Visualization of Dopamine Transporter Trafficking in Live Neurons by Use of Fluorescent Cocane Analogs

Title
Visualization of Dopamine Transporter Trafficking in Live Neurons by Use of Fluorescent Cocane Analogs
Authors
Jacob EriksenSoren G. F. RasmusseTrine Nygaard RasmusChristian Bjerggaard차주환Mu-Fa ZouAmy Hauck NewmanUlrik Gether
Keywords
Visualization; Dopamine transporter; Fluorescent; Cocaine
Issue Date
2009-05
Publisher
The Journal of neuroscience : the official journal of the Society for Neuroscience
Citation
VOL 29, NO 21, 6794-6808
Abstract
The dopamine transporter (DAT) mediates reuptake of dopamine from the synaptic cleft and is a target for widely abused psychostimulants such as cocaine and amphetamine. Nonetheless, little is known about the cellular distribution and trafficking of natively expressed DAT. Here we use novel fluorescently tagged cocaine analogs to visualize DAT and DAT trafficking in cultured live midbrain dopaminergic neurons. The fluorescent tags were extended from the tropane N-position of 2 -carbomethoxy-3 -(3,4-dichlorophenyl)tropane using an ethylamino-linker. The rhodamine-, OR Green-, or Cy3-labeled ligands had high binding affinity for DAT and enabled specific labeling of DAT in live neurons and visualization by confocal imaging. In the dopaminergic neurons, DAT was uniformly distributed in the plasma membrane of the soma, the neuronal extensions, and varicosities along these extensions. FRAP (fluorescence recovery after photobleaching) experiments demonstrated bidirectional movement of DAT in the extensions and indicated that DAT is highly mobile both in the extensions and in the varicosities (immobile fraction less than 30%). DAT was constitutively internalized into vesicular structures likely representing intracellular transporter pools. The internalization was blocked by lentiviral-mediated expression of dominant-negative dynamin and internalized DAT displayed partial colocalization with the early endosomal marker EGFP-Rab5 and with the transferrin receptor. DAT internalization and function was not affected by activation of protein kinase C (PKC) with phorbol- 12-myristate-13-acetate (PMA) or by inhibition with staurosporine or GF109203X. These data are in contrast to findings for DAT in transfected heterologous cells and challenge the paradigm that trafficking and cellular distribution of endogenous DAT is subject to regulation by PKC.
URI
http://pubs.kist.re.kr/handle/201004/35395
ISSN
0270-6474
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