Calcium-binding proteins are altered in the cerebellum in schizophrenia

Francisco Vidal-Domènech,Alfonso Monje,Belén Ramos,Gemma Riquelme,Judit Villén,Isidre Ferrer,Ricard Rodriguez-Mias,Raquel Pinacho,Luis F Callado,América Vera,J Javier Meana

doi:10.1371/journal.pone.0230400

Abstract

Alterations in the cortico-cerebellar-thalamic-cortical circuit might underlie the diversity of symptoms in schizophrenia. However, molecular changes in cerebellar neuronal circuits, part of this network, have not yet been fully determined. Using LC-MS/MS, we screened altered candidates in pooled grey matter of cerebellum from schizophrenia subjects who committed suicide (n = 4) and healthy individuals (n = 4). Further validation by immunoblotting of three selected candidates was performed in two cohorts comprising schizophrenia (n = 20), non-schizophrenia suicide (n = 6) and healthy controls (n = 21). We found 99 significantly altered proteins, 31 of them previously reported in other brain areas by proteomic studies. Transport function was the most enriched category, while cell communication was the most prevalent function. For validation, we selected the vacuolar proton pump subunit 1 (VPP1), from transport, and two EF-hand calcium-binding proteins, calmodulin and parvalbumin, from cell communication. All candidates showed significant changes in schizophrenia (n = 7) compared to controls (n = 7). VPP1 was altered in the non-schizophrenia suicide group and increased levels of parvalbumin were linked to antipsychotics. Further validation in an independent cohort of non-suicidal chronic schizophrenia subjects (n = 13) and non-psychiatric controls (n = 14) showed that parvalbumin was increased, while calmodulin was decreased in schizophrenia. Our findings provide evidence of calcium-binding protein dysregulation in the cerebellum in schizophrenia, suggesting an impact on normal calcium-dependent synaptic functioning of cerebellar circuits. Our study also links VPP1 to suicide behaviours, suggesting a possible impairment in vesicle neurotransmitter refilling and release in these phenotypes.

Highlights

Schizophrenia constitutes a complex disorder with a mixture of symptoms and cognitive deficiencies
Both Purkinje cells and granule cells are key in orchestrating the organisation of this circuitry during development, and defective regulation of the intracellular mechanisms maintaining the normal synaptic functioning of these cells could impact on internal cerebellar circuit activities and the cerebellum output signal to the cortex
To identify proteins significantly altered in schizophrenia in the cerebellum, we analysed the proteomes of pooled protein lysates from four subjects with schizophrenia and four control subjects matched for gender, age and post-mortem delay (S1A Fig and S1 Table)

Summary

Introduction

Schizophrenia constitutes a complex disorder with a mixture of symptoms and cognitive deficiencies. The complex cytoarchitecture of the cerebellar cortex comprises a variety of neurons including GABAergic neurons, such as Purkinje cells, basket cells, stellate cells, and Golgi cells, and glutamatergic cells, such as granule neurons and unipolar brush cells Both Purkinje cells and granule cells are key in orchestrating the organisation of this circuitry during development, and defective regulation of the intracellular mechanisms maintaining the normal synaptic functioning of these cells could impact on internal cerebellar circuit activities and the cerebellum output signal to the cortex. These altered cerebellar circuits have been linked to a number of neurological and psychiatric conditions such as schizophrenia (reviewed in [11,12]). This characteristic makes the cerebellar cortex an attractive area for investigating proteomic changes in a relatively small sample

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Discussion

Conclusion