Cloning, expression, and functional analysis of rhesus monkey trace amine-associated receptor 6: evidence for lack of monoaminergic association.
Several recent studies report an association between trace amine-associated receptor 6 (TAAR6) and susceptibility to schizophrenia and bipolar affective disorder in humans. However, endogenous TAAR6 agonists and the receptor signaling profile and brain distribution remain unclear. Here, we clone TAAR6 from the rhesus monkey and use transfected cells to investigate whether this receptor interacts with brain monoamines and a psychostimulant drug to trigger cAMP signaling or extracellular signal-regulated kinase (ERK) phosphorylation, while investigating its expression profile in the rhesus monkey brain. Unlike TAAR1, rhesus monkey TAAR6 did not alter cAMP levels in response to 10 microM of monoamines (dopamine, norepinephrine, serotonin, beta-phenylethylamine (beta-PEA), octopamine, tryptamine, and tyramine) or methamphetamine in stably transfected cells in vitro. Real-time cell electronic sensing analysis indicated that the receptor did not alter cell impedance or change the effect of forskolin on cell impedance at exposure to 20 microM of each monoamine, suggesting a lack of either Gs or Gi-linked signaling. Whereas kappa opioid receptor activation led to ERK phosphorylation at exposure to 1 microM U69593, rhesus monkey TAAR6 had no such effect at exposure to 10 microM of monoamines or methamphetamine. Membrane and cell surface localization of TAAR6 was confirmed by immunocytochemistry, biotinylation, and Western blot testing with a TAAR6 antibody in the transfected cells. Real-time reverse transcriptase-polymerase chain reaction amplification showed that TAAR6 mRNA was undetectable in selected rhesus monkey brain regions. Together, the data reveal that TAAR6 is unresponsive to brain monoamines and is not expressed in rhesus monkey brain monoaminergic nuclei, suggesting TAAR6 lacks direct association with brain monoaminergic neuronal function.
Xie
Zhihua
Z
Division of Neurochemistry, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts 01772, USA.
Vallender
Eric J
EJ
Yu
Naichen
N
Kirstein
Shelli L
SL
Yang
Hong
H
Bahn
Mary E
ME
Westmoreland
Susan V
SV
Miller
Gregory M
GM
D000595:Amino Acid Sequence; D000818:Animals; D015306:Biogenic Monoamines / Q000494:pharmacology; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D015259:Dopamine Agents / Q000494:pharmacology; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008253:Macaca mulatta; D008694:Methamphetamine / Q000494:pharmacology; D008969:Molecular Sequence Data; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
D015306:Biogenic Monoamines; D015259:Dopamine Agents; D043562:Receptors, G-Protein-Coupled; D008694:Methamphetamine; D000242:Cyclic AMP