Proteomic analysis reveals protein changes within layer 2 of the insular cortex in schizophrenia

Abnormalities in the size and activity of the insular cortex (IC), a brain region involved in auditory hallucinations and language, have been previously found in brain imaging studies in schizophrenia. In addition, cortical layer 2 has been shown to be abnormal in many brain regions in schizophrenia. In this study, 2-D DIGE was used to quantitatively analyse protein expression in schizophrenia and control cases (n = 15/group) in microdissected layer 2 IC tissue. Proteomic analyses revealed 57 significantly differentially expressed (p<0.05) protein spots in schizophrenia. Validation of differential expression of two of the proteins differentially expressed was subsequently confirmed using Western blotting. This work provides evidence of abnormal protein expression in layer 2 of the IC in schizophrenia, supporting previous work of reduced neuronal size in this cortical layer in the IC. Over half of proteins abnormally expressed in this study have not been reported previously in proteomic studies investigating schizophrenia or neurodegenerative disorders. Proteins found to be abnormally expressed appear to collectively impact on neuronal plasticity through roles in neurite outgrowth, cellular morphogenesis and synaptic function.