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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.—Brast, S., Grabner, A., Sucic, S., Sitte, H. H., Hermann, E., Pavenstädt, H., Schlatter, E., and Ciarimboli, G. 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.

Cocaine and methylphenidate (MPH) act as competitive inhibitors at the dopamine transporter (DAT). Both drugs bind DAT with similar affinities, but they differ fundamentally with respect to their a...

The eukaryotic secretory pathway allows synthesized proteins to leave the endoplasmic reticulum and makes its way to the cell surface where it carries out its individual functions. The intracellular pathway through the various cellular compartments comprises different coat protein complexes, namely coat protein complex II (COPII) and coat protein complex I (COPI). The excitatory amino acid transporter 3 (EAAT3) mediates the regulation of the synaptic transmission at the glutamatergic synapse by transporting the neurotransmitter glutamate. Our goal is to understand the key mediators of the secretory pathway who play a pivotal role in transporting the EAAT3 to the surface. The work focuses on looking at the EAAT3 as a cargo within the cells and following it through the anterograde pathway mediated by COPII. The knowledge gained from this work will be able to shed some light in the pathway of EAAT3 through the cell and can be further extrapolated to the other glutamate transporter family members. Furthermore...

Dopamine (DA) signaling is central to movement, cognition, and reward pathways in the CNS and presynaptic DA reuptake mediated by the DA transporter (DAT) terminates DA signaling. DAT is potently i...

Serotonin plays an important role as neurotransmitter in the brain in a number of circuits which can also be linked to reward and cognition. The transporters for these neurotransmitters are located...