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Pilot study identifying distinct circulating proteomic profiles associated with longitudinal CT-defined fibrotic and inflammatory sarcoidosis.

INTRODUCTION: Pulmonary sarcoidosis exhibits heterogeneous clinical trajectories ranging from self-limited disease resolution to chronic progressive fibrosis, yet reliable biomarkers capable of distinguishing these disease patterns remain lacking. Whether longitudinal CT-defined sarcoidosis phenotypes are associated with distinct circulating molecular signatures remains unknown. METHODS: We performed high-throughput plasma proteomics (SomaScan 11K) in participants with pulmonary sarcoidosis classified into longitudinal chest CT-defined progressive fibrosis, progressive nodular inflammatory disease, or resolving disease trajectories, along with healthy controls. CT phenotypes were assigned based on predefined longitudinal changes in reticulation, traction bronchiectasis, nodular involvement, and mediastinal lymphadenopathy across serial CT scans. One plasma sample per participant was selected from the study visit corresponding to the CT time point at which criteria for the assigned longitudinal phenotype were met. Principal component analysis, hierarchical clustering, pathway enrichment, and correlation-based analyses linking protein expression to quantitative CT features were used to evaluate whether distinct longitudinal CT phenotypes were associated with divergent proteomic signatures. RESULTS: Principal component analysis and hierarchical clustering suggested partial segregation by CT-defined phenotype. Longitudinal CT phenotypes were associated with distinct pathway-level proteomic signatures, with progressive fibrosis enriched for epithelial-mesenchymal transition signaling, and progressive nodular inflammatory disease enriched for mTORC1, MYC, oxidative phosphorylation, adipogenesis, and fatty acid metabolism pathways. Correlation analyses showed coordinated protein-expression patterns associated with fibrotic CT features and mediastinal lymph node enlargement. DISCUSSION: These findings suggest that longitudinal CT-defined fibrotic and inflammatory sarcoidosis phenotypes are associated with distinct pathway-level proteomic signatures. This pilot study provides preliminary proof-of-concept evidence that integrating longitudinal CT imaging phenotypes with plasma proteomics may serve as a framework for future mechanistic studies and biomarker discovery in pulmonary sarcoidosis.

Humans↗

Mapping the causal chain from genetic risk variants to lipid dysmetabolism in Parkinson's disease.

The molecular pathways linking genetic variants to Parkinson's disease (PD) onset and progression remain incompletely defined; however, risk alleles in multiple genes, including GBA1, strongly implicate lipid metabolism. To systematically identify causal biomarker signatures, we analysed comprehensive metabolome profiles from blood plasma in 149 PD patients and 150 controls, along with complementary genetic, RNA-sequencing and metabolic data from other available clinical and pathologic cohorts. Using colocalization and summary-data-based Mendelian randomization, we tested whether expression and metabolic quantitative trait loci mediate the association between implicated genetic variants and PD risk. We further integrated differential metabolomics and proteomics from blood and brain to reveal pertinent mechanisms. We show that common PD risk variants at the serine palmitoyltransferase small subunit B (SPTSSB) locus, a key regulator of de novo sphingolipid biosynthesis, are associated with increased SPTSSB brain expression and elevated plasma ceramides. Additional analyses strongly support our hypothesis that a common SPTSSB causal variant is responsible for PD risk as well as the expression and metabolic quantitative trait loci. Multiple sphingolipids and fatty acid derivatives were perturbed in PD, and we identified both unique and shared features with the Alzheimer's disease metabolome. A PD acylcarnitine signature was further replicated in human post-mortem brain tissue, when comparing those with or without preclinical Lewy body pathology. Integrated analysis of complementary brain proteomic profiles revealed dysregulation of mitochondrial processes dependent on acylcarnitines, including fatty acid beta-oxidation, the tricarboxylic acid cycle and oxidative phosphorylation. Our results identify promising biomarkers and reveal a causal chain linking genetic variation to altered gene/protein expression, lipid dysmetabolism, and the manifestation of PD.

Humans↗

Differential display proteomic analysis of Picea meyeri pollen germination and pollen-tube growth after inhibition of actin polymerization by latrunculin B.

To investigate roles of the actin cytoskeleton in growth of the pollen tube of Picea meyeri, we used the actin polymerization inhibitor latrunculin B (LATB) under quantitatively controlled conditions. At low concentrations, LATB inhibited polymerization of the actin cytoskeleton in the growing pollen tube, which rapidly inhibited tip growth. The proteomic approach was used to analyse protein expression-profile changes during pollen germination and subsequent pollen-tube development with disturbed organization of the actin cytoskeleton. Two-dimensional electrophoresis and staining with Coomassie Brilliant Blue revealed nearly 600 protein spots. A total of 84 of these were differentially displayed at different hours with varying doses of LATB, and 53 upregulated or downregulated proteins were identified by mass spectrometry. These proteins were grouped into distinct functional categories including signalling, actin cytoskeleton organization, cell expansion and carbohydrate metabolism. Moreover, actin disruption affected the morphology of Golgi stacks, mitochondria and amyloplasts, along with a differential expression of proteins involved in their functions. These findings provide new insights into the multifaceted mechanism of actin cytoskeleton functions and its interaction with signalling, cell-expansion machinery and energy-providing pathways.

Actin Cytoskeleton↗

Multiplex proteomic approaches to sepsis research: case studies employing new technologies.

Sepsis is a multifactorial disease that provides unique challenges to the critical care physician. Diagnosis is hampered by the lack of a quantitative in vitro diagnostic test, instead, it relies on a series of clinical measures. The complex nature of the disease, with involvement of several physiologic systems, suggests a need to simultaneously monitor many clinical parameters. Novel proteomic technologies now exist that enable the multiplex measurement of multiple protein analytes from the same sample. Integration of these analytical measures with patient clinical data may provide the foundation for a better understanding of disease diagnosis, disease progression and the selection of optimal therapeutic regimen. The future challenge is the translation of these multiplex approaches from investigative research to clinical diagnostics for the greatest impact on patient treatment decisions.

Animals↗

Automated approach for quantitative analysis of complex peptide mixtures from tandem mass spectra.

To take advantage of the potential quantitative benefits offered by tandem mass spectrometry, we have modified the method in which tandem mass spectrum data are acquired in 'shotgun' proteomic analyses. The proposed method is not data dependent and is based on the sequential isolation and fragmentation of precursor windows (of 10 m/z) within the ion trap until a desired mass range has been covered. We compared the quantitative figures of merit for this method to those for existing strategies by performing an analysis of the soluble fraction of whole-cell lysates from yeast metabolically labeled in vivo with (15)N. To automate this analysis, we modified software (RelEx) previously written in the Yates lab to generate chromatograms directly from tandem mass spectra. These chromatograms showed improvements in signal-to-noise ratio of approximately three- to fivefold over corresponding chromatograms generated from mass spectrometry scans. In addition, to demonstrate the utility of the data-independent acquisition strategy coupled with chromatogram reconstruction from tandem mass spectra, we measured protein expression levels in two developmental stages of Caenorhabditis elegans.

Algorithms↗

Alpha tocopherol supplementation elevates plasma apolipoprotein A1 isoforms in normal healthy subjects.

Plasma alpha-tocopherol (AT) concentrations are inversely related to cardiovascular (CV) risk; however, intervention studies with AT have failed to show any consistent benefit against CV disease (CVD). Proteomics offers the opportunity to examine novel effects of AT supplementation on protein expression and therefore improve our understanding of the physiological roles of AT. Thus, to investigate the effects of AT supplementation on the plasma proteome of healthy subjects we have undertaken a double-blind, randomised, parallel design supplementation study in which healthy subjects (n = 32; 11 male and 21 female) consumed AT supplements (134 or 268 mg/day) or placebo capsules for up to 28 days. Plasma samples were obtained before supplementation and after 14 and 28 days of supplementation for analysis of changes in the plasma proteome using 2-DE and MALDI-MS. Using semiquantitative proteomics, we observed that proapolipoprotein A1 (identified by MS and Western blotting) was altered at least two-fold. Using quantitative ELISA techniques, we confirmed a significant increase in plasma apolipoprotein A1 concentration following supplementation with AT which was both time and dose dependent (p < 0.01 after 28 days supplementation with 268 mg AT/day). These data demonstrate the time and dose sensitivity of the plasma proteome to AT supplementation.

Adult↗

The molecular similarity landscape of preclinical cancer models to patient tumors.

Selecting appropriate preclinical models is fundamental for translational oncology, yet a large-scale, multi-omic quantitative comparison of their similarity to primary human tumors is lacking. To address this, we integrated transcriptomic, proteomic, and genomic profiles from over 10,000 primary tumors from The Cancer Genome Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC), alongside 4,000 preclinical models. Using a robust computational framework, we revealed a clear hierarchy of transcriptomic and proteomic similarity to patient tumors: with patient-dervied xenografts (PDXs) having greater transcriptomic and proteomic similarity to patient tumors (>) compared with patient-derived organoids (PDOs), which are equal in hierarchy to that of PDX-dervied organoids (PDXOs) > cell lines. We also quantified high molecular conservation (Pearson correlation coefficient = 0.96) across paired in vitro to in vivo platform (organoids to PDX) transitions. Furthermore, genomic analysis demonstrated that whole-exome sequencing (WES) outperforms RNA-seq in detecting DNA variants, and it identified a clonal complexity hierarchy (cell lines > PDXOs > PDXs > PDOs) reflecting the effect of passaging history on intratumor heterogeneity. Ultimately, this study delivers a comprehensive quantitative benchmark, establishing a population-level hierarchy of molecular similarity between preclinical models and primary tumors and providing a data-driven reference for model selection. These findings offer a data-driven framework for selecting models that balance biological representativeness with experimental practicality.

Humans↗

Organelle proteomics: implications for subcellular fractionation in proteomics.

Functional proteome analysis is not restricted to the sequence information but includes the broad spectrum of structural modifications and quantitative changes of proteins to which they are subjected in different tissues and cell organelles and during the development of an organism. Cell biology has provided the means required for the analysis of the composition and properties of purified cellular elements. Subcellular fractionation is an approach universal across all cell types and tissues, including cardiac and vascular system. Subcellular fractionation and proteomics form an ideal partnership when it comes to enrichment and analysis of intracellular organelles and low abundant multiprotein complexes. Subcellular fractionation is a flexible and adjustable approach resulting in reduced sample complexity and is most efficiently combined with high-resolution 2D gel/mass spectrometry analysis as well as with gel-independent techniques. In this study we introduce state of the art subcellular fractionation techniques and discuss their suitability, advantages, and limitations for proteomics research.

Animals↗

Proteomic consequences of a human mitochondrial tRNA mutation beyond the frame of mitochondrial translation.

Numerous severe neurodegenerative and neuromuscular disorders, characterized biochemically by strong perturbations in energy metabolism, are correlated with single point mutations in mitochondrial genes coding for transfer RNAs. Initial comparative proteomics performed on wild-type and Myoclonic Epilepsy and Ragged Red Fibers (MERRF) mitochondria from sibling human cybrid cell lines revealed the potential of this approach. Here a quantitative analysis of several hundred silver-stained spots separated by two-dimensional gel electrophoresis was performed in the specific case of a couple of mitochondria, containing or not mutation A8344G in the gene for mitochondrial tRNALys, correlated with MERRF syndrome. Computer-assisted analysis allowed us to detect 38 spots with significant quantitative variations, of which 20 could be assigned by mass spectrometry. These include nuclear encoded proteins located in mitochondria such as respiratory chain subunits, metabolic enzymes, a protein of the mitochondrial translation machinery, and cytosolic contaminants. Furthermore, Western blotting combined with mass spectrometry revealed the occurrence of numerous isoforms of pyruvate dehydrogenase subunits, with subtle changes in post-translational modifications. This comparative proteomic approach gives the first insight for nuclear encoded proteins that undergo the largest quantitative changes, and pinpoints new potential molecular partners involved in the cascade of events that connect genotype to phenotype.

Humans↗

A fluorescent natural product for ultra sensitive detection of proteins in one-dimensional and two-dimensional gel electrophoresis.

Lightning Fast is a sensitive fluorescence-based stain for detecting proteins in one-dimensional and two-dimensional polyacrylamide electrophoresis gels. It contains the fluorophore epicocconone from the fungus Epicoccum nigrum that interacts noncovalently with sodium dodecyl sulfate and protein. Stained proteins can be excited optimally by near-ultraviolet light of about 395 nm or with visible light of about 520 nm. The stain can be excited using a range of sources used in image analysis systems including UVA (ca. 365 nm) and UVB (ca. 302 nm) transilluminators; Xenon-arc lamps; 488 nm and 457 nm Argon-ion lasers; 473 nm and 532 nm neodymium: yttrium aluminum garnet (Nd:YAG) solid-state lasers; 543 nm helium-neon lasers, and emerging violet, blue and green diode lasers. Maximum fluorescence emission of the dye is at approximately 610 nm. The limit of detection in one-dimensional gels stained with Lightning Fast protein gel stain is less than 100 pg of protein, rivaling the current limits of matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). Lightning Fast was found to be considerably more sensitive than SYPRO Ruby, SYPRO Orange, silver and Coomassie Brilliant Blue G-250 in matched experiments. Staining takes as little as 3.5 h and stained proteins displayed quantitative linearity over more than four orders of magnitude, thereby allowing visualization of entire proteomes. Lightning Fast protein gel staining is compatible with subsequent peptide mass fingerprinting using MALDI-MS and Edman-based sequencing chemistry.

Animals↗

A high-performance liquid chromatography method for determining transition metal content in proteins.

Transition metals are common components of cellular proteins and the detailed study of metalloproteins necessitates the identification and quantification of bound metal ions. Screening for metals is also an informative step in the initial characterization of the numerous unknown and unclassified proteins now coming through the proteomic pipeline. We have developed a high-performance liquid chromatography method for the quantitative determination of the most prevalent biological transition metals: manganese, iron, cobalt, nickel, copper, and zinc. The method is accurate and simple and can be adapted for automated high-throughput studies. The metal analysis involves acid hydrolysis to release the metal ions into solution, followed by ion separation on a mixed-bead ion-exchange column and absorbance detection after postcolumn derivatization with the metallochromic indicator 4-(2-pyridylazo)resorcinol. The potential interferences by common components of protein solutions were investigated. The metal content of a variety of metalloproteins was analyzed and the data were compared to data obtained from inductively coupled plasma-atomic emission spectroscopy. The sensitivity of the assay allows for the detection of 0.1-0.8 nmol, depending on the metal. The amount of protein required is governed by the size of the protein and the fraction of protein with metal bound. For routine analysis 50 microg was used but for many proteins 10 microg would be sufficient. The advantages, disadvantages, and possible applications of this method are discussed.

Animals↗

Biological rhythmicity in expressed proteins of the marine dinoflagellate Lingulodinium polyedrum demonstrated by chronological proteomics.

The dinoflagellate Lingulodinium polyedrum shows circadian expression of proteins. Analysis of the expression profile of ca. 900 proteins (pI range 5-8; MW 22,000-120,000) by chronological proteomics in 12:12h light-dark ('day-night') cycles revealed 28 with quantitative circadian changes. The patterns were classified into three types: Phase 1 ('evening'), Phase 2 ('night'), and Phase 3 ('midnight'). Peptide mass fingerprinting identified luciferin-binding protein in Phase 2 and two components of the tricarboxylic acid cycle in Phases 1 and 2. Thus, rhythmicity appears to be related to physiological states and to control the metabolic pathway in L. polyedrum.

Animals↗

Protein microarrays and multiplexed sandwich immunoassays: what beats the beads?

Protein microarray technology allows the simultaneous determination of a large variety of parameters from a minute amount of sample within a single experiment. Assay systems based on this technology are currently applied for the identification, quantitation and functional analysis of proteins. Protein microarray technology is of major interest for proteomic research in basic and applied biology as well as for diagnostic applications. Miniaturized and parallelized assay systems have reached adequate sensitivity and hence have the potential to replace singleplex analysis systems. However, robustness and automation needs to be demonstrated before this technology will finally prove suitable for high-throughput applications. Miniaturized and parallelized sandwich immunoassays are the most advanced assays formats among the different protein microarray applications. Multiplexed sandwich immunoassays can be used for the identification of biomarkers and the validation of potential target molecules. In this review an overview will be given on the current stage of protein microarray technology with a special focus on miniaturized multiplexed sandwich immunoassays.

Automation↗

An Integrated Proteomics and Genomics Approach to Identify Essential Protein Kinases During Human Trophoblast Development.

In the developing human placenta, three subtypes of trophoblast cells, cytotrophoblasts (CTBs), extravillous trophoblasts (EVTs), and syncytiotrophoblasts (STBs), mediate critical functions essential for a successful pregnancy. CTBs constitute the stem/progenitor compartment and differentiate into STBs and EVTs within the floating and anchoring villi, respectively. STBs establish the maternal-fetal exchange interface and secrete human chorionic gonadotropin (hCG), a hormone vital for the maintenance of early pregnancy. EVTs anchor the maternal endometrium and invade the uterine tissue to remodel maternal cells, supporting implantation and progression of pregnancy. In this study, we used human trophoblast stem cells (hTSCs) as a model system and performed quantitative, label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) to profile the proteome and phosphoproteome in TSC stem state (analogous to undifferentiated CTBs) and following their differentiation to STBs and EVTs. Through a multiomics approach, we integrated our proteomics data with global gene expression profiles to correlate cell-type specific gene and protein expression during human trophoblast development. We also identified global phosphoproteome and analyzed kinases that are specifically active in hTSC stem state, as well as in differentiated STBs and EVTs. We experimentally validated specific kinases, such as BUB1B, PAK6, PKYMT1, and TNIK, that are essential for maintaining the hTSC stem-state. Additionally, atypical protein kinase C isoforms PKC&#x3b6; are essential for STB development, whereas PTK2B, SRC, TRIO, and LYN are important for EVT development. Our findings highlight key kinases uniquely required for specific stages of trophoblast development during human placentation and suggest that pharmacological inhibition of these kinases could negatively impact the placentation process during pregnancy.

Humans↗

Mitochondrial proteome: altered cytochrome c oxidase subunit levels in prostate cancer.

Laser capture microdissection was combined with reverse phase protein lysate arrays to quantitatively analyze the ratios of mitochondrial encoded cytochrome c oxidase subunits to nuclear encoded cytochrome c oxidase subunits, and to correlate the ratios with malignant progression in human prostate tissue specimens. Cytochrome c oxidase subunits I-III comprise the catalytic core of the enzyme and are all synthesized from mitochondrial DNA. The remaining subunits (IV-VIII) are synthesized from cellular nuclear DNA. A significant (P < 0.001, 30/30 prostate cases) shift in the relative concentrations of nuclear encoded cytochrome c oxidase subunits IV, Vb, and VIc compared to mitochondrial encoded cytochrome c oxidase subunits I and II was noted during the progression of prostate cancer from normal epithelium through premalignant lesions to invasive carcinoma. Significantly, this shift was discovered to begin even in the premalignant stage. Reverse phase protein lysate array-based observations were corroborated with immunohistochemistry, and extended to a few human carcinomas in addition to prostate. This analysis points to a role for nuclear DNA encoded mitochondrial proteins in carcinogenesis; underscoring their potential as targets for therapy while highlighting the need for full characterization of the mitochondrial proteome.

Blotting, Western↗

A proteomic study of serum from children with autism showing differential expression of apolipoproteins and complement proteins.

Modern methods that use systematic, quantitative and unbiased approaches are making it possible to discover proteins altered by a disease. To identify proteins that might be differentially expressed in autism, serum proteins from blood were subjected to trypsin digestion followed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) on time-of-flight (TOF) instruments to identify differentially expressed peptides. Children with autism 4-6 years of age (n=69) were compared to typically developing children (n=35) with similar age and gender distributions. A total of 6348 peptide components were quantified. Of these, five peptide components corresponding to four known proteins had an effect size >0.99 with a P<0.05 and a Mascot identification score of 30 or greater for autism compared to controls. The four proteins were: Apolipoprotein (apo) B-100, Complement Factor H Related Protein (FHR1), Complement C1q and Fibronectin 1 (FN1). In addition, apo B-100 and apo A-IV were higher in children with high compared to low functioning autism. Apos are involved in the transport of lipids, cholesterol and vitamin E. The complement system is involved in the lysis and removal of infectious organisms in blood, and may be involved in cellular apoptosis in brain. Despite limitations of the study, including the low fold changes and variable detection rates for the peptide components, the data support possible differences of circulating proteins in autism, and should help stimulate the continued search for causes and treatments of autism by examining peripheral blood.

Apolipoproteins↗

Integrated molecular signature of disease: analysis of influenza virus-infected macaques through functional genomics and proteomics.

Recent outbreaks of avian influenza in humans have stressed the need for an improved nonhuman primate model of influenza pathogenesis. In order to further develop a macaque model, we expanded our previous in vivo genomics experiments with influenza virus-infected macaques by focusing on the innate immune response at day 2 postinoculation and on gene expression in affected lung tissue with viral genetic material present. Finally, we sought to identify signature genes for early infection in whole blood. For these purposes, we infected six pigtailed macaques (Macaca nemestrina) with reconstructed influenza A/Texas/36/91 virus and three control animals with a sham inoculate. We sacrificed one control and two experimental animals at days 2, 4, and 7 postinfection. Lung tissue was harvested for pathology, gene expression profiling, and proteomics. Blood was collected for genomics every other day from each animal until the experimental endpoint. Gross and microscopic pathology, immunohistochemistry, viral gene expression by arrays, and/or quantitative real-time reverse transcription-PCR confirmed successful yet mild infections in all experimental animals. Genomic experiments were performed using macaque-specific oligonucleotide arrays, and high-throughput proteomics revealed the host response to infection at the mRNA and protein levels. Our data showed dramatic differences in gene expression within regions in influenza virus-induced lesions based on the presence or absence of viral mRNA. We also identified genes tightly coregulated in peripheral white blood cells and in lung tissue at day 2 postinoculation. This latter finding opens the possibility of using gene expression arrays on whole blood to detect infection after exposure but prior to onset of symptoms or shedding.

Animals↗

Direct visualization of serine hydrolase activities in complex proteomes using fluorescent active site-directed probes.

The field of biochemistry is currently faced with the enormous challenge of assigning functional significance to more than thirty thousand predicted protein products encoded by the human genome. In order to accomplish this daunting task, methods will be required that facilitate the global analysis of proteins in complex biological systems. Recently, methods have been described for simultaneously monitoring the activity of multiple enzymes in crude proteomes based on their reactivity with tagged chemical probes. These activity based probes (ABPs) have used either radiochemical or biotin/avidin-based detection methods to allow consolidated visualization of numerous enzyme activities. Here we report the synthesis and evaluation of fluorescent activity based probes for the serine hydrolase super-family of enzymes. The fluorescent methods detailed herein provide superior throughput, sensitivity, and quantitative accuracy when compared to previously described ABPs, and provide a straight-forward platform for high-throughput proteome analysis.

Animals↗