title: The cysteines of the extracellular loop are crucial for trafficking of human organic cation transporter 2 to the plasma membrane and are involved in oligomerization.
abstract: Human organic cation transporter 2 (hOCT2) is involved in transport of many endogenous and exogenous organic cations, mainly in kidney and brain cells. Because the quaternary structure of transmembrane proteins plays an essential role for their cellular trafficking and function, we investigated whether hOCT2 forms oligomeric complexes, and if so, which part of the transporter is involved in the oligomerization. A yeast 2-hybrid mating-based split-ubiquitin system (mbSUS), fluorescence resonance energy transfer, Western blot analysis, cross-linking experiments, immunofluorescence, and uptake measurements of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium were applied to human embryonic kidney 293 (HEK293) cells transfected with hOCT2 and partly also to freshly isolated human proximal tubules. The role of cysteines for oligomerization and trafficking of the transporter to the plasma membranes was investigated in cysteine mutants of hOCT2. hOCT2 formed oligomers both in the HEK293 expression system and in native human kidneys. The cysteines of the large extracellular loop are important to enable correct folding, oligomeric assembly, and plasma membrane insertion of hOCT2. Mutation of the first and the last cysteines of the loop at positions 51 and 143 abolished oligomer formation. Thus, the cysteines of the extracellular loop are important for correct trafficking of the transporter to the plasma membrane and for its oligomerization.
authors.affiliation: Experimentelle Nephrologie, Medizinische Klinik und Poliklinik D, Domagkstrasse 3A, 48149 Münster, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Brast
authors.forename: Alexander
authors.initials: A
authors.lastname: Grabner
authors.forename: Sonja
authors.initials: S
authors.lastname: Sucic
authors.forename: Harald H
authors.initials: HH
authors.lastname: Sitte
authors.forename: Edwin
authors.initials: E
authors.lastname: Hermann
authors.forename: Hermann
authors.initials: H
authors.lastname: Pavenstädt
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schlatter
authors.forename: Giuliano
authors.initials: G
authors.lastname: Ciarimboli
mesh_terms: D001692:Biological Transport; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009154:Mutation; D027701:Organic Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D011485:Protein Binding; D055503:Protein Multimerization; D011726:Pyridinium Compounds / Q000493:pharmacokinetics; D046509:Tissue Culture Techniques; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: C032315:4-(4-dimethylaminostyryl)-1-methylpyridinium; D008164:Luminescent Proteins; D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; D011726:Pyridinium Compounds; C491013:SLC22A2 protein, human; D003545:Cysteine
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