No abstract

Intracellular β-amyloid (Aβ) accumulation is an early event in Alzheimer's disease (AD) progression. Recently, it has been uncovered that presenilins (PSs), the key components of the amyloid precursor protein (APP) processing and the β-amyloid producing γ-secretase complex, are highly enriched in a special sub-compartment of the endoplasmic reticulum (ER) functionally connected to mitochondria, called mitochondria-associated ER membrane (MAM). A current hypothesis of pathogenesis of Alzheimer's diseases (AD) suggests that MAM is involved in the initial phase of AD. Since MAM supplies mitochondria with essential proteins, the increasing level of PSs and β-amyloid could lead to metabolic dysfunction because of the impairment of ER-mitochondrion crosstalk. To reveal the early molecular changes of this subcellular compartment in AD development MAM fraction was isolated from the cerebral cortex of 3 months old APP/PS1 mouse model of AD and age-matched C57BL/6 control mice, then mass spectrometry-based quantitative proteome analysis was performed. The enrichment and purity of MAM preparations were validated with EM, LC-MS/MS and protein enrichment analysis. Label-free LC-MS/MS was used to reveal the differences between the proteome of the transgenic and control mice. We obtained 77 increased and 49 decreased protein level changes in the range of - 6.365 to + 2.988, which have mitochondrial, ER or ribosomal localization according to Gene Ontology database. The highest degree of difference between the two groups was shown by the ATP-binding cassette G1 (Abcg1) which plays a crucial role in cholesterol metabolism and suppresses Aβ accumulation. Most of the other protein changes were associated with increased protein synthesis, endoplasmic-reticulum-associated protein degradation (ERAD), oxidative stress response, decreased mitochondrial protein transport and ATP production. The interaction network analysis revealed a strong relationship between the detected MAM protein changes and AD. Moreover, it explored several MAM proteins with hub position suggesting their importance in Aβ induced early MAM dysregulation. Our identified MAM protein changes precede the onset of dementia-like symptoms in the APP/PS1 model, suggesting their importance in the development of AD.

A common feature of neurodegenerative diseases is the formation of misfolded, mostly enzyme resistant proteins. These substances may form toxic assemblies according to the current concept of the neurodegenerative diseases. Overlapping of the misfolded proteins is typical in these disorders. The formation of misfolded proteins and toxic aggregates point to a common pathway of these disorders: failure in normal protein folding in the ER as a consequence of ER-stress and mitochondrial energy production. Alzheimer's disease (AD) is a rather heterogeneous, multifactorial disorder with wide clinical heterogeneity and is classified into several subtypes. In AD the processing of the amyloid precursor protein (APP) and formation of toxic β-amyloid (Aβ) structures occur intraneuronally. Aβ affects both ER and mitochondria and disturbs Ca(2+)-homeostasis of the cells. Mitochondrial dysfunction is one of the main pathological events in AD. Mitochondria accumulate Aβ derived from the ER/Golgi or from the mitochondria-associated ER-membranes (MAM). Free radicals, oxidative stress and increasing Ca(2+)-concentration in mitochondria cause decreased ATP production. Mitochondrial dynamic and trafficking are also altered as a result of Aβ toxicity. Synaptic mitochondria show a very high vulnerability. Depletion of Ca(2+) level in the ER results in dysfunction of protein folding and evokes unfolded protein response (UPR), and affects also mitochondria. MAM may play special role in the ER-mitochondria cross talk. Mitochondria themselves (using mitochondria-targeting antioxidants such as MitoQ) could be a special target for AD treatment. Another targets are the UPR cascade proteins (PERK, IRE1, ATF6) and receptors involved in Ca(2+) -level stabilization of the ER (Ryr, IP3R).

Chronic cerebral hypoperfusion (CCH) evokes mild cognitive impairment (MCI) and contributes to the progression of vascular dementia and Alzheimer's disease (AD). How CCH 2 induces these neurodegenerative processes that may spread along the synaptic network and whether they are detectable at the synaptic proteome level of the cerebral cortex remains to be established.In the present study, we report the synaptic protein changes in the cerebral cortex after stepwise bilateral common carotid artery occlusion (BCCAO) induced CCH in the rat. The occlusions were confirmed with Magnetic Resonance Angiography 5 weeks after the surgery.Synaptosome fractions were prepared using sucrose gradient centrifugation from cerebral cortex dissected 7 weeks after the occlusion. The synaptic protein differences between the sham operated and CCH groups were analysed with label free nanoUHPLC-MS/MS.

No abstract

a b s t r a c tPeripheral injection of bacterial lipopolysaccharide (LPS) facilitates 8-10 Hz spike-wave discharges (SWD) characterizing absence epilepsy in WAG/Rij rats. It is unknown however, whether peripherally administered LPS is able to alter the generator areas of epileptic activity at the molecular level. We injected 1 mg/kg dose of LPS intraperitoneally into WAG/Rij rats, recorded the body temperature and EEG, and examined the protein expression changes of the proteome 12 h after injection in the frontoparietal cortex and thalamus. We used fluorescent two-dimensional differential gel electrophoresis to investigate the expression profile. We found 16 differentially expressed proteins in the fronto-parietal cortex and 35 proteins in the thalamus. It is known that SWD genesis correlates with the transitional state of sleep-wake cycle thus we performed meta-analysis of the altered proteins in relation to inflammation, epilepsy as well as sleep. The analysis revealed that all categories are highly represented by the altered proteins and these protein-sets have considerable overlap. Protein network modeling suggested that the alterations in the proteome were largely induced by the immune response, which invokes the NFkB signaling pathway. The proteomics and computational analysis verified the known functional interplay between inflammation, epilepsy and sleep and highlighted proteins that are involved in their common synaptic mechanisms. Our physiological findings support the phenomenon that high dose of peripheral LPS injection increases SWD-number, modifies its duration as well as the sleep-wake stages and decreases body temperature.

No abstract

Alzheimer's disease (AD) is a multifactorial disease of wide clinical heterogenity. Overproduction of amyloid precursor protein (APP) and accumulation of β-amyloid (Aβ) and tau proteins are important hallmarks of AD. The identification of early pathomechanisms of AD is critically important for discovery of early diagnosis markers. Decreased brain metabolism is one of the earliest clinical symptoms of AD that indicate mitochondrial dysfunction in the brain. We performed the first comprehensive study integrating synaptic and non-synaptic mitochondrial proteome analysis (two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry) in correlation with Aβ progression in APP/PS1 mice (3, 6, and 9 months of age). We identified changes of 60 mitochondrial proteins that reflect the progressive effect of APP overproduction and Aβ accumulation on mitochondrial processes. Most of the significantly affected proteins play role in the mitochondrial electron transport chain, citric acid cycle, oxidative stress, or apoptosis. Altered expression levels of Htra2 and Ethe1, which showed parallel changes in different age groups, were confirmed also by Western blot. The common regulator bioinformatical analysis suggests the regulatory role of tumor necrosis factor (TNF) in Aβ-mediated mitochondrial protein changes. Our results are in accordance with the previous postmortem human brain proteomic studies in AD in the case of many proteins. Our results could open a new path of research aiming early mitochondrial molecular mechanisms of Aβ accumulation as a prodromal stage of human AD.