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Proteomics 03/2013; 13(6):901-903. · 4.43 Impact Factor
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ABSTRACT: Tyrosine phosphorylation plays a central role in signal transduction controlling many important biological processes. In platelets, the activity of several signaling proteins is controlled by tyrosine phosphorylation ensuring proper platelet activation and aggregation essential for regulation of the delicate balance between bleeding and hemostasis. Here, we applied SH2-profiling for deciphering of the phosphotyrosine state of human platelets activated by ADP. Applying a panel of 31 SH2-domains, rapid and complex regulation of the phosphotyrosine state of platelets was observed after ADP stimulation. Specific inhibition of platelet P2Y receptors by synthetic drugs revealed a major role for the P2Y1 receptor in tyrosine phosphorylation. Concomitant activation of protein kinase A (PKA) abolished ADP-induced tyrosine phosphorylation in a time and concentration dependent manner. Given the fact that PKA activity is negatively regulated by the P2Y12 receptor, our data provide evidence for a novel link of synergistic control of the state of tyrosine phosphorylation by both P2Y receptors. By SH2 domain pull down and MS/MS analysis, we identified distinct tyrosine phosphorylation sites in cell adhesion molecules, intracellular adapter proteins and phosphatases suggesting a major, functional role of tyrosine phosphorylation of theses candidate proteins in ADP-dependent signaling in human platelets.
Proteomics 01/2013; · 4.43 Impact Factor
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ABSTRACT: Protein profiles of developing neural circuits undergo manifold changes. The aim of this proteomic analysis was to quantify postnatal changes in two auditory brainstem areas in a comparative approach. Protein samples from the inferior colliculus (IC) and the superior olivary complex (SOC) were obtained from neonatal (P4) and young adult (P60) rats. The cytosolic fractions of both areas were examined by 2-D DIGE, and the plasma membrane-enriched fraction of the IC was analyzed via iTRAQ. iTRAQ showed a regulation in 34% of the quantified proteins. DIGE revealed 12% regulated spots in both the SOC and IC and, thus, numeric congruency. Although regulation in KEGG pathways displayed a similar pattern in both areas, only 13 of 71 regulated DIGE proteins were regulated in common, implying major area-specific differences. 89% of regulated Glycolysis / Gluconeogenesis and Citrate cycle proteins were up-regulated in the SOC or IC, suggesting a higher energy demand in adulthood. Seventeen Cytoskeleton proteins were regulated, consistent with complex morphological reorganization between P4 and P60. Fourteen were uniquely regulated in the SOC, providing further evidence for area-specific differences. Altogether, we provide the first elaborate catalog of proteins involved in auditory brainstem development, several of them possibly of particular developmental relevance.
Journal of proteomics 11/2012; · 5.07 Impact Factor
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ABSTRACT: In a time frame of a few decades, protein identification went from laborious single protein identification to automated identification of entire proteomes. This shift was enabled by the emergence of peptide-centric, gel-free analyses, in particular the so-called shotgun approaches, which not only rely on extensive experiments, but also on cutting-edge data processing methods. The present review therefore provides an overview of a shotgun proteomics identification workflow, listing the state-of-the-art methods involved and software that implement these. The authors focus on freely available tools where possible. Finally, data analysis in the context of emerging across-omics studies will also be discussed briefly, where proteomics goes beyond merely delivering a list of protein accession numbers.
Expert Review of Proteomics 10/2012; 9(5):519-32. · 3.68 Impact Factor
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ABSTRACT: The intermembrane space (IMS) represents the smallest subcompartment of mitochondria. Nevertheless, it plays important roles in transport and modification of proteins, lipids or metal ions and for the regulation and assembly of the respiratory chain complexes. Moreover it is involved in many redox processes and coordinates key steps in programmed cell death. A comprehensive profiling of IMS proteins was not performed so far. We have established a method that uses the proapoptotic protein Bax to release IMS proteins from isolated mitochondria and profiled the protein composition of this compartment. By using stable isotope-labelled mitochondria from Saccharomyces cerevisiae we were able to measure specific Bax-dependent protein release and to distinguish between quantitatively released IMS proteins and background efflux of matrix proteins. From the so far known 31 soluble IMS proteins 29 proteins were reproducibly identified corresponding to a coverage of > 90%. In addition we found 20 novel intermembrane space proteins out of which 10 have not been localized to mitochondria before. Many of these novel IMS proteins are of unknown function or have been reported to play a role in redox regulation. We confirmed IMS localization for 15 proteins using in organello import, protease accessibility upon osmotic swelling and Bax-release assays. Moreover, we identified two novel mitochondrial proteins, Ymr244c-a (Coa6) and Ybl107c (Mic23) as substrates of the MIA import pathway that have unusual cysteine motifs and found the protein phosphatase Ptc5 as a novel substrate of the inner membrane protease IMP. For Coa6 we discovered a role as a novel assembly factor of the cytochrome c oxidase complex. We present here the first and comprehensive proteome of IMS proteins of yeast mitochondria with 51 proteins in total. The IMS proteome will serve as a valuable source for further studies on the role of the IMS in cell life and death.
Molecular & Cellular Proteomics 09/2012; · 7.40 Impact Factor
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ABSTRACT: With the increasing popularity of comparative studies of complex proteomes, reporter ion-based quantification methods such as iTRAQ and TMT have become commonplace in biological studies. Their appeal derives from simple multiplexing and quantification of several samples at reasonable cost. This advantage yet comes with a known shortcoming: precursors of different species can interfere, thus reducing the quantification accuracy. Recently, two methods were brought to the community alleviating the amount of interference via novel experimental design. Before considering setting up a new workflow, tuning the system, optimizing identification and quantification rates, etc. one legitimately asks: is it really worth the effort, time and money? The question is actually not easy to answer since the interference is heavily sample and system dependent. Moreover, there was to date no method allowing the inline estimation of error rates for reporter quantification. We therefore introduce a method called iQuARI to compute false discovery rates for reporter ion based quantification experiments as easily as Target/Decoy FDR for identification. With it, the scientist can accurately estimate the amount of interference in his sample on his system and eventually consider removing shadows subsequently, a task for which reporter ion quantification might not be the solution of choice.
Journal of Proteome Research 08/2012; 11(10):5072-80. · 5.11 Impact Factor
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ABSTRACT: Antiplatelet treatment is of fundamental importance in combatting functions/dysfunction of platelets in the pathogenesis of cardiovascular and inflammatory diseases. Dysfunction of anucleate platelets is likely to be completely attributable to alterations in posttranslational modifications and protein expression. We therefore examined the proteome of platelets highly purified from fresh blood donations, using elaborate protocols to ensure negligible contamination by leukocytes, erythrocytes, and plasma. Using quantitative mass spectrometry, we created the first comprehensive and quantitative human platelet proteome, comprising almost 4000 unique proteins, estimated copy numbers for ∼ 3700 of those, and assessed intersubject (4 donors) as well as intrasubject (3 different blood samples from 1 donor) variations of the proteome. For the first time, our data allow for a systematic and weighted appraisal of protein networks and pathways in human platelets, and indicate the feasibility of differential and comprehensive proteome analyses from small blood donations. Because 85% of the platelet proteome shows no variation between healthy donors, this study represents the starting point for disease-oriented platelet proteomics. In the near future, comprehensive and quantitative comparisons between normal and well-defined dysfunctional platelets, or between platelets obtained from donors at various stages of chronic cardiovascular and inflammatory diseases will be feasible.
Blood 08/2012; 120(15):e73-82. · 9.90 Impact Factor
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ABSTRACT: IntroductionGlycosylations range among the most common posttranslational modifications with an estimated 50% of all proteins supposed
to be glycosylated. These modifications are required for essential cellular processes including cell–cell recognition, protein
structure and activity, e.g., of surface receptors, as well as subcellular localization of proteins. Beside the elucidation
of the carbohydrate structures, the annotation of glycosylation sites is of primary interest as a basis for subsequent functional
characterization. Although mass spectrometry is the method of choice for large-scale analysis of glycosylation sites, it requires
initial enrichment of glycopeptides prior mass spectrometric detection in most cases.
Materials and MethodsIn this paper, we present a novel approach for glycopeptide enrichment by electrostatic repulsion hydrophilic interaction
chromatography (ERLIC). Glycopeptides were separated from the bulk of non-modified peptides and gradually eluted from the
stationary phase with potential for isoform resolution. Applied to human platelets, 125 glycosylation sites on 66 proteins
were identified including major platelet glycoproteins responsible for cellular function.
ConclusionThese sites add a major contribution to the now more than 250 glycosylation sites annotated for platelets, which enable the
clinically relevant design of quantification assays for platelet glycoproteins.
Clinical Proteomics 04/2012; 4(1):25-36.
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ABSTRACT: Shotgun proteomic investigations rely on the algorithmic assignment of mass spectra to peptides. The quality of these matches is therefore a cornerstone in the analysis and has been the subject of numerous recent developments. In order to establish the benefits of novel algorithms, they are applied to reference samples of known content. However, these were recently shown to be either too simple to resemble typical real-life samples or as leading to results of lower accuracy as the method itself. Here, we describe how to use the proteome of Pyrococcus furiosus , a hyperthermophile, as a standard to evaluate proteomics identification workflows. Indeed, we prove that the Pyrococcus furiosus proteome provides a valid method for detecting random hits, comparable to the decoy databases currently in popular use, but we also prove that the Pyrococcus furiosus proteome goes squarely beyond the decoy approach by also providing many hundreds of highly reliable true positive hits. Searching the Pyrococcus furiosus proteome can thus be used as a unique test that provides the ability to reliably detect both false positives as well as proteome-scale true positives, allowing the rigorous testing of identification algorithms at the peptide and protein level.
Journal of Proteome Research 04/2012; 11(10):5065-71. · 5.11 Impact Factor
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ABSTRACT: Glycosylations are ubiquitous and, in many cases, essential protein modifications. Yet comprehensive and detailed analysis of glycosylations on a proteome-wide scale is a daunting and still unsolved challenge. However, a common workflow has emerged over the last decade for large-scale N-glycosylation site annotation by application of proteomic methodology. Thereby, the qualitative and quantitative assessment of hundreds or thousands of modification sites is enabled. This review presents a short overview about common enrichment techniques and glycosylation site detection for N-glycopeptides, including benefits and challenges of analysis.
Biological Chemistry 04/2012; 393(4):249-58. · 2.96 Impact Factor
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ABSTRACT: To study human cancer development, cell culture models for malignant transformation can be used. In 1999 Hahn and Coworkers introduced such a model system and established herewith a basis for research on human tumorigenesis. Primary human fibroblasts are sequentially transduced with defined genetic elements (hTERT, SV40 ER, and H-RasV12), resulting in four defined cell lines, whereby the last has a fully transformed phenotype. In order to get a deeper insight into the molecular biology of human tumorigenesis, we compared the proteomes of these four cell lines following a multimethod concept. At the beginning we assumed SILAC and sample fractionation with COFRADIC is the method of choice to analyze the cell culture model for malignant transformation. Here, the compared samples are combined before sample preparation, thus avoiding differences in sample preparation, and using COFRADIC notably reduces sample complexity. Because 2D-PAGE is a standard method for the separation and visualization of closely related proteomes, we decided to analyze and compare the proteomes of these four cell lines in a first approach by differential 2D-PAGE. Surprisingly, we discovered much more unique results with iTRAQ and sample fractionation with SCX than with the combination of 2D-PAGE and SILAC-COFRADIC. Moreover, iTRAQ outperforms the other strategies not only in number of yielded results but also in analysis time. Here, we present the iTRAQ quantification results and compare them with the results of 2D-PAGE and SILAC-COFRADIC. We found changes in the protein level at each transition. Thereby, SV40 has the strongest impact on the proteome. In detail we identified 201 regulated proteins. Beside others, these proteins are involved in cytoskeleton, RNA processing, and cell cycle, such as CDC2, hnRNPs, snRNPs, collagens, and MCM proteins. For example, MCM proteins are up-regulated and collagens are down-regulated due to SV40 ER expression. Furthermore we made the observation that proteins containing the same domain have analogous regulation profiles during malignant transformation. For instance, several proteins containing a CH or LIM domain are down-regulated. Moreover, by this study and the defined cell culture model, changes could be clearly matched to specific steps during tumorigenesis.
Journal of Proteome Research 02/2012; 11(4):2140-53. · 5.11 Impact Factor
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ABSTRACT: Quantitative proteomic analysis can help elucidating unexplored biological questions; it, however, relies on highly reproducible experiments and reliable data processing. Among the existing strategies, iTRAQ is known as an easy to use method allowing relative comparison of up to eight multiplexed samples.Once the data is acquired it is important that the final protein quantification reflects the actual amounts in the samples. Data interpretation must thus be achieved with a constant focus on quality. Here, we describe a workflow for processing iTRAQ data in user-friendly environments with emphasis on quality control.
Methods in molecular biology (Clifton, N.J.) 01/2012; 893:501-9.
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ABSTRACT: Quantitative proteomics has become a routinely used technique to globally compare protein content and expression profiles of biological samples, for instance after differential stimulation. In this context, chemical stable isotope-based labeling techniques, such as ICAT and iTRAQ, have been successfully applied in a large variety of studies. Since iTRAQ labels are isobaric, quantitation is conducted on the MS/MS level. Consequently, up to eight samples can be multiplexed and quantified in a single experiment without increasing sample complexity. Here, we present a robust workflow to conduct iTRAQ quantification of biological samples such as human platelets, which comprises (a) an adequate sample preparation procedure, (b) an optimized tryptic digestion protocol, (c) SPE desalting and subsequent peptide labeling using a 4-plex iTRAQ labeling kit, and (d) fractionation of the obtained peptide mixture by strong cation exchange chromatography.
Methods in molecular biology (Clifton, N.J.) 01/2012; 893:101-13.
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ABSTRACT: Lyme disease Borreliae are highly dependent on the uptake of nutrients provided by their hosts. Our study describes the identification of a 36 kDa protein that functions as putative dicarboxylate-specific porin in the outer membrane of Lyme disease Borrelia. The protein was purified by hydroxyapatite chromatography from Borrelia burgdorferi B31 and designated as DipA, for dicarboxylate-specific porin A. DipA was partially sequenced, and corresponding genes were identified in the genomes of B. burgdorferi B31, Borrelia garinii PBi and Borrelia afzelii PKo. DipA exhibits high homology to the Oms38 porins of relapsing fever Borreliae. B. burgdorferi DipA was characterized using the black lipid bilayer assay. The protein has a single-channel conductance of 50 pS in 1 M KCl, is slightly selective for anions with a permeability ratio for cations over anions of 0.57 in KCl and is not voltage-dependent. The channel could be partly blocked by different di- and tricarboxylic anions. Particular high stability constants up to about 28,000 l/mol (in 0.1 M KCl) were obtained among the 11 tested anions for oxaloacetate, 2-oxoglutarate and citrate. The results imply that DipA forms a porin specific for dicarboxylates which may play an important role for the uptake of specific nutrients in different Borrelia species.
PLoS ONE 01/2012; 7(5):e36523. · 4.09 Impact Factor
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Natalia Gebert,
Michael Gebert,
Silke Oeljeklaus,
Karina von der Malsburg,
David A Stroud,
Bogusz Kulawiak,
Christophe Wirth,
René P Zahedi,
Pavel Dolezal,
Sebastian Wiese, [......],
Agnes Schulze-Specking,
Kaye N Truscott, Albert Sickmann,
Peter Rehling,
Bernard Guiard,
Carola Hunte,
Bettina Warscheid,
Martin van der Laan,
Nikolaus Pfanner,
Nils Wiedemann
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ABSTRACT: The mitochondrial inner membrane harbors the complexes of the respiratory chain and translocase complexes for precursor proteins. We have identified a further subunit of the carrier translocase (TIM22 complex) that surprisingly is identical to subunit 3 of respiratory complex II, succinate dehydrogenase (Sdh3). The membrane-integral protein Sdh3 plays specific functions in electron transfer in complex II. We show by genetic and biochemical approaches that Sdh3 also plays specific functions in the TIM22 complex. Sdh3 forms a subcomplex with Tim18 and is involved in biogenesis and assembly of the membrane-integral subunits of the TIM22 complex. We conclude that the assembly of Sdh3 with different partner proteins, Sdh4 and Tim18, recruits it to two different mitochondrial membrane complexes with functions in bioenergetics and protein biogenesis, respectively.
Molecular cell 12/2011; 44(5):811-8. · 14.61 Impact Factor
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ABSTRACT: Trypsin is the most frequently used proteolytic enzyme in mass spectrometry-based proteomics. Beside its good availability, it also offers some major advantages such as an optimal average peptide length of ~14 amino acids, and typically the presence of at least two defined positive charges at the N-terminus as well as the C-terminal Arg/Lys, rendering tryptic peptides well suited for CID-based LC-MS/MS. Here, we conducted a systematic study of different types of commercially available trypsin in order to qualitatively and quantitatively compare cleavage specificity, efficiency as well as reproducibility and the potential impact on quantitation and proteome coverage. We present a straightforward strategy applied to complex digests of human platelets, comprising (1) digest controls using a monolithic column HPLC-setup, (2) SCX enrichment of semitryptic/nonspecific peptides, (3) targeted MRM analysis of corresponding full cleavage/missed cleavage peptide pairs as well as (4) LC-MS analyses of complete digests with a three-step data interpretation. Thus, differences in digest performance can be readily assessed, rendering these procedures extremely beneficial to quality control not only the trypsin of choice, but also to effectively compare as well as optimize different digestion conditions and to evaluate the reproducibility of a dedicated digest protocol for all kinds of quantitative proteome studies.
Journal of proteomics 11/2011; 75(4):1454-62. · 5.07 Impact Factor
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Thomas G P Grunewald,
Isabel Diebold,
Irene Esposito,
Stephanie Plehm,
Kristina Hauer,
Uwe Thiel,
Patricia da Silva-Buttkus,
Frauke Neff,
Rebekka Unland,
Carsten Müller-Tidow,
Colette Zobywalski,
Katharina Lohrig,
Urs Lewandrowski, Albert Sickmann,
Olivia Prazeres da Costa,
Agnes Görlach,
Andrea Cossarizza,
Elke Butt,
Günther H S Richter,
Stefan Burdach
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ABSTRACT: Ewing tumors comprise the second most common type of bone-associated cancer in children and are characterized by oncogenic EWS/FLI1 fusion proteins and early metastasis. Compelling evidence suggests that elevated levels of intracellular oxidative stress contribute to enhanced aggressiveness of numerous cancers, possibly including Ewing tumors. Using comprehensive microarray analyses and RNA interference, we identified the six-transmembrane epithelial antigen of the prostate 1 (STEAP1)-a membrane-bound mesenchymal stem cell marker of unknown function-as a highly expressed protein in Ewing tumors compared with benign tissues and show its regulation by EWS/FLI1. In addition, we show that STEAP1 knockdown reduces Ewing tumor proliferation, anchorage-independent colony formation as well as invasion in vitro and decreases growth and metastasis of Ewing tumor xenografts in vivo. Moreover, transcriptome and proteome analyses as well as functional studies revealed that STEAP1 expression correlates with oxidative stress responses and elevated levels of reactive oxygen species that in turn are able to regulate redox-sensitive and proinvasive genes. In synopsis, our data suggest that STEAP1 is associated with the invasive behavior and oxidative stress phenotype of Ewing tumors and point to a hitherto unanticipated oncogenic function of STEAP1.
Molecular Cancer Research 11/2011; 10(1):52-65. · 4.29 Impact Factor
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ABSTRACT: Eukaryotic cells contain multiple organelles, which are functionally and structurally interconnected. The endoplasmic reticulum-mitochondria encounter structure (ERMES) forms a junction between mitochondria and the endoplasmic reticulum (ER). Four ERMES proteins are known in yeast, the ER-anchored protein Mmm1 and three mitochondria-associated proteins, Mdm10, Mdm12 and Mdm34, with functions related to mitochondrial morphology and protein biogenesis. We mapped the glycosylation sites of ERMES and demonstrate that three asparagine residues in the N‑terminal domain of Mmm1 are glycosylated. While the glycosylation is dispensable, the cytosolic C‑terminal domain of Mmm1 that connects to the Mdm proteins is required for Mmm1 function. To analyze the composition of ERMES, we determined the subunits by quantitative mass spectrometry. We identified the calcium-binding GTPase Gem1 as a new ERMES subunit, revealing that ERMES is composed of five genuine subunits. Taken together, ERMES represents a platform that integrates components with functions in formation of ER-mitochondria junctions, maintenance of mitochondrial morphology, protein biogenesis and calcium binding.
Journal of Molecular Biology 09/2011; 413(4):743-50. · 4.00 Impact Factor
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ABSTRACT: The Thermo Proteome Discoverer program integrates both peptide identification and quantification into a single workflow for peptide-centric proteomics. Furthermore, its close integration with Thermo mass spectrometers has made it increasingly popular in the field. Here, we present a Java library to parse the msf files that constitute the output of Proteome Discoverer. The parser is also implemented as a graphical user interface allowing convenient access to the information found in the msf files, and in Rover, a program to analyze and validate quantitative proteomics information. All code, binaries, and documentation is freely available at http://thermo-msf-parser.googlecode.com.
Journal of Proteome Research 06/2011; 10(8):3840-3. · 5.11 Impact Factor
