The sex-specific role of SUMOylation in heroin seeking

About This Grant

Abstract The goal of this proposal is to understand how sex-specific SUMOylation, a post-translational modification mediated by the enzyme UBC9, influences heroin seeking and the functionality of target proteins underlying heroin-induced neuroadaptations. Heroin use disorder has risen to a public health emergency with limited therapeutic options that do not provide permanent symptom alleviation. Limited understanding of long-term neuroadaptations has stymied the development of successful therapeutics. Moreover, despite females being more susceptible to opioid craving and relapse when compared to males, the mechanisms mediating this sex- dependent predisposition remain equivocal. Our group has recently shown sex-specific patterns in SUMOylation underlying fear memory processing. However, the role of sex-specific SUMOylation in influencing brain mechanisms by drugs of abuse, including opioids, remains unknown. In our preliminary studies, we identified 9 SUMOylated proteins in the nucleus accumbens of males at early abstinence following heroin self-administration, but no significantly altered proteins were identified in females. Parallelly, we found that females self-administered a significantly higher number of heroin infusions than males in self-administration behavior, and cue-induced heroin-seeking is potentiated in both males and females at prolonged abstinence (abstinence day 14) when compared to early abstinence, which led us to hypothesize that temporal neuroadaptations contribute to persistent behavioral expression. We also found that depleting ovarian hormones through ovariectomy resulted in significantly higher drug-taking behavior and reduction in UBC9 levels in ovariectomized females when compared to the sham heroin counterpart. Based on these results, we propose to examine the sex-specific mechanisms through which SUMOylation dictates heroin-induced behavioral and neurobiological changes. In Aim 1, we will utilize a novel SUMO-specific proteomic analysis to identify sex-specific SUMOylated targets at prolonged abstinence. We will then examine how the viral mediated expression of SUMO deficient TCP-1η in the NAc shell changes its functionality. In Aim 2, we will use CRISPR-mediated bidirectional regulation of UBC9 coding gene Ube2i and viral-mediated expression of wild-type and SUMO deficient TCP-1η to test if SUMOylation is critical for active heroin taking and cue-induced heroin-seeking behavior and if this modulation diverges based on sex and abstinence. Collectively, this study will answer for the first time a comprehensive understanding of the role of sex-specific SUMOylation in influencing heroin-induced behavioral and neurobiological changes during abstinence. Such knowledge will hold clinical relevance in designing the next generation of therapeutics.