Modulating protein kinase D1 signal transduction

Protein kinase C （PKC） consists of a family of serine/threonine kinases that are identified by the presence of two copies of the C1 domain, which form the diacylglycerol （DAG）-binding module. According to their enzymatic activities PKCs are sub-divided into conventional isozymes （PKCα, β and γ; calcium, phospholipid and DAG-activated kinases）, novel isozymes （PKCδ, ε, η, μ and θ; calcium-insensitive, phospholipid-dependent and DAG-dependent）, and atypical isozymes （PKCζ and λ; calcium-insensitive and DAG-insensitive enzymes）. Human protein kinase Cμ and its mouse homolog, protein kinase D1 （PKD1）, which has been under intense investigation in recent years, is a DAG-dependent, Ca^2＋-independent serine/threonine protein kinase as a novel PKC isoform. Recently PKDs were classified as a novel subgroup of the calcium/calmodulin-dependent protein kinase （CAMK） family, based on sequence similarities of the kinase domain; the catal~ctic domain of PKD1 has the highest homology to CAMK. PKD1 has three main pathways for activation. One is DAG-phospholipase C （PLC）-PKC-dependent activation of PKD1. In this model, PKD 1 not only acts as a direct DAG target but also lies downstream of PKCs to regulate biological processes in cells.     

A new blaLEN-17 gene in a clinical isolate of Staphylococcus epidermidis in Shanghai, China

The introduction of the antibiotics into clinical practice has significantly reduced the mortality of infectious diseases. Although chromosomally mediated β-1actamase is natural in many genera of bacteria, the intensive use of antibiotics is the main cause for the increasing emergence of new β-1actamases. So far, more than 340 β-lactamases have been identified,1 among which, more than 200 are extended-spectrum β-lactamases （ESBLs）.2 The most prevalent β-lactamases are class A enzymes, including SHV and TEM. Genes encoding these enzymes generally located in large transferable plasmids. The dissemination of these plasmids attributes to the increasing incidence and spread of v-lactam resistance. It is important to investigate the prevalence and allelic distribution of genes encoding β-lactamase in the bacterial population in order to prevent the emergence of ESBLs in those bacteria and the spread of ESBLs in the clinical setting.     

Effect of a conserved peptide derived from Kunitz domain of hepatitis B virus x protein on the cell cycle and apoptosis of HepG2 cells via the proteasome pathway

Background Hepatitis B virus （HBV） x protein （HBx） in HepG2 cells causes a moderate decrease in proteolysis activity of the proteasome. A highly conserved Kunitz-type serine protease inhibitor domain within 154 amino acid residues of HBx has been identified. In this study, a peptide chain derived from the Kunitz domain （PKD） was used to study its effect on the cell cycle and apoptosis of HepG2 cells, and investigated the function of PKD on the activities of proteasomes and AAA-ATPase p97, which involves in the ubiquitin-proteasome protein degradation pathway.
Methods The PKD peptide （Phe-Val-Leu-Gly-Gly-Cys-Arg-His-Lys） was chemically synthesized. MTT assays were used to determine the effects of PKD on HepG2 cell growth. Mouse anti-p97 antibody was developed for Western blotting to detect the expression of p97. ATPase activity of proteasomes was measured using a colorimetric assay. Peptidase activities of proteasomes were analyzed with various peptidase-specific fluorogenic peptide substrates. Flow cytometry was used to determinate cell cycle phase and apoptosis.
Results Viability of HepG2 cells decreased in a PKD-dose-dependent manner. Cells exhibited significant cytotoxicity in the presence of 15 mmol/L of PKD. Western blotting analysis showed that expression of p97 was suppressed in HepG2 cells treated with PKD compared to untreated cells. The ATPase activity of proteasomes from immunoprecipitates of HepG2 cells pretreated with PKD was apparently decreased. Chymotryptic activity of proteasomes in HepG2 cells was significantly inhibited by 10mmol/L PKD; tryptic activity and peptidylglutamyl peptide hydroiase activity of proteasomes were less inhibited by PKD than chymotryptic activity. The cell cycle phase of HepG2 cells treated with PKD for 36 hours was blocked largely at the G0-G1 phase, while untreated control cells were mainly in S phase. PKD also significantly induced apoptosis.
Conclusions The peptide derived from Kunitz domain of HBx protein induces HepG2 cell growth arrest and apoptosis, which may result from down-regulation of p97 expression, and decrease of both the ATPase and chymotryptic activities of proteasomes.     

T4SP: A Novel Tool and Database for Type Ⅳ Secretion Systems in Bacterial Genomes

Secretion systems, which can mediate the macromolecules to pass across cellular membranes, are essential for virulent and genetic material exchange among bacterial species [1] . Type IV secretion system (T4SS) is one of the secretion systems and it usually consists of 12 genes: VirB1, VirB2 …VirB11, and VirD4 [2] . The structure and molecular mechanisms of these genes have been well     

Cytotoxic genes from traditional Chinese medicine inhibit tumor growth both in vitro and in vivo

OBJECTIVE： Little effort has been made to study the protein-encoding genes isolated from traditional Chinese medicine（TCM） drugs, and the delivery of these genes into malignant cells through recombinant adeno-associated virus（r AAV） vectors has not been attempted. METHODS： We synthesized the c DNAs of five known cytotoxic proteins isolated from TCM drugs and the FLAG epitope-tagged c DNAs were subcloned into a r AAV plasmid vector. The protein expression was confi rmed by Western blot assay. Various cancer cell lines were transfected with the above plasmids and cell growth was monitored both in vitro and in vivo. The best cytotoxic gene was further packaged into r AAV vectors, under the control of a liver cancer-specifi c promoter. The liver tumor growth was then monitored following intratumor administration of the r AAV vectors.RESULTS： The expression plasmids, encoding individual potential cytotoxic genes tagged with FLAG epitope, were successfully generated and sequenced. Among these genes, trichosanthin（TCS） gene yielded the most promising results for the inhibition of cancer cell growth in vitro. The over-expressed TCS functioned as a type I ribosome-inactivating protein, followed by inducing apoptosis that is associated with the Bcl-PARP signaling pathway. Furthermore, intratumor injection of r AAV vectors containing the TCS gene signifi cantly inhibited the growth of human hepatocellular carcinoma tumors in a murine xenograft model.CONCLUSION： Our studies suggest that the use of TCM cytotoxic genes is a useful therapeutic strategy for treating human cancers in general, and liver tumors in particular.     

DIFFERENTIAL RENAL GENE EXPRESSION IN EXPERIMENTAL DIABETIC RATS AFTER ASTRAGALUS MEMBRANACEUS TREATMENT

Objective To find the genes involved in pathogenesis of diabetic nephropathy using gene chip technology. Methods We established a type I diabetic rat model by streptozotocin injection and divided these diabetic rats into two groups： diabetic rats group（ D group） and diabetic rats group treated with Astragalus Membranaceus （ DA group）. The renal tissue was collected and total RNA was extracted for gene chips. With the help of gene chip, we tried to discover the differential-displayed genes between these two groups. Results Totally 201 differential-displayed genes were found between the two groups, among which 126 genes were up-regulated and 75 genes were down-regulated in the rat renal tissue. Conclusion With gene chip results, we find several genes which are associated with diabetes in the rat renal tissue. The further research on the function of these genes will be helpful to understand the mechanism of diabetic nephropathy.