Zinc transporter genes and urological cancers: integrated analysis suggests a role for ZIP11 in bladder cancer

A Novel Role for the Longevity-Associated Protein SLC39A11 as a Manganese Transporter

The identification of aging- and longevity-associated genes is important for promoting healthy aging. By analyzing a large cohort of Chinese centenarians, we previously found that single-nucleotide polymorphisms (SNPs) in the SLC39A11 gene (also known as ZIP11) are associated with longevity in males. However, the function of the SLC39A11 protein remains unclear. Here, we found that SLC39A11 expression is significantly reduced in patients with Hutchinson-Gilford progeria syndrome (HGPS). In addition, we found that zebrafish with a mutation in slc39a11 that significantly reduces its expression have an accelerated aging phenotype, including a shortened average lifespan, muscle atrophy and reduced swimming, impaired muscle regeneration, gut damage, and abnormal morphology in the reproductive system. Interestingly, these signs of premature aging were more pronounced in male zebrafish than in females. RNA-sequencing analysis revealed that cellular senescence may serve as a potential mechanism for driving this slc39a11 deficiency-induced phenotype in mutant zebrafish. Moreover, immunofluorescence showed significantly increased DNA damage and reactive oxygen species signaling in slc39a11 mutant zebrafish. Using inductively coupled plasma mass spectrometry (ICP-MS), we found that manganese significantly accumulates in slc39a11 mutant zebrafish, as well as in the serum of both global Slc39a11 knockout and hepatocyte-specific Slc39a11 knockout mice, suggesting that this metal transporter regulates systemic manganese levels. Finally, using cultured human fibroblasts, we found that both knocking down SLC39A11 and exposure to high extracellular manganese increased cellular senescence. These findings provide compelling evidence that SLC39A11 serves to protect against the aging process, at least in part by regulating cellular manganese homeostasis.

ZIP transporters-regulated Zn2+ homeostasis: A novel determinant of human diseases

As an essential trace element for organisms, zinc participates in various physiological processes, such as RNA transcription, DNA replication, cell proliferation, and cell differentiation. The destruction of zinc homeostasis is associated with various diseases. Zinc homeostasis is controlled by the cooperative action of zinc transporter proteins that are responsible for the influx and efflux of zinc. Zinc transporter proteins are mainly categorized into two families: Zrt/Irt-like protein (SLC39A/ZIP) family and zinc transporter (SLC30A/ZNT) family. ZIP transporters contain 14 members, namely ZIP1-14, which can be further divided into four subfamilies. Currently, ZIP transporters-regulated zinc homeostasis is one of the research hotspots. Cumulative evidence suggests that ZIP transporters-regulated zinc homeostasis may cause physiological dysfunction and contribute to the onset and progression of diverse diseases, such as cancers, neurological diseases, and cardiovascular diseases. In this review, we initially discuss the structure and distribution of ZIP transporters. Furthermore, we comprehensively review the latest research progress of ZIP transporters-regulated zinc homeostasis in diseases, providing a new perspective into new therapeutic targets for treating related diseases.

Single nucleotide polymorphisms and Zn transport by ZIP11 shape functional phenotypes of HeLa cells

Zinc (Zn) is a vital micronutrient with essential roles in biological processes like enzyme function, gene expression, and cell signaling. Disruptions in the cellular regulation of Zn2+ ions often lead to pathological states. Mammalian Zn transporters, such as ZIP11, play a key role in homeostasis of this ion. ZIP11 resides predominately in the nucleus and Golgi apparatus. Our laboratory reported a function of ZIP11 in maintaining nuclear Zn levels in HeLa cervical cancer cells. Analyses of cervical and ovarian cancer patients' datasets identified four coding, single nucleotide polymorphisms (SNPs) in SLC39A11, the gene that encodes ZIP11, correlating with disease severity. We hypothesized that these SNPs might translate to functional changes in the ZIP11 protein by modifying access to substrate availability. We also proposed that a metal-binding site (MBS) in ZIP11 is crucial for transmembrane Zn2+ transport and required for maintenance of various pathogenic phenotypes observed in HeLa cells. Here, we investigated these claims by re-introducing single the SLC39A11 gene encoding for mutant residues associated with the SNPs, as well as MBS mutations into HeLa cells knocked down for the transporter. Some SNPs-encoding ZIP11 variants rescued Zn levels, proliferation, migration, and invasiveness of knockdown (KD) cells. Conversely, single MBS mutations mimicked the traits of KD cells, confirming the transporter's role in establishing and maintaining proliferative, migratory, and invasive traits. Overall, the intricate role of Zn in cellular dynamics and cancer progression underscores the significance of Zn transporters like ZIP11 in potential therapeutic interventions.

Genetic Polymorphisms Involved in Bladder Cancer: A Global Review

Bladder cancer (BC) has been associated with genetic susceptibility. Single peptide polymorphisms (SNPs) can modulate BC susceptibility. A literature search was performed covering the period between January 2000 and October 2020. Overall, 334 articles were selected, reporting 455 SNPs located in 244 genes. The selected 455 SNPs were further investigated. All SNPs that were associated with smoking and environmental exposure were excluded from this study. A total of 197 genes and 343 SNPs were found to be associated with BC, among which 177 genes and 291 SNPs had congruent results across all available studies. These genes and SNPs were classified into eight different categories according to their function.

Zinc Ions Modulate YY1 Activity: Relevance in Carcinogenesis

YY1 is widely recognized as an intrinsically disordered transcription factor that plays a role in development of many cancers. In most cases, its overexpression is correlated with tumor progression and unfavorable patient outcomes. Our latest research focusing on the role of zinc ions in modulating YY1's interaction with DNA demonstrated that zinc enhances the protein's multimeric state and affinity to its operator. In light of these findings, changes in protein concentration appear to be just one element relevant to modulating YY1-dependent processes. Thus, alterations in zinc ion concentration can directly and specifically impact the regulation of gene expression by YY1, in line with reports indicating a correlation between zinc ion levels and advancement of certain tumors. This review concentrates on other potential consequences of YY1 interaction with zinc ions that may act by altering charge distribution, conformational state distribution, or oligomerization to influence its interactions with molecular partners that can disrupt gene expression patterns.

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.

Expression profiles of the genes associated with zinc homeostasis in normal and cancerous breast and prostate cells

Zn2+ dyshomeostasis is an intriguing phenomenon in breast and prostate cancers, with breast cancer cells exhibiting higher intracellular Zn2+ level compared to their corresponding normal epithelial cells, in contrast to the low Zn2+ level in prostate cancer cells. In order to gain molecular insights into the zinc homeostasis of breast and prostate cancer cells, this study profiled the expression of 28 genes, including 14 zinc importer genes (SLC39A1-14) which encode ZIP1-14 to transport Zn2+ into the cytoplasm, 10 zinc exporter genes (SLC30A1-10) which encode ZnT1-10 to transport Zn2+ out of the cytoplasm and 4 metallothionein genes (MT1B, MT1F, MT1X, MT2A) in breast (MCF10A, MCF-7, MDA-MB-231) and prostate (RWPE-1, PC3, DU145) cell lines in response to extracellular zinc exposures at a mild cytotoxic dosage and a benign dosage. The RNA samples were prepared at 0 min (T0), 30 min (T30) and 120 min (T120) in a time course with or without zinc exposure, which were used for profiling the baseline and dynamic gene expression. The up-regulation of MT genes was observed across the breast and prostate cancer cell lines. The expression landscape of SLC39A and SLC30A was revealed by the qRT-PCR data of this study, which sheds light on the divergence of intracellular Zn2+ levels for breast and prostate cancer cells. Taken together, the findings are valuable in unravelling the molecular intricacy of zinc homeostasis in breast and prostate cancer cells.

Zinc transporters as potential therapeutic targets: An updated review

Zinc is an essential trace element that plays important roles in the regulation of various physiological responses in the body. Zinc deficiency is known to cause various health problems, including dysgeusia, skin disorders, and immune disorders. Therefore, the maintenance of healthy zinc content in the body is critical to our healthy life. Zinc homeostasis is tightly controlled by two of the solute carrier protein families SLC30A and SLC39A, called zinc transporters. In the last decade, research on zinc biology has made dramatic progress based on the physiological and functional analysis of zinc transporters in the fields of molecular biology, human genetics, and drug discovery. In particular, since the association between zinc transporters and human diseases was recently reported using human genetics and gene knockout mouse studies, zinc and zinc signals controlled by zinc transporters have been considered useful therapeutic targets. In this review, we introduce the importance of zinc homeostasis based on the findings of zinc transporter functions and their signals in relation to human diseases.

Clinical impact of copy number variation changes in bladder cancer samples

The aim of the present study was to detect copy number variations (CNVs) related to tumour progression and metastasis of urothelial carcinoma through whole-genome scanning. A total of 30 bladder cancer samples staged from pTa to pT4 were included in the study. DNA was extracted from freshly frozen tissue via standard phenol-chloroform extraction and CNV analysis was performed on two alternative platforms (CytoChip Oligo aCGH, 4x44K and Infinium OncoArray-500K BeadChip; Illumina, Inc.). Data were analysed with BlueFuse Multi software and Karyostudio, respectively. The results highlight the role of genomic imbalances in regions containing genes with metastatic and proliferative potential for tumour invasion. A high level of genomic instability in uroepithelial tumours was observed and a total of 524 aberrations, including 175 losses and 349 gains, were identified. The most prevalent genetic imbalances affected the following regions: 1p, 1q, 2q, 4p, 4q, 5p, 5q, 6p, 6q, 7q, 8q, 9p, 9q, 10p, 10q, 11q, 13q and 17q. High-grade tumours more frequently harboured genomic imbalances (n=227) than low-grade tumours (n=103). A total of 36 CNVs in high-grade bladder tumours were detected in chromosomes 1-5, 8-11, 14, 17, 19 and 20. Furthermore, five loss of heterozygosity variants containing 176 genes were observed in high-grade bladder cancer and may be used as potential targets for precision therapy. Revealing specific chromosomal regions related to the metastatic potential of uroepithelial tumours may lay a foundation for implementing molecular CNV profiling of bladder tumours as part of a routine progression risk estimation strategy, thus expanding the personalized therapeutic approach.

Overproduction of Human Zip (SLC39) Zinc Transporters in Saccharomyces cerevisiae for Biophysical Characterization

Zinc constitutes the second most abundant transition metal in the human body, and it is implicated in numerous cellular processes, including cell division, DNA and protein synthesis as well as for the catalytic activity of many enzymes. Two major membrane protein families facilitate zinc homeostasis in the animal kingdom, i.e., Zrt/Irt-like proteins (ZIPs aka solute carrier 39, SLC39, family) and Zn transporters (ZnTs), essentially conducting zinc flux in the opposite directions. Human ZIPs (hZIPs) regulate import of extracellular zinc to the cytosol, being critical in preventing overaccumulation of this potentially toxic metal, and crucial for diverse physiological and pathological processes, including development of neurodegenerative disorders and several cancers. To date, our understanding of structure-function relationships governing hZIP-mediated zinc transport mechanism is scarce, mainly due to the notorious difficulty in overproduction of these proteins for biophysical characterization. Here we describe employment of a Saccharomyces cerevisiae-based platform for heterologous expression of hZIPs. We demonstrate that yeast is able to produce four full-length hZIP members belonging to three different subfamilies. One target (hZIP1) is purified in the high quantity and homogeneity required for the downstream biochemical analysis. Our work demonstrates the potential of the described production system for future structural and functional studies of hZIP transporters.

Zinc dysregulation in cancers and its potential as a therapeutic target

Zinc is an essential element and serves as a structural or catalytic component in many proteins. Two families of transporters are involved in maintaining cellular zinc homeostasis: the ZIP (SLC39A) family that facilitates zinc influx into the cytoplasm, and the ZnT (SLC30A) family that facilitates zinc efflux from the cytoplasm. Zinc dyshomeostasis caused by the dysfunction of zinc transporters can contribute to the initiation or progression of various cancers, including prostate cancer, breast cancer, and pancreatic cancer. In addition, intracellular zinc fluctuations lead to the disturbance of certain signaling pathways involved in the malignant properties of cancer cells. This review briefly summarizes our current understanding of zinc dyshomeostasis in cancer, and discusses the potential roles of zinc or zinc transporters in cancer therapy.

Maintenance of Intestinal Epithelial Homeostasis by Zinc Transporters

Zinc is an essential micronutrient for normal organ function, and dysregulation of zinc metabolism has been implicated in a wide range of diseases. Emerging evidence has revealed that zinc transporters play diverse roles in cellular homeostasis and function by regulating zinc trafficking via organelles or the plasma membrane. In the gastrointestinal tract, zinc deficiency leads to diarrhea and dysfunction of intestinal epithelial cells. Studies also showed that zinc transporters are very important in intestinal epithelial homeostasis. In this review, we describe the physiological roles of zinc transporters in intestinal epithelial functions and relevance of zinc transporters in gastrointestinal diseases.

Zinc Transporter Proteins

Zinc, which is involved in the structure of all enzyme classes, is a micro nutrient element and necessary for growth and development. The ability of zinc to function without causing toxic effects is depends on the protection of its homeostasis. Zinc transporter proteins are responsible for keeping zinc at certain concentrations. Based on their predicted membrane topology, Zn transporters are divided into two major families, SLC39s/ZIPs and SLC30s/ZnTs, which transport Zn in opposite directions through cellular and intracellular membranes. ZIPs increases the zinc concentration in the cytosol. For this, the ZIPs carries the zinc from extracellular and intracellular compartments to the cytosol. ZnTs, reduces the concentration of zinc in the cytosol. For this, ZnTs carries the zinc from the cytosol to extracellular and intracellular compartments. After being transported to the cell, 50% of the zinc is found in the cytoplasm, 30-40% in the nucleus, and 10% in the plasma and organelle membranes. The expression of many zinc transporter proteins in the cell is depending on the concentration of zinc and the physiological problems. The aim of this study is to give information about association of zinc transporter proteins with physiological events and health problems.

Recent Advances in the Role of SLC39A/ZIP Zinc Transporters In Vivo

Zinc (Zn), which is an essential trace element, is involved in numerous mammalian physiological events; therefore, either a deficiency or excess of Zn impairs cellular machineries and influences physiological events, such as systemic growth, bone homeostasis, skin formation, immune responses, endocrine function, and neuronal function. Zn transporters are thought to mainly contribute to Zn homeostasis within cells and in the whole body. Recent genetic, cellular, and molecular studies of Zn transporters highlight the dynamic role of Zn as a signaling mediator linking several cellular events and signaling pathways. Dysfunction in Zn transporters causes various diseases. This review aims to provide an update of Zn transporters and Zn signaling studies and discusses the remaining questions and future directions by focusing on recent progress in determining the roles of SLC39A/ZIP family members in vivo.

Novel lincRNA Susceptibility Gene and Its Role in Etiopathogenesis of Thyrotoxic Periodic Paralysis

Thyrotoxic periodic paralysis (TPP) is a life-threatening neuromuscular complication of thyrotoxicosis characterized by muscle weakness and hypokalemia and with an unclear etiopathogenesis. However, the 17q24.3 locus had been genetically linked to TPP, in which the genetic variant rs312691 (TC genotype) in long intergenic noncoding RNA (lincRNA) CTD-2378E21.1 is located downstream of inward-rectifier potassium (Kir) channel genes [KCNJ2 and its antisense KCNJ2 (AS-KCNJ2)]. A TPP patient with a suppressed thyroid-stimulating hormone level, a high free thyroxine level of (5.8 ng/dL), and low serum potassium level of (2 mEq/L) was evaluated for Kir channel expression during and after recovery from thyrotoxicosis. We observed that circulating lincRNA and Kir expression varied in accordance with thyroid status and TC genotype. To endorse this association of a lincRNA-rs312691 variant with a genetic risk of TPP, an additional series of 37 patients with TPP and 32 patients with thyrotoxic without paralysis (TWP) were assessed. We verified that the risk of minor allele C was greater in TPP than in TWP (odds ratio, 5.289; P = 0.0062), and protective major allele T was more frequent than observed in the 1000 genome controls (odds ratio, 11.90; P < 0.0001). AS-KCNJ2 was downregulated during thyrotoxicosis in the TWP controls carrying allele T and were upregulated in those with TPP with risk allele C. Moreover, KCNJ2 (Kir2.1) expression was reduced during thyrotoxicosis and restored in euthyroid status. We further excluded any other coding variant by performing targeted exome sequencing mutational screening in 17q24.3. Our data suggest that high lincRNA AS-KCNJ2 and CDT-2378E21.1 expression, possibly driven by the triiodothyronine regulatory mechanism, reduces the Kir2.1 expression observed during thyrotoxicosis. This finding could contribute to the understanding of the reduced inward-rectifying current observed during muscle weakness in genetically susceptible TPP patients.

Zinc transporters and dysregulated channels in cancers

As a nutritionally essential metal ion, zinc (Zn) not only constitutes a structural element for more than 3000 proteins but also plays important regulatory functions in cellular signal transduction. Zn homeostasis is tightly controlled by regulating the flux of Zn across cell membranes through specific transporters, i.e. ZnT and ZIP family proteins. Zn deficiency and malfunction of Zn transporters have been associated with many chronic diseases including cancer. However, the mechanisms underlying Zn regulatory functions in cellular signaling and their impact on the pathogenesis and progression of cancers remain largely unknown. In addition to these acknowledged multifunctions, Zn modulates a wide range of ion channels that in turn may also play an important role in cancer biology. The goal of this review is to propose how zinc deficiency, through modified Zn homeostasis, transporter activity and the putative regulatory function of Zn can influence ion channel activity, and thereby contribute to carcinogenesis and tumorigenesis. This review intends to stimulate interest in, and support for research into the understanding of Zn-modulated channels in cancers, and to search for novel biomarkers facilitating effective clinical stratification of high risk cancer patients as well as improved prevention and therapy in this emerging field.