Cellular Zn Research Articles

ZIP11 Regulates Nuclear Zinc Homeostasis in HeLa Cells and Is Required for Proliferation and Establishment of the Carcinogenic Phenotype.

Zinc (Zn) is an essential trace element that plays a key role in several biological processes, including transcription, signaling, and catalysis. A subcellular network of transporters ensures adequate distribution of Zn to facilitate homeostasis. Among these are a family of importers, the Zrt/Irt-like proteins (ZIP), which consists of 14 members (ZIP1-ZIP14) that mobilize Zn from the extracellular domain and organelles into the cytosol. Expression of these transporters varies among tissues and during developmental stages, and their distribution at various cellular locations is essential for defining the net cellular Zn transport. Normally, the ion is bound to proteins or sequestered in organelles and vesicles. However, though research has focused on Zn internalization in mammalian cells, little is known about Zn mobilization within organelles, including within the nuclei under both normal and pathological conditions. Analyses from stomach and colon tissues isolated from mouse suggested that ZIP11 is the only ZIP transporter localized to the nucleus of mammalian cells, yet no clear cellular role has been attributed to this protein. We hypothesized that ZIP11 is essential to maintaining nuclear Zn homeostasis in mammalian cells. To test this, we utilized HeLa cells, as research in humans correlated elevated expression of ZIP11 with poor prognosis in cervical cancer patients. We stably knocked down ZIP11 in HeLa cancer cells and investigated the effect of Zn dysregulation in vitro. Our data show that ZIP11 knockdown (KD) reduced HeLa cells proliferation due to nuclear accumulation of Zn. RNA-seq analyses revealed that genes related to angiogenesis, apoptosis, mRNA metabolism, and signaling pathways are dysregulated. Although the KD cells undergoing nuclear Zn stress can activate the homeostasis response by MTF1 and MT1, the RNA-seq analyses showed that only ZIP14 (an importer expressed on the plasma membrane and endocytic vesicles) is mildly induced, which may explain the sensitivity to elevated levels of extracellular Zn. Consequently, ZIP11 KD HeLa cells have impaired migration, invasive properties and decreased mitochondrial potential. Furthermore, KD of ZIP11 delayed cell cycle progression and rendered an enhanced senescent state in HeLa cells, pointing to a novel mechanism whereby maintenance of nuclear Zn homeostasis is essential for cancer progression.

Methionine metabolism regulates pluripotent stem cell pluripotency and differentiation through zinc mobilization.

Pluripotent stem cells (PSCs) exhibit a unique feature that requires S-adenosylmethionine (SAM) for the maintenance of their pluripotency. Methionine deprivation in the medium causes a reduction in intracellular SAM, thus rendering PSCs in a state potentiated for differentiation. In this study, we find that methionine deprivation triggers a reduction in intracellular protein-bound Zn content and upregulation of Zn exporter SLC30A1 in PSCs. Culturing PSCs in Zn-deprived medium results in decreased intracellular protein-bound Zn content, reduced cell growth, and potentiated differentiation, which partially mimics methionine deprivation. PSCs cultured under Zn deprivation exhibit an altered methionine metabolism-related metabolite profile. We conclude that methionine deprivation potentiates differentiation partly by lowering cellular Zn content. We establish a protocol to generate functional pancreatic β cells by applying methionine and Zn deprivation. Our results reveal a link between Zn signaling and methionine metabolism in the regulation of cell fate in PSCs.

Interplay between Zn2+ Homeostasis and Mitochondrial Functions in Cardiovascular Diseases and Heart Ageing.

Zinc plays an important role in cardiomyocytes, where it exists in bound and histochemically reactive labile Zn2+ forms. Although Zn2+ concentration is under tight control through several Zn2+-transporters, its concentration and intracellular distribution may vary during normal cardiac function and pathological conditions, when the protein levels and efficacy of Zn2+ transporters can lead to zinc re-distribution among organelles in cardiomyocytes. Such dysregulation of cellular Zn2+ homeostasis leads to mitochondrial and ER stresses, and interrupts normal ER/mitochondria cross-talk and mitophagy, which subsequently, result in increased ROS production and dysregulated metabolic function. Besides cardiac structural and functional defects, insufficient Zn2+ supply was associated with heart development abnormalities, induction and progression of cardiovascular diseases, resulting in accelerated cardiac ageing. In the present review, we summarize the recently identified connections between cellular and mitochondrial Zn2+ homeostasis, ER stress and mitophagy in heart development, excitation–contraction coupling, heart failure and ischemia/reperfusion injury. Additionally, we discuss the role of Zn2+ in accelerated heart ageing and ageing-associated rise of mitochondrial ROS and cardiomyocyte dysfunction.

Zn-regulated GTPase metalloprotein activator 1 modulates vertebrate zinc homeostasis

Zinc (Zn) is an essential micronutrient and cofactor for up to 10% of proteins in living organisms. During Zn limitation, specialized enzymes called metallochaperones are predicted to allocate Zn to specific metalloproteins. This function has been putatively assigned to G3E GTPase COG0523 proteins, yet no Zn metallochaperone has been experimentally identified in any organism. Here, we functionally characterize a family of COG0523 proteins that is conserved across vertebrates. We identify Zn metalloprotease methionine aminopeptidase 1 (METAP1) as a COG0523 client, leading to the redesignation of this group of COG0523 proteins as the Zn-regulated GTPase metalloprotein activator (ZNG1) family. Using biochemical, structural, genetic, and pharmacological approaches across evolutionarily divergent models, including zebrafish and mice, we demonstrate a critical role for ZNG1 proteins in regulating cellular Zn homeostasis. Collectively, these data reveal the existence of a family of Zn metallochaperones and assign ZNG1 an important role for intracellular Zn trafficking.

Molecular Characterization and the Essential Biological Function of the Metal Chaperone Protein MtmA in Aspergillus fumigatus.

The detoxification system of reactive oxygen species (ROS) plays critical roles in the survival and virulence of fungal pathogens in infected hosts, while superoxide dismutase (SOD) is the primary ROS scavenger. In the model yeast Saccharomyces cerevisiae, the metal chaperone protein Mtm1 is required for mitochondrial Sod2 activation and responses to oxidative stress. However, the function of the S. cerevisiae Mtm1 homolog in the human fungal pathogen Aspergillus fumigatus has not yet been clarified. In this study, we found that mitochondria-localized MtmA in A. fumigatus, a putative homolog of yeast Mtm1, not only has a similar function to Mtm1 in responding to oxidative stress resistance by affecting SodB (MnSOD) activity but is also essential for hyphal growth such that repressed expression of MtmA results in severe growth defects in A. fumigatus. In addition, the chelation of Zn2+ can obviously rescue growth defects caused by repression of MtmA, suggesting that MtmA may be involved in hyphal growth by affecting cellular Zn2+ detoxification. Moreover, MtmA contains four Mito-carr domains, whereas only the first Mito-carr domain is required for the function of MtmA. Therefore, the findings in this study suggest that MtmA in A. fumigatus has an important and unique function that is different from that in yeast. IMPORTANCE Knowledge of the key factors required for the viability of pathogenic fungi can help to explore new antifungal drugs. Here, we demonstrate that MtmA is involved in responding to oxidative stress by activating mitochondrial SodB activity. MtmA, especially for the first Mito-carr domain, is essential for colony growth by regulating cellular Zn2+ equilibrium and responses to oxidative stress in A. fumigatus. This is the first report of the vital and unique role of the MtmA protein in pathogenic fungi, indicating that it might be a potential antifungal drug target.

A plausible model for the outward-facing conformation of YiiP and its transport mechanism

The zinc/proton antiporter YiiP from Escherichia coli, a member of the cation diffusion facilitator family, plays an important role in maintaining cellular Zn2+ homeostasis. The difference between experimental inward-facing (IF) and outward-facing (OF) structures suggested a transport model involving large-scale scissoring of the transmembrane domains (TMDs). However, several experiments on YiiP and its mammalian homolog ZnT8 showed that this scissor-like rotation was not necessary for transport activity.

Bioimaging revealed contrasting organelle-specific transport of copper and zinc and implication for toxicity

Zn and Cu are two of the essential trace elements and it is important to understand the regulation of their distribution on cellular functions. Herein, we for the first time investigated the subcellular fate and behavior of Zn and Cu in zebrafish cells through bioimaging, and demonstrated the completely different behaviors of Zn and Cu. The distribution of Zn2+ was concentration-dependent, and Zn2+ at low concentration was predominantly located in the lysosomes (76.5%). A further increase of cellular Zn2+ resulted in a spillover and more diffusive distribution, with partitioning to mitochondria and other regions. In contrast, the subcellular distribution of Cu+ was time-dependent. Upon entering the cells, Cu2+ was reduced to Cu+, which was first concentrated in the mitochondria (71.4%) followed by transportation to lysosomes (58.6%), and finally removal from the cell. With such differential transportation, Cu2+ instead of Zn2+ had a negative effect on the mitochondrial membrane potential and glutathione. Correspondingly, the pH of lysosomes was more sensitive to Zn2+ exposure and decreased with increasing internalized Zn2+, whereas it increased upon Cu2+ exposure. The responses of cellular pH showed an opposite pattern from the lysosomal pH. Lysosome was the most critical organelle in response to incoming Zn2+ by increasing its number and size, whereas Cu2+ reduced the lysosome size. Our study showed that Zn2+ and Cu2+ had completely different cellular handlings and fates with important implications for understanding of their toxicity.

Efeitos de tratamentos com nanopartículas e estresse salino na estrutura genética e características fisiológicas de Lavandula angustifolia Mill.

Lavandula angustifolia Mill. is an aromatic herb of the Lamiaceae family, which has been widely used by humans for many centuries. In the current study, we treated L. angustifolia samples with various concentrations of ZnO and Fe2O3 nanoparticles in the presence/ absence of NaCl salinity stress to evaluate the composition of essential oils, genetic structure, glandular trichome density and cellular Zn2+ and Fe2+ contents. We used Inter Simple Sequence Repeat (ISSR) molecular markers to investigate the parameters of genetic diversity among the treated samples. Furthermore, the hydro-distilled essential oil from the aerial parts of the samples was subjected to GC and GC / MS analyses. SPSS ver. 15, PAST, PopGene, and GenAlex software were employed for statistical analyses. Intracellular concentrations of Fe2+ and Zn2+ differed under various concentrations of nanoparticles and salinity treatments, and a significant negative correlation was observed between these elements, however, nanoparticles treatment significantly increased intracellular concentrations of iron and zinc ions. We found four types of glandular trichomes on the surface of the leaf of the treated plants, and the ANOVA test revealed a significant variation for most of them. Meanwhile, the short-stalked capitate trichomes were the most frequent in most of the evaluated samples. The main and trace essential oil compounds were the same among the treated plants, meanwhile, their percentages varied among the samples. The percentages of 1,8- cineole and camphor decreased in treated plants, which affects the quality of essential oils. Parameters of genetic diversity differed among the treated samples. Furthermore, the AMOVA test demonstrated a significant genetic variation that its substantial part belonged to among treated samples. These findings revealed that the treatment of nanoparticles and salinity stress strongly influenced the genetic diversity, trichomes density, iron and zinc ions content in lavender plants.

The cytotoxicity of zinc oxide nanoparticles to 3D brain organoids results from excessive intracellular zinc ions and defective autophagy.

Although the neurotoxicity of ZnO nanoparticles (NPs) has been evaluated in animal and nerve cell culture models, these models cannot accurately mimic human brains. Three-dimensional (3D) brain organoids based on human-induced pluripotent stem cells have been developed to study the human brains, but this model has rarely been used to evaluate NP neurotoxicity. We used 3D brain organoids that express cortical layer proteins to investigate the mechanisms of ZnO NP-induced neurotoxicity. Cytotoxicity caused by high levels of ZnO NPs (64μg/mL) correlated with high intracellular Zn ion levels but not superoxide levels. Exposure to a non-cytotoxic concentration of ZnO NPs (16μg/mL) increased the autophagy-marker proteins LC3B-II/I but decreased p62 accumulation, whereas a cytotoxic concentration of ZnO NPs (64μg/mL) decreased LC3B-II/I proteins but did not affect p62 accumulation. Fluorescence micro-optical sectioning tomography revealed that 64μg/mL ZnO NPs led to decreases in LC3B proteins that were more obvious at the outer layers of the organoids, which were directly exposed to the ZnO NPs. In addition to reducing LC3B proteins in the outer layers, ZnO NPs increased the number of micronuclei in the outer layers but not the inner layers (where LC3B proteins were still expressed). Adding the autophagy flux inhibitor bafilomycin A1 to ZnO NPs increased cytotoxicity and intracellular Zn ion levels, but adding the autophagy inducer rapamycin only slightly decreased cellular Zn ion levels. We conclude that high concentrations of ZnO NPs are cytotoxic to 3D brain organoids via defective autophagy and intracellular accumulation of Zn ions.

The cell biology of zinc.

Nearly 10% of all plant proteins belong to the zinc (Zn) proteome. They require Zn either for catalysis or as a structural element. Most of the protein-bound Zn in eukaryotic cells is found in the cytosol. The fundamental differences between transition metal cations in the stability of their complexes with organic ligands, as described by the Irving-Williams series, necessitate buffering of cytosolic Zn (the 'free Zn' pool) in the picomolar range (i.e. ~6 orders of magnitude lower than the total cellular concentration). Various metabolites and peptides, including nicotianamine, glutathione, and phytochelatins, serve as Zn buffers. They are hypothesized to supply Zn to enzymes, transporters, or the recently identified sensor proteins. Zn2+ acquisition is mediated by ZRT/IRT-like proteins. Metal tolerance proteins transport Zn2+ into vacuoles and the endoplasmic reticulum, the major Zn storage sites. Heavy metal ATPase-dependent efflux of Zn2+ is another mechanism to control cytosolic Zn. Spatially controlled Zn2+ influx or release from intracellular stores would result in dynamic modulation of cellular Zn pools, which may directly influence protein-protein interactions or the activities of enzymes involved in signaling cascades. Possible regulatory roles of such changes, as recently elucidated in mammalian cells, are discussed.

Redundant roles of four ZIP family members in zinc homeostasis and seed development in Arabidopsis thaliana.

Zinc (Zn) is essential for normal plant growth and development. The Zn-regulated transporter, iron-regulated transporter (IRT)-like protein (ZIP) family members are involved in Zn transport and cellular Zn homeostasis throughout the domains of life. In this study, we have characterized four ZIP transporters from Arabidopsis thaliana (IRT3, ZIP4, ZIP6, and ZIP9) to better understand their functional roles. The four ZIP proteins can restore the growth defect of a yeast Zn uptake mutant and are upregulated under Zn deficiency. Single and double mutants show no phenotypes under Zn-sufficient or Zn-limited growth conditions. In contrast, triple and quadruple mutants show impaired growth irrespective of external Zn supply due to reduced Zn translocation from root to shoot. All four ZIP genes are highly expressed during seed development, and siliques from all single and higher-order mutants exhibited an increased number of abnormal seeds and decreased Zn levels in mature seeds relative to wild type. The seed phenotypes could be reversed by supplementing the soil with Zn. Our data demonstrate that IRT3, ZIP4, ZIP6, and ZIP9 function redundantly in maintaining Zn homeostasis and seed development in A. thaliana.

Zinc Signaling in the Mammary Gland: For Better and for Worse.

Zinc (Zn2+) plays an essential role in epithelial physiology. Among its many effects, most prominent is its action to accelerate cell proliferation, thereby modulating wound healing. It also mediates affects in the gastrointestinal system, in the testes, and in secretory organs, including the pancreas, salivary, and prostate glands. On the cellular level, Zn2+ is involved in protein folding, DNA, and RNA synthesis, and in the function of numerous enzymes. In the mammary gland, Zn2+ accumulation in maternal milk is essential for supporting infant growth during the neonatal period. Importantly, Zn2+ signaling also has direct roles in controlling mammary gland development or, alternatively, involution. During breast cancer progression, accumulation or redistribution of Zn2+ occurs in the mammary gland, with aberrant Zn2+ signaling observed in the malignant cells. Here, we review the current understanding of the role of in Zn2+ the mammary gland, and the proteins controlling cellular Zn2+ homeostasis and signaling, including Zn2+ transporters and the Gq-coupled Zn2+ sensing receptor, ZnR/GPR39. Significant advances in our understanding of Zn2+ signaling in the normal mammary gland as well as in the context of breast cancer provides new avenues for identification of specific targets for breast cancer therapy.

Winter dissolved and particulate zinc in the Indian Sector of the Southern Ocean: Distribution and relation to major nutrients (GEOTRACES GIpr07 transect)

First winter measurements of dissolved zinc (dZn) and particulate zinc (pZn) are presented from seven stations, between 41 and 58°S, occupied in July 2017 along the 30°E longitude in the Indian Sector of the Southern Ocean. This unique spatial and seasonal dataset provided the opportunity to investigate Zn biogeochemical cycling in a region which is extremely data scarce and during a period when conditions are unfavourable for phytoplankton growth. Surface comparisons of our winter dZn and pZn to previous measurements during spring and summer revealed that Zn seasonality is most pronounced at the higher latitudes where higher dZn (and higher ratios of dZn to phosphate; dZn:PO4) and lower pZn in winter reflect decreased biological uptake and preferential dZn resupply (relative to PO4) to surface waters through deep winter mixing. The composition of pZn was majorly biogenic however localised lithogenic inputs were attributed to potential hydrothermal activity and transport of continental sediment via Agulhas waters. Calculated vertical attenuation factors (b values) for pZn (0.31) and phosphorus (P; 0.41) suggest that Zn has a longer remineralisation length scale than P, providing a mechanism as to why dZn appears to be remineralised deeper in the water column than PO4. Ratios of pZn to P (pZn:P) in surface waters increased with latitude from 1.12 to 8.28 mmol mol−1 due to increased dZn availability and the dominance of diatoms (with high cellular Zn quotas) in the high latitude Antarctic Zone (AAZ). Interestingly, the high surface pZn:P ratios in the AAZ did not change significantly with depth (in contrast to the northern stations where pZn:P increased with depth) suggesting the export of diatom cells below the winter mixed layer where remineralisation and rigorous mixing may resolve the linear dZn to silicic acid (dZn:Si(OH)4) correlation (dZn (nmol kg−1) = 0.064 Si(OH)4 (μmol kg−1) + 0.690; r2 = 0.93; n = 120) despite these elements being located in separate components of the diatom cell. Additionally, elevated concentrations of dZn and Si(OH)4 below 3000 m in the AAZ may reflect nutrient accumulation in bottom waters where northward flow is inhibited by the Indian mid-Ocean ridge.

An Integrated Mass Spectrometry and Molecular Dynamics Simulations Approach Reveals the Spatial Organization Impact of Metal-Binding Sites on the Stability of Metal-Depleted Metallothionein-2 Species.

Mammalian metallothioneins (MTs) are a group of cysteine-rich proteins that bind metal ions in two α- and β-domains and represent a major cellular Zn(II)/Cu(I) buffering system in the cell. At cellular free Zn(II) concentrations (10–11–10–9 M), MTs do not exist in fully loaded forms with seven Zn(II)-bound ions (Zn7MTs). Instead, MTs exist as partially metal-depleted species (Zn4–6MT) because their Zn(II) binding affinities are on the nano- to picomolar range comparable to the concentrations of cellular Zn(II). The mode of action of MTs remains poorly understood, and thus, the aim of this study is to characterize the mechanism of Zn(II) (un)binding to MTs, the thermodynamic properties of the Zn1–6MT2 species, and their mechanostability properties. To this end, native mass spectrometry (MS) and label-free quantitative bottom-up and top-down MS in combination with steered molecular dynamics simulations, well-tempered metadynamics (WT-MetaD), and parallel-bias WT-MetaD (amounting to 3.5 μs) were integrated to unravel the chemical coordination of Zn(II) in all Zn1–6MT2 species and to explain the differences in binding affinities of Zn(II) ions to MTs. Differences are found to be the result of the degree of water participation in MT (un)folding and the hyper-reactive character of Cys21 and Cys29 residues. The thermodynamics properties of Zn(II) (un)binding to MT2 are found to differ from those of Cd(II), justifying their distinctive roles. The potential of this integrated strategy in the investigation of numerous unexplored metalloproteins is attested by the results highlighted in the present study.

The Evolving Role for Zinc and Zinc Transporters in Cadmium Tolerance and Urothelial Cancer

Cadmium (Cd) is an environmental toxicant with serious public health consequences due to its persistence within arable soils, and the ease with which it enters food chains and then, accumulates in human tissues to induce a broad range of adverse health effects. The present review focuses on the role of zinc (Zn), a nutritionally essential metal, to protect against the cytotoxicity and carcinogenicity of Cd in urinary bladder epithelial cells. The stress responses and defense mechanisms involving the low-molecular-weight metal binding protein, metallothionein (MT), are highlighted. The efflux and influx transporters of the ZnT and Zrt-/Irt-like protein (ZIP) gene families are discussed with respect to their putative role in retaining cellular Zn homeostasis. Among fourteen ZIP family members, ZIP8 and ZIP14 mediate Cd uptake by cells, while ZnT1 is among ten ZnT family members solely responsible for efflux of Zn (Cd), representing cellular defense against toxicity from excessively high Zn (Cd) intake. In theory, upregulation of the efflux transporter ZnT1 concomitant with the downregulation of influx transporters such as ZIP8 and ZIP14 can prevent Cd accumulation by cells, thereby increasing tolerance to Cd toxicity. To link the perturbation of Zn homeostasis, reflected by the aberrant expression of ZnT1, ZIP1, ZIP6, and ZIP10, with malignancy, tolerance to Cd toxicity acquired during Cd-induced transformation of a cell model of human urothelium, UROtsa, is discussed as a particular example.

Transcription Factors as Zinc Sensors in Plants.

Zinc (Zn) is an essential nutrient; however, understanding the sensing of cellular Zn status in plants has remained elusive. Recently, Lilay et al. identified a nuclear Zn-sensing mechanism where the conserved zinc sensor motif of Basic Leucine Zipper 19 (bZIP19) and bZIP23 transcription factors (TFs) bind to Zn2+ and coordinate their activity according to Zn availability.

Combined effects of different sizes of ZnO and ZIF-8 nanoparticles co-exposure with Cd2+ on HepG2 cells

Heavy metal and nanoparticles (NPs) emitted in the environment have attracted worldwide attention. But the combined effect of NPs and heavy metals is still unclear. In this study, the combined effect of zinc-based NPs and Cd2+ on HepG2 cells was investigated by combining biological indicator detection methods with time-resolved inductively coupled plasma mass spectrometry (TRA-ICP-MS) single cell analysis, and the combined effect of Zn2+ and Cd2+ was also investigated for a comparison. High-dose of ZnO or ZIF-8 NPs co-exposure with Cd2+ would reduce the cell viability while low-dose of ZnO or ZIF-8 NPs co-exposure with Cd2+showed antagonism and the particle size has no remarkable effect on the combined toxicity. In the antagonism, Zn2+ would increase cellular Zn amount through increasing the expression of ZIP8 and ZIP14 transporters to manage the ROS generation, but the zinc-based NPs would decrease expression of these transporters to decrease cellular Cd amount to help maintain the cell viability. Thus, we should hold a dialectical thinking about the pollution of NPs emissions in the environment.

A new peptide-based fluorescent probe for highly selective and sensitive detection of zinc (II) and application in real samples and cells imaging

Zinc (Zn2+) ions play a very important role in the environment and organisms, and it is of great significance to realize the high sensitivity and selectivity detection of Zn2+ ions. Herein, a new peptide-based fluorescent probe named DCH was rationally designed and synthesized by solid phase peptide synthesis with Fmoc chemistry. DCH exhibited excellent fluorescent “turn-on” responding to Zn2+ with highly selective and exhilaratingly sensitive in aqueous media, with detection limits (LOD) as low as 30.49 nM. ESI-MS, Job's plot curves and fluorescence titration results indicated that the stoichiometric ratio between DCH and Zn2+ was 2:1. DCH could be regenerated by adding EDTA solutions to the complex formed during interaction, and indicated that DCH was promising reversibility probe. Furthermore, DCH has excellent practical application potential through two actual water sample experiments. Importantly, DCH was successfully used in monitor cellular Zn2+ and EDTA in living HK2 cells and SV-HUC-1 cells based on good biocompatibility and exciting low toxicity.

The role of labile Zn2+ and Zn2+–transporters in the pathophysiology of mitochondria dysfunction in cardiomyocytes

An important energy supplier of cardiomyocytes is mitochondria, similar to other mammalian cells. Studies have demonstrated that any defect in the normal processes controlled by mitochondria can lead to abnormal ROS production, thereby high oxidative stress as well as lack of ATP. Taken into consideration, the relationship between mitochondrial dysfunction and overproduction of ROS as well as the relation between increased ROS and high-level release of intracellular labile Zn2+, those bring into consideration the importance of the events related with those stimuli in cardiomyocytes responsible from cellular Zn2+-homeostasis and responsible Zn2+-transporters associated with the Zn2+-homeostasis and Zn2+-signaling. Zn2+-signaling, controlled by cellular Zn2+-homeostatic mechanisms, is regulated with intracellular labile Zn2+ levels, which are controlled, especially, with the two Zn2+-transporter families; ZIPs and ZnTs. Our experimental studies in mammalian cardiomyocytes and human heart tissue showed that Zn2+-transporters localizes to mitochondria besides sarco(endo)plasmic reticulum and Golgi under physiological condition. The protein levels as well as functions of those transporters can re-distribute under pathological conditions, therefore, they can interplay among organelles in cardiomyocytes to adjust a proper intracellular labile Zn2+ level. In the present review, we aimed to summarize the already known Zn2+-transporters localize to mitochondria and function to stabilize not only the cellular Zn2+ level but also cellular oxidative stress status. In conclusion, one can propose that a detailed understanding of cellular Zn2+-homeostasis and Zn2+-signaling through mitochondria may emphasize the importance of new mitochondria-targeting agents for prevention and/or therapy of cardiovascular dysfunction in humans.

Whole-transcriptome sequencing (RNA-seq) study of the ZFL zebrafish liver cell line after acute exposure to Cd2+ ions

Cadmium (Cd) is a non-essential metal with no known biological function and a broad range of toxic effects in biological systems. We used whole-transcriptome sequencing (RNA-seq) to study the effects of Cd2+ toxicity in zebrafish liver cells, ZFL. The results of an RNA-Seq analysis of ZFL cells exposed to 5, 10 or 20 μM Cd2+ for 4- or 24-h. The differentially expressed genes affected by Cd2+ were analyzed by using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis to study the regulated pathways. Cd2+ regulated the expression of genes associated with cellular Cu, Zn, and Fe homeostasis, DNA replication leading to cell cycle arrest and apoptosis, and glutathione metabolism. Cd2+ boosted up the amino acid synthesis, possibly to support the glutathione metabolism for tackling the oxidative stress generated from Cd2+. Cd2+ stimulation was similar to heat or xenobiotics, based on the responses from ZFL such as endoplasmic reticulum stress and protein folding. We linked also those finding of gene activations relating to carcinogenesis of Cd. This paper provides a comprehensive analysis of the expression profiles induced by Cd2+ exposure in ZFL cells, as well as useful insights into the specific toxic effects.