Quantitative changes in the mitochondrial proteome from subjects with mild cognitive impairment, early stage, and late stage Alzheimer's disease

Abstract

The major barrier to treating or preventing Alzheimer's disease (AD) is its unknown etiology and pathogenesis. Although increasing evidence supports a role for mitochondrial dysfunction in the pathogenesis of AD, there have been few studies that simultaneously evaluate changes in multiple mitochondrial proteins. To evaluate changes in sites of potentially interacting mitochondrial proteins, we applied 2-dimensional liquid chromatography coupled with tandem mass spectrometry and the isotope coded affinity tag method to identify and quantify proteins in mitochondrial enriched fractions isolated from short postmortem interval temporal pole specimens from subjects with mild cognitive impairment (4 subjects pooled), early AD (4 subjects pooled), late-stage AD (8 subjects pooled) and age-matched normal control (7 subjects pooled) subjects. A total of 112 unique, non-redundant proteins were identified and quantified in common to all three stages of disease progression. Overall, patterns of protein change suggest activation of mitochondrial pathways that include proteins responsible for transport and utilization of ATP. These proteins include adenine nucleotide translocase, voltage dependent anion channels, hexokinase, and creatine kinase. Comparison of protein changes throughout the progression of AD suggests the most pronounced changes occur in early AD mitochondria.

Figure 1

A frequency distribution histogram resulting from the protein clustering algorithm showing that 21 of the 112 proteins were clustered into the HXH category.

Figure 2

Histogram plot of the log base 2 ratio data for the VDAC isoforms as a function of the three disease states, MCI, EAD and LAD.

Figure 3

Histogram plot of the log base 2 ratio data for ADT1 as a function of the three disease states, MCI, EAD and LAD.

Figure 4

Histogram plot of the log base 2 ratio data for HXK1 as a function of the three disease states, MCI, EAD and LAD.

Figure 5

Histogram plot of the log base 2 ratio data for KRCU as a function of the three disease states, MCI, EAD and LAD.

Figure 6

Histogram plot of the log base 2 ratio data for the CN37 (CNP) as a function of the three disease states, MCI, EAD and LAD showing no change in protein levels.

Figure 7

Histogram plot of the log base 2 ratio data for KRCB as a function of the three disease states, MCI, EAD and LAD showing a completely different pattern of protein change..

Figure 8

8a. Western blot images for VDACs, HXK1 and CN37 (CNP) where the first four lanes are control and the next four lanes are LAD. 8b. Histogram plots for VDACs, HXK1 and CN37 resulting from quantitative analysis of the Western blot images (expressed as percent of control).