Proteomic characterization of small vessel pathology in PSEN1 E280A familial Alzheimer’s disease

Abstract

AbstractBackgroundVascular pathology is a main contributor to Alzheimer’s disease (AD) progression and severity. We have previously characterized vascular pathology in the PSEN1E280A Colombian kindred. In postmortem analyses we identified that the occipital cortex (OC) is the most affected region by small vessel disease (SVD), including other cortical areas and basal ganglia. Interestingly, frontal cortex (FC) is spared from tau pathology in protected PSEN1E280A cases, while the OC is not. Here we study the proteome of isolated vessels from frontal and occipital cortices to identify differences in molecular pathways.MethodApproximately 400 mg of FC and OC of postmortem brain tissue from PSEN1E280A familial AD (FAD, n = 10), sporadic AD (SAD, n = 10) and controls (HC, n = 5) were homogenized, centrifuged at 2000 g / 5 minutes before using gradient centrifugation at 10000 g / 15 minutes with dextran to receive the microvessel containing pellet which was retrieved and resuspended in lysis buffer for tandem mass tag (TMT) proteomics. Proteomics spectral data were matched to peptide sequences in the human UniProt protein database using the MaxQuant software package. The MaxQuant output files were analysed by MSstatsTMT using R software for statistical analysis. clusterProfiler package was used to perform Gene Ontology enrichment analyses.ResultMicrovessels isolated from AD OC showed 1597 significantly dysregulated proteins when compared to controls, while FC showed 523. FAD showed the majority of upregulated proteins in FC (181 > 88 in SAD), and OC (428 > 84). This pattern was similar in downregulated proteins in the OC (391>171), but not in the FC (106<156) (Fig. 1A). The comparison between FAD cases and controls was the only one that identified a variety of biological processes (BP) during Protein set enrichment analysis. Notably, FAD FC showed upregulation of BP associated to vessel proliferation (Fig. 1B), while the OC showed downregulation of BP associated to immune system and mRNA regulation (Fig. 1C).ConclusionWe have identified the OC as a critical region of FAD pathology. Proteomic analysis of isolated microvessels from this region point towards a more deleterious profile while the FC microvessel proteome indicates an earlier stage of SVD pathology.