title: Intracellular anion fluorescence assay for sodium/iodide symporter substrates.
abstract: The sodium/iodide symporter (NIS) is primarily responsible for iodide accumulation in the thyroid gland for the synthesis of thyroid hormones; however, it can also transport other lyotropic anions in the thyroid gland and nonthyroid tissues. Some NIS substrates have important physiological or clinical roles, and others are environmental contaminants with health-related consequences. The aim of this study was to assess the utility of a yellow fluorescent protein variant, YFP-H148Q/I152L, as a biosensor to monitor the cellular uptake of NIS substrates, including thiocyanate (SCN(-)), nitrate (NO(3)(-)), chlorate (ClO(3)(-)), perchlorate (ClO(4)(-)), and perrhenate (ReO(4)(-)). The fluorescence of purified YFP-H148Q/I152L was suppressed by anions with an order of potency of ReO(4)(-)>ClO(4)(-)=I(-)=SCN(-)=ClO(3)(-)>NO(3)(-)≫Cl(-). Anions also suppressed the fluorescence of YFP-H148Q/I152L expressed in FRTL-5, a thyroid cell line with high NIS expression. Quantitation of intracellular concentrations revealed differences among anions in the affinity and maximal velocity of NIS-mediated uptake as well as in the rate constant for passive efflux. These results suggest that YFP-H148Q/I152L can serve as an intracellular biosensor of NIS-transported anions and may be useful to study the physiology of endogenous anions as well as the health-related consequences of environmental anions.
authors.affiliation: Medical Genetics Unit, Department of Gynecologic, Obstetric, and Pediatric Sciences, University of Bologna, Bologna 401 38, Italy.
authors.forename: Julie
authors.initials: J
authors.lastname: Di Bernardo
authors.forename: Carmela
authors.initials: C
authors.lastname: Iosco
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Rhoden
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D001681:Biological Assay; D002478:Cells, Cultured; D002704:Chlorates / Q000378:metabolism; D007454:Iodides / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D009566:Nitrates / Q000378:metabolism; D010472:Perchlorates / Q000378:metabolism; D051381:Rats; D012211:Rhenium / Q000378:metabolism; D027981:Symporters / Q000378:metabolism*; D013861:Thiocyanates / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism; D000099209:Sodium-Iodide Symporters
chemical_list: D000838:Anions; D001426:Bacterial Proteins; D002704:Chlorates; D007454:Iodides; D008164:Luminescent Proteins; D009566:Nitrates; D010472:Perchlorates; D012211:Rhenium; D027981:Symporters; D013861:Thiocyanates; D000099209:Sodium-Iodide Symporters; C054562:yellow fluorescent protein, Bacteria; C015428:perrhenate; C031760:thiocyanate; C494474:perchlorate