Linking gender-specific differences to the molecular etiology of obesity has been largely based on genomic and transcriptomic evidence lacking endophenotypic insight and is not applicable to the extracellular fluid compartments, or the milieu intérieur, of the human body. To address this need, this study profiled the whole serum proteomes of age-matched nondiabetic overweight and obese females (n = 28) and males (n = 31) using a multiplex design with pooled biological and technical replicates. To bypass basic limitations of immunodepletion-based strategies, subproteome enrichment by size-exclusion chromatography (SuPrE-SEC) followed by iTRAQ 2D-LC-nESI-FTMS analysis was used. The study resulted in the reproducible analysis of 2472 proteins (peptide FDR < 5%, q < 0.05). A total of 248 proteins exhibited significant modulation between men and women (p < 0.05) that mapped to pathways associated with ?-estradiol, lipid and prostanoid metabolism, vitamin D function, immunity/inflammation, and the complement and coagulation cascades. This novel endophenotypic signature of gender-specific differences in whole serum confirmed and expanded the results of previous physiologic and pharmacologic studies exploring sexual dimorphism at the genomic and transcriptomic level in tissues and cells. Conclusively, the multifactorial and pleiotropic nature of human obesity exhibits sexual dimorphism in the circulating proteome of importance to clinical study design.
Cellular proteomics is becoming a widespread clinical application, matching the definition of bench-to-bedside translation. Among various fields of investigation, this approach can be applied to the study of the metabolic alterations that accompany oncogenesis and tumor progression, which are globally referred to as oncometabolism. Here, we describe a multidimensional protein identification technology (MuDPIT)-based strategy that can be employed to study the cellular proteome of malignant cells and tissues. This method has previously been shown to be compatible with the reproducible, in-depth analysis of up to a thousand proteins in clinical samples. The possibility to employ this technique to study clinical specimens demonstrates its robustness. MuDPIT is advantageous as compared to other approaches because it is direct, highly sensitive, and reproducible, it provides high resolution with ultra-high mass accuracy, it allows for relative quantifications, and it is compatible with multiplexing (thus limiting costs).This method enables the direct assessment of the proteomic profile of neoplastic cells and tissues and could be employed in the near future as a high-throughput, rapid, quantitative, and cost-effective screening platform for clinical samples.
Muscle lim protein (MLP) has emerged as a critical regulator of striated muscle physiology and pathophysiology. Mutations in cysteine and glycine-rich protein 3 (CSRP3), the gene encoding MLP, have been directly associated with human cardiomyopathies, whereas aberrant expression patterns are reported in human cardiac and skeletal muscle diseases. Increasing evidence suggests that MLP has an important role in both myogenic differentiation and myocyte cytoarchitecture, although the full spectrum of its intracellular roles has not been delineated. We report the discovery of an alternative splice variant of MLP, designated as MLP-b, showing distinct expression in neuromuscular disease and direct roles in actin dynamics and muscle differentiation. This novel isoform originates by alternative splicing of exons 3 and 4. At the protein level, it contains the N-terminus first half LIM domain of MLP and a unique sequence of 22 amino acids. Physiologically, it is expressed during early differentiation, whereas its overexpression reduces C2C12 differentiation and myotube formation. This may be mediated through its inhibition of MLP/cofilin-2-mediated F-actin dynamics. In differentiated striated muscles, MLP-b localizes to the sarcomeres and binds directly to Z-disc components, including ?-actinin, T-cap and MLP. The findings of the present study unveil a novel player in muscle physiology and pathophysiology that is implicated in myogenesis as a negative regulator of myotube formation, as well as in differentiated striated muscles as a contributor to sarcomeric integrity.
We report the Laser Induced Forward Transfer (LIFT) of antibodies from a liquid donor film onto paper receivers for application as point-of-care diagnostic sensors. To minimise the loss of functionality of the active biomolecules during transfer, a dynamic release layer was employed to shield the biomaterial from direct exposure to the pulsed laser source. Cellulose paper was chosen as the ideal receiver because of its inherent bio-compatibility, liquid transport properties, wide availability and low cost, all of which make it an efficient and suitable platform for point-of-care diagnostic sensors. Both enzyme-tagged and untagged IgG antibodies were LIFT-printed and their functionality was confirmed via a colorimetric enzyme-linked immunosorbent assay. Localisation of the printed antibodies was exhibited, which can allow the creation of complex 2-d patterns such as QR codes or letters for use in a final working device. Finally, a calibration curve was determined that related the intensity of the colour obtained to the concentration of active antibodies to enable quantitative assessment of the device performance. The motivation for this work was to implement a laser-based procedure for manufacturing low-cost, point-of-care diagnostic devices on paper.
Recent evidence suggests that specific extracellular ?-synuclein (?-syn) strains are implicated in the progression of Parkinson's disease (PD) pathology. It is plausible that deregulation in the normal processing of secreted ?-syn may be a causative risk factor for PD. To date, the degradation mechanisms involved have received very little attention. Here, we sought to investigate factors that regulate extracellular ?-syn levels. We show, for the first time, that cell-secreted ?-syn forms are resistant to direct proteolysis by kallikrein-related peptidase 6 (KLK6), an extracellular enzyme known to cleave recombinant ?-syn. This differential susceptibility appears to be partially due to the association of secreted ?-syn with lipids. We further provide evidence that secreted ?-syn can be cleaved by KLK6 indirectly through activation of a secreted metalloprotease, suggestive of the involvement of a proteolytic cascade in the catabolism of secreted ?-syn. Our results clearly suggest that physiological modifications affect the biochemical behavior of secreted ?-syn and provide novel insights into mechanisms and potential targets for therapeutic interventions.-Ximerakis, M., Pampalakis, G., Roumeliotis, T. I., Sykioti, V.-S., Garbis, S. D., Stefanis, L., Sotiropoulou, G., Vekrellis, K. Resistance of naturally secreted ?-synuclein to proteolysis.
Despite intense global efforts, no new clinical and/or viable biomarkers have been established to overcome the limitation of the prostate specific antigen in the early diagnosis and prognosis of prostate cancer (PCa). The current proteomic approaches to PCa biomarker discovery, each have distinct advantages and disadvantages, yet when combined hold real promise in the coming years. One key approach to this effort is the development of non-targeted, depletion-free and quantitative liquid chromatography-ultra high resolution tandem mass spectrometry (LC-MS) pipelines for the systems-wide interrogation of the diverse proteomes encompassed in whole tissue and blood serum or plasma. Derived quantitative proteomes can be decoded for their biomedical relevance with advanced bioinformatics and bibliographic mining to yield promising molecular portraits that can gauge prostatic disease at the serological level. Their functional annotation, although potentially useful, is beyond our current level of biological understanding and should not be requisite for their effective use in the clinical monitoring of prostatic disease.
The ThinPrep cervical smear is widely used in clinical practice for the cytological and molecular screening against abnormal cells and Human Papillomavirus (HPV) infection. Current advancements made to LC-MS proteomics include the use of stable isotope labeling for the in-depth analysis of proteins in complex clinical specimens. Such approaches have yet to be realized for ThinPrep clinical specimens. In this study, an LC-MS method based on isobaric (iTRAQ) labeling and high-resolution FT-Orbitrap mass spectrometry was used for the proteomic analysis of 23 human ThinPrep smear specimens. Tandem mass spectrometry analysis was performed with both nitrogen high collision dissociation (HCD MS/MS) and helium collision induced dissociation (CID MS/MS) peptide fragmentation modes. The analysis of three 8-plex sample sets yielded the identification of over 3200 unique proteins at FDR < 1%, of which over 2300 proteins were quantitatively profiled in at least one of the three experiments. The interindividual variability served to define the required sample size needed to identify significant protein expression differences. The degree of in-depth proteome coverage allowed the detection of 6 HPV-derived proteins including the high-risk HPV16 type in the specimens tested. The presence of the HPV strains of origin was also confirmed with PCR-hybridization molecular methods. This proof-of-principle study constitutes the first ever report on the nontargeted analysis of HPV proteins in human ThinPrep clinical specimens with high-resolution mass spectrometry. A further testament to the sensitivity and selectivity of the proposed study method was the confident detection of a significant number of phosphopeptides in these specimens.
A naturally occurring benzofuran derivative, Ebenfuran III (Eb III), was investigated for its antiproliferative effects using the DU-145 prostate cell line. Eb III was isolated from Onobrychis ebenoides of the Leguminosae family, a plant endemic in Central and Southern Greece. We have previously reported that Eb III exerts significant cytotoxic effects on certain cancer cell lines. This effect is thought to occur via the isoprenyl moiety at the C-5 position of the molecule. The study aim was to gain a deeper understanding of the pharmacological effect of Eb III on DU-145 cell death at the translational level using a relative quantitative and temporal proteomics approach. Proteins extracted from the cell pellets were subjected to solution phase trypsin proteolysis followed by iTRAQ-labeling. The labeled tryptic peptide extracts were then fractionated using strong cation exchange chromatography and the fractions were analyzed by nanoflow reverse phase ultraperformance liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry analysis using a hybrid QqTOF platform. Using this approach, we compared the expression levels of 1360 proteins analyzed at ?1% global protein false discovery rate (FDR), commonly present in untreated (control, vehicle only) and Eb III-treated cells at the different exposure time points. Through the iterative use of Ingenuity Pathway Analysis with hierarchical clustering of protein expression patterns, followed by bibliographic research, the temporal regulation of the Calpain-1, ERK2, PAR-4, RAB-7, and Bap31 proteins were identified as potential nodes of multipathway convergence to Eb III induced DU-145 cell death. These proteins were further verified with Western blot analysis. This gel-free, quantitative 2DLC-MS/MS proteomics method effectively captured novel modulated proteins in the DU-145 cell line as a response to Eb III treatment. This approach also provided greater insight to the multifocal and combinatorial signaling pathways implicated in Eb III-induced cell death.
Proteomics profiling of intact proteins based on MALDI-TOF MS and derived platforms has been used in cancer biomarker discovery studies. This approach suffers from a number of limitations such as low resolution, low sensitivity, and that no knowledge is available on the identity of the respective proteins in the discovery mode. Nevertheless, it remains the most high-throughput, untargeted mode of clinical proteomics studies to date. Here we compare key protein separation and MS techniques available for protein biomarker identification in this type of studies and define reasons of uncertainty in protein peak identity. As a result of critical data analysis, we consider 3D protein separation and identification workflows as optimal procedures. Subsequently, we present a new protocol based on 3D LC-MS/MS with top-down at high resolution that enabled the identification of HNRNP A2/B1 intact peptide as correlating with the estrogen receptor expression in breast cancer tissues. Additional development of this general concept toward next generation, top-down based protein profiling at high resolution is discussed.
We fabricated a TiO(2)-ZrO(2) affinity chromatography micro-column on 2 mm PMMA plates, and demonstrated the enrichment and separation of (a) a standard mono- and tetra-phosphopeptide, and (b) phosphopeptides contained in a tryptic digest of ?-Casein. The chromatography column consisted of 32 parallel microchannels with common input and output ports and was fabricated by lithography directly on the polymeric substrate followed by plasma etching (i.e. standard MEMS processing) and sealed with lamination. The liquid deposited TiO(2)-ZrO(2) stationary phase was characterized by X-ray diffraction and was found to be mostly TiO(2) and ZrO(2) in crystalline phases. Off-chip UV detection and MALDI MS identification of the separated effluents were used. The chip had a capacity of >1.4 ?g (0.7 nmol) of a prototype mono-phosphopeptide and a recovery of 94 ± 3%, and can be used with small samples (less than 0.1 ?L depending on the syringe pump used). The chip design allows an expansion of its capacity by means of increasing the number of parallel microchannels at a constant sample volume. Our approach provided an alternative to off-line extraction tips (with typical capacities of 1-2 ?g and sample volumes of 1-10 ?L), and to on-chip efforts based on packed bed and frit formats.
The current proof-of-principle study was aimed toward development of a novel multidimensional protein identification technology (MudPIT) approach for the in-depth proteome analysis of human serum derived from patients with benign prostate hyperplasia (BPH) using rational chromatographic design principles. This study constituted an extension of our published work relating to the identification and relative quantification of potential clinical biomarkers in BPH and prostate cancer (PCa) tissue specimens. The proposed MudPIT approach encompassed the use of three distinct yet complementary liquid chromatographic chemistries. High-pressure size-exclusion chromatography (SEC) was used for the prefractionation of serum proteins followed by their dialysis exchange and solution phase trypsin proteolysis. The tryptic peptides were then subjected to offline zwitterion-ion hydrophilic interaction chromatography (ZIC-HILIC) fractionation followed by their online analysis with reversed-phase nano-ultraperformance chromatography (RP-nUPLC) hyphenated to nanoelectrospray ionization-tandem mass spectrometry using an ion trap mass analyzer. For the spectral processing, the sequential use of the SpectrumMill, Scaffold, and InsPecT software tools was applied for the tryptic peptide product ion MS(2) spectral processing, false discovery rate (FDR) assessment, validation, and protein identification. This milestone serum analysis study allowed the confident identification of over 1955 proteins (p ? 0.05; FDR ? 5%) with a broad spectrum of biological and physicochemical properties including secreted, tissue-specific proteins spanning approximately 12 orders of magnitude as they occur in their native abundance levels in the serum matrix. Also encompassed in this proteome was the confident identification of 375 phosphoproteins (p ? 0.05; FDR ? 5%) with potential importance to cancer biology. To demonstrate the performance characteristics of this novel MudPIT approach, a comparison was made with the proteomes resulting from the immunodepletion of the high abundant albumin and IgG proteins with offline first dimensional tryptic peptide separation with both ZIC-HILIC and strong cation exchange (SCX) chromatography and their subsequent online RP-nUPLC-nESI-MS(2) analysis.
alpha-Synuclein is central in Parkinsons disease pathogenesis. Although initially alpha-synuclein was considered a purely intracellular protein, recent data suggest that it can be detected in the plasma and CSF of humans and in the culture media of neuronal cells. To address a role of secreted alpha-synuclein in neuronal homeostasis, we have generated wild-type alpha-synuclein and beta-galactosidase inducible SH-SY5Y cells. Soluble oligomeric and monomeric species of alpha-synuclein are readily detected in the conditioned media (CM) of these cells at concentrations similar to those observed in human CSF. We have found that, in this model, alpha-synuclein is secreted by externalized vesicles in a calcium-dependent manner. Electron microscopy and liquid chromatography-mass spectrometry proteomic analysis demonstrate that these vesicles have the characteristic hallmarks of exosomes, secreted intraluminar vesicles of multivesicular bodies. Application of CM containing secreted alpha-synuclein causes cell death of recipient neuronal cells, which can be reversed after alpha-synuclein immunodepletion from the CM. High- and low-molecular-weight alpha-synuclein species, isolated from this CM, significantly decrease cell viability. Importantly, treatment of the CM with oligomer-interfering compounds before application rescues the recipient neuronal cells from the observed toxicity. Our results show for the first time that cell-produced alpha-synuclein is secreted via an exosomal, calcium-dependent mechanism and suggest that alpha-synuclein secretion serves to amplify and propagate Parkinsons disease-related pathology.
BDNF plays a key role in neuronal development, in short- and long-term changes in synaptic activity, and in neuronal survival. These effects are mediated, to a great extent, by changes in protein synthesis. We conducted a gel-based proteome profiling of the long-term (12 h) effects of BDNF in cultured hippocampal neurons. BDNF changed the abundance of proteins involved in (i) Nucleobase, nucleoside, nucleotide and nucleic acid metabolism, (ii) protein metabolism, (iii) carbohydrate metabolism, (iv) regulators of apoptosis, and (v) regulators of cell proliferation. A large majority of the identified proteins involved in translation activity were upregulated, but not all changes in the protein content were correlated with alterations in the corresponding mRNA. The upregulation of Seryl-aminoacyl-tRNA-synthetase and Eef2 was sensitive to the mTOR inhibitor rapamycin, as determined by Western blot. Since the mRNAs for proteins involved in translation represent a large fraction of the diversity of dendritic mRNAs, we investigated the effect of BDNF on the distribution of the transcripts in the soma versus neurite compartments. The increase in mRNA for proteins of the translation machinery in the soma was differentially coupled with the upregulation of neurite transcripts. BDNF also downregulated specific mRNAs in neurite compartments suggesting that the neurotrophin may act by regulating mRNA stability and thereby affecting the dendritic protein content.
The cis/trans isomerization of the peptide bond preceding proline is an intrinsically slow process, although important in many biological processes in both prokaryotes and eukaryotes. In vivo, this isomerization is catalyzed by peptidyl-prolyl cis/trans-isomerases (PPIases). Here, we present the molecular and biochemical characterization of parvulin-type PPIase family members of the model legume Lotus japonicus, annotated as LjPar1, LjPar2, and LjPar3. Although LjPar1 and LjPar2 were found to be homologous to PIN1 (Protein Interacting with NIMA)-type parvulins and hPar14 from human, respectively, LjPar3 represents a novel multidomain parvulin, apparently present only in plants, that contains an active carboxyl-terminal sulfurtransferase domain. All Lotus parvulins were heterologously expressed and purified from Escherichia coli, and purified protein verification measurements used a liquid chromatography-mass spectrometry-based proteomic method. The biochemical characterization of the recombinant Lotus parvulins revealed that they possess PPIase activity toward synthetic tetrapeptides, although they exhibited different substrate specificities depending on the amino acid amino terminal to proline. These differences were also studied in a structural context using molecular modeling of the encoded polypeptides. Real-time reverse transcription-polymerase chain reaction revealed that the three parvulin genes of Lotus are ubiquitously expressed in all plant organs. LjPar1 was found to be up-regulated during the later stages of nodule development. Subcellular localization of LjPar-enhanced Yellow Fluorescence Protein (eYFP) fusions expressed in Arabidopsis (Arabidopsis thaliana) leaf epidermal cells revealed that LjPar1- and LjPar2-eYFP fusions were localized in the cytoplasm and in the nucleus, in contrast to LjPar3-eYFP, which was clearly localized in plastids. Divergent substrate specificities, expression profiles, and subcellular localization indicate that plant parvulin-type PPIases are probably involved in a wide range of biochemical and physiological processes.
The present pilot study constitutes a proof-of-principle in the use of a quantitative LC-MS/MS based proteomic method for the comparative analysis of representative low-grade breast primary tumor tissues with and without metastases and metastasis in lymph node relative to the nonmetastatic tumor type. The study method incorporated iTRAQ stable isotope labeling, two-dimensional liquid chromatography, nanoelectrospray ionization and high resolution tandem mass spectrometry using the hybrid QqTOF platform (iTRAQ-2DLC-MS/MS). The principal aims of this study were (1) to define the protein spectrum obtainable using this approach, and (2) to highlight potential candidates for verification and validation studies focused on biomarkers involved in metastatic processes in breast cancer. The study resulted in the reproducible identification of 605 nonredundant proteins (p < or = 0.05). A quantitative comparison revealed 3/3 proteins with significantly increased/decreased level in metastatic primary tumor and 13/6 proteins with increased/decreased level in lymph node metastasis compared to nonmetastatic primary tumor (p < 0.01). Changes in selected differentially expressed proteins were verified with qRT-PCR. Although our pilot scale study does not warrant general biological conclusions, the synergic regulation of some proteins with related function (e.g., heme binding proteins, proteins of energetic metabolism, interferon induced proteins, proteins with adhesive function) determined in our sample set reflects the ability of our method in providing biologically meaningful data. The main conclusion from this pilot study was that our quantitative proteomic method constitutes a novel way of analyzing cancerous breast tissue biopsy samples that can be extended as part of a larger scale biomarker discovery program.
The different steps of a proteomics analysis workflow generate a plethora of features for each extracted proteomic object (a protein spot in 2D gel electrophoresis (2-DE), or a peptide peak in liquid chromatography-mass spectrometry (LC-MS) analysis). Yet, the joint visualization of multiple object features on 2D gel-like maps is rather limited in currently available proteomics software packages. We introduce a new, simple, and intuitive visualization method that utilizes spheres to represent proteomic objects on proteomic feature maps, and exploits the spheres size and color to provide simultaneous visualization of user-selected feature pairs. Our contribution, a unified and flexible visualization mechanism that can be easily applied at any stage of a 2-DE or a LC-MS based differential proteomics study, is demonstrated and discussed using five representative scenarios. The joint visualization of proteomic object features and their spatial distribution is a powerful tool for inspecting and comparing the proteomics analysis results, attracting the users attention to useful information, such as differential expression trends and patterns, and even assisting in the evaluation and refinement of a proteomics experiment.
The ability to predict mode, as well as risk, of death in left ventricular systolic dysfunction (LVSD) is important, as the clinical and cost-effectiveness of implantable cardioverter defibrillators (ICD) therapy depends on its use in appropriately selected patient populations. The value of a proteomic approach in identifying prognostic biomarkers in LVSD is unknown. The aims of this pilot study were to use proteomic techniques to identify serum biomarkers associated with LVSD and to prospectively explore their association with prognosis.
Whats known on the subject? and What does the study add? The use of biomarkers to detect a cancer early, especially prostate cancer, is not a new idea and PSA has been proved to be the best biomarker for the early diagnosis of prostate cancer. Since the introduction and wide use of PSA various efforts have been made to find novel biomarkers in both serum and urine of individuals at high risk for prostate cancer. The best example of a biomarker detected in the urine after a vigorous digital rectal examination is PCA3, which is used mainly in the subgroup of patients with PSA 4-10 ng/mL whose prostate biopsy was repeatedly negative for prostate cancer in order to decide the performance or not of a new biopsy. Proteomics is a state of the art new biotechnology used to identify the proteome of a certain tissue meaning the whole group of proteins related to the anatomy and biochemistry of the tissue. Using proteomics can effectively and more specifically identify proteins that can be used as potential biomarkers for the early diagnosis of prostate cancer. Zinc ?2-glycoprotein has been studied in the past as a protein related to cancer cachexia and it has been measured in both prostate tissue and serum in patients with prostate cancer. Zinc ?2-glycoprotein has also been recently identified by proteomics in prostate tissue showing different values in patients with prostate cancer and benign prostate hyperplasia. It is the first time that zinc ?2-glycoprotein has been systematically measured and studied in an easily obtained biological fluid such as urine showing a very optimistic potential both as a novel solo biomarker and as an adjunct to PSA for the early diagnosis of prostate cancer. PSA has revolutionized the way we approximate prostate cancer diagnosis. Even though PSA is still the best biomarker for the diagnosis of prostate cancer it constitutes an organ-specific and not a disease-specific biomarker and diagnostic dilemmas are often raised concerning the performance or not of a prostate biopsy. Thus novel biomarkers are required in order to improve the diagnostic ability of PSA. Increasingly in the literature it is stated that the future of prostate cancer diagnosis could be not a single biomarker but a band of different biomarkers that as a total could give the possibility of an individual having prostate cancer. By detecting and measuring zinc ?2-glycoprotein in the urine we believe that interesting conclusions can be made: first that proteomics is the way to detect with accuracy proteins that could be proved to be valuable novel biomarkers; second that zinc ?2-glycoprotein detected in the urine could be used both as a solo biomarker and as an adjunct to PSA for the early diagnosis of prostate cancer.
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