Nurr1/CoREST complexes controlling gene expression in dopamine neurons
Keywords: dopamine, nurr1, corest
Midbrain dopamine neurons play a key role in voluntary movement and motivated behaviors; therefore, these neurons are subjected to plastic processes allowing learning for meaningful behaviors, adaptation and survival. Plastic processes in dopamine neurons underlie also aberrant behaviors as addiction and compulsivity, and compensatory mechanisms during neuronal degeneration. The transcription factor Nurr1 is pivotal to plastic processes in midbrain dopamine neurons. Nurr1 is an orphan nuclear receptor essential for the genesis of midbrain dopamine neurons during development and for their maintenance in adulthood. Nurr1 regulates the expression of characteristic genes of the neurochemical dopamine phenotype such as tyrosine hydroxylase and dopamine transporter, among others, as well genes important for dopamine neurons survival as the tyrosine kinase receptor, ret, and genes for mitochondrial respiration. The mechanisms by which Nurr1 regulates these disparate sets of target genes are unknown. Unlike other nuclear receptors whose activity is regulated by ligand, Nurr1 is a true orphan, whose activity is regulated by adjusting its level of expression and by post-translational modifications. More recently, it came to light that Nurr1-dependent activity is regulated by the interaction with transcriptional corepressors as CoREST, which turns Nurr1 in a transcriptional repressor. CoREST is a family of transcriptional co-repressors formed by CoREST1 (CoREST, RCOR1), CoREST2 (RCOR2) and CoREST3 (RCOR3). Recently, we showed that all CoREST co-repressors are expressed widely in brain of adult rats, coexisting in same neurons. In addition, we showed that the different CoRESTs provide specific transcriptional repressor capacities to the complexes they belong to. We propose that Nurr1-dependent transcriptional activity in dopamine neurons is regulated by specific and selected interaction with members of the CoREST family of transcriptional co-repressors. The hypothesis guiding this project is: “CoREST family of co-repressors regulates Nurr1-dependent transcriptional activity and the expression of genes in dopamine neurons” this hypothesis is based in the following observations: a) Nurr1 interacts with CoREST1; b) CoREST1 binds to the promoter of dopamine genes during development; c) both Nurr1 and CoREST1 interacts with the SUMO E3 ligase PIAS and d) Nurr1 interaction with CoREST1 depends on Nurr1 SUMOylation; e) depolarization increases dopamine gene expression by increasing Nurr1 binding and CoREST1 exits from target gene promoters. To test this hypothesis, we propose to develope four Specific Aims. First, we will determine the mechanisms of interaction and regulation between Nurr1 and CoREST family of co-repressors. We will search for the interaction domains in Nurr1 and CoRESTs and whether the interaction depends on Nurr1 SUMOylation. We will take in vitro and in cell lines experimental approaches to characterize the molecular and dynamic features of Nurr1/CoREST complexes. Second, we will assess the effect of knocking-down CoREST1, CoREST2 and CoREST3 on dopamine neuronal phenotype features and the histone demethylase and deacetylase activities associated to the different CoREST transcriptional repressor complexes in cultured dopamine neurons. Third, we will assess the behavioral and neurochemical effects of knocking down separately each CoREST in adult midbrain using adeno-associated virus (AAV) encoding shRNA against each CoREST. We will carry out a series of behavioral paradigms and measure phasic and tonic dopamine extracellular levels using in vivo microdialysis and fast scan cyclic voltammetry, respectively. Finally, we will carry out RNAseq analysis to determine the transcriptome of CoREST(1,2 or 3) that has relevant behavioral and/or neurochemical role in adult midbrain (fourth aim). The work proposed is highly significant for understanding how Nurr1 regulates the expression of target genes in dopamine neurons, whose function is essential for normal behavior and whose dysfunction leads to major neurological and psychiatric disorders.
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