Filter-aided Sample Preparation Research Articles

#1978 Proteomic analysis of exosomes derived from mesangial cells treated with galactose-deficient IgA1

Abstract Background and Aims IgA nephropathy (IgAN) is an autoimmune disease characterized by IgA deposits that build up in the kidneys, inflame and damage glomeruli causing hematuria and proteinuria. It is a leading cause of chronic kidney disease, which often results in end-stage kidney disease. There is no disease specific treatment for IgAN. The glomerulus, in which IgA1 lacking galactose residues (gdIgA1) are deposited, consists of mesangial cells, podocytes, and endothelial cells. Crosstalk between the cell types allows the glomerulus to act as a unit and react to its dynamic environment. There is very little evidence on mesangial cell derived exosomes and their cargo to understand the pathological crosstalk signaling in the glomerulus of IgAN. We isolated exosomes from mesangial cells that were treated with patient-derived gdIgA1 and IgA1 complexes. Proteomic analysis was performed to identify the exosome cargo and delineate the signaling pathways leading to maladaptive paracrine crosstalk. From our study, we aim to understand the molecular targets for therapeutic strategies in IgAN. Method Human mesangial cells were treated with/without IgA1, gdIgA1 or IgG for 24 h. Cell culture supernatant was collected for exosome isolations. Exosomes were analyzed by size, morphology and number using TEM and NanoFCM. Exosome protein extracts were processed for LC-Tandem mass spectrometry analysis using filter-aided sample preparation protocol. Proteomic analysis was performed using Qlucore omics explorer and pathway analysis using Ingenuity Pathway Analysis (IPA). Exosome marker expressions such as CD63, CD81 and FLOT1 and proteome validation was performed using Western blotting. Statistical analysis was performed using GraphPad Prism and values <0.05 were considered significant. Results We confirmed the release of exosomes by mesangial cells in response to IgA1/gdIgA1 complexes. Exosomes were fewer in unstimulated cells as compared to IgA1/gdIgA1 treated cells. They showed round morphology with a dense core and uniform size distribution. Exosomes from treated cells showed a mean size of about 75 nm and concentration in the range of 1-2 × 10^10 particles/ml. While untreated cells showed a mean size of about 100 nm and concentration of about 1 × 10^9 particles/ml. We confirmed the protein expression of exosome markers such as CD63, CD81 and FLOT1. For the first time, we demonstrated global proteomics on exosomes from mesangial cells followed by pathway analysis. We have identified 89 unique proteins and pathways in exosomes derived from gdIgA1 treated mesangial cells that could mediate pathological signaling in the glomerulus in comparison to exosomes derived from IgA1 treated mesangial cells. Conclusion Our study provides an understanding of the pathological crosstalk signaling through exosomes and key molecular targets for IgAN.

Evaluation of PAC and FASP Performance: DIA-Based Quantitative Proteomic Analysis.

The aim of this study was to compare filter-aided sample preparation (FASP) and protein aggregation capture (PAC) starting from a three-species protein mix (Human, Soybean and Pisum sativum) and two different starting amounts (1 and 10 µg). Peptide mixtures were analyzed by data-independent acquisition (DIA) and raw files were processed by three commonly used software: Spectronaut, MaxDIA and DIA-NN. Overall, the highest number of proteins (mean value of 5491) were identified by PAC (10 µg), while the lowest number (4855) was identified by FASP (1 µg). The latter experiment displayed the worst performance in terms of both specificity (0.73) and precision (0.24). Other tested conditions showed better diagnostic accuracy, with specificity values of 0.95-0.99 and precision values between 0.61 and 0.86. In order to provide guidance on the data analysis pipeline, the accuracy diagnostic of three software was investigated: (i) the highest sensitivity was obtained with Spectronaut (median of 0.67) highlighting the ability of Spectronaut to quantify low-abundance proteins, (ii) the best precision value was obtained by MaxDIA (median of 0.84), but with a reduced number of identifications compared to Spectronaut and DIA-NN data, and (iii) the specificity values were similar (between 0.93 and 0.99). The data are available on ProteomeXchange with the identifier PXD044349.

From bottom-up to cell surface proteomics: detergents or no detergents, that is the question.

Measuring the expression levels of membrane proteins (MPs) is crucial for understanding cell differentiation and tissue specificity, defining disease characteristics, identifying biomarkers, and developing therapeutics. While bottom-up proteomics addresses the need for accurately surveying the membrane proteome, the lower abundance and hydrophobic nature of MPs pose challenges in sample preparation. As MPs normally reside in the lipid bilayer, conventional extraction methods rely on detergents, introducing here a paradox - detergents prevent aggregation and facilitate protein processing, but themselves become contaminants that interfere with downstream analytical applications. Various detergent removal methods exist to mitigate this issue, including filter-aided sample preparation, SP3, suspension trapping, and membrane mimetics. This review delves into the fundamentals of each strategy, applications, merits, and limitations, providing insights into their effectiveness in MP research.

Proteomic Analysis of Salivary Secretions from the Tea Green Leafhopper, Empoasca flavescens Fabrecius.

Saliva plays a crucial role in shaping the compatibility of piercing-sucking insects with their host plants. Understanding the complex composition of leafhopper saliva is important for developing effective and eco-friendly control strategies for the tea green leafhopper, Empoasca flavescens Fabrecius, a major piercing-sucking pest in Chinese tea plantations. This study explored the saliva proteins of tea green leafhopper adults using a custom collection device, consisting of two layers of Parafilm stretched over a sucrose diet. A total of 152 proteins were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) following the filter-aided sample preparation (FASP). These proteins were categorized into six groups based on their functions, including enzymes, transport proteins, regulatory proteins, cell structure proteins, other proteins, and unknown proteins. Bioinformatics analyses predicted 16 secreted proteins, which were successfully cloned and transcriptionally analyzed across various tissues and developmental stages. Genes encoding putative salivary secretory proteins, including Efmucin1, EfOBP1, EfOBP2, EfOBP3, Efmucin2, low-density lipoprotein receptor-related protein (EfLRP), EFVg1, and EFVg2, exhibited high expressions in salivary gland (SG) tissues and feeding-associated expressions at different developmental stages. These findings shed light on the potential elicitors or effectors mediating the leafhopper feeding and defense responses in tea plants, providing insights into the coevolution of tea plants and leafhoppers. The study's conclusions open avenues for the development of innovative leafhopper control technologies that reduce the reliance on pesticides in the tea industry.

The effect of feeding on different hosts on the egg proteins in Haemaphysalis qinghaiensis tick.

The majority of ixodid ticks display host-specificity to varying extents. Feeding on different hosts affects their development and reproduction. Consequences can be analyzed at the level of the egg, as it is the initial stage of tick development. Tick egg proteins are abundant and diverse, providing nutrients for embryonic development. However, studies on tick egg profiles are scarce. In this study, we aimed to analyze whether feeding Haemaphysalis qinghaiensis ticks on the yaks (Bos grunniens) and domestic sheep (Ovis aries) has an impact on the variety and variability of the egg proteome. Detached engorged females were used to lay eggs, which were then collected, dewaxed, and subjected to protein extraction. The extracted egg proteins were enzymatically digested using Filter-Aided Sample Preparation (FASP), and the unique peptides were separated and detected by Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS). The MS data were searched against the previously constructed whole tick transcriptome library of H. qinghaiensis, and the UniProt database for the identification of tick-derived egg proteins. The analysis revealed 49 and 53 high-confidence proteins identified in eggs collected from B. grunniens (EggBg) and O. aries (EggOa), respectively. Of these, 46 high-confidence proteins were common to both egg types, while three were unique to EggBg and seven to EggOa. All the identified proteins mainly belonged to enzymes, enzyme inhibitors, transporters, and proteins with unknown functions. The differential abundance analysis showed that nine proteins were significantly more present in EggBg, while six were significantly more present in EggOa. Overall, enzymes were the most diverse group, while vitellogenin (Vg) was the most abundant. Blood meal uptake on different hosts has a certain effect on the egg proteome composition and the abundance of some proteins, but it may also lead to compensation of protein roles.

A Comparison of Bottom-Up Proteomic Sample Preparation Methods for the Human Parasite Trichomonas vaginalis.

Bottom-up proteomic approaches depend on the efficient digestion of proteins into peptides for mass spectrometric analysis. Sample preparation strategies, based on magnetic beads, filter-aided systems, or in-solution digests, are commonly used for proteomic analysis. Time-intensive methods like filter-aided sample preparation (FASP) have led to the development of new, more time-efficient filter-based strategies like suspension trappings (S-Traps) or magnetic bead-based strategies like SP3. S-Traps have been reported as an alternative proteomic sample preparation method as they allow for high sodium dodecyl sulfate (SDS) concentrations to be present in the sample. In this study, we compare the efficiency of different protocols for FASP, SP3, and S-Trap-based digestion of proteins after extraction from Trichomonas vaginalis. Overall, we found a high number of protein IDs for all tested methods and a high degree of reproducibility within each method type. However, FASP with a 3 kDa cutoff filter unit outperformed the other methods analyzed, referring to the number of protein IDs. This is the first work providing the direct comparison of four different bottom-up proteomic approaches regarding the most efficient proteomic sample preparation protocol for the human parasite T. vaginalis.

The High Resolution MASS spectrometry in Personalised Medicine: Retinol-Binding Protein 4 as a Candidate Biomarker Predictor of Progression in Bladder Urothelial Carcinoma

Introduction: Bladder cancer (BC) is the seventh most commonly diagnosed cancer in males. A large proportion of T1 cases and some Ta cases are under-staged and the significant risk of residual tumour after initial TURB of TaT1 lesions has been demonstrated. A second TURB is recommended in T1 tumours because it can increase recurrence-free survival (RFS) providing prognostic information. Non-invasive methods differentiating bladder cancer stages would be essential for diagnosis of under staged cases. Previously we demonstrated that a panel of urinary proteins measured by high resolution mass spectrometry could predict bladder cancer stages namely Ta, T1 and T2 cases. Our aim is to increase the accuracy of the biomarker panel for BC stage differentiation using a more patients, also intending to identify proteins that could be a signature to bladder cancer progression. Methods: Forty-eight urine samples were collected from volun- teers of these groups: 20 patients with bladder cancer stage Ta; 19 patients with BC stage T1 and 9 patients with BC stage T2+ (T2, T3 and T4). Urinary proteome was cleaned and digested using the Filter-Aided Sample Preparation methodology and analysed by liquid chromatography-mass spectrometry. For protein identification and label-free quantification we used MaxQuant, the data was further interrogated with the bioinformatics platform Perseus. Results: A biomarker panel was developed which consists of 87 proteins which were down-regulated between three different urothelial bladder carcinoma stages evaluated. Retinol-binding protein 4 (RBP4) consistently increases from Ta to T1, to T2+ (p <0.001) and in high grade tumours (p = 0.006). Conclusion: Our results showed a proteomic biomarker panel capable to differentiate bladder cancer stages. Besides, retinolbinding protein 4 can be a candidate signature of progression.

Optimizing MS-Based Multi-Omics: Comparative Analysis of Protein, Metabolite, and Lipid Extraction Techniques.

Multi-omics integrates diverse types of biological information from genomic, proteomic, and metabolomics experiments to achieve a comprehensive understanding of complex cellular mechanisms. However, this approach is also challenging due to technical issues such as limited sample quantities, the complexity of data pre-processing, and reproducibility concerns. Furthermore, existing studies have primarily focused on technical performance assessment and the presentation of modified protocols through quantitative comparisons of the identified protein counts. Nevertheless, the specific differences in these comparisons have been minimally investigated. Here, findings obtained from various omics approaches were profiled using various extraction methods (methanol extraction, the Folch method, and Matyash methods for metabolites and lipids) and two digestion methods (filter-aided sample preparation (FASP) and suspension traps (S-Trap)) for resuspended proteins. FASP was found to be more effective for the identification of membrane-related proteins, whereas S-Trap excelled in isolating nuclear-related and RNA-processing proteins. Thus, FASP may be suitable for investigating the immune response and bacterial infection pathways, whereas S-Trap may be more effective for studies focused on the mechanisms of neurodegenerative diseases. Moreover, regarding the choice of extraction method, the single-phase method identified organic compounds and compounds related to fatty acids, whereas the two-phase extraction method identified more hydrophilic compounds such as nucleotides. Lipids with strong hydrophobicity, such as ChE and TG, were identified in the two-phase extraction results. These findings highlight that significant differences among small molecules are primarily identified due to the varying polarities of extraction solvents. These results, obtained by considering variables such as human error and batch effects in the sample preparation step, offer comprehensive and detailed results not previously provided by existing studies, thereby aiding in the selection of the most suitable pre-processing approach.

Reduced Proliferation and Cell Death of Acute Myeloid Leukemia Cell Lines after Acalabrutinib Treatment

Background Acute myeloid leukemia (AML) still remains a significant challenge, with intensive chemotherapy treatments showing limited efficacy and lack of druggable targets in contrast to other hematologic malignancies. Exosomes, nanomolecules derived from cells reflect the parent cell's state, present opportunities for disease biomarker discovery and targeted therapy. Proteomic analysis of AML-derived exosomes may identify druggable targets despite limited prior research. In this study we investigated the potential of exosomes as a tool for target discovery in AML. Methods We conducted a proteomic analysis of AML-derived exosomes from HL-60, KG-1, and THP-1 cell lines, using fibroblast and mesenchymal stem cells as controls. Exosomes of each cell line were isolated, and digested via filter-aided sample preparation (FASP), followed by isobaric tagging using tandem mass tag (TMT) reagents. The samples were then fractionated using high-pH reversed-phase liquid chromatography and analyzed using Q-Exactive Orbitrap Hybrid Mass Spectrometry. Proteomic data were evaluated using SEQUEST in Proteome Discoverer 2.1 with a false discovery rate set to 1%. Differentially expressed proteins (DEPs) were identified and visualized in an interaction network and was analyzed for the gene ontology biological process (GOBP) using DAVID software. Protein-protein interactions were analyzed using the STRING software. Based on proteomic analysis, we identified the BTK-related pathway as potential druggable target for AML cells. AML cells were incubated with ACT, a BTK inhibitor, in various exposure time and density. Cell viability and proliferation rate was assessed using CCK-8 assay. BTK activity and signaling were assessed via Western blot analysis and immunocytochemistry of AML-derived exosomes. Cell death was evaluated using Annexin-V & PI apoptosis kit and FACS analysis. Statistical analysis was performed to ascertain significance. Results Proteomics of exosomes from three AML cell types revealed distinct protein profiles via LC-MS, with 2450 unique proteins identified (Figure 1A). For KG1, HL60, and THP1, the number of up-regulated DEPs were 438, 434, and 408, and the number of down-regulated DEPs was 126, 118, and 89 (fold change>1.5 or <0.67, P<0.05). Gene ontology analysis identified four main categories of biological processes, including cell migration, T-cell pathways, cell damage, and vesicle formation pathways. Investigation into protein-protein interactions using the STRING software allowed selection of tyrosine kinases SYK and LYN as biomarker candidates. Both kinases regulate BTK, a critical molecule in B-cell antigen receptor signaling. SYK and LYN were found to be enriched in exosomes, promoting phosphorylation of BTK in recipient cells. (Figure 1B) Cell viability experiments with AML cell lines revealed reduced viability upon treatment with ACT. Viability decreased with increased exposure time and density, with the highest effects observed at 1,000nM ACT concentration for 48 hours (Figure 2A). This was accompanied by decreased cell numbers and proliferation rate which was significant in the HL-60 and KG-1 cell lines (Figure 2B). Western blot analysis demonstrated significant decrease of the BTK downstream signaling (P-BTK, PKC and p-ERK) by acalabrutinib treatment (1,000nM) at 48 hours (Figure 2C). Proliferative markers, such as PCNA, and Cyclin D1 were also significantly decreased. LYN and SYK was also decreased in the exosomes of HL-60 and THP-1 cell line. The inhibition of P-BTK and Cyclin D1 by ACT was further confirmed through Immunofluorescence assay. Finally, ACT was shown to promote cell death in AML cell lines, as evidenced by an apoptosis assay, with the most significant increases observed in cells treated exposed to 1,000nM ACT for 72 h (Figure 2D). Conclusion Overall, the findings of this study revealed that acalabrutinib reduced proliferation and induced cell death in AML cells suggesting the potential of BTK inhibitors in AML treatment. This was explained through proteomic analysis of AML-derived exosomes. However, further studies are required to validate the clinical use of exosomes as biomarkers and druggable target.

Disclosing the molecular profile of the human amniotic mesenchymal stromal cell secretome by filter-aided sample preparation proteomic characterization

BackgroundThe secretome of mesenchymal stromal cells isolated from the amniotic membrane (hAMSCs) has been extensively studied for its in vitro immunomodulatory activity as well as for the treatment of several preclinical models of immune-related disorders. The bioactive molecules within the hAMSCs secretome are capable of modulating the immune response and thus contribute to stimulating regenerative processes. At present, only a few studies have attempted to define the composition of the secretome, and several approaches, including multi-omics, are underway in an attempt to precisely define its composition and possibly identify key factors responsible for the therapeutic effect.MethodsIn this study, we characterized the protein composition of the hAMSCs secretome by a filter-aided sample preparation (FASP) digestion and liquid chromatography-high resolution mass spectrometry (LC–MS) approach. Data were processed for gene ontology classification and functional protein interaction analysis by bioinformatics tools.ResultsProteomic analysis of the hAMSCs secretome resulted in the identification of 1521 total proteins, including 662 unique elements. A number of 157 elements, corresponding to 23.7%, were found as repeatedly characterizing the hAMSCs secretome, and those that resulted as significantly over-represented were involved in immunomodulation, hemostasis, development and remodeling of the extracellular matrix molecular pathways.ConclusionsOverall, our characterization enriches the landscape of hAMSCs with new information that could enable a better understanding of the mechanisms of action underlying the therapeutic efficacy of the hAMSCs secretome while also providing a basis for its therapeutic translation.

An ionic liquid-assisted sample preparation method for sensitive integral-membrane proteome analysis

Many ion channels and receptor proteins are potential targets for new drugs. However, standard methods for profiling these integral membrane proteins (IMPs) have not been fully established, especially when applied to rare and quantity-limited biological samples. We previously demonstrated that a mixture containing 1-butyl-3-methylimidazolium cyanate, an ionic liquid (IL), and NaOH (termed i-soln) is an excellent solubilizer for insoluble aggregates. In this study, we present a combined i-soln-assisted proteomic sample preparation platform (termed pTRUST), which is compatible with starting materials in the sub-microgram range, using our previously reported i-soln-based sample preparation strategy (iBOPs) and an in-StageTip technique. This novel and straightforward approach allows for the rapid solubilization and processing of a variety of IMPs from human samples to support highly sensitive mass spectrometry analysis. We also demonstrated that the performance of this technology surpasses that of conventional methods such as filter-aided sample preparation methods, FASP and i-FASP. The convenience and availability of pTRUST technology using the IL system have great potential for proteomic identification and characterization of novel drug targets and disease biology in research and clinical settings.

OR33-03 Circadian Analysis Of Nuclear Receptor Protein Expression In Mouse Liver Reveals Peak COUP-TFII, EAR2, LXRa, LXRb And TR4 Expression At The End Of The Mouse Active Cycle ZT0

Abstract Disclosure: M.F. Saikali: None. J. Li: None. C.L. Cummins: None. Nuclear Receptors (NRs) are a family of ligand-mediated transcription factors that control the expression of genes involved in a wide range of physiological processes. The ability to study NRs quantitatively at the protein level has been hindered by the poor quality of available antibodies, as well as the lack of available high throughput methods to study more than a few receptors at a time. To address this need, we have developed a mass spectrometry based targeted proteomic assay to quantify the absolute amounts of NR protein in mouse livers over a circadian period. C57Bl6 mice were sacrificed at 12 weeks every 4 hours from zeitgeber time ZT0 to ZT20. Their livers were processed using a transcription factor extraction protocol1. For each sample, 100 µg nuclear protein was processed using the NR assay described previously2. Briefly, the lysate is digested following the Multi-Enzyme Digestion Filter Aided Sample Preparation protocol. The sample is then spiked with 50 fmol of our internal standard mix. This mix is composed of 66 carefully selected peptides that account for 49 NRs, 11 histone peptides, and 6 circadian clock proteins. The resulting digest that contains the internal standards is desalted on C18 tips, followed by separation on an EASY-Spray C18 column (75 um x 50 cm, 3Å), and analyzed on a Thermo QExactive HF mass spectrometer in parallel reaction monitoring mode. We used this assay to quantify the changes in NR protein expression in mouse livers for 9 receptors; RORα, CAR, COUP-TFII, EAR2, GR, LXRα, LXRβ, PPARα, and TR4. RORα showed peak nuclear expression at ZT0, with a peak-to-trough change of 2.2-fold. COUP-TFII, EAR2, LXRα, LXRβ, and TR4 also showed peak expression at ZT0 (the end of the active phase) with changes of 3.3, 2.4, 1.7, 2.0, and 1.6-fold respectively. GR showed peak nuclear expression at ZT12 with a 1.8-fold change. CAR showed 2.3-fold peak expression at ZT16. COUP-TFII, EAR2, and TR4 are considered orphan receptors with no known endogenous ligands. These data will be used to uncover endogenous tissue-specific ligands by analyzing extracts isolated at the zeitgeber time that the receptor is maximally expressed. Sources of Research Support: This project has been supported by the J. P. Bickell Foundation and the Canadian Institutes of Health Research New Frontiers Research Fund and International Development Research Fund. 1.Gillespie, M. A. et al. Absolute Quantification of Transcription Factors Reveals Principles of Gene Regulation in Erythropoiesis. Mol Cell (2020) doi:10.1016/j.molcel.2020.03.031.2.Saikali, M. F. & Cummins, C. L. Quantifying the Protein Levels of All Nuclear Hormone Receptors by Mass Spectrometry. J Endocr Soc5, (2021). Presentation: Sunday, June 18, 2023

Development of a sample preparation method for micro-proteomics analysis of the formaldehyde-fixed paraffin-embedded liver tissue samples

Liver micro-proteomics based on the routinely used formaldehyde-fixed paraffin-embedded (FFPE) samples is valuable for innovative research, but the technical approach for sample preparation is often challenging. In this study, we aimed to develop a method for sample preparation for micro-proteomics on using the FFPE liver samples. We collected 2000 individual cells per batch from FFPE liver slices with laser capture microdissection and used them as test samples. We used the microscale fresh-frozen liver samples or HepG2 cells as control samples. For the FFPE samples, we first established a procedure for protein extraction. 2 h incubation at 95 °C in alkaline amine buffer supplemented with 4% sodium dodecyl sulfate allows improved production, efficiency, and quality of protein extraction. Then, we developed a dedicated protocol HDMSP for the micro-concentrated (<0.05 μg/μL) protein preparation for mass spectrometry (MS) based analysis, in which 2 μg/μL carboxyl magnetic beads and 70% acetonitrile are used to induce protein precipitation. For the 0.01 μg/μL protein control samples, protein recovery rate (PRR) by HDMSP is 72.1%, while the PRR is 5.9% if using a standard method solid phase-enhanced sample preparation. For the FFPE samples, the HDMSP PRR is 88.8%, and the subsequent MS analysis demonstrates increased depth, robustness, and quantitation accuracy for HDMSP relative to the control of in-gel digestion. Moreover, the physicochemical properties and subcellular location of the FFPE liver micro-proteome are comparable to those of the fresh-frozen control samples processed with filter-aided sample preparation (FASP). HDMSP is also comparable to FASP in terms of reproducibility and physicochemical properties in liver subcellular proteomes, and meanwhile reduces the sample preparation time by 15.9% and the experimental cost by 30.8%. Overall, the new method is simple and highly effective for preparing the microscale FFPE liver protein samples for MS analysis. This study provides a useful solution for FFPE liver micro-proteomics.

A Rapid and Efficient Method for the Extraction of Histone Proteins.

Current protocols used to extract and purify histones are notoriously tedious, especially when using yeast cells. Here, we describe the use of a simple filter-aided sample preparation approach enabling histone extraction from yeast and mammalian cells using acidified ethanol, which not only improves extraction but also inactivates histone-modifying enzymes. We show that our improved method prevents N-terminal clipping of H3, an artifact frequently observed in yeast cells using standard histone extraction protocols. Our method is scalable and provides efficient recovery of histones when extracts are prepared from as few as two million yeast cells. We further demonstrate the application of this approach for the analysis of histone modifications in fungal clinical isolates available in a limited quantity. Compared with standard protocols, our method enables the study of histones and their modifications in a faster, simpler, and more robust manner.

Integrated Mass Spectrometry‐based Pipeline for Characterization of Tau in Human Alzheimer’s Brain: Development and Comparison of Sample Preparation Methods

AbstractBackgroundTau protein aggregation into neurofibrillary tangles in the brain is a pathological hallmark of Alzheimer’s disease (AD) and related tauopathies [1]. Though the mechanism of tau destabilization is not fully understood, tau protein exhibits several allele‐specific isoforms and post‐translational modifications (PTMs) specific to tau aggregates [2]. To explore in‐depth tau species in brain tissues of AD patients, we developed novel pipelines based on different tau fractions retrieved by buffer solubility, Filter Aided Sample Preparation (FASP) or immunoprecipitation, before high‐resolution mass spectrometry (HRMS) analysis.MethodAs a proof of concept, we used frozen brain samples from two AD patients (0.6‐1.2 g per replicate, middle frontal gyrus). The samples were divided and homogenized, ultracentrifuged at 180.000xg for 30min and solubilized in different buffers successively (2 replicates): (1) SarkMethodlow‐salt buffer, 10% Triton X‐100, sarkosyl buffer, and urea buffer; (2) RIPAMethodhigh‐salt buffer (twice), RIPA buffer and urea buffer; and, (3) GnHMethodguanidine hydrochloride and urea buffer. Then, we performed an antibody‐free approach by FASP or immunoprecipitation with a panel of commercial tau antibodies and analyzed on reversed‐phase capillary liquid chromatography, coupled with a qExactive HRMS.ResultHRMS demonstrated that the RIPA method performed better than the other methods for Tau analysis: coverage of 63% (full‐length, 2N4R) and 342 tau peptide‐spectrum matches (PSMs) (Sark: 49% and 183 PSMs; GnH: 41% and 169 PSMs). PTM‐modified tau species (phosphorylated, methylated, and acetylated) were primarily seen using the RIPA method (59 PSMs; Sark: 19 PSMs, GnH: 21 PSMs). Immunoprecipitation improved tau coverage and PTM detection compared to FASP.ConclusionThese findings highlight the best performance of the RIPA method followed by immunoprecipitation for the study of AD brain tau allele‐specific isoforms and PTMs using HRMS. Better characterization of Tau molecular profile in the brain of AD patients opens the gate for a better understanding of AD pathogenesis and represents an opportunity in the biomarker field.[1] Mroczko, B. et al. Int J Mol Sci 2019, 20, E4661, https://doi.org/10.3390/ijms20194661.[2] Boyarko, B.; Hook, V. Front. Neurosci. 2021, 15, 702788, https://doi.org/10.3389/fnins.2021.702788.

Egg protein profile and dynamics during embryogenesis in Haemaphysalis flava ticks

Tick eggs contain all essential proteins for embryogenesis, and egg proteins are a potential reservoir of tick-protective antigens. However, the protein profile and dynamics during embryonic development remain unknown. This study aimed to depict the protein profile and dynamics in tick embryogenesis, further providing protein candidates for targeted interventions. Eggs from Haemaphysalis flava ticks were incubated at 28 °C and 85% relative humidity. On days 0 (newly laid eggs without incubation), 7, 14 and 21, eggs were collected, dewaxed and subject to protein extraction. Extracted proteins were digested by filter-aided sample preparation and analyzed by liquid chromatography-tandem mass spectrometry (LC/MS-MS). MS data were searched against an in-house H. flava protein database for tick-derived protein identification. Abundances of 40 selected high-confidence proteins were further quantified by LC-parallel reaction monitoring (PRM)/MS analysis throughout egg incubation. A total of 93 high-confidence proteins were identified in eggs on 0-day incubation. Identified proteins belonged to seven functional categories: transporters, enzymes, proteinase inhibitors, immunity-related proteins, cytoskeletal proteins, heat shock proteins and uncharacterized proteins. The enzyme category contained the most types of proteins. Neutrophil elastase inhibitors represented the most abundant proteins in terms of intensity-based absolute-protein-quantification. LC-PRM/MS revealed that the abundances of 20 proteins increased including enolase, calreticulin, actin, GAPDH et cetera, and the abundances of 11 proteins decreased including vitellogenins, neutrophil elastase inhibitor, carboxypeptidase Q, et cetera from 0- to 21-day incubation. This study provides the most comprehensive egg protein profile and dynamics during tick embryogenesis. Further investigations are needed to test the tick-control efficacy by targeting the egg proteins.

Bottom-Up Proteomics: Advancements in Sample Preparation

Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomics is a powerful technique for profiling proteomes of cells, tissues, and body fluids. Typical bottom-up proteomic workflows consist of the following three major steps: sample preparation, LC-MS/MS analysis, and data analysis. LC-MS/MS and data analysis techniques have been intensively developed, whereas sample preparation, a laborious process, remains a difficult task and the main challenge in different applications. Sample preparation is a crucial stage that affects the overall efficiency of a proteomic study; however, it is prone to errors and has low reproducibility and throughput. In-solution digestion and filter-aided sample preparation are the typical and widely used methods. In the past decade, novel methods to improve and facilitate the entire sample preparation process or integrate sample preparation and fractionation have been reported to reduce time, increase throughput, and improve reproducibility. In this review, we have outlined the current methods used for sample preparation in proteomics, including on-membrane digestion, bead-based digestion, immobilized enzymatic digestion, and suspension trapping. Additionally, we have summarized and discussed current devices and methods for integrating different steps of sample preparation and peptide fractionation.

Dysregulation of metalloproteins in ischemic heart disease patients with systolic dysfunction

Ischemic heart disease (IHD) is the leading cause of mortality worldwide. Metalloproteins have been linked to human health and diseases. The molecular functions of metalloproteins in IHD is not well understood and require further exploration. The objective of this study was to find out the role of metalloproteins in the pericardial fluid of IHD patients having normal (EF > 45) and impaired (EF < 45) left ventricular ejection fraction (LVEF). IHD patients were grouped into two categories: LVEF<45 (n = 12) and LVEF >45 (n = 33). Pooled samples of pericardial fluid were fractionated by using ZOOM-isoelectric focusing (IEF) followed by further processing using one-dimensional gel electrophoresis (1D SDS-PAGE) and filter-aided sample preparation (FASP). Tryptic peptides of each fraction and differential bands were then analyzed by nano-LC-ESI-MS/MS. Protein identification was performed through a Mascot search engine using NCBI-Prot and SwissProt databases. A total of 1082 proteins including 154 metalloproteins were identified. In the differential bands, 60 metalloproteins were identified, while 115 metalloproteins were identified in all ZOOM-IEF fractions. Twelve differentially expressed metalloproteins were selected in the intense bands according to their molecular weight (MW) and isoelectric point (pI). The 12 differentially expressed metalloprotein includes ceruloplasmin, Prothrombin, Vitamin K-dependent protein, Fibulin-1, Ribosomal protein S6 kinase alpha-6, nidogen, partial, Serum albumin, Hemopexin, C-reactive protein, Serum amyloid P-component, and Intelectin-1 protein which were all up-regulated while serotransferrin is the only metalloprotein that was down-regulated in impaired (LVEF<45) group. Among the metalloproteins, Zn-binding proteins are 36.5 % followed by Ca-binging 32.2 %, and Fe-binging 12.2 %. KEGG, pathway analysis revealed the association of ceruloplasmin and serotransferrin with the ferroptosis pathway. In conclusion, 154 metalloproteins were identified of them the Zn-binding protein followed by Ca-binding and Fe-binding proteins were the most abundant metalloproteins. The two metalloproteins, the Cu-binding protein ceruloplasmin, and Fe-binding protein serotransferrin are involved in the ferroptosis pathway, an iron-dependent form of regulated cell death that has been linked to cardiac pathology, especially in IHD patients having impaired systolic (LVEF<45) dysfunction. However, further research is required to validate these findings.

An analysis for proteomic profile of NeuroD2 related changes in N2A neuroblastoma cell line

Aim: NeuroD2 transcription factor is a key regulator of neurogenin-NeuroD signaling network and induces neuronal development, differentiation, neurogenesis and calcium dependent signaling. NeuroD2 regulates expression of survival and plasticity related proteins in neurons. Surprisingly, inhibition of NeuroD2 causes an increase in apoptotic cell death. Even though previous studies found out important data about NeuroD2 function, molecular interactions of NeuroD2 behind all of these impacts remains elusive. For this reason, it was aimed to shed light on the proteome profile of NeuroD2 based changes in the N2A cell line. Materials and methods: NeuroD2 over-expression and NeuroD2 inhibition groups were created via lentiviral vectors. Mouse N2A cell line was transfected with the given vectors and incubated for 6 hours. After incubation samples were prepared for proteomic analyses with Filter Aided Sample Preparation (FASP) protocol an LC-MS/MS analysis was carried out. Results: Under conditions of overexpression and inhibition, detected proteins were filtered according to significant cut off values. The filtered proteins were further investigated to exhibit a coherent expression in each situation. Eventually, increased NeuroD2 activity was accompanied by an increase in N-alpha-acetyltransferase 25 (NAA25), and Synaptobrevin homolog (YKT6). On the other hand, when NeuroD2 was suppressed, expression of Cytoplasmic Dynein 1 Light Intermediate Chain 1, Kinesin-Like Protein (KIF-11), Leucine-tRNA Ligase (LARS1), and Ubiquitin-Associated Protein 2 (UBA2) were found to be upregulated with a back action. Conclusion: Up-regulations of the proteins Cytoplasmic Dynein 1, KIF11, LARS1, and UBA2 suggested that these proteins might be controlled by inhibiting NeuroD2. Axonal transport, neuronal signaling, and activity of PI3K/AKT pathway can be indirectly induced by NeuroD2.

Does filter-aided sample preparation provide sufficient method linearity for quantitative plant shotgun proteomics?

Due to its outstanding throughput and analytical resolution, gel-free LC-based shotgun proteomics represents the gold standard of proteome analysis. Thereby, the efficiency of sample preparation dramatically affects the correctness and reliability of protein quantification. Thus, the steps of protein isolation, solubilization, and proteolysis represent the principal bottleneck of shotgun proteomics. The desired performance of the sample preparation protocols can be achieved by the application of detergents. However, these compounds ultimately compromise reverse-phase chromatographic separation and disrupt electrospray ionization. Filter-aided sample preparation (FASP) represents an elegant approach to overcome these limitations. Although this method is comprehensively validated for cell proteomics, its applicability to plants and compatibility with plant-specific protein isolation protocols remain to be confirmed. Thereby, the most important gap is the absence of the data on the linearity of underlying protein quantification methods for plant matrices. To fill this gap, we address here the potential of FASP in combination with two protein isolation protocols for quantitative analysis of pea (Pisum sativum) seed and Arabidopsis thaliana leaf proteomes by the shotgun approach. For this aim, in comprehensive spiking experiments with bovine serum albumin (BSA), we evaluated the linear dynamic range (LDR) of protein quantification in the presence of plant matrices. Furthermore, we addressed the interference of two different plant matrices in quantitative experiments, accomplished with two alternative sample preparation workflows in comparison to conventional FASP-based digestion of cell lysates, considered here as a reference. The spiking experiments revealed high sensitivities (LODs of up to 4 fmol) for spiked BSA and LDRs of at least 0.6 × 102. Thereby, phenol extraction yielded slightly better recoveries, whereas the detergent-based method showed better linearity. Thus, our results indicate the very good applicability of FASP to quantitative plant proteomics with only limited impact of the protein isolation technique on the method's overall performance.