title: Constitutive and protein kinase C-induced internalization of the dopamine transporter is mediated by a clathrin-dependent mechanism.
abstract: The amount of dopamine transporter (DAT) present at the cell surface is rapidly regulated by the rates of DAT internalization to endosomes and DAT recycling back to the plasma membrane. The re-distribution of the transporter from the cell surface to endosomes was induced by phorbol ester activation of protein kinase C in porcine aortic endothelial cells stably expressing the human DAT. Inhibition of DAT recycling with the carboxylic ionophore monensin also caused significant accumulation of DAT in early endosomes and a concomitant loss of DAT from the cell surface, due to protein kinase C-independent constitutive internalization of DAT in the absence of recycling. Such monensin-induced relocation of DAT to endosomes was therefore utilized as a measure of the constitutive internalization of DAT. Knock-down of clathrin heavy chain or dynamin II by small interfering RNAs dramatically inhibited both constitutive and protein kinase C-mediated internalization of DAT. In contrast, neither monensin-dependent nor phorbol ester-induced re-distribution of DAT were affected by inhibitors of endocytosis through cholesterol-rich membrane microdomains. Mutational analysis revealed the potential importance of amino acid residues 587-597 in DAT internalization. Altogether, the data suggest that both constitutive and protein kinase C-mediated internalization of DAT utilize the clathrin-dependent endocytic pathway, but likely involve unconventional mechanisms.
authors.affiliation: Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, Colorado 80045, USA.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Sorkina
authors.forename: Brian R
authors.initials: BR
authors.lastname: Hoover
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Zahniser
authors.forename: Alexander
authors.initials: A
authors.lastname: Sorkin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001011:Aorta / Q000166:cytology; D019921:Biotinylation; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D008954:Models, Biological; D008985:Monensin / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D002966:Clathrin; D050483:Dopamine Plasma Membrane Transport Proteins; D007476:Ionophores; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493214:SLC6A3 protein, human; D049452:Green Fluorescent Proteins; D008985:Monensin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D004298:Dopamine