title: Attenuation of the norepinephrine transporter activity and trafficking via interactions with alpha-synuclein.
abstract: Alpha-synuclein (alpha-Syn) has been studied in the context of Parkinson's disease, but its normative role remains elusive. We have shown that alpha-Syn regulates the homeostasis of dopaminergic and serotonergic synapses, through trafficking of the dopamine and serotonin transporter, respectively. In the present study we sought to determine if alpha-Syn could also modulate noradrenergic signaling, by studying its interactions with the norepinephrine transporter (NET). We co-transfected Ltk- cells with increasing amounts of alpha-Syn DNA and a constant amount of NET DNA, and observed a progressive decrease (68%) in [3H]-NE uptake in cells co-transfected with a ratio of 3:1 alpha-Syn:NET DNA. The Kd of transport did not change, but increasing alpha-Syn caused a decrease in the Vmax of the transporter, from 2.27+/-0.14 to 0.89+/-0.15 pmol/min/10(5) cells, with NET expression alone or 4:1 ratio of alpha-Syn:NET transfection, respectively. Decreases in surface biotinylation and [3H]-nisoxetine binding kinetics in intact cells revealed that NET cell surface expression was attenuated in correlation to the amount of alpha-Syn co-transfected into cells. The interaction between NET and alpha-Syn occurred via the NAC domain of alpha-Syn, the region directly responsible for self-aggregation. These findings are the first to show that alpha-Syn has a central role in the homeostasis of noradrenergic neurons. Together with our previous studies on dopamine and serotonin transporters, we propose that a primary physiological role of alpha-Syn may be to regulate the homeostasis of monoamines in synapses, through modulatory interactions of the protein with monoaminergic transporters.
authors.affiliation: Department of Biochemistry, Molecular and Cell Biology, Georgetown University, Washington, DC 20007, USA.
authors.forename: Christophe
authors.initials: C
authors.lastname: Wersinger
authors.forename: Alexis
authors.initials: A
authors.lastname: Jeannotte
authors.forename: Anita
authors.initials: A
authors.lastname: Sidhu
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002460:Cell Line; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology; D014162:Transfection; D051844:alpha-Synuclein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D050484:Norepinephrine Plasma Membrane Transport Proteins; D051844:alpha-Synuclein; D009638:Norepinephrine