title: Mutation of amino acid 475 of rat organic cation transporter 2 (rOCT2) impairs organic cation transport.
abstract: Protein sequence alignments revealed one amino acid position, where organic cation transporters (OCTs, aspartate (D) at position 475 of rOCT2) and organic anion transporters (OATs, arginine (R) at position 466 of rOAT1) are charged oppositely. To address the impact of this amino acid for protein function we cloned rat organic cation transporter 2 (rOCT2), the renal electrogenic cation transporter of the basolateral side of proximal tubule cells. Site-directed mutagenesis was used to generate rOCT2-D475R (rOCT2-mut). Heterologous expression of rOCT2 wild-type (rOCT2-wt) in A6 cells resulted in a significant uptake of the fluorescent organic cation 4-(4-dimethylaminostyryl)-N-methylpyridinium (ASP(+)). Accordingly, rOCT2-wt-transfected COS 7 cells showed an almost fourfold uptake of 25 microM [(14)C]-TEA, whereas rOCT2-mut did not exhibit any uptake of [(14)C]-TEA. These data indicate that rOCT2 transports both ASP(+) and TEA and that aspartate at position 475 of rOCT2 plays a critical role in transport function.
authors.affiliation: Zentrum für Physiologie und Pathophysiologie, Abt Vegetative Physiologie und Pathophysiologie, Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany. abahn@veg-physiol.med.uni-goettingen.de
authors.forename: Andrew
authors.initials: A
authors.lastname: Bahn
authors.forename: Yohannes
authors.initials: Y
authors.lastname: Hagos
authors.forename: Tanja
authors.initials: T
authors.lastname: Rudolph
authors.forename: Gerhard
authors.initials: G
authors.lastname: Burckhardt
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000235:genetics*; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D015870:Gene Expression; D017136:Ion Transport / Q000235:genetics / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000737:chemistry / Q000166:cytology; D016297:Mutagenesis, Site-Directed; D027361:Organic Anion Transporters / Q000235:genetics / Q000502:physiology; D027701:Organic Cation Transport Proteins / Q000235:genetics* / Q000502:physiology*; D000075102:Organic Cation Transporter 2; D051381:Rats; D013329:Structure-Activity Relationship; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D000596:Amino Acids; D027361:Organic Anion Transporters; D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; C100590:Slc22a2 protein, rat