Identification of a benzo imidazole thiazole derivative as the specific irreversible inhibitor of protein tyrosine phosphatase.

Protein tyrosine phosphatases (PTPs) play key roles in many physiological processes, including cell proliferation, differentiation, immune responses and neural activities. Inappropriate regulation of the PTP activity could lead to human diseases, such as cancer or diabetes. Functional studies of PTP can be greatly facilitated by chemical probes that covalently label the active site of a PTP through an activity-dependent chemical reaction. Here, we characterize compound E4 as a new class of PTP activity probes. Compound E4 inactivate STEP in a time- and concentration-dependent fashion. Further study showed that compound E4 inhibits a series of PTPs in a time dependent manner, whereas it shows little or no inhibition toward metal dependent protein phosphatases. Collectively, this new identified covalent inhibitor of PTPs has the potential to be developed to an active site Cys directed PTP probes to study the active properties of the PTPs in cell signaling.

'a'-Position-mutated and G4-mutated hemagglutinin-neuraminidase proteins of Newcastle disease virus impair fusion and hemagglutinin-neuraminidase-fusion interaction by different mechanisms.

OBJECTIVES: To determine the effects of heptad repeat regions (HRs) and N-linked carbohydrate sites of the Newcastle disease virus hemagglutinin-neuraminidase (HN) protein on fusion of HN and fusion (F) proteins and HN-F interaction. METHODS: We mutated six 'a' residues in the HRs and four asparagines in N-linked carbohydrate sites to alanine in the HN protein. A vaccinia-T7 RNA polymerase expression system was used to express HN cDNAs in BHK-21 cells to determine the HN functions. Deglycosylation was treated with PGNase F digestion. The formation of HN-F protein complexes was determined by the coimmunoprecipitation assay. RESULTS: Each HR-mutated protein interfered with fusion and the HN-F interaction. The G4-mutated protein not only impaired fusion and HN-F interaction but also decreased activities in cell fusion promotion, hemadsorption and neuraminidase. CONCLUSIONS: It is assumed that two different mechanisms for mutations in these two regions are responsible for the decreased fusion promotion activity and the reduced ability of interaction with F protein. Mutations in the HRs impair fusion and HN-F interaction by altering the transmission of a signal from the globular domain to the F-specific region in the stalk, but the G4 mutation modulates fusion and HN-F interaction by the misfolding of some important structures.

Preventive action of curcumin in experimental acute pancreatitis in mouse.

BACKGROUND & OBJECTIVES: Curcuma longa (turmeric) has a long history of use in Ayurvedic medicine as a treatment for inflammatory conditions. The purpose of the present study was to investigate the preventive effects of curcumin against acute pancreatitis (AP) induced by caerulein in mouse and to elucidate possible mechanism of curcumin action. METHODS: Curcumin (50 mg/kg/day) was intraperitoneally injected to Kun Ming male mice for 6 days, followed by injection of caerulein to induce AP. GW9662 (0.3 mg/kg), a specific peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, was intravenously injected along with curcumin. Murine macrophage RAW264.7 cells were treated with 100 µmol/l curcumin for 2 h, and then stimulated with 0.1 µ g/ml lipopolysaccharide (LPS). Serum amylase and transaminase levels were measured at 10 h after AP. TNF-α level in mouse serum and cell culture medium were detected by ELISA. Expression of PPARγ and NF-κB were analyzed by RT-PCR and Western blot. RESULTS: Curcumin significantly decreased the pancreas injury and reversed the elevation of serum amylase, ALT and AST activities and TNF-α level in mice with AP. Curcumin treatment inhibited the elevation of NF-κB-p65 in the nucleus of mouse pancreas AP group and RAW264.7 cells, but significantly increased the expression of PPARγ. GW9662 could abolish the effects of curcumin on serum levels of amylase, ALT, AST, TNF-α, and NF-κB level. INTERPRETATION & CONCLUSIONS: Our results suggest that curcumin could attenuate pancreas tissue and other organ injury by inhibiting the release of inflammatory cytokine TNF-α. These effects may involve upregulation of PPARγ and subsequent downregulation of NF-κB.

Association between KIR Genes and Efficacy of Treatment of HBeAg-Positive Chronic Hepatitis B Patients with Entecavir.

Entecavir (ETV) is commonly used to treat chronic hepatitis B (CHB) in China. However, certain percentages of e-Antigen (HBeAg) positive CHB patients do not respond to ETV therapy. OBJECTIVE: To investigate whether the killer immunoglobulin-like receptor (KIR) genes were associated with seroconversion in HBeAg positive CHB responder patients treated with ETV. METHODS: Polymerase chain reaction with sequence-specific primers (PCR-SSP) method was performed to genotype KIR genes in 200 healthy controls and 198 HBeAg-positive CHB patients which 59 were defined as the complete response group (CRG) to the treatment with ETV and 139 were defined as null or partial response group (NPRG). RESULTS: The frequencies of KIR2DS2 and KIR2DS3 were significantly higher (P=0.030, OR=1.57，95%CI=2.36-1.05 and P=0.018, OR=1.773，95%CI=2.77-1.13, respectively), while, the frequencies of KIR2DL3, KIR2DS1 and KIR3DS1 were significantly lower (P=0.038, OR=0.525, 95%CI=0.96-0.29,and P=0.031, OR=0.640, 95%CI =0.95-0.43, and P=0.035, OR=0.641, 95%CI=0.96-0.43, respectively) in HBeAg-positive CHB patients than those in healthy controls. The frequency of KIR2DS3 gene was significantly higher in NPRG than that in CRG (P=0.018, OR=0.402, 95%CI=0.83-0.20). The frequencies of KIR2DL3 and KIR3DS1 genes were significantly higher in CRG than those in NPRG (P=0.019, OR=3.625, 95%CI=10.83-1.21 and P=0.041, OR=1.949, 95%CI=3.65-1.04, respectively). CONCLUSION: Patients with KIR2DS3 might have negative responses to anti-HBV therapy with ETV and patients with KIR2DL3 and KIR3DS1 might have advantage in the therapy with ETV.

[Effects of 9-cis-retinoic acid on cell cycle and expression of cyclin D1 and cdk4 in lung cancer cells].

AIM: To study the effects of 9-cis-retinoic acid (9-cis-RA) on cell cycle and expression of cyclin D1 and cdk4 in lung cancer cells. METHODS: 9-cis-RA (1 x 10(-6) mol.L-1) was used to treat lung cancer cells for 24 h; Flow cytometry (FCM) was used to detect the percent of G0/G1 phase and S phase cells of three groups including blank control, DMSO control and 9-cis-RA groups; RT-PCR was used to analyze the expression changes of cyclin D1 and cdk4 before and after treatment with 9-cis-RA in lung cancer cells. RESULTS: The percent of G0/G1 phase cells of 9-cis-RA groups was significantly higher than that of the control groups (P < 0.01 or P < 0.05) and the percent of S phase cells of 9-cis-RA groups was lower than that of the control groups (P < 0.01 or P < 0.05); the expression of cyclin D1 of PG, SPC-A1 and L78 cells was decreased (P < 0.01) and the expression of cdk4 of PG, A549 and L78 cells was also decreased (P < 0.01) after treatment with 9-cis-RA. CONCLUSION: Most of the proliferation and the expression of cyclin D1 and cdk4 of PG, A549, SPC-A1 and L78 were inhibited by 9-cis-RA.

Role of N-linked glycosylation of the human parainfluenza virus type 3 hemagglutinin-neuraminidase protein.

Human parainfluenza virus type 3 (hPIV-3) is a major respiratory tract pathogen that affects infants and young children. The hPIV-3 hemagglutinin-neuraminidase (HN) protein is a multifunctional protein mediating hemadsorption (HAD), neuraminidase (NA), and fusion promotion activities, each of which affects the ability of HN to promote viral fusion and entry. The hPIV-3 HN protein contains four potential sites (N308, N351, N485 and N523) for N-linked glycosylation. Electrophoretic mobility analysis of mutated HN proteins indicated that N308, N351 and N523 sites, but not the N485 site in HN protein, were targeted for the addition of glycans in BHK-21 cells. These functional glycosylation sites were systematically eliminated in various combinations from HN to form a panel of mutants in which the roles of individual carbohydrate chains and groups of carbohydrate chains could be analyzed. Removal of individual or multiple N-glycans on the hPIV-3 HN protein had no effects on transport to the cell surface, expression and NA activity. Single glycosylation site mutants (G1, G2 and G4) not only impaired fusion promotion activity but also reduced HAD activity of HN protein, which was even more obvious for all three double mutants (G12, G14 and G24) and the triple mutant (G124). In addition, every mutant protein retained F-interactive capability that was equal to the wild-type protein capability. Interestingly, the F protein that could be co-immunoprecipitated with the G12 mutated protein or immunoprecipitated with anti-F antibody was not efficiently cleaved. For G14, G24 and G124, little cleaved F protein was detected in co-immuoprecipitation F protein assay and its total amounts where in the cell lysates. The mechanism underlying hPIV-3 HN and F protein remained associated before and after receptor engagement and the strength of the HN-receptor interaction modulated the activation of F the protein which could determine the extent of fusion. Finally, we demonstrated that single or multiple N-glycosylation site mutations inhibited fusion at the earliest stages. Taken together, these results indicated that N-glycosylation of hPIV-3 HN is critical to its receptor recognition activity, cleavage of the F protein, and fusion promotion activity, but had no influence on its interaction with the homologous F protein and NA activity.

[Study on functions of N-carbohydrate chains in human parainfluenza virus type 3 hemagglutinin-neuraminidase protein].

To determine the functions of N-carbohydrate chains in human parainfluenza virus type 3 hemagglutinin-neuraminidase(HN) protein, a PCR-based site-directed mutagenesis method was used to obtain N-glycan mutants. Protein electrophoresis rate, cell surface expression,receptor binding activity, neuraminidase activity and cell fusion promotion activity were determined. The HN proteins of single mutants (G1, G2, and G4) and multiple mutants (G12, G14, G24 and G124) migrated faster than the wild-type (wt) HN protein on polyacrylamide gels, while G3-mutated protein and wt HN protein migrated at the same position. There was no statistic difference in cell surface expression and neuraminidase activity between wt and each mutant HN protein (P>0.05), but receptor binding activity and cell fusion promotion activity of each mutant protein was reduced to significant extent (P<0.05). G1, G2 and G4 mutants exhibited re duced receptor binding activity, which was 83.94%, 76.45% and 55.32% of the wt level, respectively. G1, G2 and G4-mutated proteins also showed reductions in fusion promotion activity, which was 80.84%, 77.83% and 64.16%, respectively. Multiple mutants with G12-, G14-, G24- and G124- substitutions could further reduce receptor binding activities, 33.07%, 20.67%, 19.96% and 15.11% of the wt HN level, respectively. G12, G14, G24 and G124 mutants exhibited levels of fusion promotion activity that were only 46.360, 12.04%, 13.43% and 4.05% of the wt amount, respectively. As N-glycans of hPIV3 HN protein play an important role in receptor binding activity and cell fusion promotion activity of HN protein. We propose that the loss of N-glycans change the conformation or orientation of globular domain that is responsible for receptor binding and lower receptor binding activity and cell fusion promotion activi ty.

Human leukocyte antigen-C and killer cell immunoglobulin-like receptor gene polymorphisms among patients with syphilis in a Chinese Han population.

Syphilis is a sexually transmitted infection caused by the Treponema pallidum subspecies pallidum spirochete bacterium. The killer cell immunoglobulin-like receptors (KIR), interacting with human leukocyte antigens (HLA), regulate the activations of natural killer (NK) cells and certain T-cell subsets in response to microbe infection. The objective of this study was to explore whether KIR and HLA-C gene polymorphisms were associated with syphilis in a Chinese Han population. Polymerase chain reaction with sequence-specific primers (PCR-SSP) method was used to genotype KIR and HLA-C genes in 231 syphilis patients and 247 healthy controls. Framework genes KIR2DL4, KIR3DL2, KIR3DL3 and KIR3DP1 were present in all individuals. The frequencies of KIR2DS3 and KIR3DS1 were higher in syphilis patients than in healthy controls (p = 0.030 and p = 0.038, respectively), while the frequency of KIR2DS5 was higher in healthy controls than in syphilis patients (p = 0.015; OR = 0.575). The homozygote for HLA-C1 allele (HLA-C1C1) was more common in controls compared with syphilis patients (p = 0.030; OR = 0.667). The frequency of individuals with HLA-C1C1 and KIR2DL3 genotype was higher in control group relative to syphilis patient group (p = 0.018; OR = 0.647). These data indicated that KIR2DS3 and KIR3DS1 were more prevalent in syphilis patients than in controls, and that KIR2DS5, HLA-C1C1 and HLA-C1C1-KIR2DL3 were more prevalent in controls than in syphilis patients, respectively. These will require further investigation using functional studies.