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Up-regulation of competence- but not stress-responsive proteins accompanies an altered metabolic phenotype in Streptococcus mutans biofilms.

Mature biofilm and planktonic cells of Streptococcus mutans cultured in a neutral pH environment were subjected to comparative proteome analysis. Of the 242 protein spots identified, 48 were significantly altered in their level of expression (P<0.050) or were unique to planktonic or biofilm-grown cells. Among these were four hypothetical proteins as well as proteins known to be associated with the maintenance of competence or found to possess a cin-box-like element upstream of their coding gene. Most notable among the non-responsive genes were those encoding the molecular chaperones DnaK, GroEL and GroES, which are considered to be up-regulated by sessile growth. Analysis of the rest of the proteome indicated that a number of cellular functions associated with carbon uptake and cell division were down-regulated. The data obtained were consistent with the hypothesis that a reduction in the general growth rate of mature biofilms of S. mutans in a neutral pH environment is associated with the maintenance of transformation without the concomitant stress response observed during the transient state of competence in bacterial batch cultures.

Adaptation, Physiological↗

Analysis of detergent-resistant membranes in Arabidopsis. Evidence for plasma membrane lipid rafts.

The trafficking and function of cell surface proteins in eukaryotic cells may require association with detergent-resistant sphingolipid- and sterol-rich membrane domains. The aim of this work was to obtain evidence for lipid domain phenomena in plant membranes. A protocol to prepare Triton X-100 detergent-resistant membranes (DRMs) was developed using Arabidopsis (Arabidopsis thaliana) callus membranes. A comparative proteomics approach using two-dimensional difference gel electrophoresis and liquid chromatography-tandem mass spectrometry revealed that the DRMs were highly enriched in specific proteins. They included eight glycosylphosphatidylinositol-anchored proteins, several plasma membrane (PM) ATPases, multidrug resistance proteins, and proteins of the stomatin/prohibitin/hypersensitive response family, suggesting that the DRMs originated from PM domains. We also identified a plant homolog of flotillin, a major mammalian DRM protein, suggesting a conserved role for this protein in lipid domain phenomena in eukaryotic cells. Lipid analysis by gas chromatography-mass spectrometry showed that the DRMs had a 4-fold higher sterol-to-protein content than the average for Arabidopsis membranes. The DRMs were also 5-fold increased in sphingolipid-to-protein ratio. Our results indicate that the preparation of DRMs can yield a very specific set of membrane proteins and suggest that the PM contains phytosterol and sphingolipid-rich lipid domains with a specialized protein composition. Our results also suggest a conserved role of lipid modification in targeting proteins to both the intracellular and extracellular leaflet of these domains. The proteins associated with these domains provide important new experimental avenues into understanding plant cell polarity and cell surface processes.

Arabidopsis↗

Involvement of multitargets in paeoniflorin-induced preconditioning.

Paeoniflorin (PF) is the principal component of Paeoniae radix prescribed in traditional Chinese medicine. The delayed neuroprotection induced by PF preconditioning and its underlying mechanisms were investigated in rat middle cerebral artery occlusion (MCAO) and reperfusion model. At a dosage of 20 or 40 mg/kg, PF preconditioning 48 h before MCAO followed by 24-h reperfusion significantly reduced the mortality and infarct volume and reversed the neurological deficits caused by ischemia. Likewise, the ameliorative effects on mortality, infarct size, and neurological impairment induced by MCAO emerged as well when PF was administered 24 h, 48 h, or 5 days before MCAO at the dose of 20 mg/kg. Furthermore, comparative proteomics analysis was adopted to identify the differentially expressed proteins induced by PF preconditioning itself. The relative levels of 42 proteins were altered after PF preconditioning, among which 20 were elevated and 22 reduced. In summary, A(1) receptor-regulator of G protein signaling-K(ATP) signaling, arachidonic acid cascade, nitric oxide system, markers of neuronal damage, mitochondrial damage-related molecules, and the mitogen-activated protein kinase and nuclear factor-kappaB pathway are associated with the mechanisms of PF preconditioning.

Adenosine Triphosphate↗

Microbial metalloproteinases mediate sensing of invading pathogens and activate innate immune responses in the lepidopteran model host Galleria mellonella.

Thermolysin-like metalloproteinases such as aureolysin, pseudolysin, and bacillolysin represent virulence factors of diverse bacterial pathogens. Recently, we discovered that injection of thermolysin into larvae of the greater wax moth, Galleria mellonella, mediated strong immune responses. Thermolysin-mediated proteolysis of hemolymph proteins yielded a variety of small-sized (<3 kDa) protein fragments (protfrags) that are potent elicitors of innate immune responses. In this study, we report the activation of a serine proteinase cascade by thermolysin, as described for bacterial lipopolysaccharides (LPS), that results in subsequent prophenoloxidase activation leading to melanization, an elementary immune defense reaction of insects. Quantitative real-time reverse transcription-PCR analyses of the expression of immune-related genes encoding the inducible metalloproteinase inhibitor, gallerimycin, and lysozyme demonstrated increased transcriptional rates after challenge with purified protfrags similar to rates after challenge with LPS. Additionally, we determined the induction of a similar spectrum of immune-responsive proteins that were secreted into the hemolymph by using comparative proteomic analyses of hemolymph proteins from untreated larvae and from larvae that were challenged with either protfrags or LPS. Since G. mellonella was recently established as a valuable pathogenicity model for Cryptococcus neoformans infection, the present results add to our understanding of the mechanisms of immune responses in G. mellonella. The obtained results support the proposed danger model, which suggests that the immune system senses endogenous alarm signals during infection besides recognition of microbial pattern molecules.

Animals↗

A mutant of Francisella tularensis strain SCHU S4 lacking the ability to express a 58-kilodalton protein is attenuated for virulence and is an effective live vaccine.

Francisella tularensis subsp. tularensis (type A) strain SCHU S4 is a prototypic strain of the pathogen that is highly virulent for humans and other mammals. Its intradermal (i.d.) 50% lethal dose (LD50) for mice is <10 CFU. We discovered a spontaneous mutant, designated FSC043, of SCHU S4 with an i.d. LD50 of >10(8) CFU. FSC043 effectively vaccinated mice against challenge with a highly virulent type A strain, and the protective efficacy was at least as good as that of F. tularensis LVS, an empirically attenuated strain which has been used as an efficacious human vaccine. Comparative proteomics was used to identify two proteins of unknown function that were identified as defective in LVS and FSC043, and deletion mutants of SCHU S4 were created for each of the two encoding genes. One mutant, the DeltaFTT0918 strain, failed to express a 58-kDa protein, had an i.d. LD50 of approximately 10(5) CFU, and was found to be less capable than SCHU S4 of growing in peritoneal mouse macrophages. Mice that recovered from sublethal infection with the DeltaFTT0918 mutant survived when challenged 2 months later with >100 LD50s of the highly virulent type A strain FSC033. This is the first report of the generation of defined mutants of F. tularensis subsp. tularensis and their use as live vaccines.

Administration, Cutaneous↗

Physiologic effects of forced down-regulation of dnaK and groEL expression in Streptococcus mutans.

Strains of Streptococcus mutans lacking DnaK or GroEL appear not to be isolable. To better distinguish the roles played by these chaperones/chaperonins in the physiology of S. mutans, we created a knockdown strategy to lower the levels of DnaK by over 95% in strain SM12 and the level of GroEL about 80% in strain SM13. Interestingly, GroEL levels were approximately twofold higher in SM12 than in the parent strain, but the levels of DnaK were not altered in the GroEL knockdown strain. Both SM12 and SM13 grew slower than the parent strain, had a strong tendency to aggregate in broth culture, and showed major changes in their proteomes. Compared with the wild-type strain, SM12 and SM13 had impaired biofilm-forming capacities when grown in the presence of glucose. The SM12 strain was impaired in its capacity to grow at 44 degrees C or at pH 5.0 and was more susceptible to H(2)O(2), whereas SM13 behaved like the wild-type strain under these conditions. Phenotypical reversions were noted for both mutants when cells were grown in continuous culture at a low pH, suggesting the occurrence of compensatory mutations. These results demonstrate that DnaK and GroEL differentially affect the expression of key virulence traits, including biofilm formation and acid tolerance, and support that these chaperones have evolved to accommodate unique roles in the context of this organism and its niche.

Bacterial Proteins↗

Metabotropic glutamate receptor 4-mediated 5-Fluorouracil resistance in a human colon cancer cell line.

PURPOSE: 5-Fluorouracil (5-FU) has been the mainstay treatment for colorectal cancer for the past few decades. However, as with other cancers, development of 5-FU resistance has been a major obstacle in colorectal cancer chemotherapy. The purpose of this study was to gain further understanding of the mechanisms underlying 5-FU resistance in colorectal cancer cells. EXPERIMENTAL DESIGN: A 5-FU-resistant cell line was established from the human colon cancer cell line SNU-769A. Protein extracts from these two cell lines (parent and resistant) were analyzed using comparative proteomics to identify differentially expressed proteins. RESULTS: 5-FU-resistant human colon cancer cells were found to overexpress metabotropic glutamate receptor 4 (mGluR4). Other experiments showed cellular resistance to 5-FU (i.e., cell survival) was altered by the mGluR4 agonist l-2-amino-4-phosphonobutyric acid (L-AP 4), and by the mGluR4 antagonist (S)-amino-2-methyl-4-phosphonobutanoic acid (MAP 4), in that L-AP 4 increased 5-FU resistance in SNU-769A cells, whereas MAP 4 ablated 5-FU resistance in 5-FU-resistant cells. However, there was no significant effect of L-AP 4 or MAP 4 on basal cAMP and thymidylate synthase levels. Interestingly, 5-FU down-regulated mGluR4 expression, and MAP 4 suppressed proliferation in both cell lines. CONCLUSIONS: We here report mGluR4 expression in human colon cancer cell line, which provides further evidence for extra-central nervous system expression of glutamate receptors. Overexpression of mGluR4 may tentatively be responsible for 5-FU resistance and, although activation by agonist promotes cell survival in the presence of 5-FU, decreased mGluR4 expression or inactivation by antagonist contributes to cell death.

Amino Acids↗

Studies on substantially increased proteins in follicular fluid of bovine ovarian follicular cysts using 2-D PAGE and MALDI-TOF MS.

BACKGROUND: The objective of this study was to identify substantially increased proteins in bovine cystic follicular fluid (FF) in order to clarify the pathology and etiology of bovine ovarian follicular cysts (BOFC). METHODS: Proteins in normal and cystic FF samples were subjected to two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and were compared using silver stained gel images with PDQuest image analysis software. Peptides from these increased spots were analyzed by matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), and were identified based on the NCBI database by a peptide mass fingerprinting method. RESULTS: Comparative proteomic analysis showed 8 increased protein spots present in cystic FF. MS analysis and database searching revealed that the increased proteins in cystic FF were bovine mitochondrial f1-atpase (BMFA), erythroid associated factor (EAF), methionine synthase (MeS), VEGF-receptor, glyceraldehydes 3-phosphate dehydrogenase (GAPDH), heat shock protein 70 (HSP70), beta-lactoglobulin (BLG) and succinate dehydrogenase Ip subunit (SD). CONCLUSION: Our results suggest that these proteins are overexpressed in BOFC, and that they may play important roles in the pathogenesis of BOFC. Furthermore, these proteins in the FF could be useful biomarkers for BOFC.

Animals↗

Innate immune response by ficolin binding in apoptotic placenta is associated with the clinical syndrome of preeclampsia.

BACKGROUND: Unidentified circulating factors derived from placenta are thought to be responsible for the exaggerated systemic inflammation leading to preeclampsia. Our aim was to identify the circulating factors present in preeclampsia and to investigate their relationship to the underlying systemic immune response responsible for the associated clinical manifestations. METHODS: We obtained blood samples from pregnant women with and without preeclampsia and performed comparative proteomic analyses to identify the abnormal circulating factors by 2-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time of flight for protein separation and identification. In placentas from preeclamptic pregnancies, we evaluated the potential role of the candidate proteins identified by Western and immunohistochemical analysis. We also used proinflammatory cytokine antibody arrays to investigate local and systemic immune responses. RESULTS: We found that ficolins, the pattern-recognition proteins involved in the lectin-complement pathway, were differentially expressed in plasma from preeclamptic pregnancies. Ficolins were present in low concentrations in plasma but at high concentrations in the placenta, particularly in syncytiotrophoblasts undergoing apoptosis. The binding of ficolins in apoptotic trophoblasts induced innate immunity through local and systemic cytokine activation and correlated with the clinical manifestation of preeclampsia. CONCLUSIONS: We identified specific in vivo circulating factors derived from the placenta that are responsible for the local immune recognition and systemic inflammatory response in the development of clinical manifestations of preeclampsia. These findings may have predictive value and also therapeutic applications to lessen adverse clinical outcomes of preeclampsia.

Apoptosis↗

Visible and fluorescent staining of two-dimensional gels.

Staining of two-dimensional gel constitutes a crucial step in comparative proteome analysis with respect to the number of proteins analyzed, the accuracy of spot quantification, and compatibility with mass spectrometry. The present chapter describes procedures for several visible and fluorescent dyes compatible with mass spectrometry: colloidal Coomassie blue, silver nitrate, Sypro Ruby, Deep Purple, and 5-hexadecanoylamino-fluorescein.

Arabidopsis↗

Quantitative analysis of 2D gels.

The use of 2D electrophoresis for comparative proteomics allows the revelation of variations of protein relative amounts according to various physiological or genetic criteria. The statistical significance of these results is related to different factors, from the experimental design to the statistical tests. In this chapter we describe different parameters that should be taken into account in the experimental design and during image acquisition, and we present different programs for the normalization of quantitative data, the selection of reproducible spots according to user-defined criteria, and the selection of spots showing qualitative and significant quantitative variations.

Algorithms↗

Differential protein expression induced by transient transfection of metallothionein-3 gene in SH-SY5Y neuroblastoma cell line.

Metallothionein-3(MT-3), also known as growth inhibitory factor (GIF), is predominantly expressed in central nervous system (CNS). It belongs to the family of metallothionein(MT) but has several unique properties that are not shared by other family members such as MT-1/MT-2. In the past few years, MT-3 had been postulated to be a multipurpose protein which could play important neuromodulatory and neuroprotective roles in CNS besides the common roles of MTs. However, the primary function of MT-3 and the mechanism underlying its multiple functions were not elucidated so far. In present study, human neuroblastoma cell line SH-SY5Y was employed to study the overall cellular protein changes induced by transient transfection of MT-3 gene, based on comparative proteome analysis. Averagely about 750 spots were visualized by Coomassie staining in one 2D gel, in which 17 proteins were shown to display significant and reproducible changes by semiquantitative analysis with ImageMaster 2D Elite software. Among them, 12 proteins were up-regulated while other 5 proteins were down-regulated. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 10 proteins were further identified to be zinc finger protein, glutamate transporter, and enhancer protein, etc., which were involved in several important pathways regulating the functions of central nervous system. The results showed that MT-3 might exert its unique functions by regulating the expression of these proteins.

Adaptor Proteins, Signal Transducing↗

Preferred amino acids and thermostability.

Most organisms grow at temperatures from 20 to 50 degrees C, but some prokaryotes, including Archaea and Bacteria, are capable of withstanding higher temperatures, from 60 to >100 degrees C. Their biomolecules, especially proteins, must be sufficiently stable to function under these extreme conditions; however, the basis for thermostability remains elusive. We investigated the preferential usage of certain groupings of amino acids and codons in thermally adapted organisms, by comparative proteome analysis, using 28 complete genomes from 18 mesophiles (M), 4 thermophiles (T), and 6 hyperthermophiles (HT). Whenever the percent of glutamate (E) and lysine (K) increased in the HT proteomes, the percent of glutamine (Q) and histidine (H) decreased, so that the E + K/Q + H ratio was >4.5; it was <2.5 in the M proteomes, and 3.2 to 4.6 in T. The E + K/Q + H ratios for chaperonins, potentially thermostable proteins, were higher than their proteome ratios, whereas for DNA ligases, which are not necessarily thermostable, they followed the proteome ratios. Analysis of codon usage revealed that HT had more AGR codons for Arg than they did CGN codons, which were more common in mesophiles. The E + K/Q + H ratio may provide a useful marker for distinguishing HT, T and M prokaryotes, and the high percentage of the amino acid couple E + K, consistently associated with a low percentage of the pair Q + H, could contribute to protein thermostability. The preponderance of AGR codons for Arg is a signature of all HT so far analyzed. The E + K/Q + H ratio and the codon bias for Arg are apparently not related to phylogeny. HT members of the Bacteria show the same values as the HT members of the Archaea; the values for T organisms are related to their lifestyle (intermediate temperature) and not to their domain (Archaea) and the values for M are similar in Eukarya, Bacteria and Archaea.

Adaptation, Biological↗

[Study on the relationship between serum cytokeratin 19 level in hepatocellular carcinoma patients and the clinico-pathologic characteristics].

OBJECTIVE: As our previous comparative proteomics study on high and low metastasis human hepatocellular carcinoma (HCC) cell strains revealed that cytokeratin 19 (CK19) was related to higher metastasis potential, we further investigated the relationship between serum CK19 level in HCC patients and their clinico-pathologic characteristics. METHODS: Serum CK19 levels of 101 normal controls and 108 pathology-proven HCC patients were determined using radioimmunoassay, and the their correlation with clinico-pathologic parameters were studied. RESULTS: The upper limit of one-side 98% confidence interval of normal serum CK19 level was 2.3 microg/L. Among 108 HCC patients, 24 (22.2%) had increased serum CK19 level, ranging from 2.4 to 45.5 microg/L. There were 12 patients (11.1%) with increased CK19 level but normal AFP level. The percentage of poor differentiated tumor was higher in CK19 increased cases (37.5%, 9/24) than in CK19 normal cases (20.2%, 17/84). Moreover, the presence of portal vein tumor emboli was significantly higher in CK19 increased cases (25.0%, 6/24) than in CK19 normal cases (6.0%, 5/84). (Chi-square = 7.403, P < 0.01) In addition, the percentage of TNM stage III/IV tumor was significantly higher in CK19 increased patients (54.2%, 13/24) than in CK19 normal cases. (chi-square = 13.300, P < 0.005) CONCLUSION: Some HCC patients do have increased serum CK19 level, which could be related to portal vein tumor emboli, poor tumor differentiation and advanced tumor stages.

Adult↗

Release of the mitochondrial enzyme carbamoyl phosphate synthase under septic conditions.

To identify sepsis-related dysregulations of protein expression in the liver, we used a baboon model of acute endotoxemia and performed comparative proteome analysis. Treatment with lipopolysaccharide (LPS) was followed by an early but long-lasting (5-48 h) generation of N-terminal fragments of carbamoyl phosphate synthase-1 (CPS-1), an abundant enzyme of the hepatic urea cycle, which is normally located in the mitochondrial matrix. In addition, we developed a new sandwich immunoassay to determine circulating CPS-1 in human and baboons. We found CPS-1 to be induced by LPS and to be released into the circulation of healthy humans and baboons as early as 4 to 5 h after stimulation. Similarly, CPS-1 levels increased after injection of gram-positive bacteria in another baboon model. Enhanced CPS-1 levels were also detected in serum of patients with sepsis. Our data demonstrate fragmentation of CPS-1 in the liver and early increase in circulating CPS-1 levels under septic conditions. We suggest that circulating CPS-1 might serve as a novel serum marker indicating mitochondrial impairment of the liver and/or the small intestine in critically ill patients.

Animals↗

[Analysis of differential proteins in laryngeal carcinoma cell line Hep-2 with transfection of LCRG1].

BACKGROUND & OBJECTIVE: Laryngeal carcinoma-related gene 1 (LCRG1), a novel laryngeal carcinoma-related tumor suppressor gene, was cloned with mRNA differential display method. Previous researches showed LCRG1 might inhibit cell growth, proliferation, colony formation in soft agar, and tumorigenesis of laryngeal carcinoma cell line Hep-2. This study was to screen the proteins associated with the tumor suppressive function of LCRG1 by comparative proteomics method. METHODS: The whole cellular proteins of Hep-2/LCRG1 and Hep-2/pcDNA3.1(+) cells were extracted and separated by two-dimensional gel electrophoresis (2-DE) technology. After electrophoresis, the gels were stained by Coomassie Brilliant Blue G-250, and analyzed using PDQuest software. The differentially expressed proteins were cut from the gels, analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), or electrospray ionization-quadrupole time-of-flight MS/MS (ESI-Q-TOF MS/MS), and identified through searching database with Mascot software. RESULTS: The well-resolved, reproducible 2-DE patterns of Hep-2/LCRG1 and Hep-2/pcDNA3.1(+) cells were established. The total protein spots were 1,075+/-43 in Hep-2/LCRG1 cells and 1,027+/-23 in Hep-2/pcDNA3.1(+) cells, with an average matching rate of 91%. Using mass spectrometry technology, 20 differential protein spots between the 2 cell lines were identified. Among them, 16 were identified by MALDI-TOF-MS, and 4 were identified by ESI-Q-TOF MS/MS. Some of the identified proteins were characterized as members of cellular transcription and metabolism enzymes. CONCLUSIONS: In this study, 2-DE gels of Hep-2/LCRG1 cell line with high expression of LCRG1 mRNA and vector control Hep-2/pcDNA3.1(+) cell line were established; some differential proteins related to LCRG1 were identified by mass spectrometry. These data will help to illustrate the molecular mechanism of LCRG1.

Adaptor Proteins, Signal Transducing↗

Gel-free and gel-based proteomics in Bacillus subtilis: a comparative study.

The proteome of exponentially growing Bacillus subtilis cells was dissected by the implementation of shotgun proteomics and a semigel-based approach for a particular exploration of membrane proteins. The current number of 745 protein identifications that was gained by the use of two-dimensional gel electrophoresis could be increased by 473 additional proteins. Therefore, almost 50% of the 2500 genes expressed in growing B. subtilis cells have been demonstrated at the protein level. In terms of exploring cellular physiology and adaptation to environmental changes or stress, proteins showing an alteration in expression level are of primary interest. The large number of vegetative proteins identified by gel-based and gel-free approaches is a good starting point for comparative physiological investigations. For this reason a gel-free quantitation with the recently introduced iTRAQ (isobaric tagging for relative and absolute quantitation) reagent technique was performed to investigate the heat shock response in B. subtilis. A comparison with gel-based data showed that both techniques revealed a similar level of up-regulation for proteins belonging to well studied heat hock regulons (SigB, HrcA, and CtsR). However, additional datasets have been obtained by the gel-free approach indicating a strong heat sensitivity of specific enzymes involved in amino acid synthesis.

Bacillus subtilis↗

Comparative genomic and proteomic analysis reveals orthogroup structured evolution of tick protease inhibitors.

Protease inhibitors (PIs) play central roles in regulating endogenous proteolysis and host-parasite interactions in ticks. However, the evolutionary architecture underlying their diversification across tick lineages remains insufficiently resolved. Here, we performed a genome-wide comparative analysis of predicted proteomes from 14 tick species to systematically characterize PI repertoires. In total, 4931 putative PIs were identified and grouped into 20 families using the MEROPS classification system. Further, PI families such as Antistasin, WAP-type, and Pacifastin, which have not previously been systematically reported in tick genomes, were classified. Orthogroup inference demonstrated that PI expansion is structured at the level of evolutionary lineages rather than uniformly across families. By stratifying orthogroups according to duplication burden and taxonomic conservation, we identified a broadly conserved single-copy core under strong purifying selection. Motif level analysis of serpin reactive center loops further revealed conservation of inhibitory specificity within single copy orthogroups and diversification of key functional residues in duplication-associated lineages. Integration of secretion prediction and tissue-resolved proteomics from Hyalomma anatolicum and Rhipicephalus microplus demonstrated that evolutionary stratification is reflected at the protein level. Together, these findings provide an orthogroup-resolved evolutionary framework linking duplication dynamics, molecular evolution, and tissue-level protein deployment. This integrative approach offers a systematic basis for prioritizing conserved and diversified PI lineages for future functional and anti-tick intervention studies.

Animals↗