Biomedical subjects

Xianglin Yuan

Publications and source records attributed to Xianglin Yuan.

9 recordsLinked to original sources

PubMed2005

Stabilization of ubiquitous mitochondrial creatine kinase preprotein by APP family proteins.

Amyloid precursor protein (APP) is involved in the pathogenesis of Alzheimer's disease (AD). However, the physiological role of APP and its family members is still unclear. To gain insights into APP function, we used a proteomic approach to identify APP interacting proteins. We report here for the first time a direct interaction between the C-terminal region of APP family proteins and ubiquitous mitochondrial creatine kinase (uMtCK). This interaction was confirmed in vitro as well as in cultured cells and in brain. Interestingly, expression of full-length and C-terminal domain of APP family proteins stabilized uMtCK preprotein in cultured cells. Our data suggest that APP may regulate cellular energy levels and mitochondrial function via a direct interaction and stabilization of uMtCK.

Amino Acid Sequence↗

PubMed2005

Proteomics analysis of human cerebrospinal fluid.

Cerebrospinal fluid (CSF) is secreted from several different central nervous system (CNS) structures, and any changes in the CSF composition will accurately reflect pathological processes. Proteomics offers a comprehensive bird's eye view to analyze CSF proteins at a systems level. This paper reviews the variety of analytical methods that have been used for proteomics analysis of CSF, including sample preparation, two-dimensional liquid and gel electrophoresis, mass spectrometry, bioinformatics, and non-gel methods. The differentially expressed CSF proteins that have been identified by proteomics methods are discussed.

Cerebrospinal Fluid Proteins↗

PubMed2005

Human cerebrospinal fluid peptidomics.

Cerebrospinal fluid (CSF) has frequently been extensively studied to explore several different central nervous system (CNS) disorders because it contains proteins, enzymes, hormones, neuropeptides and neurotransmitters that play critical regulatory roles in many different physiological processes. Individual neuropeptidergic systems in CSF have been studied. In theory, peptidomics offers a bird's-eye, comprehensive and systems-level approach to analyze all of the peptidergic systems that have been expressed in CSF at any given time. In this study, low molecular mass (M(r) < 5 kDa) peptides were isolated by ultrafiltration. The isolated peptides, with or without trypsin digestion, were preferentially enriched with a solid-phase extraction cartridge, and the peptides were separated with capillary liquid chromatography and analyzed with on-line quadrupole time-of-flight mass spectrometry (MS). In this proof-of-principle study, the 20 representative MS-characterized peptides were shown to be derived from 12 proteins, among which four proteins, amyloid-like protein 1, secretogranin I, granin-like neuroendocrine peptide precursor and neurosecretory protein VGF, have been shown elsewhere to be either associated with CNS disorders or to play a central role in the CNS. The long-term goals of this peptidomics study are to monitor the changes (amount; modifications) of CSF peptides, clarify the aberrant processing of large intact protein precursors, elucidate the molecular mechanisms of CNS disorders and find biomarkers. This analytical method is effective for the analysis of the human lumbar CSF peptidome.

Adult↗

PubMed2005

Proteomics analysis of prefractionated human lumbar cerebrospinal fluid.

Cerebrospinal fluid (CSF) is produced by the chorioid plexus in the ventricles. It surrounds the brain and bone marrow, and reflects several different disorders of the central nervous system (CNS). Proteomics has been used to analyze CSF in order to discover disease-associated proteins and to elucidate the basic molecular mechanisms that either cause, or result from, CNS disorders. However, some disease-associated proteins are of low-abundance and are difficult to detect. A low total-protein concentration, a high amount of albumin and immunoglobins, and a wide dynamic range (several orders of magnitude) of protein concentration cause several difficulties in the identification of low-abundance CSF proteins. In this study, advantage was taken of the range of different hydrophobic properties of CSF proteins, and a reversed-phase solid-phase extraction (SPE) cartridge was used to prefractionate human lumbar CSF proteins into three separate fractions prior to two-dimensional gel electrophoresis resolution of the proteome. A portion of the high-abundance CSF proteins were removed from two (eluted with 35% and 50% acetonitrile) of the three fractions. Some trace CSF proteins were preferentially enriched in the two fractions, and many proteins were detected in the two-dimensional (2-D) gels of the two fractions. Among the novel proteins identified, sixty-two protein spots that represent forty-two proteins were characterized. Most of the proteins have not been annotated in any previous 2-D map of human CSF, and several have been implicated in CNS diseases. The prefractionation of CSF proteins with SPE, followed by proteomics analysis, provides a new method to explore low-abundance, disease-specific CSF proteins.

Cerebrospinal Fluid Proteins↗

PubMed2005

Effects of hypoxia on expression of P-gp and mutltidrug resistance protein in human lung adenocarcinoma A549 cell line.

To study the effects of hypoxia-on the expression of P-gp and mutltidrug resistance protein in human lung adenocarcinoma A549 cell line, and to explore the probable mechanism of hypoxia in tumor cell of MDR. The expression of hypoxia inducible factor-1 alpha, P-gp and mutltidrug resistance protein was immunohistochemically detected by culturing human lung adenocarcinoma A549 cell under hypoxia (2 % O2) for 24 h. After interaction with adriamycin or cisplatin under hypoxia (2 % O2) for 24 h, the cell survival rate was detected by MTT. Our results showed that the expression of hypoxia inducible factor-1 alpha, P-gp and mutltidrug resistance protein under hypoxia were higher than the expression under normoxia, and correlations between the expression of HIF-1alpha and P-gp or multidrug resistance-associated protein was observed (P< 0.05). The resistance of adriamycin of A549 cell was enhanced under hypoxia. It is concluded that the resistance of tumor chemotherapy is enhanced in hypoxia. The expression of HIF-1alpha is obviously correlated with the expression of P-gp and mutltidrug resistance protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Analysis of DNA ploidy, cell cycle and Ki67 antigen in nasopharyngeal carcinoma by flow cytometry.

The expression of DNA ploidy, the cell cycle and Ki67 antigen in nasopharyngeal carcinoma (NPC) were studied and their relationship with the clinical biological behaviors and prognosis of NPC was evaluated. Biopsied specimens of NPC were made into cell suspension. By using cytometric double labeling Ki67 and DNA method, the expression of DNA ploidy, the cell cycle and Ki67 antigen were analyzed. The patients were followed-up for about 3 years and the relationship between the above-mentioned parameters and the clinical biological behavior and prognosis of NPC were evaluated. Of the 62 cases of NPC, the DNA aneuploid accounted for 29.03%. The S phase cells accounted for 0 to 54% in the cell cycle and the positive expression of Ki67 ranged from 0 to 52%. There were 40 cases of LPI (64.5%) including 15 negative cases and 22 cases of HPI (35.5%) respectively. The DNA anueploid content was positively related to the S phase cells. The patients having a low expression of Ki67 or DNA aneuploid in tumor cells were not sensitive to chemotherapy, liable to metastasis to distant organs and had a poor prognosis, while Ki67 showed no correlation with DNA ploidy and the cell cycle. It was suggested that DNA ploidy and Ki67 could be used as an independent and objective marker to evaluate the radiosensitivity and prognosis of NPC.

Adult↗

PubMed2002

Analysis of the human lumbar cerebrospinal fluid proteome.

Idiopathic low back pain has no known cause, and the molecular basis is unknown. Neuropeptidergic systems have been previously studied, and proteomics methods have been applied in this present study. Proteomics combines high-resolution two-dimensional (2-D) gel electrophoresis, high-sensitivity mass spectrometry, and continuously expanding protein databases. Proteomics offers a comprehensive, bird's-eye view to analyze, at a systems level, all of the proteins in cerebrospinal fluid (CSF) that might contribute to idiopathic low back pain. CSF contains a high salt concentration and low protein concentration. In order to obtain a high-quality 2-D pattern, several sample preparation methods were tested to remove salts - protein precipitation with either acetone or trichloroacetic acid/acetone, or sample treatment with a Bio-Spin column. More spots were visualized on the 2-D gel of human CSF, and a relatively high protein recovery was obtained when a Bio-Spin column was used to process a human CSF sample. Sixty-one protein spots, obtained from 2-D gels with a pH range of either 3-10 or 4-7, were identified by matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and MALDI-post-source decay (PSD)-MS. These 61 protein spots represent 22 proteins; six of those proteins were not annotated in any previously published 2-D maps. Those six proteins are PRO2619, pigment epithelium-derived factor, albumin homolog, kallikrein-6 precursor, DJ717I23.1, and AMBP protein precursor. These protein-mapping data will contribute to the database that will be used in the future to compare the proteomes obtained from the CSF of controls and low back pain patients, to characterize differentially expressed proteins, and to elucidate the biological markers for idiopathic low back pain.

Amino Acid Sequence↗

PubMed2002

Protein identification with Teflon as matrix-assisted laser desorption/ionization sample support.

Protein identification is a critical step in proteomics, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) plays an important role in that identification. Polytetrafluoroethylene (Teflon) was tested as a new MALDI sample support to improve protein identification. The tryptic peptides obtained from a model protein were bound to the surface of a modified MALDI sample holder via the hydrophobic interactions that occur between the Teflon surface and the peptide ion-pairs, and the affinity of alpha-cyano-4-hydroxycinnamic acid for the peptides. During that surface-binding step, the peptide mixture was also desalted and concentrated. A greater number of matched peptides and a larger sequence coverage were obtained for the proteins when Teflon was used as the sample support compared with conventional sample preparation methods and a stainless-steel surface. In addition, the characterization of a small amount of protein was improved with Teflon. Nine silver-stained protein spots obtained from 2-D gel of a human cerebrospinal fluid (CSF) proteome were identified by this method. Among the nine protein spots, peptide 6:c3c fragment and procollagen c-proteinase enhancer were not annotated in any published 2-D map of human CSF. A Teflon MALDI sample support is a low-cost, simple, and effective method that can be used to improve the quality of the MALDI mass spectrum of a complex tryptic peptide mixture, and to achieve a higher level of reliability and success in protein identification.

Animals↗

PubMedDate not supplied

Proteomics analysis of phosphotyrosyl-proteins in human lumbar cerebrospinal fluid.

Cerebrospinal fluid (CSF) is a secretion product of several different central nervous system (CNS) structures, including the choroid plexus in the ventricles. Pathological CNS processes are reflected in the protein composition of CSF. To elucidate the molecular events that occur in the homeostatic and pathological processes of the CNS, the high-throughput characterization of differentially expressed proteins, and of post-translationally modified proteins, is needed for proteomics studies of CSF. Among the post-translational modifications of proteins, phosphorylation is the most common and important mechanism for the reversible regulation of protein function. In this study, CSF phosphotyrosyl (p-Tyr)-proteins were detected with antibodies and were analyzed with proteomics methods. Three different combination methods--1D gel electrophoresis and Western blotting, immunoprecipitation and 2D gel electrophoresis, and 2D gel electrophoresis and Western blotting--were used to detect p-Tyr-proteins in human lumbar CSF samples. Six protein spots, representing four proteins on a 2D Western blot, were identified as p-Tyr-proteins with the 2D gel electrophoresis and Western blotting method. Those four p-Tyr-proteins are kallikrein-6 precursor, complement C4 gamma-chain, gelsolin, and ceruloplasmin precursor. Additionally, four other nonphosphorylated CSF proteins--beta-2-glycoprotein I precursor, fibulin-1 precursor, EGF-containing fibulin-like extracellur matrix protein 1 precursor, and angiotensinogen precursor--were characterized for the first time.

Blotting, Western↗