Our earlier studies have shown that red blood cell (RBC) morphology in Alzheimer's disease (AD) subjects was altered (> 15% of the RBCs were elongated as compared to 5.9% in normal controls (p < 0.0001)). These results suggested alterations in the RBC membrane architecture in AD subjects, possibly due to RBC-β-amyloid interactions and/or changes in the expression of membrane proteins. We hypothesized that the observed changes could be due to changes in the level of the protein components of the cytoskeleton and those linked to the RBC membrane. To examine this, we performed a proteomic analysis of RBC membrane proteins of AD subjects, and their age-matched controls using one pool of samples from each group, following their separation by SDS-PAGE, in-gel Tryptic digestion, LC-MS-MS of peptides generated, and a label-free approach of semi-quantitative analysis of their relative MS spectral intensities.
The data suggest, (1) RBC shape/morphology changes in AD subjects are possibly attributed primarily to the changes (elevation or decrease) in the level of a series of membrane/cytoskeleton proteins involved in regulating the stability and elasticity of the RBC membrane, and (2) changes (elevation or decrease) in the level of a second series of proteins in the RBC membrane proteome reflect similar changes reported earlier by various investigators in AD or animal model of AD. Of particular interest, elevation of oxidative stress response proteins such as heat shock 90 kDa protein 1 alpha in AD subjects has been confirmed by western blot analysis in the RBC membrane proteome.
The results suggest that this study provides a potential link between the alterations in RBC membrane proteome in AD subjects and AD pathology.