S. Doolen et Nr. Zahniser, Protein tyrosine kinase inhibitors alter human dopamine transporter activity in Xenopus oocytes, J PHARM EXP, 296(3), 2001, pp. 931-938
Citations number
36
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
The dopamine (DA) transporter (DAT) regulates dopaminergic synaptic transmi
ssion by controlling extracellular levels of DA. Thus, understanding signal
ing mechanisms that alter DAT function is critical for understanding dopami
nergic neurotransmission. We have expressed the human DAT (hDAT) in Xenopus
laevis oocytes to test the hypothesis that protein tyrosine kinases (PTKs)
acutely regulate DAT function by altering cell surface expression of the t
ransporter. Using a relatively high concentration of DA (10 muM), we found
that several PTK inhibitors, namely, genistein, lavendustin A, and tyrphost
in 25 (10 muM), decreased DA uptake velocity by 58, 41, and 30% of control,
respectively. Furthermore, genistein potently inhibited DA uptake with a K
-i = 68 nM. Kinetic analysis confirmed that genistein decreased the V-max o
f the DAT, with no change in K-m. The effects of PTK inhibition on hDAT-ass
ociated currents were also measured. All three PTK inhibitors attenuated su
bstrate transport-associated currents to similar extents as DA uptake. In c
ontrast, the potent Src inhibitor 4-amino-5-(4-chlorophenyl)- 7-(t-butyl) p
yrazolo[3,4-d] pyrimidine (PP2) did not significantly inhibit either DA upt
ake or transport-associated currents. PTK inhibitors decreased hDAT-associa
ted leak currents, however in a more variable manner than for uptake and tr
ansport-associated currents. Genistein also decreased cell surface binding
of [H-3] WIN 35,428 to hDAT by 48% of control. Together, these data provide
several lines of evidence suggesting that PTK inhibition rapidly reduces h
DAT activity via redistribution of the transporter away from the cell surfa
ce. Thus, PTKs likely represent another component of cellular signaling cas
cades that acutely regulate neurotransmitter transporters.