Calcium-binding proteins are altered in the cerebellum in schizophrenia

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.

Cerebellar Calcium-Binding Protein and Neurotrophin Receptor Defects in Down Syndrome and Alzheimer's Disease

“…However, a reduction in PC Parv immunoreactivity (Stepień et al, 2012) and cell size (Satoh et al, 1991) has been described in AD compared to controls. Decreases in PC Parv mRNA levels and Parv-ir neuron numbers occur in people with autism (Soghomonian et al, 2017), while an increase in cerebellar Parv levels were found in the schizophrenic brain (Vidal-Domènech et al, 2020). These observations indicate that Parv cells are vulnerable in various neurologic disorders, whereas Calb is associated with cellular resistance in the face of neuropathologic diseases (Fairless et al, 2019).…”

Analysis of Molecular Networks in the Cerebellum in Chronic Schizophrenia: Modulation by Early Postnatal Life Stressors in Murine Models

“…We found that only 56 of the 250 altered proteins had been previously reported in a gene expression study in an iPSC model of SZ [ 28 ], and that only 16 altered proteins had been reported in a microarray assay in human cerebellum [ 25 ] ( Figure 1 E, Supplementary Dataset S2 ). Eighty-six altered proteins in the cerebellum had been previously reported as altered in other brain regions in SZ, and 20 proteins had been reported in two recent cerebellar proteomic studies [ 26 , 27 ] using different designs (sample pooling versus individual sample analyses), labelling of peptides (chemical labelling quantification versus label-free quantification), type of lysates (cellular fractioning versus whole extracts), mass spectrometry instruments (LTQ-Orbitrap XL, Thermofisher or DS-11, DeNovix versus Q-Exactive, Thermofisher) and age of SZ subjects, among others ( Table S2 and Supplementary Dataset S2 ).…”

“…Despite the growing importance of the cerebellum as a stress target region highly vulnerable to accumulating molecular stress-induced errors in schizophrenia, only a few recent studies have investigated global mRNA [ 25 ] or proteomic alterations in this region [ 26 , 27 ]. The main aim of our study was to identify altered protein networks in the cerebellum with potential therapeutic targets for schizophrenia.…”

‘Omics’ of suicidal behaviour: A path to personalised psychiatry

“…Various tissue samples have been used to date to study the proteomics of suicidal behaviour, including the prefrontal cortex[ 64 - 66 ], amygdala[ 65 ] and cerebellum[ 67 ]. Studies have also examined cerebrospinal fluid[ 68 , 69 ] and plasma[ 70 , 71 ], as although these are still invasive, they represent more easily accessible sources of tissue.…”

“…A reoccurring pattern can be observed, that is similar to the other -omics studies described above. Here, too, there are connections with many of the previously mentioned cell functions and pathways, with indications of association with glial function, neurodegeneration, oxidative stress, neuronal injury[ 64 ], the cytoskeleton, synaptic functions[ 65 ], coagulation and inflammation[ 70 ], decreased glucose utilisation[ 69 ], altered cholesterol metabolism in deliberate self-harm[ 71 ], transport functions and cell communication in schizophrenia suicide victims[ 67 ], the GABA receptor signalling pathway, and pathways related to other neurotransmitters in mood disorder suicide victims ( e.g. , serotonin receptor signalling, melatonin signalling, CREB signalling in neurons, dopamine receptor signalling)[ 66 ].…”