Iron Transport-related Genes Research Articles

Molecular Regulation of The Menkes Copper ATPase (Atp7a) and Divalent Metal Transporter 1 (Dmt1) by Iron in Rat Duodenum and IEC‐6 Cells

Iron transport-related genes are induced by iron-deficiency in the mammalian duodenum. We also noted very strong induction of genes related to intestinal copper homeostasis (Atp7a and metallothionein) during iron-deficiency, and intestinal and hepatic Cu-loading. Intestinal copper transport may thus be enhanced by iron deprivation; in fact, our preliminary studies support this supposition and we hypothesize that that Dmt1 and Atp7a play roles in this process. Importantly, 2 proteins involved in intestinal iron transport, hephaestin and ceruloplasmin, are copper-dependent ferroxidases. We further show that Dmt1 protein expression is very strongly induced and present in brush-border membrane (BBM) vesicles, while Atp7a protein levels are also dramatically increased and surprisingly present on both BB and basolateral membrane domains. We demonstrate that both Dmt1 and Atp7a are induced throughout the length of the GI tract. We have now developed IEC-6 cells as an in vitro model of intestinal iron and copper transport. Dmt1 and Atp7a are strongly induced by iron chelation in pre- and post-confluent cells, and membrane associated Atp7a protein expression is also greatly enhanced. Additional mechanistic studies demonstrate that the induction of Dmt1 and Atp7a are likely via distinct molecular mechanisms. Overall, these studies have described novel molecular events in the intestines of iron-deficient rats and IEC-6 cells that may have relevance to understanding the mechanisms involved in upregulation of iron transport during deficient states.

Comparative genomics and phylogenetic analysis of S. dysenteriae subgroup

Genomic compositions of representatives of thirteen S. dysenteriae serotypes were investigated by performing comparative genomic hybridization (CGH) with microarray containing the whole genomic ORFs (open reading frames, ORFs) of E. coli K12 strain MG1655 and specific ORFs of S. dysenteriae A1 strain Sd51197. The CGH results indicated the genomes of the serotypes contain 2654 conserved ORFs originating from E. coli. However, 219 intrinsic genes of E. coli including those prophage genes, molecular chaperones, synthesis of specific O antigen and so on were absent. Moreover, some specific genes such as type II secretion system associated components, iron transport related genes and some others as well were acquired through horizontal transfer. According to phylogenic trees based on genetic composition, it was demonstrated that A1, A2, A8, A10 were distinct from the other S. dysenteriae serotypes. Our results in this report may provide new insights into the physiological process, pathogenicity and evolution of S. dysenteriae.

The Ophthalmic Test for Glanders.

Genes with G/C-rich promoters were up-regulated in the duodenal epithelium of iron-deficient rats including those encoding iron (e.g. Dmt1 and Dcytb) and copper (e.g. Atp7a and Mt1) metabolism-related proteins. It was shown previously that an intestinal copper transporter (Atp7a) was co-regulated with iron transport-related genes by a hypoxia-inducible transcription factor, Hif2α. In the current study, we sought to test the role of Sp1 in transcriptional regulation of Atp7a expression during iron deprivation/hypoxia. Initial studies in IEC-6 cells showed that mithramycin, an Sp1 inhibitor, reduced expression of Atp7a and iron transport-related genes (Dmt1, Dcytb, and Fpn1) and blocked their induction by CoCl2, a hypoxia mimetic. Consistent with this, overexpression of Sp1 increased endogenous Atp7a mRNA and protein expression and stimulated Atp7a, Dmt1, and Dcytb promoter activity. Site-directed mutagenesis and functional analysis of a basal Atp7a promoter construct revealed four functional Sp1 binding sites that were necessary for Hif2α-mediated induction of promoter activity. Furthermore, chromatin immunoprecipitation (ChIP) assays confirmed that Sp1 specifically interacts with the Atp7a promoter in IEC-6 cells and in rat duodenal enterocytes. This investigation has thus revealed a novel aspect of Atp7a gene regulation in which Sp1 may be necessary for the HIF-mediated induction of gene transcription during iron deficiency/hypoxia. Understanding regulation of Atp7a expression may help further clarify the physiological role of copper in the maintenance of iron homeostasis. Furthermore, this Sp1/Hif2α regulatory mechanism may have broader implications for understanding the genetic response of the intestinal epithelium to maintain whole-body iron homeostasis during states of deficiency.Background: A hypoxia-inducible transcription factor (Hif2α) mediates induction of intestinal iron and copper transporters during iron deficiency.Results: Specificity factor 1 (Sp1) is required for transcriptional induction of an intestinal copper transporter (Atp7a) by Hif2α.Conclusion: Sp1 and Hif2α may synergistically mediate the genetic response to iron deficiency.Significance: Understanding molecular mechanisms governing iron absorption may allow modulation of this process during disease states.