Protein interacting with C-kinase 1 (PICK1) is a widely expressed scaffold protein known to interact via its PSD-95/discs-large/ZO-1 (PDZ)-domain with several membrane proteins including the dopamine (DA) transporter (DAT), the primary target for cocaine's reinforcing actions. Here, we establish the importance of PICK1 for behavioral effects observed after both acute and repeated administration of cocaine. In PICK1 knock-out (KO) mice, the acute locomotor response to a single injection of cocaine was markedly attenuated. Moreover, in support of a role for PICK1 in neuroadaptive changes induced by cocaine, we observed diminished cocaine intake in a self-administration paradigm. Reduced behavioral effects of cocaine were not associated with decreased striatal DAT distribution and most likely not caused by the ∼30% reduction in synaptosomal DA uptake observed in PICK1 KO mice. The PICK1 KO mice demonstrated preserved behavioral responses to DA receptor agonists supporting intact downstream DA receptor signaling. Unexpectedly, we found a prominent increase in striatal DA content and levels of striatal tyrosine hydroxylase (TH) in PICK1 KO mice. Chronoamperometric recordings showed enhanced DA release in PICK1 KO mice, consistent with increased striatal DA pools. Viral-mediated knock-down (KD) of PICK1 in cultured dopaminergic neurons increased TH expression, supporting a direct cellular effect of PICK1. In summary, in addition to demonstrating a key role of PICK1 in mediating behavioral effects of cocaine, our data reveal a so far unappreciated role of PICK1 in DA homeostasis that possibly involves negative regulation of striatal TH levels.

The frontline anti-malarial drug artemisinin and its derivatives have also been implicated in modulating multiple mammalian cellular pathways, including the recent identification of targeting γ-aminobutyric acid type A receptor (GABAAR) signaling in the pancreas. Their molecular mechanism of action, however, remains elusive. Here, we present crystal structures of gephyrin, the central organizer at inhibitory postsynapses, in complex with artesunate and artemether at 1.5-Å resolution. These artemisinins target the universal inhibitory neurotransmitter receptor-binding epitope of gephyrin, thus inhibiting critical interactions between gephyrin and glycine receptors (GlyRs) as well as GABAARs. Electrophysiological recordings reveal a significant inhibition of gephyrin-mediated neurotransmission by artemisinins. Furthermore, clustering analyses in primary neurons demonstrate a rapid inhibition and a time-dependent regulation of gephyrin and GABAAR cluster parameters. Our data not only provide a comprehensive model for artemisinin-mediated modulation of inhibitory neurotransmission but also establish artemisinins as potential lead compounds to pharmacologically interfere with this process.