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Combination of two-dimensional electrophoresis and shotgun peptide sequencing in comparative proteomics.

Two-dimensional electrophoresis (2-DE) and shotgun peptide sequencing are the two major technologies to compare the expression profile of proteins, which is also referred to as comparative proteomics or quantitative proteomics. Although the methodologies, such as difference gel electrophoresis for 2-DE and isotope-coded affinity tags for shotgun peptide sequencing, have made rapid progress, these two approaches have their own strengths and weaknesses. Therefore, the combination of the two methodologies is beneficial for the purpose of better comparative proteomics, especially in comprehensive coverage of the proteome and protein information such as post-translational modifications.

Animals↗

Microarray-based functional protein profiling using peptide nucleic acid-encoded libraries.

The availability of complete genome sequences from numerous organisms has provided investigators with the challenge of assigning physiologic functions to the encoded gene products. To facilitate this process, multiple technologies have been developed to profile the transcriptome and the proteome, including methods to monitor the function of enzymes in complex biologic systems. These methods typically target specific classes of enzymes and attempt to correlate the enzymatic activity with the specific phenotype of interest. Here, technologies to measure enzymatic activity on a subproteomic scale are reviewed, including the authors' own efforts, which are based on self-assembled microarrays utilizing peptide nucleic acid-encoded small-molecule libraries.

Animals↗

Quality control and quality assessment of data from surface-enhanced laser desorption/ionization (SELDI) time-of flight (TOF) mass spectrometry (MS).

BACKGROUND: Proteomic profiling of complex biological mixtures by the ProteinChip technology of surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry (MS) is one of the most promising approaches in toxicological, biological, and clinic research. The reliable identification of protein expression patterns and associated protein biomarkers that differentiate disease from health or that distinguish different stages of a disease depends on developing methods for assessing the quality of SELDI-TOF mass spectra. The use of SELDI data for biomarker identification requires application of rigorous procedures to detect and discard low quality spectra prior to data analysis. RESULTS: The systematic variability from plates, chips, and spot positions in SELDI experiments was evaluated using biological and technical replicates. Systematic biases on plates, chips, and spots were not found. The reproducibility of SELDI experiments was demonstrated by examining the resulting low coefficient of variances of five peaks presented in all 144 spectra from quality control samples that were loaded randomly on different spots in the chips of six bioprocessor plates. We developed a method to detect and discard low quality spectra prior to proteomic profiling data analysis, which uses a correlation matrix to measure the similarities among SELDI mass spectra obtained from similar biological samples. Application of the correlation matrix to our SELDI data for liver cancer and liver toxicity study and myeloma-associated lytic bone disease study confirmed this approach as an efficient and reliable method for detecting low quality spectra. CONCLUSION: This report provides evidence that systematic variability between plates, chips, and spots on which the samples were assayed using SELDI based proteomic procedures did not exist. The reproducibility of experiments in our studies was demonstrated to be acceptable and the profiling data for subsequent data analysis are reliable. Correlation matrix was developed as a quality control tool to detect and discard low quality spectra prior to data analysis. It proved to be a reliable method to measure the similarities among SELDI mass spectra and can be used for quality control to decrease noise in proteomic profiling data prior to data analysis.

Female↗

Identification of several proteins involved in regulation of sperm motility by proteomic analysis.

Proteomic technology was used to compare sperm protein expression profiles in asthenozoospermic patients with that of normozoospermic donors and 10 differentially expressed proteins were identified. These proteins may play roles in the regulation of sperm motility, and their characterization could merit further investigation on sperm motility-related male factor infertility.

Asthenozoospermia↗

Modern approaches to age-old questions about thyroid tumors.

There is a compelling need for improvement in the diagnosis of thyroid nodules, in predicting thyroid cancer prognosis and, in the treatment of recurrent well-differentiated and anaplastic thyroid cancer. In this review we discuss the impact of genomic technologies such as microarrays, SAGE, and proteomics on the diagnosis, prognosis and treatment of thyroid cancer. Gene expression profiling using these technologies has shown promising results in the molecular classification of different types of cancer, including thyroid. Furthermore, microarrays have been successfully used to identify prognostic markers in other cancer-types, offering the possibility to better tailor thyroid cancer treatment schemes. Lastly, novel therapeutic targeting against tyrosine kinases have shown promising results in the treatment of several cancers and might prove to be beneficial for patients with recurrent or undifferentiated thyroid cancer.

Humans↗

Activity profiling of papain-like cysteine proteases in plants.

Transcriptomic and proteomic technologies are generating a wealth of data that are frequently used by scientists to predict the function of proteins based on their expression or presence. However, activity of many proteins, such as transcription factors, kinases, and proteases, depends on posttranslational modifications that frequently are not detected by these technologies. Therefore, to monitor activity of proteases rather than their abundance, we introduce protease activity profiling in plants. This technology is based on the use of biotinylated, irreversible protease inhibitors that react with active proteases in a mechanism-based manner. Using a biotinylated derivative of the Cys protease inhibitor E-64, we display simultaneous activities of many papain-like Cys proteases in extracts from various tissues and from different plant species. Labeling is pH dependent, stimulated with reducing agents, and inhibited specifically by Cys protease inhibitors but not by inhibitors of other protease classes. Using one-step affinity capture of biotinylated proteases followed by sequencing mass spectrometry, we identified proteases that include xylem-specific XCP2, desiccation-induced RD21, and cathepsin B- and aleurain-like proteases. Together, these results demonstrate that this technology can identify differentially activated proteases and/or characterize the activity of a particular protease within complex mixtures.

Amino Acid Sequence↗

Expression profiling in toxicology--potentials and limitations.

Recent progress in genomics and proteomics technologies has created a unique opportunity to significantly impact the pharmaceutical drug development processes. The perception that cells and whole organisms express specific inducible responses to stimuli such as drug treatment implies that unique expression patterns, molecular fingerprints, indicative of a drug's efficacy and potential toxicity are accessible. The integration into state-of-the-art toxicology of assays allowing one to profile treatment-related changes in gene expression patterns promises new insights into mechanisms of drug action and toxicity. The benefits will be improved lead selection, and optimized monitoring of drug efficacy and safety in pre-clinical and clinical studies based on biologically relevant tissue and surrogate markers.

Animals↗

Printing of protein microarrays via a capillary-free fluid jetting mechanism.

Current proteomics experiments rely upon printing techniques such as ink jet, pin, or quill arrayers that were developed for the creation of cDNA microarrays. These techniques often do not meet the requirements needed for successful spotting of proteins to perform high-throughput, array-based proteomic profiling. Biological laser printing (BioLP) is a spotting technology that does not rely on solid pins, quill pins, or capillary-based fluidics. The non-contact mechanism of BioLP utilizes a focused laser pulse to transfer protein solutions, thereby eliminating the potential for orifice clogging, air bubbles, and unnecessary volume loss potentially encountered in commercially available spotting technologies. The speed and spot-to-spot reproducibility of BioLP is comparable to other techniques, while the minimum spot diameter and volume per printed droplet is significantly less at 30 microm and approximately 500 fL, respectively. The transfer of fluid by BioLP occurs through a fluid jetting mechanism, as observed by high-speed images of the printing process. Arraying a solution of BSA with subsequent immunodetection demonstrates the reproducible spotting of protein in an array format with CVs of <3%. Printing of the enzyme alkaline phosphatase followed by a positive reaction with a colorimetric substrate demonstrates that functional protein can be spotted using this laser-based printer.

Alkaline Phosphatase↗

Comprehensive quantitative proteome analysis of 20S proteasome subtypes from rat liver by isotope coded affinity tag and 2-D gel-based approaches.

Quantitative protein profiling is an essential part of proteomics and requires technologies that accurately, reproducibly, and comprehensively identify and quantify proteins. Over the past years, many quantitative proteomic methods have been developed. Here, 20S proteasome subtypes isolated from rat were compared by four approaches based on the combination of isotope-coded affinity tag (ICAT), 2-DE, LC and ESI and MALDI MS: (i) 2-DE, (ii) ICAT/2-DE MALDI-MS, (iii) ICAT/LC-ESI-MS, (iv) ICAT/LC-MALDI-MS. A definite qualitative advantage of 2-DE gels was the separation of all known protein species, the identification of cysteine sulfoxide of alpha-4 (RC6-IS) and N-terminal acetylation of several subunits. Furthermore, quantitative differences between the standard subunits beta-2, and beta-5 and their immunosubunits were only detected by 2-DE image analysis revealing a higher replacement of standard- by immuno-beta-subunits in subtype IV. It was obvious that for relative quantification only protein spot and mass peaks with a certain level of intensity displayed acceptable values of SD. However, ICAT in conjunction with LC/MALDI-MS was the most accurate method for quantification. The experimental data of this investigation are accessible via http://www.mpiib-berlin.mpg.de/2D-PAGE/.

Acetylation↗

Screening for gynaecological cancers.

BACKGROUND: The role of screening in gynaecological cancers is under evaluation. With mass screening proven effective in significantly reducing cervical cancer mortality, there is an interest in developing other screening methods to detect gynaecological malignancies early. This review covers advances in cervical cancer screening, strategies being investigated in ovarian cancer screening and the lack of justification in screening for endometrial, vulval and vaginal cancers. METHODS: A Medline based literature search was performed for articles relating to screening for different gynaecological malignancies. Additional original papers cited in those identified by the initial search were also reviewed. RESULTS: Advances in cervical cancer screening include liquid-based cytology and HPV testing. Results of ongoing trials are awaited before these can be fully implemented. The results of the two large, multicentre, randomised controlled trials being conducted in the United Kingdom and United States (UKCTOCS and PLCO study, respectively) to assess impact of screening on ovarian cancer mortality will shed some light on the need to implement screening for ovarian cancer in the general population. Novel markers, serum proteomic profiles and Doppler are some of the other technologies being explored. Currently, screening for endometrial cancer is not advocated as most women present with symptoms in early disease with good survival outcomes. Vulval and vaginal cancers are too rare to justify mass screening. CONCLUSION: Methods to screen for various gynaecological malignancies need further evaluation before implementation in the general population. Results of large multicentred trials are awaited. Presently, screening for endometrial, vaginal and vulval cancers is not justified.

Female↗

Biomarkers for neurodegenerative diseases.

PURPOSE OF REVIEW: A major goal of current clinical research in neurodegenerative diseases is to improve early detection of disease and presymptomatic detection of neuronal dysfunction. We also need better tools to assess disease progression in this group of disorders. Currently, many potential disease-modifying therapies are being developed and evaluated at the preclinical stage, and will lead to clinical trials in the near future for which biomarkers are urgently needed. This review summarizes the field of biomarker research in the major neurodegenerative diseases. RECENT FINDINGS: Many different approaches are being undertaken to identify biomarkers and include imaging, neurophysiological and cognitive testing in addition to newer technologies such as biochemical, proteomic, metabanomic and gene array profiling of tissue and biofluids from patients. Key recent findings in each of these areas are discussed. SUMMARY: The ideal biomarker needs to be easy to quantify and measure, reproducible, not subject to wide variation in the general population and unaffected by co-morbid factors. For evaluation of therapies the biomarker needs to change linearly with disease progression and closely correlate with established clinico-pathological parameters of the disease. It is unlikely that any one biomarker will fulfil all these characteristics, and it is likely that more than one biomarker will be needed for early diagnosis and similarly for evaluation of disease progression for therapeutic trials. For example, the combination of more detailed clinical assessments encompassing specific cognitive and neurophysiological testing, in addition to imaging, biochemical and genomic profiling, is likely to be needed.

Animals↗

Proteomic profiling identifies cyclooxygenase-2-independent global proteomic changes by celecoxib in colorectal cancer cells.

Celecoxib, a selective inhibitor of the enzyme cyclooxygenase-2 (COX-2), has been shown to be a promising chemoprevention agent. The chemopreventive efficacy of celecoxib is believed to be a consequence of its COX-2-dependent and COX-2-independent effects on a variety of cellular processes including proliferation, apoptosis, angiogenesis, and immunosurveillance. In an attempt to identify proteomic markers modulated by celecoxib that are independent of its inhibitory effect on COX-2, the colorectal cancer cell line HCT-116, a nonexpresser of COX-2, was treated with celecoxib. We used the powerful, state-of-the-art two-dimensional difference gel electrophoresis technology coupled with mass spectrometric sequencing to compare global proteomic profiles of HCT-116 cells before and after treatment with celecoxib. Among the differentially expressed proteins identified following celecoxib treatment were proteins involved in diverse cellular functions including glycolysis, protein biosynthesis, DNA synthesis, mRNA processing, protein folding, phosphorylation, redox regulation, and molecular chaperon activities. Our study presents a comprehensive analysis of large-scale celecoxib-modulated proteomic alterations, at least some of which may be mechanistically related to the COX-2-independent chemopreventive effect of celecoxib.

Blotting, Western↗

Profiling of the cell surface proteome.

The in depth-mining of the proteome necessitates the comprehensive analysis of proteins in individual subcellular compartments to uncover interesting patterns of protein expression that include assessment of protein location, trafficking and of post-translational modifications that are location specific. One of the compartments of substantial interest from a diagnostic and therapeutic point of view is the plasma membrane which contains intrinsic membrane proteins and other proteins expressed on the cell surface. Technologies are currently available for the comprehensive profiling of the cell surface proteome that rely on protein tagging of intact cells. Studies are emerging that point to unexpected patterns of expression of specific proteins on the cell surface, with a common occurrence of proteins previously considered to occur predominantly in other compartments, notably the endoplasmic reticulum. The profiling of the cell surface and plasma membrane proteomes will likely provide novel insights and uncover disease related alterations.

ADP-ribosyl Cyclase↗

From genomics to proteomics.

Proteomics is the study of the function of all expressed proteins. Tremendous progress has been made in the past few years in generating large-scale data sets for protein-protein interactions, organelle composition, protein activity patterns and protein profiles in cancer patients. But further technological improvements, organization of international proteomics projects and open access to results are needed for proteomics to fulfil its potential.

Animals↗

Contribution of genomics and proteomics in understanding the role of modifying factors in Parkinson's disease.

Parkinson's disease (PD) is a complex neurological disorder, characterized by selective degeneration of nigrostriatal dopaminergic neurons. It is a multi-factorial disease, contributed by a combination of age, genetic and environmental factors. Etiology of sporadic PD and mechanism underlying selective loss of dopaminergic neurons has not yet been clearly understood. Recent developments in genomics and proteomics have revolutionized the research on PD at genetic level. Differential gene expression patterns (DNA biochip technology), age-dependent complex genetic patterns (SNP genotyping), and protein expression profiles (proteomics) of PD patients have started providing the specific and rigorous molecular explanation and role of modifying factors in PD. Genomics and proteomics are further expected to help in developing biomarkers for diagnosis of early onset PD and also to develop valuable and potential therapeutic strategies for its treatment. In this review, we have discussed the progress made by genomics and proteomics, in understanding the role of modifying factors in PD.

Animals↗

Biomarker discovery using protein microarray technology platforms: antibody-antigen complex profiling.

Protein microarrays represent an important new tool in proteomic systems biology. This review focuses on the contributions of protein microarrays to the discovery of novel disease biomarkers through antibody-based assays. Of particular interest is the use of protein microarrays for immune response profiling, through which a disease-specific antibody repertoire may be defined. The antigens and antibodies revealed by these studies are useful for clinical assay development, with enormous potential to aid in diagnosis, prognosis, disease staging and treatment selection. The discovery and characterization of novel biomarkers specifically tailored to disease type and stage are expected to enable personalized medicine by facilitating preventative medicine, predictive diagnostics and individualized curative therapies.

Allergens↗

Unraveling the pathogenesis of type 1 diabetes with proteomics: present and future directions.

Type 1 diabetes (T1D) is the result of selective destruction of the insulin-producing beta-cells in the pancreatic islets of Langerhans. T1D is due to a complex interplay between the beta-cell, the immune system, and the environment in genetically susceptible individuals. The initiating mechanism(s) behind the development of T1D are largely unknown, and no genes or proteins are specific for most T1D cases. Different pro-apoptotic cytokines, IL-1 beta in particular, are present in the islets during beta-cell destruction and are able to modulate beta-cell function and induce beta-cell death. In beta-cells exposed to IL-1 beta, a race between destructive and protective events are initiated and in susceptible individuals the deleterious events prevail. Proteins are involved in most cellular processes, and it is thus expected that their cumulative expression profile reflects the specific activity of cells. Proteomics may be useful in describing the protein expression profile and thus the diabetic phenotype. Relatively few studies using proteomics technologies to investigate the T1D pathogenesis have been published to date despite the defined target organ, the beta-cell. Proteomics has been applied in studies of differentiating beta-cells, cytokine exposed islets, dietary manipulated islets, and in transplanted islets. Although that the studies have revealed a complex and detailed picture of the protein expression profiles many functional implications remain to be answered. In conclusion, a rather detailed picture of protein expression in beta-cell lines, islets, and transplanted islets both in vitro and in vivo have been described. The data indicate that the beta-cell is an active participant in its own destruction during diabetes development. No single protein alone seems to be responsible for the development of diabetes. Rather the cumulative pattern of changes seems to be what favors a transition from dynamic stability in the unperturbed beta-cell to dynamic instability and eventually to beta-cell destruction.

Animals↗