Biomedical subjects

Jianping Sun

Publications and source records attributed to Jianping Sun.

11 recordsLinked to original sources

PubMed2007

Genotype and phenotype patterns of drug-resistant HIV-1 subtype B' (Thai B) isolated from patients failing antiretroviral therapy in China.

Many AIDS patients in China who received free-of-charge antiretroviral therapeutics, including nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs), showed significant life improvement. Increasing numbers of patients, however, are experiencing antiretroviral therapy failure due to the emergence of drug-resistant viruses. The aim of this study was to investigate the genotypic and phenotypic drug resistance patterns of HIV-1 subtype B' variants, which are prevalent in China, in order to rationally design more efficient anti-HIV-1 regimens for future treatment of AIDS patients. 13 out of 16 patients (81%) who were treated with two NRTIs (ddI, and d4T or AZT) and one NNRTI (NVP) exhibited high resistance to NVP, 8 of them with a >1,000 IC50 fold increase. Five codons (101, 103, 108, 181, and 190) were involved in the NVP-resistant mutations, and K103N and Y181C mutations were predominant in these isolates. Fifteen isolates were resistant to at least one of the NRTIs, with high resistance to AZT (>10 IC50 fold increase) and intermediate resistance to d4T or ddI (approximately 4 IC50 fold increase). More than 10 codons were involved in the NRTI-resistant mutation and located in two regions (M41-V75 and T215-K219) of the reverse transcriptase. Concordance between the genotype and phenotype patterns for both NRTIs and NNRTI were detected in a majority of the isolates, suggesting that phenotypic resistance is predictable from genotyping assays, which are faster and less expensive than phenotypic assay. Because NVP and AZT can induce high resistances in these patients, these two drugs should be replaced with others more effective NNRTIs and NRTIs.

Anti-HIV Agents↗

PubMed2006

Solution structure of the second SH3 domain of human CMS and a newly identified binding site at the C-terminus of c-Cbl.

CMS, cas ligand with multiple Src homology 3 (SH3) domains, belongs to a family of ubiquitously expressed adaptor proteins. Among the CMS binding proteins, c-Cbl has been mostly extensively studied. It was reported that the motif PKPFPR (residues 824-829) of c-Cbl can bind to the N-terminus SH3 domains of CMS. Here we report the solution structure of the second SH3 domain of CMS (CMS_SH3_B), furthermore, we have identified that a peptide from residues 701 to 714 of c-Cbl (Cbl-p), i.e. MTPSSRPLRPLDTS, can specially bind to CMS_SH3_B using NMR chemical shift perturbation, suggesting that the peptide is a new potential CMS binding site. Among the peptide, TPSSRPLR is the core binding motif and Arg709 plays a key role in the interaction. Cbl-p binding interface on CMS_SH3_B along a hydrophobic channel is composed of RT loop, n-Src loop and beta4 strand and divided into three pockets. This work indicates the solution structure of CMS_SH3_B bears the canonical beta-beta-beta-beta-alpha-beta fold and a new binding site in c-Cbl involved in its interaction with CMS, which probably contributes to the clustering of CMS. All the information provided here should be beneficial for the future functional study of CMS.

Adaptor Proteins, Signal Transducing↗

PubMed2006

BMP4 activation and secretion are negatively regulated by an intracellular gremlin-BMP4 interaction.

Bone morphogenetic protein 4 (BMP4) is a potent growth factor that is involved in many important biological processes. Regulation of the level of secreted mature BMP4 determines the biological effects of BMP4 on cells in the local microenvironment. Previous studies suggested that Gremlin, a member of DAN family proteins, antagonizes BMP4 activity by sequestering extracellular BMP4. Herein, we report a novel intracellular regulatory mechanism by which Gremlin interacts with BMP4 precursor, prevents secretion of mature BMP4, and therefore inhibits BMP4 activity more efficiently. Furthermore, we also defined a 30-amino acid peptide sequence within the Gremlin DAN domain that is essential for BMP4 interaction. This novel Gremlin-mediated BMP4 posttranslational regulatory mechanism implies that the level of BMP4 mRNA expression does not truly reflect BMP4 activity when Gremlin and BMP4 are coexpressed within the same cell. Similar regulatory mechanisms may be utilized by other DAN family proteins.

Amino Acid Sequence↗

PubMed2006

Expression, purification, crystallization and preliminary X-ray characterization of the GRP carbohydrate-recognition domain from Homo sapiens.

Galectins are a family of animal lectins which share similar carbohydrate-recognition domains (CRDs) and an affinity for beta-galactosides. A novel human galectin-related protein named GRP (galectin-related protein; previously known as HSPC159) comprises only one conserved CRD with 38 additional N-terminal residues. The C-terminal fragment of human GRP (GRP-C; residues 38-172) containing the CRD has been expressed and purified. The protein was crystallized using the hanging-drop vapour-diffusion method from a solution containing 2% PEG 400 and 2M ammonium sulfate in 100 mM Tris-HCl buffer pH 7.5. Diffraction data were collected to a resolution limit of 2.0 angstroms at beamline 3W1A of Beijing Synchrotron Radiation Facility at 100 K. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 123.07, b = 96.67, c = 61.56 angstroms, beta = 118.72 degrees. The estimated Matthews coefficient was 2.6 angstroms3 Da(-1), corresponding to 51.8% solvent content.

Cloning, Molecular↗

PubMed2006

Solution structure of human peptidyl prolyl isomerase-like protein 1 and insights into its interaction with SKIP.

The human PPIL1 (peptidyl prolyl isomerase-like protein 1) is a specific component of human 35 S U5 small nuclear ribonucleoprotein particle and 45 S activated spliceosome. It is recruited by SKIP, another essential component of 45 S activated spliceosome, into spliceosome just before the catalytic step 1. It stably associates with SKIP, which also exists in 35 S and activated spliceosome as a nuclear matrix protein. We report here the solution structure of PPIL1 determined by NMR spectroscopy. The structure of PPIL1 resembles other members of the cyclophilin family and exhibits PPIase activity. To investigate its interaction with SKIP in vitro, we identified the SKIP contact region by GST pulldown experiments and surface plasmon resonance. We provide direct evidence of PPIL1 stably associated with SKIP. The dissociation constant is 1.25 x 10(-7) M for the N-terminal peptide of SKIP-(59-129) with PPIL1. We also used chemical shift perturbation experiments to show the possible SKIP binding interface on PPIL1. These results illustrated that a novel cyclophilin-protein contact mode exists in the PPIL1-SKIP complex during activation of the spliceosome. The biological implication of this binding with spliceosome rearrangement during activation is discussed.

Amino Acid Sequence↗

PubMed2005

Solution structure of Kti11p from Saccharomyces cerevisiae reveals a novel zinc-binding module.

Kti11p is a small, highly conserved CSL zinc finger-containing protein found in many eukaryotes. It was first identified as one of the factors required for maintaining the sensitivity of Saccharomyces cerevisiae to Kluyveromyces lactis zymocin. Then, it was found to be identical to Dph3, a protein required for diphthamide biosynthesis on eEF-2, the target of diphtheria toxin and Pseudomonas exotoxin A, in both yeast and higher eukaryotes. Furthermore, Kti11p/Dph3 was found to physically interact with core-Elongator, ribosomal proteins, eEF-2, two other proteins required for diphthamide modification on eEF-2, and DelGEF. Here, we determined the solution structure of Kti11p using NMR, providing the first structure of the CSL-class zinc-binding protein family. We present the first experimental evidence that Kti11p can bind a single Zn(2+) ion by its four conserved cysteine residues. The major structure of Kti11p comprises a beta sandwich as well as an alpha helix. Moreover, a structure-based similarity search suggests that it represents a novel structure and may define a new family of the zinc ribbon fold group. Therefore, our work provides a molecular basis for further understanding the multiple functions of Kti11p/Dph3 in different biological processes.

Amino Acid Sequence↗

PubMed2005

Smad1 expression and function during mouse embryonic lung branching morphogenesis.

Bone morphogenetic protein (BMP) 4 plays very important roles in regulating developmental processes of many organs, including lung. Smad1 is one of the BMP receptor downstream signaling proteins that transduce BMP4 ligand signaling from cell surface to nucleus. The dynamic expression patterns of Smad1 in embryonic mouse lungs were examined using immunohistochemistry. Smad1 protein was predominantly detected in peripheral airway epithelial cells of early embryonic lung tissue [embryonic day 12.5 (E12.5)], whereas Smad1 protein expression in mesenchymal cells increased during mid-late gestation. Many Smad1-positive mesenchymal cells were localized adjacent to large airway epithelial cells and endothelial cells of blood vessels, which colocalized with a molecular marker of smooth muscle cells (alpha-smooth muscle actin). The biological function of Smad1 in early lung branching morphogenesis was then studied in our established E11.5 lung explant culture model. Reduction of endogenous Smad1 expression was achieved by adding a Smad1-specific antisense DNA oligonucleotide, causing approximately 20% reduction of lung epithelial branching. Furthermore, airway epithelial cell proliferation and differentiation were also inhibited when endogenous Smad1 expression was knocked down. Therefore, these data indicate that Smad1, acting as an intracellular BMP signaling pathway component, positively regulates early mouse embryonic lung branching morphogenesis.

Animals↗

PubMed2004

Abnormal mouse lung alveolarization caused by Smad3 deficiency is a developmental antecedent of centrilobular emphysema.

Transforming growth factor-beta (TGF-beta) signaling plays an important regulatory role during lung development and remodeling. Smad3 is a major downstream signal transducer in the TGF-beta pathway from the cell membrane to the nucleus. In Smad3 null mutant mice, we have observed retarded lung alveolarization from postnatal day 7 to day 28, and subsequently centrilobular emphysema starting from day 28, as determined by morphometric analysis. In addition to the morphological changes, peripheral lung cell proliferation in Smad3 knockout mice was reduced compared with the wild-type control between postnatal days 7 and 28. Expression of tropoelastin at the mRNA level was also dramatically decreased in Smad3 knockout lungs from postnatal day 28 through adulthood. Furthermore, increased matrix metalloproteinase-9 protein expression and activity were detected in the Smad3 knockout mouse lung tissue and the bronchoalveolar lavage fluid at postnatal day 28 when the centrilobular emphysema pathology was just beginning to appear. Therefore, these results indicate that Smad3 not only has a positive regulatory impact on neonatal lung alveolarization but also potentially plays a protective role against the occurrence of centrilobular emphysema later on in life.

Animals↗

PubMed2004

Insulin receptor, insulin receptor substrate-1, Raf-1, and Mek-1 during hormonal hepatocarcinogenesis by intrahepatic pancreatic islet transplantation in diabetic rats.

Low-number transplantation of pancreatic islets into the livers of diabetic rats leads to transformation of the downstream liver acini into clear-cell foci of altered hepatocytes (FAHs). These FAHs correspond to the glycogen-storing (clear-cell) phenotype of hepatocellular preneoplasias and develop into hepatocellular adenomas (HCAs) and hepatocellular carcinomas (HCCs) within 6 to 24 months. In addition, they show metabolic alterations that resemble well-known insulin effects, most likely constituting the result of the local hyperinsulinemia. Thus, we investigated FAHs, HCAs, and HCCs for altered expression of insulin receptor, insulin receptor substrate-1 (IRS-1), Raf-1 and Mek-1. Light and electron microscopic immunohistochemistry revealed a translocation of insulin receptor from the plasma membrane (normal tissue) into the cytoplasm in clear-cell FAHs and an increase in insulin receptor expression in HCAs and HCCs. FAHs also showed an increase in IRS-1 gene expression, investigated by in situ hybridization and quantitative reverse transcription-PCR. IRS-1, Raf-1, and Mek-1 proteins were strongly overexpressed in FAHs and tumors, as compared with the unaltered liver tissue. These overexpressions were closely linked to the clear-cell phenotype of preneoplastic and neoplastic hepatocytes, because basophilic FAHs (later stages) and basophilic tumors showed no overexpressions. In this endocrine model of hepatocarcinogenesis, severe alterations of insulin signaling were induced by the pathological local action of islet hormones in the livers and may substantially contribute to the carcinogenic process.

Animals↗

PubMed2004

Overexpression of Smurf1 negatively regulates mouse embryonic lung branching morphogenesis by specifically reducing Smad1 and Smad5 proteins.

Early embryonic lung branching morphogenesis is regulated by many growth factor-mediated pathways. Bone morphogenetic protein 4 (BMP4) is one of the morphogens that stimulate epithelial branching in mouse embryonic lung explant culture. To further understand the molecular mechanisms of BMP4-regulated lung development, we studied the biological role of Smad-ubiquitin regulatory factor 1 (Smurf1), an ubiquitin ligase specific for BMP receptor-regulated Smads, during mouse lung development. The temporo-spatial expression pattern of Smurf1 in mouse embryonic lung was first determined by quantitative real-time PCR and immunohistochemistry. Overexpression of Smurf1 in airway epithelial cells by intratracheal introduction of recombinant adenoviral vector dramatically inhibited embryonic day (E) 11.5 lung explant growth in vitro. This inhibition of lung epithelial branching was restored by coexpression of Smad1 or by addition of soluble BMP4 ligand into the culture medium. Studies at the cellular level show that overexpression of Smurf1 reduced epithelial cell proliferation and differentiation, as documented by reduced PCNA-positive cell index and by reduced mRNA levels for surfactant protein C and Clara cell protein 10 expression. Further studies found that overexpression of Smurf1 reduced BMP-specific Smad1 and Smad5, but not Smad8, protein levels. Thus overexpression of Smurf1 specifically promotes Smad1 and Smad5 ubiquitination and degradation in embryonic lung epithelium, thereby modulating the effects of BMP4 on embryonic lung growth.

Animals↗

PubMed2003

TACE is required for fetal murine cardiac development and modeling.

Tumor necrosis factor-alpha converting enzyme (TACE) is a membrane-anchored, Zn-dependent metalloprotease, which belongs to the ADAM (a disintegrin and metalloprotease) family. TACE functions as a membrane sheddase to release the ectodomain portions of many transmembrane proteins, including the precursors of TNFalpha, TGFalpha, several other cytokines, as well as the receptors for TNFalpha, and neuregulin (ErbB4). Mice with TACE(DeltaZn/DeltaZn) null mutation die at birth with phenotypic changes, including failure of eyelid fusion, hair and skin defects, and abnormalities of lung development. Abnormal fetal heart development was not previously described. Herein, we report that TACE(DeltaZn/DeltaZn) null mutant mice by late gestation exhibit markedly enlarged fetal hearts with increased myocardial trabeculation and reduced cell compaction, mimicking the pathological changes of noncompaction of ventricular myocardium. In addition, larger cardiomyocyte cell size and increased cell proliferation were observed in ventricles of TACE(DeltaZn/DeltaZn) knockout mouse hearts. At the molecular level, reduced expression of epidermal growth factor receptor, attenuated protein cleavage of ErbB4, and changes in MAPK activation were also detected in TACE(DeltaZn/DeltaZn) knockout heart tissues. The data suggest that TACE-mediated cell surface protein ectodomain shedding plays an essential and a novel regulatory role during cardiac development and modeling.

ADAM Proteins↗