Probing the substrate specificity of the ergothioneine transporter with methimazole, hercynine, and organic cations. 2007

Silke Grigat, and Stephanie Harlfinger, and Sonia Pal, and Ralph Striebinger, and Stefan Golz, and Andreas Geerts, and Andreas Lazar, and Edgar Schömig, and Dirk Gründemann
Department of Pharmacology, University of Cologne, Gleueler Strasse 24, 50931 Cologne, Germany.

Recently, we have identified the ergothioneine (ET) transporter ETT (gene symbol SLC22A4). Much interest in human ETT has been generated by case-control studies that suggest an association of polymorphisms in the SLC22A4 gene with susceptibility to chronic inflammatory diseases. ETT was originally designated a multispecific novel organic cation transporter (OCTN1). Here we reinvestigated, based on stably transfected 293 cells and with ET as reference substrate, uptake of quinidine, verapamil, and pyrilamine. ETT from human robustly catalyzed transport of ET (68micfrol/(minmgprotein)), but no transport of organic cations was discernible. With ET as substrate, ETT was relatively resistant to inhibition by selected drugs; the most potent inhibitor was verapamil (K(i)=11micromol/l). The natural compound hercynine and antithyroid drug methimazole are related in structure to ET. However, efficiency of ETT-mediated transport of methimazole (K(i)=7.5mmol/l) was 130-fold lower, and transport of hercynine (K(i)=1.4mmol/l) was 25-fold lower than transport of ET. ETT from mouse, upon expression in 293 cells, catalyzed high affinity, sodium-driven uptake of ET very similar to ETT from human. Additional real-time PCR experiments based on 16 human tissues revealed ETT mRNA levels considerably lower than in bone marrow. Our experiments establish that ETT is highly specific for its physiological substrate ergothioneine. ETT is not a cationic drug transporter, and it does not have high affinity for organic cation inhibitors. Detection of ETT mRNA or protein can therefore be utilized as a specific molecular marker of intracellular ET activity.

UI MeSH Term Description Entries
D008713 Methimazole A thioureylene antithyroid agent that inhibits the formation of thyroid hormones by interfering with the incorporation of iodine into tyrosyl residues of thyroglobulin. This is done by interfering with the oxidation of iodide ion and iodotyrosyl groups through inhibition of the peroxidase enzyme. Methymazol,Thiamazole,1-Methyl-2-mercaptoimidazole,Favistan,Mercasolyl,Mercazol,Mercazole,Mercazolyl,Merkazolil,Methizol,Methylmercaptoimidazole,Metisol,Metizol,Strumazol,Tapazole,Thiamazol Henning,Thiamazol Hexal,Thimazol,Thyrozol,Tiamazol,Tirodril,1 Methyl 2 mercaptoimidazole,Henning, Thiamazol,Hexal, Thiamazol
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D004880 Ergothioneine A naturally occurring metabolite of HISTIDINE that has antioxidant properties. Thioneine,2-Thiol-L-histidine-betaine,2 Thiol L histidine betaine
D006639 Histidine An essential amino acid that is required for the production of HISTAMINE. Histidine, L-isomer,L-Histidine,Histidine, L isomer,L-isomer Histidine
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001622 Betaine A naturally occurring compound that has been of interest for its role in osmoregulation. As a drug, betaine hydrochloride has been used as a source of hydrochloric acid in the treatment of hypochlorhydria. Betaine has also been used in the treatment of liver disorders, for hyperkalemia, for homocystinuria, and for gastrointestinal disturbances. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1341) Lycine,Oxyneurine,Acidin-Pepsin,Betaine Hydrochloride,C.B.B.,Citrate de Bétaïne Beaufour,Citrate de Bétaïne UPSA,Cystadane,Glycine Betaine,Hepastyl,Novobetaine,Scorbo-bétaïne,Stea-16,Acidin Pepsin,AcidinPepsin,Betaine, Glycine,Hydrochloride, Betaine,Scorbo bétaïne,Scorbobétaïne,Stea 16,Stea16
D001692 Biological Transport The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments. Transport, Biological,Biologic Transport,Transport, Biologic
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D013379 Substrate Specificity A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D027701 Organic Cation Transport Proteins A family of proteins involved in the transport of organic cations. They play an important role in the elimination of a variety of endogenous substances, xenobiotics, and their metabolites from the body. Membrane Transport-Proteins, Organic Cation

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