Zinc transporters and their functional integration in mammalian cells

DNA aptamer targeting zinc transporters ZIP10 and ZIP6 on cancer cells

Cell-SELEX is an effective method for generating aptamers that specifically bind molecules in their native state on live cells. It not only uncovers novel potential biomarkers but also provides robust molecular recognition tools for a wide spectrum of applications. In this work, we generate a high affinity aptamer, HL15, through Cell-SELEX. A refined sequence HL15a demonstrated a strong binding affinity to target cells, with a minimal dissociation constant (Kd) of just 1.90 ± 0.49 nM. Subsequent truncation and mutation assays revealed that the core sequence of HL15a forms an antiparallel G-quadruplex structure. Furthermore, the target proteins of aptamer HL15a were identified and confirmed to be ZIP10 and ZIP6, both members of the zinc transporter ZIP family with high homology. Using HL15a as a molecular probe, we detected a range of universal binding affinities to the majority of tumor cells in the 48 cell lines evaluated. Furthermore, HL15a was effectively applied to distinguish high malignancy cancer tissues from both normal and low malignancy tissues in the pathological sections of breast and prostate cancers. Given that ZIP10 and ZIP6 play crucial roles in regulating zinc homeostasis and are implicated in numerous diseases, the aptamer HL15a offers a powerful tool for the study and potential therapeutic intervention of these two proteins.

The genetic interaction map of the human solute carrier superfamily

Solute carriers (SLCs), the largest superfamily of transporter proteins in humans with about 450 members, control the movement of molecules across membranes. A typical human cell expresses over 200 different SLCs, yet their collective influence on cell phenotypes is not well understood due to overlapping substrate specificities and expression patterns. To address this, we performed systematic pairwise gene double knockouts using CRISPR-Cas12a and -Cas9 in human colon carcinoma cells. A total of 1,088,605 guide combinations were used to interrogate 35,421 SLC-SLC and SLC-enzyme double knockout combinations across multiple growth conditions, uncovering 1236 genetic interactions with a growth phenotype. Further exploration of an interaction between the mitochondrial citrate/malate exchanger SLC25A1 and the zinc transporter SLC39A1 revealed an unexpected role for SLC39A1 in metabolic reprogramming and anti-apoptotic signaling. This full-scale genetic interaction map of human SLC transporters is the backbone for understanding the intricate functional network of SLCs in cellular systems and generates hypotheses for pharmacological target exploitation in cancer and other diseases. The results are available at https://re-solute.eu/resources/dashboards/genomics/ .

A small molecule modified UiO series MOFs for simultaneous detection of Fe3+ and Zn2

Iron and zinc are two metal ions with important roles in biology, industry and the environment, however, the excess or deficiency of both Fe3+ and Zn2+ can have negative effects on organisms and environment. Therefore, the development of efficient method for simultaneous detection of Fe3+ and Zn2+ provides timely information on metal content, simplifies operations and improves efficiency. In this work, a small molecule (COOH-BPEA) of recognizing Zn2+ modified the four metal-organic-framework (MOF) (UiO-66-X(66, OH, NH2 and OH/NH2)) was developed for the simultaneous detection of Fe3+ and Zn2+. The fluorescence signal of the small molecule is enhanced by small molecule chelating Zn2+ to block the photoinduced electron transfer (PET) effect. The fluorescence signals of the UiO series MOFs were quenched through Fe3+ with electron transfer and static quenching effect (SQE). It's worth mentioning that the emission wavelengths of the small molecules and MOFs did not interfere with each other. The UiO-66-NH2@BPEA with optimal performance was selected by fluorescence spectra for the detection of Fe3+ and Zn2+ with detection limit of 0.175 μM and 0.021 μM, respectively. The nanoprobe provides a fast response (less than 1 min) for both Fe3+ and Zn2+. Finally, we applied it to the simultaneous detection of Fe3+ and Zn2+ in environmental water, human serum and cell lysates.

Ion-Induced Dipole Interactions Matter in Metadynamics Simulation of Transition Metal Ion Transporters

Metal transporters play crucial roles in the homeostasis and detoxification of beneficial and toxic metals in the human body. Due to experimental limitations in studying some metal transporters, numerous simulation studies have been conducted to understand the mechanisms of metal transport. However, studying the transport of divalent metal ions across the plasma membrane by metal transporters has been challenging with traditional molecular dynamics (MD) simulations. The metal ions often become trapped inside the transporter due to encountering high energy barriers during the transport process. In this study, we combined a recently developed metadynamics setup, known as well-tempered (WT) volume-based MTD, with the 12-6-4 Lennard-Jones (LJ) model representing transition metal-His/Asp/Glu side chain interactions. We used this approach to investigate the mechanism of action of a Zrt-/Irt-like protein (ZIP) transporter and compared the results with simulations using standard 12-6 LJ parameters for the transition metal-His/Asp/Glu side chain interactions. Our results show that the 12-6-4 LJ model for transition metal-His/Asp/Glu side chain interactions samples conformational space more broadly than the standard 12-6 LJ model for the same interactions in MTD simulations, facilitating the sampling of states that are hard to reach with the standard 12-6 model within the same time scale. This is even more remarkable given the fact that the model is dominated by 12-6 LJ interactions for the majority of the system, while the transition metal-His/Asp/Glu side chain interactions are the only interactions using the 12-6-4 LJ model. Hence, a small subset of interactions significantly modifies the states sampled by the entire protein leading to a more frequent observation of the transport of the transition metal ion. Overall, using 12-6-4 LJ to model the transition metal-His/Asp/Glu side chain interactions increases the potential for discovering additional metastable states by enabling metal ions to traverse more freely along the defined transport pathways.

The TRPV3 channel is a mediator of zinc influx and homeostasis in murine oocytes

Zinc (Zn2+) homeostasis is essential for gametogenesis and reproduction, and its deficiency causes infertility. Oocytes contain higher Zn2+ levels than somatic cells, and Zn2+ concentrations in oocytes are far higher than those of other transition metals and increase even more during maturation in preparation for fertilization. Remarkably, it is unknown what transporter(s) or channel(s) mediate Zn2+ influx in oocytes and whether they are expressed uniformly throughout folliculogenesis. Here, we showed that the functional expression of a member of the transient receptor potential family, vanilloid 3, TRPV3, closely follows the dynamics of intracellular Zn2+ during oocyte maturation, raising the prospect that these events may be functionally linked. Using microfluorometry, we monitored in oocytes of Trpv3 null females the expected rise in Zn2+ concentrations during maturation. Surprisingly, Zn2+ levels did not climb, and the overall FluoZin3 signal in Trpv3 null eggs was lower than in control eggs. Electrophysiological recordings showed a large TRPV3 current induced by the agonist 2-APB in WT eggs supplemented with extracellular Zn2+ that was absent in Trpv3 null eggs; TRPV3 showed a clear preference for Zn2+ over Ca2+. Trpv3 null eggs displayed features associated with Zn2+ deficient conditions, such as lower IP3R1 function, abnormal cortical granule distribution, and disturbed cytoskeletal organization with distinct actin nucleation disorders. Notably, Trpv3 null eggs demonstrated undisturbed Zn2+ sparks. Our results suggest that TRPV3 is a pivotal member of the Zn2+ toolkit, mediating Zn2+ intake during maturation. They also indicate that distinct transporters or channels mediate Zn2+ influx throughout folliculogenesis.

Probing the substrate binding-induced conformational change of a ZIP metal transporter using a sandwich ELISA

Zrt-/Irt-like proteins (ZIPs), a family of divalent metal transporters, are crucial for maintaining the homeostasis of zinc, an essential trace element involved in numerous biological processes. While extensive research on the prototypical ZIP from Bordetella bronchiseptica (BbZIP) have suggested an elevator transport mechanism, the dynamic conformational changes during the transport cycle have not been thoroughly studied. In this work, we developed a sandwich ELISA using a custom anti-BbZIP monoclonal antibody to investigate the conformational change induced by the metal binding to the transport site. This was achieved by determining the accessibility of a cysteine residue introduced at a position exposed to the solvent only when the transporter adopts an outward-facing conformation. This assay allowed us to report the dissociation constants of BbZIP for Zn2+ and Cd2+ at low and sub-micromolar levels, respectively. Notably, the installation of a positive charge at the M2 site drastically reduced metal binding at the M1 site, consistent with an auxiliary role for the M2 site in metal transport. We also demonstrated that this assay can be used to rapidly screen variants for subsequent structural study. We anticipate that other transporters where substrate binding induces large conformational changes can also be studied using this method.

Responsive DNA artificial cells for contact and behavior regulation of mammalian cells

Artificial cells have emerged as synthetic entities designed to mimic the functionalities of natural cells, but their interactive ability with mammalian cells remains challenging. Herein, we develop a generalizable and modular strategy to engineer DNA-empowered stimulable artificial cells designated to regulate mammalian cells (STARM) via synthetic contact-dependent communication. Constructed through temperature-controlled DNA self-assembly involving liquid-liquid phase separation (LLPS), STARMs feature organized all-DNA cytoplasm-mimic and membrane-mimic compartments. These compartments can integrate functional nucleic acid (FNA) modules and light-responsive gold nanorods (AuNRs) to establish a programmable sense-and-respond mechanism to specific stimuli, such as light or ions, orchestrating diverse biological functions, including tissue formation and cellular signaling. By combining two designer STARMs into a dual-channel system, we achieve orthogonally regulated cellular signaling in multicellular communities. Ultimately, the in vivo therapeutic efficacy of STARM in light-guided muscle regeneration in living animals demonstrates the promising potential of smart artificial cells in regenerative medicine.

Quantification of lysosomal labile Zn2+ and monitoring of Zn2+ efflux using a small-molecule-protein hybrid fluorescent probe

Lysosomal labile Zn2+ levels have been unclear. By targeting a small-molecule fluorescent Zn2+ probe, ZnDA-3H, to lysosomes via VAMP7-Halo, the lysosomal labile Zn2+ concentration was determined to be 1.9 nM in HeLa cells. Furthermore, ZnDA-3H enabled direct visualization of the Zn2+ efflux from the lysosomes to cytosol upon TRPMLs activation.

Transcriptional responses of three slc39a/zip members (zip4, zip5 and zip9) and their roles in Zn metabolism in grass carp (Ctenopharyngodon idella)

In order to explore the regulatory mechanism of zip4, zip5 and zip9 in zinc metabolism of grass carp (Ctenopharyngodon idella), the effects of zinc (Zn) on the mRNA expression of zip4, zip5 and zip9 were investigated. Compared to the control, the mRNA levels of zip4 and zip9 were significantly reduced under low and high zinc in L8824 cells; the mRNA expression level of zip5 was significantly increased under low and high zinc incubation. Then, their promoter sequences were cloned, which were 2361 bp, 2004 bp and 2186 bp sequences for zip4, zip5 and zip9 promoters, respectively. The transcriptional activities of the three promoters had different responses to Zn treatment. The transcriptional factor signal transducer and activator of transcription 3 (STAT3) had specific binding sites at -1111/-1121 bp of zip5 promoter and at -1679/-1689 bp of zip9 promoter. Similarly, krüppel-like factor 4 (KLF4) could specifically bind to the -599/-609 bp sequence on the zip5 promoter and the -261/-272 bp sequence on the zip9 promoter. The results of electrophoretic mobility-shift assay (EMSA) and Chromatin immunoprecipitation (ChIP) indicated that Zn incubation increased DNA binding capacity of STAT3 to zip5 and zip9 promoters, and decreased DNA binding capacity of KLF4 to zip5 and zip9 promoters. This study provides a good basis for elucidating the regulatory mechanism of zinc metabolism in the vertebrates.

A dual absorption pathway of novel oyster-derived peptide-zinc complex enhances zinc bioavailability and restores mitochondrial function

Zinc deficiency is a global health issue that impairs immune function, growth, and energy metabolism. Although conventional zinc supplements have been developed, their effectiveness is limited by poor bioavailability and susceptibility to dietary inhibitors. In this study, a peptide-zinc complex (IE-Zn) derived from oysters was developed to enhance zinc uptake and address metabolic disruptions caused by deficiency. It was determined that Zn2+ binds with high affinity to the IE peptide, promoting structural flexibility that facilitates zinc transport through both zinc ion transporters and oligopeptide transporters. In Caco-2 and IEC-6 cell models, IE-Zn was shown to significantly improve zinc absorption and retention compared to ZnSO4, driven by the upregulation of ZIP4 and PEPT1 transporters. In vivo studies in a zinc-deficient mouse model confirmed enhanced zinc absorption and distribution across serum, intestine, and liver. Moreover, IE-Zn restored energy homeostasis by activating the AMPK/PGC1-α/NRF-1/TFAM signaling pathway, promoting mitochondrial biogenesis and reducing oxidative stress. These findings suggest that IE-Zn is a superior zinc supplement with higher bioavailability and serves as a potent regulator of cellular energy metabolism, offering therapeutic potential for managing conditions related to zinc deficiency and mitochondrial dysfunction. This study lays the foundation for further exploration of peptide-mineral complexes as advanced nutritional supplements with broad applications. Subsequent studies will further investigate the absorption pathway and targeting of peptide-zinc complex. The hope is to provide potential preventive applications for people in need, including zinc deficiency and a range of diseases caused by zinc deficiency.

Transcriptome-wide association study identifies genes associated with bladder cancer risk

Genome-wide association studies (GWAS) have detected several susceptibility variants for urinary bladder cancer, but how gene regulation affects disease development remains unclear. To extend GWAS findings, we conducted a transcriptome-wide association study (TWAS) using PrediXcan to predict gene expression levels in whole blood using genome-wide genotype data for 6180 bladder cancer cases and 5699 controls included in the database of Genotypes and Phenotypes (dbGaP). Logistic regression was used to estimate adjusted gene-level odds ratios (OR) per 1-standard deviation higher expression with 95% confidence intervals (CI) for bladder cancer risk. We further assessed associations for individual single-nucleotide polymorphisms (SNPs) used to predict expression levels and proximal loci for genes identified in gene-level analyses with false-discovery rate (FDR) correction. TWAS identified four genes for which expression levels were associated with bladder cancer risk: SLC39A3 (OR = 0.91, CI = 0.87-0.95, FDR = 0.015), ZNF737 (OR = 0.91, CI = 0.88-0.95, FDR = 0.016), FAM53A (OR = 1.09, CI = 1.05-1.14, FDR = 0.022), and PPP1R2 (OR = 1.09, CI = 1.05-1.13, FDR = 0.049). Findings from this TWAS enhance our understanding of how genetically-regulated gene expression affects bladder cancer development and point to potential prevention and treatment targets.

Severe neonatal hypotonia due to SLC30A5 variant affecting function of ZnT5 zinc transporter

The tightly-regulated spatial and temporal distribution of zinc ion concentrations within cellular compartments is controlled by two groups of Zn2+ transporters: the 14-member ZIP/SLC39 family, facilitating Zn2+ influx into the cytoplasm from the extracellular space or intracellular organelles; and the 10-member ZnT/SLC30 family, mobilizing Zn2+ in the opposite direction. Genetic aberrations in most zinc transporters cause human syndromes. Notably, previous studies demonstrated osteopenia and male-specific cardiac death in mice lacking the ZnT5/SLC30A5 zinc transporter, and suggested association of two homozygous frameshift SLC30A5 variants with perinatal mortality in humans, due to hydrops fetalis and hypertrophic cardiomyopathy. We set out to decipher the molecular basis of a severe hypotonia syndrome. Combining homozygosity mapping and exome sequencing studies of consanguineous Bedouin kindred, as well as transfection experiments and zinc monitoring in HEK293 cells, we demonstrate that a bi-allelic in-frame 3bp deletion variant in SLC30A5, deleting isoleucine within the highly conserved cation efflux domain of the encoded ZnT5, results in lower cytosolic zinc concentrations, causing a syndrome of severe non-progressive neonatal axial and limb hypotonia with high-arched palate and respiratory failure. There was no evidence of hydrops fetalis, cardiomyopathy or multi-organ involvement. Affected infants required nasogastric tube or gastrostomy feeding, suffered from various degrees of respiratory compromise and failure to thrive and died in infancy. Thus, a biallelic variant in SLC30A5 (ZnT5), affecting cytosolic zinc concentrations, causes a severe hypotonia syndrome with respiratory insufficiency and failure to thrive, lethal by 1 year of age.

Moonlighting Proteins of Human and Some Other Eukaryotes. Evolutionary Aspects

This review presents materials on formation of the concept of moonlighting proteins and general characteristics of different similar proteins. It is noted that the concept under consideration is based on the data on the existence in different organisms of individual genes, protein products of which have not one, but at least two fundamentally different functions, for example, depending on cellular or extracellular location. An important feature of these proteins is that their functions can be switched. As a result, in different cellular compartments or outside the cells, as well as under a number of other circumstances, one of the possible functions can be carried out, and under other conditions, another. It is emphasized that the significant interest in moonlighting proteins is due to the fact that information is currently accumulating about their involvement in many vital molecular processes (glycolysis, translation, transcription, replication, etc.). Alternative hypotheses on the evolutionary origin of moonlighting proteins are discussed.

Zinc and its binding proteins: essential roles and therapeutic potential

Zinc is an essential micronutrient that participates in a multitude of cellular and biochemical processes. It is indispensable for normal growth and the maintenance of physiological functions. As one of the most significant trace elements in the body, zinc fulfills three primary biological roles: catalytic, structural, and regulatory. It serves as a cofactor in over 300 enzymes, and more than 3000 proteins require zinc, underscoring its crucial role in numerous physiological processes such as cell division and growth, immune function, tissue maintenance, as well as synthesis protein and collagen synthesis. Zinc deficiency has been linked to increased oxidative stress and inflammation, which may contribute to the pathogenesis of a multitude of diseases, like neurological disorders and cancer. In addition, zinc is a key constituent of zinc-binding proteins, which play a pivotal role in maintaining cellular zinc homeostasis. This review aims to update and expand upon the understanding of zinc biology, highlighting the fundamental roles of zinc in biological processes and the health implications of zinc deficiency. This work also explores the diverse functions of zinc in immune regulation, cellular growth, and neurological health, emphasizing the need for further research to fully elucidate the therapeutic potential of zinc supplementation in disease prevention and management.

Cryo-EM structures of the zinc transporters ZnT3 and ZnT4 provide insights into their transport mechanisms

Zinc transporters (ZnTs) act as H+/Zn2+ antiporters, crucial for zinc homeostasis. Brain-specific ZnT3 expressed in synaptic vesicles transports Zn2+ from the cytosol into vesicles and is essential for neurotransmission, with ZnT3 dysfunction associated with neurological disorders. Ubiquitously expressed ZnT4 localized to lysosomes facilitates the Zn2+ efflux from the cytosol to lysosomes, mitigating the cell injury risk. Despite their importance, the structures and Zn2+ transport mechanisms remain unclear. We characterized the three-dimensional structures of human ZnT3 (inward-facing) and ZnT4 (outward-facing) using cryo-electron microscopy. By combining these structures, we assessed the conformational changes that could occur within the transmembrane domain during Zn2+ transport. Our results provide a structural basis for a more comprehensive understanding of the H+/Zn2+ exchange mechanisms exhibited by ZnTs.

BPA Exacerbates Zinc Deficiency-Induced Testicular Tissue Inflammation in Male Mice Through the TNF-α/NF-κB/Caspase8 Signaling Pathway

Bisphenol A (BPA) is an endocrine-disrupting chemical that is toxic to reproduction. Zinc (Zn) plays an important role in male reproductive health. Zn deficiency (ZD) can co-exist with BPA. In order to investigate the specific mechanism of reproductive damage caused by BPA exposure in ZD male mice, a mouse model of ZD, BPA exposure, and their combined exposure was established in this study. Forty 4-week-old SPF male ICR mice with an average body weight of 31.7 ± 4.2 g were divided into four groups including normal Zn diet group 30 mg/(kg•d), BPA exposure group 150 mg/(kg•d), zinc deficiency diet group 7.5 mg/(kg•d), and BPA + ZD combined exposure group (BPA 150 mg/(kg•d) + ZD 7.5 mg/(kg•d)). The mice were kept for 8 weeks. The results showed that the testicular tissue structure was disturbed, and semen quality, serum Zn, testicular tissue Zn, and testicular tissue free Zn ions were decreased in the BPA-exposed and ZD groups. The expression of zinc transporters (ZIP7, ZIP8, ZIP13, and ZIP14) in testicular tissue was changed. The expressions of pro-inflammatory cytokines including TNF-α and IL-1β as well as inflammatory pathway-related proteins (IKB-α, p-IKB-α, NF-κB, p-NF-κB, Caspase8, and Caspase3) were increased, while the expressions of anti-inflammatory cytokines (TGF-β and IL-10) were decreased. The changes in the above indexes in the BPA + ZD group were more obvious. Both BPA exposure and ZD can induce testicular tissue inflammation through the TNF-α/NF-κB/Caspase8 signaling pathway, and BPA further aggravates zinc deficiency-induced testicular tissue inflammation and apoptosis damage.

Biochemical Markers of Zinc Nutrition

Zinc is an important trace element involved in the biochemical and physiological functions of the organism and is essential in the human body. It has been reported that 17.3% of people around the world are at risk of many diseases due to zinc deficiency, which has already affected people's healthy lives. Currently, mild zinc deficiency is difficult to diagnose early due to the lack of typical clinical manifestations, so finding zinc biomarkers is crucial for people's health. The present article reviews the main representative zinc biomarkers, such as body fluid zinc levels, zinc-dependent proteins, tissue zinc, and zinc-containing enzymes, to provide a reference for actively promoting the study of zinc nutritional status and early clinical diagnosis.

Distinctive expression and cellular localisation of zinc homeostasis-related proteins in breast and prostate cancer cells

BACKGROUND

Zinc transport proteins (ZIP and ZnT), metallothioneins (MT) and protein kinase CK2 are involved in dysregulation of zinc homeostasis in breast and prostate cancer cells. Following up our previous research, we targeted ZIP12, ZnT1, MT2A and CK2 in this study by investigating their expression levels and protein localisation.

METHODS

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence confocal microscopy were employed to quantify the expression of ZIP12, ZnT1, MT2A and CK2 subunits in a panel of breast and prostate cell lines without or with extracellular zinc exposure. The cellular localisations of these target proteins were also examined by immunofluorescence confocal microscopy.

RESULTS

In response to the extracellular zinc exposure, the gene expression was elevated for SLC39A12 (ZIP12), SLC30A1 (ZnT1) and MT2A (MT2A) in normal prostate epithelial cells (RWPE-1) in contrast to their cancerous counterparts (PC3 and DU145), whilst the gene expression was higher for SLC39A12 (ZIP12) and SLC30A1 (ZnT1) in both normal (MCF10A) and basal breast cancer cells (MDA-MB-231) compared to luminal breast cancer cells (MCF-7). At the protein level, the expression for both ZIP12 and ZnT1 was trending lower in the time course for the breast cancer cells whilst their expression was remained constant in the normal breast epithelial cells. The expression of ZIP12 in prostate cancer cells was higher than the normal prostate cells. The protein expression for CK2 α/αꞌ and CK2β was markedly higher in prostate cancer cells than the normal prostate cells. Upon extracellular zinc exposure, ZIP12 was, for the first time, conspicuously localised in the plasma membrane of breast cancer cells but not in normal breast epithelial cells and prostate cells. ZnT1 is only localised in the plasma membrane of breast cancer cells. MT2A is distinctively seen close to the plasma membrane in breast cancer cells. CK2 is also for the first time shown to be localised in proximity to the plasma membrane of breast cancer cells.

CONCLUSION

The findings, particularly the localisation of ZIP12 and CK2, are novel and significant for our understanding of zinc homeostasis in breast and prostate cancer cells.

Zinc as a Mediator Through the ROCK1 Pathway of Cognitive Impairment in Aluminum-Exposed Workers: A Clinical and Animal Study

Aluminum (Al) exposure was implicated in neurodegenerative diseases and cognitive impairment, yet the involvement of zinc (Zn) and its mechanism in Al-induced mild cognitive impairment (MCI) remains poorly understood. The objective is to explore the role of Zn in Al-induced cognitive impairment and its potential mechanisms. Montreal cognitive assessment (MoCA) test scores and serum Al, Zn from Al industry workers were collected. A mediation analysis was performed to evaluate the role of serum Zn among serum Al and MoCA test scores. Subsequently, an Al-exposure study was conducted on a rat model categorized into control, low-, medium-, and high-dose groups. After a Morris Water Maze test and detection of Al, Zn content in the hippocampus, integrated transcriptomic and proteomic analyses between the control group and the high-dose group were performed to identify the differentially expressed genes (DEPs), proteins (DEPs), and pathways. To corroborate these findings, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB) were selected to identify the gene and protein results. Zn overall mediates the relationship between serum Al and cognitive function (mediation effect 17.82%, effect value =  - 0.0351). In the Al-exposed rat model, 734 DEGs, 18 miRNAs, 35 lncRNAs, 64 circRNAs, and 113 DEPs were identified between the high-dose group and the control group. Among them, ROCK1, DMD, and other four DEPs were identified as related to zinc finger proteins (ZNF). Co-enrichment analyses of the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) linked these changes to the RHOA/ROCK1 signaling axis. ZNF-related proteins Rock1, DMD, and DHX57 in the high-dose group were downregulated (p = 0.006, 0.003, 0.04), and the expression of Myl9, Rhoa, miR431, and miR182 was also downregulated (p = 0.003, 0.032, 0.032, and 0.046). These findings also show correlations between Al, Zn levels in the hippocampus, water maze performance, and expressions of Myl9, Rhoa, miR431, miR182, DMD, ROCK1, and DHX57, with both negative and positive associations. Based on the results, we determined that Zn was involved in Al-induced MCI in Al workers and Al-exposed rat models. Al exposure and interaction with Zn could trigger the downregulation of ZNF of ROCK1, DMD, and DHX57. miR431, miR182 regulate RHOA/ROCK1 was one of the Zn-involved pathways in Al-induced cognitive impairment.

Elements in trace amount with a significant role in human physiology: a tumor pathophysiological and diagnostic aspects

Cancer has a devastating impact globally regardless of gender, age, and community, which continues its severity to the population due to the lack of efficient strategy for the cancer diagnosis and treatment. According to the World Health Organisation report, one out of six people dies due to this deadly cancer and we need effective strategies to regulate it. In this context, trace element has a very hidden and unexplored role and require more attention from investigators. The variation in concentration of trace elements was observed during comparative studies on a cancer patient and a healthy person making them an effective target for cancer regulation. The percentage of trace elements present in the human body depends on environmental exposure, food habits, and habitats and could be instrumental in the early diagnosis of cancer. In this review, we have conducted inclusive analytics on trace elements associated with the various types of cancers and explored the several methods involved in their analysis. Further, intricacies in the correlation of trace elements with prominent cancers like prostate cancer, breast cancer, and leukaemia are represented in this review. This comprehensive information on trace elements proposes their role during cancer and as biomarkers in cancer diagnosis.

Molecular insights into substrate translocation in an elevator-type metal transporter

The Zrt/Irt-like protein (ZIP) metal transporters are key players in maintaining the homeostasis of a panel of essential microelements. The prototypical ZIP from Bordetella bronchiseptica (BbZIP) is an elevator transporter, but how the metal substrate moves along the transport pathway and how the transporter changes conformation to allow alternating access remain to be elucidated. Here, we combine structural, biochemical, and computational approaches to investigate the process of metal substrate translocation along with the global structural rearrangement. Our study reveals an upward hinge motion of the transport domain in a high-resolution crystal structure of a cross-linked variant, elucidates the mechanisms of metal release from the transport site into the cytoplasm and activity regulation by a cytoplasmic metal-binding loop, and unravels an unusual elevator mode in enhanced sampling simulations that distinguishes BbZIP from other elevator transporters. This work provides important insights into the metal transport mechanism of the ZIP family.

Effects of Dietary Zinc Deficiency and Supplementation on Prepubertal Rat Testes: Sulfhydryl and Antioxidant Status

The study was designed to investigate the effects of dietary zinc deficiency and supplementation on antioxidant system viz. superoxide-dismutase, glutathione reductase, glutathione peroxidase, glutathione- S-transferase, catalase and sulfhydryls levels (GSH, TSH, NPSH and PBSH) in testes of Wistar rats. Pre-pubertal rats were divided into two groups with 6 sub-groups each viz. zinc control (ZC), pair fed (PF), zinc deficient (ZD), zinc control supplementation (ZCS), pair-fed supplementation (PFS) and zinc deficient supplementation (ZDS). Experiments were set for 2- and 4-weeks followed by 4 weeks of zinc supplementation. The zinc deficient group animals exhibited significant decrease in gonado-somatic index (2- and 4- weeks), sulfhydryls levels, GSH, GPx, GR (2 and 4-weeks) and GST concentration (2-weeks). However, after zinc supplementation significant improvement in gonadosomatic index, SH, GSH, antioxidant enzyme levels (GR, GPx, and GST) in deficient groups has been observed. Zinc deficiency during pre-pubertal period affected growth and caused dysregulation of the glutathione antioxidant system. The significant alterations in the levels of antioxidant enzymes and non-enzymatic antioxidant system (GSH and SH) in zinc deficient groups could be due to alleviated generation of free radicals, causative factor for increased oxidative stress which may lead to infertility as oxidative stress is a common pathology seen during infertility. Altered antioxidant system and sulfhydryls levels in testes due to dietary zinc deficiency reflect the significance of optimum zinc for maintaining homeostatic balance in gonadal physiology. Supplementing zinc for 4 weeks could reduce the redox imbalance which may help in alleviating oxidative stress induced alterations in testes.

On the genesis and unique functions of zinc neuromodulation

In addition to the essential structural and catalytic functions of zinc, evolution has adopted synaptic zinc as a neuromodulator. In the brain, synaptic zinc is released primarily from glutamatergic neurons, notably in the neocortex, hippocampus, amygdala, and auditory brainstem. In these brain areas, synaptic zinc is essential for neuronal and sensory processing fine-tuning. But what niche does zinc fill in neural signaling that other neuromodulators do not? Here, we discuss the evolutionary history of zinc as a signaling agent and its eventual adoption as an essential neuromodulator in the mammalian brain. We then attempt to describe the unique roles that zinc has carved out of the vast and diverse landscape of neuromodulators.

Upregulation of Intracellular Zinc Ion Level after Differentiation of the Neural Stem/Progenitor Cells In Vitro with the Changes in Gene Expression of Zinc Transporters

We measured the intracellular zinc ion concentration of murine fetal neural stem/progenitor cells (NSPCs) and that in the differentiated cells. The NSPCs cultured with 1.5 μM Zn2+ proliferated slightly faster than that in the zinc-deficient medium and the intracellular zinc concentration of the NSPCs and that of their differentiated cells (DCs) cultured with 1.5 μM Zn2+ was 1.34-fold and 2.00-fold higher than those in the zinc-deficient medium, respectively. The zinc transporter genes upregulated over the 3.5-fold change were Zip1, Zip4, Zip12, Zip13, ZnT1, ZnT8, and ZnT10 whereas the only downregulated one was Zip8 during the differentiation of NSPCs to DCs. The cell morphologies of both NSPCs and DCs in the low oxygen culture condition consisting of 2%O2 and 5%CO2, the high carbon dioxide condition consisting of 21%O2 and 10%CO2, and the normal condition consisting of 21%O2 and 5%CO2 were essentially the same each other. The expression of Zip4, Zip8, Zip12, and Zip14 was not drastically changed depending on the O2 and CO2 concentrations.

Zinc-glutathione mitigates alcohol-induced intestinal and hepatic injury by modulating intestinal zinc-transporters in mice

Long-term alcohol overconsumption impairs intestinal and hepatic structure and function, along with dysregulation of zinc homeostasis. We previously found that zinc-glutathione (Zn-GSH) complex effectively suppressed alcohol-induced liver injury in mice. This study was undertaken to test the hypothesis that Zn-GSH suppresses alcohol-induced liver injury by modulating intestinal zinc transporters. Mice were subjected to long-term ethanol feeding, as per the NIAAA model, with groups receiving either an ethanol diet alone or an ethanol diet supplemented with Zn-GSH. Treatment groups were carefully monitored for alcohol consumption and subjected to a final binge drinking exposure. The results showed that Zn-GSH increased the survival rate and decreased the recovery time from binge drinking-induced drunkenness. Histopathological analyses demonstrated a reduction in liver steatosis and the preservation of intestinal integrity by Zn-GSH. It was observed that Zn-GSH prevented the reduction of Zn and GSH levels while increasing alcohol dehydrogenase and aldehyde dehydrogenase in both liver and intestine. Importantly, the expression and protein abundance of zinc transporters ZnT-1, ZIP-1, ZIP-4, ZIP-6, and ZIP-14, all of which are critically involved in intestinal zinc transport and homeostasis, were significantly increased or preserved by Zn-GSH in response to alcohol exposure. This study thus highlights the critical role of Zn-GSH in maintaining intestinal zinc homeostasis by modulating zinc transporters, thereby preventing alcohol-induced intestinal and hepatic injury.

Evolution, classification, and mechanisms of transport, activity regulation, and substrate specificity of ZIP metal transporters

The Zrt/Irt-like protein (ZIP) family consists of ubiquitously expressed divalent d-block metal transporters that play central roles in the uptake, secretion, excretion, and distribution of several essential and toxic metals in living organisms. The past few years has witnessed rapid progress in the molecular basis of these membrane transport proteins. In this critical review, we summarize the research progress at the molecular level of the ZIP family and discuss the future prospects. Furthermore, an evolutionary path for the unique ZIP fold and a new classification of the ZIP family are proposed based on the presented structural and sequence analyses.

Molecular insights into substrate translocation in an elevator-type metal transporter

The Zrt/Irt-like protein (ZIP) metal transporters are key players in maintaining the homeostasis of a panel of essential microelements. The prototypical ZIP from Bordetella bronchiseptica (BbZIP) is an elevator transporter, but how the metal substrate moves along the transport pathway and how the transporter changes conformation to allow alternating access remain to be elucidated. Here, we combined structural, biochemical, and computational approaches to investigate the process of metal substrate translocation along with the global structural rearrangement. Our study revealed an upward hinge motion of the transport domain in a high-resolution crystal structure of a cross-linked variant, elucidated the mechanisms of metal release from the transport site into the cytoplasm and activity regulation by a cytoplasmic metal-binding loop, and unraveled an unusual elevator mode in enhanced sampling simulations that distinguishes BbZIP from other elevator transporters. This work provides important insights into the metal transport mechanism of the ZIP family.

The role of zinc and matrix metalloproteinases in myofibrillar protein degradation in critical illness myopathy

Due to an unexpected activation of different zinc (Zn) transporters in a recent prospective clinical study, we have revisited the role of Zn homeostasis and the activation of matrix metalloproteinases (MMPs) in skeletal muscle exposed to the intensive care unit (ICU) condition (immobilization and mechanical ventilation). ICU patients exposed to 12 days ICU condition were followed longitudinally with six repeated muscle biopsies while they showed a progressive preferential myosin loss, i.e., the hallmark of Critical Illness Myopathy (CIM), in parallel with the activation of Zn-transporters. In this study, we have revisited the expression of Zn-transporters and the activation of MMPs in clinical as well as in experimental studies using an established ICU model. MMPs are a group Zn-dependent endopeptidases which do not only target and cleave extracellular proteins but also intracellular proteins including multiple sarcomeric proteins. MMP-9 is of specific interest since the hallmark of CIM, the preferential myosin loss, has also been reported in dilated cardiomyopathy and coupled to MMP-9 activation. Transcriptional activation of Zn-transporters was observed in both clinical and experimental studies as well as the activation of MMPs, in particular MMP-9, in various limb and respiratory muscles in response to long-term exposure to the ICU condition. The activation of Zn-transporters was paralleled by increased Zn levels in skeletal muscle which in turn showed a negative linear correlation with the preferential myosin loss associated with CIM, offering a potential intervention strategy. Thus, activation of Zn-transporters, increased intramuscular Zn levels, and activation of the Zn-dependent MMPs are forwarded as a probable mechanism involved in CIM pathophysiology. These effects were confirmed in different rat strains subjected to a model of CIM and exacerbated by old age. This is of specific interest since old age and muscle wasting are the two factors most strongly associated with ICU mortality.

Zn2+ chelating peptide GFLGSP: Characterization of structure/Zn2+ chelating mode and the potential mechanisms for promoting Zn2+ transport in Caco-2 cells

This study focused on exploring the Zn2+ chelating peptide GFLGSP: the characterization of structure/Zn2+ chelating mode and the potential mechanisms for promoting Zn2+ transport in Caco-2 cells. The findings revealed the bidentate chelating between Zn2+ and carboxyl oxygen atom in Pro6 residue. Thereafter, the secondary structure of GFLGSP remained unchanged, but there was an increase in zeta potential and particle size. Notably, the GFLGSP-Zn2+ complex enhanced the Zn2+ transport rate and modulated ZIP4 and ZNT1 expression in a Caco-2 cells monolayer model. As revealed by molecular docking analysis, GFLGSP interacted with ZIP4 through intermolecular hydrogen bonds as well as Van der Waals forces. The Zn2+ transport mechanisms of the GFLGSP-Zn2+ complex encompassed ZIP4 (vital channel), endocytosis (primary pathway) and paracellular transport (supplementary pathway). Based on these results, the tilapia skin collagen-derived GFLGSP hold promise as the potential dietary Zn2+ supplement.

Determination of metal ion transport rate of human ZIP4 using stable zinc isotopes

The essential microelement zinc is absorbed in the small intestine mainly by the zinc transporter ZIP4, a representative member of the Zrt/Irt-like protein (ZIP) family. ZIP4 is reportedly upregulated in many cancers, making it a promising oncology drug target. To date, there have been no reports on the turnover number of ZIP4, which is a crucial missing piece of information needed to better understand the transport mechanism. In this work, we used a nonradioactive zinc isotope, 70Zn, and inductively coupled plasma mass spectrometry to study human ZIP4 (hZIP4) expressed in Human embryonic kidney 293 cells. Our data showed that 70Zn can replace the radioactive 65Zn as a tracer in kinetic evaluation of hZIP4 activity. This approach, combined with the quantification of the cell surface expression of hZIP4 using biotinylation or surface-bound antibody, allowed us to estimate the apparent turnover number of hZIP4 to be in the range of 0.08 to 0.2 s-1. The turnover numbers of the truncated hZIP4 variants are significantly smaller than that of the full-length hZIP4, confirming a crucial role for the extracellular domain in zinc transport. Using 64Zn and 70Zn, we measured zinc efflux during the cell-based transport assay and found that it has little effect on the zinc import analysis under these conditions. Finally, we demonstrated that use of laser ablation inductively coupled plasma-TOF-mass spectrometry on samples applied to a solid substrate significantly increased the throughput of the transport assay. We envision that the approach reported here can be applied to the studies of metal transporters beyond the ZIP family.

Localization of the MTP4 transporter to trans-Golgi network in pollen tubes of Arabidopsis thaliana

Zinc (Zn) is an essential element for plants. Numerous proteins in different cellular compartments require Zn for their structure and function. Zn can be toxic when it accumulates in high levels in the cytoplasm. Therefore, Zn homeostasis at tissue, cell, and organelle levels is vital for plant growth. A part of the metal tolerance protein (MTP) / Cation Diffusion Facilitator (CDF) transporters functions as Zn transporters, exporting Zn from the cytosol to various membrane compartments. In Arabidopsis thaliana, MTP1, MTP2, MTP3, MTP4, MTP5, and MTP12 are classified as Zn transporters (Zn-CDF). In this study, we systematically analyzed the localization of GFP-fused Zn-CDFs in the leaf epidermal cells of Nicotiana benthamiana. As previously reported, MTP1 and MTP3 were localized to tonoplast, MTP2 to endoplasmic reticulum, and MTP5 to Golgi. In addition, we identified the localization of MTP4 to trans-Golgi Network (TGN). Since MTP4 is specifically expressed in pollen, we analyzed the localization of MTP4-GFP in the Arabidopsis pollen tubes and confirmed that it is in the TGN. We also showed the Zn transport capability of MTP4 in yeast cells. We then analyzed the phenotype of an mtp4 T-DNA insertion mutant under both limited and excess Zn conditions. We found that their growth and fertility were not largely different from the wild-type. Our study has paved the way for investigating the possible roles of MTP4 in metallating proteins in the secretory pathway or in exporting excess Zn through exocytosis. In addition, our system of GFP-fused MTPs will help study the mechanisms for targeting transporters to specific membrane compartments.

Zinc transporters expression profile in professional handball players supplemented with zinc

INTRODUCTION

Zinc (Zn) deficiency has been described not only on general human health but also within the sports context -as negatively affecting performance-. Thus, Zn status assessment is of great interest for athletes, especially in order to correct deficiency states of this mineral.

OBJECTIVE

The overall objective of this work was to assess Zn status in professional handball players during the competitive period (through plasma levels, dietary intake and gene expression of the Zn transporters), as well as to determine the effect of Zn supplementation.

METHODS

A total of twenty-two participants were recruited, -twelve belonged to the Control Group (CG) and ten male handball players comprised the experimental group (ATH-G)-, being monitored over a 2-month period with 2 evaluation moments: baseline (i.e., initial conditions) and follow-up (i.e., after 8 weeks of training and competition). Zn intake, plasma Zn levels, and gene expression of Zn transporters were obtained.

RESULTS

Plasma Zn levels were higher in ATH-G than in CG at the end of Zn intervention (p ≤ 0.010). Moreover, differences in the gene expression profile of Zn transporters were observed in ATH-G -with the down-regulation of several Zn transporters-, compared to the CG at baseline (p ≤ 0.05). Likewise, differences in the Zn transporters expression were observed in ATH-G at 8 weeks (all, p ≤ 0.001) -with ZnT2, ZnT5, ZIP3, ZIP5, ZIP11, ZIP13 and ZIP14 transporters being up-regulated-.

CONCLUSION

Handball players seemed to have different nutritional needs for Zn, with differences in the gene expression of Zn transporters compared to controls. Zn intervention in our athletes may have influenced the expression of Zn transporters, indicating a potential increase in Zn transporters expression to mobilize Zn at the cellular level at 8 weeks of Zn intervention.

Reduced Mn uptake of pleiotropic ZIP8 SNP is caused by its loss of Mn-responsive accumulation on the cell-surface

Zrt/Irt-like protein 8 (ZIP8), which is a Zn transporter, plays a pivotal role as a Mn transporter. Recent studies have shown that a ZIP8 SNP (rs13107325 C→T, A391T) is associated with multiple diseases, likely by causing systemic Mn deficiency. However, the underlying molecular mechanisms remain unclear. We attempted to address this issue in cell-based experiments using Madin-Darby canine kidney cells stably expressing ZIP8 WT or the A391T SNP mutant under the control of the Tet-regulatable promoter. We showed that the A391T mutant lost the property of Mn-responsive accumulation on the cell surface, which was observed in WT ZIP8. We also showed that the loss of Mn-responsive accumulation of A391T mutant was associated with its reduced Mn uptake, compared with WT ZIP8, in the Mn uptake assay using the radioisotope 54Mn. Our results potentially explain how the ZIP8 A391T substitution is associated with disease pathogenesis caused by Mn deficiency.

Cadmium exposure elicited dynamic RNA m6A modification and epi-transcriptomic regulation in the Pacific whiteleg shrimp Litopenaeus vannamei

N6-methyladenosine (m6A) methylation is the most prevalent post-transcriptional RNA modification in eukaryotic organisms, but its roles in the regulation of physiological resistance of marine crustaceans to heavy metal pollutants are poorly understood. In this study, the transcriptome-wide m6A RNA methylation profiles and dynamic m6A changes induced by acute Cd2+ exposure in the the pacific whiteleg shrimp Litopenaeus vannamei were comprehensively analyzed. Cd2+ toxicity caused a significant reduction in global RNA m6A methylation level, with major m6A regulators including the m6A methyltransferase METTL3 and the m6A binding protein YTHDF2 showing declined expression. Totally, 11,467 m6A methylation peaks from 6415 genes and 17,291 peaks within 7855 genes were identified from the Cd2+ exposure group and the control group, respectively. These m6A peaks were predominantly enriched in the 3' untranslated region (UTR) and around the start codon region of the transcripts. 7132 differentially expressed genes (DEGs) and 7382 differentially m6A-methylated genes (DMGs) were identified. 3186 genes showed significant changes in both gene expression and m6A methylation levels upon cadmium exposure, and they were related to a variety of biological processes and gene pathways. Notably, an array of genes associated with antioxidation homeostasis, transmembrane transporter activity and intracellular detoxification processes were significantly enriched, demonstrating that m6A modification may mediate the physiological responses of shrimp to cadmium toxicity via regulating ROS balance, Cd2+ transport and toxicity mitigation. The study would contribute to a deeper understanding of the evolutionary and functional significance of m6A methylation to the physiological resilience of decapod crustaceans to heavy metal toxicants.

Coordination chemistry suggests that independently observed benefits of metformin and Zn2+ against COVID-19 are not independent

Independent trials indicate that either oral Zn2+ or metformin can separately improve COVID-19 outcomes by approximately 40%. Coordination chemistry predicts a mechanistic relationship and therapeutic synergy. Zn2+ deficit is a known risk factor for both COVID-19 and non-infectious inflammation. Most dietary Zn2+ is not absorbed. Metformin is a naked ligand that presumably increases intestinal Zn2+ bioavailability and active absorption by cation transporters known to transport metformin. Intracellular Zn2+ provides a natural buffer of many protease reactions; the variable "set point" is determined by Zn2+ regulation or availability. A Zn2+-interactive protease network is suggested here. The two viral cysteine proteases are therapeutic targets against COVID-19. Viral and many host proteases are submaximally inhibited by exchangeable cell Zn2+. Inhibition of cysteine proteases can improve COVID-19 outcomes and non-infectious inflammation. Metformin reportedly enhances the natural moderating effect of Zn2+ on bioassayed proteome degradation. Firstly, the dissociable metformin-Zn2+ complex could be actively transported by intestinal cation transporters; thereby creating artificial pathways of absorption and increased body Zn2+ content. Secondly, metformin Zn2+ coordination can create a non-natural protease inhibitor independent of cell Zn2+ content. Moderation of peptidolytic reactions by either or both mechanisms could slow (a) viral multiplication (b) viral invasion and (c) the pathogenic host inflammatory response. These combined actions could allow development of acquired immunity to clear the infection before life-threatening inflammation. Nirmatrelvir (Paxlovid®) opposes COVID-19 by selective inhibition the viral main protease by a Zn2+-independent mechanism. Pending safety evaluation, predictable synergistic benefits of metformin and Zn2+, and perhaps metformin/Zn2+/Paxlovid® co-administration should be investigated.

An Overexpression of SLC30A6 Gene Contributes to Cardiomyocyte Dysfunction via Affecting Mitochondria and Inducing Activations in K-Acetylation and Epigenetic Proteins

Intracellular free Zn2+ ([Zn2+]i) is less than 1-nM in cardiomyocytes and its regulation is performed with Zn2+-transporters. However, the roles of Zn2+-transporters in cardiomyocytes are not defined exactly yet. Here, we aimed to examine the role of an overexpression and subcellular localization of a ZnT6 in insulin-resistance mimic H9c2 cardiomyoblasts (IR-cells; 50-μM palmitic acid for 24-h incubation). We used both IR-cells and ZnT6-overexpressed (ZnT6OE) cells in comparison to those of H9c2 cells (CON-cells). The IR-cells have higher ZnT6-protein levels than CON-cells while this level was similar to those of ZnT6OE-cells. The [Zn2+]i in IR-cells was increased significantly and mitochondrial localization of ZnT6 was demonstrated in these cells by using confocal microscopy visualization. Furthermore, electron microscopy analysis demonstrated abnormal morphological appearance in both IR-cells and ZnT6OE-cells characterized by irregular mitochondrion cristae and condensed and dilated cisterna in the sarcoplasmic reticulum. Mitochondria were similarly depolarized in both IR-cells and ZnT6OE-cells. The protein expression level of a mitofusin protein MFN2 in the IR-cells was decreased, significantly, whereas, it was found significantly upregulated in both ZnT6-OE-cells and IR-incubated ZnT6OE-cells, which demonstrates the role of ZnT6-overexpression but not IR. Additionally, the total protein level of a mitochondrial fission protein, dynamin-related protein 1, DRP1 was found to be increased over 1.5-fold in IR-cells while this increase was found to be higher in the ZnT6OE-cells than those of IR-cells, demonstrating an additional effect on IR-increase. ZnT6-overexpression induced also significant increases in K-acetylation, trimethylation of histone H3 lysine27, and mono-methylation of histone H3 lysine36, in a similar manner to those of IR-cells. Overall, our data point out an important contribution of ZnT6-overexpression to IR-induced cellular changes, such as alteration in mitochondria function and activation of epigenetic modifications.

Metal Homeostasis in Land Plants: A Perpetual Balancing Act Beyond the Fulfilment of Metalloproteome Cofactor Demands

One of life's decisive innovations was to harness the catalytic power of metals for cellular chemistry. With life's expansion, global atmospheric and biogeochemical cycles underwent dramatic changes. Although initially harmful, they permitted the evolution of multicellularity and the colonization of land. In land plants as primary producers, metal homeostasis faces heightened demands, in part because soil is a challenging environment for nutrient balancing. To avoid both nutrient metal limitation and metal toxicity, plants must maintain the homeostasis of metals within tighter limits than the homeostasis of other minerals. This review describes the present model of protein metalation and sketches its transfer from unicellular organisms to land plants as complex multicellular organisms. The inseparable connection between metal and redox homeostasis increasingly draws our attention to more general regulatory roles of metals. Mineral co-option, the use of nutrient or other metals for functions other than nutrition, is an emerging concept beyond that of nutritional immunity.

Emerging Perspectives in Zinc Transporter Research in Prostate Cancer: An Updated Review

Dysregulation of zinc and zinc transporters families has been associated with the genesis and progression of prostate cancer. The prostate epithelium utilizes two types of zinc transporters, the ZIP (Zrt-, Irt-related Protein) and the ZnTs (Zinc Transporter), to transport zinc from the blood plasma to the gland lumen. ZIP transporters uptake zinc from extracellular space and organelle lumen, while ZnT transporters release zinc outside the cells or to organelle lumen. In prostate cancer, a commonly observed low zinc concentration in prostate tissue has been correlated with downregulations of certain ZIPs (e.g., ZIP1, ZIP2, ZIP3, ZIP14) and upregulations of specific ZnTs (e.g., ZnT1, ZnT9, ZnT10). These alterations may enable cancer cells to adapt to toxic high zinc levels. While zinc supplementation has been suggested as a potential therapy for this type of cancer, studies have yielded inconsistent results because some trials have indicated that zinc supplementation could exacerbate cancer risk. The reason for this discrepancy remains unclear, but given the high molecular and genetic variability present in prostate tumors, it is plausible that some zinc transporters-comprising 14 ZIP and 10 ZnT members-could be dysregulated in others patterns that promote cancer. From this perspective, this review highlights novel dysregulation, such as ZIP-Up/ZnT-Down, observed in prostate cancer cell lines for ZIP4, ZIP8, ZnT2, ZnT4, ZnT5, etc. Additionally, an in silico analysis of an available microarray from mouse models of prostate cancer (Nkx3.1;Pten) predicts similar dysregulation pattern for ZIP4, ZIP8, and ZnT2, which appear in early stages of prostate cancer progression. Furthermore, similar dysregulation patterns are supported by an in silico analysis of RNA-seq data from human cancer tumors available in cBioPortal. We discuss how these dysregulations of zinc transporters could impact zinc supplementation trials, particularly focusing on how the ZIP-Up/ZnT-Down dysregulation through various mechanisms might promote prostate cancer progression.

Effect of estrogen and progesterone on intracellular free zinc and zinc transporter expression in bovine oviduct epithelial cells

Zinc (Zn) plays essential roles in numerous cellular processes. However, there is limited understanding of Zn homeostasis within the bovine reproductive system. This study investigated the influence of estradiol (E2) and progesterone (P4) on Zn transporter expression and intracellular free Zn levels in bovine oviduct epithelial cells (BOEC). For this purpose, cells were harvested from slaughtered cows and cultured in vitro. Intracellular Zn concentrations were measured using FluoZin-3AM staining, while real-time polymerase chain reaction assessed Zn transporter gene expression and quantification. Overall, our results confirmed the gene expression of all the evaluated Zn transporters (ZIP6, ZIP8, ZIP14, ZnT3, ZnT7 and ZnT9), denoted and the active role of E2 and P4 in intracellular Zn regulation. Our findings suggest an interaction between Zn, E2 and P4.

Genetic deletion of zinc transporter ZnT3 induces progressive cognitive deficits in mice by impairing dendritic spine plasticity and glucose metabolism

Zinc transporter 3 (ZnT3) is abundantly expressed in the brain, residing in synaptic vesicles, where it plays important roles in controlling the luminal zinc levels. In this study, we found that ZnT3 knockout in mice decreased zinc levels in the hippocampus and cortex, and was associated with progressive cognitive impairments, assessed at 2, 6, and 9-month of age. The results of Golgi-Cox staining demonstrated that ZnT3 deficiency was associated with an increase in dendritic complexity and a decrease in the density of mature dendritic spines, indicating potential synaptic plasticity deficit. Since ZnT3 deficiency was previously linked to glucose metabolism abnormalities, we tested the expression levels of genes related to insulin signaling pathway in the hippocampus and cortex. We found that the Expression of glucose transporters, GLUT3, GLUT4, and the insulin receptor in the whole tissue and synaptosome fraction of the hippocampus of the ZnT3 knockout mice were significantly reduced, as compared to wild-type controls. Expression of AKT (A serine/threonine protein kinase) and insulin-induced AKT phosphorylation was also reduced in the hippocampus of ZnT3 knockout mice. We hypothesize that the ZnT3 deficiency and reduced brain zinc levels may cause cognitive impairment by negatively affecting glycose metabolism via decreased expression of key components of insulin signaling, as well as via changes in synaptic plasticity. These finding may provide new therapeutic target for treatments of neurodegenerative disorders.

A prognostic and immune related risk model based on zinc homeostasis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. The dysfunction of zinc homeostasis participates in the early and advancing malignancy of HCC. However, the prognostic ability of zinc homeostasis in HCC has not been clarified yet. Here, we showed a zinc-homeostasis related risk model in HCC. Five signature genes including ADAMTS5, PLOD2, PTDSS2, KLRB1, and UCK2 were screened out via survival analyses and regression algorithms to construct the nomogram with clinical characteristics. Experimental researches indicated that UCK2 participated in the progression of HCC. Patients with higher risk scores always had worse outcomes and were more associated with immune suppression according to the analyses of immune related-pathway activation, cell infiltration, and gene expression. Moreover, these patients were likely to exhibit more sensitivity to sorafenib and other antitumor drugs. This study highlights the significant prognostic role of zinc homeostasis and suggests potential treatment strategies in HCC.

Zinc and manganese homeostasis closely interact in mammalian cells

Understanding the homeostatic interactions among essential trace metals is important for explaining their roles in cellular systems. Recent studies in vertebrates suggest that cellular Mn metabolism is related to Zn metabolism in multifarious cellular processes. However, the underlying mechanism remains unclear. In this study, we examined the changes in the expression of proteins involved in cellular Zn and/or Mn homeostatic control and measured the Mn as well as Zn contents and Zn enzyme activities to elucidate the effects of Mn and Zn homeostasis on each other. Mn treatment decreased the expression of the Zn homeostatic proteins metallothionein (MT) and ZNT1 and reduced Zn enzyme activities, which were attributed to the decreased Zn content. Moreover, loss of Mn efflux transport protein decreased MT and ZNT1 expression and Zn enzyme activity without changing extracellular Mn content. This reduction was not observed when supplementing with the same Cu concentrations and in cells lacking Cu efflux proteins. Furthermore, cellular Zn homeostasis was oppositely regulated in cells expressing Zn and Mn importer ZIP8, depending on whether Zn or Mn concentration was elevated in the extracellular milieu. Our results provide novel insights into the intricate interactions between Mn and Zn homeostasis in mammalian cells and facilitate our understanding of the physiopathology of Mn, which may lead to the development of treatment strategies for Mn-related diseases in the future.

Possible involvement of zinc transporter ZIP13 in myogenic differentiation

Ehlers-Danlos syndrome spondylodysplastic type 3 (EDSSPD3, OMIM 612350) is an inherited recessive connective tissue disorder that is caused by loss of function of SLC39A13/ZIP13, a zinc transporter belonging to the Slc39a/ZIP family. We previously reported that patients with EDSSPD3 harboring a homozygous loss of function mutation (c.221G > A, p.G64D) in ZIP13 exon 2 (ZIP13G64D) suffer from impaired development of bone and connective tissues, and muscular hypotonia. However, whether ZIP13 participates in the early differentiation of these cell types remains unclear. In the present study, we investigated the role of ZIP13 in myogenic differentiation using a murine myoblast cell line (C2C12) as well as patient-derived induced pluripotent stem cells (iPSCs). We found that ZIP13 gene expression was upregulated by myogenic stimulation in C2C12 cells, and its knockdown disrupted myotubular differentiation. Myocytes differentiated from iPSCs derived from patients with EDSSPD3 (EDSSPD3-iPSCs) also exhibited incomplete myogenic differentiation. Such phenotypic abnormalities of EDSSPD3-iPSC-derived myocytes were corrected by genomic editing of the pathogenic ZIP13G64D mutation. Collectively, our findings suggest the possible involvement of ZIP13 in myogenic differentiation, and that EDSSPD3-iPSCs established herein may be a promising tool to study the molecular basis underlying the clinical features caused by loss of ZIP13 function.

Back in time to the Gly-rich prototype of the phosphate binding elementary function

Binding of nucleotides and their derivatives is one of the most ancient elementary functions dating back to the Origin of Life. We review here the works considering one of the key elements in binding of (di)nucleotide-containing ligands - phosphate binding. We start from a brief discussion of major participants, conditions, and events in prebiotic evolution that resulted in the Origin of Life. Tracing back to the basic functions, including metal and phosphate binding, and, potentially, formation of primitive protein-protein interactions, we focus here on the phosphate binding. Critically assessing works on the structural, functional, and evolutionary aspects of phosphate binding, we perform a simple computational experiment reconstructing its most ancient and generic sequence prototype. The profiles of the phosphate binding signatures have been derived in form of position-specific scoring matrices (PSSMs), their peculiarities depending on the type of the ligands have been analyzed, and evolutionary connections between them have been delineated. Then, the apparent prototype that gave rise to all relevant phosphate-binding signatures had also been reconstructed. We show that two major signatures of the phosphate binding that discriminate between the binding of dinucleotide- and nucleotide-containing ligands are GxGxxG and GxxGxG, respectively. It appears that the signature archetypal for dinucleotide-containing ligands is more generic, and it can frequently bind phosphate groups in nucleotide-containing ligands as well. The reconstructed prototype's key signature GxGGxG underlies the role of glycine residues in providing flexibility and interactions necessary for binding the phosphate groups. The prototype also contains other ancient amino acids, valine, and alanine, showing versatility towards evolutionary design and functional diversification.

Expression analysis of zinc-metabolizing enzymes in the saliva as a new method of evaluating zinc content in the body: two case reports and a review of the literature

BACKGROUND

The activity level of alkaline phosphatase, a zinc-requiring enzyme in the serum, is used to indicate zinc nutritional status; however, it does not correlate with serum zinc levels or subjective symptoms of taste disorder in many cases. Hence, this study focused on the total activity of alkaline phosphatase, a zinc-requiring enzyme. The total alkaline phosphatasa activity level in the saliva was measured before and after zinc supplementation, and the results were compared with serum zinc levels.

CASE PRESENTATION

This study included patients with hypozincemia, specifically a patient with zinc-deficient taste disorder (patient 1: a 69-year-old Japanese woman) and a patient with glossodynia with zinc deficiency (patient 2: an 82-year-old Japanese woman). Saliva samples were collected, and blood tests were performed before and after zinc supplementation. Subjective symptoms and serum zinc levels were simultaneously evaluated. Zinc supplementation was performed using zinc acetate hydrate or Polaprezinc.

CONCLUSIONS

Total alkaline phosphatase activity levels were found to be associated with serum zinc levels and subjective symptoms. A further study with a higher number of patients is necessary to confirm whether total alkaline phosphatase activity levels more accurately reflect the amounts of zinc in the body than serum zinc levels.

Cross-talk between zinc and calcium regulates ion transport: A role for the zinc receptor, ZnR/GPR39

Zinc is essential for many physiological functions, with a major role in digestive system, skin health, and learning and memory. On the cellular level, zinc is involved in cell proliferation and cell death. A selective zinc sensing receptor, ZnR/GPR39 is a Gq-coupled receptor that acts via the inositol trisphosphate pathway to release intracellular Ca2+. The ZnR/GPR39 serves as a mediator between extracellular changes in Zn2+ concentration and cellular Ca2+ signalling. This signalling pathway regulates ion transporters activity and thereby controls the formation of transepithelial gradients or neuronal membrane potential, which play a fundamental role in the physiological function of these tissues. This review focuses on the role of Ca2+ signalling, and specifically ZnR/GPR39, with respect to the regulation of the Na+/H+ exchanger, NHE1, and of the K+/Cl- cotransporters, KCC1-3, and also describes the physiological implications of this regulation.

A Dietary Supplement Jinghuosu Ameliorates Reproductive Damage Induced by Tripterygium Glycosides

OBJECTIVE

To determine the possible protective effects of Jinghuosu, a dietary supplement (DS), on tripterygium glycosides (TG)-induced reproductive system injury in rats and its underlying mechanisms.

METHODS

A reproductive damage model was established in rats by feeding of TGs. Twenty-eight male Sprague Dawley rats were randomly divided into 4 groups using a random number table (n=7 in each): control (C) group, model (M) group, DS group and L-carnitine (LC) group. Rats in M, DS and LC groups received 40 mg/kg TGs orally. Starting from the 5th week, after administration of TGs for 4 h every day, rats in DS and LC groups were administered with 2.7 g/kg DS and 0.21 g/kg LC, respectively, for protective treatment over the next 4 weeks. Rats in Group C continued to receive the control treatment. Hematoxylin-eosin staining was used for histopathological analysis of rat testicular tissues. Enzyme-linked immunosorbent assay was performed to measure alkaline phosphatase (ALP), lactate dehydrogenase, alcohol dehydrogenase, total antioxidant capacity (T-AOC), superoxide dismutase, glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) concentrations. Chemiluminescence assay was used to determine the serum testosterone content. Quantitative real-time PCR and Western blotting were conducted to analyze the expression of genes and proteins related to the testosterone synthesis pathway and the nuclear factor erythroid 2-related factor 2/heme oxygenase 1 antioxidant pathway.

RESULTS

Oral administration of TGs induced significant increases in the testicular levels of zinc transporter 1 and MDA (P<0.05). On the other hand, sperm concentration, sperm motility, and serum testosterone, serum zinc, testicular zinc, Zrt-, Irt-like protein 1, ALP, luteinizing hormone (LH) receptor, steroidogenic acute regulatory protein, Cytochrome P450 family 11 subfamily A member 1, 3 β -hydroxysteroid dehydrogenase 1 T-AOC, GSH-Px, nuclear factor erythroid 2-related factor 2, heme oxygenase-1 and NAD (P)H: quinone oxidoreductase 1 levels decreased following TGs exposure (P<0.05). All of these phenotypes were evidently reversed by DS (P<0.05).

CONCLUSION

DS Jinghuosu protects against TG-induced reproductive system injury in rats, probably by improving zinc homeostasis, enhancing the testosterone synthesis and attenuating oxidative stress.

Correlative single-cell hard X-ray computed tomography and X-ray fluorescence imaging

X-ray computed tomography (XCT) and X-ray fluorescence (XRF) imaging are two non-invasive imaging techniques to study cellular structures and chemical element distributions, respectively. However, correlative X-ray computed tomography and fluorescence imaging for the same cell have yet to be routinely realized due to challenges in sample preparation and X-ray radiation damage. Here we report an integrated experimental and computational workflow for achieving correlative multi-modality X-ray imaging of a single cell. The method consists of the preparation of radiation-resistant single-cell samples using live-cell imaging-assisted chemical fixation and freeze-drying procedures, targeting and labeling cells for correlative XCT and XRF measurement, and computational reconstruction of the correlative and multi-modality images. With XCT, cellular structures including the overall structure and intracellular organelles are visualized, while XRF imaging reveals the distribution of multiple chemical elements within the same cell. Our correlative method demonstrates the feasibility and broad applicability of using X-rays to understand cellular structures and the roles of chemical elements and related proteins in signaling and other biological processes.

Structures, Mechanisms, and Physiological Functions of Zinc Transporters in Different Biological Kingdoms

Zinc transporters take up/release zinc ions (Zn2+) across biological membranes and maintain intracellular and intra-organellar Zn2+ homeostasis. Since this process requires a series of conformational changes in the transporters, detailed information about the structures of different reaction intermediates is required for a comprehensive understanding of their Zn2+ transport mechanisms. Recently, various Zn2+ transport systems have been identified in bacteria, yeasts, plants, and humans. Based on structural analyses of human ZnT7, human ZnT8, and bacterial YiiP, we propose updated models explaining their mechanisms of action to ensure efficient Zn2+ transport. We place particular focus on the mechanistic roles of the histidine-rich loop shared by several zinc transporters, which facilitates Zn2+ recruitment to the transmembrane Zn2+-binding site. This review provides an extensive overview of the structures, mechanisms, and physiological functions of zinc transporters in different biological kingdoms.

Caged Zn2+ Photolysis in Zebrafish Whole Brains Reveals Subsecond Modulation of Dopamine Uptake

Free, ionic zinc (Zn2+) modulates neurotransmitter dynamics in the brain. However, the sub-s effects of transient concentration changes of Zn2+ on neurotransmitter release and uptake are not well understood. To address this lack of knowledge, we have combined the photolysis of the novel caged Zn2+ compound [Zn(DPAdeCageOMe)]+ with fast scan cyclic voltammetry (FSCV) at carbon fiber microelectrodes in live, whole brain preparations from zebrafish (Danio rerio). After treating the brain with [Zn(DPAdeCageOMe)]+, Zn2+ was released by application of light that was gated through a computer-controlled shutter synchronized with the FSCV measurements and delivered through a 1 mm fiber optic cable. We systematically optimized the photocage concentration and light application parameters, including the total duration and light-to-electrical stimulation delay time. While sub-s Zn2+ application with this method inhibited DA reuptake, assessed by the first-order rate constant (k) and half-life (t1/2), it had no effect on the electrically stimulated DA overflow ([DA]STIM). Increasing the photocage concentration and light duration progressively inhibited uptake, with maximal effects occurring at 100 μM and 800 ms, respectively. Furthermore, uptake was inhibited 200 ms after Zn2+ photorelease, but no measurable effect occurred after 800 ms. We expect that application of this method to the zebrafish whole brain and other preparations will help expand the current knowledge of how Zn2+ affects neurotransmitter release/uptake in select neurological disease states.