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Results for “targeted proteomic analysis”

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PubMed2025

Stage-dependent proteomic alterations in aqueous humor of diabetic retinopathy patients based on data-independent acquisition and parallel reaction monitoring.

BACKGROUND: Diabetic retinopathy (DR), a microvascular complication of diabetes mellitus (DM), represents the predominant cause of preventable vision loss in working-age populations globally. While the pathophysiological mechanisms underlying DR progression remain incompletely understood, our study employs comprehensive proteomic profiling of aqueous humor (AH) to identify stage-specific biomarkers and therapeutic targets in type 2 diabetes mellitus (T2DM) patients across DR progression. METHODS: Utilizing data-independent acquisition (DIA) mass spectrometry, we quantified AH proteomes in a discovery cohort comprising 24 subjects: 18 T2DM patients stratified by DR severity [6 non-DR, 6 non-proliferative DR (NPDR), 6 proliferative DR (PDR)] and 6 cataract controls without diabetes (non-DM). Validation cohort analysis (including 10 AH samples in each group) was performed using parallel reaction monitoring (PRM) strategy for verification of target proteins. Comprehensive bioinformatics analyses included gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, protein-protein interaction (PPI) network construction, receiver operating characteristic (ROC) curve analysis, and ConnectivityMap (Cmap)-based drug prediction. RESULTS: Proteomic profiling identified 739 quantifiable AH proteins (62% extracellular) with clear separation among the four clinical stages in the discovery cohort. GSEA uncovered altered expression of proteins mainly related to complement and coagulation cascades, folate metabolism, and the selenium micronutrient network in patients with DR. WGCNA-derived protein modules yielded 83 PRM-validated targets, including 5 hub proteins differentiating NPDR from non-DR and 33 hub proteins showed significant upregulation in PDR versus NPDR comparison. Clinical correlation analysis identified F2, FGG, FGB, RBP4, AMBP, VTN, C8A, CPB2, and C2 associated with clinical traits. C6, FAM3C, SPP1, and JCHAIN levels were altered post-anti-VEGF treatment. Pharmacological prediction identified potential therapeutic compounds, including perindopril, triciribine, and XAV-939 for NPDR, and topiramate, triciribine, and vecuronium for PDR. CONCLUSION: This study established a comprehensive AH proteomic signature of DR progression, offering insights into the pathogenesis of DR and highlighting potential biomarkers and novel therapeutic targets.

Humans↗

PubMed2004

Advances in recombinant antibody microarrays.

Antibody microarrays, one emerging class of proteomic technologies, have broad applications in proteome analysis, disease diagnostics and quantitative analysis. Compared to DNA microarrays, protein targets have significantly more complex interactions with their ligands such as antibodies. To introduce antibody microarrays for clinical diagnostics and thus to complement or replace conventional immunoassays, several new developments are addressed. We discuss different microarray surfaces, immobilization techniques, detection systems and advantages and disadvantages of antibody microarrays compared to standard clinical techniques. Currently, the probes with highest specificity, well-characterized binding properties, and the possibility of large-scale production using display libraries are recombinant antibodies.

Animals↗

PubMed2003

Proteome analysis of vinca alkaloid response and resistance in acute lymphoblastic leukemia reveals novel cytoskeletal alterations.

Vinca alkaloids are used widely in the treatment of both childhood and adult cancers. Their cellular target is the beta-tubulin subunit of alpha/beta-tubulin heterodimers, and they act to inhibit cell division by disrupting microtubule dynamics. Despite the effectiveness of these agents, drug resistance is a major clinical problem. To identify the underlying mechanisms behind vinca alkaloid resistance, we have performed high resolution differential proteome analysis. Treatment of drug-sensitive human leukemia cells (CCRF-CEM) with vincristine identified numerous proteins involved in the cellular response to vincristine. In addition, differential protein expression was analyzed in leukemia cell lines selected for resistance to vincristine (CEM/VCR R) and vinblastine (CEM/VLB100). This combined proteomic approach identified 10 proteins altered in both vinca alkaloid response and resistance: beta-tubulin, alpha-tubulin, actin, heat shock protein 90beta, 14-3-3tau, 14-3-3epsilon, L-plastin, lamin B1, heterogeneous nuclear ribonuclear protein-F, and heterogeneous nuclear ribonuclear protein-K. Several of these proteins have not previously been associated with drug resistance and are thus novel targets for elucidation of resistance mechanisms. In addition, seven of these proteins are associated with the tubulin and/or actin cytoskeletons. This study provides novel insights into the interrelationship between the microtubule and microfilament systems in vinca alkaloid resistance.

Actins↗

PubMed2001

Proteome analysis and morphological studies reveal multiple effects of the immunosuppressive drug mycophenolic acid specifically resulting from guanylic nucleotide depletion.

Mycophenolic acid (MPA), one of the most promising immunosuppressive drugs recently developed, is a potent inhibitor of IMP dehydrogenase, the first committed step toward GMP synthesis. We found that all the drug effects on yeast cells were prevented by bypassing GMP synthesis, thus confirming the high specificity of MPA. Although the primary target of MPA is clearly identified, we aimed to further understand how GTP depletion leads to growth arrest and developed a new approach based on proteome analysis combined with overexpression studies. Essential proteins down-expressed in the presence of MPA were identified by protein two-dimensional gel analysis and subsequently overexpressed in yeast. Two such proteins, Cdc37p and Sup45p, when overexpressed allowed partial relief of MPA toxicity, strongly suggesting that their lower amount after MPA treatment significantly contributed to the MPA effect. These conserved proteins involved in cell cycle progression and translation are therefore important secondary targets for MPA. Our data establish that MPA effects occur through inhibition of a unique primary target resulting in guanine nucleotides depletion, thereby affecting multiple cellular processes.

Base Sequence↗

PubMed2003

An integrated approach to identifying chemically induced posttranslational modifications using comparative MALDI-MS and targeted HPLC-ESI-MS/MS.

Identification of multiple and novel posttranslational modifications remains a major challenge in proteomics. The present approach uses comparative analysis by matrix-assisted laser/desorption ionization (MALDI) MS of proteolytic digests from control and treated proteins to target differences due to modifications, without initial assumption as to type or residue localization. Differences between modified and unmodified digest MS spectra highlight peptides of interest for subsequent tandem mass spectrometry (MS/MS) analysis. Targeted HPLC-electrospray ionization (ESI)-MS/MS is then used to fragment peptides, and manual de novo sequencing is used to determine the amino acid sequence and type of modification. This strategy for identifying posttranslational modifications in an unbiased manner is particularly useful for finding modifications produced by exogenous chemicals. Successful characterization of chemically induced posttranslational modifications and novel chemical adducts is given as an example of the use of this strategy. Histone H4 from butyrate-treated LLC-PK1 cells is separated on a gel into bands representing different overall charge state. Bands are analyzed by comparative MALDI-MS and LC-MS/MS to identify the sites of methylation and acetylation. Previous attempts to identify chemically adducted proteins in vivo have been unsuccessful in part due to a lack of understanding of the final adduct form. Cytochrome c is adducted in vitro with benzoquinone, an electrophilic metabolite of benzene capable of interacting with nucleophilic sites within proteins. De novo sequencing identifies a novel cyclized diquinone adduct species as the major reaction product, targeting Lys and His residues at two specific locations on the protein surface. This unpredicted reaction product is characterized using our unbiased methods for detection and demonstrates the important influence of protein structure on chemical adduction.

Acetylation↗

PubMed2026

Multi-omics identification of therapeutic targets of compound sappan decoction in hepatocellular carcinoma.

BACKGROUND: Compound sappan decoction (CSD) is a multi-herbal traditional Chinese medicine formulation with clinical relevance in hepatocellular carcinoma (HCC). However, its therapeutic mechanisms remain unclear. METHODS: Bioactive compounds of CSD were identified and standardized using pharmacological and chemical databases. Potential targets were predicted via multiple target inference platforms. HCC-related genes were curated from comprehensive disease databases. Summary-data-based Mendelian randomization (SMR) was conducted to infer causal relationships between compound targets and HCC risk using large-scale quantitative trait loci (QTL) datasets and HCC genome-wide association study data. Colocalization analysis, protein-protein interaction (PPI) network construction, and GO/KEGG enrichment were performed on SMR-identified targets. Molecular docking evaluated binding affinities of representative compounds to prioritized targets. RESULTS: A total of 784 overlapping genes between predicted CSD targets and HCC-related genes were subjected to SMR analysis. Among these, 22 targets were significantly associated with HCC risk based on transcriptomic or proteomic QTLs and showed colocalization evidence. Notably, four targets (ADRB2, APOE, SYK, and PGF) were supported by both replication in an independent cohort and strong colocalization. These 22 targets were enriched in apoptosis, PI3K-Akt signaling, redox metabolism, and detoxification pathways. PPI analysis revealed central hubs including MMP9, BCL2, CASP1, and MCL1. Molecular docking demonstrated strong binding of APOE to quercetin, PGF to luteolin-7-olate, and SYK to kaempferol. CONCLUSIONS: CSD may exert therapeutic effects on HCC through modulation of genetically validated targets involved in tumor progression, inflammation, and metabolic reprogramming, supporting its potential clinical utility as an adjunctive treatment strategy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at https://doi.org/10.1007/s12672-026-04740-8.

Caesalpinia↗

PubMed2005

Towards replacing closed with open target selection strategies.

Increasingly, microbial production processes are being improved by targeted approaches. In directed strain improvement, the selection of the relevant targets is the limiting step in metabolic engineering. Currently, the identification of leads is still a random process relying largely on expert knowledge. Recently, this approach has been complemented by metabolic flux and control analysis approaches. However, both are closed approaches, and biological processes or interactions that are not currently known to exist, or to be important for bioproduct formation, are not taken into account. By contrast, the recently introduced functional genomics technologies enable an open approach towards target selection. In the near future, we might see that metabolomics, and its integration with transcriptomics and/or proteomics into a systems biology approach, in combination with multivariate data analysis tools, will become of increasing importance for the unbiased selection and ranking of targets, not only for strain improvement but also for bioprocess improvement.

Bacteria↗

PubMed1999

Candida albicans pathogenicity: a proteomic perspective.

Candida albicans is an opportunistic fungus which causes both superficial infections and life-threatening systemic candidiasis in immunocompromised hosts such as AIDS patients, people with cancer, or other immunosuppressed individuals. Virulence factors for this fungus include the ability to adhere to host tissues, production of tissue damaging secreted enzymes, and changes in morphological form that may enhance tissue penetration and avoidance of immune surveillance. Treatment of candidiasis patients is hampered by a limited choice of antifungal agents and the appearance of clinical isolates resistant to azole drugs. Proteome analysis involves the separation and isolation of proteins by two-dimensional gel electrophoresis and their identification and characterization by mass spectrometry. The systematic application of this methodology to C. albicans is in its infancy, but is progressing rapidly. Comparing protein profiles between avirulent and virulent C. albicans strains, between drug-sensitive and -resistant strains, or between different morphological forms, could identify key control and effector proteins. There are difficulties, however, associated with the display of low abundance and cell envelope-associated proteins and the choice of conditions for obtaining suitable C. albicans cells. This article describes the potential of applying proteome analysis to C. albicans in order to better understand pathogenicity and identify new antifungal targets.

Candida albicans↗

PubMed2006

Proteomic analysis of ischemia-reperfusion injury upon human liver transplantation reveals the protective role of IQGAP1.

Ischemia-reperfusion injury (IRI) represents a major determinant of liver transplantation. IRI-induced graft dysfunction is related to biliary damage, partly due to a loss of bile canaliculi (BC) integrity associated with a dramatic remodeling of actin cytoskeleton. However, the molecular mechanisms associated with these events remain poorly characterized. Using liver biopsies collected during the early phases of organ procurement (ischemia) and transplantation (reperfusion), we characterized the global patterns of expression and phosphorylation of cytoskeleton-related proteins during hepatic IRI. This targeted functional proteomic approach, which combined protein expression pattern profiling and phosphoprotein enrichment followed by mass spectrometry analysis, allowed us to identify IQGAP1, a Cdc42/Rac1 effector, as a potential regulator of actin cytoskeleton remodeling and maintenance of BC integrity. Cell fractionation and immunohistochemistry revealed that IQGAP1 expression and localization were affected upon IRI and related to actin reorganization. Furthermore using an IRI model in human hepatoma cells, we demonstrated that IQGAP1 silencing decreased the basal level of actin polymerization at BC periphery, reflecting a defect in BC structure coincident with reduced cellular resistance to IRI. In summary, this study uncovered new mechanistic insights into the global regulation of IRI-induced cytoskeleton remodeling and led to the identification of IQGAP1 as a regulator of BC structure. IQGAP1 therefore represents a potential target for the design of new organ preservation strategies to improve transplantation outcome.

Actins↗

PubMed2002

Proteomic analysis of human lysosomes: application to monocytic and breast cancer cells.

To date, about fifty lysosomal hydrolases have been identified, and most of them are targeted towards the lysosomes through a specific mannose-6-phosphate (M-6-P) tag. As more lysosomal hydrolases were expected to be discovered, we performed a proteomic study of soluble lysosomal proteins. Human cells were induced to secrete M-6-P proteins which were affinity purified on immobilized M-6-P receptor. The purified proteins were resolved by two-dimensional electrophoresis and analyzed by mass spectrometry. Twenty-two proteins were identified, among which 16 were well-known lysosomal hydrolases. The remaining species distributed as follows: epididymis-specific alpha-mannosidase is a new mannosidase homolog, cystatin F and CREG (cellular repressor of E1A-stimulated genes) were previously identified as M-6-P proteins (Journet et al., Electrophoresis 2000, 21, 3411-3419), and the last three, which are not hydrolases, were up to now considered as nonlysosomal. This two-dimensional reference map of human U937 M-6-P proteins was afterwards used for comparison with M-6-P proteins purified either from U937 differentiated into macrophage-like cells, or from human breast cancer MCF7 cells. Phorbol ester induced differentiation of U937 cells led to limited proteolytic cleavage or maturation of a discrete number of hydrolases. Five additional lysosomal hydrolases were identified from MCF7 samples. These results prove the usefulness of such a procedure to analyze the lysosomal content of various cell lines, to discover new M-6-P proteins, as well as to point towards unknown biological processes.

Animals↗

PubMed2001

Hepatocellular carcinoma: from bedside to proteomics.

Hepatocellular carcinoma (HCC or hepatoma) is the most common primary cancer of the liver. It is responsible for approximately one million deaths each year, mainly in underdeveloped and developing countries. The aetiological factors identified in the development of HCC included persistent infection by hepatitis B and hepatitis C viruses, and exposure to aflatoxins. Although immunization can protect individuals from being infected by the hepatitis B virus, the early detection of HCC in those who have been infected by the virus remains a challenge. Thus most HCCs present late and are not suitable for curative treatment. Hence there is a tremendous interest and urgency to identify novel HCC diagnostic marker(s) for early detection, and tumour specific disease associated proteins as potential therapeutic targets in the treatment of HCC. Screening for these HCC proteins has been facilitated by proteomics, a key technology in the global analysis of protein expression and understanding gene function. Present and earlier proteome analyses of HCC have used predominantly experimental in vitro systems. The protein expression profiles of several hepatoma cell lines such as HepG2, Huh7, SK-Hep1, and Hep3B have been compared with normal liver, and nontransformed cell lines (Chang and WRL-68), while a comprehensive proteome analysis to create a protein database was carried out for the cell line HCC-M. In the future, proteome analyses utilizing tumour tissues, which reflect the pathological state of HCC more closely, will be undertaken. This work will complement the gene expression studies of HCC which are already underway. Efforts have also been directed at the proteome analysis of hepatic stellate cells, as these cells play an important role in liver fibrosis. Since liver fibrosis is reversible but not cirrhosis, it is of considerable importance to identify therapeutic targets that can slow its progression.

Amino Acid Sequence↗

PubMed2003

Combined use of proteomic analysis and enzyme activity assays for metabolic pathway analysis of glycerol fermentation by Klebsiella pneumoniae.

The fed-batch fermentation of glycerol to 1,3-propanediol by Klebsiella pneumoniae displayed an unusual dynamic behavior that can be clearly divided into four distinct phases according to cell growth and CO(2) evolution rate. Metabolism changed significantly during the different phases as reflected by the varied specific rates of substrate consumption and product formation. An assay of activities of the three initial enzymes of glycerol metabolism, namely glycerol dehydratase (GDHt), glycerol dehydrogenase (GDH), and 1,3-propanediol-oxidoreductase (PDOR), showed apparently different patterns of expression. To understand the culture dynamics and patterns of enzyme formation at a more systemic level we analyzed the expression patterns of intracellular proteins of K. pneumoniae from different phases of the fed-batch fermentation using two-dimensional gel electrophoresis (2DE). Two new enzymes, namely a phosphoenolpyruvate-dependent dihydroxyacetone kinase (DHAK II) and a hypothetical oxidoreductase (HOR), which are directly related to glycerol metabolism and 1,3-propanediol formation, were identified among the highly expressed proteins. The changes in expression of these new enzymes and several other proteins identified from the 2DE analysis helped to understand not only the dynamic behavior of the fed-batch fermentation reported in this work but also some previously insufficiently understood phenomena related to this fermentation process. In particular, we demonstrated the combined use of proteomic analysis and enzyme activity assay data for metabolic pathway analysis and for a better identification of targets for bioprocess improvement.

Amino Acid Sequence↗

PubMed2002

Towards complete analysis of the platelet proteome.

Platelets exert a crucial function in haemostasis, wound repair, and the formation of vascular plugs, underlying thrombotic diseases such as stroke and myocardial infarction. Analysis of platelet biochemistry is largely dependent on protein analysis as platelets are anucleated cells providing little analytical target for DNA or RNA based strategies. Here we present data from our analysis of the human platelet proteome, the entire set of proteins building a platelet at a given point in time. Proteins were separated by two-dimensional electrophoresis (2-DE) using broad and narrow range pH gradients in the isoelectric focusing step. Consequently, a high-resolution 2-DE proteome map has been generated that comprises approximately 2300 different protein features. From the 536 protein features detected in the 4-5 pI range 284 features were identified by electrospray ionisation time of flight tandem mass spectrometry. These 284 proteins originate from 123 different open reading frames. This includes the five human proteins KIAA0193, KIAA0573, KIAA0830, WUGSC:H_DJ0777O23 protein, and cytokine receptor related protein 4, all isolated for the first time. The data are discussed with regard to proteome characteristics, protein function, and the high prevalence of signalling molecules. This study contributes to a more thorough and holistic understanding of platelet biology, helping to build the basis for future identification of new drug targets and therapeutic strategies.

Blood Platelets↗

PubMed2006

Proteomic analysis of the E2F1 response in p53-negative cancer cells: new aspects in the regulation of cell survival and death.

E2F1 is an essential transcription factor that regulates cell-cycle progression and apoptosis. Overexpression of E2F1 sensitizes neoplastic cells to apoptosis and leads to tumor growth suppression, making it an interesting target for anticancer therapy. Use of E2F1 as a therapeutic, however, requires a detailed knowledge of the mechanisms by which it controls cellular proliferation and apoptosis, and of other potential E2F1 activities. In this study, a differential proteome analysis was performed to identify proteins associated with E2F1 activity in inducible p53-deficient Saos-2ERE2F1 osteosarcoma cells. 2-DE revealed a distinct protein profile at 32 h after E2F1 activation. Thirty-three proteins were reproducibly identified as either up-regulated or down-regulated. Proteins were identified by MALDI-MS. They included hitherto unknown E2F1 target proteins of cytoskeletal origin, chaperones, enzymes, proteasomal proteins, and several heterogeneous nuclear ribonucleoproteins, suggesting its role in the ER-stress response, protein degradation, and modulation of pre-mRNA splicing. Protein analysis-derived results were verified by Western blot using representative protein candidates. Thirteen identified proteins were the products of genes known to be cancer related. Thus, proteome analysis provides new information about the complexity of E2F1 activities in human cancer cells that may be considered when using E2F1 as a drug.

Apoptosis↗

PubMed2006

High-throughput affinity mass spectrometry.

Affinity mass spectrometry (AMS) is a proteomics approach for selectively isolating target protein(s) from complex biological fluids for mass spectrometric analysis. The resulting high-content mass spectrometry (MS) data show the unique MS protein signatures (wild-type, posttranslationally modified, as well as genetically modified forms of the protein target) that are present within a biological sample. Information regarding such protein diversity is normally lost in classical proteomic or immunoassay analyses. This chapter presents a step-by-step description of high-throughput AMS in the population proteomic screening of the human plasma protein cystatin C.

Amino Acid Sequence↗

PubMed2026

Targeting STK17B kinase activates ferroptosis and suppresses drug resistance in multiple myeloma.

The progression of multiple myeloma (MM), an incurable malignancy of plasma cells, is often associated with the suppression of ferroptosis, a type of cell death driven by iron-dependent lipid peroxidation. The mechanisms underlying this suppression remain largely unknown. Here, we identified serine/threonine kinase 17b (STK17B) kinase as a critical suppressor of ferroptosis in MM. Elevated levels of STK17B are associated with poor overall survival in patients with MM, and STK17B expression is significantly higher in relapsed vs newly diagnosed MM cases. We found that inhibiting STK17B in MM cells increased the labile iron pool, enhanced lipid peroxidation, and sensitized cells to conventional anti-MM therapies. Notably, an orally available, in-house-generated STK17B inhibitor induced ferroptosis and significantly reduced tumor growth in MM xenograft mouse models. Mechanistically, proximity labeling assay combined with the phospho-proteomic analysis identified 2 major regulators of iron uptake and transport as direct targets of STK17B: iron-responsive element binding protein 2 (IREB2), and heat shock protein family B member 1 (HSPB1). We demonstrated that STK17B phosphorylates critical regulatory sites on IREB2 (S157) and HSPB1 (S15), thereby modulating the balance between IREB2 and HSPB1 downstream effectors, proferroptotic transferrin receptor, and antiferroptotic ferritin heavy chain proteins. Furthermore, we demonstrated that STK17B indirectly maintains activating phosphorylation of STAT3, a ferroptosis suppressor and a major driver of MM pathobiology. Our findings uncovered a clinically relevant and targetable STK17B-pIREB2S157/pHSPB1S15 signaling axis that suppresses ferroptosis and contributes to drug resistance in MM.

Ferroptosis↗

PubMed2004

Characterization of anti-inflammatory compounds using transcriptomics, proteomics, and metabolomics in combination with multivariate data analysis.

The discovery of new anti-inflammatory drugs is often based on an interaction with a specific target, although other pathways often play a primary or secondary role. Anti-inflammatory drugs can be categorized into classes, based on their mechanism of action. In this article we investigate the possibility to characterize novel anti-inflammatory compounds by three holistic methods. For this purpose, we make use of macrophage-like U937 cells which are stimulated with LPS in the absence or presence of an anti-inflammatory compound. Using micro-arrays, 2-D gel electrophoresis and a LC-MS method for lipids the effects on the transcriptome, proteome and metabolome of the exposed cells is investigated. The expression patterns are subsequently analyzed using in-house developed pattern recognition tools. Using the methods described above, we have examined the effects of six anti-inflammatory compounds. Our results demonstrate that different classes of anti-inflammatory compounds show distinct and characteristic mRNA, protein, and lipid expression patterns, which can be used to categorise known molecules and to discover and classify new leads. The potential of our approach is illustrated by the analysis of several beta (2)-adrenergic agonists (beta2-agonists). In addition to their primary pharmacological target, beta2-agonists posses certain anti-inflammatory properties. We were able to show that zilpaterol, a poorly characterized beta2-agonist, gives rise to an almost identical expression pattern as the beta2-agonists clenbuterol and salbutamol. Furthermore we have identified specific mRNA, protein and lipid markers for the anti-inflammatory compounds investigated in this study.

Adrenergic beta-2 Receptor Agonists↗

PubMed2005

Oxidative modification of proteasome: identification of an oxidation-sensitive subunit in 26 S proteasome.

Reactive oxygen species (ROS) have the potential to damage cellular components, such as protein, resulting in loss of function and structural alteration of proteins. The oxidative process affects a variety of side amino acid groups, some of which are converted to carbonyl compounds. We have previously shown that a prostaglandin D2 metabolite, 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), is the potent inducer of intracellular oxidative stress on human neuroblastoma SH-SY5Y cells [Kondo, M., Oya-Ito, T., Kumagai, T., Osawa, T., and Uchida, K. (2001) Cyclopentenone prostaglandins as potential inducers of intracellular oxidative stress, J. Biol. Chem. 276, 12076-12083]. In the present study, to elucidate the molecular mechanism underlying the oxidative stress-mediated cell degeneration, we analyzed the protein carbonylation on SH-SY5Y cells when these cells were submitted to an endogenous inducer of ROS production. Upon exposure of SH-SY5Y cells to this endogenous electrophile, we observed significant accumulation of protein carbonyls within the cells. Proteomic analysis of oxidation-sensitive proteins showed that the major intracellular target of protein carbonylation was one of the regulatory subunits in 26 S proteasome, S6 ATPase. Accompanied by a dramatic increase in protein carbonyls within S6 ATPase, the electrophile-induced oxidative stress exerted a significant decrease in the S6 ATPase activities and a decreased ability of the 26 S proteasome to degrade substrates. Moreover, in vitro oxidation of 26 S proteasome with a metal-catalyzed oxidation system also confirmed that S6 ATPase represents the most oxidation-sensitive subunit in the proteasome. These and the observation that down-regulation of S6 ATPase by RNA interference resulted in the enhanced accumulation of ubiquitinated proteins suggest that S6 ATPase is a molecular target of ROS under conditions of electrophile-induced oxidative stress and that oxidative modification of this regulatory subunit of proteasome may be functionally associated with the altered recognition and degradation of proteasomal substrates in the cells.

Amino Acid Sequence↗