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Proteomic identification of oxidatively modified proteins in Alzheimer's disease brain. Part I: creatine kinase BB, glutamine synthase, and ubiquitin carboxy-terminal hydrolase L-1.

Oxidative alterations of proteins by reactive oxygen species (ROS) have been implicated in the progression of aging and age-related neurodegenerative disorders such as Alzheimer's disease (AD). Protein carbonyls, a marker of protein oxidation, are increased in AD brain, indicating that oxidative modification of proteins is relevant in AD. Oxidative damage can lead to several events such as loss in specific protein function, abnormal protein clearance, depletion of the cellular redox-balance and interference with the cell cycle, and, ultimately, to neuronal death. Identification of specific targets of protein oxidation represents a crucial step in establishing a relationship between oxidative modification and neuronal death in AD, and was partially achieved previously in our laboratory through immunochemical detection of creatine kinase BB and beta-actin as specifically oxidized proteins in AD brain versus control brain. However, this process is laborious, requires the availability of specific antibodies, and, most importantly, requires a reasonable guess as to the identity of the protein in the first place. In this study, we present the first proteomics approach to identify specifically oxidized proteins in AD, by coupling 2D fingerprinting with immunological detection of carbonyls and identification of proteins by mass spectrometry. The powerful techniques, emerging from application of proteomics to neurodegenerative disease, reveal the presence of specific targets of protein oxidation in Alzheimer's disease (AD) brain: creatine kinase BB, glutamine synthase, and ubiquitin carboxy-terminal hydrolase L-1. These results are discussed with reference to potential involvement of these oxidatively modified proteins in neurodegeneration in AD brain. Proteomics offers a rapid means of identifying oxidatively modified proteins in aging and age-related neurodegenerative disorders without the limitations of the immunochemical detection method.

Alzheimer Disease↗

DeepPlaque: a scalable multimodal platform for Aβ pathology and cell analysis in Alzheimer's disease.

Histological analysis is essential for understanding disease pathology and the microenvironment, particularly in Alzheimer's disease (AD), characterized by beta-amyloid (Aβ) plaques that exist as diffuse, fibrillar, and core species, with distinct toxicity levels. However, accurate classification of Aβ plaque types in postmortem brain tissues and profiling of surrounding cells present significant challenges. To address these challenges, we developed "DeepPlaque", an integrated system featuring "PlaqueNet", a deep learning model for automated classification of Aβ plaque species from diverse imaging platforms. DeepPlaque includes automated workflows for cellular phenotyping and proteomic profiling through targeted laser microdissection. PlaqueNet achieves expert-level accuracy (AUC > 90%) in classifying the 3 major Aβ plaque species, supporting consistent and large-scale annotation. By integrating spatial cellular phenotyping with laser microdissection, DeepPlaque enables high-throughput proteomic analysis of Aβ plaque niches, revealing that microglia are more abundant around core and fibrillar Aβ plaques, with increased expression of apolipoprotein E and amyloid precursor protein in core Aβ plaques. This customizable platform enhances the molecular and cellular characterization of Aβ plaque-associated environments, providing critical insights into AD pathology.

Alzheimer Disease↗

Subcellular proteomics reveals neuromelanin granules to be a lysosome-related organelle.

The powerful combination of subcellular fractionation and protein identification by electrospray ionization tandem mass spectrometry (ESI-MS/MS) pioneered the molecular elucidation of neuromelanin (NM) granules. We recently isolated NM granules from the human brain and succeeded in the establishment of the first protein profile of this compartment. NM granules are pigmented organelles, which are mainly found in the catecholaminergic neurons of the human substantia nigra (SN) pars compacta and the locus coeruleus. These granules contain the insoluble pigment NM, which is regarded as the most important iron storage system in these neurons. A global examination of NM granules, however, has so far been hampered due to the lack of a pigmented brain stem in rodents, the absence of an appropriate experimental system and their scarcity in the human brain. 'Subcellular proteomics', which increasingly emerges as the method of choice to characterize cellular compartments and to elucidate their biogenesis, has recently been shown to be an adequate approach to tackle a thorough description of NM granules. Thereby, NM granules could be described as a 'lysosome-related organelle'. This indicates a genetic program underlying a biogenesis of NM rather than its autoxidative formation.

Cytoplasmic Granules↗

A combined stimulus of acute fasting and exercise modulates hippocampal mitochondrial quality control in healthy mice.

BACKGROUND AND AIMS: Exercise and fasting are recognized for their ability to improve brain health and mitigate neurodegeneration. However, little is known about how these interventions acutely impact mitochondrial quality control mechanisms including mitophagy. METHODS: We examined the effects of a single bout of fasting and exercise (FEx) on hippocampal mitochondrial function and proteomic remodeling in male and female mice. To assess in vivo autophagy dynamics, we combined proteomics with chloroquine (CQ) inhibition of autophagic flux. Mice were assigned to sedentary (Sed), fasting (F), exercise (Ex), or combined FEx groups and received unilateral intrahippocampal injections of CQ or PBS following treatments. Four hours later, hippocampi were collected for analysis. RESULTS: LC3-II levels significantly increased in the FEx group only following CQ treatment, indicating enhanced autophagic flux. Proteomic profiling showed sedentary males failed to mount a robust response to FEx however females exhibited upregulation of proteins involved in the TCA cycle, glutathione metabolism, and oxidative phosphorylation, suggesting greater mitochondrial adaptability. Functional assays supported these findings, females showed increased complex IV activity post-FEx. The mitochondrial DNA / nuclear DNA ratio increased after FEx regardless of sex, and upstream regulator analysis predicted activation of mitochondrial biogenesis. CONCLUSIONS: Together, these data reveal sex-specific mitochondrial remodeling in response to acute fasting and exercise. Defining these normative responses is critical for understanding how mitochondrial adaptability shapes resilience or vulnerability to neurological challenges.

Animals↗

Proteomics: a new approach to investigate oxidative stress in Alzheimer's disease brain.

In Alzheimer's disease (AD) brain oxidative stress is observed indexed by several markers, among which are protein carbonyls and 3-nitrotyrosine, markers for protein oxidation. We hypothesized that identity of these oxidatively modified proteins would lead to greater understanding of some of the potential molecular mechanisms involved in neurodegeneration in this dementing disorder. Proteomics is an emerging method for identification of proteins, and its application to neurodegenerative disorders, especially AD, is just beginning. Posttranslational modification of brain proteins, particularly that due of oxidation of proteins, provides an effective means of screening a subset of proteins within the brain proteome that likely reflects the extensive oxidative stress under which the AD brain exists, and this new methodology provides insights into mechanisms of neurodegeneration in and new therapeutic targets for AD. In this review, the use of proteomics to identify specifically oxidized proteins in AD brain is presented, from which new insights into mechanisms of neurodegeneration and synapse loss in this dementing disorder that is associated with oxidative stress have emerged.

Alzheimer Disease↗

Enhanced detergent extraction for analysis of membrane proteomes by two-dimensional gel electrophoresis.

BACKGROUND: The analysis of hydrophobic membrane proteins by two-dimensional gel electrophoresis has long been hampered by the concept of inherent difficulty due to solubility issues. We have optimized extraction protocols by varying the detergent composition of the solubilization buffer with a variety of commercially available non-ionic and zwitterionic detergents and detergent-like phospholipids. RESULTS: After initial analyses by one-dimensional SDS-PAGE, quantitative two-dimensional analyses of human erythrocyte membranes, mouse liver membranes, and mouse brain membranes, extracted with buffers that included the zwitterionic detergent MEGA 10 (decanoyl-N-methylglucamide) and the zwitterionic lipid LPC (1-lauroyl lysophosphatidylcholine), showed selective improvement over extraction with the common 2-DE detergent CHAPS (3 [(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate). Mixtures of the three detergents showed additive improvements in spot number, density, and resolution. Substantial improvements in the analysis of a brain membrane proteome were observed. CONCLUSION: This study demonstrates that an optimized detergent mix, coupled with rigorous sample handling and electrophoretic protocols, enables simple and effective analysis of membrane proteomes using two-dimensional electrophoresis.

Journal Article↗

cDNA microarray and proteomic approaches in the study of brain diseases: focus on schizophrenia and Alzheimer's disease.

Recent advances in experimental genomics and proteomics, coupled with the wealth of sequence information available for a variety of organisms, have tremendous implications for how biomedical research is performed. Genomic techniques, such as complementary DNA (cDNA) microarrays, currently allow researchers to quickly and accurately quantify vast numbers of potential gene expression changes simultaneously. Modern proteomic techniques allow for the detection and elucidation of protein-protein interactions on a scale and at a speed never before possible. Although hurdles remain, together, these tools open the possibility of enormous change in our ability to analyze and interpret complex biological processes. The field of neuroscience is particularly well suited to analysis with these new techniques, given the complexity of neuronal signaling and the diversity of cellular responses. This review summarizes the major cDNA microarray and proteomic findings of relevance to schizophrenia and Alzheimer's disease (AD) as 2 representative areas of neuroscience research. The potential for these techniques to help unravel the underlying pathology of complex neurological and neuropsychiatric conditions is considerable and warrants continued investigation.

Alzheimer Disease↗

Amyloid beta-peptide (1-42)-induced oxidative stress and neurotoxicity: implications for neurodegeneration in Alzheimer's disease brain. A review.

Oxidative stress, manifested by protein oxidation, lipid peroxidation, DNA oxidation and 3-nitrotyrosine formation, among other indices, is observed in Alzheimer's disease (AD) brain. Amyloid beta-peptide (1-42) [Abeta(1-42)] may be central to the pathogenesis of AD. Our laboratory and others have implicated Abeta(1-42)-induced free radical oxidative stress in the neurodegeneration observed in AD brain. This paper reviews some of these studies from our laboratory. Recently, we showed both in-vitro and in-vivo that methionine residue 35 (Met-35) of Abeta(1-42) was critical to its oxidative stress and neurotoxic properties. Because the C-terminal region of Abeta(1-42) is helical, and invoking the i + 4 rule of helices, we hypothesized that the carboxyl oxygen of lle-31, known to be within a van der Waals distance of the S atom of Met-35, would interact with the latter. This interaction could alter the susceptibility for oxidation of Met-35, i.e. free radical formation. Consistent with this hypothesis, substitution of lle-31 by the helix-breaking amino acid, proline, completely abrogated the oxidative stress and neurotoxic properties of Abeta(1-42). Removal of the Met-35 residue from the lipid bilayer by substitution of the negatively charged Asp for Gly-37 abrogated oxidative stress and neurotoxic properties of Abeta(1-42). The free radical scavenger vitamin E prevented A(beta (1-42)-induced ROS formation, protein oxidation, lipid peroxidation, and neurotoxicity in hippocampal neurons, consistent with our model for Abeta-associated free radical oxidative stress induced neurodegeneration in AD. ApoE, allele 4, is a risk factor for AD. Synaptosomes from apoE knock-out mice are more vulnerable to Abeta-induced oxidative stress (protein oxidation, lipid peroxidation, and ROS generation) than are those from wild-type mice. We also studied synaptosomes from allele-specific human apoE knock-in mice. Brain membranes from human apoE4 mice have greater vulnerability to Abeta(1-42)-induced oxidative stress than brain membranes from apoE2 or E3, assessed by the same indices, consistent with the notion of a coupling of the oxidative environment in AD brain and increased risk of developing this disorder. Using immunoprecipitation of proteins from AD and control brain obtained no longer than 4h PMI, selective oxidized proteins were identified in the AD brain. Creatine kinase (CK) and beta-actin have increased carbonyl groups, an index of protein oxidation, and Glt-1, the principal glutamate transporter, has increased binding of the lipid peroxidation product, 4-hydroxy-2-nonenal (HNE). Abeta inhibits CK and causes lipid peroxidation, leading to HNE formation. Implications of these findings relate to decreased energy utilization, altered assembly of cytoskeletal proteins, and increased excitotoxicity to neurons by glutamate, all reported for AD. Other oxidatively modified proteins have been identified in AD brain by proteomics analysis, and these oxidatively-modified proteins may be related to increased excitotoxicity (glutamine synthetase), aberrant proteasomal degradation of damaged or aggregated proteins (ubiquitin C-terminal hydrolase L-1), altered energy production (alpha-enolase), and diminished growth cone elongation and directionality (dihydropyrimindase-related protein 2). Taken together, these studies outlined above suggest that Met-35 is key to the oxidative stress and neurotoxic properties of Abeta(1-42) and may help explain the apoE allele dependence on risk for AD, some of the functional and structural alterations in AD brain, and strongly support a causative role of Abeta(1-42)-induced oxidative stress and neurodegeneration in AD.

Alzheimer Disease↗

Integrated analysis of amide proton transfer weighted MRI and proteomics uncovers altered protein dynamics in glioblastoma.

PURPOSE: Elevated amide proton transfer-weighted (APTw) MRI signals in glioblastoma (GBM) are often linked to increased intracellular mobile proteins, but the associated molecular patterns in human tissue remain unclear. We examined the relationship between regional APTw features and cellular protein composition and profiled proteomic differences between tumor and peritumoral tissue. METHODS: In this single-center prospective study, preoperative MRI data were integrated with intraoperative neuronavigation for 12 image-guided tissue samples (8 tumor and 4 peritumoral). Total, cytoplasmic, and nuclear proteins were quantified using bicinchoninic acid (BCA) assay. Data-independent acquisition (DIA) proteomics identified exploratory differentially expressed proteins (DEPs), followed by functional enrichment and protein-protein interaction (PPI) network analyses. Transcript-level expression patterns and survival associations were queried in The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) datasets to provide indirect external clinical context. RESULTS: Tumor regions showed higher APTw signals than peritumoral regions (p&#x2009;<&#x2009;0.001) and increased cytoplasmic protein concentration (p&#x2009;<&#x2009;0.05), without a corresponding increase in total or nuclear protein levels. DIA identified 654 DEPs. Further analysis highlighted 36 higher-significance DEPs, and prioritized 12 hub proteins in the PPI network. In public transcriptomic datasets, ERBB2, RUNX1, and SHC1 showed higher expression in GBM and were associated with poorer overall survival. CONCLUSION: These findings suggest that elevated APTw signal in GBM may be associated with increased cytoplasmic protein content and distinct proteomic alterations. This imaging-proteomic framework provides exploratory regional context for future mechanistic and follow-up studies, but larger, spatially matched and independently validated cohorts are required to confirm the molecular contributors to APTw contrast.

Humans↗

Longitudinal multi-omics in alpha-synuclein Drosophila model discriminates disease- from age-associated pathologies in Parkinson's disease.

Parkinson's disease (PD) starts decades before symptoms appear, usually in the later decades of life, when age-related changes are occurring. To identify molecular changes early in the disease course and distinguish PD pathologies from aging, we generated Drosophila expressing alpha-synuclein (&#x3b1;Syn) in neurons and performed longitudinal bulk transcriptomics and proteomics on brains at six time points across the lifespan and compared the data to healthy control flies as well as human post-mortem brain datasets. We found that translational and energy metabolism pathways were downregulated in &#x3b1;Syn flies at the earliest timepoints; comparison with the aged control flies suggests that elevated &#x3b1;Syn accelerates changes associated with normal aging. Unexpectedly, single-cell analysis at a mid-disease stage revealed that neurons upregulate protein synthesis and nonsense-mediated decay, while glia drive their overall downregulation. Longitudinal multi-omics approaches in animal models can thus help elucidate the molecular cascades underlying neurodegeneration vs. aging and co-pathologies.

Journal Article↗

Optimization and evaluation of surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry for protein profiling of cerebrospinal fluid.

Cerebrospinal fluid (CSF) potentially carries an archive of peptides and small proteins relevant to pathological processes in the central nervous system (CNS) and surrounding brain tissue. Proteomics is especially well suited for the discovery of biomarkers of diagnostic potential in CSF for early diagnosis and discrimination of several neurodegenerative diseases. ProteinChip surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) is one such approach which offers a unique platform for high throughput profiling of peptides and small proteins in CSF. In this study, we evaluated methodologies for the retention of CSF proteins < 20 kDa in size, and identify a strategy for screening small proteins and peptides in CSF. ProteinChip array types, along with sample and binding buffer conditions, and matrices were investigated. By coupling the processing of arrays to a liquid handler reproducible and reliable profiles, with mean peak coefficients of variation < 20%, were achieved for intra- and inter-assays under selected conditions. Based on peak m/z we found a high degree of overlap between the tested array surfaces. The combination of CM10 and IMAC30 arrays was sufficient to represent between 80-90% of all assigned peaks when using either sinapinic acid or alpha-Cyano-4-hydroxycinnamic acid as the energy absorbing matrices. Moreover, arrays processed with SPA consistently showed better peak resolution and higher peak number across all surfaces within the measured mass range. We intend to use CM10 and IMAC30 arrays prepared in sinapinic acid as a fast and cost-effective approach to drive decisions on sample selection prior to more in-depth discovery of diagnostic biomarkers in CSF using alternative but complementary proteomic strategies.

Journal Article↗

Pharmacology of valproate.

Valproate has been in clinical use for nearly 40 years for the treatment of a variety of neuropsychiatric illnesses, including bipolar disorder and epilepsy. Early reports linked its biochemical mechanism of action to alterations in gamma-aminobutyric acid (GABA)-ergic function. The definitive mechanism(s) mediating the clinical efficacy of this relatively simple molecule remain obscure. Although valproate does not directly interact with postsynaptic GABA receptors, it does increase regional neuronal concentrations of GABA by both inhibiting its metabolism and increasing its synthesis. The relevance of these effects to the clinical efficacy of valproate is unclear. Results of preclinical research, largely in rodents, have implicated ion channels, monoamines, corticotropin-releasing factor, and intracellular signaling proteins in the mechanism of action of valproate. This relative dearth of data in the area of valproate neuropharmacology is also evident when discussing the mechanism( s) of action of other mood stabilizers and anticonvulsants. Modern tools of basic and clinical neuroscience (eg, genomics, proteomics, functional brain imaging) will rapidly provide valuable insights into the precise mechanism(s) of action of valproate.

Animals↗

Proteome studies of human cerebrospinal fluid and brain tissue using a preparative two-dimensional electrophoresis approach prior to mass spectrometry.

A preparative proteomic approach, involving liquid phase isoelectric focusing (IEF) in combination with one-dimensional electrophoresis and electroelution followed by mass spectrometry and database searches, was found to be an important tool for identifying low-abundant proteins (microgram/L) in human cerebrospinal fluid (CSF) and membrane proteins in human frontal cortex. Several neuron-related proteins, such as amyloid precursor-like protein, chromogranins A and B, glial fibrillary acid protein, beta-trace, transthyretin, ubiquitin, and cystatin C, were identified in CSF. Several types of proteins were also characterized from a detergent-solubilized human frontal cortex homogenate including membrane proteins such as synaptophysin, syntaxin and Na+/K+ ATPase. One-third of the identified proteins have not previously been identified in human CSF or human frontal cortex using proteomic techniques. The absence of these proteins in two-dimensional electrophoresis maps might be due to insufficient amounts or low solubility. The advantages of using preparative liquid phase electrophoretic separations for identifying proteins from complex biological mixtures are speed of analysis, high loadability in the IEF separation, nondiscrimination of membrane proteins or low abundance proteins, yielding sufficient amounts for characterization by mass spectrometry. The use of this strategy in proteome studies of CSF/brain tissue is expected to offer new perspectives in studies of the pathology of neurodegenerative diseases, and reveal new potential markers for brain disorders.

Brain Chemistry↗

Proteomic studies on the white matter of human brain.

Limited information on the protein expression profiles of the different components of mammalian brain is available to date. In the present study, proteomic analysis was performed on 32 white matter samples obtained from 8 different regions of brains of four post mortem cases. Proteins were separated by 2D gel electrophoresis and identified by mass spectrometry. Most of the protein spots (98%) are reproducibly present in all the samples analyzed. A total of 64 different proteins were identified and divided into seven functional groups. These include metabolic proteins (33%), structural proteins (9%), proteins involved in signal transduction (9%), blood proteins (8%), stress related proteins (23%), and proteins involved in the ubiquitin mediated proteolysis (6%). This protein database obtained from the white matter of human brain contributes to deepen our knowledge on the molecular mechanisms that control several pathologies affecting this key component of the brain.

Brain↗

From the genome to the proteome: uncovering peptides in the Apis brain.

Neuropeptides, critical brain peptides that modulate animal behavior by affecting the activity of almost every neuronal circuit, are inherently difficult to predict directly from a nascent genome sequence because of extensive posttranslational processing. The combination of bioinformatics and proteomics allows unprecedented neuropeptide discovery from an unannotated genome. Within the Apis mellifera genome, we have inferred more than 200 neuropeptides and have confirmed the sequences of 100 peptides. This study lays the groundwork for future molecular studies of Apis neuropeptides with the identification of 36 genes, 33 of which were previously unreported.

Algorithms↗

Proteomic identification of biomarkers of traumatic brain injury.

Traumatic brain injury (TBI) is a major national health problem without a US Food and Drug Administration-approved therapy. This review summarizes the importance of discovering relevant TBI protein biomarkers and presents logical rationale that neuroproteomic technologies are uniquely suited for the discovery of otherwise unnoticed TBI biomarkers. It highlights that one must make careful decisions when choosing which paradigm (human vs. animal models) and which biologic samples to use for such proteomic studies. It further outlines some of the desirable attributes of an ideal TBI biomarker and discusses how biomarkers discovered proteomically are complementary to those identified by traditional approaches. Lastly, the most important sequela of any proteomically identified TBI biomarker is validation in preclinical or clinical samples.

Animals↗

Proteomic analysis identifies alterations in cellular morphology and cell death pathways in mouse brain after chronic corticosterone treatment.

Some patients with Major Depression and other neurological afflictions display hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. HPA hyperactivity may be due to impaired feedback inhibition and manifested as increased levels of circulating cortisol. Subcutaneous implants of corticosterone pellets were used to mimic this situation in mice to gain insight into any effects on brain function by comparative proteomic analysis using two-dimensional Differential In-Gel Electrophoresis. A total of 150 different protein spots were altered by corticosterone treatment in the hypothalamus, hippocampus and cerebral cortex. Of these, 117 spots were identified by matrix-assisted laser desorption/ionization-time of flight mass fingerprinting equating to 51 different proteins. Association of these corticosterone-modulated proteins with biological functions using the Ingenuity Pathways Analysis tool showed that cell morphology was significantly altered in the hippocampus and cerebral cortex, whereas the hypothalamus showed significant changes in cell death. Ingenuity Pathways Analysis of the canonical signaling pathways showed that glycolysis and gluconeogenesis were altered in the hypothalamus and the hippocampus and all three brain regions showed changes in phenylalanine, glutamate and nitrogen metabolism. Further elucidation of these pathways could lead to identification of biomarkers for the development of pharmacological therapies targeted at neuropsychiatric disorders.

Animals↗

Proteomics for the identification of specifically oxidized proteins in brain: technology and application to the study of neurodegenerative disorders.

Proteomics offers the opportunity elucidate the complex protein interactions of cellular systems by studying the products of genes, i.e., proteins, and their structure, function and localization. The purpose of proteomics is to explain the information contained in the genome sequences in order to provide clues on cellular events, especially related to disease. Our proteomic approach has made possible the identification of specifically oxidized proteins in Alzheimer's disease (AD) brain, providing for the first time evidence on how oxidative stress plays a crucial role in AD-related neurodegeneration. This represents an example of the use of proteomics to solve biological problems related to disease. The field, which is still in its infancy, represents a very promising way to elucidate mechanism of disease at a protein level. However, the techniques that support its development present several limitations and require introduction of new tools and innovation in order to achieve a fast, reliable and sensitive method to understand normal biological processes and their regulation as well as these cellular properties in disease.

Alzheimer Disease↗