| 1. |
- Ahmad, Yasmeen, et al.
(författare)
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Systematic Analysis of Protein Pools, Isoforms, and Modifications Affecting Turnover and Subcellular Localization
- 2012
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- In higher eukaryotes many genes encode protein isoforms whose properties and biological roles are often poorly characterized. Here we describe systematic approaches for detection of either distinct isoforms, or separate pools of the same isoform, with differential biological properties. Using information from ion intensities we have estimated protein abundance levels and using rates of change in stable isotope labeling with amino acids in cell culture isotope ratios we measured turnover rates and subcellular distribution for the HeLa cell proteome. Protein isoforms were detected using three data analysis strategies that evaluate differences between stable isotope labeling with amino acids in cell culture isotope ratios for specific groups of peptides within the total set of peptides assigned to a protein. The candidate approach compares stable isotope labeling with amino acids in cell culture isotope ratios for predicted isoform- specific peptides, with ratio values for peptides shared by all the isoforms. The rule of thirds approach compares the mean isotope ratio values for all peptides in each of three equal segments along the linear length of the protein, assessing differences between segment values. The three in a row approach compares mean isotope ratio values for each sequential group of three adjacent peptides, assessing differences with the mean value for all peptides assigned to the protein. Protein isoforms were also detected and their properties evaluated by fractionating cell extracts on one- dimensional SDS- PAGE prior to trypsin digestion and MS analysis and independently evaluating isotope ratio values for the same peptides isolated from different gel slices. The effect of protein phosphorylation on turnover rates was analyzed by comparing mean turnover values calculated for all peptides assigned to a protein, either including, or excluding, values for cognate phosphopeptides. Collectively, these experimental and analytical approaches provide a framework for expanding the func- tional annotation of the genome.
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| 2. |
- Barbe, Laurent, et al.
(författare)
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Toward a confocal subcellular atlas of the human proteome
- 2008
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Ingår i: Molecular and cellular proteomics. - 1535-9476 .- 1535-9484. ; 7:3, s. 499-508
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Tidskriftsartikel (refereegranskat)abstract
- Information on protein localization on the subcellular level is important to map and characterize the proteome and to better understand cellular functions of proteins. Here we report on a pilot study of 466 proteins in three human cell lines aimed to allow large scale confocal microscopy analysis using protein-specific antibodies. Approximately 3000 high resolution images were generated, and more than 80% of the analyzed proteins could be classified in one or multiple subcellular compartment(s). The localizations of the proteins showed, in many cases, good agreement with the Gene Ontology localization prediction model. This is the first large scale antibody-based study to localize proteins into subcellular compartments using antibodies and confocal microscopy. The results suggest that this approach might be a valuable tool in conjunction with predictive models for protein localization.
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| 3. |
- Berglund, Lisa, et al.
(författare)
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A genecentric Human Protein Atlas for expression profiles based on antibodies
- 2008
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 7:10, s. 2019-2027
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Forskningsöversikt (refereegranskat)abstract
- An attractive path forward in proteomics is to experimentally annotate the human protein complement of the genome in a genecentric manner. Using antibodies, it might be possible to design protein-specific probes for a representative protein from every protein-coding gene and to subsequently use the antibodies for systematical analysis of cellular distribution and subcellular localization of proteins in normal and disease tissues. A new version (4.0) of the Human Protein Atlas has been developed in a genecentric manner with the inclusion of all human genes and splice variants predicted from genome efforts together with a visualization of each protein with characteristics such as predicted membrane regions, signal peptide, and protein domains and new plots showing the uniqueness (sequence similarity) of every fraction of each protein toward all other human proteins. The new version is based on tissue profiles generated from 6120 antibodies with more than five million immunohistochemistry-based images covering 5067 human genes, corresponding to approximately 25% of the human genome. Version 4.0 includes a putative list of members in various protein classes, both functional classes, such as kinases, transcription factors, G-protein-coupled receptors, etc., and project-related classes, such as candidate genes for cancer or cardiovascular diseases. The exact antigen sequence for the internally generated antibodies has also been released together with a visualization of the application-specific validation performed for each antibody, including a protein array assay, Western blot analysis, immunohistochemistry, and, for a large fraction, immunofluorescence-based confocal microscopy. New search functionalities have been added to allow complex queries regarding protein expression profiles, protein classes, and chromosome location. The new version of the protein atlas thus is a resource for many areas of biomedical research, including protein science and biomarker discovery.
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| 4. |
- Burnum-Johnson, Kristin E., et al.
(författare)
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New Views of Old Proteins : Clarifying the Enigmatic Proteome
- 2022
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Ingår i: Molecular & Cellular Proteomics. - : Elsevier BV. - 1535-9476 .- 1535-9484. ; 21:7
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Tidskriftsartikel (refereegranskat)abstract
- All human diseases involve proteins, yet our current tools to characterize and quantify them are limited. To better elucidate proteins across space, time, and molecular composition, we provide a >10 years of projection for technologies to meet the challenges that protein biology presents. With a broad perspective, we discuss grand opportunities to transition the science of proteomics into a more propulsive enterprise. Extrapolating recent trends, we describe a next generation of approaches to define, quantify, and visualize the multiple dimensions of the proteome, thereby transforming our understanding and interactions with human disease in the coming decade.
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| 5. |
- Dengjel, Joern, et al.
(författare)
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Identification of Autophagosome-associated Proteins and Regulators by Quantitative Proteomic Analysis and Genetic Screens
- 2012
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Autophagy is one of the major intracellular catabolic pathways, but little is known about the composition of autophagosomes. To study the associated proteins, we isolated autophagosomes from human breast cancer cells using two different biochemical methods and three stimulus types: amino acid deprivation or rapamycin or concanamycin A treatment. The autophagosome- associated proteins were dependent on stimulus, but a core set of proteins was stimulus- independent. Remarkably, proteasomal proteins were abundant among the stimulus- independent common autophagosome- associated proteins, and the activation of autophagy significantly decreased the cellular proteasome level and activity supporting interplay between the two degradation pathways. A screen of yeast strains defective in the orthologs of the human genes encoding for a common set of autophagosome- associated proteins revealed several regulators of autophagy, including subunits of the retromer complex. The combined spatiotemporal proteomic and genetic data sets presented here provide a basis for further characterization of autophagosome biogenesis and cargo selection.
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| 6. |
- Edfors, Fredrik, et al.
(författare)
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Immunoproteomics using polyclonal antibodies and stable isotope-labeled affinity-purified recombinant proteins
- 2014
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 13:6, s. 1611-1624
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Tidskriftsartikel (refereegranskat)abstract
- AThe combination of immuno-based methods and mass spectrometry detection has great potential in the field of quantitative proteomics. Here, we describe a new method (immuno-SILAC) for the absolute quantification of proteins in complex samples based on polyclonal antibodies and stable isotope-labeled recombinant protein fragments to allow affinity enrichment prior to mass spectrometry analysis and accurate quantification. We took advantage of the antibody resources publicly available from the Human Protein Atlas project covering more than 80% of all human protein-coding genes. Epitope mapping revealed that a majority of the polyclonal antibodies recognized multiple linear epitopes, and based on these results, a semi-automated method was developed for peptide enrichment using polyclonal antibodies immobilized on protein A-coated magnetic beads. A protocol based on the simultaneous multiplex capture of more than 40 protein targets showed that approximately half of the antibodies enriched at least one functional peptide detected in the subsequent mass spectrometry analysis. The approach was further developed to also generate quantitative data via the addition of heavy isotope-labeled recombinant protein fragment standards prior to trypsin digestion. Here, we show that we were able to use small amounts of antibodies (50 ng per target) in this manner for efficient multiplex analysis of quantitative levels of proteins in a human HeLa cell lysate. The results suggest that polyclonal antibodies generated via immunization of recombinant protein fragments could be used for the enrichment of target peptides to allow for rapid mass spectrometry analysis taking advantage of a substantial reduction in sample complexity. The possibility of building up a proteome-wide resource for immuno-SILAC assays based on publicly available antibody resources is discussed.
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| 7. |
- Larance, Mark, et al.
(författare)
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Characterization of MRFAP1 Turnover and Interactions Downstream of the NEDD8 Pathway
- 2012
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- The NEDD8-Cullin E3 ligase pathway plays an important role in protein homeostasis, in particular the degradation of cell cycle regulators and transcriptional control networks. To characterize NEDD8-cullin target proteins, we performed a quantitative proteomic analysis of cells treated with MLN4924, a small molecule inhibitor of the NEDD8 conjugation pathway. MRFAP1 and its interaction partner, MORF4L1, were among the most up-regulated proteins after NEDD8 inhibition in multiple human cell lines. We show that MRFAP1 has a fast turnover rate in the absence of MLN4924 and is degraded via the ubiquitin- proteasome system. The increased abundance of MRFAP1 after MLN4924 treatment results from a decreased rate of degradation. Characterization of the binding partners of both MRFAP1 and MORF4L1 revealed a complex protein-protein interaction network. MRFAP1 bound to a number of E3 ubiquitin ligases, including CUL4B, but not to components of the NuA4 complex, including MRGBP, which bound to MORF4L1. These data indicate that MRFAP1 may regulate the ability of MORF4L1 to interact with chromatin-modifying enzymes by binding to MORF4L1 in a mutually exclusive manner with MRGBP. Analysis of MRFAP1 expression in human tissues by immunostaining with a MRFAP1-specific antibody revealed that it was detectable in only a small number of tissues, in particular testis and brain. Strikingly, analysis of the seminiferous tubules of the testis showed the highest nuclear staining in the spermatogonia and much weaker staining in the spermatocytes and spermatids. MRGBP was inversely correlated with MRFAP1 expression in these cell types, consistent with an exchange of MORF4L1 interaction partners as cells progress through meiosis in the testis. These data highlight an important new arm of the NEDD8cullin pathway.
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| 8. |
- Uhlén, Mathias, et al.
(författare)
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Antibody-based Protein Profiling of the Human Chromosome 21
- 2012
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- The Human Proteome Project has been proposed to create a knowledge-based resource based on a systematical mapping of all human proteins, chromosome by chromosome, in a gene-centric manner. With this background, we here describe the systematic analysis of chromosome 21 using an antibody-based approach for protein profiling using both confocal microscopy and immunohistochemistry, complemented with transcript profiling using next generation sequencing data. We also describe a new approach for protein isoform analysis using a combination of antibody-based probing and isoelectric focusing. The analysis has identified several genes on chromosome 21 with no previous evidence on the protein level, and the isoform analysis indicates that a large fraction of human proteins have multiple isoforms. A chromosome-wide matrix is presented with status for all chromosome 21 genes regarding subcellular localization, tissue distribution, and molecular characterization of the corresponding proteins. The path to generate a chromosome-specific resource, including integrated data from complementary assay platforms, such as mass spectrometry and gene tagging analysis, is discussed.
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| 9. |
- Zeiler, Marlis, et al.
(författare)
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A Protein Epitope Signature Tag (PrEST) Library Allows SILAC-based Absolute Quantification and Multiplexed Determination of Protein Copy Numbers in Cell Lines
- 2012
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometry-based proteomics increasingly relies on relative or absolute quantification. In relative quantification, stable isotope based methods often allow mixing at early stages of sample preparation, whereas for absolute quantification this has generally required recombinant expression of full length, labeled protein standards. Here we make use of a very large library of Protein Epitope Signature Tags (PrESTs) that has been developed in the course of the Human Protein Atlas Project. These PrESTs are expressed recombinantly in E. coli and they consist of a short and unique region of the protein of interest as well as purification and solubility tags. We first quantify a highly purified, stable isotope labeling of amino acids in cell culture (SILAC)-labeled version of the solubility tag and use it determine the precise amount of each PrEST by its SILAC ratios. The PrESTs are then spiked into cell lysates and the SILAC ratios of PrEST peptides to peptides from endogenous target proteins yield their cellular quantities. The procedure can readily be multiplexed, as we demonstrate by simultaneously determining the copy number of 40 proteins in HeLa cells. Among the proteins analyzed, the cytoskeletal protein vimentin was found to be most abundant with 20 million copies per cell, while the transcription factor and oncogene FOS only had 6000 copies. Direct quantification of the absolute amount of single proteins is possible via a SILAC experiment in which labeled cell lysate is mixed both with the heavy labeled solubility tag and with the corresponding PrEST. The SILAC-PrEST combination allows accurate and streamlined quantification of the absolute or relative amount of proteins of interest in a wide variety of applications.
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