Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) for Quantitative Proteomics

Mechanistic insights into the antitumoral potential and in vivo antiproliferative efficacy of a silver-based core@shell nanosystem

This study delves into the biomolecular mechanisms underlying the antitumoral efficacy of a hybrid nanosystem, comprised of a silver core@shell (Ag@MSNs) functionalized with transferrin (Tf). Employing a SILAC proteomics strategy, we identified over 150 de-regulated proteins following exposure to the nanosystem. These proteins play pivotal roles in diverse cellular processes, including mitochondrial fission, calcium homeostasis, endoplasmic reticulum (ER) stress, oxidative stress response, migration, invasion, protein synthesis, RNA maturation, chemoresistance, and cellular proliferation. Rigorous validation of key findings substantiates that the nanosystem elicits its antitumoral effects by activating mitochondrial fission, leading to disruptions in calcium homeostasis, as corroborated by RT-qPCR and flow cytometry analyses. Additionally, induction of ER stress was validated through western blotting of ER stress markers. The cytotoxic action of the nanosystem was further affirmed through the generation of cytosolic and mitochondrial reactive oxygen species (ROS). Finally, in vivo experiments using a chicken embryo model not only confirmed the antitumoral capacity of the nanosystem, but also demonstrated its efficacy in reducing cellular proliferation. These comprehensive findings endorse the potential of the designed Ag@MSNs-Tf nanosystem as a groundbreaking chemotherapeutic agent, shedding light on its multifaceted mechanisms and in vivo applicability.

Recent Advances and Techniques for Identifying Novel Antibacterial Targets

BACKGROUND

With the emergence of drug-resistant bacteria, the development of new antibiotics is urgently required. Target-based drug discovery is the most frequently employed approach for the drug development process. However, traditional drug target identification techniques are costly and time-consuming. As research continues, innovative approaches for antibacterial target identification have been developed which enabled us to discover drug targets more easily and quickly.

METHODS

In this review, methods for finding drug targets from omics databases have been discussed in detail including principles, procedures, advantages, and potential limitations. The role of phage-driven and bacterial cytological profiling approaches is also discussed. Moreover, current article demonstrates the advancements being made in the establishment of computational tools, machine learning algorithms, and databases for antibacterial target identification.

RESULTS

Bacterial drug targets successfully identified by employing these aforementioned techniques are described as well.

CONCLUSION

The goal of this review is to attract the interest of synthetic chemists, biologists, and computational researchers to discuss and improve these methods for easier and quicker development of new drugs.

Glycan/Protein-Stable Isotope Labeling in Cell Culture for Enabling Concurrent Quantitative Glycomics/Proteomics/Glycoproteomics

The complexity and heterogeneity of protein glycosylation present an analytical challenge to the studies of characterization and quantitation. Various LC-MS-based quantitation strategies have emerged in recent decades. Metabolic stable isotope labeling has been developed to enhance the accurate LC/MS-based quantitation between different cell lines. Stable isotope labeling by amino acids in a cell culture (SILAC) is the most widely used metabolic labeling method in proteomic analysis. However, it can only label the peptide backbone and is thus limited in glycomic studies. Here, we present a metabolic isotope labeling strategy, named GlyProSILC (Glycan Protein Stable Isotope Labeling in Cell Culture), that can label both the glycan motif and peptide backbone from the same batch of cells. It was performed by feeding cells with a heavy medium containing amide-15N-glutamine, 13C6-arginine (Arg6), and 13C6-15N2-lysine (Lys8). No significant change of cell line metabolism after GlyProSILC labeling was observed based on transcriptomic, glycomic, and proteomic data. The labeling conditions, labeling efficiency, and quantitation accuracy were investigated. After quantitation correction, we simultaneously quantified 62 N-glycans, 574 proteins, and 344 glycopeptides using the same batch of mixed 231BR/231 cell lines. So far, GlyProSILC provides an accurate and effective quantitation approach for glycomics, proteomics, and glycoproteomics in a cell culture system.

Biochemical and proteomic insights into sarcoplasmic reticulum Ca2+-ATPase complexes in skeletal muscles

INTRODUCTION

Skeletal muscles contain large numbers of high-molecular-mass protein complexes in elaborate membrane systems. Integral membrane proteins are involved in diverse cellular functions including the regulation of ion handling, membrane homeostasis, energy metabolism and force transmission.

AREAS COVERED

The proteomic profiling of membrane proteins and large protein assemblies in skeletal muscles are outlined in this article. This includes a critical overview of the main biochemical separation techniques and the mass spectrometric approaches taken to study membrane proteins. As an illustrative example of an analytically challenging large protein complex, the proteomic detection and characterization of the Ca2+-ATPase of the sarcoplasmic reticulum is discussed. The biological role of this large protein complex during normal muscle functioning, in the context of fiber type diversity and in relation to mechanisms of physiological adaptations and pathophysiological abnormalities is evaluated from a proteomics perspective.

EXPERT OPINION

Mass spectrometry-based muscle proteomics has decisively advanced the field of basic and applied myology. Although it is technically challenging to study membrane proteins, innovations in protein separation methodology in combination with sensitive mass spectrometry and improved systems bioinformatics has allowed the detailed proteomic detection and characterization of skeletal muscle membrane protein complexes, such as Ca2+-pump proteins of the sarcoplasmic reticulum.

Identification of PP2A-B55 targets uncovers regulation of emerin during nuclear envelope reassembly in Drosophila

Mitotic exit requires the dephosphorylation of many proteins whose phosphorylation was needed for mitosis. Protein phosphatase 2A with its B55 regulatory subunit (PP2A-B55) promotes this transition. However, the events and substrates that it regulates are incompletely understood. We used proteomic approaches in Drosophila to identify proteins that interact with and are dephosphorylated by PP2A-B55. Among several candidates, we identified emerin (otefin in Drosophila). Emerin resides in the inner nuclear membrane and interacts with the DNA-binding protein barrier-to-autointegration factor (BAF) via a LEM domain. We found that the phosphorylation of emerin at Ser50 and Ser54 near its LEM domain negatively regulates its association with BAF, lamin and additional emerin in mitosis. We show that dephosphorylation of emerin at these sites by PP2A-B55 determines the timing of nuclear envelope reformation. Genetic experiments indicate that this regulation is required during embryonic development. Phosphoregulation of the emerin-BAF complex formation by PP2A-B55 appears as a key event of mitotic exit that is likely conserved across species.

Fiber-Type Shifting in Sarcopenia of Old Age: Proteomic Profiling of the Contractile Apparatus of Skeletal Muscles

The progressive loss of skeletal muscle mass and concomitant reduction in contractile strength plays a central role in frailty syndrome. Age-related neuronal impairments are closely associated with sarcopenia in the elderly, which is characterized by severe muscular atrophy that can considerably lessen the overall quality of life at old age. Mass-spectrometry-based proteomic surveys of senescent human skeletal muscles, as well as animal models of sarcopenia, have decisively improved our understanding of the molecular and cellular consequences of muscular atrophy and associated fiber-type shifting during aging. This review outlines the mass spectrometric identification of proteome-wide changes in atrophying skeletal muscles, with a focus on contractile proteins as potential markers of changes in fiber-type distribution patterns. The observed trend of fast-to-slow transitions in individual human skeletal muscles during the aging process is most likely linked to a preferential susceptibility of fast-twitching muscle fibers to muscular atrophy. Studies with senescent animal models, including mostly aged rodent skeletal muscles, have confirmed fiber-type shifting. The proteomic analysis of fast versus slow isoforms of key contractile proteins, such as myosin heavy chains, myosin light chains, actins, troponins and tropomyosins, suggests them as suitable bioanalytical tools of fiber-type transitions during aging.

Proteomic profiling of the carbon-starved Escherichia coli reveals upregulation of stress-inducible pathways implicated in biological adhesion and methylglyoxal metabolism

Starvation in bacteria is a complex adaptive response to deprivation of nutrients that has been shown to implicate a number of stress networks that modulate pathogenicity and antibiotic resistance. Starvation in nature is qualitatively different from in-culture late stationary phase energy source depletion. To look into proteome-level alterations elicited by complete elimination of carbon source, we used Escherichia coli HT115-derived SLE1 strain cells and a combination of label-free and metabolic isotope labeling approaches. We isolated pathways differentially affected by carbon starvation and observed robust upregulation of proteins implicated in networks belonging to Gene Ontology terms 'Biological adhesion' and 'Methylglyoxal metabolism'.

Characterizing Endogenous Protein Complexes with Biological Mass Spectrometry

Biological mass spectrometry (MS) encompasses a range of methods for characterizing proteins and other biomolecules. MS is uniquely powerful for the structural analysis of endogenous protein complexes, which are often heterogeneous, poorly abundant, and refractive to characterization by other methods. Here, we focus on how biological MS can contribute to the study of endogenous protein complexes, which we define as complexes expressed in the physiological host and purified intact, as opposed to reconstituted complexes assembled from heterologously expressed components. Biological MS can yield information on complex stoichiometry, heterogeneity, topology, stability, activity, modes of regulation, and even structural dynamics. We begin with a review of methods for isolating endogenous complexes. We then describe the various biological MS approaches, focusing on the type of information that each method yields. We end with future directions and challenges for these MS-based methods.

Proteomic profiling of carbonic anhydrase CA3 in skeletal muscle

INTRODUCTION

Carbonic anhydrase (CA) is a key enzyme that mediates the reversible hydration of carbon dioxide. Skeletal muscles contain high levels of the cytosolic isoform CA3. This enzyme has antioxidative function and plays a crucial role in the maintenance of intracellular pH homeostasis.

AREAS COVERED

Since elevated levels of serum CA3, often in combination with other muscle-specific proteins, are routinely used as a marker of general muscle damage, it was of interest to examine recent analyses of this enzyme carried out by modern proteomics. This review summarizes the mass spectrometry-based identification and evaluation of CA3 in normal, adapting, dystrophic, and aging skeletal muscle tissues.

EXPERT OPINION

The mass spectrometric characterization of CA3 confirmed this enzyme as a highly useful marker of both physiological and pathophysiological alterations in skeletal muscles. Cytosolic CA3 is clearly enriched in slow-twitching type I fibers, which makes it an ideal marker for studying fiber type shifting and muscle adaptations. Importantly, neuromuscular diseases feature distinct alterations in CA3 in skeletal muscle tissues versus biofluids, such as serum. Characteristic changes of CA3 in age-related muscle wasting and dystrophinopathy established this enzyme as a suitable biomarker candidate for differential diagnosis and monitoring of disease progression and therapeutic impact.

Cloning, expression, solubilization, and purification of a functionally active recombinant cAMP-dependent protein kinase catalytic subunit-like protein PKAC1 from Trypanosoma equiperdum

The gene encoding the cAMP-dependent protein kinase (PKA) catalytic subunit-like protein PKAC1 from the Venezuelan TeAp-N/D1 strain of Trypanosoma equiperdum was cloned, and the recombinant TeqPKAC1 protein was overexpressed in bacteria. A major polypeptide with an apparent molecular mass of ∼38 kDa was detected by SDS-polyacrylamide gel electrophoresis, and immunoblotting using antibodies against the human PKA catalytic subunit α. Unfortunately, most of the expressed TeqPKAC1 was highly insoluble. Polypeptides of 36-38 kDa and 45-50 kDa were predominantly seen by immunoblotting in the bacterial particulate and cytosolic fractions, respectively. Since the incorporation of either 4% Triton X-100 or 3% sarkosyl or a mixture of 10 mM MgCl₂ and 1 mM ATP (MgATP) improved the solubilization of TeqPKAC1, we used a combination of Triton X-100, sarkosyl and MgATP to solubilize the recombinant protein. TeqPKAC1 was purified by first reconstituting a hybrid holoenzyme between the recombinant protein and a mammalian poly-His-tagged PKA regulatory subunit that was immobilized on a Ni²⁺-chelating affinity resin, and then by eluting TeqPKAC1 using cAMP. TeqPKAC1 was functional given that it was capable of phosphorylating PKA catalytic subunit substrates, such as kemptide (LRRASLG), histone type II-AS, and the peptide SP20 (TTYADFIASGRTGRRNSIHD), and was inhibited by the peptide IP20 (TTYADFIASGRTGRRNAIHD), which contains the inhibitory motif of the PKA-specific heat-stable inhibitor PKI-α. Optimal enzymatic activity was obtained at 37 °C and pH 8.0-9.0; and the order of effectiveness of nucleotide triphosphates and divalent cations was ATP » GTP ≅ ITP and Mg²⁺ ≅ Mn²⁺ ≅ Fe²⁺ » Ca²⁺ ≅ Zn², respectively.

Stable Isotope Labeling by Carbon-13 in Bacteria Culture for the Analysis of Residual Avermectin Using Stable Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry

This study describes the development of a new stable isotope labeling method by carbon-13 in bacteria culture (SILCB) for the analysis of residual antibiotics via liquid chromatography with tandem mass spectrometry (LC-MS/MS). Stable isotope dilution (SID) LC-MS/MS with QuEChERS was employed to determine avermectin, particularly avermectin B1a (AV-a) and B1b (AV-b), based on completely ¹³C-labeled internal standards (¹³C-ISs) obtained from the SILCB. Our SILCB was developed from an optimal inorganic medium using ¹³C₆-glucose for Streptomyces avermitilis (14893 strain). A rough extract containing ¹³C-ISs was purified via high-speed countercurrent chromatography with a volatile two-phase solvent system composed of n-hexane/ethyl acetate/methanol/0.5% formic acid in water (7/3/5/5/, V/V). The purified ¹³C-ISs were evaluated to confirm the presence of completely ¹³C-labeled ions with m/z 938 > 326 and m/z 923 > 309 for AV-a and AV-b, respectively. The QuEChERS approach with the ¹³C-ISs procedure achieved acceptable recovery rates in beef meat samples of 99.5 - 100.0% (RSD < 2.0%, n = 6). For the analysis of residual antibiotics in foodstuffs by SID-LC-MS/MS and QuEChERS, the SILCB represents a significant improvement over previous methods suffering from cumbersome sample preparation and matrix effects.

Advances in mass spectrometry-based glycoproteomics: An update covering the period 2017-2021

Protein glycosylation is one of the most common posttranslational modifications, and plays an essential role in a wide range of biological processes such as immune response, intercellular signaling, inflammation, host-pathogen interaction, and protein stability. Glycoproteomics is a proteomics subfield dedicated to identifying and characterizing the glycans and glycoproteins in a given cell or tissue. Aberrant glycosylation has been associated with various diseases such as Alzheimer's disease, viral infections, inflammation, immune deficiencies, congenital disorders, and cancers. However, glycoproteomic analysis remains challenging because of the low abundance, site-specific heterogeneity, and poor ionization efficiency of glycopeptides during LC-MS analyses. Therefore, the development of sensitive and accurate approaches to efficiently characterize protein glycosylation is crucial. Methods such as metabolic labeling, enrichment, and derivatization of glycopeptides, coupled with different mass spectrometry techniques and bioinformatics tools, have been developed to achieve sophisticated levels of quantitative and qualitative analyses of glycoproteins. This review attempts to update the recent developments in the field of glycoproteomics reported between 2017 and 2021.

MALDI-TOF mass spectrometry for antimicrobial susceptibility testing

The advent of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in clinical microbiology has dramatically improved the accuracy and speed of diagnostics. However, this progress has mainly been limited to the identification of microorganisms, whereas the practical improvement of antimicrobial susceptibility testing (AST) still lags behind. MALDI-TOF MS-based approaches include the detection of selected resistance mechanisms and the universal phenotypic AST. This minireview focuses on the discussion of those MALDI-TOF MS methods that allow universal growth-based phenotypic AST. The method of minimal profile change concentrations (MPCC) is based on detecting proteome modification in presence of an antimicrobial. Using stable-isotope labeling, characteristic mass shifts in the presence of an antimicrobial indicate the incorporation of the isotopic labels, and, thus, the viability and resistance of the microorganism. For MALDI Biotyper antibiotic susceptibility test rapid assay (MBT-ASTRA), microorganisms are incubated with or without an antimicrobial, followed by cell lysis, protein extraction, and transfer of the cell lysate onto a MALDI target plate. Using the internal standard, peak intensities are correlated to the amount of microbial proteins, and the relative microbial growth is calculated. Most recent development in the field is the direct-on-target microdroplet growth assay (DOT-MGA). Here, incubation of microorganisms with antimicrobials takes place directly on spots of a MALDI target in form of microdroplets. After incubation, nutrient medium is removed by dabbing with absorptive material. Resistant microorganisms grow despite the presence of antimicrobial, and their amplified biomass is detected by MALDI-TOF MS. Finally, an outlook is provided for further assay improvements.

Evaluating Spatiotemporal Dynamics of Phosphorylation of RNA Polymerase II Carboxy-Terminal Domain by Ultraviolet Photodissociation Mass Spectrometry

The critical role of site-specific phosphorylation in eukaryotic transcription has motivated efforts to decipher the complex phosphorylation patterns exhibited by the carboxyl-terminal domain (CTD) of RNA polymerase II. Phosphorylation remains a challenging post-translational modification to characterize by mass spectrometry owing to the labile phosphate ester linkage and low stoichiometric prevalence, two features that complicate analysis by high-throughput MS/MS methods. Identifying phosphorylation sites represents one significant hurdle in decrypting the CTD phosphorylation, a problem exaggerated by a large number of potential phosphorylation sites. An even greater obstacle is decoding the dynamic phosphorylation pattern along the length of the periodic CTD sequence. Ultraviolet photodissociation (UVPD) is a high-energy ion activation method that provides ample backbone cleavages of peptides while preserving labile post-translational modifications that facilitate their confident localization. Herein, we report a quantitative parallel reaction monitoring (PRM) method developed to monitor spatiotemporal changes in site-specific Ser5 phosphorylation of the CTD by cyclin-dependent kinase 7 (CDK7) using UVPD for sequence identification, phosphosite localization, and differentiation of phosphopeptide isomers. We capitalize on the series of phospho-retaining fragment ions produced by UVPD to create unique transition lists that are pivotal for distinguishing the array of phosphopeptides generated from the CTD.

Quantitative Mass Spectrometry-Based Proteomics for Biomarker Development in Ovarian Cancer

Ovarian cancer is the most lethal gynecologic malignancy among women. Approximately 70–80% of patients with advanced ovarian cancer experience relapse within five years and develop platinum-resistance. The short life expectancy of patients with platinum-resistant or platinum-refractory disease underscores the need to develop new and more effective treatment strategies. Early detection is a critical step in mitigating the risk of disease progression from early to an advanced stage disease, and protein biomarkers have an integral role in this process. The best biological diagnostic tool for ovarian cancer will likely be a combination of biomarkers. Targeted proteomics methods, including mass spectrometry-based approaches, have emerged as robust methods that can address the chasm between initial biomarker discovery and the successful verification and validation of these biomarkers enabling their clinical translation due to the robust sensitivity, specificity, and reproducibility of these versatile methods. In this review, we provide background information on the fundamental principles of biomarkers and the need for improved treatment strategies in ovarian cancer. We also provide insight into the ways in which mass spectrometry-based targeted proteomics approaches can provide greatly needed solutions to many of the challenges related to ovarian cancer biomarker development.

SILAC quantitative proteomics analysis of ivermectin-related proteomic profiling and molecular network alterations in human ovarian cancer cells

The antiparasitic agent ivermectin offers more promises to treat a diverse range of diseases. However, a comprehensive proteomic analysis of ivermectin-treated ovarian cancer (OC) cells has not been performed. This study sought to identify ivermectin-related proteomic profiling and molecular network alterations in human OC cells. Stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative proteomics was used to study the human OC TOV-21G cells. After TOV-21G cells underwent 10 passages in SILAC-labeled growth media, TOV-21G cells were treated with 10 ml of 20 μmol/L ivermectin in cell growing medium for 24 h. The SILAC-labeled proteins were digested with trypsin; tryptic peptides were identified with mass spectrometry (MS). Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was used to mine signaling pathway alterations with ivermectin-related proteins in TOV-21G cells. Gene ontology (GO) analysis was used to explore biological functions of ivermectin-related proteins, including biological processes (BPs), cellular components (CCs), and molecular functions (MFs). The protein-protein interaction network was analyzed with molecular complex detection (MCODE) to identify hub modules. In total, 4,447 proteins were identified in ivermectin-treated TOV-21G cells. KEGG analysis revealed 89 statistically significant signaling pathways. Interestingly, the clustering analysis of these pathways showed that ivermectin was involved in various cancer pathogenesis processes, including modulation of replication, RNA metabolism, and translational machinery. GO analysis revealed 69 statistically significant CCs, 87 MFs, and 62 BPs. Furthermore, MCODE analysis identified five hub modules, including 147 hub molecules. Those hub modules involved ribosomal proteins, RNA-binding proteins, cell-cycle progression-related proteins, proteasome subunits, and minichromosome maintenance proteins. These findings demonstrate that SILAC quantitative proteomics is an effective method to analyze ivermectin-treated cells, provide the first ivermectin-related proteomic profiling and molecular network alterations in human OC cells, and provide deeper insights into molecular mechanisms and functions of ivermectin to inhibit OC cells.

Mosquito defensin facilitates Japanese encephalitis virus infection by downregulating the C6/36 cell-surface antiviral protein HSC70B

Japanese encephalitis virus (JEV) is a viral zoonosis that can cause viral encephalitis, death and disability whose primary vector is the Culex mosquito. Viral infection induces a series of antimicrobial peptide responses in mosquitoes, and the effector defensin enhances JEV replication in mosquitoes. However, the underlying mechanisms by which defensin enhances JEV are not fully understood. Here, we found that mosquito defensin could downregulate the antiviral protein HSC70B and enhance virus infection in mosquitoes. The cell-surface protein HSC70B was significantly downregulated by JEV infection and defensin treatment. Low levels of HSC70B were beneficial to JEV infection in mosquitoes. Taken together, these findings show that defensin and HSC70B axis facilitates JEV infection in the mosquito.

Phosphoproteome Analysis in Immune Cell Signaling

Immune cell signaling is largely regulated by protein phosphorylation. Stimulation of toll-like receptors (TLRs) by pathogen-associated ligands drives the cascade of immune response, which can be influenced by differences in phosphoprotein abundance. Therefore, the analysis of phosphorylation signatures at a global level is central to understanding the complex and integrated signaling in macrophages upon pathogen attack. Here, we describe a mass spectrometry-based approach to identify and quantify phosphoproteome changes in response to the stimulation of TLR2, TLR4, and TLR7 with immune-response inducing ligands in cultured immune cells. This review will focus on the TLR stimulation of mouse macrophages as an example; however, the technique is applicable to any immortalized immune cell and any soluble stimuli. The methodology includes protocols for metabolic labeling of immune cells (stable isotope labeling of amino acids in cell culture, i.e., SILAC); ligand-initiated stimulation of immune receptors followed by cell lysis; in-solution trypsin digestion of proteins and enrichment of the resulting peptide mix for collecting phosphopeptides, which are then analyzed by high-resolution LC-MS/MS (liquid-chromatography tandem mass spectrometry). © 2020 Wiley Periodicals LLC. Basic Protocol 1: SILAC labeling of mouse macrophages Basic Protocol 2: Stimulation, cell lysis and Western Blotting Basic Protocol 3: Trypsin digestion, fractionation and phosphopeptide enrichment Basic Protocol 4: Quantitative mass spectrometry Alternate Protocol: Culturing SILAC-labeled cells from frozen mouse macrophages cells.

Activity Dependent and Independent Determinants of Synaptic Size Diversity

The extraordinary diversity of excitatory synapse sizes is commonly attributed to activity-dependent processes that drive synaptic growth and diminution. Recent studies also point to activity-independent size fluctuations, possibly driven by innate synaptic molecule dynamics, as important generators of size diversity. To examine the contributions of activity-dependent and independent processes to excitatory synapse size diversity, we studied glutamatergic synapse size dynamics and diversification in cultured rat cortical neurons (both sexes), silenced from plating. We found that in networks with no history of activity whatsoever, synaptic size diversity was no less extensive than that observed in spontaneously active networks. Synapses in silenced networks were larger, size distributions were broader, yet these were rightward-skewed and similar in shape when scaled by mean synaptic size. Silencing reduced the magnitude of size fluctuations and weakened constraints on size distributions, yet these were sufficient to explain synaptic size diversity in silenced networks. Model-based exploration followed by experimental testing indicated that silencing-associated changes in innate molecular dynamics and fluctuation characteristics might negatively impact synaptic persistence, resulting in reduced synaptic numbers. This, in turn, would increase synaptic molecule availability, promote synaptic enlargement, and ultimately alter fluctuation characteristics. These findings suggest that activity-independent size fluctuations are sufficient to fully diversify glutamatergic synaptic sizes, with activity-dependent processes primarily setting the scale rather than the shape of size distributions. Moreover, they point to reciprocal relationships between synaptic size fluctuations, size distributions, and synaptic numbers mediated by the innate dynamics of synaptic molecules as they move in, out, and between synapses.SIGNIFICANCE STATEMENT Sizes of glutamatergic synapses vary tremendously, even when formed on the same neuron. This diversity is commonly thought to reflect the outcome of activity-dependent forms of synaptic plasticity, yet activity-independent processes might also play some part. Here we show that in neurons with no history of activity whatsoever, synaptic sizes are no less diverse. We show that this diversity is the product of activity-independent size fluctuations, which are sufficient to generate a full repertoire of synaptic sizes at correct proportions. By combining modeling and experimentation we expose reciprocal relationships between size fluctuations, synaptic sizes and synaptic counts, and show how these phenomena might be connected through the dynamics of synaptic molecules as they move in, out, and between synapses.

Identification of the differentially expressed proteins in nasopharyngeal carcinoma by proteomics

Background

We sought to determine the differences with respect to the proteome of nasopharyngeal tissues between patients with nasopharyngeal carcinoma (NPC) and healthy controls by using sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH^TM-MS) and ingenuity pathway analysis (IPA). Our primary purpose was to identify specific protein markers that can be applied for diagnosis or treatment of NPC.

Methods

The CNE-1, CNE-2 and H1299 cell lines were cultured in stable isotope labeling of amino acids in cell culture (SILAC) medium for 10 generations to obtain labeled proteins. Thirty samples of NPC and 30 healthy control nasopharyngeal tissues were collected from the Department of Otolaryngology of the First Affiliated Hospital of Jinan University. Proteome of the nasopharyngeal tissues were analyzed and compared by SWATH-MS to identify differently expressed proteins. Further, extraction of target proteins and biological pathways was performed by IPA. Super-SILAC technique and liquid chromatography-tandem mass spectrometry were used to verify the reliability of the data obtained using SWATH-MS.

Results

We identified 1,415 differentially expressed proteins between NPC patients and healthy controls. On IPA analysis, EIF2AK2 and MAPK1 proteins were found to be enriched in multiple biological pathways and functional networks.

Conclusions

The differentially expressed proteins EIF2AK2 and MAPK seem to play an important role in the biological network of NPC or may help discover the specific functional proteins of NPC. Further studies are required to identify the pathways and molecular mechanisms that underlie NPC.