Soo Jae Lee

Role of protein tyrosine nitration in neurodegenerative diseases and atherosclerosis

Nitric oxide generates reactive nitrosative species, such as peroxynitrite (ONOO−) that may be involved in a number of diseases. ONOO− can mediate protein tyrosine nitration which causes structural changes of affected proteins and leads to their inactivation. Various proteomics and immunological methods including mass spectrometry combined with both liquid and 2-D PAGE, and immunodetection have been employed to identify and characterize nitrated proteins from pathological samples. This review presents the pahtobiological roles of the pathogenic posttranslational modification in neurodegenerative diseases and atherosclerosis.

Lipid MALDI profile classifies non-small cell lung cancers according to the histologic type

We investigated whether direct tissue matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) analysis on lipid may assist with the histopathologic diagnosis of non-small cell lung cancers (NSCLCs). Twenty-one pairs of frozen, resected NSCLCs and adjacent normal tissue samples were initially analyzed using histology-directed, MALDI MS. 2,5-dihydroxybenzoic acid/α-cyano-4-hydroxycinnamic acid were manually deposited on areas of each tissue section enriched in epithelial cells to identify lipid profiles, and mass spectra were acquired using a MALDI-time of flight instrument. A lipid profile that could differentiate cancer and adjacent normal samples with a median accuracy of 92.9% was discovered. Several phospholipids including phosphatidylcholines (PC) {34:1} were overexpressed in lung cancer. Squamous cell carcinomas and adenocarcinomas were found to have different lipid profiles. Discriminatory lipids correctly classified the histology of 80.4% of independent NSCLC surgical tissue samples (41 out of 51) in validation set. MALDI MS image of 11 discriminatory lipids validated their differential expression according to the histologic type in cancer cells of bronchoscopic biopsy samples. PC {32:0} [M+Na](+) (m/z 756.68) and ST-OH {42:1} [M-H](-) (m/z 906.89) were overexpressed in adenocarcinomas. Thus, lipid profiles accurately distinguish tumor from adjacent normal tissue and classify non-small cell lung cancers according to the histologic type.

Selective Enrichment and Mass Spectrometric Identification of Nitrated Peptides Using Fluorinated Carbon Tags

Protein tyrosine nitration (PTN) is a post-translational modification that is related to several acute or chronic diseases. PTN introduces a nitro group in the ortho position of the phenolic hydroxyl group of tyrosine residues. PTN has been shown to be involved in the pathogenesis of inflammatory responses, cancers, and neurodegenerative and age-related disorders. Furthermore, it has been proposed that PTN regulates signal cascades related to nitric oxide (NO·) production and NO-mediated processes. Although nitrated proteins as markers of oxidative stress are confirmed by immunological assays in various affected cells or tissues, it is not known how many different types of proteins in living cells are nitrated. Since protein nitration is a low-abundance post-translational modification, development of an effective enrichment method for nitrated proteins is needed to detect nitrated peptides or proteins from the limited amount of pathophysiological samples. In the present study, we developed an enrichment method using specific chemical tagging. Nitroproteome profiling using chemical tagging and mass spectrometry was validated by model proteins. Furthermore, we successfully identified numerous nitrated proteins from the Huh7 human hepatoma cell line.

Proteomic Analysis for Tissues and Liquid from Bonghan Ducts on Rabbit Intestinal Surfaces

Research on the Bonghan system has recently prompted great interest in the theory proposed by Bong Han Kimin in the early 1960s. In order to study the biochemical characteristics of the Bonghan system, we analyzed Bonghan ducts (BHD) on the surface of rabbit intestines and characterized the liquid in the BHD at the level of the proteome. Proteomic analysis was performed using nano LC-ESI MS/MS. Using a solution digestion technique, we identified 70 different proteins in the liquid of the BHD. We used gel-based digestion to analyze the BHD itself and our results showed the presence of 207 proteins. We used these proteins to analyze gene ontology (GO) to yield insights into biological processes, molecular functions and cellular compartmentalization. Remarkably, GO clustering showed high concentrations of proteins involved in metabolism. These proteins are not usually found in blood, lymph or blood vessels, and thus can be useful for characterizing BHD. It is worth studying their association with stem cells, especially mesenchymal stem cells, cancer cells and myeloid cells.

Chemical Approach for Specific Enrichment and Mass Analysis of Nitrated Peptides

The analysis and detection of 3-nitrotyrosine are biologically and clinically important because protein tyrosine nitration is known to be involved in a number of biological phenomena such as cellular signal transduction, pathogenesis of inflammatory responses, and age-related disorders. However, the main obstacles in the study are low abundance of nitrated species and lack of efficient enrichment methods. Here in, we suggest a new chemical approach to analyze nitrated peptides using mass spectrometry by incorporating specific tagging groups in the peptides through simple chemical transformations. Nitro groups on tyrosine side chains of nitrated peptides were subjected to reduction to give rise to amine which was further converted to metal-chelating motif. Mass analyses verified that Ni(2+)-NTA magnetic agarose beads selectively captured and isolated the modified peptides, i.e., nitrated peptides, by strong and specific metal chelating interactions. We further demonstrated the utility of our approach by detection of nitrated peptides in complex samples such as tryptic peptide mixtures of bovine serum albumin (BSA) and a HeLa cell lysate.

Discovery of the serum biomarker proteins in severe preeclampsia by proteomic analysis

Preeclapsia (PE) is a severe disorder that occurs during pregnancy, leading to maternal and fetal morbidity and mortality. PE affects about 3-8% of all pregnancies. In this study, we conducted liquid chromatographymass spectrometry/mass spectrometry (LC-MS/MS) to analyze serum samples depleted of the six most abundant proteins from normal and PE-affected pregnancies to profile serum proteins. A total of 237 proteins were confidently identified with < 1% false discovery rate from the two groups of duplicate analysis. The expression levels of those identified proteins were compared semiquantitatively by spectral counting. To further validate the candidate proteins with a quantitative mass spectrometric method, selective reaction monitoring (SRM) and enzyme linked immune assay (ELISA) of serum samples collected from pregnant women with severe PE (n = 8) or normal pregnant women (n = 5) was conducted. α2-HS-glycoprotein (AHSG), retinol binding protein 4 (RBP4) and α-1-microglobulin/bikunin (AMBP) and Insulin like growth factor binding protein, acid labile subunit (IGFBP-ALS) were confirmed to be differentially expressed in PE using SRM (P < 0.05). Among these proteins, AHSG was verified by ELISA and showed a statistically significant increase in PE samples when compared to controls.

Effects of the aryl linker and the aromatic substituent on the anti-HCV activities of aryl diketoacid (ADK) analogues

Based on our pharmacophore model of the aryl diketoacids (ADKs), we designed and prepared a series of novel ADK analogues, which showed potent inhibitory activities against the NS5B polymerase in the submicromolar range. Pharmacophore-guided docking study revealed that the antiviral activities of the ADKs are highly dependent upon the aryl linker as well as the size and position of the aromatic substituent. It is of another importance that, unlike previously reported ADKs, three ADK analogues synthesized in this study effectively blocked Hepatitis C Virus (HCV) replication in the replicon systems.

Composition of the extracellular matrix of lymphatic novel threadlike structures: Is it keratin?

Background. The lumen of novel threadlike structures (NTSs) is enclosed by a single layer of endothelial cells surrounded by extracellular matrix (ECM). We hypothesized that collagen may be a component of the ECM associated with lymphatic NTSs. Methods. Six female New Zealand white rabbits were anesthetized, and the NTS structures within lymphatic vessels were identified by contrast-enhanced stereomicroscopy or alcian blue staining. Isolated NTS specimens were stained with acridine orange, YOYO-1, and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI). The structural and molecular composition of the ECM was investigated using transmission electron microscopy (TEM), electrospray ionization-mass spectrometry, and proteomic analysis. Results. The lymph vessel wall was stained red by DiI, and rod-shaped nuclei were stained green by YOYO-1. The area surrounding the NTS was also stained red and contained green rod-shaped nuclei. TEM images showed that the NTS consisted of many ECM fibers and the ECM fibers appeared to be ~100 nm in diameter and had narrowly spaced striated bands. Proteomic analysis of the lymphatic NTS-associated ECM identified 4 proteins: keratin 10, cytokeratin 3, cytokeratin 12, and soluble adenylyl cyclase. Conclusion. The TEM study suggested that the lymphatic NTS-associated ECM did not contain collagen. This was confirmed by proteomic analysis, which showed that keratin was the major component of the ECM.