Uncoupling DISC1 × D2R Protein-Protein Interactions Facilitates Latent Inhibition in Disc1-L100P Animal Model of Schizophrenia and Enhances Synaptic Plasticity via D2 Receptors

Abstract

Both Disrupted-In-Schizophrenia-1 (DISC1) and dopamine receptors D2R have significant contributions to the pathogenesis of schizophrenia. Our previous study demonstrated that DISC1 binds to D2R and such protein-protein interaction is enhanced in patients with schizophrenia and Disc1-L100P mouse model of schizophrenia (Su et al., 2014). By uncoupling DISC1 × D2R interaction (trans-activator of transcription (TAT)-D2pep), the synthesized TAT-peptide elicited antipsychotic-like effects in pharmacological and genetic animal models, without motor side effects as tardive dyskinesia commonly seen with typical antipsychotic drugs (APDs), indicating that the potential of TAT-D2pep of becoming a new APD. Therefore, in the current study, we further explored the APD-associated capacities of TAT-D2pep. We found that TAT-D2pep corrected the disrupted latent inhibition (LI), as a hallmark of schizophrenia associated endophenotype, in Disc1-L100P mutant mice—a genetic model of schizophrenia, supporting further APD’ capacity of TAT-D2pep. Moreover, we found that TAT-D2pep elicited nootropic effects in C57BL/6NCrl inbred mice, suggesting that TAT-D2pep acts as a cognitive enhancer, a desirable feature of APDs of the new generation. Namely, TAT-D2pep improved working memory in T-maze, and cognitive flexibility assessed by the LI paradigm, in C57BL/6N mice. Next, we assessed the impact of TAT-D2pep on hippocampal long-term plasticity (LTP) under basal conditions and upon stimulation of D2 receptors using quinpirole. We found comparable effects of TAT-D2pep and its control TAT-D2pep-scrambled peptide (TAT-D2pep-sc) under basal conditions. However, under stimulation of D2R by quinpirole, LTP was enhanced in hippocampal slices incubated with TAT-D2pep, supporting the notion that TAT-D2pep acts in a dopamine-dependent manner and acts as synaptic enhancer. Overall, our experiments demonstrated implication of DISC1 × D2R protein-protein interactions into mechanisms of cognitive and synaptic plasticity, which help to further understand molecular-cellular mechanisms of APD of the next generation.

Prevention of Neurite Spine Loss Induced by Dopamine D2 Receptor Overactivation in Striatal Neurons

“…We further found that TAT-D2pep restored the reduced spine density of D2R over-activated striatal neurons, indicating that the dendritic spines of the striatum could be therapeutic targets of this cell-penetrating peptide. In line with our results, increasing D2R-DISC1 complex formation caused by D2R over-activation has been recently demonstrated to decrease long term potentials in mouse hippocampus, indicating a role in synaptic plasticity (Lipina et al, 2018). To our knowledge, this is the first time that TAT-D2pep has been shown to reverse neurite impairment in vitro.…”

“…The following reagents were purchased: Quinpirole hydrochloride (Sigma Aldrich, St Louis, MO, United States), anti-MAP2 (1:1,000; Sigma Aldrich), anti-PSD-95 (1:1,000; Abcam, Cambridge, United Kingdom), anti-synaptophysin (1:1,000; Sigma Aldrich), anti-GSK3α/β (1:1,000; Cell Signaling Technology, Danvers, MA, United States), anti-phospho-GSK3β (Ser9) (1:1000; Cell Signaling Technology), anti-β-actin (1:5000; Millipore, Bedford, MA, United States), anti-GAD67 (1:800; Cell Signaling Technology), anti-D2R (1:400, Santa Cruz Biotechnology, CA, United States), anti-NPY (1:400, Santa Cruz Biotechnology), Alexa Fluor 568 Phalloidin (Invitrogen, Waltham, MA, United States), Alexa Fluor 488-conjugated goat anti-mouse IgG secondary antibody (1:400; Invitrogen) and Alexa Fluor 568-conjugated goat anti-rabbit IgG secondary antibody (1:400; Invitrogen), Cy3B-NHS (GE Healthcare, NSW, Australia), and Alexa Fluor 647-NHS (Thermo Fisher, Waltham, MA, United States). The region from K 211 to T 225 (KIYIVLRRRRKRVNT) of D2R is known to directly interact with DISC1 (Su et al, 2014;Lipina et al, 2018), which is used for designing TAT-D2peps. TAT-D2pep (YGRKKRRQRRR-KIYIVLRRRRKRVNT) and TAT-D2pep-negative control (NC; YGRKKRRQRRR) were synthesized by GenScript (GenScript, Hong Kong Ltd.), and dissolved in ultrapure water to a stock concentration of 10 mM.…”

Canonical and Non-Canonical Antipsychotics’ Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

“…A post-mortem study on the striatum of patients affected by schizophrenia demonstrated an increased interaction between D2R and DISC1 with the formation and accumulation of intraneural complexes [ 367 ]. They are involved in a potential neuroprotective effect, and also seem to exert a modulatory effect on synaptic plasticity, which is able to decrease long-term potentiation (LTP) in the hippocampus of mice [ 368 ]. Zheng and co-authors, using FRET and stochastic optical reconstruction microscopy (STORM) techniques in murine striatal neurons, demonstrated that the D2R-DISC1 complex is also able to influence intracellular signaling and affect the growth of dendritic spines.…”

Dopamine Dynamics and Neurobiology of Non-Response to Antipsychotics, Relevance for Treatment Resistant Schizophrenia: A Systematic Review and Critical Appraisal

“…Consistently with these suggestions, the disruption of the D2R/DISC1 interaction has been found to reverse hyperactivity and prepulse Inhibition (PPI) aberrations in multiple rodent models of psychosis [ 143 ]. Finally, recent studies have demonstrated the involvement of DISC1 × D2R protein-protein interactions in the mechanisms of cognitive and synaptic plasticity and their modulation as pharmacological targets, contributing further insight into the molecular–cellular mechanisms of antipsychotic drugs [ 144 ].…”