Selective labelling of cell-surface proteins using CyDye DIGE Fluor minimal dyes.

Surface proteins are central to the cell's ability to react to its environment and to interact with neighboring cells. They are known to be inducers of almost all intracellular signaling. Moreover, they play an important role in environmental adaptation and drug treatment, and are often involved in disease pathogenesis and pathology (1). Protein-protein interactions are intrinsic to signaling pathways, and to gain more insight in these complex biological processes, sensitive and reliable methods are needed for studying cell surface proteins. Two-dimensional (2-D) electrophoresis is used extensively for detection of biomarkers and other targets in complex protein samples to study differential changes. Cell surface proteins, partly due to their low abundance (1 2% of cellular proteins), are difficult to detect in a 2-D gel without fractionation or some other type of enrichment. They are also often poorly represented in 2-D gels due to their hydrophobic nature and high molecular weight (2). In this study, we present a new protocol for intact cells using CyDye DIGE Fluor minimal dyes for specific labeling and detection of this important group of proteins. The results showed specific labeling of a large number of cell surface proteins with minimal labeling of intracellular proteins. This protocol is rapid, simple to use, and all three CyDye DIGE Fluor minimal dyes (Cy 2, Cy 3 and Cy 5) can be used to label cell-surface proteins. These features allow for multiplexing using the 2-D Fluorescence Difference Gel Electrophoresis (2-D DIGE) with Ettan DIGE technology and analysis of protein expression changes using DeCyder 2-D Differential Analysis Software. The level of cell-surface proteins was followed during serum starvation of CHO cells for various lengths of time (see Table 1). Small changes in abundance were detected with high accuracy, and results are supported by defined statistical methods.

A quantitative proteomic analysis of soluble bronchoalveolar fluid proteins from patients with sarcoidosis and chronic beryllium disease.

BACKGROUND: Sarcoidosis and chronic beryllium disease (CBD) are granulomatous disorders which can lead to development of chronic inflammation and fibrosis. These diseases have several similarities from their clinical aspects. The aim of this study was to compare the protein profile at the site of active inflammation i.e. the lungs of patients with sarcoidosis and CBD. METHODS: Bronchoalveolar lavage (BAL) proteins from patients having sarcoidosis or CBD were studied using two dimensional gel based proteomics. In this study, we used Difference Gel Electrophoresis (DIGE) proteomics approach to analyse the protein expression profiles from sarcoidosis patients (n=4), CBD (n=4) and healthy controls (n = 5). Subsequently, differentially expressed proteins were identified by using mass spectrometry. RESULTS: We found 37 protein-spots with statistically different expression levels, and identified 14 of these proteins. The protein expression levels of peroxiredoxin 5, heat shock protein 70, complement C3, annexin A2 and transthyretin were significantly different in sarcoidosis versus control group. The proteins; hemopexin, beta2-microglobulin, alpha-1 antitrypsin, cystatin B, IgG kappa chain, apolipoprotein A1, and albumin were significantly different between CBD versus control group. When comparing CBD versus sarcoidosis, we found superoxide dismutase and hemoglobin upregulated in the CBD group. CONCLUSION: By using quantitative proteomics, we were able to find proteins with different expression levels in both diseases.

A proteomics approach to the study of absorption, distribution, metabolism, excretion, and toxicity.

A proteomics approach was used to identify liver proteins that displayed altered levels in mice following treatment with a candidate drug. Samples from livers of mice treated with candidate drug or untreated were prepared, quantified, labeled with CyDye DIGE Fluors, and subjected to two-dimensional electrophoresis. Following scanning and imaging of gels from three different isoelectric focusing intervals (3-10, 7-11, 6.2-7.5), automated spot handling was performed on a large number of gel spots including those found to differ more than 20% between the treated and untreated condition. Subsequently, differentially regulated proteins were subjected to a three-step approach of mass spectrometry using (a) matrix-assisted laser desorption/ionization time-of-flight mass spectrometry peptide mass fingerprinting, (b) post-source decay utilizing chemically assisted fragmentation, and (c) liquid chromatography-tandem mass spectrometry. Using this approach we have so far resolved 121 differentially regulated proteins following treatment of mice with the candidate drug and identified 110 of these using mass spectrometry. Such data can potentially give improved molecular insight into the metabolism of drugs as well as the proteins involved in potential toxicity following the treatment. The differentially regulated proteins could be used as targets for metabolic studies or as markers for toxicity.