Quantitative mass spectrometry reveals changes in SNAP-25 isoforms in schizophrenia

Area of Science:

• Neuroscience
• Molecular Psychiatry
• Biochemistry

Background:

• Synaptic vesicle release is mediated by SNARE proteins, including SNAP-25 and syntaxin.
• Alterations in SNARE proteins are implicated in the pathophysiology of schizophrenia.
• SNAP-25 exists in two isoforms, SNAP-25A and SNAP-25B, with distinct functional roles.

Purpose of the Study:

• To quantify SNAP-25 isoforms (SNAP-25A and SNAP-25B) in the ventral caudate of individuals with schizophrenia.
• To investigate the relationship between SNAP-25 isoform levels and SNAP-25-syntaxin interactions.
• To explore the impact of antipsychotic medications on SNAP-25 levels and interactions.

Main Methods:

• Development of a quantitative mass spectrometry assay for SNAP-25 isoforms.
• Analysis of ventral caudate tissue samples from patients with schizophrenia (n=15) and controls (n=13).
• In vitro protein-protein interaction assays and correlation analyses.

Main Results:

• Confirmed significantly lower total SNAP-25 (27%) in schizophrenia patients.
• Observed significantly lower SNAP-25A (31%) but not SNAP-25B (20%) levels in schizophrenia.
• Found a negative correlation between lower SNAP-25A levels and increased SNAP-25-syntaxin interaction.

Conclusions:

• The study suggests that schizophrenia disproportionately affects the SNAP-25A isoform.
• Reduced SNAP-25A may lead to enhanced SNAP-25-syntaxin interactions, potentially contributing to neurotransmission deficits in schizophrenia.
• Antipsychotic treatments (haloperidol, clozapine) did not replicate these findings in rat models.