Prosapip1- A Novel Mediator of Alcohol Abuse Disorder

We previously reported that excessive consumption of alcohol activates the H-Ras/PI3K/AKT signaling in the nucleus accumbens (NAc) of rodents, which ultimately leads to the activation of the mechanistic target of rapamycin complex 1 (mTORC1) [1-3]. mTORC1 is localized in dendrites and plays an important role in synaptic plasticity by promoting the translation of synaptic proteins [4]. We therefore hypothesized that mTORC1-dependent mRNA translation contributes to neuroadaptations that underlie excessive alcohol consumption. We utilized the high throughput RNA sequencing (RNA seq) approach to identify novel genes whose mTORC1-dependent translation is induced in the NAc in response to excessive alcohol consumption. Among the 12 identified candidates was ProSAP-interacting protein 1 (Prosapip1), a synaptic protein [5] whose function is not well understood. We first determined Prosapip1 expression profile in the brain and found that the protein is highly expressed in the striatum. Next, we confirmed the RNAseq data and showed that the translation of Prosapip1 but not the transcription was induced in response to excessive alcohol drinking in an mTORC1-dependent manner. The increase in Prosapip1 protein in the NAc in response to alcohol drinking was localized to the synaptic fraction and was maintained even after 24 hours of withdrawal. Prosapip1 levels were not altered in brain regions where mTORC1 is not activated by alcohol. Next, we elucidated the potential cellular consequences of mTORC1-dependent increase in Prosapip1 levels in the NAc. Prosapip1 has been indirectly linked to actin cytoskeleton regulation [5], and found that the overexpression of Prosapip1 in the NAc as well as binge drinking of alcohol leads to increased F-actin content. Conversely, shRNA-mediated knockdown endogenous Prosapip1 reduced the amount of actin filaments. Next, we determined whether Prosapip1 contributes to mechanisms underlying alcohol drinking behaviors. To do so, Prosapip1 was knocked-down in the NAc and alcohol intake was evaluated using an operant-self administration paradigm. We found that a reduction of Prosapip1 expression in the NAc lead to an attenuation of operant self-administration of alcohol. The decrease in alcohol self-administration by Prosapip1 knockdown was not due to non-specific changes in locomotion. We further showed that decreasing Prosapip1 levels in the NAc reduces alcohol place preference. Together, our data suggest that alcohol-mediated mTORC1-dependent translation of Prosapip1 in the NAc contributes to increase in F-actin content and drives the motivation to seek and consume alcohol.