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The human organic cation transporter 2 (hOCT2) transports cadmium (Cd 2+ ) and mediates Cd 2+ induced cell death
Author(s) -
Thevenod Frank,
Ciarimboli Giuliano,
Wolff Natascha A.,
Schlatter Eberhard,
Koepsell Hermann
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1202.6
Subject(s) - chemistry , organic cation transport proteins , cadmium , ouabain , microbiology and biotechnology , stereochemistry , biophysics , biochemistry , transporter , sodium , biology , organic chemistry , gene
Kidney proximal tubule (PT) is a major target of chronic Cd 2+ nephrotoxicity and may take up free or bound Cd 2+ forms. Free Cd 2+ uptake pathways are not completely understood. The electrogenic polyspecific OCTs are expressed at the apical and basolateral plasma membrane of PT cells where they translocate small organic cations with one positive charge. Here we investigated Cd 2+ as a substrate for OCT using human OCT1‐3 stably transfected in HEK293. 109 Cd 2+ uptake was only observed in hOCT2 cells, where it was linear at 10 or 100 μM free Cd 2+ for < 60 min.However, uptake was saturable with increasing Cd 2+ with an apparent K m of 53.7 ± 7.2 μmol/l and V max of 481.9 ± 31.34 μmol/l. OCT inhibitors/substrates cimetidine, quinine and choline (IC 50 50 nM, 0.4 μM and 0.8 mM) blocked 109 Cd 2+ uptake. Cu 2+ and Zn 2+ , but not Fe 2+ and Al 3+ , competed 109 Cd 2+ uptake (IC 50 0.5 and 8.0 μM). Uptake of 1 μM ASP + , a model substrate for hOCT, was competed by Cd 2+ and Zn 2+ (IC 50 205 and 60 μM) in hOCT2 cells. 100 μM Cd 2+ uptake into hOCT2 cells for 2.5 h significantly increased apoptosis by annexin V labelling. Using MTT assay, cell viability was significantly reduced by 10 or 100 μM Cd 2+ for 2.5 h or 16 h in hOCT2 cells. Cd 2+ induced cell death was abolished by cimetidine. The data demonstrate for the first time that hOCT2 transports the divalent metal Cd 2+ , where it could contribute to subsequent toxicity. Funded by DFG TH 345/8‐1 and TH 345/10‐1