title: Mitogen-activated protein kinase regulates dopamine transporter surface expression and dopamine transport capacity.
abstract: The dopamine transporter (DAT) regulates the clearance of dopamine (DA) released into the extracellular space and is an important site on which psychostimulants act to produce their effects. Here, we show that mitogen-activated protein kinase (MAPK) regulates the transport capacity and intracellular trafficking of DAT. Incubation of striatal synaptosomes or epitope-tagged human DAT (hDAT) human embryonic kidney (HEK) 293 cells with the MAPK kinase (MEK) inhibitors 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto) butadiene and 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one decreased DA uptake in a concentration- and time-dependent manner. Kinetic studies revealed a decrease in the capacity of transport (Vmax) but no change in Km. Immunoblotting confirmed labeling of p42 and p44 MAPK in untreated striatal synaptosomes and HEK 293 cells, consistent with constitutive MAPK activation, and the inhibitors used decreased MAPK phosphorylation. Biotinylation and confocal imaging studies showed that MAPK inhibition promoted the clathrin-associated redistribution of hDAT from the plasma membrane to the cytosol. In contrast, transient transfection of hDAT-expressing cells with constitutively active MEK increased the Vmax of DA transport without altering Km. However, only a small increase in hDAT cell surface expression was seen. These data demonstrate an involvement of the MAPK cascade in regulating DAT transport capacity in striatum and that inhibition of this cascade decreases DAT cell surface expression in HEK 293 cells. Furthermore, they highlight the potential role of MAPK as a presynaptic mechanism that regulates DA signaling.
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002460:Cell Line; D003342:Corpus Striatum / Q000737:chemistry; D004298:Dopamine / Q000378:metabolism* / Q000493:pharmacokinetics; D050483:Dopamine Plasma Membrane Transport Proteins; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D010455:Peptides / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013574:Synaptosomes / Q000737:chemistry / Q000201:enzymology; D014316:Tritium
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D010455:Peptides; D011993:Recombinant Fusion Proteins; C493214:SLC6A3 protein, human; C493216:Slc6a3 protein, rat; D014316:Tritium; C085706:FLAG peptide; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D004298:Dopamine