Cloning of dopamine, norepinephrine and serotonin transporters from monkey brain: relevance to cocaine sensitivity.
We used RT-PCR to clone monoamine transporters from Macaca mulatta, Macaca fasicularis and Saimiri sciureus (dopamine transporter; DAT) and Macaca mulatta (norepinephrine transporter; NET and serotonin transporter; SERT). Monkey DAT, NET and SERT proteins were >98% homologous to human and, when expressed in HEK-293 cells, displayed drug affinities and uptake kinetics that were highly correlated with monkey brain or human monoamine transporters. In contrast to reports of other species, we discovered double (leucine for phenylalanine 143 and arginine for glutamine 509; Variant I) and single (proline for leucine 355; Variant II) amino acid variants of DAT. Variant I displayed dopamine transport kinetics and binding affinities for various DAT blockers (including cocaine) versus [3H] CFT (WIN 35, 428) that were identical to wild-type DAT (n=7 drugs; r(2)=0.991). However, we detected a six-fold difference in the affinity of cocaine versus [3H] cocaine between Variant I (IC(50): 488+/-102 nM, SEM, n=3) and wild-type DAT (IC(50): 79+/-8.2 nM, n=3, P<0.05). Variant II was localized intracellularly in HEK-293 cells, as detected by confocal microscopy, and had very low levels of binding and dopamine transport. Also discovered was a novel exon 5 splice variant of NET that displayed very low levels of transport and did not bind cocaine. With NetPhos analysis, we detected a number of highly conserved putative phosphorylation sites on extracellular as well as intracellular loops of the DAT, NET, and SERT, which may be functional for internalized transporters. The homology and functional similarity of human and monkey monoamine transporters further support the value of primates in investigating the role of monoamine transporters in substance abuse mechanisms, neuropsychiatric disorders and development of diagnostic and therapeutic agents.
Harvard Medical School, Division of Neurochemistry, New England Regional Primate Research Center, One Pine Hill Drive, 01772, Southborough, MA, USA.
G M
GM
Miller
S M
SM
Yatin
R
R
De La Garza
M
M
Goulet
B K
BK
Madras
D000595:Amino Acid Sequence; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology; D001923:Brain Chemistry / Q000187:drug effects* / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003042:Cocaine / Q000378:metabolism / Q000494:pharmacology; D019970:Cocaine-Related Disorders / Q000503:physiopathology*; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000378:metabolism / Q000494:pharmacology; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D015345:Oligonucleotide Probes; D011110:Polymorphism, Genetic; D011869:Radioligand Assay; D012453:Saimiri; D012701:Serotonin / Q000493:pharmacokinetics; D050486:Serotonin Plasma Membrane Transport Proteins; D027981:Symporters; D014316:Tritium
D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D015345:Oligonucleotide Probes; D050486:Serotonin Plasma Membrane Transport Proteins; D027981:Symporters; D014316:Tritium; D012701:Serotonin; D003042:Cocaine