Functional Identification and Molecular Cloning of a Human Brain Vesicle Monoamine Transporter

A vesicle monoamine transporter was functionally identified, molecularly cloned, and characterized from a human substantia nigra cDNA library. The ATP-dependent transport of 5-³H]hydroxytryptamine (³H]5-HT) by digitonin-permeabilized fibroblasts expressing the vesicle monoamine/H^± antiporter in culture exhibited a K_m of 0.55 μM. Reserpine and tetrabenazine, inhibitors of two monoamine binding sites, effectively blocked ³H]5-HT accumulation with K₁ values of 34 and 78 nM, respectively. Pretreatment of cells with as little as 10 nM reserpine in the presence of ATP abolished uptake. The rank order for substrate inhibition of ³H]5-HT uptake for both the previously reported rat vMAT1 and the human transporter clone followed the order 5-HT > dopamine > epinephrine > norepinephrine > 1 -methyl-4-phen- ylpyridinium > 2-phenylethylamine > histamine. The virtually identical transport characteristics of rvMATI and hvMAT1 confirm the relevance of neuropharmacological studies of rat brain biogenic amine uptake and storage to human brain neurochemistry.