scholarly journals The histidine-rich loop in the extracellular domain of ZIP4 binds zinc and plays a role in zinc transport

2019 ◽  
Vol 476 (12) ◽  
pp. 1791-1803 ◽  
Author(s):  
Tuo Zhang ◽  
Eziz Kuliyev ◽  
Dexin Sui ◽  
Jian Hu
Keyword(s):  
Extracellular Domain ◽  
Zinc Uptake ◽  
Zinc Homeostasis ◽  
Zinc Binding ◽  
Functional Study ◽  
Acrodermatitis Enteropathica ◽  
Zinc Transport ◽  
Metal Transporters ◽  
Histidine Residues ◽  
Zip Family

Abstract The Zrt-/Irt-like protein (ZIP) family mediates zinc influx from extracellular space or intracellular vesicles/organelles, playing a central role in systemic and cellular zinc homeostasis. Out of the 14 family members encoded in human genome, ZIP4 is exclusively responsible for zinc uptake from dietary food and dysfunctional mutations of ZIP4 cause a life-threatening genetic disorder, Acrodermatitis Enteropathica (AE). About half of the missense AE-causing mutations occur within the large N-terminal extracellular domain (ECD), and our previous study has shown that ZIP4–ECD is crucial for optimal zinc uptake but the underlying mechanism has not been clarified. In this work, we examined zinc binding to the isolated ZIP4–ECD from Pteropus Alecto (black fruit bat) and located zinc-binding sites with a low micromolar affinity within a histidine-rich loop ubiquitously present in ZIP4 proteins. Zinc binding to this protease-susceptible loop induces a small and highly localized structural perturbation. Mutagenesis and functional study on human ZIP4 by using an improved cell-based zinc uptake assay indicated that the histidine residues within this loop are not involved in preselection of metal substrate but play a role in promoting zinc transport. The possible function of the histidine-rich loop as a metal chaperone facilitating zinc binding to the transport site and/or a zinc sensor allosterically regulating the transport machinery was discussed. This work helps to establish the structure/function relationship of ZIP4 and also sheds light on other metal transporters and metalloproteins with clustered histidine residues.

scholarly journals Structural defects caused by Acrodermatitis Enteropathica mutations in the extracellular domain account for mistrafficking and malfunction of ZIP4

2020 ◽  
Author(s):  
Eziz Kuliyev ◽  
Chi Zhang ◽  
Dexin Sui ◽  
Jian Hu
Keyword(s):  
Transmembrane Domain ◽  
Extracellular Domain ◽  
Zinc Uptake ◽  
Structural Defects ◽  
Acrodermatitis Enteropathica ◽  
Missense Mutations ◽  
Zinc Transport ◽  
Loss Of Function ◽  
Transporter Family ◽  
Zip Family

AbstractZIP4 is a representative member of the Zrt-/Irt-like protein (ZIP) transporter family and responsible for zinc uptake from diet. Loss-of-function mutations of human ZIP4 (hZIP4) drastically reduce zinc absorption, causing a life-threatening autosomal recessive disorder, Acrodermatitis Enteropathica (AE). Although the zinc transport machinery is located in the transmembrane domain conserved in the entire ZIP family, half of the missense mutations occur in the extracellular domain (ECD) of hZIP4, which is only present in a fraction of mammalian ZIPs. How the AE-causing mutations in the ECD lead to ZIP4 malfunction has not be fully clarified. In this work, we characterized all the seven confirmed AE-causing missense mutations in hZIP4-ECD and found that the variants exhibited completely abolished zinc transport activity measured in a cell-based transport assay. Although the variants were able to be expressed in HEK293T cells, they failed to traffic to cell surface and were largely retained in the ER with immature glycosylation. When the corresponding mutations were introduced in the ECD of ZIP4 from Pteropus Alecto, a close homolog of hZIP4, the variants exhibited impaired protein folding and reduced thermal stability, which likely account for intracellular mistrafficking of the AE-associated variants and as such a total loss of zinc uptake in cells. This work provides a molecular pathogenic mechanism for AE, which lays out a basis for potential therapy using small molecular chaperones.

scholarly journals Aberrant Expression of ZIP and ZnT Zinc Transporters in UROtsa Cells Transformed to Malignant Cells by Cadmium

Stresses ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 78-89
Author(s):  
Soisungwan Satarug ◽  
Scott H. Garrett ◽  
Seema Somji ◽  
Mary Ann Sens ◽  
Donald A. Sens
Keyword(s):  
Mammalian Cells ◽  
Defense Mechanisms ◽  
Prolonged Exposure ◽  
Zinc Homeostasis ◽  
Zinc Transporters ◽  
Aberrant Expression ◽  
Metal Transporters ◽  
Zip Family ◽  
Cation Diffusion Facilitators ◽  
Cellular Zinc

Maintenance of zinc homeostasis is pivotal to the regulation of cell growth, differentiation, apoptosis, and defense mechanisms. In mammalian cells, control of cellular zinc homeostasis is through zinc uptake, zinc secretion, and zinc compartmentalization, mediated by metal transporters of the Zrt-/Irt-like protein (ZIP) family and the Cation Diffusion Facilitators (CDF) or ZnT family. We quantified transcript levels of ZIP and ZnT zinc transporters expressed by non-tumorigenic UROtsa cells and compared with those expressed by UROtsa clones that were experimentally transformed to cancer cells by prolonged exposure to cadmium (Cd). Although expression of the ZIP8 gene in parent UROtsa cells was lower than ZIP14 (0.1 vs. 83 transcripts per 1000 β-actin transcripts), an increased expression of ZIP8 concurrent with a reduction in expression of one or two zinc influx transporters, namely ZIP1, ZIP2, and ZIP3, were seen in six out of seven transformed UROtsa clones. Aberrant expression of the Golgi zinc transporters ZIP7, ZnT5, ZnT6, and ZnT7 were also observed. One transformed clone showed distinctively increased expression of ZIP6, ZIP10, ZIP14, and ZnT1, with a diminished ZIP8 expression. These data suggest intracellular zinc dysregulation and aberrant zinc homeostasis both in the cytosol and in the Golgi in the transformed UROtsa clones. These results provide evidence for zinc dysregulation in transformed UROtsa cells that may contribute in part to their malignancy and/or muscle invasiveness.

Zinc Uptake Regulator (zur) Gene Involved in Zinc Homeostasis and Virulence of Xanthomonas oryzae pv. oryzae in Rice

2007 ◽  
Vol 54 (4) ◽  
pp. 307-314 ◽  
Author(s):  
Wanfeng Yang ◽  
Yan Liu ◽  
Lei Chen ◽  
Tongchun Gao ◽  
Baishi Hu ◽  
...  
Keyword(s):  
Zinc Uptake ◽  
Xanthomonas Oryzae ◽  
Zinc Homeostasis ◽  
Zinc Uptake Regulator

Involvement of hepatic metallothioneins in hypozincemia associated with bacterial infection.

1978 ◽  
Vol 234 (4) ◽  
pp. E399 ◽  
Author(s):  
P Z Sobocinski ◽  
W J Canterbury ◽  
C A Mapes ◽  
R E Dinterman
Keyword(s):  
Amino Acid ◽  
Heat Stability ◽  
Acute Stage ◽  
Zinc Homeostasis ◽  
Zinc Binding ◽  
Live Vaccine Strain ◽  
Infectious Illness ◽  
Hepatic Synthesis ◽  
Major Amino Acid

Hypozincemia was induced in rats by Salmonella typhimurium and live vaccine strain Francisella tularensis (LVS) infections. Hepatic synthesis of zinc-binding proteins (ZBP) was studied in order to elucidate the mechanisms involved in the redistribution of zinc from plasma to liver occurring during infectious illness. ZBP, labeled in vivo with 65Zn, were isolated and identified as metallothioneins based, in part, on their heat stability, dimorphism, and amino acid composition. Cysteine was the major amino acid found in both forms of metallothionein and constituted 28-31% of total residues. The apparent half-life of these proteins as measured by disappearance of 65Zn was determined to be 19 h in a relatively mild infection (LVS) and 38 h in a more severe S. typhimurium infection. Results provide evidence that metallothioneins not only have the previously postulated regulatory role in normal zinc homeostasis but are intimately involved in the zinc redistribution occurring during the acute stage of infectious illness.

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

2021 ◽  
Author(s):  
Sichul Lee ◽  
Joohyun Lee ◽  
Felipe K. Ricachenevsky ◽  
Tracy Punshon ◽  
Ryan Tappero ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Seed Development ◽  
Family Members ◽  
Zinc Homeostasis ◽  
Zip Family

scholarly journals Identification of Zinc-Dependent Mechanisms Used by Group B Streptococcus To Overcome Calprotectin-Mediated Stress

mBio ◽  
2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Lindsey R. Burcham ◽  
Yoann Le Breton ◽  
Jana N. Radin ◽  
Brady L. Spencer ◽  
Liwen Deng ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Metal Ion ◽  
Invasive Disease ◽  
Female Reproductive Tract ◽  
Zinc Uptake ◽  
Wild Type ◽  
Metal Transporters ◽  
High Concentrations ◽  
Group B

ABSTRACT Nutritional immunity is an elegant host mechanism used to starve invading pathogens of necessary nutrient metals. Calprotectin, a metal-binding protein, is produced abundantly by neutrophils and is found in high concentrations within inflammatory sites during infection. Group B Streptococcus (GBS) colonizes the gastrointestinal and female reproductive tracts and is commonly associated with severe invasive infections in newborns such as pneumonia, sepsis, and meningitis. Although GBS infections induce robust neutrophil recruitment and inflammation, the dynamics of GBS and calprotectin interactions remain unknown. Here, we demonstrate that disease and colonizing isolate strains exhibit susceptibility to metal starvation by calprotectin. We constructed a mariner transposon (Krmit) mutant library in GBS and identified 258 genes that contribute to surviving calprotectin stress. Nearly 20% of all underrepresented mutants following treatment with calprotectin are predicted metal transporters, including known zinc systems. As calprotectin binds zinc with picomolar affinity, we investigated the contribution of GBS zinc uptake to overcoming calprotectin-imposed starvation. Quantitative reverse transcriptase PCR (qRT-PCR) revealed a significant upregulation of genes encoding zinc-binding proteins, adcA, adcAII, and lmb, following calprotectin exposure, while growth in calprotectin revealed a significant defect for a global zinc acquisition mutant (ΔadcAΔadcAIIΔlmb) compared to growth of the GBS wild-type (WT) strain. Furthermore, mice challenged with the ΔadcAΔadcAIIΔlmb mutant exhibited decreased mortality and significantly reduced bacterial burden in the brain compared to mice infected with WT GBS; this difference was abrogated in calprotectin knockout mice. Collectively, these data suggest that GBS zinc transport machinery is important for combatting zinc chelation by calprotectin and establishing invasive disease. IMPORTANCE Group B Streptococcus (GBS) asymptomatically colonizes the female reproductive tract but is a common causative agent of meningitis. GBS meningitis is characterized by extensive infiltration of neutrophils carrying high concentrations of calprotectin, a metal chelator. To persist within inflammatory sites and cause invasive disease, GBS must circumvent host starvation attempts. Here, we identified global requirements for GBS survival during calprotectin challenge, including known and putative systems involved in metal ion transport. We characterized the role of zinc import in tolerating calprotectin stress in vitro and in a mouse model of infection. We observed that a global zinc uptake mutant was less virulent than the parental GBS strain and found calprotectin knockout mice to be equally susceptible to infection by wild-type (WT) and mutant strains. These findings suggest that calprotectin production at the site of infection results in a zinc-limited environment and reveals the importance of GBS metal homeostasis to invasive disease.

Intestinal absorption of zinc: a role for a zinc-binding ligand in milk.

1978 ◽  
Vol 235 (5) ◽  
pp. E556
Author(s):  
J R Duncan ◽  
L S Hurley
Keyword(s):  
Human Milk ◽  
Intestinal Mucosa ◽  
Neonatal Period ◽  
Bovine Milk ◽  
Zinc Binding ◽  
Acrodermatitis Enteropathica ◽  
Zinc Absorption ◽  
Human Infants ◽  
Normal Human ◽  
Old Rats

This study examined the proposal that a low molecular weight, zinc-binding ligand (ZBL) in certain milks is important for zinc absorption in the neonatal period. Ten-day-old rats, in which intestinal ZBL is absent, fed (by stomach intubation) 65Zn-labeled ZBL from rat milk, absorbed significantly more 65Zn than those fed free 65ZnCl2 or bovine milk fractions. ZBL from human milk appeared to have an intermediate effect, possibly due to species specificity. 65Zn was found in the ZBL fraction in intestinal mucosa of 10-day-old rats fed rat or human milk fractions, but not in those fed bovine milk or free 65ZnCl2. In contrast, in 18-day-old rats, which have an endogenous intestinal ZBL, there were no differences in zinc absorption, and any of the labeled milk fractions or free 65Zn caused localization of 65Zn in the ZBL fraction of intestinal mucosa. These results support the hypothesis that the intestinal ZBL plays a role in zinc absorption and that in the neonatal period before its development the milk ZBL is valuable for this function. This mechanism may be important in normal human infants as well as in acrodermatitis enteropathica patients.

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