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Postfractionation for enhanced proteomic analyses: routine electrophoretic methods increase the resolution of standard 2D-PAGE.

Here we have addressed common issues of resolution in two-dimensional polyacrylamide gel electrophoresis (2DE) experiments including proteins 'stacked' at pH extremes, unresolved peptides migrating at the front of separation, and areas of the 2D gel obscured by high abundance proteins. Postfractionation, by selective application of well-established electrophoretic separations immediately following standard 2DE, yields markedly improved resolution in these traditional problem areas using no more specialized equipment or techniques than SDS-PAGE itself.

Animals↗

Proteomics and peptidomics in neuroscience. Experience of capabilities and limitations in a neurochemical laboratory.

The increasing use of proteomics has created a basis for new strategies to develop methodologies for rapid identification of protein patterns in living organisms. It has also become evident that proteomics has other potential applications than protein and peptide identification, e.g. protein characterization, with the aim of revealing their structure, function(s) and interactions of proteins. In comparative proteomics studies, the protein expression of a certain biological system is compared with another system or the same system under perturbed conditions. Global identification of proteins in neuroscience is extremely complex, owing to the limited availability of biological material and very low concentrations of the molecules. Moreover, in addition to proteins, there are number of peptides that must also be considered in global studies on the central nervous system. In this overview, we focus on and discuss problems related to the different sources of biological material and sample handling, which are part of all preparatory and analytical steps. Straightforward protocols are desirable to avoid excessive purification steps, since loss of material at each step is inevitable. We would like to merge the two worlds of proteomics/peptidomics and neuroscience, and finally we consider different practical and technical aspects, illustrated with examples from our laboratory.

Animals↗

Defining the mitochondrial proteomes from five rat organs in a physiologically significant context using 2D blue-native/SDS-PAGE.

In accordance with their manifold tasks, various dysfunctions of mitochondria are critically involved in a large number of diseases and the aging process. This has inspired considerable efforts to identify all the mitochondrial proteins by denaturing approaches, notably, the standard gel-based method employing isoelectric focusing. Because a significant part of the mitochondrial proteome is membrane-associated and/or functions as homo- or heterooligomeric protein complexes, there is an urgent need to detect and identify mitochondrial proteins, both membranous and soluble ones, under conditions preserving protein-protein interactions. Here, we investigated mitochondria of five different rat organs (kidney, liver, heart, skeletal muscle, and brain) solubilized with digitonin, enabling the quantitative extraction of the five oxidative phosphorylation (OXPHOS) complexes. The analysis by blue-native (BN)-PAGE recovered the OXPHOS complexes to a large extent as supercomplexes and separated many other protein complexes and individual proteins which were resolved by subsequent 2D SDS-PAGE revealing the tissue-diverse mitochondrial proteomes. Using MS peptide mass fingerprinting, we identified in all five organs 92 nonredundant soluble and membrane-embedded non-OXPHOS proteins, among them, many as constituents of known mitochondrial protein complexes as well as novel ones such as the putative "stomatin-like protein 2 complex" with an apparent mass of ca. 1800 kDa. Interestingly, the identification list included 36 proteins known or presumed to be localized to nonmitochondrial compartments, for example, glycolytic enzymes, clathrin heavy chain, valosin-containing protein/p97, VoV1-ATPase, and Na,K-ATPase. We expect that more than 200 distinct non-OXPHOS proteins of digitonin-solubilized rat mitochondria separated by 2D BN/SDS-PAGE, representing a partial "protein interactome" map, can be identified.

Animals↗

Modeling the brain-pituitary-gonad axis in salmon.

To better understand the complexity of the brain-pituitary-gonad axis (BPG) in fish, we developed a biologically based pharmacodynamic model capable of accurately predicting the normal functioning of the BPG axis in salmon. This first-generation model consisted of a set of 13 equations whose formulation was guided by published values for plasma concentrations of pituitary- (FSH, LH) and ovary- (estradiol, 17alpha,20beta-dihydroxy-4-pregnene-3-one) derived hormones measured in Coho salmon over an annual spawning period. In addition, the model incorporated pertinent features of previously published mammalian models and indirect response pharmacodynamic models. Model-based equations include a description of gonadotropin releasing hormone (GnRH) synthesis and release from the hypothalamus, which is controlled by environmental variables such as photoperiod and water temperature. GnRH stimulated the biosynthesis of mRNA for FSH and LH, which were also influenced by estradiol concentration in plasma. The level of estradiol in the plasma was regulated by the oocytes, which moved along a maturation progression. Estradiol was synthesized at a basal rate and as oocytes matured, stimulation of its biosynthesis occurred. The BPG model can be integrated with toxico-genomic, -proteomic data, allowing linkage between molecular based biomarkers and reproduction in fish.

Animals↗

The application of proteomics and genomics to the study of age-related neurodegeneration and neuroprotection.

The present study aimed to acquire more information on aging-related alterations, using proteomic and genomic analyses of hippocampus from young (8 months) and old (27 months) rats. In the old rats, the proteomic analysis identified changes in proteins related to the iron-mediated oxidative stress (OS) pathway, including reduction in antioxidant enzymes (e.g., peroxiredoxin, cytochrome c oxidase) and induction of ferritin. Furthermore, the neurofilament light peptide, associated with neurodegenerative processes, was enhanced and binding/ chaperone proteins were altered in old vs. young rats. At the genes levels, significant molecular changes related to neurodegeneration were identified in aged rat hippocampus. Thus, the effects of the potent neuroprotective compounds, the anti-Parkinson drug, rasagiline and the anti-Alzheimer drug, ladostigil (1 mg/kg, for 30 days) on gene expression in the hippocampus were further investigated. Both drugs reversed the effect of aging on the expression of various mitochondrial and key regulator genes involved in neurodegeneration, cell survival, synaptogenesis, oxidation, and metabolism. These results support the hypothesis that OS and mitochondrial dysfunction may play a pivotal role in aging and age-associated neurodegenerative diseases, and can serve as potential clinical targets for future therapy.

Aging↗

Rat neuronal cells in primary culture as a model for nociceptin/orphanin FQ metabolism.

Cortical cells in primary culture contain active proteolytic enzymes capable of cleaving nociceptin/orphanin FQ (N/OFQ) and dynorphins to shorter, bioactive fragments. Cells were divided into subpopulations (neurons, astrocytes and oligodendrocytes), and the metabolic pathways in particular populations of the cells were investigated. Processing of N/OFQ and dynorphins in the cytosolic fractions differed significantly. The proposed cell model can be used for the more detailed studies on the central nervous system proteomics.

Amino Acid Sequence↗

Proteomic analysis of cerebrospinal fluid discriminates malignant and nonmalignant disease of the central nervous system and identifies specific protein markers.

CNS diseases are often accompanied by changes in the protein composition of cerebrospinal fluid (CSF). SELDI-TOF-MS provides an approach for identifying specific protein markers of disease in biological fluids. We compared the CSF proteomes from patients with neoplastic and reactive/inflammatory CNS diseases to identify potential biomarkers. SELDI-TOF-MS was performed on CSF derived from lumbar puncture of 32 patients, including 10 with CNS malignancies, 12 with inflammatory or reactive conditions, and 10 with unknown CNS disease. Using the SAX-2 (strong anionic exchange) chip, we uncovered three conserved protein peak ranges within each disease category. For neoplastic diseases, we identified conserved peaks at 7.5-8.0 kDa (9/10 samples), 15.1-15.9 kDa (8/10 samples), and 30.0-32.0 kDa (5/10 samples). In reactive/inflammatory diseases, conserved peaks were found at 6.7-7.1 kDa (10/12 samples), 11.5-11.9 kDa (12/12 samples), and 13.3-13.7 kDa (9/12 samples). A protein from the 30.0 to 32.0 kDa peak range found in neoplastic CSF was identified by MALDI analysis as carbonic anhydrase, a protein overexpressed in many malignancies including high-grade gliomas. Similarly, cystatin C was identified in the 13.3-13.7 kDa peak range in non-neoplastic CSF and was most prominent in inflammatory conditions. Our approach provides a rational basis for identifying biomarkers that could be used for detection, diagnosis, and monitoring of CNS diseases.

Adult↗

Heat shock protein 60 or 70 activates nitric-oxide synthase (NOS) I- and inhibits NOS II-associated signaling and depresses the mitochondrial apoptotic cascade during brain stem death.

The cellular and molecular basis of brain stem death remains an enigma. As the origin of a "life-and-death" signal that reflects the progression toward brain stem death, the rostral ventrolateral medulla (RVLM) is a suitable neural substrate for mechanistic delineation of this phenomenon. Here, we evaluated the hypothesis that heat shock proteins (HSPs) play a neuroprotective role in the RVLM during brain stem death and delineated the underlying mechanisms, using a clinically relevant animal model that employed the organophosphate pesticide mevinphos (Mev) as the experimental insult. In Sprague-Dawley rats, proteomic, Western blot, and real-time PCR analyses demonstrated that Mev induced de novo synthesis of HSP60 or HSP70 in the RVLM without affecting HSP90 level. Loss-of-function manipulations of HSP60 or HSP70 in the RVLM using anti-serum or antisense oligonucleotide potentiated Mev-elicited cardiovascular depression alongside reduced nitric-oxide synthase (NOS) I/protein kinase G signaling, enhanced NOS II/peroxynitrite cascade, intensified nucleosomal DNA fragmentation, elevated cytoplasmic histone-associated DNA fragments or activated caspase-3, and augmented the cytochrome c/caspase-3 cascade of apoptotic signaling in the RVLM. Co-immunoprecipitation experiments further revealed a progressive increase in the complex formed between HSP60 and mitochondrial or cytosolic Bax or mitochondrial Bcl-2 during Mev intoxication, alongside a dissociation of the cytosolic HSP60-Bcl-2 complex. We conclude that HSP60 and HSP70 confer neuroprotection against Mev intoxication by ameliorating cardiovascular depression via an anti-apoptotic action in the RVLM. The possible underlying intracellular processes include enhancing NOS I/protein kinase G signaling and inhibiting the NOS II/peroxynitrite cascade. In addition, HSP60 exerts its effects against apoptosis by blunting Mev-induced activation of the Bax/cytochrome c/caspase-3 cascade.

Animals↗

Gamma-glutamylcysteine ethyl ester protection of proteins from Abeta(1-42)-mediated oxidative stress in neuronal cell culture: a proteomics approach.

Protein oxidation mediated by amyloid beta-peptide (1-42) (Abeta[1-42]) has been proposed to play a central role in the pathogenesis of Alzheimer's disease (AD), a neurodegenerative disorder associated with aging and the loss of cognitive function. The specific mechanism by which Abeta(1-42), the primary component of the senile plaque and a pathologic hallmark of AD, contributes to the oxidative damage evident in AD brain is unknown. Moreover, the specific proteins that are vulnerable to oxidative damage induced by Abeta(1-42) are unknown. Identification of such proteins could contribute to our understanding of not only the role of Abeta(1-42) in the pathogenesis of AD, but also provide insight into the mechanisms of neurodegeneration at the protein level in AD. We report the proteomic identification of two proteins found to be oxidized significantly in neuronal cultures treated with Abeta(1-42): 14-3-3zeta and glyceraldehyde-3-phosphate dehydrogenase. We also report that pretreatment of neuronal cultures with gamma-glutamylcysteine ethyl ester, a compound that supplies the limiting substrate for the synthesis of glutathione and results in the upregulation of glutathione in neuronal cultures, protects both proteins against Abeta(1-42)-mediated protein oxidation.

Amyloid beta-Peptides↗

Identification of dynamic proteome changes upon ligand activation of Trk-receptors using two-dimensional fluorescence difference gel electrophoresis and mass spectrometry.

The TrkA and TrkB tyrosine kinases are members of the neurotrophin receptor family and mediate survival, differentiation, growth, and apoptosis of neurons in response to stimulation by their ligands, NGF and BDNF, respectively. Expression levels of TrkA/TrkB are important prognostic factors in a variety of embryonal tumors including neuroblastoma, the most common solid tumor of childhood. Because TrkA/TrkB exhibit a high level of sequence similarity and use overlapping pathways for signal transduction, the existence of specific effector molecules crucial for receptor and cell-type-specific response is likely. To identify these effectors by analyzing biological effects of TrkA and TrkB activation in a defined model, we performed a proteome study using the human neuroblastoma SY5Y cell line stably transfected with the TrkA or TrkB cDNA. The use of the recently introduced DIGE (fluorescence two-dimensional difference gel electrophoresis) system (Amersham Biosciences, Piscataway, NJ) allowed us to monitor differences in protein expression between samples in one gel. Proteomic changes were monitored in a time course of 0, 0.5, 1, 6, and 24 h following receptor activation. Using MALDI mass spectrometry, we identified, respectively, 22 and 9 differentially expressed proteins upon the addition of neurotrophin in SY5Y-TrkB and SY5Y-TrkA cells. Functional assignment revealed that the majority of these proteins are involved in organization and maintenance of cellular structures.

Brain-Derived Neurotrophic Factor↗

ERp29, a general endoplasmic reticulum marker, is highly expressed throughout the brain.

ERp29 is a recently discovered resident of the endoplasmic reticulum (ER) that is abundant in brain and most other mammalian tissues. Investigations of nonneural secretory tissues have implicated ERp29 in a major role producing export proteins, but a molecular activity remains wanting for this functional orphan. Intriguingly, ERp29 appears to be heavily utilized in the cerebellum, a brain region not conventionally regarded as neurosecretory. To elucidate this functional quandary, we used immunochemical approaches to characterize the regional, cellular, and subcellular distributions of ERp29 in rat brain. Immunohistochemistry revealed ubiquitous expression in neuronal and nonneuronal cells, with a distinctive variation in somatic ERp29 levels. Highly expressing cells were found in diverse locations, implying that ERp29 is not biased towards the cerebellum functionally. Using immunolocalization data mined from the literature, a proteomic profile was developed to assess the functional significance of ERp29's characteristic expression pattern. Surprisingly, ERp29 correlated poorly with classical markers of neurosecretion, but strongly with a variety of major membrane proteins. Together with immunogold localization of ERp29 to somatic ER, these observations led to a novel hypothesis that ERp29 is involved primarily in production of endomembrane proteins rather than proteins destined for export. This study establishes ERp29 as a general ER marker for brain cells and provides a stimulating clue about ERp29's enigmatic function. ERp29 appears to have broad significance for neural pathophysiology, given its ubiquitous distribution and prominence in brain over classical ER residents like BiP and protein disulfide isomerase.

Animals↗

Oligosaccharide microarrays for high-throughput detection and specificity assignments of carbohydrate-protein interactions.

We describe microarrays of oligosaccharides as neoglycolipids and their robust display on nitrocellulose. The arrays are obtained from glycoproteins, glycolipids, proteoglycans, polysaccharides, whole organs, or from chemically synthesized oligosaccharides. We show that carbohydrate-recognizing proteins single out their ligands not only in arrays of homogeneous oligosaccharides but also in arrays of heterogeneous oligosaccharides. Initial applications have revealed new findings, including: (i) among O-glycans in brain, a relative abundance of the Lewis(x) sequence based on N-acetyllactosamine recognized by anti-L5, and a paucity of the Lewis(x) sequence based on poly-N-acetyllactosamine recognized by anti-SSEA-1; (ii) insights into chondroitin sulfate oligosaccharides recognized by an antiserum and an antibody (CS-56) to chondroitin sulfates; and (iii) binding of the cytokine interferon-gamma (IFN-gamma) and the chemokine RANTES to sulfated sequences such as HNK-1, sulfo-Lewis(x), and sulfo-Lewis(a), in addition to glycosaminoglycans. The approach opens the way for discovering new carbohydrate-recognizing proteins in the proteome and for mapping the repertoire of carbohydrate recognition structures in the glycome.

Animals↗

Column chromatographic prefractionation leads to the detection of 543 different gene products in human fetal brain.

In a previous publication a large series of proteins were identified in fetal human brain by the use of two-dimensional electrophoresis (2-DE) with subsequent matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and MALDI-tandem time-of-flight (TOF/TOF) analysis. Further identification of many more different spots by traditional 2-DE without additional step such as narrow immobilized ph gradient (IPG) strips or prefractionation seems unlikely and we therefore decided to separate extracted brain proteins by ion-exchange chromatography using a TSK gel DEAE-5PW column followed by 2-DE of individual fractions and analysis by MALDI-TOF/TOF with LIFT technology in fetal brain of the early second trimester. About 1880 protein spots corresponding to 543 different gene products were identified. These proteins included housekeeping, signaling, cytoskeletal, metabolic, antioxidant, and neuron/synaptosomal specific proteins. Among these, 314 gene products (314/543, 57.8%), which have never been detected in traditional 2-DE of human fetal brain, were observed by this method. This updated map of fetal brain proteins may serve as data base and reference map for fetal brain proteins, and the methodology applied may be used as a valuable analytical tool for the basis of protein expressional studies in health and disease.

Brain↗

ALS phenotypes with mutations in CHMP2B (charged multivesicular body protein 2B).

Mutation in the CHMP2B gene has been implicated in frontotemporal dementia. The authors screened CHMP2B in patients with ALS and several cohorts of control samples. They identified mutations (Q206H; I29V) in two patients with non-SOD1 ALS. Neuropathology of the Q206H case showed lower motor neuron predominant disease with ubiquitylated inclusions in motor neurons. Antibodies to p62 (sequestosome 1) showed novel oligodendroglial inclusions in the motor cortex.

Adaptor Proteins, Signal Transducing↗

Proteomic identification of a novel protein regulated in CA1 and CA3 hippocampal regions during intermittent hypoxia.

The CA1 and CA3 regions of the hippocampus markedly differ in their susceptibility to hypoxia in general, and more particularly to the intermittent hypoxia (IH) that characterizes sleep apnea. We used proteomic analysis to build a database of proteins expressed in normoxic CA1 and CA3. The current hippocampus protein database identifies 106 proteins. A hypothetical protein with accession number AK006737 (gimid R:12839969) was strongly upregulated in the CA1, but not CA3 hippocampal region. Bioinformatic analysis revealed that the unknown protein contained a high stringency protein kinase e binding site. Domain analysis demonstrated the presence of a conserved sequence indicative of macrophage scavenger receptors. Using proteomic analysis we have previously demonstrated that acute (6 h) IH-mediated CA1 injury results from complex interactions between pathways involving increased metabolism, induction of stress-induced proteins and apoptosis, and ultimately disruption of structural proteins and cell integrity. The current findings identify a hypothetical protein that may play a key role in the response of CA1 to IH. These findings provide initial insights into mechanisms underlying differences in susceptibility to hypoxia in neural tissue and demonstrate how proteomic analysis can be used to generate new hypotheses, which define neuronal adaptation to IH.

Animals↗

Rapid discovery of putative protein biomarkers of traumatic brain injury by SDS-PAGE-capillary liquid chromatography-tandem mass spectrometry.

We report the rapid discovery of putative protein biomarkers of traumatic brain injury (TBI) by SDS-PAGE-capillary liquid chromatography-tandem mass spectrometry (SDS-PAGE-Capillary LC-MS(2)). Ipsilateral hippocampus (IH) samples were collected from naive rats and rats subjected to controlled cortical impact (a rodent model of TBI). Protein database searching with 15,558 uninterpreted MS(2) spectra, collected in 3 days via data-dependent capillary LC-MS(2) of pooled cyanine dye-labeled samples separated by SDS-PAGE, identified more than 306 unique proteins. Differential proteomic analysis revealed differences in protein sequence coverage for 170 mammalian proteins (57 in naive only, 74 in injured only, and 39 of 64 in both), suggesting these are putative biomarkers of TBI. Confidence in our results was obtained by the presence of several known biomarkers of TBI (including alphaII-spectrin, brain creatine kinase, and neuron-specific enolase) in our data set. These results show that SDS-PAGE prior to in vitro proteolysis and capillary LC-MS(2) is a promising strategy for the rapid discovery of putative protein biomarkers associated with a specific physiological state (i.e., TBI) without a priori knowledge of the molecules involved.

Amino Acid Sequence↗

Assessing protein patterns in disease using imaging mass spectrometry.

Direct tissue profiling and imaging mass spectrometry (MS) provides a detailed assessment of the complex protein pattern within a tissue sample. MALDI MS analysis of thin tissue sections results in over of 500 individual protein signals in the mass range of 2 to 70 kDa that directly correlate with protein composition within a specific region of the tissue sample. To date, profiling and imaging MS has been applied to multiple diseased tissues, including human gliomas and nonsmall cell lung cancer. Interrogation of the resulting complex MS data sets has resulted in identification of both disease-state and patient-prognosis specific protein patterns. These results suggest the future usefulness of proteomic information in assessing disease progression, prognosis, and drug efficacy.

Animals↗