title: The Down regulated in Adenoma (dra) gene encodes an intestine-specific membrane sulfate transport protein.
abstract: A gene has been described, Down Regulated in Adenoma (dra), which is expressed in normal colon but is absent in the majority of colon adenomas and adenocarcinomas. However, the function of this protein is unknown. Because of sequence similarity to a recently cloned membrane sulfate transporter in rat liver, the transport function of Dra was examined. We established that dra encodes for a Na(+)-independent transporter for both sulfate and oxalate using microinjected Xenopus oocytes as an assay system. Sulfate transport was sensitive to the anion exchange inhibitor DIDS (4,4'-diisothiocyano-2,2' disulfonic acid stilbene). Using an RNase protection assay, we found that dra mRNA expression is limited to the small intestine and colon in mouse, therefore identifying Dra as an intestine-specific sulfate transporter. dra also had a unique pattern of expression during intestinal development. Northern blot analysis revealed a low level of expression in colon at birth with a marked increase in the first 2 postnatal weeks. In contrast, there was a lower, constant level of expression in small intestine in the postnatal period. Caco-2 cells, a colon carcinoma cell line that differentiates over time in culture, demonstrated a marked induction of dra mRNA as cells progressed from the preconfluent (undifferentiated) to the postconfluent (differentiated) state. These results show that Dra is an intestine-specific Na(+)-independent sulfate transporter that has differential expression during colonic development. This functional characterization provides the foundation for investigation of the role of Dra in intestinal sulfate transport and in the malignant phenotype.
authors.affiliation: Department of Medicine and Genetics, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: D G
authors.initials: DG
authors.lastname: Silberg
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: R H
authors.initials: RH
authors.lastname: Moseley
authors.forename: P G
authors.initials: PG
authors.lastname: Traber
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D017920:Antiporters; D001483:Base Sequence; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology*; D002454:Cell Differentiation; D027963:Chloride-Bicarbonate Antiporters; D003106:Colon / Q000254:growth & development / Q000378:metabolism; D003110:Colonic Neoplasms / Q000473:pathology; D018076:DNA, Complementary / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005796:Genes; D006801:Humans; D007421:Intestine, Small / Q000254:growth & development / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009865:Oocytes; D009928:Organ Specificity; D010070:Oxalates / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000076988:Sulfate Transporters; D013431:Sulfates / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014981:Xenopus
chemical_list: D017920:Antiporters; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D018076:DNA, Complementary; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D010070:Oxalates; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C081011:SLC26A3 protein, human; C489860:Slc26a3 protein, mouse; C489861:Slc26a3 protein, rat; D000076988:Sulfate Transporters; D013431:Sulfates; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid