Zinc folds the N-terminal domain of HIV-1 integrase, promotes multimerization, and enhances catalytic activity

The N-terminal domain of HIV-1 integrase contains a pair of His and Cys residues (the HHCC motif) that are conserved among retroviral integrases. Although His and Cys residues are often involved in binding zinc, the HHCC motif does not correspond to any recognized class of zinc binding domain. We have investigated the binding of zinc to HIV-1 integrase protein and find that it binds zinc with a stoichiometry of one zinc per integrase monomer. Analysis of zinc binding to deletion derivatives of integrase locates the binding site to the N-terminal domain. Integrase with a mutation in the HHCC motif does not bind zinc, consistent with coordination of zinc by these residues. The isolated N-terminal domain is disordered in the absence of zinc but, in the presence of zinc, it adopts a secondary structure with a high alpha helical content. Integrase bound by zinc tetramerizes more readily than the apoenzyme and is also more active than the apoenzyme in in vitro integration assays. We conclude that binding of zinc to the HHCC motif stabilizes the folded state of the N-terminal domain of integrase and bound zinc is required for optimal enzymatic activity.

Genome-wide association study in Han Chinese identifies four new susceptibility loci for coronary artery disease

We performed a meta-analysis of 2 genome-wide association studies of coronary artery disease comprising 1,515 cases and 5,019 controls followed by replication studies in 15,460 cases and 11,472 controls, all of Chinese Han ancestry. We identify four new loci for coronary artery disease that reached the threshold of genome-wide significance (P < 5 × 10(-8)). These loci mapped in or near TTC32-WDR35, GUCY1A3, C6orf10-BTNL2 and ATP2B1. We also replicated four loci previously identified in European populations (in or near PHACTR1, TCF21, CDKN2A-CDKN2B and C12orf51). These findings provide new insights into pathways contributing to the susceptibility for coronary artery disease in the Chinese Han population.

Solution structure of the N-terminal zinc binding domain of HIV-1 integrase

The solution structure of the N-terminal zinc binding domain (residues 1-55; IN1-55) of HIV-1 integrase has been solved by NMR spectroscopy. IN1-55 is dimeric, and each monomer comprises four helices with the zinc tetrahedrally coordinated to His 12, His 16, Cys 40 and Cys 43. IN1-55 exists in two interconverting conformational states that differ with regard to the coordination of the two histidine side chains to zinc. The different histidine arrangements are associated with large conformational differences in the polypeptide backbone (residues 9-18) around the coordinating histidines. The dimer interface is predominantly hydrophobic and is formed by the packing of the N-terminal end of helix 1, and helices 3 and 4. The monomer fold is remarkably similar to that of a number of helical DNA binding proteins containing a helix-turn-helix (HTH) motif with helices 2 and 3 of IN1-55 corresponding to the HTH motif. In contrast to the DNA binding proteins where the second helix of the HTH motif is employed for DNA recognition, IN1-55 uses this helix for dimerization.

Infectivity, transmission, and pathology of human-isolated H7N9 influenza virus in ferrets and pigs

The emergence of the H7N9 influenza virus in humans in Eastern China has raised concerns that a new influenza pandemic could occur. Here, we used a ferret model to evaluate the infectivity and transmissibility of A/Shanghai/2/2013 (SH2), a human H7N9 virus isolate. This virus replicated in the upper and lower respiratory tracts of the ferrets and was shed at high titers for 6 to 7 days, with ferrets showing relatively mild clinical signs. SH2 was efficiently transmitted between ferrets via direct contact, but less efficiently by airborne exposure. Pigs were productively infected by SH2 and shed virus for 6 days but were unable to transmit the virus to naïve pigs or ferrets. Under appropriate conditions, human-to-human transmission of the H7N9 virus may be possible.

Polymorphisms of DNA repair gene XRCC1 in squamous cell carcinoma of the head and neck

Because reduced DNA repair capacity (phenotype) has been suggested as a risk factor for squamous cell carcinoma of the head and neck (SCCHN), newly-identified DNA repair gene polymorphisms (genotype) may also be implicated in risk. To test this hypothesis, we conducted a case-control study of 203 SCCHN patients and 424 control subjects (matched for age, sex and ethnicity) to investigate the role of two XRCC1 polymorphisms (XRCC1 26304 T and XRCC1 28152 A, respectively) in SCCHN. Multivariate logistic regression analysis was performed to calculate the adjusted odds ratio (OR) and 95% confidence interval (CI). A total of 180 cases (88.7%) and 363 controls (85.6%) lacked the XRCC1 26304 T allele [adjusted OR = 1.34 (CI, 0.80-2.25)]. Lack of this polymorphism was a significant risk factor specifically for cancers of the oral cavity and pharynx [adjusted OR = 2.46 (CI, 1.22-4.97)]. Thirty-two cases (15.8%) and 46 controls (10.8%) were homozygous for the XRCC1 28152 A allele [adjusted OR = 1.59 (CI, 0.97-2.61) for all cases, and 1.41 (CI, 0. 80-2.48) for oral and pharyngeal cancer only]. Furthermore, when the two genotypes were combined into a three-level model of risk, a polymorphism-polymorphism interaction of increasing risk (trend test, P = 0.049) was evident: OR = 1.0 for those with neither risk genotype (referent group), adjusted OR = 1.51 (CI, 0.87-2.61) for those with either risk genotype, and 2.02 (CI, 1.00-4.05) for those with both risk genotypes. For oral and pharyngeal cancer, this trend was even more pronounced with the adjusted OR = 2.68 (CI, 1.28-5.61) for those with either risk genotype, and 3.22 (CI, 1.33-7.81) for those with both risk genotypes. The findings support the hypothesis that a polymorphic XRCC1 DNA repair gene contributes to risk of developing SCCHN.

Barrier-to-autointegration factor (BAF) bridges DNA in a discrete, higher-order nucleoprotein complex

Barrier-to-autointegration factor (BAF) is a highly conserved cellular protein that was identified by its activity in protecting retroviral DNA against autointegration. We show that BAF has the property of bridging double-stranded DNA in a highly ordered nucleoprotein complex. Whereas BAF protein alone is a dimer in solution, upon binding DNA, BAF forms a dodecamer with DNA bound at multiple discrete sites in the complex. The interactions between BAF and DNA are entirely nonspecific with respect to DNA sequence. The dual interaction of BAF with DNA and LAP2, a protein associated with the nuclear lamina, suggests a role for LAP2 in chromosome organization. Consistent with this idea, RNA interference experiments with Caenorhabditis elegans reveal a defect in mitosis.

XPD/ERCC2 polymorphisms and risk of head and neck cancer: a case-control analysis

DNA repair capacity is central in maintaining normal cellular functions. Variants of several DNA repair genes,including the nucleotide excision repair gene XPD, have been described recently. Because we previously reported that patients with squamous cell carcinoma of the head and neck (SCCHN) had lower DNA repair capacity than healthy controls, we hypothesized that inherited polymorphisms of XPD may contribute to genetic susceptibility to SCCHN, a tobacco-related cancer. To test this hypothesis, we conducted a hospital-based case-control study of 189 SCCHN patients and 496 cancer-free controls who were frequency-matched on age, gender and smoking status. All subjects were non-Hispanic whites. Two XPD polymorphisms (C22541A and A35931C) were typed using the restriction enzymes TfiI and PstI, respectively. Multivariate logistic regression analysis was performed to calculate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). In the controls, the frequencies of the variant 22541A and 35931C alleles were 44.7% and 33.8%, respectively. The frequency of the 22541A homozygous genotype (22541AA) was lower in cases (15.9%) than in controls (20.4%) but was not associated with risk (adjusted OR = 0.90; 95% CI = 0.52-1. 56) for SCCHN. The frequency of the 35931C homozygous genotype (35931CC) was higher in cases (16.4%) than in controls (11.5%) and associated with a borderline increased risk (adjusted OR = 1.55; 95% CI = 0.96-2.52) for SCCHN. The risk was higher in older subjects (OR = 2.22; 95% CI = 1.03-4.80), current smokers (OR = 1.83; 95% CI = 0.79-4.27) and current drinkers (OR = 2.59; 95% CI = 1.25-5.34) in the stratification analysis. These results suggest a gene-environment interaction, but this did not reach statistical significance. The findings are limited due to the relatively small numbers in the subgroups and need to be verified by further investigations.

Evidence for a superantigen mediated process in Kawasaki disease

The clinical, pathological, and immunological similarities between Kawasaki disease and the staphylococcal and streptococcal toxic shock syndromes suggest that a superantigen toxin may be involved in the pathogenesis of the disease. The V beta repertoire of peripheral blood mononuclear cells from 21 children with Kawasaki disease, 28 children with other illnesses, and 22 healthy controls were examined using monoclonal antibodies to V beta 2, 5, 8, 12, and 19. The mean percentage of V beta 2 expressing T cells in the patients with Kawasaki disease was increased when compared with healthy controls or children with other illnesses. The mean percentages of V beta 5, 8, 12, and 19 expressing T cells were also increased in the patients with Kawasaki disease compared with healthy controls, but were not increased when compared with children with other illnesses. The selective use of V beta 2 supports the hypothesis that a superantigen is involved in the pathogenesis of Kawasaki disease.

Cancer deaths and cases attributable to lifestyle factors and infections in China, 2013

Background

The burden of cancer in China is high, and it is expected to further increase. Information on cancers attributable to potentially modifiable risk factors is essential in planning preventive measures against cancer. We estimated the number and proportion of cancer deaths and cases attributable to ever-smoking, second-hand smoking, alcohol drinking, low fruit/vegetable intake, excess body weight, physical inactivity, and infections in China, using contemporary data from nationally representative surveys and cancer registries.

Methods

The number of cancer deaths and cases in 2013 were obtained from the National Central Cancer Registry of China and data on most exposures were obtained from the China National Nutrition and Health Survey 2002 or 2006 and Global Adult Tobacco Smoking 2010. We used a bootstrap simulation method to calculate the number and proportion of cancer deaths and cases attributable to risk factors and their corresponding 95% confidence intervals (CIs), allowing for uncertainty in data.

Results

Approximately 718 000 (95% CI 702 100-732 200) cancer deaths in men and 283 100 (278 800-288 800) cancer deaths in women were attributable to the studied risk factors, accounting for 52% of all cancer deaths in men and 35% in women. The numbers for incident cancer cases were 952 500 (95% CI 934 200-971 400) in men and 442 700 (437 200-447 900) in women, accounting for 47% of all incident cases in men and 28% in women. The greatest proportions of cancer deaths attributable to risk factors were for smoking (26%), HBV infection (12%), and low fruit/vegetable intake (7%) in men and HBV infection (7%), low fruit/vegetable intake (6%), and second-hand smoking (5%) in women.

Conclusions

Effective public health interventions to eliminate or reduce exposure from these risk factors, notably tobacco control and vaccinations against carcinogenic infections, can have considerable impact on reducing the cancer burden in China.

The relationship between consumption of antimicrobial agents and the prevalence of primary Helicobacter pylori resistance

BACKGROUND

Primary and acquired resistance to the antimicrobial agents is a primary reason for the failure of Helicobacter pylori eradication therapies. We assessed the primary antibiotic resistance rates of H. pylori to three different antibiotics and its relationship due to the annual antibiotic consumption in Japan during the period prior to approval of anti-H. pylori therapy in Japan.

MATERIALS AND METHODS

Antibiotic susceptibility was tested using the agar dilution method for clarithromycin, amoxicillin and metronidazole. Isolates were considered resistant when the MIC value was > 8 mg/l for metronidazole, > 1 mg/l for clarithromycin and < 0.5 mg/l for amoxicillin.

RESULTS

Helicobacter pylori isolates were obtained from 593 Japanese patients from 1995 to 2000. Primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin was found in 11%, 9% and 0.3% strains, respectively. The proportion with clarithromycin resistance significantly increased from 7% in 1997-98 to 15.2% in 1999-2000 (p =.003). During the same period the metronidazole resistance rate also increased from 6.6% in 1997-98 to 12% in 1999-2000 (p =.02). The prevalence of clarithromycin and metronidazole was related to the annual consumption of these antimicrobial agents.

CONCLUSION

Resistance rates for both clarithromycin and metronidazole appear to reflect the annual consumption of these agents. The high rate of clarithromycin resistance in Japan suggests that the effectiveness of clarithromycin-based therapies may be compromised in the near future.

Mechanisms of isoniazid resistance in Mycobacterium tuberculosis: enzymatic characterization of enoyl reductase mutants identified in isoniazid-resistant clinical isolates

Mutants in the structural gene of the inhA-encoded NADH-dependent 2-trans enoyl-acyl carrier protein reductase were identified from isoniazid-resistant clinical isolates of Mycobacterium tuberculosis. Recombinant InhA proteins with defined single amino acid replacements were expressed in Escherichia coli and purified to homogeneity. Steady-state kinetic parameters for wild type (WT) and I16T, I21V, I47T, and I95P mutants of the enoyl reductase were measured spectrophotometrically. NADH binding to WT and I16T, I21V, I47T, S94A, and I95P mutant reductases were determined by fluorescence spectroscopy and demonstrated that all mutant enzymes had reduced NADH affinity and that NADH binding to all mutants was cooperative as compared with the hyperbolic binding of NADH to the WT enzyme. Since KatG-produced electrophilic derivatives of isoniazid have been suggested to inactivate the enoyl reductase-NADH complex, the kinetics of inactivation for the WT and I21V and I95P mutants was determined. Both mutations resulted in significantly increased values for the apparent first-order rate constant of inactivation.

Solution structure of the cellular factor BAF responsible for protecting retroviral DNA from autointegration

The solution structure of the human barrier-to-autointegration factor, BAF, a 21,000 Mr dimer, has been solved by NMR, including extensive use of dipolar couplings which provide a priori long range structural information. BAF is a highly evolutionarily conserved DNA binding protein that is responsible for inhibiting autointegration of retroviral DNA, thereby promoting integration of retroviral DNA into the host chromosome. BAF is largely helical, and each subunit is composed of five helices. The dimer is elongated in shape and the dimer interface comprises principally hydrophobic contacts supplemented by a single salt bridge. Despite the absence of any sequence similarity to any other known protein family, the topology of helices 3-5 is similar to that of a number of DNA binding proteins, with helices 4 and 5 constituting a helix-turn-helix motif. A model for the interaction of BAF with DNA that is consistent with structural and mutagenesis data is proposed.

Interleukin-2 expression by a subpopulation of primary T cells is linked to enhanced memory/effector function

Single cell studies have identified intraclonal heterogeneity of cytokine production by activated T cells. To investigate implications of cytokine heterogeneity for cell fate, an interleukin (IL)-2 promoter-green fluorescent protein (GFP) reporter transgenic model was developed to track IL-2+ and IL-2- T cells during differentiation from naive precursors. Antigen-activated IL-2+ and IL-2- cells had comparable proliferative capacities in primary responses. However, T cells that expressed IL-2 in primary responses demonstrated enhanced antigenic sensitivity and increased expression of effector cytokines in secondary responses in vitro and in vivo. Thus, heterogeneity of activation during a primary response translates into heterogeneous secondary responses, in which enhanced memory/effector function is linked to cells that previously exceeded an activation threshold associated with IL-2 gene transcription.

Steady-state and pre-steady-state kinetic analysis of Mycobacterium tuberculosis pantothenate synthetase

Pantothenate synthetase (EC 6.3.2.1), encoded by the panC gene, catalyzes the essential ATP-dependent condensation of D-pantoate and beta-alanine to form pantothenate in bacteria, yeast and plants. Pantothenate synthetase from Mycobacterium tuberculosis was expressed in E. coli, purified to homogeneity, and found to be a homodimer with a subunit molecular mass of 33 kDa. Initial velocity, product, and dead-end inhibition studies showed the kinetic mechanism of pantothenate synthetase to be Bi Uni Uni Bi Ping Pong, with ATP binding followed by D-pantoate binding, release of PP(i), binding of beta-alanine, followed by the release of pantothenate and AMP. Michaelis constants were 0.13, 0.8, and 2.6 mM for D-pantoate, beta-alanine, and ATP, respectively, and the turnover number, k(cat), was 3.4 s(-1). The formation of pantoyl adenylate, suggested as a key intermediate by the kinetic mechanism, was confirmed by (31)P NMR spectroscopy of [(18)O]AMP produced from (18)O transfer using [carboxyl-(18)O]pantoate. Single-turnover reactions for the formation of pyrophosphate and pantothenate were determined using rapid quench techniques, and indicated that the two half-reactions occurred with maximum rates of 1.3 +/- 0.3 and 2.6 +/- 0.3 s(-)(1), respectively, consistent with pantoyl adenylate being a kinetically competent intermediate in the pantothenate synthetase reaction. These data also suggest that both half-reactions are partially rate-limiting. Reverse isotope exchange of [(14)C]-beta-alanine into pantothenate in the presence of AMP was observed, indicating the reversible formation of the pantoyl adenylate intermediate from products.

Scavenging effects of phenylpropanoid glycosides from Pedicularis on superoxide anion and hydroxyl radical by the spin trapping method(95)02255-4

The scavenging activities of six phenylpropanoid glycosides, i.e. leucosceptoside A and martynoside, isolated from Pedicularis alashanica Maxim, verbascoside, and pediculariosides A, M and N isolated from Pedicularis striata Pall ssp. arachnoidea Franch Tsoong, on superoxide anion and hydroxyl radicals have been studied by the spin trapping method. The results demonstrated that the number of phenolic hydroxyl groups in the structures of the phenylpropanoid glycosides is related to their scavenging activities. The scavenging effects of the phenylpropanoid glycosides possessing two o-dihydroxyl groups were stronger than the effects of the compounds possessing two o-hydroxy-methoxy groups.

Influence of radiation on the blood-brain barrier and optimum time of chemotherapy

A pilot study of the destructive effects of radiation on the blood-brain barrier (BBB) was made on 14 patients with localized and limited brain tumors by 99MTc-GH imaging from August 1988 to November 1989. Count/pixel data were obtained from the unirradiated, irradiated, and tumor areas before and after radiotherapy of 30-40 Gy. It was observed that, a) the BBB in the unirradiated area outside the radiation portal was not changed, b) the degree of destructive effect on the BBB in the irradiated normal area was directly proportional to the radiation dose. For 30-40 Gy, the count/pixel change enhances to average 24.7% [(147.6-118.4)/118.4], and c) the BBB in the tumor area is partially destroyed on an average of 22.1% [(206.8-169.4)/169.4] by the tumor. The radiotherapy further enhances this effect to an average of 74.7% [(206.8-118.4)/118.4]. Case 3 showed that before radiation, the degree of destructive effect on the BBB in the tumor area was 22% [(167-137)/137] higher than normal brain tissue. After a dose of 30 Gy of irradiation, it increased to 76.7% [(242-137)/137]; 8 months later it decreased to 17% [(160.3-137)/137]. It has been proven that the BBB can recover at least partially. Based on these observations, the authors believe that in the combined treatment of operated brain tumors, radiotherapy should precede chemotherapy so as to enhance the destruction of the BBB, facilitating the incorporation of drugs into the tumor. The dose at which to start chemotherapy is 20-30 Gy.

Three-dimensional structure of Escherichia coli dihydrodipicolinate reductase in complex with NADH and the inhibitor 2,6-pyridinedicarboxylate

Dihydrodipicolinate reductase catalyzes the NAD(P)H-dependent reduction of the alpha,beta-unsaturated cyclic imine dihydrodipicolinate to form the cyclic imine tetrahydrodipicolinate. The enzyme is a component of the biosynthetic pathway that leads to diaminopimelate and lysine in bacteria and higher plants. Because these pathways are unique to microorganisms and plants, they may represent attractive targets for new antimicrobial or herbicidal compounds. The three-dimensional structure of the ternary complex of Escherichia coli dihydrodipicolinate reductase with NADH and the inhibitor 2,6-pyridinedicarboxylate has been solved using a combination of molecular replacement and noncrystallographic symmetry averaging procedures and refined against 2.6 A resolution data to a crystallographic R-factor of 21.4% (Rfree is 29.7%). The native enzyme is a 120 000 molecular weight tetramer of identical subunits. The refined crystallographic model contains a tetramer, three molecules of NADH, three molecules of inhibitor, one phosphate ion, and 186 water molecules per asymmetric unit. Each subunit consists of two domains connected by two flexible hinge regions. While three of the four subunits of the tetramer have a closed conformation, in which the nicotinamide ring of the cofactor bound to the N-terminal domain and the reducible carbon of the substrate bound to the substrate binding domain are about 3.5 A away, the fourth subunit is unliganded and shows an open conformation, suggesting that the enzyme undergoes a major conformational change upon binding of both substrates. The residues involved in binding of the inhibitor and the residues involved in catalysis have been identified on the basis of the three-dimensional structure. Site-directed mutants have been used to further characterize the role of these residues in binding and catalysis. A chemical mechanism for the enzyme, based on these and previously reported data, is proposed.

Structural symmetry: the three-dimensional structure of Haemophilus influenzae diaminopimelate epimerase

The Haemophilus influenzae diaminopimelate epimerase was cloned, expressed, purified, and crystallized in the C2221 space group (a = 102.1 A, b = 115.4 A, c = 66.3 A, alpha = beta = gamma = 90 degrees). The three-dimensional structure was solved to 2.7 A using a single Pt derivative and the Se-Met-substituted enzyme to a conventional R factor of 19.0% (Rfree = 24.2%). The 274 amino acid enzyme consists of two structurally homologous domains, each containing eight beta-strands and two alpha-helices. Diaminopimelate epimerase is a representative of the PLP-independent amino acid racemases, for which no structure has yet been determined and substantial evidence exists supporting the role of two cysteine residues as the catalytic acid and base. Cys73 of the amino terminal domain is found in disulfide linkage, at the domain interface, with Cys217 of the carboxy terminal domain, and we suggest that these two cysteine residues in the reduced, active enzyme function as the acid and base in the mechanism.

Autoantibody production from a thymoma and a follicular dendritic cell sarcoma associated with paraneoplastic pemphigus

BACKGROUND

Paraneoplastic pemphigus (PNP) is an autoimmune mucocutaneous disease. We previously reported that B cells in a Castleman tumour associated with PNP produced autoantibodies. However, it is uncertain whether the production of autoantibodies from the associated tumour is a common mechanism in PNP.

OBJECTIVES

To investigate autoantibody production in a thymoma and a follicular dendritic cell sarcoma that were excised from two patients with PNP.

METHODS

Tumour cells were cultured, and their surface markers were identified. Indirect immunofluorescence, immunoblotting and enzyme-linked immunosorbent assay (ELISA) using culture media from the tumours were used to detect PNP autoantibodies.

RESULTS

B cells with markers (CD22+, surface membrane IgG+ and surface membrane IgM+) of mature B lymphocytes constituted a proportion of cultured tumour cells in both tumours. Western blot showed that the medium from both the thymoma and the follicular dendritic cell sarcoma cells recognized 190-kDa periplakin and 210-kDa envoplakin bands of human epithelial proteins as well as recombinant linker regions of periplakin, envoplakin, desmoplakin and bullous pemphigoid antigen 1. ELISA was positive for antidesmoglein 3 antibody.

CONCLUSIONS

The presence and localization in tumours of B-lymphocyte clones against proteins of the plakin family and desmoglein 3 in skin may not be confined to PNP with Castleman disease, but is possibly a common mechanism in PNP associated with various tumours.

Divergent immune responses in male and female mice after trauma-hemorrhage: dimorphic alterations in T lymphocyte steroidogenic enzyme activities

Immune responses are suppressed in males, but not in proestrous females, after trauma-hemorrhage. Testosterone and 17beta-estradiol appear to be responsible for divergent immune effects. There is considerable evidence to suggest sex steroid hormone involvement in immune functions. As formation of active steroid depends on the activity of androgen- and estrogen-synthesizing enzymes, expression and activity of 5alpha-reductase, aromatase, and 3beta- and 17beta- hydroxysteroid dehydrogenases were determined in spleen and T lymphocytes of male and proestrous female mice after trauma-hemorrhage. All of the enzymes were present in spleen, specifically in T lymphocytes. 5alpha-Reductase expression and activity increased in male T lymphocytes, whereas aromatase activity, but not expression, increased in female T lymphocytes. Increased 5alpha-reductase activity in male T lymphocytes is immunosuppressive because of increased 5alpha-dihydrotestosterone synthesis, whereas in females increased aromatase activity triggering 17beta-estradiol synthesis is immunoprotective. This study also demonstrates the importance of 17beta-hydroxysteroid dehydrogenase oxidative and reductive functions. The immunoprotection of proestrous females is associated with enhanced reductase function of the enzyme. In males, decreased expression of oxidative isomer type IV, which impairs catabolism of 5alpha-dihydrotestosterone, probably augments immunosuppression. This study provides evidence for the involvement of intracrine sex steroid synthesis in gender dimorphic immune responses after trauma-hemorrhage.

Human AML cells in NOD/SCID mice: engraftment potential and gene expression

Most cases of human acute myeloid leukemia (AML) engraft in irradiated non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. Intravenous transfer of as few as 10(5) human AML cells resulted in engraftment. Cases with poor prognosis clinical features, including FLT3 mutations, tended to engraft efficiently. Nevertheless, AML cells obtained from patients at relapse did not engraft more efficiently than cells obtained from the same patients at initial diagnosis. One passage of human AML cells in NOD/SCID mice did not appear to select for increased virulence, as measured by serial transplantation efficiency. Finally, cDNA microarray analyses indicated that approximately 95% of genes were expressed at similar levels in human AML cells immunopurified after growth in mice, as compared to cells assessed directly from patients. Thus, the growth of human AML cells in NOD/SCID mice could yield large numbers of human AML cells for direct experimental use and could also function as a renewable, potentially unlimited source of leukemia cells, via serial transplantation.

Exposure to westernization and dieting: a cross-cultural study

OBJECTIVES

The study aimed to establish whether an index of exposure to westernization would predict dieting behavior over and above the predictors of body mass index (BMI) and social influences. The study also sought to compare dieting behaviors among adolescents from three different cultural backgrounds.

METHOD

A total of 100 females from Beijing, China, 60 females of Chinese heritage living in Sydney, Australia, and 100 female Australians of no Chinese background were assessed. The exposure to westernization index incorporated the country of birth, the predominant language spoken at home, the country of birth of one's parents, and the country of residence.

RESULTS

Exposure to westernization was found to be a significant predictor of dieting status. The westernization index remained an important predictor when BMI and social influences to diet were taken into account. Interestingly, the Chinese Australian girls dieted the least, although the Chinese girls living in China perceived more influence from their peers to diet, despite their lower BMI.

CONCLUSION

The exposure to westernization index provides a useful assessment of important influences on dieting in adolescent females.

Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the Haemophilus influenzae dapE-encoded desuccinylase: metal activation, solvent isotope effects, and kinetic mechanism

Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the dapE-encoded desuccinylase is required for the bacterial synthesis of lysine and meso-diaminopimelic acid. We have investigated the catalytic mechanism of the recombinant enzyme from Haemophilus influenzae. The desuccinylase was overexpressed in Escherichia coli and purified to homogeneity. Steady-state kinetic experiments verified that the enzyme is metal-dependent, with a Km for N-succinyl-L,L-diaminopimelic acid of 1.3 mM and a turnover number of 200 s-1 in the presence of zinc. The maximal velocity was independent of pH above 7 but decreased with a slope of 1 below pH 7. The pH dependence of V/K was bell-shaped with apparent pKs of 6.5 and 8.3. Both L,L- and D,L-diaminopimelic acid were competitive inhibitors of the substrate, but d,d-diaminopimelic acid was not. Solvent kinetic isotope effect studies yielded inverse isotope effects, with values for D2OV/K of 0.62 and D2OV of 0.78. Determination of metal stoichiometry by ICP-AES indicated one tightly bound metal ion, while sequence homologies suggest the presence of two metal binding sites. On the basis of these observations, we propose a chemical mechanism for this metalloenzyme, which has a number of important structurally defined homologues.

Neuropeptide-stimulated cell migration in prostate cancer cells is mediated by RhoA kinase signaling and inhibited by neutral endopeptidase

The neuropeptides bombesin and endothelin-1 stimulate prostate cancer (PC) cell migration and invasion (J Clin Invest, 2000; 106: 1399-1407). The intracellular signaling pathways that direct this cell movement are not well delineated. The monomeric GTPase RhoA is required for migration in several cell types including neutrophils, monocytes and fibroblasts. We demonstrate that bombesin-stimulated PC cell migration occurs via the heterotrimeric G-protein-coupled receptors (G-protein) G alpha 13 subunit leading to activation of RhoA, and Rho-associated coiled-coil forming protein kinase (ROCK). Using siRNA to suppress expression of the three known G-protein alpha-subunit-associated RhoA guanine nucleotide exchange factors (GEFs), we also show that two of these RhoA GEFs, PDZ-RhoGEF and leukemia-associated RhoGEF (LARG), link bombesin receptors to RhoA in a non-redundant manner in PC cells. We next show that focal adhesion kinase, which activates PDZ-RhoGEF and LARG, is required for bombesin-stimulated RhoA activation. Neutral endopeptidase (NEP) is expressed on normal prostate epithelium whereas loss of NEP expression contributes to PC progression. We also demonstrate that NEP inhibits neuropeptide activation of RhoA. Together, these results establish a contiguous signaling pathway from the bombesin receptor to ROCK in PC cells, and they implicate NEP as a major regulator of neuropeptide-stimulated RhoA in these cells. This work also identifies members of this signaling pathway as potential targets for rational pharmacologic manipulation of neuropeptide-stimulated migration of PC cells.