Osteoprotegerin is a receptor for the cytotoxic ligand TRAIL

TRAIL is a tumor necrosis factor-related ligand that induces apoptosis upon binding to its death domain-containing receptors, DR4 and DR5. Two additional TRAIL receptors, TRID/DcR1 and DcR2, lack functional death domains and function as decoy receptors for TRAIL. We have identified a fifth TRAIL receptor, namely osteoprotegerin (OPG), a secreted tumor necrosis factor receptor homologue that inhibits osteoclastogenesis and increases bone density in vivo. OPG-Fc binds TRAIL with an affinity of 3.0 nM, which is slightly weaker than the interaction of TRID-Fc or DR5-Fc with TRAIL. OPG inhibits TRAIL-induced apoptosis of Jurkat cells. Conversely, TRAIL blocks the anti-osteoclastogenic activity of OPG. These data suggest potential cross-regulatory mechanisms by OPG and TRAIL.

Diverse spermatogenic defects in humans caused by Y chromosome deletions encompassing a novel RNA-binding protein gene

We have detected deletions of portions of the Y chromosome long arm in 12 of 89 men with azoospermia (no sperm in semen). No Y deletions were detected in their male relatives or in 90 other fertile males. The 12 deletions overlap, defining a region likely to contain one or more genes required for spermatogenesis (the Azoospermia Factor, AZF). Deletion of the AZF region is associated with highly variable testicular defects, ranging from complete absence of germ cells to spermatogenic arrest with occasional production of condensed spermatids. We find no evidence of YRRM genes, recently proposed as AZF candidates, in the AZF region. The region contains a single-copy gene, DAZ (Deleted in AZoospermia), which is transcribed in the adult testis and appears to encode an RNA binding protein. The possibility that DAZ is AZF should now be explored.

The product of ras is a GTPase and the T24 oncogenic mutant is deficient in this activity

Ha-ras is a member of a multigene family in man which encode highly related proteins of 189 amino acids (p21). In vitro, ras proteins bind GTP, and p21 mutants with treonine at position 59 autophosphorylate at that residue. Mutation (at amino acids 12 or 61) and elevated expression of ras genes result in cell transformation in culture, and are also observed in many types of human tumours. Normal and mutant transforming ras proteins show no differences in localization, lipidation or GTP binding. However, mutations at position 12 in recombinant (Thr 59) p21 molecules were observed to affect autophosphorylation. We have expressed the full-length normal and T24 transforming (Gly----Val at position 12) Ha-ras proteins in Escherichia coli and have purified them to homogeneity (ref. 19 and M.G. et al., in preparation); these proteins bound GTP with approximately molar stoichiometry and with an affinity comparable to partially purified mammalian proteins. Microinjection of the T24 protein into quiescent rodent fibroblasts resulted in a rapid alteration in cell morphology, stimulation of DNA synthesis and cell division; in contrast, little response was observed with the normal protein. We now report that the normal ras protein has an intrinsic GTPase activity, yielding GDP and Pi. In contrast, the T24 transforming protein is reduced 10-fold in this activity. We suggest that this deficiency in GTPase is the probable cause for the transforming phenotype of the T24 protein.

Clinical and immunologic criteria for the diagnosis of allergic bronchopulmonary aspergillosis

Clinical and immunologic characteristics are reported in a series of 20 patients with allergic bronchopulmonary aspergillosis seen by physicians in one consulting service during a period of 9 years. Seventeen of these patients have been identified in the past 2 years, reflecting the increasing recognition of the entity. Fifteen of the 20 patients are believed to have proven diagnoses; the other five are strongly suspected. Asthma, pulmonary infiltrates, and eosinophilia are the usual presenting symptoms. Serum immunoglobulin E was markedly elevated in all patients, and serum immunoglobulin D was normal in four out of five patients sampled. Bronchograms were abnormal in all cases in which they could be done. Lymphocyte transformation may be present in some cases but is not a diagnostic feature. The average age at time of diagnosis was 25.5 years, and seven of the 15 proven patients were 20 or younger.

Crystal structure of an HIV-binding recombinant fragment of human CD4

CD4 glycoprotein on the surface of T cells helps in the immune response and is the receptor for HIV infection. The structure of a soluble fragment of CD4 determined at 2.3 A resolution reveals that the molecule has two intimately associated immunoglobulin-like domains. Residues implicated in HIV recognition by analysis of mutants and antibody binding are salient features in domain D1. Domain D2 is distinguished by a variation on the beta-strand topologies of antibody domains and by an intra-sheet disulphide bridge.

Microinjection of the oncogene form of the human H-ras (T-24) protein results in rapid proliferation of quiescent cells

Using an E. coli expression-vector system we have efficiently produced, purified, and characterized the full-length, nonfused, protooncogenic and oncogenic (T-24) forms of the human H-ras gene product. These purified ras proteins have been introduced by microinjection into a variety of somatic cells in an effort to examine their function. Within several hours after injection of the oncogenic form of the human H-ras protein into quiescent cells, we observe dramatic morphological changes followed by transient proliferation of the cells. In contrast, microinjection of the normal, protooncogenic form of the ras protein at the same level appears to have only little effect on the cells. Additional experiments indicate that the effect of the ras protein requires entry into the cells, is temporary, is inhibited by cycloheximide or actinomycin D, and is seen only in established cell lines. This experimental approach demonstrates that the bacterially derived and purified human H-ras proteins retain their ability to function when put back into mammalian cells and furthermore, provides a novel assay for transformation induced in established cells by the human H-ras oncogene protein.

Identification of critical staphylococcal genes using conditional phenotypes generated by antisense RNA

Comprehensive genomic analysis of the important human pathogen Staphylococcus aureus was achieved by a strategy involving antisense technology in a regulatable gene expression system. In addition to known essential genes, many genes of unknown or poorly defined biological function were identified. This methodology allowed gene function to be characterized in a comprehensive, defined set of conditionally growth-defective/lethal isogenic strains. Quantitative titration of the conditional growth effect was performed either in bacterial culture or in an animal model of infection. This genomic strategy offers an approach to the identification of staphylococcal gene products that could serve as targets for antibiotic discovery.

The relationship between function and DNA sequence in an intercistronic regulatory region in phage lambda

rho factor-mediated transcription termination at the tr1 terminator site of bacteriophage lambda is examined. Mutations affecting the termination event are characterised. These mutations define features of the site which seem to be important to terminator function. In addition, other related transcriptional and translational regulatory elements are defined within the region surrounding the termination site. The potential molecular interactions and structural overlaps of these control signals apparently couple the regulation of the decision between lytic and lysogenic growth patterns by phage lambda.

Microinjected c-myc as a competence factor

While a number of oncogenes are expressed in a cell cycle-dependent manner, their role in the control of cell proliferation can only be established by a direct functional assay. The c-myc protein, upon microinjection into nuclei of quiescent Swiss 3T3 cells, cooperated with platelet-poor plasma in the stimulation of cellular DNA synthesis. This suggests that c-myc protein, like platelet-derived growth factor (PDGF), may act as a competence factor in the cell cycle to promote the progression of cells to S phase. The presence in the medium of an antibody against PDGF abolished DNA synthesis induced by microinjected PDGF; however, the microinjected c-myc protein stimulated DNA synthesis even when its own antibody was present in the medium. The c-myc protein may act as an intracellular competence factor, while PDGF expresses its biological activity only from outside the cells.

gridlock, an HLH gene required for assembly of the aorta in zebrafish

The first artery and vein of the vertebrate embryo assemble in the trunk by migration and coalescence of angioblasts to form endothelial tubes. The gridlock (grl) mutation in zebrafish selectively perturbs assembly of the artery (the aorta). Here it is shown that grl encodes a basic helix-loop-helix (bHLH) protein belonging to the Hairy/Enhancer of the split family of bHLH proteins. The grl gene is expressed in lateral plate mesoderm before vessel formation, and thereafter in the aorta and not in the vein. These results suggest that the arterial endothelial identity is established even before the onset of blood flow and implicate the grl gene in assignment of vessel-specific cell fate.

The effects of a 5-lipoxygenase inhibitor on asthma induced by cold, dry air

BACKGROUND

The enzyme 5-lipoxygenase catalyzes the metabolism of arachidonic acid to form products that have been implicated in the airway obstruction of asthma. We hypothesized that if products of the 5-lipoxygenase pathway are important in mediating this obstruction, then prevention of their formation should decrease the severity of an induced asthmatic response.

METHODS

In a randomized, double-blind, placebo-controlled, crossover study, we examined the effect of A-64077, a 5-lipoxygenase inhibitor, on the bronchoconstriction induced by hyperventilation of cold, dry air in 13 patients with asthma. The completeness of 5-lipoxygenase inhibition was confirmed by examining the profile of eicosanoids produced in whole blood ex vivo after activation with the calcium ionophore A-23187.

RESULTS

A-64077 decreased the mean (+/- SEM) ionophore-induced synthesis of leukotriene B4, a 5-lipoxygenase product, by 74 percent (from 265.3 +/- 30.3 to 69.5 +/- 21.5 ng per milliliter, P less than 0.001), but it did not affect the ionophore-induced synthesis of thromboxane B2, a cyclooxygenase metabolite of arachidonic acid (80.0 +/- 17.1 ng per milliliter before A-64077 vs. 75.8 +/- 14.3 ng per milliliter after A-64077). In concert with the selective inhibition of 5-lipoxygenase by A-64077, the amount of cold, dry air (expressed as respiratory heat exchange) required to reduce the forced expiratory volume in one second by 10 percent was increased by 47 percent after A-64077 (3.0 kJ per minute for placebo vs. 4.4 kJ per minute for A-64077, P less than 0.002). Similar results were obtained when minute ventilation was used as an indicator of outcome (27.5 liters per minute for placebo vs. 39.8 liters per minute for A-64077, P less than 0.005).

CONCLUSIONS

Selective inhibition of 5-lipoxygenase by A-64077 is associated with a significant amelioration of the asthmatic response to cold, dry air, suggesting that 5-lipoxygenase products are involved in this response. This approach may be useful in the treatment of asthma.

Tissue-specific and differentiation-specific expression of a human K14 keratin gene in transgenic mice

A construct containing approximately 2500 base pairs (bp) of 5' upstream and approximately 700 bp of 3' downstream sequence was used to drive the expression of an intronless human K14 gene in vitro and in vivo. To track the expression of the gene, a small sequence encoding the antigenic portion of neuropeptide substance P was inserted in frame 5' to the TGA translation stop codon of the gene. Surprisingly, this gene was expressed promiscuously in a wide variety of cultured cells transiently transfected with the construct. In contrast, when introduced into the germ line of transgenic mice, the construct was expressed in a fashion analogous to the endogenous K14 gene--namely, in the basal layer of stratified squamous epithelia. Our results suggest that some regulatory mechanism is overridden as a consequence of transient transfection but that sequences that can control proper K14 expression are present in the construct. The appropriate tissue-specific and differentiation-specific expression of K14.P in transgenic mice is an important first step in characterizing a promoter that could be employed to drive the foreign expression of drug-related genes in the epidermis of skin grafts.

The selective sphingosine 1-phosphate receptor modulator BAF312 redirects lymphocyte distribution and has species-specific effects on heart rate

BACKGROUND AND PURPOSE

BAF312 is a next-generation sphingosine 1-phosphate (S1P) receptor modulator, selective for S1P₁ and S1P₅ receptors. S1P₁ receptors are essential for lymphocyte egress from lymph nodes and a drug target in immune-mediated diseases. Here, we have characterized the immunomodulatory potential of BAF312 and the S1P receptor-mediated effects on heart rate using preclinical and human data.

EXPERIMENTAL APPROACH

BAF312 was tested in a rat experimental autoimmune encephalomyelitis (EAE) model. Electrophysiological recordings of G-protein-coupled inwardly rectifying potassium (GIRK) channels were carried out in human atrial myocytes. A Phase I multiple-dose trial studied the pharmacokinetics, pharmacodynamics and safety of BAF312 in 48 healthy subjects.

KEY RESULTS

BAF312 effectively suppressed EAE in rats by internalizing S1P₁ receptors, rendering them insensitive to the egress signal from lymph nodes. In healthy volunteers, BAF312 caused preferential decreases in CD4⁺ T cells, T_naïve, T_{central memory} and B cells within 4–6 h. Cell counts returned to normal ranges within a week after stopping treatment, in line with the elimination half-life of BAF312. Despite sparing S1P₃ receptors (associated with bradycardia in mice), BAF312 induced rapid, transient (day 1 only) bradycardia in humans. BAF312-mediated activation of GIRK channels in human atrial myocytes can fully explain the bradycardia.

CONCLUSION AND IMPLICATIONS

This study illustrates species-specific differences in S1P receptor specificity for first-dose cardiac effects. Based on its profound but rapidly reversible inhibition of lymphocyte trafficking, BAF312 may have potential as a treatment for immune-mediated diseases.

Reproducibility and sensitivity of oral malodor measurements with a portable sulphide monitor

Forty-one subjects with bad breath were assessed for oral malodor and periodontal status on three occasions, at intervals of approximately one week. Oral malodor was assessed by measurement of peak and steady-state volatile sulphide levels with a portable sulphide monitor and by organoleptic measurement of whole-mouth, tongue dorsum, and interproximal dental odors by two independent judges. Reproducibility of measurements, assessed by paired t tests and Kappa testing, demonstrated no significant differences between any of the test results from the first and second appointments. Steady-state sulphide levels were the most reproducible of all tests. The ability of the tests to detect an expected reduction of malodor following a 0.2% chlorhexidine mouthrinse regimen was investigated by comparison of test values between the second and third appointments. Following the mouthrinsing treatment, 43% reductions of peak, 47% reductions of steady-state volatile sulphide levels, and 15-58% reductions in all other measurement categories were observed. The majority of the participants (22/41) had no pockets greater than 5 mm and exhibited both moderate gingival inflammation (Mean Gingival Index = 1.17) and moderate plaque accumulation (Mean Plaque Index = 1.84). Plaque Index and presence of pockets greater than 7 mm were weakly related to sulphide measurements. Whereas assessment of steady-state sulphide levels by the sulphide monitor does not constitute a direct measure of oral malodor, its relation to organoleptic measurement, superior reproducibility, objectivity, and sensitivity support the use of the sulphide monitor in clinical studies.

A genomic analysis of two-component signal transduction in Streptococcus pneumoniae

A genomics-based approach was used to identify the entire gene complement of putative two-component signal transduction systems (TCSTSs) in Streptococcus pneumoniae. A total of 14 open reading frames (ORFs) were identified as putative response regulators, 13 of which were adjacent to genes encoding probable histidine kinases. Both the histidine kinase and response regulator proteins were categorized into subfamilies on the basis of phylogeny. Through a systematic programme of mutagenesis, the importance of each novel TCSTS was determined with respect to viability and pathogenicity. One TCSTS was identified that was essential for the growth of S. pneumoniaeThis locus was highly homologous to the yycFG gene pair encoding the essential response regulator/histidine kinase proteins identified in Bacillus subtilis and Staphylococcus aureus. Separate deletions of eight other loci led in each case to a dramatic attenuation of growth in a mouse respiratory tract infection model, suggesting that these signal transduction systems are important for the in vivo adaptation and pathogenesis of S. pneumoniae. The identification of conserved TCSTSs important for both pathogenicity and viability in a Gram-positive pathogen highlights the potential of two-component signal transduction as a multicomponent target for antibacterial drug discovery.

Copper metallothionein of yeast, structure of the gene, and regulation of expression

Addition of copper to yeast cells leads to the induction of a low molecular weight, cysteine-rich protein that binds copper. This protein, termed copper chelatin or thionein, is related to the metallothionein family of proteins that are induced in response to cadmium and zinc in vertebrate cells. We have determined the structure of the yeast copper-binding protein by DNA sequence analysis of the gene. Although the 6573-dalton yeast protein is substantially divergent from vertebrate metallothioneins, the arrangement of 12 cysteine residues, which is a hallmark of metal-binding proteins, is partially conserved. We analyzed the regulatory DNA sequence of the gene by fusing it with the Escherichia coli galactokinase gene and assaying the levels of enzyme activity in yeast in response to copper. The transcriptional activation has a specific requirement for copper. Zinc, cadmium, and gold were unable to regulate the galactokinase activity. The yeast copper metallothionein regulatory sequences represent a previously unreported class of yeast promoter that is regulated by copper.

Human immunodeficiency virus protease expressed in Escherichia coli exhibits autoprocessing and specific maturation of the gag precursor

The mature gag and pol proteins of human immunodeficiency virus (HIV) and all retroviruses derive from large gag and gag-pol polyprotein precursors by posttranslational cleavage. A highly specific, virally encoded protease is required for this essential proteolytic processing. In this study, the HIV protease gene product was expressed in Escherichia coli and shown to autocatalyze its maturation from a larger precursor. In addition, this bacterially produced HIV protease specifically processed an HIV p55 gag polyprotein precursor when coexpressed in E. coli. This system will allow detailed structure-function analysis of the HIV protease and provides a simple assay for the development of potential therapeutic agents directed against this critical viral enzyme.

Evolution of two-component signal transduction

Two-component signal transduction (TCST) systems are the principal means for coordinating responses to environmental changes in bacteria as well as some plants, fungi, protozoa, and archaea. These systems typically consist of a receptor histidine kinase, which reacts to an extracellular signal by phosphorylating a cytoplasmic response regulator, causing a change in cellular behavior. Although several model systems, including sporulation and chemotaxis, have been extensively studied, the evolutionary relationships between specific TCST systems are not well understood, and the ancestry of the signal transduction components is unclear. Phylogenetic trees of TCST components from 14 complete and 6 partial genomes, containing 183 histidine kinases and 220 response regulators, were constructed using distance methods. The trees showed extensive congruence in the positions of 11 recognizable phylogenetic clusters. Eukaryotic sequences were found almost exclusively in one cluster, which also showed the greatest extent of domain variability in its component proteins, and archaeal sequences mainly formed species-specific clusters. Three clusters in different parts of the kinase tree contained proteins with serine-phosphorylating activity. All kinases were found to be monophyletic with respect to other members of their superfamily, such as type II topoisomerases and Hsp90. Structural analysis further revealed significant similarity to the ATP-binding domain of eukaryotic protein kinases. TCST systems are of bacterial origin and radiated into archaea and eukaryotes by lateral gene transfer. Their components show extensive coevolution, suggesting that recombination has not been a major factor in their differentiation. Although histidine kinase activity is prevalent, serine kinases have evolved multiple times independently within this family, accompanied by a loss of the cognate response regulator(s). The structural and functional similarity between TCST kinases and eukaryotic protein kinases raises the possibility of a distant evolutionary relationship.

Purified lambda regulatory protein cII positively activates promoters for lysogenic development

The bacteriophage lambda regulatory protein, cII, has been purified and shown to activate positively RNA transcription from the two phage promoters which coordinately regulate phage lysogenic development. To obtain this protein, the cII gene was cloned into a plasmid vector carrying the strong, regulatable lambda phage promoter PL such that it was overproduced to levels approaching 5% of cellular protein.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera-electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

Activation of human immunodeficiency virus type 1 by DNA damage in human cells

Recent studies indicate that human immunodeficiency virus type 1 (HIV) gene expression can be dramatically enhanced by certain heterologous viral and chemical agents, implicating these as potential reactivating agents of latent virus infection. A common denominator shared by these agents is their ability to cause stress responses in cells. In an effort to determine whether stress responses affect HIV gene expression, we examined the effects of ultraviolet light (UV) and mitomycin C, on HIV gene expression as well as on viral growth and development. We demonstrate that these agents enhance HIV gene expression up to 150-fold. These levels are similar to those obtained by the tat gene product, the HIV trans-activating factor responsible for enhancing viral gene expression. The increase in gene expression after UV irradiation appears to require transcription but not de novo protein synthesis, and correlates with an accumulation of stable mRNA. Most importantly, UV irradiation of human T-cells prior to viral infection significantly shortens the viral growth cycle. Apparently, UV-induced cellular stress is highly conducive for viral replication and growth. We further demonstrate that even direct sunlight can activate HIV gene expression. These results demonstrate that DNA damaging agents, and perhaps other agents which elicit SOS-like stress responses in mammalian cells, can activate HIV expression thereby enhancing viral replication and development.

Measurement of oral malodor: current methods and future prospects

Measurement of oral malodor is complicated by a variety of parameters including complexity of gaseous molecular species, sampling difficulties, temporal variations, choice of suitable subject populations, and lack of agreement on reference standards. Since oral malodor is a perceived olfactory stimulus, direct sampling and assessment by human judges may be the most logical measurement approach. However, as with other psychophysical assessments, human malodor measurement by the human nose may vary widely among and between judges, and consequently cannot be confidently reproduced in other laboratories. Such shortcomings have led several investigators to propose quantitative approaches based on measurement of volatile sulfide compounds which are associated with oral malodor. Highly sensitive and discriminatory measurements of volatile sulfides can be made using gas chromatography although for rapid sampling of larger subject populations, portable sulfide monitors may be more appropriate. Future research in this field should consider: 1) improved and simplified instrumentation for more rapid through-put and reliability; 2) development and definition of reference standards for oral malodor assessment; 3) formulation of clinical studies with appropriately sized, well-defined patient populations; and 4) further development of within mouth, site-specific measurements.

Translational coupling at an intercistronic boundary of the Escherichia coli galactose operon

Precise frameshift and nonsense mutations were introduced into the region preceding the galactokinase gene (galK) of Escherichia coli. These mutations after the position at which upstream translation terminates relative to the galK translation initiation signal. Constructions were characterized that allow ribosomes to stop selectively before, within or downstream from the galK initiation signal. The effects of these mutations on galK expression were monitored. Galactokinase levels are highest when upstream translation terminates within the galK initiation region. In contrast, when translation stops either upstream or down stream from the galK start site, galK expression is drastically reduced. These results demonstrate that the galK gene is translationally coupled to the gene immediately preceding galK in the gal operon (that is, galT), and that the coupling effect depends primarily on the position at which upstream translation terminates relative to the galK start site. Possible mechanisms and implications of this translational coupling phenomenon are discussed.