The role of norepinephrine (NE) in attention, memory, affect, stress, heart 
rate, and blood pressure implicates NE in psychiatric and cardiovascular 
disease. The norepinephrine transporter (NET) mediates reuptake of released 
catecholamines, thus playing a role in the limitation of signaling strength in 
the central and peripheral nervous systems. Nonsynonymous single nucleotide 
polymorphisms (SNPs) in the human NET (hNET) gene that influence transporter 
function can contribute to disease, such as the nonfunctional transporter, 
A457P, identified in orthostatic intolerance. Here, we examine additional amino 
acid variants that have been identified but not characterized in populations 
that include cardiovascular phenotypes. Variant hNETs were expressed in COS-7 
cells and were assayed for protein expression and trafficking using cell-surface 
biotinylation and Western blot analysis, transport of radiolabeled substrate, 
antagonist interaction, and regulation through protein kinase C (PKC)-linked 
pathways by the phorbol ester beta-phorbol-12-myristate-13-acetate. We observed 
functional perturbations in 6 of the 10 mutants studied. Several variants were 
defective in trafficking and transport, with the most dramatic effect observed 
for A369P, which was completely devoid of the fully glycosylated form of 
transporter protein, was retained intracellularly, and lacked any transport 
activity. Furthermore, A369P and another trafficking variant, N292T, impeded 
surface expression of hNET when coexpressed. F528C demonstrated increased 
transport and, remarkably, exhibited both insensitivity to down-regulation by 
PKC and a decrease in potency for the tricyclic antidepressant desipramine. 
These findings reveal functional deficits that are likely to compromise NE 
signaling in SNP carriers in the population and identify key regions of NET 
contributing to transporter biosynthesis, activity, and regulation.