Biomedical subjects

Yuwen Cong

Publications and source records attributed to Yuwen Cong.

9 recordsLinked to original sources

PubMed2006

Mitochondrial location of severe acute respiratory syndrome coronavirus 3b protein.

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV), a distant member of the Group 2 coronaviruses, has recently been identified as the etiological agent of severe acute respiratory syndrome (SARS). The genome of SARS-CoV contains four structural genes that are homologous to genes found in other coronaviruses, as well as six subgroup-specific open reading frames (ORFs). ORF3 encodes a predicted 154-amino-acid protein that lacks similarity to any known protein, and is designated 3b in this article. We reported previously that SARS-CoV 3b is predominantly localized in the nucleolus, and induces G0/G1 arrest and apoptosis in transfected cells. In this study, we show that SARS-CoV 3b fused with EGFP at its N- or C- terminus co-localized with a mitochondria-specific marker in some transfected cells. Mutation analysis of SARS-CoV 3b revealed that the domain spanning amino acids 80 to 138 was essential for its mitochondria localization. These results provide new directions for studies of the role of SARS-CoV 3b protein in SARS pathogenesis.

Animals↗

PubMed2006

Interaction between Snapin and G-CSF receptor.

Granulocyte colony-stimulating factor (G-CSF) is the major cytokine involved in the control of neutrophil development. G-CSF activates the special receptor, the G-CSF receptor (GCSF-R), which subsequently triggers multiple signaling events. To obtain more interactive molecules with GCSF-R and to further understand the cellular signaling mechanism of GCSF-R, yeast two-hybrid system was used to screen a mouse liver library. Here, the interaction of GCSF-R and Snapin was found by yeast two-hybrid experiment, and the interaction of the two proteins was further confirmed by GST pull-down experiment, mammalian two-hybrid experiment and co-immunoprecipitation study. Moreover, the immuno-fluorescence assay was shown that the two proteins of GCSF-R with Snapin were co-localized in the cytoplasm and plasma membrane. The region of C-terminal GCSF-R between box2 and box3, including the residue Tyr703, was responsible for the interaction with Snapin. These data suggested that Snapin is a new interactive protein of GCSF-R.

Animals↗

PubMed2006

Macrophage migration inhibitory factor interacts with HBx and inhibits its apoptotic activity.

HBx, a transcriptional transactivating protein of hepatitis B virus (HBV), is required for viral infection and has been implicated in virus-mediated liver oncogenesis. However, the precise molecular mechanism remains largely elusive. We used the yeast two-hybrid system to identify that HBx interacts with MIF directly. Macrophage migration inhibitory factor (MIF) is implicated in the regulation of inflammation, cell growth, and even tumor formation. The interaction between HBx and MIF was verified with co-immunoprecipitation, GST pull-down, and cellular colocalization. The expression of MIF was up-regulated in HBV particle producing cell 2.2.15 compared with HepG2 cell. Both HBx and MIF cause HepG2 cell G(0)/G(1) phase arrest, proliferation inhibition, and apoptosis. However, MIF can counteract the apoptotic effect of HBx. These results may provide evidence to explain the link between HBV infection and hepatocellular carcinoma.

Apoptosis↗

PubMed2006

Expression and characterization of earthworm Eisenia foetida lumbrokinase-3 in Pichia pastoris.

Lumbrokinase-3 (LK-3, AY438622), first cloned from the earthworm Eisenia foetida in our laboratory, is a component of earthworm fibrinolytic enzymes. In this study, cDNA encoding the LK-3 gene was sub-cloned into yeast pPIC9K expression vector and transformed into the Pichia pastoris GS115 cells by electroporation. High level expression of LK-3 in yeast cells was confirmed with a different induction time. The activity of expressed LK-3 was observed in fibrin plates. In addition, the expressed LK-3 protein could dissolve fibrinogen and bovine serum albumin. The use of this system for the high level production of biological protein is implicated from this study.

Animals↗

PubMed2005

SARS coronavirus 7a protein blocks cell cycle progression at G0/G1 phase via the cyclin D3/pRb pathway.

The genome of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) contains four structural genes that are homologous to genes found in other coronaviruses, and also contains six subgroup-specific open reading frames (ORFs). Expression of one of these subgroup-specific genes, ORF7a, resulted in apoptosis via a caspase-dependent pathway. Here, we observed that transient expression of ORF7a protein fused with myc or GFP tags at its N or C terminus inhibited cell growth and prevented BrdU incorporation in different cultural cells, suggesting that ORF7a expression may regulate cell cycle progression. Analysis by flow cytometry demonstrated that ORF7a expression was associated with blockage of cell cycle progression at G0/G1 phase in HEK 293 cells after 24 to 60 h post-transfection. Similar results were observed in COS-7 and Vero cells. Mutation analysis of ORF7a revealed that the domain spanning aa 44-82 of 7a protein was essential for its cytoplasmic localization and for induction of the cell cycle arrest. After analyzing the cellular proteins involving in regulation of cell cycle progression, we demonstrated that ORF7a expression was correlated with a significant reduction of cyclin D3 level of mRNA transcription and expression, and phosphorylation of retinoblastoma (Rb) protein at ser795 and ser809/811, not with the expression of cyclin D1, D2, cdk4 and cdk6 in HEK 293 cells. These results suggest that the insufficient expression of cyclin D3 may cause a decreased activity of cyclin D/cdk4/6, resulting in the inhibition of Rb phosphorylation. Accumulation of hypo- or non-phosphorylated pRb thus prevents cell cycle progression at G0/G1 phase.

Animals↗

PubMed2005

G0/G1 arrest and apoptosis induced by SARS-CoV 3b protein in transfected cells.

Severe Acute Respiratory Syndrome coronavirus (SARS-CoV), cause of the life-threatening atypical pneumonia, infects many organs, such as lung, liver and immune organ, and induces parenchyma cells apoptosis and necrosis. The genome of SARS-CoV, not closely related to any of the previously characterized coronavirus, encodes replicase and four major structural proteins and a number of non-structural proteins. Published studies suggest that some non-structural proteins may play important roles in the replication, virulence and pathogenesis of viruses. Among the potential SARS-CoV non-structural proteins, 3b protein (ORF4) is predicted encoding 154 amino acids, lacking significant similarities to any known proteins. Till now, there is no report about the function of 3b protein. In this study, 3b gene was linked with the EGFP tag at the C- terminus. Through cell cycle analysis, it was found that over-expression of 3b-EGFP protein in Vero, 293 and COS-7 cells could induce cell cycle arrest at G0/G1 phase, and that especially in COS-7 cells, expression of 3b-EGFP was able to induce the increase of sub-G1 phase from 24 h after transfection, which was most obvious at 48 h. The apoptosis induction of 3b fusion protein in COS-7 cells was further confirmed by double cell labeling with 7-AAD and Annexin V, the function of 3b protein inducing cell G0/G1 arrest and apoptosis may provide a new insight for further study on the mechanism of SARS pathogenesis.

Animals↗

PubMed2005

Nucleolar localization of non-structural protein 3b, a protein specifically encoded by the severe acute respiratory syndrome coronavirus.

The open reading frame 3 (ORF3) of the severe acute respiratory syndrome coronavirus (SARS-CoV) genome encodes a predicted 154-amino acid protein, which lacks similarities to any known protein, and is named 3b. In this study, it was shown that 3b protein was predominately localized to nucleus with EGFP tag at its N- or C-terminus. The localization patterns were similar in different transfected cells. Immuno-fluorescence assay revealed that 3b protein was co-localized well with C23 in nucleolus. C23, B23 and fibrillarin all are important nucleolar proteins, which localize in the region of the nucleolus. Co-transfection of p3b-EGFP with pC23-DsRed, pB23-DsRed and pfibrillarin-DsRed further confirmed 3b's nucleolus localization. With construction of serial truncated mutants of 3b, a region (residues 134-154 aa) responsible for nucleolar localization was determinated in 3b protein. These results provide a new insight for further functional studies of SARS-CoV 3b protein.

Amino Acid Sequence↗

PubMed2005

Subcellular localization and membrane association of SARS-CoV 3a protein.

SARS-CoV 3a protein was a unique protein of SARS coronavirus (SARS-CoV), which was identified in SARS-CoV infected cells and SARS patients' specimen. Recent studies revealed that 3a could interact specifically with many SARS-CoV structural proteins, such as M, E and S protein. Expressed 3a protein was reported to localize to Golgi complex in SARS-CoV infected cells. In this study, it was shown that 3a protein was mainly located in Golgi apparatus with different tags at N- or C-terminus. The localization pattern was similar in different transfected cells. With the assay of truncated 3a protein, it was shown that 3a might contain three transmembrane regions, and the second or third region was properly responsible for Golgi localization. By ultra-centrifugation experiment with different extraction buffers, it was confirmed that 3a was an integral membrane protein and embedded in the phospholipid bilayer. Immunofluorescence assay indicated that 3a was co-localized with M protein in Golgi complex in co-transfected cells. These results provide a new insight for further study of the 3a protein on the pathogenesis of SARS-CoV.

Animals↗

PubMed2004

Regulation of LIP level and ROS formation through interaction of H-ferritin with G-CSF receptor.

A variety of hematopoietic factors including granulocyte macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), interleukin 3 (IL-3) and thrombopoietin (TPO) induce a rapid increase of intracellular reactive oxygen species (ROS). ROS induces the activation of many signaling molecules, including Shc, Lck, syk, PKC, MAPK, STAT3, through inhibition of protein phosphatase. Each growth factor has a specific cell-surface receptor, which activates both unique and shared signal transduction pathways. The processes of signal transduction linking cell-surface receptor to the formation of intracellular ROS have not been elucidated fully. Ferritins are composed of two subunit types, H and L, and made of 24 subunits that sequester up to 4500 atoms of iron. When the stored iron atoms are released from H-ferritin, through iron-catalyzed reaction, they have the capacity to promote the formation of ROS. Here, the interaction of G-CSFR and H-ferritin was confirmed by yeast two-hybrid screen, mammalian two-hybrid assays, glutathione-S-transferase (GST) pull-down experiments and immunoprecipitation studies in vitro and in vivo. Additional immunofluorescence assay showed that the two proteins colocalized along the plasma membrane and partly in the cytoplasm. The binding site for H-ferritin was demonstrated to locate to the box3 motif on the C-terminal region of granulocyte colony-stimulating factor receptor (G-CSFR). Furthermore, we found the interaction of full-length G-CSFR with H-ferritin was dissociated at 30 minutes after G-CSF induction and then began to assemble at 45 minutes. The labile iron pool (LIP) is a pool of redox-active iron complexes, which is regulated tightly by the expression of H-ferritin. Experiments showed that the level of LIP increased significantly at 30 minutes after G-CSF stimulation and intracellular ROS formation changed in a pattern similar to LIP response to G-CSF in bone-marrow hematopoietic cells. G-CSF-induced changes in the level of LIP and ROS formation could be blocked by pretreatment with iron chelators that repressed the expression of H-ferritin. In addition, the phosphorylation of STAT3 induced by G-CSF was decreased in iron chelator-treated hematopoietic cells. These data suggested that LIP may be released from the dissociated H-ferritin, and then induce intracellular ROS formation in the bone-marrow hematopoietic cells. ROS, acting as a second messenger, might take part in G-CSF receptor signal transduction. So, here, a new G-CSFR-H-ferritin-LIP-ROS pathway is proposed for regulation of intracellular ROS formation in bone-marrow hematopoietic cells.

Animals↗