Autophagic regulation of cocaine abuse

The objective of this multi-PI R01 application is to determine how the autophagy machinery regulates the development of cocaine abuse. Cocaine is one of the most widely abused drugs, and produces a variety of behaviors including reward, craving, and relapse. Although many pharmacological targets and behavioral interventions have been explored, there are no FDA-approved medications for reducing cocaine use or treating relapse in cocaine addicts. Autophagy is a key lysosomal degradation pathway that targets cargos for degradation either selectively or non-selectively, and is temporally and spatially controlled by more than 30 autophagy genes. Autophagy occurs constitutively at a basal level, and can be further induced by stress. We recently discovered that an autophagy-related protein Becn2/Beclin 2, which forms a complex with the autophagy-inducing class III phosphatidylinositol 3-kinase Vps34, is a novel regulator of acquisition of cocaine reward behaviors via dopamine (DA) D2 receptors (D2Rs). Knockout of Becn2 (but not its homolog Becn1) globally or specifically in DA neurons protects mice from cocaine-induced locomotor stimulation, conditioned place preference, and intravenous self-administration. UPLC/mass spectrometry profiling indicates that cocaine-induced accumulation of DA, but not other neurotransmitters, is attenuated by Becn2 depletion. In addition, pharmacologically inhibiting autophagy kinases upstream of Becn2, including ULK1 and Vps34, mimics the effects of Becn2 depletion/mutation on cocaine-induced reward behaviors and DA accumulation, suggesting the existence of a ULK1-Vps34-Becn2 axis in the regulation of cocaine responses. Furthermore, biochemical analyses reveal that D2R is a degradation target of Becn2 via binding to a Becn2-associated protein GASP1. Genetic inhibition of Becn2 or pharmacological inhibition of ULK1 similarly increases striatal presynaptic D2Rs. Based on these preliminary data, we propose to investigate the hypothesis that the ULK1-Vps34-Becn2 autophagy axis controls vulnerability to cocaine abuse by selectively regulating D2R autoreceptor endolysosomal trafficking and degradation in DA neurons. Using a combination of genetic, imaging, biochemical, cellular and behavioral approaches, we aim to answer the following questions: How does Becn2 function in DA neurons to regulate acquisition of cocaine-taking, dose response, reinstatement of cocaine-seeking, and D2R catabolism (Aim 1)? Is there a ULK1-Vps34-Becn2 autophagy pathway in DA neurons regulating these cocaine reward behaviors, and if so, how does it work (Aim 2)? We anticipate that with these two fundamentally related aims, our study will establish the function and mechanism of a Becn2-centered autophagy axis in the regulation of D2 receptor metabolism, DAergic function, and cocaine-related reward behaviors. A better understanding of this novel molecular mechanism may provide new options for developing treatments for cocaine abuse and additional types of drug abuse.