The nongenomic effects of physiological and environmental estrogens on dopamine transporter function

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Title: The nongenomic effects of physiological and environmental estrogens on dopamine transporter function
Author: Rebecca Ann Alyea
Abstract: Neurological diseases and neuropsychiatric disorders that vary depending on female life stages suggest that sex hormones may influence the function of neurotransmitter regulatory machinery such as the dopamine transporter (DAT ) . In this dissertation we tested the rapid nongenomic effects of several physiological estrogens [estradiol (E2 ) estrone (E1 ) , and estriol (E3 )] and xenoestrogens (XEs ) , such as organochlorine pesticides [dieldrin , endosulfan , and o¡¯ ,p¡¯ -dichlorodiphenylethylene (DDE )] , plastics manufacturing by -products /detergents (nonylphenol , bisphenol A ) , and the synthetic estrogen DES for effects on DAT function . We characterized membrane estrogen receptors (ERs ) and their responses using a nontransfected continuous rat cell line (PC12 ) . We showed that PC12 cells express membrane ER¥á , ER©¬ , GPR30 , and the DAT , and that a two day NGF -©¬ treatment increased the levels of DAT and ER¥á . Low concentrations (10 -14 -10 -8M ) of E2 administered for 9 minutes caused DA efflux , which was not dependent on extracellular Ca2+ -mediated exocytotic release from vesicular monoamine transporter vesicles (VMATs ) . XE concentrations ranging from 10 -14 -10 -8M caused dose -response patterns distinct from that caused by E2 . The rapidity and the mimicking of this response by a cell membrane -impermeable E2 -dendrimer conjugate both suggest a non -genomic , membrane -initiated response mechanism . Using receptor -selective agonist /antagonists and siRNA knockdowns for ER¥á , ER¥â , and GPR30 , we determined that E2 -mediated dopamine efflux at 9 minutes is mediated by ER¥á , with inhibitor contributions from ER©¬ and GPR30 . Using kinase inhibitors we showed that E2 -mediated dopamine efflux is also dependent on protein kinase C and MEK activation , but not on PI3K or protein kinase A . In plasma membrane -enriched fractions there were ligand -independent associations of ER¥á and ER©¬ (but not GPR30 ) with the DAT . Conditions which caused efflux (a 9 min 10 -9M E2 treatment ) also caused trafficking of ER¥á to , and ER©¬ away , from the plasma membrane . In contrast , E1 and E3 inhibited efflux while causing DAT to leave the membrane . We used kinase activity screens to develop signaling profiles for E2 and BPA ; XEs causing dopamine efflux have distinct kinase activation profiles , which could contribute to their abilities to disregulate endocrine functions . Mechanisms that we described in these studies could explain how both physiological and environmental contaminant estrogens influence DAT -dependent diseases .
URI: http : / /hdl .handle .net /2152 .3 /284
Date: 2008-12-01

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The nongenomic effects of physiological and environmental estrogens on dopamine transporter function. Doctoral dissertation, The University of Texas Medical Branch. Available electronically from http : / /hdl .handle .net /2152 .3 /284 .

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