Identifying Circadian Regulated Proteins in Specific Cell Types of the Nucleus Accumbens involved in Cocaine Reward

Significance

Basic and clinical research strongly suggests there are extensive bidirectional interactions between circadian rhythms and addiction. Disruptions to the circadian system, either by environmental or genetic perturbation, may increase the vulnerability to addiction, while chronic drug use could lead to circadian disruptions that persist during abstinence, contributing to relapse. Although these are intriguing, very little is known about the cellular and molecular mechanisms underlying these relationships. We have identified a novel mechanism for the circadian transcription factor, neuronal PAS domain protein 2 (NPAS2), in the regulation of cocaine reward, potentially via interactions with an unknown co-activator, or co-factors, selectively within dopamine receptor 1 expression (D1+) medium spiny neurons (MSNs) of the nucleus accumbens (NAc). Ongoing studies are investigating the downstream transcriptional targets of NPAS2 using ChIP-seq and RNA-seq, and whether NPAS2 also influences cocaine self-administration. Preliminary data indicates that chronic cocaine increases the expression and activity of NPAS2 in the NAc and prevents the typical interaction between NPAS2 and BMAL1 to activate circadian-driven gene transcription. We propose a novel mechanism by which NPAS2 binds another co-activator to initiate transcription in response to cocaine, since NPAS2 alone cannot drive gene transcription.

Specific Aims

The aims of this proposal will investigate the following: 1) Identify the potential binding partners and co-factors of NPAS2 in response to cocaine in the NAc across the circadian cycle; and 2) Identify the proteins in D1+ and D2+ MSNs of the NAc that are altered by cocaine across the circadian cycle, along with potential proteins downstream of NPAS2 in an effort to integrate with ongoing whole-genome sequencing studies. These pilot funds will be important for investigating a potential novel mechanism by which circadian rhythms influences
motivation and reward by identifying circadian regulated protein networks in specific cell types within a brain region that is a key substrate for integrating motivation and reward signals. The proposed project is directly related to the theme of the Yale/NIDA Neuroproteomics Center to identify altered protein signaling pathways associated with the acute and chronic effects of drugs of abuse as related to addiction.