Received for publication May 16, 2006.
Revised October 6, 2006.
Accepted for publication October 6, 2006.

AMPHETAMINE INDUCES A CAMKII-DEPENDENT REDUCTION IN NOREPINEPHRINE TRANSPORTER SURFACE EXPRESSION LINKED TO CHANGES IN SYNTAXIN 1A/TRANSPORTER COMPLEXES

Abstract

Norepinephrine (NE) transporters (NETs) are high-affinity transport proteins that mediate the synaptic clearance of NE following vesicular release. NETs represent a major therapeutic target for antidepressants and are also targets of multiple psychostimulants including amphetamine (AMPH) and cocaine. Recently, we demonstrated that syntaxin 1A (SYN1A) regulates NET surface expression and, through binding to the transporter's NH2 terminus, regulates transporter catalytic function. AMPH induces NE efflux and may also regulate transporter trafficking. We monitored NET distribution and function in catecholaminergic cell lines (CAD) stably transfected with either full-length human NET (CAD-hNET) or with an hNET N-terminal deletion (CAD-hNET_28-47 cells). In hNET-CAD cells, AMPH causes a slow and small reduction of surface hNET with a modest increase in hNET/SYN1A associations at the plasma membrane. In contrast, in CAD-hNET_28-47 cells, AMPH induces a rapid and substantial reduction in surface hNET_28-47 accompanied by a large increase in plasma membrane hNET_28-47/SYN1A complexes. We also found that AMPH in CAD-hNET_28-47 cells induces a robust increase in cytosolic Ca²⁺ and concomitant activation of calcium/calmodulin-dependent protein kinase II (CaMKII). Inhibition of either the increase in intracellular Ca²⁺ or CaMKII activity blocks AMPH stimulated hNET_28-47 trafficking as well as the formation of hNET_28-47/SYN1A complexes. Here, we demonstrate that AMPH stimulation of CAMKII stabilizes a hNET/SYN1A complex. This hNET/SYN1A complex rapidly redistributes, upon AMPH treatment, when mechanisms supported by the transporter's NH2 terminus are eliminated.

Key words: Biogenic Amine, Amphetamines