In silico identification and expression of SLC30 family genes: An expressed sequence tag data mining strategy for the characterization of zinc transporters' tissue expression

BACKGROUND: Intracellular zinc concentration and localization are strictly regulated by two main protein components, metallothioneins and membrane transporters. In mammalian cells, two membrane transporters family are involved in intracellular zinc homeostasis: the uptake transporters called SLC39 or Zip family and the efflux transporters called SLC30 or ZnT family. ZnT proteins are members of the cation diffusion facilitator (CDF) family of metal ion transporters. RESULTS: From genomic databanks analysis, we identified the full-length sequences of two novel SLC30 genes, SLC30A8 and SLC30A10, extending the SLC30 family to ten members. We used an expressed sequence tag (EST) data mining strategy to determine the pattern of ZnT genes expression in tissues. In silico results obtained for already studied ZnT sequences were compared to experimental data, previously published. We determined an overall good correlation with expression pattern obtained by RT-PCR or immunomethods, particularly for highly tissue specific genes. CONCLUSION: The method presented herein provides a useful tool to complete gene families from sequencing programs and to produce preliminary expression data to select the proper biological samples for laboratory experimentation

In vivo expression and functional characterization of the zinc transporter ZnT8 in glucose-induced insulin secretion.

International audienceInsulin-secreting pancreatic beta cells are exceptionally rich in zinc. In these cells, zinc is required for zinc-insulin crystallization within secretory vesicles. Secreted zinc has also been proposed to be a paracrine and autocrine modulator of glucagon and insulin secretion in pancreatic alpha and beta cells, respectively. However, little is known about the molecular mechanisms underlying zinc accumulation in insulin-containing vesicles. We previously identified a pancreas-specific zinc transporter, ZnT-8, which colocalized with insulin in cultured beta cells. In this paper we studied its localization in human pancreatic islet cells, and its effect on cellular zinc content and insulin secretion. In human pancreatic islet cells, ZnT-8 was exclusively expressed in insulin-producing beta cells, and colocalized with insulin in these cells. ZnT-8 overexpression stimulated zinc accumulation and increased total intracellular zinc in insulin-secreting INS-1E cells. Furthermore, ZnT-8-overexpressing cells display enhanced glucose-stimulated insulin secretion compared with control cells, only for a high glucose challenge, i.e. >10 mM glucose. Altogether, these data strongly suggest that the zinc transporter ZnT-8 is a key protein for both zinc accumulation and regulation of insulin secretion in pancreatic beta cells

Zinc transporter gene expression is regulated by pro-inflammatory cytokines: a potential role for zinc transporters in beta-cell apoptosis?

<p>Abstract</p> <p>Background</p> <p>β-cells are extremely rich in zinc and zinc homeostasis is regulated by zinc transporter proteins. β-cells are sensitive to cytokines, interleukin-1β (IL-1β) has been associated with β-cell dysfunction and -death in both type 1 and type 2 diabetes. This study explores the regulation of zinc transporters following cytokine exposure.</p> <p>Methods</p> <p>The effects of cytokines IL-1β, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) on zinc transporter gene expression were measured in INS-1-cells and rat pancreatic islets. Being the more sensitive transporter, we further explored ZnT8 (Slc30A8): the effect of ZnT8 over expression on cytokine induced apoptosis was investigated as well as expression of the insulin gene and two apoptosis associated genes, BAX and BCL2.</p> <p>Results</p> <p>Our results showed a dynamic response of genes responsible for β-cell zinc homeostasis to cytokines: IL-1β down regulated a number of zinc-transporters, most strikingly ZnT8 in both islets and INS-1 cells. The effect was even more pronounced when mixing the cytokines. TNF-α had little effect on zinc transporter expression. IFN-γ down regulated a number of zinc transporters. Insulin expression was down regulated by all cytokines. ZnT8 over expressing cells were more sensitive to IL-1β induced apoptosis whereas no differences were observed with IFN-γ, TNF-α, or a mixture of cytokines.</p> <p>Conclusion</p> <p>The zinc transporting system in β-cells is influenced by the exposure to cytokines. Particularly ZnT8, which has been associated with the development of diabetes, seems to be cytokine sensitive.</p

REGULATION DU ZINC CELLULAIRE (CONSEQUENCES SUR LA MORT PROGRAMMEE)

PARIS5-BU Saints-Pères (751062109) / SudocSudocFranceF

Zinc transporters and their role in the pancreatic ss-cell

Zinc is an essential nutrient with tremendous importance for human health, and zinc deficiency is a severe risk factor for increased mortality and morbidity. As abnormal zinc homeostasis causes diabetes, and because the pancreatic beta-cell contains the highest zinc content of any known cell type, it is of interest to know how zinc fluxes are controlled in beta-cells. The understanding of zinc homeostasis has been boosted by the discovery of multiprotein families of zinc transporters, and one of them zinc transporter 8 (ZnT8) is abundantly and specifically expressed in the pancreatic islets of Langerhans. In this review, we discuss the evidence for a physiological role of ZnT8 in the formation of zinc-insulin crystals, the physical form in which most insulin is stored in secretory granules. In addition, we cross-examine this information, collected in genetically modified mouse strains, to the knowledge that genetic variants of the human ZnT8 gene predispose to the onset of type 2 diabetes and that epitopes on the ZnT8 protein trigger autoimmunity in patients with type 1 diabetes. The overall conclusion is that we are still at the dawn of a complete understanding of how zinc homeostasis operates in normal beta-cells and how abnormalities lead to beta-cell dysfunction and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2012.00199.x, 2012)status: publishe

Differential regulation of zinc efflux transporters ZnT-1, ZnT-5 and ZnT-7 gene expression by zinc levels: a real-time RT–PCR study

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Correction: Brain region-specific alterations of RNA editing in PDE8A mRNA in suicide decedents

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