Dopamine Transporter Knock-In Mice with a Disrupted PDZ-Protein Binding Motif Display Hyperactivity and Could be Insensitive to Amphetamine

Abstract

Dopamine has an important modulatory role in the central nervous system and an impairment of function is associated with several neuropsychiatric diseases. Re-uptake from the extracellular compartment by the dopamine transporter (DAT) is crucial for homeostatic transmitter levels. Recent data suggest that DAT is part of a highly complex multi-protein network controlling critical aspects of DAT function including synaptic distribution, compartmentalization and surface targeting. In an attempt to investigate specific protein-protein interactions involving DAT, we generated knock-in mice expressing DAT with perturbed ability to interact with PDZ-domain proteins. These DAT knock-in mice displayed increased spontaneous locomotor activity and lacked the hyperlocomotor response to amphetamine treatment (2mg/kg i.p.). The behavioural response was associated with reduced DAT-immunoreactivity in the striatum and midbrain regions. In striatal membrane preparations, DAT binding sites were reduced and the remaining DAT sites were functional. Autoradiography studies further supported reduced number of dopamine transporters in striatal tissue. Our results suggest that disruption of PDZ-protein interactions has profound influence on DAT function as evidenced by hyperactive knock-in mice lacking locomotor response to amphetamine.