calcium (Ca2+)-ATPase (SERCA) was achieved by CDN1163. Hematoxylin-Eosin, Nissl staining, calcium imaging, transmission electron microscopy, western blot, and immunofluorescence were utilized to visualize histological changes, intracellular calcium levels, endoplasmic reticulum stress (ERS) markers, apoptosis, and synaptic proteins alterations. Heat stress (HS) significantly induced cognitive decline and neuronal damage in mice. By the transcriptome sequencing between control (n = 5) and heat stress (n = 5) mice in hippocampal tissues, we identified a reduction in the expression of the atp2a gene encoding SERCA, accompanied by a corresponding decrease in its protein level. Consequently, this dysregulation resulted in an excessive accumulation of intracellular calcium ions. Furthermore, HS exposure also activated ERS and apoptosis, as evidenced by the upregulation of p-PERK, p-eIF2α, CHOP, and caspase-3. Consistently, a reduction in postsynaptic density protein 95 (PSD95) and synaptophysin (SYN) expressions indicated modifications in synaptic function. Notably, the impacts on neurons caused by HS were found to be mitigated by CDN1163 treatment both in vivo and in vitro. Additionally, SERCA-mediated ERS-induced apoptosis was attenuated by GSK2606414 treatment via inhibiting PERK-eIF2α-CHOP axis that not only curtailed the level of caspase-3 but also elevated the levels of PSD95 and SYN. These findings highlight the significant impact of heat stress on cognitive impairment, and further elucidate the underlying mechanism involving SERCA/PERK/eIF2α pathway.

Based on systematic druggable genome-wide Mendelian randomization identifies therapeutic targets for diabetes

Purpose

Diabetes and its complications cause a heavy burden of disease worldwide. In recent years, Mendelian randomization (MR) has been widely used to discover the pathogenesis and epidemiology of diseases, as well as to discover new therapeutic targets. Therefore, based on systematic "druggable" genomics, we aim to identify new therapeutic targets for diabetes and analyze its pathophysiological mechanisms to promote its new therapeutic strategies.

Material and method

We used double sample MR to integrate the identified druggable genomics to evaluate the causal effect of quantitative trait loci (eQTLs) expressed by druggable genes in blood on type 1 and 2 diabetes (T1DM and T2DM). Repeat the study using different data sources on diabetes and its complications to verify the identified genes. Not only that, we also use Bayesian co-localization analysis to evaluate the posterior probabilities of different causal variations, shared causal variations, and co-localization probabilities to examine the possibility of genetic confounding. Finally, using diabetes markers with available genome-wide association studies data, we evaluated the causal relationship between established diabetes markers to explore possible mechanisms.

Result

Overall, a total of 4,477 unique druggable genes have been gathered. After filtering using methods such as Bonferroni significance (P<1.90e-05), the MR Steiger directionality test, Bayesian co-localization analysis, and validation with different datasets, Finally, 7 potential druggable genes that may affect the results of T1DM and 7 potential druggable genes that may affect the results of T2DM were identified. Reverse MR suggests that C4B may play a bidirectional role in the pathogenesis of T1DM, and none of the other 13 target genes have a reverse causal relationship. And the 7 target genes in T2DM may each affect the biomarkers of T2DM to mediate the pathogenesis of T2DM.

Conclusion

This study provides genetic evidence supporting the potential therapeutic benefits of targeting seven druggable genes, namely MAP3K13, KCNJ11, REG4, KIF11, CCNE2, PEAK1, and NRBP1, for T2DM treatment. Similarly, targeting seven druggable genes, namely ERBB3, C4B, CD69, PTPN22, IL27, ATP2A1, and LT-β, has The potential therapeutic benefits of T1DM treatment. This will provide new ideas for the treatment of diabetes and also help to determine the priority of drug development for diabetes.

Unraveling the Connection: Pain and Endoplasmic Reticulum Stress

Pain is a complex and multifaceted experience. Recent research has increasingly focused on the role of endoplasmic reticulum (ER) stress in the induction and modulation of pain. The ER is an essential organelle for cells and plays a key role in protein folding and calcium dynamics. Various pathological conditions, such as ischemia, hypoxia, toxic substances, and increased protein production, may disturb protein folding, causing an increase in misfolding proteins in the ER. Such an overload of the folding process leads to ER stress and causes the unfolded protein response (UPR), which increases folding capacity in the ER. Uncompensated ER stress impairs intracellular signaling and cell function, resulting in various diseases, such as diabetes and degenerative neurological diseases. ER stress may be a critical universal mechanism underlying human diseases. Pain sensations involve the central as well as peripheral nervous systems. Several preclinical studies indicate that ER stress in the nervous system is enhanced in various painful states, especially in neuropathic pain conditions. The purpose of this narrative review is to uncover the intricate relationship between ER stress and pain, exploring molecular pathways, implications for various pain conditions, and potential therapeutic strategies.

SERCA2 dysfunction triggers hypertension by interrupting mitochondrial homeostasis and provoking oxidative stress

BACKGROUND AND AIM

Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is critical in maintaining Ca2+ homeostasis. The cysteine 674 (C674) is the key redox regulatory cysteine in regulating SERCA2 activity, which is irreversibly oxidized in the renal cortex of hypertensive mice. We have reported that the substitution of C674 by serine causes SERCA2 dysfunction and increases blood pressure by induction of endoplasmic reticulum stress (ERS). This study is to explore whether the dysfunction of SERCA2 causes hypertension by interrupting mitochondrial homeostasis and inducing oxidative stress.

METHODS & RESULTS

We used heterozygous SERCA2 C674S gene mutation knock-in (SKI) mice, where one copy of C674 was substituted by serine to represent partial C674 oxidation. In renal proximal tubule (RPT) cells, the substitution of C674 by serine decreased mitochondrial Ca2+ content, increased mitochondrial membrane potential, ATP content, and reactive oxygen species (ROS), which could be reversed by ERS inhibitor 4-phenylbutyric acid or SERCA2 agonist CDN1163. In SKI RPT cells, the redox modulator Tempol alleviated oxidative stress, downregulated the protein expression of ERS markers and soluble epoxide hydrolase, upregulated the protein expression of dopamine D1 receptor, and reduced Na+/K+- ATPase activity. In SKI mice, SERCA2 agonists CDN1163 and [6]-Gingerol, or the redox modulator Tempol increased urine output and lowered blood pressure.

CONCLUSION

The irreversible oxidation of C674 is not only an indicator of increased ROS, but also further inducing oxidative stress to cause hypertension. Activation of SERCA2 or inhibition of oxidative stress is beneficial to alleviate hypertension caused by SERCA2 dysfunction.

Dual effect of polyaromatic hydrocarbons on sarco(endo)plasmic reticulum calcium ATPase (SERCA) activity of a teleost fish (Oncorhynchus mykiss)

Polycyclic aromatic hydrocarbons (PAHs) are embryo- and cardiotoxic to fish that might be associated with improper intracellular Ca2+ management. Since sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) is a major regulator of intracellular Ca2+, the SERCA activity and the contractile properties of rainbow trout (Oncorhynchus mykiss) ventricle were measured in the presence of 3- and 4-cyclic PAHs. In unfractionated ventricular homogenates, acute exposure of SERCA to 0.1-1.0 μM phenanthrene (Phe), retene (Ret), fluoranthene (Flu), or pyrene (Pyr) resulted in concentration-dependent increase in SERCA activity, except for the Flu exposure, with maximal effects of 49.7-83 % at 1 μM. However, PAH mixture did not affect the contractile parameters of trout ventricular strips. Similarly, all PAHs, except Ret, increased the myotomal SERCA activity, but with lower effect (27.8-40.8 % at 1 μM). To investigate the putative chronic effects of PAHs on SERCA, the atp2a2a gene encoding trout cardiac SERCA was expressed in human embryonic kidney (HEK) cells. Culture of HEK cells in the presence of 0.3-1.0 μM Phe, Ret, Flu, and Pyr for 4 days suppressed SERCA expression in a concentration-dependent manner, with maximal inhibition of 49 %, 65 %, 39 % (P < 0.05), and 18 % (P > 0.05), respectively at 1 μM. Current findings indicate divergent effects of submicromolar PAH concentrations on SERCA: stimulation of SERCA activity in acute exposure and inhibition of SERCA expression in chronic exposure. The depressed expression of SERCA is likely to contribute to the embryo- and cardiotoxicity of PAHs by depressing muscle function and altering gene expression.

The dynamic equilibrium between the protective and toxic effects of matrine in the development of liver injury: a systematic review and meta-analysis

Background: Matrine, an alkaloid derived from the dried roots of Sophora flavescens Aiton, has been utilized for the treatment of liver diseases, but its potential hepatotoxicity raises concerns. However, the precise condition and mechanism of action of matrine on the liver remain inconclusive. Therefore, the objective of this systematic review and meta-analysis is to comprehensively evaluate both the hepatoprotective and hepatotoxic effects of matrine and provide therapeutic guidance based on the findings. Methods: The meta-analysis systematically searched relevant preclinical literature up to May 2023 from eight databases, including PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure, WanFang Med Online, China Science and Technology Journal Database, and China Biomedical Literature Service System. The CAMARADES system assessed the quality and bias of the evidence. Statistical analysis was conducted using STATA, which included the use of 3D maps and radar charts to display the effects of matrine dosage and frequency on hepatoprotection and hepatotoxicity. Results: After a thorough screening, 24 studies involving 657 rodents were selected for inclusion. The results demonstrate that matrine has bidirectional effects on ALT and AST levels, and it also regulates SOD, MDA, serum TG, serum TC, IL-6, TNF-α, and CAT levels. Based on our comprehensive three-dimensional analysis, the optimal bidirectional effective dosage of matrine ranges from 10 to 69.1 mg/kg. However, at a dose of 20-30 mg/kg/d for 0.02-0.86 weeks, it demonstrated high liver protection and low toxicity. The molecular docking analysis revealed the interaction between MT and SERCA as well as SREBP-SCAP complexes. Matrine could alter Ca2+ homeostasis in liver injury via multiple pathways, including the SREBP1c/SCAP, Notch/RBP-J/HES1, IκK/NF-κB, and Cul3/Rbx1/Keap1/Nrf2. Conclusion: Matrine has bidirectional effects on the liver at doses ranging from 10 to 69.1 mg/kg by influencing Ca2+ homeostasis in the cytoplasm, endoplasmic reticulum, Golgi apparatus, and mitochondria. Systematic review registration: https://inplasy.com/, identifier INPLASY202340114.

Bafilomycin A1 Molecular Effect on ATPase Activity of Subcellular Fraction of Human Colorectal Cancer and Rat Liver

Bafilomycin A1 inhibits V-type H+ ATPases on the molecular level, which acidifies endo-lysosomes. The main objective of the study was to assess the effect of bafilomycin A1 on Ca2+ content, NAADP-induced Ca2+ release, and ATPase activity in rat hepatocytes and human colon cancer samples. Chlortetracycline (CTC) was used for a quantitative measure of stored calcium in permeabilized rat hepatocytes. ATPase activity was determined by orthophosphate content released after ATP hydrolysis in subcellular post-mitochondrial fraction obtained from rat liver as well as from patients' samples of colon mucosa and colorectal cancer samples. In rat hepatocytes, bafilomycin A1 decreased stored Ca2+ and prevented the effect of NAADP on stored Ca2+. This effect was dependent on EGTA-Ca2+ buffers in the medium. Bafilomycin A1 significantly increased the activity of Ca2+ ATPases of endoplasmic reticulum (EPR), but not plasma membrane (PM) Ca2+ ATPases in rat liver. Bafilomycin A1 also prevented the effect of NAADP on these pumps. In addition, bafilomycin A1 reduced Na+/K+ ATPase activity and increased basal Mg2+ ATPase activity in the subcellular fraction of rat liver. Concomitant administration of bafilomycin A1 and NAADP enhanced these effects. Bafilomycin A1 increased the activity of the Ca2+ ATPase of EPR in the subcellular fraction of normal human colon mucosa and also in colon cancer tissue samples. In contrast, it decreased Ca2+ ATPase PM activity in samples of normal human colon mucosa and caused no changes in colon cancer. Bafilomycin A1 decreased Na+/K+ ATPase activity and increased basal Mg2+ ATPase activity in normal colon mucosa samples and in human colon cancer samples. It can be concluded that bafilomycin A1 targets NAADP-sensitive acidic Ca2+ stores, effectively modulates ATPase activity, and assumes the link between acidic stores and EPR. Bafilomycin A1 may be useful for cancer therapy.

Congenital Hyperinsulinism in Humans and Insulin Secretory Dysfunction in Mice Caused by Biallelic DNAJC3 Variants

The BiP co-chaperone DNAJC3 protects cells during ER stress. In mice, the deficiency of DNAJC3 leads to beta-cell apoptosis and the gradual onset of hyperglycemia. In humans, biallelic DNAJC3 variants cause a multisystem disease, including early-onset diabetes mellitus. Recently, hyperinsulinemic hypoglycemia (HH) has been recognized as part of this syndrome. This report presents a case study of an individual with HH caused by DNAJC3 variants and provides an overview of the metabolic phenotype of individuals with HH and DNAJC3 variants. The study demonstrates that HH may be a primary symptom of DNAJC3 deficiency and can persist until adolescence. Additionally, glycemia and insulin release were analyzed in young DNACJ3 knockout (K.O.) mice, which are equivalent to human infants. In the youngest experimentally accessible age group of 4-week-old mice, the in vivo glycemic phenotype was already dominated by a reduced total insulin secretion capacity. However, on a cellular level, the degree of insulin release of DNAJC3 K.O. islets was higher during periods of increased synthetic activity (high-glucose stimulation). We propose that calcium leakage from the ER into the cytosol, due to disrupted DNAJC3-controlled gating of the Sec61 channel, is the most likely mechanism for HH. This is the first genetic mechanism explaining HH solely by the disruption of intracellular calcium homeostasis. Clinicians should screen for HH in DNAJC3 deficiency and consider DNAJC3 variants in the differential diagnosis of congenital hyperinsulinism.

CDN1163 alleviates SERCA2 dysfunction-induced pulmonary vascular remodeling by inhibiting the phenotypic transition of pulmonary artery smooth muscle cells

BACKGROUND AND PURPOSE

Substitution of Cys674 (C674) in the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) causes SERCA2 dysfunction which leads to activated inositol requiring enzyme 1 alpha (IRE1α) and spliced X-box binding protein 1 (XBP1s) pathway accelerating cell proliferation of pulmonary artery smooth muscle cells (PASMCs) followed by significant pulmonary vascular remodeling resembling human pulmonary hypertension. Based on this knowledge, we intend to investigate other potential mechanisms involved in SERCA2 dysfunction-induced pulmonary vascular remodeling.

EXPERIMENTAL APPROACH

Heterozygous SERCA2 C674S knock-in (SKI) mice of which half of cysteine in 674 was substituted by serine to mimic the partial irreversible oxidation of C674 were used. The lungs of SKI mice and their littermate wild-type mice were collected for PASMC culture, protein expression, and pulmonary vascular remodeling analysis.

RESULTS

SERCA2 dysfunction increased intracellular Ca2+ levels, which activated Ca2+-dependent calcineurin (CaN) and promoted the nuclear translocation and protein expression of the nuclear factor of activated T-lymphocytes 4 (NFAT4) in an IRE1α/XBP1s pathway-independent manner. In SKI PASMCs, the scavenge of intracellular Ca2+ by BAPTA-AM or inhibition of CaN by cyclosporin A can prevent PASMC phenotypic transition. CDN1163, a SERCA2 agonist, suppressed the activation of CaN/NFAT4 and IRE1α/XBP1s pathways, reversed the protein expression of PASMC phenotypic transition markers and cell cycle-related proteins, and inhibited cell proliferation and migration when given to SKI PASMCs. Furthermore, CDN1163 ameliorated pulmonary vascular remodeling in SKI mice.

CONCLUSIONS AND IMPLICATIONS

SERCA2 dysfunction promotes PASMC phenotypic transition and pulmonary vascular remodeling by multiple mechanisms, which could be improved by SERCA2 agonist CDN1163.

Achilles' Heel-The Significance of Maintaining Microenvironmental Homeostasis in the Nucleus Pulposus for Intervertebral Discs

The dysregulation of intracellular and extracellular environments as well as the aberrant expression of ion channels on the cell membrane are intricately linked to a diverse array of degenerative disorders, including intervertebral disc degeneration. This condition is a significant contributor to low back pain, which poses a substantial burden on both personal quality of life and societal economics. Changes in the number and function of ion channels can disrupt the water and ion balance both inside and outside cells, thereby impacting the physiological functions of tissues and organs. Therefore, maintaining ion homeostasis and stable expression of ion channels within the cellular microenvironment may prove beneficial in the treatment of disc degeneration. Aquaporin (AQP), calcium ion channels, and acid-sensitive ion channels (ASIC) play crucial roles in regulating water, calcium ions, and hydrogen ions levels. These channels have significant effects on physiological and pathological processes such as cellular aging, inflammatory response, stromal decomposition, endoplasmic reticulum stress, and accumulation of cell metabolites. Additionally, Piezo 1, transient receptor potential vanilloid type 4 (TRPV4), tension response enhancer binding protein (TonEBP), potassium ions, zinc ions, and tungsten all play a role in the process of intervertebral disc degeneration. This review endeavors to elucidate alterations in the microenvironment of the nucleus pulposus during intervertebral disc degeneration (IVDD), with a view to offer novel insights and approaches for exploring therapeutic interventions against disc degeneration.

Discovery of New Anti-Cancer Agents against Patient-Derived Sorafenib-Resistant Papillary Thyroid Cancer

Thyroid cancer is the most well-known type of endocrine cancer that is easily treatable and can be completely cured in most cases. Nonetheless, anti-cancer drug-resistant metastasis or recurrence may occur and lead to the failure of cancer therapy, which eventually leads to the death of a patient with cancer. This study aimed to detect novel thyroid cancer target candidates based on validating and identifying one of many anti-cancer drug-resistant targets in patient-derived sorafenib-resistant papillary thyroid cancer (PTC). We focused on targeting the sarco/endoplasmic reticulum calcium ATPase (SERCA) in patient-derived sorafenib-resistant PTC cells compared with patient-derived sorafenib-sensitive PTC cells. We discovered novel SERCA inhibitors (candidates 33 and 36) by virtual screening. These candidates are novel SERCA inhibitors that lead to remarkable tumor shrinkage in a xenograft tumor model of sorafenib-resistant patient-derived PTC cells. These results are clinically valuable for the progression of novel combinatorial strategies that facultatively and efficiently target extremely malignant cancer cells, such as anti-cancer drug-resistant PTC cells.

Metabolic and Genetic Association of Vitamin D with Calcium Signaling and Insulin Resistance

Various evidences have unveiled the significance of Vitamin D in diverse processes which include its action in prevention of immune dysfunction, cancer and cardiometabolic disorders. Studies have confirmed the function of VD in controlling the expression of approximately nine hundred genes including gene expression of insulin. VD insufficiency may be linked with the pathogenesis of diseases that are associated with insulin resistance (IR) including diabetes as well as obesity. Thus, VD lowers IR-related disorders such as inflammation and oxidative stress. This review provides an insight regarding the molecular mechanism manifesting, how insufficiency of VD may be connected with the IR and diabetes. It also discusses the effect of VD in maintaining the Ca2+ levels in beta cells of the pancreas and in the tissues that are responsive to insulin.

The plant pathogenic bacterium Candidatus Liberibacter solanacearum induces calcium-regulated autophagy in midgut cells of its insect vector Bactericera trigonica

Autophagy plays an important role against pathogen infection in many organisms; however, little has been done with regard to vector-borne plant and animal pathogens, that sometimes replicate and cause deleterious effects in their vectors. Candidatus Liberibacter solanacearum (CLso) is a fastidious gram-negative phloem-restricted plant pathogen and vectored by the carrot psyllid, Bactericera trigonica. The plant disease caused by this bacterium is called carrot yellows and has recently gained much importance due to worldwide excessive economical losses. Here, we demonstrate that calcium ATPase, cytosolic calcium, and most importantly Beclin-1 have a role in regulating autophagy and its association with Liberibacter inside the psyllid. The presence of CLso generates reactive oxygen species and induces the expression of detoxification enzymes in the psyllid midguts, a main site for bacteria transmission. CLso also induces the expression of both sarco/endoplasmic reticulum Ca2+pump (SERCA) and 1,4,5-trisphosphate receptors (ITPR) in midguts, resulting in high levels of calcium in the cellular cytosol. Silencing these genes individually disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and subsequently on Liberibacter persistence and transmission. Inhibiting Beclin1-phosphorylation through different calcium-induced kinases altered the expression of autophagy and CLso titers and persistence. Based on our results obtained from the midgut, we suggest the existence of a direct correlation between cytosolic calcium levels, autophagy, and CLso persistence and transmission by the carrot psyllid. IMPORTANCE Plant diseases caused by vector-borne Liberibacter species are responsible for the most important economic losses in many agricultural sectors. Preventing these diseases relies mostly on chemical sprays against the insect vectors. Knowledge-based interference with the bacteria-vector interaction remains a promising approach as a sustainable solution. For unravelling how Liberibacter exploits molecular pathways in its insect vector for transmission, here, we show that the bacterium manipulates calcium levels on both sides of the endoplasmic reticulum membrane, resulting in manipulating autophagy. Silencing genes associated with these pathways disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and Liberibacter transmission. These results demonstrate major pathways that could be exploited for manipulating and controlling the disease transmission.

Phosphoinositides and intracellular calcium signaling: novel insights into phosphoinositides and calcium coupling as negative regulators of cellular signaling

Intracellular calcium (Ca2+) and phosphoinositides (PIPs) are crucial for regulating cellular activities such as metabolism and cell survival. Cells maintain precise intracellular Ca2+ and PIP levels via the actions of a complex system of Ca2+ channels, transporters, Ca2+ ATPases, and signaling effectors, including specific lipid kinases, phosphatases, and phospholipases. Recent research has shed light on the complex interplay between Ca2+ and PIP signaling, suggesting that elevated intracellular Ca2+ levels negatively regulate PIP signaling by inhibiting the membrane localization of PIP-binding proteins carrying specific domains, such as the pleckstrin homology (PH) and Ca2+-independent C2 domains. This dysregulation is often associated with cancer and metabolic diseases. PIPs recruit various proteins with PH domains to the plasma membrane in response to growth hormones, which activate signaling pathways regulating metabolism, cell survival, and growth. However, abnormal PIP signaling in cancer cells triggers consistent membrane localization and activation of PIP-binding proteins. In the context of obesity, an excessive intracellular Ca2+ level prevents the membrane localization of the PIP-binding proteins AKT, IRS1, and PLCδ via Ca2+-PIPs, contributing to insulin resistance and other metabolic diseases. Furthermore, an excessive intracellular Ca2+ level can cause functional defects in subcellular organelles such as the endoplasmic reticulum (ER), lysosomes, and mitochondria, causing metabolic diseases. This review explores how intracellular Ca2+ overload negatively regulates the membrane localization of PIP-binding proteins.

NNAT is a novel mediator of oxidative stress that suppresses ER + breast cancer

BACKGROUND

Neuronatin (NNAT) was recently identified as a novel mediator of estrogen receptor-positive (ER+) breast cancer cell proliferation and migration, which correlated with decreased tumorigenic potential and prolonged patient survival. However, despite these observations, the molecular and pathophysiological role(s) of NNAT in ER + breast cancer remains unclear. Based on high protein homology with phospholamban, we hypothesized that NNAT mediates the homeostasis of intracellular calcium [Ca2+]i levels and endoplasmic reticulum (EndoR) function, which is frequently disrupted in ER + breast cancer and other malignancies.

METHODS

To evaluate the role of NNAT on [Ca2+]i homeostasis, we used a combination of bioinformatics, gene expression and promoter activity assays, CRISPR gene manipulation, pharmacological tools and confocal imaging to characterize the association between ROS, NNAT and calcium signaling.

RESULTS

Our data indicate that NNAT localizes predominantly to EndoR and lysosome, and genetic manipulation of NNAT levels demonstrated that NNAT modulates [Ca2+]i influx and maintains Ca2+ homeostasis. Pharmacological inhibition of calcium channels revealed that NNAT regulates [Ca2+]i levels in breast cancer cells through the interaction with ORAI but not the TRPC signaling cascade. Furthermore, NNAT is transcriptionally regulated by NRF1, PPARα, and PPARγ and is strongly upregulated by oxidative stress via the ROS and PPAR signaling cascades.

CONCLUSION

Collectively, these data suggest that NNAT expression is mediated by oxidative stress and acts as a regulator of Ca2+ homeostasis to impact ER + breast cancer proliferation, thus providing a molecular link between the longstanding observation that is accumulating ROS and altered Ca2+ signaling are key oncogenic drivers of cancer.

Biochemical and proteomic insights into sarcoplasmic reticulum Ca2+-ATPase complexes in skeletal muscles

INTRODUCTION

Skeletal muscles contain large numbers of high-molecular-mass protein complexes in elaborate membrane systems. Integral membrane proteins are involved in diverse cellular functions including the regulation of ion handling, membrane homeostasis, energy metabolism and force transmission.

AREAS COVERED

The proteomic profiling of membrane proteins and large protein assemblies in skeletal muscles are outlined in this article. This includes a critical overview of the main biochemical separation techniques and the mass spectrometric approaches taken to study membrane proteins. As an illustrative example of an analytically challenging large protein complex, the proteomic detection and characterization of the Ca2+-ATPase of the sarcoplasmic reticulum is discussed. The biological role of this large protein complex during normal muscle functioning, in the context of fiber type diversity and in relation to mechanisms of physiological adaptations and pathophysiological abnormalities is evaluated from a proteomics perspective.

EXPERT OPINION

Mass spectrometry-based muscle proteomics has decisively advanced the field of basic and applied myology. Although it is technically challenging to study membrane proteins, innovations in protein separation methodology in combination with sensitive mass spectrometry and improved systems bioinformatics has allowed the detailed proteomic detection and characterization of skeletal muscle membrane protein complexes, such as Ca2+-pump proteins of the sarcoplasmic reticulum.

Isolation and Biological Activity of Iezoside and Iezoside B, SERCA Inhibitors from Floridian Marine Cyanobacteria

Marine cyanobacteria are a rich source of bioactive natural products. Here, we report the isolation and structure elucidation of the previously reported iezoside (1) and its C-31 O-demethyl analogue, iezoside B (2), from a cyanobacterial assemblage collected at Loggerhead Key in the Dry Tortugas, Florida. The two compounds have a unique skeleton comprised of a peptide, a polyketide and a modified sugar unit. The compounds were tested for cytotoxicity and effects on intracellular calcium. Both compounds exhibited cytotoxic activity with an IC50 of 1.5 and 3.0 μΜ, respectively, against A549 lung carcinoma epithelial cells and 1.0 and 2.4 μΜ against HeLa cervical cancer cells, respectively. In the same cell lines, compounds 1 and 2 show an increase in cytosolic calcium with approximate EC50 values of 0.3 and 0.6 μΜ in A549 cells and 0.1 and 0.5 μΜ, respectively, in HeLa cells, near the IC50 for cell viability, suggesting that the increase in cytosolic calcium is functionally related to the cytotoxicity of the compounds and consistent with their activity as SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase) inhibitors. The structure-activity relationship provides evidence that structural changes in the sugar unit may be tolerated, and the activity is tunable. This finding has implications for future analogue synthesis and target interaction studies.

Endoplasmic reticulum homeostasis: a potential target for diabetic nephropathy

The endoplasmic reticulum (ER) is the most vigorous organelle in intracellular metabolism and is involved in physiological processes such as protein and lipid synthesis and calcium ion transport. Recently, the abnormal function of the ER has also been reported to be involved in the progression of kidney disease, especially in diabetic nephropathy (DN). Here, we reviewed the function of the ER and summarized the regulation of homeostasis through the UPR and ER-phagy. Then, we also reviewed the role of abnormal ER homeostasis in residential renal cells in DN. Finally, some ER stress activators and inhibitors were also summarized, and the possibility of maintaining ER homeostasis as a potential therapeutic target for DN was discussed.

Calcium Homeostasis, Transporters, and Blockers in Health and Diseases of the Cardiovascular System

Calcium is a highly positively charged ionic species. It regulates all cell types' functions and is an important second messenger that controls and triggers several mechanisms, including membrane stabilization, permeability, contraction, secretion, mitosis, intercellular communications, and in the activation of kinases and gene expression. Therefore, controlling calcium transport and its intracellular homeostasis in physiology leads to the healthy functioning of the biological system. However, abnormal extracellular and intracellular calcium homeostasis leads to cardiovascular, skeletal, immune, secretory diseases, and cancer. Therefore, the pharmacological control of calcium influx directly via calcium channels and exchangers and its outflow via calcium pumps and uptake by the ER/SR are crucial in treating calcium transport remodeling in pathology. Here, we mainly focused on selective calcium transporters and blockers in the cardiovascular system.

Rats lacking Ucp1 present a novel translational tool for the investigation of thermogenic adaptation during cold challenge

AIM

Valuable studies have tested the role of UCP1 on body temperature maintenance in mice, and we sought to knockout Ucp1 in rats (Ucp1-/- ) to provide insight into thermogenic mechanisms in larger mammals.

METHODS

We used CRISPR/Cas9 technology to create Ucp1-/- rats. Body weight and adiposity were measured, and rats were subjected to indirect calorimetry. Rats were maintained at room temperature or exposed to 4°C for either 24 h or 14 days. Analyses of brown and white adipose tissue and skeletal muscle were conducted via histology, western blot comparison of oxidative phosphorylation proteins, and qPCR to compare mitochondrial DNA levels and mRNA expression profiles. RNA-seq was performed in skeletal muscle.

RESULTS

Ucp1-/- rats withstood 4°C for 14 days, but core temperature steadily declined. All rats lost body weight after 14 days at 4°C, but controls increased food intake more robustly than Ucp1-/- rats. Brown adipose tissue showed signs of decreased activity in Ucp1-/- rats, while mitochondrial lipid metabolism markers in white adipose tissue and skeletal muscle were increased. Ucp1-/- rats displayed more visible shivering and energy expenditure than controls at 4°C. Skeletal muscle transcriptomics showed more differences between genotypes at 23°C than at 4°C.

CONCLUSION

Room temperature presented sufficient cold stress to rats lacking UCP1 to activate compensatory thermogenic mechanisms in skeletal muscle, which were only activated in control rats following exposure to 4°C. These results provide novel insight into thermogenic responses to UCP1 deficiency; and highlight Ucp1-/- rats as an attractive translational model for the study of thermogenesis.

Anti-Cancer SERCA Inhibitors Targeting Sorafenib-Resistant Human Papillary Thyroid Carcinoma

Thyroid cancer is generally curable and, in many cases, can be completely treated, although it can sometimes recur after cancer therapy. Papillary thyroid cancer (PTC) is known as one of the most general subtypes of thyroid cancer, which take up nearly 80% of whole thyroid cancer. However, PTC may develop anti-cancer drug resistance via metastasis or recurrence, making it practically incurable. In this study, we propose a clinical approach that identifies novel candidates based on target identification and validation of numerous survival-involved genes in human sorafenib-sensitive and -resistant PTC. Consequently, we recognized a sarco/endoplasmic reticulum calcium ATPase (SERCA) in human sorafenib-resistant PTC cells. Based on the present results, we detected novel SERCA inhibitor candidates 24 and 31 via virtual screening. These SERCA inhibitors showed remarkable tumor shrinkage in the sorafenib-resistant human PTC xenograft tumor model. These consequences would be clinically worthwhile for the development of a new combinatorial strategy that effectively targets incredibly refractory cancer cells, such as cancer stem cells and anti-cancer drug-resistant cells.

Apoptotic proteins with non-apoptotic activity: expression and function in cancer

Apoptosis is a process of programmed cell death in which a cell commits suicide while maintaining the integrity and architecture of the tissue as a whole. Apoptosis involves activation of one of two major pathways: the extrinsic pathway, where extracellular pro-apoptotic signals, transduced through plasma membrane death receptors, activate a caspase cascade leading to apoptosis. The second, the intrinsic apoptotic pathway, where damaged DNA, oxidative stress, or chemicals, induce the release of pro-apoptotic proteins from the mitochondria, leading to the activation of caspase-dependent and independent apoptosis. However, it has recently become apparent that proteins involved in apoptosis also exhibit non-cell death-related physiological functions that are related to the cell cycle, differentiation, metabolism, inflammation or immunity. Such non-conventional activities were predominantly reported in non-cancer cells although, recently, such a dual function for pro-apoptotic proteins has also been reported in cancers where they are overexpressed. Interestingly, some apoptotic proteins translocate to the nucleus in order to perform a non-apoptotic function. In this review, we summarize the unconventional roles of the apoptotic proteins from a functional perspective, while focusing on two mitochondrial proteins: VDAC1 and SMAC/Diablo. Despite having pro-apoptotic functions, these proteins are overexpressed in cancers and this apparent paradox and the associated pathophysiological implications will be discussed. We will also present possible mechanisms underlying the switch from apoptotic to non-apoptotic activities although a deeper investigation into the process awaits further study.

Identification of calcium metabolism related score associated with the poor outcome in papillary thyroid carcinoma

Introduction

Papillary thyroid carcinoma is a type of thyroid cancer that exhibits significant variability in prognosis. Extensive research indicates that the impaired signaling of 1,25(OH)2D3-VDR may be a crucial factor in the development and progression of PTC.

Methods

To investigate this further, Integrated analysis mRNA expression information from The Cancer Genome Atlas and GEO, we compared gene expression in cancer and normal tissues and identified differentially expressed genes (DEGs). Through this analysis, we identified DEGs and calculated risk estimates for seven genetic markers.

Results

Subsequently, we constructed predictive models using LASSO-Cox regression to test the predictive value of these markers. Our results revealed that 64 calcium metabolism-related genes showed significant differences between tumor and normal tissues. Ten of the identified DEGs were significantly associated with overall survival, indicating their potential role in disease progression. Using the average risk score for the seven genetic markers, we divided patients into high- and low-risk groups. We found that patients in the low-risk group had significantly better overall survival than those in the high-risk group, highlighting the importance of these genetic markers in predicting prognosis. Further analysis using Cox regression demonstrated that the risk levels had independent predictive power. Additionally, we conducted functional analysis of the identified genetic markers, which showed significant differences in immune status between the two patient groups. We also investigated the effect of these calcium metabolism-related genes on thyroid cancer biological functions, immune microenvironment, and drug resistance.

Discussion

Our findings provide evidence of a novel genetic signature associated with calcium metabolism, which can predict prognosis in patients with PTC. These results may have significant implications for the development of new diagnostic and therapeutic approaches to improve outcomes for PTC patients.

The Meeting of Micropeptides with Major Ca2+ Pumps in Inner Membranes-Consideration of a New Player, SERCA1b

Calcium is a major signalling bivalent cation within the cell. Compartmentalization is essential for regulation of calcium mediated processes. A number of players contribute to intracellular handling of calcium, among them are the sarco/endoplasmic reticulum calcium ATP-ases (SERCAs). These molecules function in the membrane of ER/SR pumping Ca²⁺ from cytoplasm into the lumen of the internal store. Removal of calcium from the cytoplasm is essential for signalling and for relaxation of skeletal muscle and heart. There are three genes and over a dozen isoforms of SERCA in mammals. These can be potentially influenced by small membrane peptides, also called regulins. The discovery of micropeptides has increased in recent years, mostly because of the small ORFs found in long RNAs, annotated formerly as noncoding (lncRNAs). Several excellent works have analysed the mechanism of interaction of micropeptides with each other and with the best known SERCA1a (fast muscle) and SERCA2a (heart, slow muscle) isoforms. However, the array of tissue and developmental expressions of these potential regulators raises the question of interaction with other SERCAs. For example, the most abundant calcium pump in neonatal and regenerating skeletal muscle, SERCA1b has never been looked at with scrutiny to determine whether it is influenced by micropeptides. Further details might be interesting on the interaction of these peptides with the less studied SERCA1b isoform.

The Effects of Mechanical Load on Chondrogenic Responses of Bone Marrow Mesenchymal Stem Cells and Chondrocytes Encapsulated in Chondroitin Sulfate-Based Hydrogel

Articular cartilage is vulnerable to mechanical overload and has limited ability to restore lesions, which leads to the development of chronic diseases such as osteoarthritis (OA). In this study, the chondrogenic responses of human bone marrow mesenchymal stem cells (BMMSCs) and OA cartilage-derived chondrocytes in 3D chondroitin sulfate-tyramine/gelatin (CS-Tyr)/Gel) hydrogels with or without experimental mechanical load have been investigated. Chondrocytes were smaller in size, had slower proliferation rate and higher level of intracellular calcium (iCa²⁺) compared to BMMSCs. Under 3D chondrogenic conditions in CS-Tyr/Gel with or without TGF-β3, chondrocytes more intensively secreted cartilage oligomeric matrix protein (COMP) and expressed collagen type II (COL2A1) and aggrecan (ACAN) genes but were more susceptible to mechanical load compared to BMMSCs. ICa²⁺ was more stably controlled in CS-Tyr/Gel/BMMSCs than in CS-Tyr/Gel/chondrocytes ones, through the expression of L-type channel subunit CaV1.2 (CACNA1C) and Serca2 pump (ATP2A2) genes, and their balance was kept more stable. Due to the lower susceptibility to mechanical load, BMMSCs in CS-Tyr/Gel hydrogel may have an advantage over chondrocytes in application for cartilage regeneration purposes. The mechanical overload related cartilage damage in vivo and the vague regenerative processes of OA chondrocytes might be associated to the inefficient control of iCa²⁺ regulating channels.

Vitamin C Modes of Action in Calcium-Involved Signaling in the Brain

Vitamin C (ascorbic acid) is well known for its potent antioxidant properties, as it can neutralize ROS and free radicals, thereby protecting cellular elements from oxidative stress. It predominantly exists as an ascorbate anion and after oxidation to dehydroascorbic acid and further breakdown, is removed from the cells. In nervous tissue, a progressive decrease in vitamin C level or its prolonged deficiency have been associated with an increased risk of disturbances in neurotransmission, leading to dysregulation in brain function. Therefore, understanding the regulatory function of vitamin C in antioxidant defence and identification of its molecular targets deserves more attention. One of the key signalling ions is calcium and a transient rise in its concentration is crucial for all neuronal processes. Extracellular Ca²⁺ influx (through specific ion channels) or Ca²⁺ release from intracellular stores (endoplasmic reticulum, mitochondria) are precisely controlled. Ca²⁺ regulates the functioning of the CNS, including growth, development, myelin formation, synthesis of catecholamines, modulation of neurotransmission and antioxidant protection. A growing body of evidence indicates a unique role for vitamin C in these processes. In this short review, we focus on vitamin C in the regulation of calcium-involved pathways under physiological and stress conditions in the brain.

A novel defined risk signature of endoplasmic reticulum stress-related genes for predicting the prognosis and immune infiltration status of ovarian cancer

Endoplasmic reticulum (ER) stress, as an emerging hallmark feature of cancer, has a considerable impact on cell proliferation, metastasis, invasion, and chemotherapy resistance. Ovarian cancer (OvCa) is one of the leading causes of cancer-related mortality across the world due to the late stage of disease at diagnosis. Studies have explored the influence of ER stress on OvCa in recent years, while the predictive role of ER stress-related genes in OvCa prognosis remains unexplored. Here, we enrolled 552 cases of ER stress-related genes involved in OvCa from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) cohorts for the screening of prognosis-related genes. The least absolute shrinkage and selection operator (LASSO) regression was applied to establish an ER stress-related risk signature based on the TCGA cohort. A seven-gene signature revealed a favorable predictive efficacy for the TCGA, International Cancer Genome Consortium (ICGC), and another GEO cohort (P<0.001, P<0.001, and P=0.04, respectively). Moreover, functional annotation indicated that this signature was enriched in cellular response and senescence, cytokines interaction, as well as multiple immune-associated terms. The immune infiltration profiles further delineated an immunologic unresponsive status in the high-risk group. In conclusion, ER stress-related genes are vital factors predicting the prognosis of OvCa, and possess great application potential in the clinic.

PKM2 deficiency exacerbates gram-negative sepsis-induced cardiomyopathy via disrupting cardiac calcium homeostasis

Sepsis is a life-threatening syndrome with multi-organ dysfunction in critical care medicine. With the occurrence of sepsis-induced cardiomyopathy (SIC), characterized by reduced ventricular contractility, the mortality of sepsis is boosted to 70-90%. Pyruvate kinase M2 (PKM2) functions in a variety of biological processes and diseases other than glycolysis, and has been documented as a cardioprotective factor in several heart diseases. It is currently unknown whether PKM2 influences the development of SIC. Here, we found that PKM2 was upregulated in cardiomyocytes treated with LPS both in vitro and in vivo. Pkm2 inhibition exacerbated the LPS-induced cardiac damage to neonatal rat cardiomyocytes (NRCMs). Furthermore, cardiomyocytes lacking PKM2 aggravated LPS-induced cardiomyopathy, including myocardial damage and impaired contractility, whereas PKM2 overexpression and activation mitigated SIC. Mechanism investigation revealed that PKM2 interacted with sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), a key regulator of the excitation-contraction coupling, to maintain calcium homeostasis, and PKM2 deficiency exacerbated LPS-induced cardiac systolic dysfunction by impairing SERCA2a expression. In conclusion, these findings highlight that PKM2 plays an essential role in gram-negative sepsis-induced cardiomyopathy, which provides an attractive target for the prevention and treatment of septic cardiomyopathy.

Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA)-mediated ER stress crosstalk with autophagy is involved in tris(2-chloroethyl) phosphate stress-induced cardiac fibrosis

Excessive organophosphate flame retardant (OPFR) use in consumer products has been reported to increase human disease susceptibility. However, the adverse effects of tris(2-chloroethyl) phosphate (TCEP) (a chlorinated alkyl OPFR) on the heart remain unknown. In this study, we tested whether cardiac fibrosis occurred in animal models of TCEP (10 mg/kg b.w./day) administered continuously by gavage for 30 days and evaluated the specific role of sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA). First, we confirmed that TCEP could trigger cardiac fibrosis by histopathological observation and cardiac fibrosis markers. We further verified that cardiac fibrosis occurred in animal models of TCEP exposure accompanied by SERCA2a, SERCA2b and SERCA2c downregulation. Notably, inductively coupled plasma-mass spectrometry (ICP-MS) analysis revealed that the cardiac concentrations of Ca²⁺ increased by 45.3% after TCEP exposure. Using 4-Isopropoxy-N-(2-methylquinolin-8-yl)benzamide (CDN1163, a small molecule SERCA activator), we observed that Ca²⁺ overload and subsequent cardiac fibrosis caused by TCEP were both alleviated. Simultaneously, the protein levels of endoplasmic reticulum (ER) markers (protein kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring protein 1α (IRE1α), eukaryotic initiation factor 2 α (eIF2α)) were upregulated by TCEP, which could be abrogated by CDN1163 pretreatment. Furthermore, we observed that CDN1163 supplementation prevented overactive autophagy induced by TCEP in the heart. Mechanistically, TCEP could lead to Ca²⁺ overload by inhibiting the expression of SERCA, thereby triggering ER stress and overactive autophagy, eventually resulting in cardiac fibrosis. Together, our results suggest that the Ca²⁺ overload/ER stress/autophagy axis can act as a driver of cardiotoxicity induced by TCEP.

Protective Role of Hepassocin against Hepatic Endoplasmic Reticulum Stress in Mice

Hepassocin (HPS) is a hepatokine that has multiple proposed physiological functions. Some of the biological processes in which it is involved are closely related to endoplasmic reticulum (ER) stress, but the role of HPS in the regulation of ER stress remains unclear. Here, we demonstrated that HPS transcription is induced by the protein kinase RNA-like ER kinase (PERK)/activating transcription factor 4 (ATF4) cascade upon ER stress in hepatocytes. Additionally, fasting/refeeding also induced HPS expression in mice liver. The loss of HPS sensitizes hepatocytes to ER stress-related cytotoxicity in vitro, whereas HPS treatment altered these phenotypes. HPS deficiency exacerbates fasting/refeeding-induced ER stress in vivo. The preliminary administration of HPS ameliorates liver steatosis, cell death, and inflammation in mice injected with tunicamycin (TM). The improvement of HPS can be observed even if HPS protein is injected after TM treatment. Furthermore, the administration of an ER stress inhibitor alleviated steatohepatitis in methionine- and choline-deficient (MCD) diet-fed HPS-deficient mice. These results suggest that HPS protects hepatocytes from physiological and pathological ER stress, and that the inactivation of HPS signaling aggravating ER stress may be a novel mechanism that drives the development of steatohepatitis. The protective mechanism of HPS against ER stress in hepatocytes was associated with the regulation of ER calcium handling, and the suppression of calcium influx release from ER upon stressor treatment. Collectively, our findings indicate that HPS may act in a negative feedback fashion to regulate hepatic ER stress and protect hepatocytes from ER stress-related injury. HPS has the potential to be a candidate drug for the treatment of ER stress-related liver injury.