Parkinson's disease (PD) is characterized by a loss of dopamine (DA) neurons in substantia nigra and an accumulation of a-synuclein in Lewy bodies, the cytoplasmic inclusions of PD. These and other observations suggest that an understanding of the role of a-synuclein in these processes will provide insights into the pathogenesis of PD. Although the function of this protein is unknown, a-synuclein is likely to be a chaperone. This is suggested by a-synuclein's native unfolded structure, its ability to interact with several key cellular proteins, and its homology to 14-3-3, a family of molecular chaperones. One of the proteins to which 14-3-3 binds is tyrosine hydroxylase (TB), the rate limiting enzyme in catecholamine synthesis. The binding of 14-3-3 to TH occurs primarily to a phosphorylated serine (Ser19) in the N-terminal regulatory domain of the enzyme. The binding of 14-3-3 to Ser19 is required to increase the enzyme's activity and this activation correlates with an increase in catecholamine synthesis. An interaction of 14-3-3 with Ser40 on TH has recently been reported. We have preliminary data suggesting that: (1) a-synuclein and TB interact with each other in brain and in a dopaminergic cell line, (2) the addition of recombinant a-synuclein inhibits TH activity in an in vitro model of TH activity, and (3) overexpression of a-synuclein in a dopaminergic cell line inhibits TH activity, TH phosphorylation, and DA synthesis. Together these data suggest a key role for a-synuclein in TB regulation and link a-synuclein with the regulation of DA synthesis, storage, and release. Thus, the overall goal of this proposal is to explore the role of a-synuclein in TH regulation and DA synthesis and its impact on dopaminergic cell function under normal and pathophysiological conditions. To achieve this goal we propose three specific aims: ? ? (1) To test the hypothesis that a-synuclein inhibition of TH activity is associated with TH Ser19 and Ser40 phosphorylation.(2) To test the hypothesis that a-synuclein-induced TH-inhibition reduces DA release and that the absence of a-synuclein increases DA synthesis and release.(3) To test the hypothesis that a loss of a-synuclein-mediated inhibition of TH is associated with ROS formation and reduced cell viability. ? ? Using a unique combination of in vitro and in vivo approaches, our studies hold promise to expand both our basic understanding of TH regulation and provide further insight into the association between a-synuclein and TH as they relate to several abnormal conditions, including PD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS042094-05
Application #
7103629
Study Section
Special Emphasis Panel (ZRG1-MDCN-2 (01))
Program Officer
Sutherland, Margaret L
Project Start
2002-07-01
Project End
2008-06-30
Budget Start
2006-07-01
Budget End
2008-06-30
Support Year
5
Fiscal Year
2006
Total Cost
$282,781
Indirect Cost
Name
University of Pittsburgh
Department
Neurology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
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