| Description |
Methamphetamine (METH) is a psychostimulant drug of abuse that is widely used and easily, chemically, synthesized. In various animal models, high-dose administrations of METH lead to persistent reductions in dopaminergic markers including dopamine (DA), tyrosine hydroxylase, and dopamine transporter (DAT). Certain factors are known to contribute to METH induced neurotoxicity; these include: formation of reactive oxygen species (ROS), hyperthermia, DA release, and of particular relevance to this dissertation, the DAT. The DAT can form oligomers which can be visualized on western blots as both homo-dimers as well as higher-order molecular weight structures. Oligomerization of certain proteins is linked to toxicity and certain disease states. For example, ?-synuclein oligomerization and fibril formation is linked to Parkinson's disease. Given (1) the persistent effects of METH on dopaminergic neurons, which models some aspects of Parkinson's disease, (2) that various neurological disorders exhibit oligomerization of specific proteins, and (3) the direct effects of METH on the DAT, this dissertation tested the hypothesis that neurotoxic regimens of METH alter the oligomerization state of the DAT protein. This dissertation demonstrates that a neurotoxic regimen of METH leads to a marked increase in oligomerization of the DAT. Neither a single injection of METH nor multiple injections of methylenedioxymethamphetamine (MDMA) cause persistent dopaminergic deficits, nor do these drug regimens alter DAT oligomerization. In addition, prevention of factors that are linked to the METH-induced toxicity, such as hyperthermia, DA receptor blockade, and tolerance, also attenuate the formation of the METH-induced DAT oligomers. These data demonstrate a correlation between METH-induced neurotoxicity and DAT oligomer formation. Furthermore, initial structural studies of the DAT oligomer reveal that it is a membrane-associated, disulfide-bonded, glycoprotein. This dissertation is the first work to demonstrate that the DAT can oligomerize in vivo in response to a pharmacological manipulation. The implications for these data are numerous, especially in the area of drugs of abuse research and Parkinson's disease. These initial experiments could elucidate the mechanism of, and possible improved treatments for, addiction, neurotoxicity, Parkinson's disease, as well as other neurodegenerative disorders. |
