Blue Native PAGE Analysis of Bacterial Secretion Complexes

Bacterial protein secretion systems serve to translocate substrate proteins across up to three biological membranes, a task accomplished by hydrophobic, membrane-spanning macromolecular complexes. The overexpression, purification, and biochemical characterization of these complexes is often difficult, thus impeding progress in understading structure and function of these systems. Blue native (BN) polyacrylamide gel electrophoresis (PAGE) allows for the investigation of these transmembrane complexes right from their originating membranes, without the need of long preparative steps, and is amenable to the parallel characterization of a number of samples under near-native conditions. Here, we present protocols for sample preparation, one-dimensional BN PAGE and two-dimensional BN/SDS PAGE, as well as for downstream analysis by staining, immunoblotting, and mass spectrometry on the example of the type III secretion system encoded on Salmonella pathogenicity island 1.

Synovial fluid proteome profile of surgical versus chemical induced osteoarthritis in rabbits

BACKGROUND

Animal models are significant for understanding human osteoarthritis (OA). This study compared the synovial fluid proteomics changes in surgical and chemical induced OA models.

METHODS

Thirty rabbits either had anterior cruciate ligament transection (ACLT) procedure or injected intra-articularly with monosodium iodoacetate (MIA, 8 mg) into the right knee. The joints were anatomically assessed, and the synovial fluid proteins analyzed using two-dimensional polyacrylamide gel electrophoresis (2DGE) and MALDI TOF/TOF mass spectrometry analysis at 4, 8 and 12 weeks. The proteins' upregulation and downregulation were compared with control healthy knees.

RESULTS

Seven proteins (histidine-rich glycoprotein, beta-actin-like protein 2 isoform X1, retinol-binding protein-4, alpha-1-antiproteinase, gelsolin isoform, serotransferrin, immunoglobulin kappa-b4 chain-C-region) were significantly expressed by the surgical induction. They characterized cellular process (27%), organization of cellular components or biogenesis (27%), localization (27%) and biological regulation (18%), which related to synovitis, increased cellularity, and subsequently cartilage damage. Three proteins (apolipoprotein I-IV precursor, serpin peptidase inhibitor and haptoglobin precursor) were significantly modified by the chemical induction. They characterized stimulus responses (23%), immune responses (15%), biological regulations (15%), metabolism (15%), organization of cellular components or biogenesis (8%), cellular process (8%), biological adhesions (8%) and localization (8%), which related to chondrocytes glycolysis/death, neovascularization, subchondral bone necrosis/collapse and inflammation.

CONCLUSIONS

The surgical induced OA model showed a wider range of protein changes, which were most upregulated at week 12. The biological process proteins expressions showed the chemical induced joints had slower OA progression compared to surgical induced joints. The chemical induced OA joints showed early inflammatory changes, which later decreased.

Two-Dimensional Difference Gel Electrophoresis: A Gel-Based Proteomic Approach for Protein Analysis

Two-dimensional difference gel electrophoresis (2D-DIGE) remains to be one of the most popular and versatile methods of protein separation among many proteomics technologies. Similar to traditional two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), the proteins are separated based on their charges and molecular weight by 2D-DIGE. Different from 2D-PAGE, proteins are pre-labeled with different fluorescent dyes, and different protein samples are run in one gel by this method. Therefore, 2D-DIGE not only carries the advantages of 2D-PAGE but also eliminates gel-to-gel variation and achieves high resolution, sensitivity, and reproducibility.

Increase in Local Protein Concentration by Field-Inversion Gel Electrophoresis

Proteins that migrate through cross-linked polyacrylamide gels (PAGs) under the influence of a constant electric field experience negative factors, such as diffusion and nonspecific trapping in the gel matrix. These negative factors reduce protein concentrations within a defined gel volume with increasing migration distance and, therefore, decrease protein recovery efficiency. Here, we describe the enhancement of protein separation efficiency for up to twofold in conventional one-dimensional PAG electrophoresis (1D PAGE), two-dimensional (2D) PAGE, and native PAGE by implementing pulses of inverted electric field during gel electrophoresis.

Cancer biomarker development and two-dimensional difference gel electrophoresis (2D-DIGE)

Cancer results from the accumulation of genomic alterations. As the genome is functionally translated to the proteome and regulates tumor cell behavior, proteomics studies are expected to further the current understanding of the molecular mechanisms underlying carcinogenesis and cancer progression. Biomarkers are potential tools to classify cancers for therapy, predict responses to treatments, and support treatment-related decision-making. Biomarker development has been actively pursued in oncology by proteomic approaches. Two-dimensional difference gel electrophoresis (2D-DIGE) is a proteomics technique based on two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). In 2D-DIGE, protein samples are labeled with distinct fluorescent dyes before fractionation via 2D-PAGE. 2D-DIGE offers advantages to identify biomarker candidates, including reproducibility, high sensitivity, comprehensiveness, and high throughput. 2D-DIGE has contributed to the establishment of tissue biomarkers, which potentially facilitate precision medicine. 2D-DIGE is thus expected to yield major advancements in cancer biomarker identification and development.

Blue Native PAGE Analysis of Bacterial Secretion Complexes

Bacterial protein secretion systems serve to translocate substrate proteins across up to three biological membranes, a task accomplished by hydrophobic, membrane-spanning macromolecular complexes. The overexpression, purification, and biochemical characterization of these complexes is often difficult, impeding progress in understanding the structure and function of these systems. Blue native (BN) polyacrylamide gel electrophoresis (PAGE) allows for the investigation of these transmembrane complexes right from their originating membranes, without the need for long preparative steps, and is amenable to the parallel characterization of a number of samples under near-native conditions. Here we present protocols for sample preparation, one-dimensional BN PAGE and two-dimensional BN/sodium dodecyl sulfate (SDS)-PAGE, as well as for downstream analysis by staining, immunoblotting, and mass spectrometry on the example of the type III secretion system encoded on Salmonella pathogenicity island 1.

A Novel 2-DE-Based Proteomic Analysis to Identify Multiple Substrates for Specific Protease in Neuronal Cells

Proteolysis is a process where proteins are broken down into smaller polypeptides or amino acids, comprising one of the important posttranslational modifications of proteins. Since this process is exquisitely achieved by specialized enzymes called proteases under physiological conditions, abnormal protease activity and dysregulation of their substrate proteins are closely associated with a progression of several neurodegenerative diseases including Alzheimer disease, Parkinson disease, stroke, and spinal cord injury. Thus, it is important to identify the specific substrates of proteases with nonbiased high-throughput screenings to understand how proteolysis contributes to neurodegeneration. Here, we described a so-called gel-based protease proteomic approach. Critical steps of our novel strategy consist of two-dimensional polyacrylamide gel electrophoresis (2-DE)-based protein separation and in vitro incubation with the specific protease of interest. As a prototypic example, cellular lysates obtained from neuronal cells are separated by an isoelectric focusing, and the resulting immobilized proteins on a gel strip are incubated with a predetermined amount of a recombinant or a purified protease. By densitometric analysis of the Coomassie Brilliant Blue-stained gel images following separation by 2-DE, significantly altered protein spots are subjected to a mass spectral analysis for protein identification. Interestingly, the concepts of our strategy can be applied to any proteases, and to any neural cells or neural tissues of one's interest. Since the immobilized protein spots are exposed to the purified protease, this protocol ensures the identification of only substrates that are directly cleaved by specific protease. This protocol ensures to avoid the possibility of identifying substrates that may be cleaved by combinatorial or sequential activation of proteolytic enzymes present in a liquid state of the lysates. We propose that our strategy can be effectively utilized to provide meaningful insights into newly identified protease substrates and to decipher molecular mechanisms critically involved in neurodegenerative processes.

Pathogenicity of Leishmania donovani is associated with the high expression of a group low molecular weight proteins

Background:

With few exceptions, members of the Leishmania donovani complex such as L. donovani, L. infantum and L. chagashi are the etiological agents of visceral leishmaniasis or kala-azar. Promastigotes of Leishmania spp. lose their Pathogenicity; the ability to establish infection in a susceptible host, after prolonged culture. The molecular basis of this evolution of pathogenic to nonpathogenic culture has not been very well understood. It has been proposed that the loss of pathogenicity is associated with the gradual disappearance of selective parasite proteins. An alternative hypothesis is that during prolonged culture, the pathogenic clonal population of the parasite is deleted from the mixed population due to their selection pressure. This clonal deletion is proposed to be responsible for the emergence of the nonpathogenic population.

Study Methodology and Results:

We have a done a series of two-dimensional polyacrylamide gel electrophoresis followed by western blot experiments to study the antigenic profile of few L. donovani isolates of Indian origin. We observed a gradual and significant downregulation of expression of a group of low molecular weight proteins (LMW, molecular weight 20–30 kDa) which are associated with loss of pathogenicity. These proteins are recognized only by antiserum raised against the whole cell extract of one of the pathogenic Indian L. donovani isolates, Ag83, and remained undetected by antiserum raised against the nonpathogenic AG83 isolates. These LMW proteins were also present in the nonpathogenic extract in very low levels and remained undetected by the virulent serum, indicating a phenomenon of simultaneous downregulation of the expression and altered immunogenicity. LMW proteins were universally expressed in all early passage Indian isolate we tested and also detected in two clones obtained from pathogenic parasite culture. The antigenic patterns of none of the eight clones obtained from nonpathogenic culture were not exactly similar with the pathogenic clones.

Conclusion:

Therefore, our data strongly support the hypothesis that the loss of pathogenicity of L. donovani is associated with a change in antigenic profile, but not due the selective deletion of pathogenic clones.

'Omics' techniques for identifying flooding-response mechanisms in soybean

Plant growth and productivity are adversely influenced by various environmental stresses, which often lead to reduced seedling growth and decreased crop yields. Plants respond to stressful conditions through changes in 'omics' profiles, including transcriptomics, proteomics, and metabolomics. Linking plant phenotype to gene expression patterns, protein abundance, and metabolite accumulation is one of the main challenges for improving agricultural production. 'Omics' approaches may shed insight into the mechanisms that function in soybean in response to environmental stresses, particularly flooding by frequent rain, which occurs worldwide due to changes in global climate. Flooding causes significant reductions in the growth and yield of several crops, especially soybean. The application of 'omics' techniques may facilitate the development of flood-tolerant cultivars of soybean. In this review, the use of 'omics' techniques towards understanding the flooding-responsive mechanisms of soybeans is discussed, as the findings from these studies are expected to have applications in both breeding and agronomy. This article is part of a Special Issue entitled: Translational Plant Proteomics.

Can proteomics lead to the discovery of real biomarkers for HCC?

The development of proteomics technologies has lead to a great deal of effort being focused on the identification of biomarkers for cancers. Although many papers have reported candidate biomarkers for hepatocellular carcinomas (HCCs) in particular, so far none of these candidate biomarkers have been used either for diagnosis or therapy intreating patients. The question remains: Can proteomics identify real biomarkers for HCCs?

Comparative proteomics analysis of human gastric cancer

AIM: To isolate and identify differentially expressed proteins between cancer and normal tissues of gastric cancer by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

METHODS: Soluble fraction proteins of gastric cancer tissues and paired normal tissues were separated by 2-DE. The differentially expressed proteins were selected and identified by MALDI-TOF-MS and database search.

RESULTS: 2-DE profiles with high resolution and reproducibility were obtained. Twenty-three protein spots were excised from sliver staining gel and digested in gel by trypsin, in which fifteen protein spots were identified successfully. Among the identified proteins, there were ten over-expressed and five under-expressed proteins in stomach cancer tissues compared with normal tissues.

CONCLUSION: In this study, the well-resolved, reproducible 2-DE patterns of human gastric cancer tissue and paired normal tissue were established and optimized and certain differentially-expressed proteins were identified. The combined use of 2-DE and MS provides an effective approach to screen for potential tumor markers.

Research progress in screening biomarkers of pancreatic cancer by proteomic techniques

Pancreatic cancer is one kind of devastating diseases. Those patients without nonspecific symptoms at early stage had mostly lost the opporunity of surgical therapy when pancreatic cancer was detected at advanced stage. Rapid growth of proteomic technologies provides possibilities to study etiopathogenesis, and screen early diagnostic and prognosis biomarkers of pancreatic cancer. In this paper, the application of proteomic techniques in cell lines, tissues, serum and pancreatic juice from patients with pancreatic cancer is reviewed briefly.

Protein expression profile using two-dimensional gel analysis in squamous cervical cancer patients

PURPOSE

Screening in cervical cancer is now progressing to discover candidate genes and proteins that may serve as biological markers and that play a role in tumor progression. We examined the protein expression patterns of the squamous cell carcinoma (SCC) tissues from Korean women with using two- dimensional polyacrylamide gel electrophoresis (2-DE) and matrix assisted laser desorption/ionization-time of flight (MALDI- TOF) mass spectrometer.

MATERIALS AND METHODS

Normal cervix and SCC tissues were solubilized and 2-DE was performed using pH 3 approximately 10 linear IPG strips of 17 cm length. The protein expression was evaluated using PDQuest 2-D software. The differentially expressed protein spots were identified with a MALDI-TOF mass spectrometer, and the peptide mass spectra identifications were performed using the Mascot program and by searching the Swiss-prot or NCBInr databases.

RESULTS

A total of 35 proteins were detected in SCC. 17 proteins were up-regulated and 18 proteins were down-regulated. Among the proteins that were identified, 12 proteins (pigment epithelium derived factor, annexin A2 and A5, keratin 19 and 20, heat shock protein 27, smooth muscle protein 22 alpha, alpha-enolase, squamous cell carcinoma antigen 1 and 2, glutathione S-transferase and apolipoprotein a1) were protein previously known to be involved in tumor, and 21 proteins were newly identified in this study.

CONCLUSION

2-DE offers the total protein expression profiles of SCC tissues; further characterization of these differentially expressed proteins will give a chance to identify the badly needed tumor-specific diagnostic markers for SCC.

Changes in cell surface proteins of culturedDrosophila cells exposed to 20-hydroxyecdysone

Drosophila cell lines have provided popular material for study of the mechanisms by which steroid hormones regulate cellular events. Previous investigations at the organismic or organ level have suggested that ecdysteroids are bound by a cytoplasmic receptor, and that the resulting complex translocates to the nucleus where it results in active transcription of a few genes. The protein products of these primary responding genes then modulate a larger series of secondary transcriptional changes. In cultured cells, other investigators have detected the hormonally-induced synthesis of only 4-5 new polypeptides through 72 h of treatment. Although these proteins may represent the gene products associated with the primary response, this small number of changes is surprising in view of the rapid morphological alteration of the cells and changes in such surface-mediated behavior as substrate adhesion and agglutinability observed within the same time interval. In this report, we show that lactoperoxidase-catalyzed radioiodination followed by 2-dimensional polyacrylamide gel electrophoresis and autoradiography provide an effective protocol for visualizing cell surface proteins of a Drosophila cell line. Among the more than 175 labeled species detected, comparisons of control cells with those treated by 20-hydroxyecdysone for 72 h shows at least 27 differences. We interpret these differences as the result of the secondary transcriptional response to the hormone.