Pharmacological impacts on schizophrenia functional analysis: a postmortem proteome study

ABSTRACT Schizophrenia (SCZ) is a severe and debilitating mental illness. Antipsychotic drugs (APDs) are used to treat both positive and negative SCZ symptoms, by influencing the cellular, subcellular-synaptic, and molecular processes. We posit that these effects influence our understanding of SCZ. To address this, we analyzed postmortem dorsolateral prefrontal cortex grey matter samples from control and SCZ subjects (n=10/group) using liquid-chromatography mass-spectrometry-based proteomics. We retrieved SCZ-altered and APD-influenced proteome-sets using linear and mixed linear models, respectively, and validated them experimentally using independent cohorts and insilico using published datasets. Functional analysis of proteome-sets was contrasted at the biological pathway, cell-type, subcellular-synaptic, and drug-target levels. The SCZ-altered proteome was conserved across several studies from DLPFC and other brain areas and was dependent on drug effect. At the pathway level, we observed an aberrant extracellular event and, except for homeostasis, signal-transduction, cytoskeleton, and dendrites associated downregulated changes, the APDs compensated for the majority of the SCZ-altered pathways. At the cell-type level, the up-and down-regulated SCZ-altered events were associated with two different subsets of striatum projecting layer-5 pyramidal-neurons regulating dopaminergic secretion. At the subcellular synaptic level, compensatory pre- and post-synaptic events were observed. At the drug target level, dopaminergic processes influence the SCZ-altered up-regulated proteome, whereas non-dopaminergic and a diverse array of non-neuromodulatory mechanisms influence the SCZ-altered down-regulated proteome. While these findings are dependent on pharmacological effects, they are also consistent with previous SCZ studies, implying the need to re-evaluate previous results. We discuss our findings in the context of cortico-striatal influence in SCZ-pathology.