Neuronal differentiation is associated with a redox-regulated increase of copper flow to the secretory pathway

A primer on copper biology in the brain

This primer aims to expose scientists who study the brain to the field of copper biology. We briefly discuss key copper homeostasis mechanisms and proteins and place these functions in the context of the brain and neurodevelopment. A small number of key copper genes are explored as representative examples of the importance of this metal to the brain. We show that these genes are expressed throughout the brain and their defects are linked to a diverse array of neurological phenotypes, which we discuss further in the context of several neurological and neurodegenerative diseases associated with dysregulation of copper. This review aims to expose interested scientists to the fundamental roles for copper in the brain, the primary proteins responsible for maintaining copper homeostasis in the brain, and the classic neurological diseases associated with this metal.

Copper in cancer: friend or foe? Metabolism, dysregulation, and therapeutic opportunities

Copper, one of the essential nutrients for the human body, acts as an electron relay in multiple pathways due to its redox properties. Both deficiencies and excesses of copper lead to cellular fragility. Therefore, it can manifest pro- and anti-cancer properties in tumors. Therefore, it is crucial to clarify the copper activity within the cell. We have thoughtfully summarized the metabolic activities of copper from a macro and micro perspective. Cuproptosis, as well as other forms of cell death, is directly or indirectly interfered with by Cu2+, causing cancer cell death. Meanwhile, we did pan-cancer analysis of cuproptosis-related genes to further clarify the roles of these genes. In addition, copper has been found to be involved in multiple pathways within the metastasis of cancer cells. Given the complexity of copper's role, we are compelled to ask: is copper a friend or a foe? Up to now, copper has been used in various clinical applications, including protocols for measurement of copper concentration and bioimaging of radioactive 64Cu. But therapeutically it is still a continuation of the old medicine, and new possibilities need to be explored, such as the use of nanomaterials. Some studies have also shown that copper has considerable interventional power in metabolic cancers, which provides the great applications potential of copper therapy in specific cancer types. This paper reviews the dual roles played by cuproptosis in cancer from the new perspectives of oxidative stress, cell death, and tumor metastasis, and points out the value of its application in specific cancer types, summarizes the value of its testing and imaging from the perspective of clinical application as well as the current feasible options for the new use of the old drugs, and emphasizes the prospects for the application of nano-copper.

Induction of Cuproptosis by Dichloromethane Extract From Patrinia scabiosaefolia Fisch on K562 Cells

Cuproptosis is a newly identified form of cell death that relies on copper (Cu) ionophores to transport Cu into cancer cells. As a perennial herb, Patrinia scabiosaefolia Fisch (PS) has garnered significant attention owing to its analgesic, anti-inflammatory, antibacterial, and antitumor properties. Previous research has shown that the extract from PS (DEPS) can inhibit the growth of leukemia cell lines. However, the specific mechanism of its anti-leukemic effect has not been fully clarified. Therefore, this study was conducted to investigate the molecular mechanism of cuproptosis in the treatment of leukemia with DEPS. Our results demonstrated that DEPS up-regulated SLC31A1 and down-regulated ATP7B expression, which increased intracellular copper concentration, down-regulated FDX1, influenced the lipoylation of DLAT and DLD, and subsequently increased the expression of the stress protein HSP70 and the expression of PDHA1, inducing copper death in K562 cells. In addition, we investigated the toxicity of DEPS in vivo and demonstrated its low in vivo toxicity and adequate in vivo safety. In conclusion, our results suggest that DEPS may induce cuproptosis in cells, offering valuable insights for the future application of PS in leukemia treatment.

Adaptive protein synthesis in genetic models of copper deficiency and childhood neurodegeneration

Rare inherited diseases caused by mutations in the copper transporters SLC31A1 (CTR1) or ATP7A induce copper deficiency in the brain, causing seizures and neurodegeneration in infancy through poorly understood mechanisms. Here, we used multiple model systems to characterize the molecular mechanisms by which neuronal cells respond to copper deficiency. Targeted deletion of CTR1 in neuroblastoma cells produced copper deficiency that produced a metabolic shift favoring glycolysis over oxidative phosphorylation. Proteomic and transcriptomic analysis of CTR1 knockout (KO) cells revealed simultaneous up-regulation of mTORC1 and S6K signaling and reduced PERK signaling. Patterns of gene and protein expression and pharmacogenomics show increased activation of the mTORC1-S6K pathway as a prosurvival mechanism, ultimately resulting in increased protein synthesis. Spatial transcriptomic profiling of Atp7aflx/Y :: Vil1Cre/+ mice identified up-regulated protein synthesis machinery and mTORC1-S6K pathway genes in copper-deficient Purkinje neurons in the cerebellum. Genetic epistasis experiments in Drosophila demonstrated that copper deficiency dendritic phenotypes in class IV neurons are improved or rescued by increased S6k expression or 4E-BP1 (Thor) RNAi, while epidermis phenotypes are exacerbated by Akt, S6k, or raptor RNAi. Overall, we demonstrate that increased mTORC1-S6K pathway activation and protein synthesis is an adaptive mechanism by which neuronal cells respond to copper deficiency.

Mammalian copper homeostasis: physiological roles and molecular mechanisms

In the past decade, evidence for the numerous roles of copper (Cu) in mammalian physiology has grown exponentially. The discoveries of Cu involvement in cell signaling, autophagy, cell motility, differentiation, and regulated cell death (cuproptosis) have markedly extended the list of already known functions of Cu, such as a cofactor of essential metabolic enzymes, a protein structural component, and a regulator of protein trafficking. Novel and unexpected functions of Cu transporting proteins and enzymes have been identified, and new disorders of Cu homeostasis have been described. Significant progress has been made in the mechanistic studies of two classic disorders of Cu metabolism, Menkes disease and Wilson's disease, which paved the way for novel approaches to their treatment. The discovery of cuproptosis and the role of Cu in cell metastatic growth have markedly increased interest in targeting Cu homeostatic pathways to treat cancer. In this review, we summarize the established concepts in the field of mammalian Cu physiology and discuss how new discoveries of the past decade expand and modify these concepts. The roles of Cu in brain metabolism and in cell functional speciation and a recently discovered regulated cell death have attracted significant attention and are highlighted in this review.

Metal Ruthenium Complexes Treat Spinal Cord Injury By Alleviating Oxidative Stress Through Interaction With Antioxidant 1 Copper Chaperone Protein

Oxidative stress is a major factor affecting spinal cord injury (SCI) prognosis. A ruthenium metal complex can aid in treating SCI by scavenging reactive oxygen species via a protein-regulated mechanism to alleviate oxidative stress. This study aimed to introduce a pioneering strategy for SCI treatment by designing two novel half-sandwich ruthenium (II) complexes containing diverse N^N-chelating ligands. The general formula is [(η6-Arene)Ru(N^N)Cl]PF6, where arene is either 2-phenylethanol-1-ol (bz-EA) or 3-phenylpropanol-1-ol (bz-PA), and the N^N-chelating ligands are fluorine-based imino-pyridyl ligands. This study shows that these ruthenium metal complexes protect neurons by scavenging reactive oxygen species. Notably, η6-Arene substitution from bz-PA to bz-EA significantly enhances reactive oxygen species scavenging ability and neuroprotective effect. Additionally, molecular dynamics simulations indicate that the ruthenium metal complex increases Antioxidant 1 Copper Chaperone protein expression, reduces oxidative stress, and protects neurons during SCI treatment. Furthermore, ruthenium metal complex protected spinal cord neurons and stimulated their regeneration, which improves electrical signals and motor functions in mice with SCI. Thus, this treatment strategy using ruthenium metal complexes can be a new therapeutic approach for the efficient treatment of SCI.

Cysteine Rich Intestinal Protein 2 is a copper-responsive regulator of skeletal muscle differentiation and metal homeostasis

Copper (Cu) is essential for respiration, neurotransmitter synthesis, oxidative stress response, and transcription regulation, with imbalances leading to neurological, cognitive, and muscular disorders. Here we show the role of a novel Cu-binding protein (Cu-BP) in mammalian transcriptional regulation, specifically on skeletal muscle differentiation using murine primary myoblasts. Utilizing synchrotron X-ray fluorescence-mass spectrometry, we identified murine cysteine-rich intestinal protein 2 (mCrip2) as a key Cu-BP abundant in both nuclear and cytosolic fractions. mCrip2 binds two to four Cu+ ions with high affinity and presents limited redox potential. CRISPR/Cas9-mediated deletion of mCrip2 impaired myogenesis, likely due to Cu accumulation in cells. CUT&RUN and transcriptome analyses revealed its association with gene promoters, including MyoD1 and metallothioneins, suggesting a novel Cu-responsive regulatory role for mCrip2. Our work describes the significance of mCrip2 in skeletal muscle differentiation and metal homeostasis, expanding understanding of the Cu-network in myoblasts. Copper (Cu) is essential for various cellular processes, including respiration and stress response, but imbalances can cause serious health issues. This study reveals a new Cu-binding protein (Cu-BP) involved in muscle development in primary myoblasts. Using unbiased metalloproteomic techniques and high throughput sequencing, we identified mCrip2 as a key Cu-BP found in cell nuclei and cytoplasm. mCrip2 binds up to four Cu+ ions and has a limited redox potential. Deleting mCrip2 using CRISPR/Cas9 disrupted muscle formation due to Cu accumulation. Further analyses showed that mCrip2 regulates the expression of genes like MyoD1, essential for muscle differentiation, and metallothioneins in response to copper supplementation. This research highlights the importance of mCrip2 in muscle development and metal homeostasis, providing new insights into the Cu-network in cells.

Mechanism of Cu entry into the brain: many unanswered questions

Brain tissue requires high amounts of copper (Cu) for its key physiological processes, such as energy production, neurotransmitter synthesis, maturation of neuropeptides, myelination, synaptic plasticity, and radical scavenging. The requirements for Cu in the brain vary depending on specific brain regions, cell types, organism age, and nutritional status. Cu imbalances cause or contribute to several life-threatening neurologic disorders including Menkes disease, Wilson disease, Alzheimer's disease, Parkinson's disease, and others. Despite the well-established role of Cu homeostasis in brain development and function, the mechanisms that govern Cu delivery to the brain are not well defined. This review summarizes available information on Cu transfer through the brain barriers and discusses issues that require further research.

Emerging perspectives of copper-mediated transcriptional regulation in mammalian cell development

Copper (Cu) is a vital micronutrient necessary for proper development and function of mammalian cells and tissues. Cu mediates the function of redox active enzymes that facilitate metabolic processes and signaling pathways. Cu levels are tightly regulated by a network of Cu-binding transporters, chaperones, and small molecule ligands. Extensive research has focused on the mammalian Cu homeostasis (cuprostasis) network and pathologies, which result from mutations and perturbations. There are roles for Cu-binding proteins as transcription factors (Cu-TFs) and regulators that mediate metal homeostasis through the activation or repression of genes associated with Cu handling. Emerging evidence suggests that Cu and some Cu-TFs may be involved in the regulation of targets related to development-expanding the biological roles of Cu-binding proteins. Cu and Cu-TFs are implicated in embryonic and tissue-specific development alongside the mediation of the cellular response to oxidative stress and hypoxia. Cu-TFs are also involved in the regulation of targets implicated in neurological disorders, providing new biomarkers and therapeutic targets for diseases such as Parkinson's disease, prion disease, and Friedreich's ataxia. This review provides a critical analysis of the current understanding of the role of Cu and cuproproteins in transcriptional regulation.

New BDNF and NT-3 Cyclic Mimetics Concur with Copper to Activate Trophic Signaling Pathways as Potential Molecular Entities to Protect Old Brains from Neurodegeneration

A low level of Neurotrophins (NTs), their Tyrosine Kinase Receptors (Trks), Vascular Endothelial Growth Factors (VEGFs) and their receptors, mainly VEGFR1 and VEGFR2, characterizes AD brains. The use of NTs and VEGFs as drugs presents different issues due to their low permeability of the blood-brain barrier, the poor pharmacokinetic profile, and the relevant side effects. To overcome these issues, different functional and structural NT mimics have been employed. Being aware that the N-terminus domain as the key domain of NTs for the binding selectivity and activation of Trks and the need to avoid or delay proteolysis, we herein report on the mimicking ability of two cyclic peptide encompassing the N-terminus of Brain Derived Growth Factor (BDNF), (c-[HSDPARRGELSV-]), cBDNF(1-12) and of Neurotrophin3 (NT3), (c-[YAEHKSHRGEYSV-]), cNT3(1-13). The two cyclic peptide features were characterized by a combined thermodynamic and spectroscopic approach (potentiometry, NMR, UV-vis and CD) that was extended to their copper(II) ion complexes. SH-SY5Y cell assays show that the Cu2+ present at the sub-micromolar level in the complete culture media affects the treatments with the two peptides. cBDNF(1-12) and cNT3(1-13) act as ionophores, induce neuronal differentiation and promote Trks and CREB phosphorylation in a copper dependent manner. Consistently, both peptide and Cu2+ stimulate BDNF and VEGF expression as well as VEGF release; cBDNF(1-12) and cNT3(1-13) induce the expression of Trks and VEGFRs.

Inorganic ions activate lineage-specific gene regulatory networks

Inorganic biomaterials have been shown to direct cellular responses, including cell-cell and cell-matrix interactions. Notably, ions released from these inorganic biomaterials play a vital role in defining cell identity, and promoting tissue-specific functions. However, the effect of inorganic ions on cellular functions have yet to be investigated at the transcriptomic level, representing a critical knowledge gap in the development of next-generation bioactive materials. To address this gap, we investigated the impact of various inorganic ions including silver, copper, titanium, and platinum on human mesenchymal stem cells (hMSCs). Our finding showed that silver and copper induce osteogenic and chondrogenic differentiation respectively, through enrichment of lineage-specific gene expression program. In particular, silver effectively induced Wingless/Integrated (Wnt) and mitogen-activated protein kinase (MAPK) signaling, which are vital for osteogenesis. On the other hand, copper specifically stimulated Transforming growth factor beta (TGFβ) signaling, while suppressing Janus kinase/signal transducers and activators of transcription (JAK-STAT) signaling, thereby promoting chondrogenesis. In contrast, platinum, and tantalum, ions didn't stimulate regenerative responses. Together, our findings highlight the potential of inorganic biomaterials in tissue regeneration strategies, which currently rely largely on growth factors and small molecule therapeutics. STATEMENT OF SIGNIFICANCE: This research emphasizes the critical role of bioactive inorganic ions in controlling lineage-specific gene expression patterns in mesenchymal stem cells, effectively modulating the transcriptome landscape and directing cell fate. The study lays the foundation for a systematic database of biomaterial candidates and their effects on cellular functions, which will ultimately streamline the translation of new biomaterials into clinical applications.

The physiological and pathophysiological roles of copper in the nervous system

Copper is a critical trace element in biological systems due the vast number of essential enzymes that require the metal as a cofactor, including cytochrome c oxidase, superoxide dismutase and dopamine-β-hydroxylase. Due its key role in oxidative metabolism, antioxidant defence and neurotransmitter synthesis, copper is particularly important for neuronal development and proper neuronal function. Moreover, increasing evidence suggests that copper also serves important functions in synaptic and network activity, the regulation of circadian rhythms, and arousal. However, it is important to note that because of copper's ability to redox cycle and generate reactive species, cellular levels of the metal must be tightly regulated to meet cellular needs while avoiding copper-induced oxidative stress. Therefore, it is essential that the intricate system of copper transporters, exporters, copper chaperones and copper trafficking proteins function properly and in coordinate fashion. Indeed, disorders of copper metabolism such as Menkes disease and Wilson disease, as well as diseases linked to dysfunction of copper-requiring enzymes, such as SOD1-linked amyotrophic lateral sclerosis, demonstrate the dramatic neurological consequences of altered copper homeostasis. In this review, we explore the physiological importance of copper in the nervous system as well as pathologies related to improper copper handling.

Information Transmission through Biotic-Abiotic Interfaces to Restore or Enhance Human Function

Advancements in reliable information transfer across biotic-abiotic interfaces have enabled the restoration of lost human function. For example, communication between neuronal cells and electrical devices restores the ability to walk to a tetraplegic patient and vision to patients blinded by retinal disease. These impactful medical achievements are aided by tailored biotic-abiotic interfaces that maximize information transfer fidelity by considering the physical properties of the underlying biological and synthetic components. This Review develops a modular framework to define and describe the engineering of biotic and abiotic components as well as the design of interfaces to facilitate biotic-abiotic information transfer using light or electricity. Delineating the properties of the biotic, interface, and abiotic components that enable communication can serve as a guide for future research in this highly interdisciplinary field. Application of synthetic biology to engineer light-sensitive proteins has facilitated the control of neural signaling and the restoration of rudimentary vision after retinal blindness. Electrophysiological methodologies that use brain-computer interfaces and stimulating implants to bypass spinal column injuries have led to the rehabilitation of limb movement and walking ability. Cellular interfacing methodologies and on-chip learning capability have been made possible by organic transistors that mimic the information processing capacity of neurons. The collaboration of molecular biologists, material scientists, and electrical engineers in the emerging field of biotic-abiotic interfacing will lead to the development of prosthetics capable of responding to thought and experiencing touch sensation via direct integration into the human nervous system. Further interdisciplinary research will improve electrical and optical interfacing technologies for the restoration of vision, offering greater visual acuity and potentially color vision in the near future.

Cysteine Rich Intestinal Protein 2 is a copper-responsive regulator of skeletal muscle differentiation

Copper (Cu) is an essential trace element required for respiration, neurotransmitter synthesis, oxidative stress response, and transcriptional regulation. Imbalance in Cu homeostasis can lead to several pathological conditions, affecting neuronal, cognitive, and muscular development. Mechanistically, Cu and Cu-binding proteins (Cu-BPs) have an important but underappreciated role in transcription regulation in mammalian cells. In this context, our lab investigates the contributions of novel Cu-BPs in skeletal muscle differentiation using murine primary myoblasts. Through an unbiased synchrotron X-ray fluorescence-mass spectrometry (XRF/MS) metalloproteomic approach, we identified the murine cysteine rich intestinal protein 2 (mCrip2) in a sample that showed enriched Cu signal, which was isolated from differentiating primary myoblasts derived from mouse satellite cells. Immunolocalization analyses showed that mCrip2 is abundant in both nuclear and cytosolic fractions. Thus, we hypothesized that mCrip2 might have differential roles depending on its cellular localization in the skeletal muscle lineage. mCrip2 is a LIM-family protein with 4 conserved Zn2+-binding sites. Homology and phylogenetic analyses showed that mammalian Crip2 possesses histidine residues near two of the Zn2+-binding sites (CX2C-HX2C) which are potentially implicated in Cu+-binding and competition with Zn2+. Biochemical characterization of recombinant human hsCRIP2 revealed a high Cu+-binding affinity for two and four Cu+ ions and limited redox potential. Functional characterization using CRISPR/Cas9-mediated deletion of mCrip2 in primary myoblasts did not impact proliferation, but impaired myogenesis by decreasing the expression of differentiation markers, possibly attributed to Cu accumulation. Transcriptome analyses of proliferating and differentiating mCrip2 KO myoblasts showed alterations in mRNA processing, protein translation, ribosome synthesis, and chromatin organization. CUT&RUN analyses showed that mCrip2 associates with a select set of gene promoters, including MyoD1 and metallothioneins, acting as a novel Cu-responsive or Cu-regulating protein. Our work demonstrates novel regulatory functions of mCrip2 that mediate skeletal muscle differentiation, presenting new features of the Cu-network in myoblasts.

ATP7A-dependent copper sequestration contributes to termination of β-CATENIN signaling during early adipogenesis

OBJECTIVES

Adipocyte fate determination is tightly regulated by extrinsic signaling pathways and intrinsic metabolic and morphologic changes that maintain adipose tissue function. Copper (Cu) homeostasis is required for the normal metabolism of mature adipocytes, whereas the role of Cu in adipogenesis is unclear.

METHODS

To determine the role of Cu is adipocytes differentiation, we used 3T3-L1 adipocytes, immunocytochemistry, X-ray fluorescence, mass-spectrometry, pharmacological treatments, and manipulations of copper levels.

RESULTS

In differentiating 3T3-L1 cells, adipogenic stimuli trigger the upregulation and trafficking of the Cu transporter Atp7a, thus causing Cu redistribution from the cytosol to vesicles. Disrupting Cu homeostasis by the deletion of Atp7a results in Cu elevation and inhibition of adipogenesis. The upregulation of C/EBPβ, an initial step of adipogenesis, is not affected in Atp7a-/- cells, whereas the subsequent upregulation of PPARγ is inhibited. Comparison of changes in the Atp7a-/- and wild type cells proteomes during early adipogenesis revealed stabilization of β-catenin, a negative regulator of adipogenesis. Cu chelation, or overexpression of the Cu transporter ATP7B in Atp7a-/- cells, restored β-catenin down-regulation and intracellular targeting.

CONCLUSIONS

Cu buffering during early adipogenesis contributes to termination of β-catenin signaling. Abnormal upregulation of β-catenin was also observed in vivo in the livers of Atp7b-/- mice, which accumulate Cu, suggesting a tissue-independent crosstalk between Cu homeostasis and the Wnt/β-catenin pathway. These results point to a new regulatory role of Cu in adipocytes and contribute to better understanding of human disorders of Cu misbalance.

Identification of a 5-Gene Cuproptosis Signature Predicting the Prognosis for Colon Adenocarcinoma Based on WGCNA

Background: Colorectal cancer is a highly aggressive malignant tumor that primarily affects the digestive system. It is frequently diagnosed at an advanced stage. Cuproptosis is a copper-dependent form cell death mechanism, distinct from all other known pathways underlying cell death, tumor progression, prognosis, and immune response. Although the role of cuproptosis in colorectal cancer has been investigated over time, there is still an urgent need to explore new methods and insights to understand its potential function. Methods: The Gene Expression Omnibus and The Cancer Genome Atlas gene expression data were systematically explored to investigate the role of cuproptosis in colon adenocarcinoma. The weighted gene coexpression network analysis was used to construct a gene coexpression network and identify the critical module and cuproptosis-related genes correlated with colon adenocarcinoma prognosis. A cuproptosis-related genes prognostic signature for colon adenocarcinoma was identified and validated. To validate the identified gene signature, quantitative reverse transcription-polymerase chain reaction was performed. Cell proliferation assays were analyzed by CCK8 and cell cycle detection. In addition, reactive oxygen species assay was also analyzed. Results: Five hub cuproptosis-related genes (Dihydrolipoamide S-acetyltransferase, Cyclin-dependent kinase inhibitor 2A, ATOX1, VEGFA, and ULK1) were screened and a prognostic risk model for predicting overall survival was established based on these genes. The model was successfully tested in the validation cohort and the GEPIA database. Colon adenocarcinoma patients were categorized into high-risk and low-risk groups based on risk scores. The study revealed that patients with higher risk scores were more likely to have a poor prognosis. Moreover, Dihydrolipoamide S-acetyltransferase was a tumor suppressor gene that can induce cell death and affected the redox reactions in the colon cancer cell line. Conclusions: These findings suggest that the newly identified 5-gene signature may serve as a more reliable prognostic factor than clinical factors such as age and stage of disease. These findings offer a theoretical foundation for further investigation into potential cuproptosis-related biomarkers for predicting colon adenocarcinoma prognosis in the future.

P-type ATPases: Many more enigmas left to solve

P-type ATPases constitute a large ancient super-family of primary active pumps that have diverse substrate specificities ranging from H+ to phospholipids. The significance of these enzymes in biology cannot be overstated. They are structurally related, and their catalytic cycles alternate between high- and low-affinity conformations that are induced by phosphorylation and dephosphorylation of a conserved aspartate residue. In the year 1988, all P-type sequences available by then were analyzed and five major families, P1 to P5, were identified. Since then, a large body of knowledge has accumulated concerning the structure, function, and physiological roles of members of these families, but only one additional family, P6 ATPases, has been identified. However, much is still left to be learned. For each family a few remaining enigmas are presented, with the intention that they will stimulate interest in continued research in the field. The review is by no way comprehensive and merely presents personal views with a focus on evolution.

α-lipoic acid ameliorates consequences of copper overload by up-regulating selenoproteins and decreasing redox misbalance

α-lipoic acid (LA) is an essential cofactor for mitochondrial dehydrogenases and is required for cell growth, metabolic fuel production, and antioxidant defense. In vitro, LA binds copper (Cu) with high affinity and as an endogenous membrane permeable metabolite could be advantageous in mitigating the consequences of Cu overload in human diseases. We tested this hypothesis in 3T3-L1 preadipocytes with inactivated Cu transporter Atp7a; these cells accumulate Cu and show morphologic changes and mitochondria impairment. Treatment with LA corrected the morphology of Atp7a-/- cells similar to the Cu chelator bathocuproinedisulfonate (BCS) and improved mitochondria function; however, the mechanisms of LA and BCS action were different. Unlike BCS, LA did not decrease intracellular Cu but instead increased selenium levels that were low in Atp7a-/- cells. Proteome analysis confirmed distinct cell responses to these compounds and identified upregulation of selenoproteins as the major effect of LA on preadipocytes. Upregulation of selenoproteins was associated with an improved GSH:GSSG ratio in cellular compartments, which was lowered by elevated Cu, and reversal of protein oxidation. Thus, LA diminishes toxic effects of elevated Cu by improving cellular redox environment. We also show that selenium levels are decreased in tissues of a Wilson disease animal model, especially in the liver, making LA an attractive candidate for supplemental treatment of this disease.

Abnormalities in Copper Status Associated with an Elevated Risk of Parkinson's Phenotype Development

In the last 15 years, among the many reasons given for the development of idiopathic forms of Parkinson's disease (PD), copper imbalance has been identified as a factor, and PD is often referred to as a copper-mediated disorder. More than 640 papers have been devoted to the relationship between PD and copper status in the blood, which include the following markers: total copper concentration, enzymatic ceruloplasmin (Cp) concentration, Cp protein level, and non-ceruloplasmin copper level. Most studies measure only one of these markers. Therefore, the existence of a correlation between copper status and the development of PD is still debated. Based on data from the published literature, meta-analysis, and our own research, it is clear that there is a connection between the development of PD symptoms and the number of copper atoms, which are weakly associated with the ceruloplasmin molecule. In this work, the link between the risk of developing PD and various inborn errors related to copper metabolism, leading to decreased levels of oxidase ceruloplasmin in the circulation and cerebrospinal fluid, is discussed.

Identification and validation of a novel cuproptosis-related genes signature associated with prognosis, clinical implications and immunotherapy of hepatocellular carcinoma

Background: Cuproptosis is a novel type of regulated cell death and is reported to promote tumor occurrence and progression. However, whether a cuproptosis-related signature has an impact on hepatocellular carcinoma (HCC) is still unclear. Materials and methods: We analyzed the transcriptome data of HCC from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) database, and searched for tumor types with different cuproptosis patterns through consistent clustering of cuproptosis genes. We then constructed a Cuproptosis-Related Genes (CRGs)-based risk signature through LASSO COX regression, and further analyzed its impact on the prognosis, clinical characteristics, immune cell infiltration, and drug sensitivity of HCC. Results: We identified the expression changes of 10 cuproptosis-related genes in HCC, and all the patients can be divided into two subtypes with different prognosis by applying the consensus clustering algorithm. We then constructed a cuproptosis-related risk signature and identified five CRGs, which were highly correlated with prognosis and representative of this gene set, namely G6PD, PRR11, KIF20A, EZH2, and CDCA8. Patients in the low CRGs signature group had a favorable prognosis. We further validated the CRGs signature in ICGC cohorts and got consistent results. Besides, we also discovered that the CRGs signature was significantly associated with a variety of clinical characteristics, different immune landscapes and drug sensitivity. Moreover, we explored that the high CRGs signature group was more sensitive to immunotherapy. Conclusion: Our integrative analysis demonstrated the potential molecular signature and clinical applications of CRGs in HCC. The model based on CRGs can precisely predict the survival outcomes of HCC, and help better guide risk stratification and treatment strategy for HCC patients.

A novel prognostic signature of cuproptosis-related genes and the prognostic value of FDX1 in gliomas

Background: Gliomas are the most common malignant tumors of the central nervous system, with extremely bad prognoses. Cuproptosis is a novel form of regulated cell death. The impact of cuproptosis-related genes on glioma development has not been reported. Methods: The TCGA, GTEx, and CGGA databases were used to retrieve transcriptomic expression data. We employed Cox's regressions to determine the associations between clinical factors and cuproptosis-related gene expression. Overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) were evaluated using the Kaplan-Meier method. We also used the least absolute shrinkage and selection operator (LASSO) regression technique. Results: The expression levels of all 10 CRGs varied considerably between glioma tumors and healthy tissues. In glioma patients, the levels of CDKN2A, FDX1, DLD, DLAT, LIAS, LIPT1, and PDHA1 were significantly associated with the OS, disease-specific survival, and progression-free interval. We used LASSO Cox's regression to create a prognostic model; the risk score was (0.882340) *FDX1 expression + (0.141089) *DLD expression + (-0.333875) *LIAS expression + (0.356469) *LIPT1 expression + (-0.123851) *PDHA1 expression. A high-risk score/signature was associated with poor OS (hazard ratio = 3.50, 95% confidence interval 2, -4.55, log-rank p < 0.001). Cox's regression revealed that the FDX1 level independently predicted prognosis; FDX1 may control immune cell infiltration of the tumor microenvironment. Conclusion: The CRG signature may be prognostic in glioma patients, and the FDX1 level may independently predict glioma prognosis. These data may afford new insights into treatment.

Subcellular redox responses reveal different Cu-dependent antioxidant defenses between mitochondria and cytosol

Excess intracellular Cu perturbs cellular redox balance and thus causes diseases. However, the relationship between cellular redox status and Cu homeostasis and how such an interplay is coordinated within cellular compartments has not yet been well established. Using combined approaches of organelle-specific redox sensor Grx1-roGFP2 and non-targeted proteomics, we investigate the real-time Cu-dependent antioxidant defenses of mitochondria and cytosol in live HEK293 cells. The Cu-dependent real-time imaging experiments show that CuCl2 treatment results in increased oxidative stress in both cytosol and mitochondria. In contrast, subsequent excess Cu removal by bathocuproine sulfonate, a Cu chelating reagent, lowers oxidative stress in mitochondria but causes even higher oxidative stress in the cytosol. The proteomic data reveal that several mitochondrial proteins, but not cytosolic ones, undergo significant abundance change under Cu treatments. The proteomic analysis also shows that proteins with significant changes are related to mitochondrial oxidative phosphorylation and glutathione synthesis. The differences in redox behaviors and protein profiles in different cellular compartments reveal distinct mitochondrial and cytosolic response mechanisms upon Cu-induced oxidative stress. These findings provide insights into how redox and Cu homeostasis interplay by modulating specific protein expressions at the subcellular levels, shedding light on understanding the effects of Cu-induced redox misregulation on the diseases.

SOX4 Mediates ATRA-Induced Differentiation in Neuroblastoma Cells

Neuroblastoma (NB), which is considered to be caused by the differentiation failure of neural crest cells, is the most common extracranial malignant solid tumor in children. The degree of tumor differentiation in patients with NB is closely correlated with the survival rate. To explore the potential targets that mediate NB cell differentiation, we analyzed four microarray datasets from GEO, and the overlapping down- or upregulated DEGs were displayed using Venn diagrams. SOX4 was one of the overlapping upregulated DEGs and was confirmed by RT-qPCR and Western blot in ATRA-treated NGP, SY5Y, and BE2 cells. To clarify whether SOX4 was the target gene regulating NB cell differentiation, the correlation between the expression of SOX4 and the survival of clinical patients was analyzed via the R2 database, SOX4 overexpression plasmids and siRNAs were generated to change the expression of SOX4, RT-qPCR and Western blot were performed to detect SOX4 expression, cell confluence or cell survival was detected by IncuCyte Zoom or CCK8 assay, immunocytochemistry staining was performed to detect cells' neurites, and a cell cycle analysis was implemented using Flow cytometry after PI staining. The results showed that the survival probabilities were positively correlated with SOX4 expression, in which overexpressing SOX4 inhibited NB cell proliferation, elongated the cells' neurite, and blocked the cell cycle in G1 phase, and that knockdown of the expression of SOX4 partially reversed the ATRA-induced inhibition of NB cell proliferation, the elongation of the cells' neurites, and the blocking of the cell cycle in the G1 phase. These indicate that SOX4 may be a target to induce NB cell differentiation.

Correlative nano-imaging of metals and proteins in primary neurons by synchrotron X-ray fluorescence and STED super resolution microscopy: Experimental validation

BACKGROUND

It is becoming increasingly clear that biological metals such as iron, copper or zinc are involved in synaptic functions, and in particular in the mechanisms of synaptogenesis and subsequent plasticity. Understanding the role of metals on synaptic functions is a difficult challenge due to the very low concentration of these elements in neurons and to the submicrometer size of synaptic compartments.

NEW METHOD

To address this challenge we have developed a correlative nano-imaging approach combining metal and protein detection. First, stimulated emission depletion (STED) microscopy, a super resolution optical microscopy technique, is applied to locate fluorescently labeled proteins. Then, synchrotron radiation induced X-ray fluorescence (SXRF) is performed on the same regions of interest, e.g. synaptic compartments.

RESULTS

We present here the principle scheme that allows this correlative nano-imaging and its experimental validation. We applied this correlative nano-imaging to the study of the physiological distribution of metals in synaptic compartments of primary rat hippocampal neurons. We thus compared the nanometric distribution of metals with that of synaptic proteins, such as PSD95 or cytoskeleton proteins.

COMPARISON WITH EXISTING METHOD(S)

Compared to correlative imaging approaches currently used to characterize synaptic structures, such as electron microscopy correlated with optical fluorescence, our approach allows for ultra-sensitive detection of trace metals using highly focused synchrotron radiation beams.

CONCLUSION

We provide proof-of-principle for correlative imaging of metals and proteins at the synaptic scale and discuss the present limitations and future developments in this area.

The Molecular Mechanisms of Defective Copper Metabolism in Diabetic Cardiomyopathy

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, connective tissue crosslinking, and antioxidant defense. Copper level has been proved to be closely related to the morbidity and mortality of cardiovascular diseases such as atherosclerosis, heart failure, and diabetic cardiomyopathy (DCM). Copper deficiency can induce cardiac hypertrophy and aggravate cardiomyopathy, while copper excess can mediate various types of cell death, such as autophagy, apoptosis, cuproptosis, pyroptosis, and cardiac hypertrophy and fibrosis. Both copper excess and copper deficiency lead to redox imbalance, activate inflammatory response, and aggravate diabetic cardiomyopathy. This defective copper metabolism suggests a specific metabolic pattern of copper in diabetes and a specific role in the pathogenesis and progression of DCM. This review is aimed at providing a timely summary of the effects of defective copper homeostasis on DCM and discussing potential underlying molecular mechanisms.

Copper Modulates Adult Neurogenesis in Brain Subventricular Zone

The subventricular zone (SVZ) in lateral ventricles is the largest neurogenic region in adult brain containing high amounts of copper (Cu). This study aims to define the role of Cu in adult neurogenesis by chelating labile Cu ions using a well-established Cu chelator D-Penicillamine (D-Pen). A neurosphere model derived from adult mouse SVZ tissues was established and characterized for its functionality with regards to neural stem/progenitor cells (NSPCs). Applying D-Pen in cultured neurospheres significantly reduced intracellular Cu levels and reversed the Cu-induced suppression of NSPC’s differentiation and migration. An in vivo intracerebroventricular (ICV) infusion model was subsequently established to infuse D-Pen directly into the lateral ventricle. Metal analyses revealed a selective reduction of Cu in SVZ by 13.1% (p = 0.19) and 21.4% (p < 0.05) following D-Pen infusions at low (0.075 μg/h) and high (0.75 μg/h) doses for 28 days, respectively, compared to saline-infused controls. Immunohistochemical studies revealed that the 7-day, low-dose D-Pen infusion significantly increased Ki67(+)/Nestin(+) cell counts in SVZ by 28% (p < 0.05). Quantification of BrdU(+)/doublecortin (DCX)(+) newborn neuroblasts in the rostral migration stream (RMS) and olfactory bulb (OB) further revealed that the short-term, low-dose D-Pen infusion, as compared with saline-infused controls, resulted in more newborn neuroblasts in OB, while the high-dose D-Pen infusion showed fewer newborn neuroblasts in OB but with more arrested in the RMS. Long-term (28-day) infusion revealed similar outcomes. The qPCR data from neurosphere experiments revealed altered expressions of mRNAs encoding key proteins known to regulate SVZ adult neurogenesis, including, but not limited to, Shh, Dlx2, and Slit1, in response to the changed Cu level in neurospheres. Further immunohistochemical data indicated that Cu chelation also altered the expression of high-affinity copper uptake protein 1 (CTR1) and metallothionein-3 (MT3) in the SVZ as well as CTR1 in the choroid plexus, a tissue regulating brain Cu homeostasis. Taken together, this study provides first-hand evidence that a high Cu level in SVZ appears likely to maintain the stability of adult neurogenesis in this neurogenic zone.

Copper dependent ERK1/2 phosphorylation is essential for the viability of neurons and not glia

Intracellular copper [Cu(I)] has been hypothesized to play role in the differentiation of the neurons. This necessitates understanding the role of Cu(I) not only in the neurons but also in the glia considering their anatomical proximity, contribution towards ion homeostasis, and neurodegeneration. In this study, we did a systematic investigation of the changes in the cellular copper homeostasis during neuronal and glial differentiation and the pathways triggered by them. Our study demonstrates increased mRNA for the plasma membrane copper transporter CTR1 leading to increased Cu(I) during the neuronal (PC-12) differentiation. ATP7A is retained in the trans-Golgi network (TGN) despite high Cu(I) demonstrating its utilization towards the neuronal differentiation. Intracellular copper triggers pathways essential for neurite generation and ERK1/2 activation during the neuronal differentiation. ERK1/2 activation also accompanies the differentiation of the foetal brain derived neuronal progenitor cells. The study demonstrates that ERK1/2 phosphorylation is essential for the viability of the neurons. In contrast, differentiated C-6 (glia) cells contain low intracellular copper and significant downregulation of the ERK1/2 phosphorylation demonstrating that ERK1/2 activation does not regulate the viability of the glia. But ATP7A shows vesicular localization despite low copper in the glia. In addition to the TGN, ATP7A localizes into RAB11 positive recycling endosomes in the glial neurites. Our study demonstrates the role of copper dependent ERK1/2 phosphorylation in the neuronal viability. Whereas glial differentiation largely involves sequestration of Cu(I) into the endosomes potentially (i) for ready release and (ii) rendering cytosolic copper unavailable for pathways like the ERK1/2 activation.

Heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates the abundance of the copper-transporter ATP7A in an isoform-dependent manner

Copper (Cu) is an essential micronutrient with a critical role in mammalian growth and development. Imbalance of Cu causes severe diseases in humans; therefore, cellular Cu levels are tightly regulated. Major Cu-transport proteins and their cellular behavior have been characterized in detail, whereas their regulation at the mRNA level and associated factors are not well-understood. We show that the heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates Cu homeostasis by modulating the abundance of Cu(I)-transporter ATP7A. Downregulation of hnRNPA2/B1 in HeLa cells increases the ATP7A mRNA and protein levels and significantly decreases cellular Cu; this regulation involves the 3' UTR of ATP7A transcript. Downregulation of B1 and B1b isoforms of hnRNPA2/B1 is sufficient to elevate ATP7A, whereas overexpression of either hnRNPA2 or hnRNPB1 isoforms decreases the ATP7A mRNA levels. Concurrent decrease in hnRNPA2/B1, increase in ATP7A, and a decrease in Cu levels was observed in neuroblastoma SH-SY5Y cells during retinoic acid-induced differentiation; this effect was reversed by overexpression of B1/B1b isoforms. We conclude that hnRNPA2/B1 is a new isoform-specific negative regulator of ATP7A abundance.

Crossroads between membrane trafficking machinery and copper homeostasis in the nerve system

Imbalanced copper homeostasis and perturbation of membrane trafficking are two common symptoms that have been associated with the pathogenesis of neurodegenerative and neurodevelopmental diseases. Accumulating evidence from biophysical, cellular and in vivo studies suggest that membrane trafficking orchestrates both copper homeostasis and neural functions-however, a systematic review of how copper homeostasis and membrane trafficking interplays in neurons remains lacking. Here, we summarize current knowledge of the general trafficking itineraries for copper transporters and highlight several critical membrane trafficking regulators in maintaining copper homeostasis. We discuss how membrane trafficking regulators may alter copper transporter distribution in different membrane compartments to regulate intracellular copper homeostasis. Using Parkinson's disease and MEDNIK as examples, we further elaborate how misregulated trafficking regulators may interplay parallelly or synergistically with copper dyshomeostasis in devastating pathogenesis in neurodegenerative diseases. Finally, we explore multiple unsolved questions and highlight the existing challenges to understand how copper homeostasis is modulated through membrane trafficking.

Dissecting the copper bioinorganic chemistry of the functional and pathological roles of the prion protein: Relevance in Alzheimer's disease and cancer

The cellular prion protein (PrP^C) is a metal-binding biomolecule that can interact with different protein partners involved in pivotal physiological processes, such as neurogenesis and neuronal plasticity. Recent studies profile copper and PrP^C as important players in the pathological mechanisms of Alzheimer's disease and cancer. Although the copper-PrP^C interaction has been characterized extensively, the role of the metal ion in the physiological and pathological roles of PrP^C has been barely explored. In this article, we discuss how copper binding and proteolytic processing may impact the ability of PrP^C to recruit protein partners for its functional roles. The importance to dissect the role of copper-PrP^C interactions in health and disease is also underscored.

Dynamic and cell-specific transport networks for intracellular copper ions

Copper (Cu) homeostasis is essential for the development and function of many organisms. In humans, Cu misbalance causes serious pathologies and has been observed in a growing number of diseases. This Review focuses on mammalian Cu(I) transporters and highlights recent studies on regulation of intracellular Cu fluxes. Cu is used by essential metabolic enzymes for their activity. These enzymes are located in various intracellular compartments and outside cells. When cells differentiate, or their metabolic state is otherwise altered, the need for Cu in different cell compartments change, and Cu has to be redistributed to accommodate these changes. The Cu transporters SLC31A1 (CTR1), SLC31A2 (CTR2), ATP7A and ATP7B regulate Cu content in cellular compartments and maintain Cu homeostasis. Increasing numbers of regulatory proteins have been shown to contribute to multifaceted regulation of these Cu transporters. It is becoming abundantly clear that the Cu transport networks are dynamic and cell specific. The comparison of the Cu transport machinery in the liver and intestine illustrates the distinct composition and dissimilar regulatory response of their Cu transporters to changing Cu levels.

The molecular and cellular basis of copper dysregulation and its relationship with human pathologies

Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu⁺ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.

ATP7A-Regulated Enzyme Metalation and Trafficking in the Menkes Disease Puzzle

Copper is vital for numerous cellular functions affecting all tissues and organ systems in the body. The copper pump, ATP7A is critical for whole-body, cellular, and subcellular copper homeostasis, and dysfunction due to genetic defects results in Menkes disease. ATP7A dysfunction leads to copper deficiency in nervous tissue, liver, and blood but accumulation in other tissues. Site-specific cellular deficiencies of copper lead to loss of function of copper-dependent enzymes in all tissues, and the range of Menkes disease pathologies observed can now be explained in full by lack of specific copper enzymes. New pathways involving copper activated lysosomal and steroid sulfatases link patient symptoms usually related to other inborn errors of metabolism to Menkes disease. Additionally, new roles for lysyl oxidase in activation of molecules necessary for the innate immune system, and novel adapter molecules that play roles in ERGIC trafficking of brain receptors and other proteins, are emerging. We here summarize the current knowledge of the roles of copper enzyme function in Menkes disease, with a focus on ATP7A-mediated enzyme metalation in the secretory pathway. By establishing mechanistic relationships between copper-dependent cellular processes and Menkes disease symptoms in patients will not only increase understanding of copper biology but will also allow for the identification of an expanding range of copper-dependent enzymes and pathways. This will raise awareness of rare patient symptoms, and thus aid in early diagnosis of Menkes disease patients.

Copper Dependent Modulation of α-Synuclein Phosphorylation in Differentiated SHSY5Y Neuroblastoma Cells

Copper (Cu) dyshomeostasis plays a pivotal role in several neuropathologies, such as Parkinson's disease (PD). Metal accumulation in the central nervous system (CNS) could result in loss-of-function of proteins involved in Cu metabolism and redox cycling, generating reactive oxygen species (ROS). Moreover, neurodegenerative disorders imply the presence of an excess of misfolded proteins known to lead to neuronal damage. In PD, Cu accumulates in the brain, binds α-synuclein, and initiates its aggregation. We assessed the correlation between neuronal differentiation, Cu homeostasis regulation, and α-synuclein phosphorylation. At this purpose, we used differentiated SHSY5Y neuroblastoma cells to reproduce some of the characteristics of the dopaminergic neurons. Here, we reported that differentiated cells expressed a significantly higher amount of a copper transporter protein 1 (CTR1), increasing the copper uptake. Cells also showed a significantly more phosphorylated form of α-synuclein, further increased by copper treatment, without modifications in α-synuclein levels. This effect depended on the upregulation of the polo-like kinase 2 (PLK2), whereas the levels of the relative protein phosphatase 2A (PP2A) remained unvaried. No changes in the oxidative state of the cells were identified. The Cu dependent alteration of α-synuclein phosphorylation pattern might potentially offer new opportunities for clinical intervention.

Multiplicity of states in Taylor-Couette flow of a dense granular gas

Molecular dynamics simulations with a purely repulsive Lennard-Jones potential and a normal damping force is used to simulate the granular flow in the annular region between two differentially-rotating cylinders, called the Taylor-Couette flow. The flow transition from the azimuthally-invariant Circular Couette flow (CCF) to the Taylor-vortex flow (TVF) is studied by increasing the rotation rate (ωi) of the inner cylinder, with the outer cylinder being kept stationary. Multiplicity of states, highlighting the hysteretic nature of the “CCF ↔ TVF” transition, is observed over a wide range of rotation rates. The onset of Taylor vortices is quantified in terms of the maximum radial velocity and the net circulation per vortex.

Correlating STED and synchrotron XRF nano-imaging unveils cosegregation of metals and cytoskeleton proteins in dendrites

Zinc and copper are involved in neuronal differentiation and synaptic plasticity but the molecular mechanisms behind these processes are still elusive due in part to the difficulty of imaging trace metals together with proteins at the synaptic level. We correlate stimulated-emission-depletion microscopy of proteins and synchrotron X-ray fluorescence imaging of trace metals, both performed with 40 nm spatial resolution, on primary rat hippocampal neurons. We reveal the co-localization at the nanoscale of zinc and tubulin in dendrites with a molecular ratio of about one zinc atom per tubulin-αβ dimer. We observe the co-segregation of copper and F-actin within the nano-architecture of dendritic protrusions. In addition, zinc chelation causes a decrease in the expression of cytoskeleton proteins in dendrites and spines. Overall, these results indicate new functions for zinc and copper in the modulation of the cytoskeleton morphology in dendrites, a mechanism associated to neuronal plasticity and memory formation.

Exposure of the SH-SY5Y Human Neuroblastoma Cells to 50-Hz Magnetic Field: Comparison Between Two-Dimensional (2D) and Three-Dimensional (3D) In Vitro Cultures

We here characterize the response to the extremely low-frequency (ELF) magnetic field (MF, 50 Hz, 1 mT) of SH-SY5Y human neuroblastoma cells, cultured in a three-dimensional (3D) Alvetex^® scaffold compared to conventional two-dimensional (2D) monolayers. We proved that the growing phenotype of proliferating SH-SY5Y cells is not affected by the culturing conditions, as morphology, cell cycle distribution, proliferation/differentiation gene expression of 3D-cultures overlap what reported in 2D plates. In response to 72-h exposure to 50-Hz MF, we demonstrated that no proliferation change and apoptosis activation occur in both 2D and 3D cultures. Consistently, no modulation of Ki67, MYCN, CCDN1, and Nestin, of invasiveness and neo-angiogenesis-controlling genes (HIF-1α, VEGF, and PDGF) and of microRNA epigenetic signature (miR-21-5p, miR-222-3p and miR-133b) is driven by ELF exposure. Conversely, intracellular glutathione content and SOD1 expression are exclusively impaired in 3D-culture cells in response to the MF, whereas no change of such redox modulators is observed in SH-SY5Y cells if grown on 2D monolayers. Moreover, ELF-MF synergizes with the differentiating agents to stimulate neuroblastoma differentiation into a dopaminergic (DA) phenotype in the 3D-scaffold culture only, as growth arrest and induction of p21, TH, DAT, and GAP43 are reported in ELF-exposed SH-SY5Y cells exclusively if grown on 3D scaffolds. As overall, our findings prove that 3D culture is a more reliable experimental model for studying SH-SY5Y response to ELF-MF if compared to 2D conventional monolayer, and put the bases for promoting 3D systems in future studies addressing the interaction between electromagnetic fields and biological systems.

In Vivo Imaging with Genetically Encoded Redox Biosensors

Redox reactions are of high fundamental and practical interest since they are involved in both normal physiology and the pathogenesis of various diseases. However, this area of research has always been a relatively problematic field in the context of analytical approaches, mostly because of the unstable nature of the compounds that are measured. Genetically encoded sensors allow for the registration of highly reactive molecules in real-time mode and, therefore, they began a new era in redox biology. Their strongest points manifest most brightly in in vivo experiments and pave the way for the non-invasive investigation of biochemical pathways that proceed in organisms from different systematic groups. In the first part of the review, we briefly describe the redox sensors that were used in vivo as well as summarize the model systems to which they were applied. Next, we thoroughly discuss the biological results obtained in these studies in regard to animals, plants, as well as unicellular eukaryotes and prokaryotes. We hope that this work reflects the amazing power of this technology and can serve as a useful guide for biologists and chemists who work in the field of redox processes.

L-Cysteine-mediated modulation of copper trafficking in prostate cancer cells: an in vitro and in vivo investigation with 64Cu and 64Cu-PET

Copper imbalance is implicated in many diseases, including cancer. Copper in blood is mainly transported by carrier proteins but a small fraction is bound to low molecular weight species, possibly amino acids. Their roles in cellular copper delivery are unknown. Our aim was to test whether accumulation of 64Cu into cancer-derived cells can be influenced by copper-binding serum amino acids. In vitro cellular accumulation of 64Cu was measured in Hank's Balanced Salt Solution in the presence of 100 μM l-histidine, l-methionine, l-cysteine and l-threonine. l-Cysteine markedly increased 64Cu accumulation and retention in DU145, PC3 and SK-OV-3 cells, while some other cell lines did not show an effect. This effect was not due to 64Cu delivery in the form of a 64Cu-cysteine complex, nor to reduction of 64Cu(ii) to 64Cu(i) by l-cysteine. Pre-incubation of cells with l-cysteine increased 64Cu accumulation, even if l-cysteine was removed from HBSS before 64Cu was added. The effect of l-cysteine on 64Cu accumulation was not mediated by increased glutathione synthesis. Despite the demonstrable in vitro effect, pre-injection of l-cysteine precursor N-acetyl-cysteine (NAC) in vivo did not enhance 64Cu delivery to DU145 xenografts in mice. Instead, it decreased 64Cu accumulation in the DU145 tumour and in brain, as assessed by PET imaging. We conclude that 64Cu is not delivered to DU145 cancer cells in vitro as a complex with amino acids but its cellular accumulation is enhanced by l-cysteine or NAC influx to cells. The latter effect was not demonstrable in vivo in the DU145 xenograft.

Copper metabolism as a unique vulnerability in cancer

The last 25 years have witnessed tremendous progress in identifying and characterizing proteins that regulate the uptake, intracellular trafficking and export of copper. Although dietary copper is required in trace amounts, sufficient quantities of this metal are needed to sustain growth and development in humans and other mammals. However, copper is also a rate-limiting nutrient for the growth and proliferation of cancer cells. Oral copper chelators taken with food have been shown to confer anti-neoplastic and anti-metastatic benefits in animals and humans. Recent studies have begun to identify specific roles for copper in pathways of oncogenic signaling and resistance to anti-neoplastic drugs. Here, we review the general mechanisms of cellular copper homeostasis and discuss roles of copper in cancer progression, highlighting metabolic vulnerabilities that may be targetable in the development of anticancer therapies.

Clioquinol inhibits dopamine-β-hydroxylase secretion and noradrenaline synthesis by affecting the redox status of ATOX1 and copper transport in human neuroblastoma SH-SY5Y cells

Clioquinol (5-chloro-7-indo-8-quinolinol), a chelator and ionophore of copper/zinc, was extensively used as an amebicide to treat indigestion and diarrhea in the mid-1900s. However, it was withdrawn from the market in Japan because its use was epidemiologically linked to an increase in the incidence of subacute myelo-optic neuropathy (SMON). SMON is characterized by the subacute onset of sensory and motor disturbances in the lower extremities with occasional visual impairments, which are preceded by abdominal symptoms. Although pathological studies demonstrated axonopathy of the spinal cord and optic nerves, the underlying mechanisms of clioquinol toxicity have not been elucidated in detail. In the present study, a reporter assay revealed that clioquinol (20-50 µM) activated metal response element-dependent transcription in human neuroblastoma SH-SY5Y cells. Clioquinol significantly increased the cellular level of zinc within 1 h, suggesting zinc influx due to its ionophore effects. On the other hand, clioquinol (20-50 µM) significantly increased the cellular level of copper within 24 h. Clioquinol (50 µM) induced the oxidation of the copper chaperone antioxidant 1 (ATOX1), suggesting its inactivation and inhibition of copper transport. The secretion of dopamine-β-hydroxylase (DBH) and lysyl oxidase, both of which are copper-dependent enzymes, was altered by clioquinol (20-50 µM). Noradrenaline levels were reduced by clioquinol (20-50 µM). Disruption of the ATOX1 gene suppressed the secretion of DBH. This study suggested that the disturbance of cellular copper transport by the inactivation of ATOX1 is one of the mechanisms involved in clioquinol-induced neurotoxicity in SMON.

The rise of bio-inspired polymer compartments responding to pathology-related signals

Self-organized nano- and microscale polymer compartments such as polymersomes, giant unilamellar vesicles (GUVs), polyion complex vesicles (PICsomes) and layer-by-layer (LbL) capsules have increasing potential in many sensing applications. Besides modifying the physicochemical properties of the corresponding polymer building blocks, the versatility of these compartments can be markedly expanded by biomolecules that endow the nanomaterials with specific molecular and cellular functions. In this review, we focus on polymer-based compartments that preserve their structure, and highlight the key role they play in the field of medical diagnostics: first, the self-assembling abilities that result in preferred architectures are presented for a broad range of polymers. In the following, we describe different strategies for sensing disease-related signals (pH-change, reductive conditions, and presence of ions or biomolecules) by polymer compartments that exhibit stimuli-responsiveness. In particular, we distinguish between the stimulus-sensitivity contributed by the polymer itself or by additional compounds embedded in the compartments in different sensing systems. We then address necessary properties of sensing polymeric compartments, such as the enhancement of their stability and biocompatibility, or the targeting ability, that open up new perspectives for diagnostic applications.

The Redox Theory of Development

Significance: The geological record shows that as atmospheric O2 levels increased, it concomitantly coincided with the evolution of metazoans. More complex, higher organisms contain a more cysteine-rich proteome, potentially as a means to regulate homeostatic responses in a more O2-rich environment. Regulation of redox-sensitive processes to control development is likely to be evolutionarily conserved. Recent Advances: During early embryonic development, the conceptus is exposed to varying levels of O2. Oxygen and redox-sensitive elements can be regulated to promote normal development, defined as changes to cellular mass, morphology, biochemistry, and function, suggesting that O2 is a developmental morphogen. During periods of O2 fluctuation, embryos are "reprogrammed," on the genomic and metabolic levels. Reprogramming imparts changes to particular redox couples (nodes) that would support specific post-translational modifications (PTMs), targeting the cysteine proteome to regulate protein function and development. Critical Issues: Major developmental events such as stem cell expansion, proliferation, differentiation, migration, and cell fate decisions are controlled through oxidative PTMs of cysteine-based redox nodes. As such, timely coordinated redox regulation of these events yields normal developmental outcomes and viable species reproduction. Disruption of normal redox signaling can produce adverse developmental outcomes. Future Directions: Furthering our understanding of the redox-sensitive processes/pathways, the nature of the regulatory PTMs involved in development and periods of activation/sensitivity to specific developmental pathways would greatly support the theory of redox regulation of development, and would also provide rationale and direction to more fully comprehend poor developmental outcomes, such as dysmorphogenesis, functional deficits, and preterm embryonic death.

Human glutaredoxin-1 can transfer copper to isolated metal binding domains of the P1B-type ATPase, ATP7B

Intracellular copper (Cu) in eukaryotic organisms is regulated by homeostatic systems, which rely on the activities of soluble metallochaperones that participate in Cu exchange through highly tuned protein-protein interactions. Recently, the human enzyme glutaredoxin-1 (hGrx1) has been shown to possess Cu metallochaperone activity. The aim of this study was to ascertain whether hGrx1 can act in Cu delivery to the metal binding domains (MBDs) of the P_1B-type ATPase ATP7B and to determine the thermodynamic factors that underpin this activity. hGrx1 can transfer Cu to the metallochaperone Atox1 and to the MBDs 5-6 of ATP7B (WLN5-6). This exchange is irreversible. In a mixture of the three proteins, Cu is delivered to the WLN5-6 preferentially, despite the presence of Atox1. This preferential Cu exchange appears to be driven by both the thermodynamics of the interactions between the proteins pairs and of the proteins with Cu(I). Crucially, protein-protein interactions between hGrx1, Atox1 and WLN5-6 were detected by NMR spectroscopy both in the presence and absence of Cu at a common interface. This study augments the possible activities of hGrx1 in intracellular Cu homeostasis and suggests a potential redundancy in this system, where hGrx1 has the potential to act under cellular conditions where the activity of Atox1 in Cu regulation is attenuated.

Inorganic Biomaterials for Regenerative Medicine

Regenerative medicine leverages the innate potential of the human body to efficiently repair and regenerate damaged tissues using engineered biomaterials. By designing responsive biomaterials with the appropriate biophysical and biochemical characteristics, cellular response can be modulated to direct tissue healing. Recently, inorganic biomaterials have been shown to regulate cellular responses including cell-cell and cell-matrix interactions. Moreover, ions released from these mineral-based biomaterials play a vital role in defining cell identity, as well as driving tissue-specific functions. The intrinsic properties of inorganic biomaterials, such as the release of bioactive ions (e.g., Ca, Mg, Sr, Si, B, Fe, Cu, Zn, Cr, Co, Mo, Mn, Au, Ag, V, Eu, and La), can be leveraged to induce phenotypic changes in cells or modulate the immune microenvironment to direct tissue healing and regeneration. Biophysical characteristics of biomaterials, such as topography, charge, size, electrostatic interactions, and stiffness can be modulated by addition of inorganic micro- and nanoparticles to polymeric networks have also been shown to play an important role in their biological response. In this Review, we discuss the recent emergence of inorganic biomaterials to harness the innate regenerative potential of the body. Specifically, we will discuss various biophysical or biochemical effects of inorganic-based materials in directing cellular response for regenerative medicine applications.

Visualization of the Redox Status of Cytosolic Glutathione Using the Organelle- and Cytoskeleton-Targeted Redox Sensors

Glutathione is a small thiol-containing peptide that plays a central role in maintaining cellular redox homeostasis. Glutathione serves as a physiologic redox buffer by providing thiol electrons for catabolizing harmful oxidants and reversing oxidative effects on biomolecules. Recent evidence suggests that the balance of reduced and oxidized glutathione (GSH/GSSG) defines the redox states of Cys residues in proteins and fine-tunes their stabilities and functions. To elucidate the redox balance of cellular glutathione at subcellular resolution, a number of redox-sensitive green fluorescent protein (roGFP) variants have been developed. In this study, we constructed and functionally validated organelle- and cytoskeleton-targeted roGFP and elucidated the redox status of the cytosolic glutathione at a subcellular resolution. These new redox sensors firmly established a highly reduced redox equilibrium of cytosolic glutathione, wherein significant deviation was observed among cells. By targeting the sensor to the cytosolic and lumen sides of the Golgi membrane, we identified a prominent redox gradient across the biological membrane at the Golgi body. The results demonstrated that organelle- and cytoskeleton-targeted sensors enable the assessment of glutathione oxidation near the cytosolic surfaces of different organelle membranes.

Neuron-glia: understanding cellular copper homeostasis, its cross-talk and their contribution towards neurodegenerative diseases

Over the years, the mechanism of copper homeostasis in various organ systems has gained importance. This is owing to the involvement of copper in a wide range of genetic disorders, most of them involving neurological symptoms. This highlights the importance of copper and its tight regulation in a complex organ system like the brain. It demands understanding the mechanism of copper acquisition and delivery to various cell types overcoming the limitation imposed by the blood brain barrier. The present review aims to investigate the existing work to understand the mechanism and complexity of cellular copper homeostasis in the two major cell types of the CNS - the neurons and the astrocytes. It investigates the mechanism of copper uptake, incorporation and export by these cell types. Furthermore, it brings forth the common as well as the exclusive aspects of neuronal and glial copper homeostasis including the studies from copper-based sensors. Glia act as a mediator of copper supply between the endothelium and the neurons. They possess all the qualifications of acting as a 'copper-sponge' for supply to the neurons. The neurons, on the other hand, require copper for various essential functions like incorporation as a cofactor for enzymes, synaptogenesis, axonal extension, inhibition of postsynaptic excitotoxicity, etc. Lastly, we also aim to understand the neuronal and glial pathology in various copper homeostasis disorders. The etiology of glial pathology and its contribution towards neuronal pathology and vice versa underlies the complexity of the neuropathology associated with the copper metabolism disorders.