Mitochondrial Proteomics: An Approach to Identify Cellular Stress Induced By Amyloid-Beta Peptide

Abstract

Mitochondria are dynamic ATP-generating organelle which contribute to many cellular functions including bioenergetic processes. intracellular calcium regulation, alteration of reduction-oxidation potential of cells, free radical scavenging, and activation of caspase-mediated celi death. Many lines of evidence suggest that mitochondria have a central role in ageing-related neurodegenerative diseases. Mitochondrial functions can be negatively affected by Amyloid Beta-peptide (ABeta), an important component in Alzheimer's disease (AD) pathogenesis, and ABeta can interact with mitochondria and cause mitochondrial dysfunction. One of the most accepted hypotheses for AD onset implicates that mitochondrial dysfunction and oxidative stress are one of the primary events in the insurgence of the pathology. To examine structural and functional mitochondrial changes in presence of Abeta, we utilized a proteomic approach by using an Orbitrap-based mass spectrometer that use a new physical principle to obtain high resolution. The Orbitrap is an advanced instrume nt for shotgun proteomics combining high-resolving power and mass accuracy that leads to higher quality datasets and reduction of false positive peptide identifications. For this aim we used neuroblastoma LAN5 cells treated without or with ABeta and submitted to cellular fractionation. Mitochondrial fractions were separated and ulilized to extract protcins to be submitted to proteomic analysis by using an LTQ-Orbitrap Velos mass spectrometer, followed by tandem mass spectra (MS/MS) examination. Proteome Discoverer platform interfaced with an in-house Mascot server was used for data analyzing and protein identification. together with database UniProtKB/Swiss-Prot. The spectral count (SpC) log ratio was used to express fold-change between different conditions. Using the program lngenuity Systems, lnc, we evidenced the involvement of some proteins in specific networks. About 500 mitochondrial proteins were identified and some of them were up- or down-regulated in the treated sample. Some of thcse proteins are involved in mitochondrial oxidative stress, bioenergetics, biogenesis, trafficking, itochondrial permeability transition pore (mPTP) formation and mitochondrial protein interaction, all mechanisms whose alteration leads to mitochondrial ysfunction.