Bid, a Bcl2 interacting protein, mediates cytochrome c release from mitochondria in response to activation of cell surface death receptors

We report here the purification of a cytosolic protein that induces cytochrome c release from mitochondria in response to caspase-8, the apical caspase activated by cell surface death receptors such as Fas and TNF. Peptide mass fingerprinting identified this protein as Bid, a BH3 domain-containing protein known to interact with both Bcl2 and Bax. Caspase-8 cleaves Bid, and the COOH-terminal part translocates to mitochondria where it triggers cytochrome c release. Immunodepletion of Bid from cell extracts eliminated the cytochrome c releasing activity. The cytochrome c releasing activity of Bid was antagonized by Bcl2. A mutation at the BH3 domain diminished its cytochrome c releasing activity. Bid, therefore, relays an apoptotic signal from the cell surface to mitochondria.

Apaf-1, a human protein homologous to C. elegans CED-4, participates in cytochrome c-dependent activation of caspase-3

We report here the purification and cDNA cloning of Apaf-1, a novel 130 kd protein from HeLa cell cytosol that participates in the cytochrome c-dependent activation of caspase-3. The NH2-terminal 85 amino acids of Apaf-1 show 21% identity and 53% similarity to the NH2-terminal prodomain of the Caenorhabditis elegans caspase, CED-3. This is followed by 320 amino acids that show 22% identity and 48% similarity to CED-4, a protein that is believed to initiate apoptosis in C. elegans. The COOH-terminal region of Apaf-1 comprises multiple WD repeats, which are proposed to mediate protein-protein interactions. Cytochrome c binds to Apaf-1, an event that may trigger the activation of caspase-3, leading to apoptosis.

An APAF-1.cytochrome c multimeric complex is a functional apoptosome that activates procaspase-9

We report here the reconstitution of the de novo procaspase-9 activation pathway using highly purified cytochrome c, recombinant APAF-1, and recombinant procaspase-9. APAF-1 binds and hydrolyzes ATP or dATP to ADP or dADP, respectively. The hydrolysis of ATP/dATP and the binding of cytochrome c promote APAF-1 oligomerization, forming a large multimeric APAF-1.cytochrome c complex. Such a complex can be isolated using gel filtration chromatography and is by itself sufficient to recruit and activate procaspase-9. The stoichiometric ratio of procaspase-9 to APAF-1 is approximately 1 to 1 in the complex. Once activated, caspase-9 disassociates from the complex and becomes available to cleave and activate downstream caspases such as caspase-3.

DFF, a heterodimeric protein that functions downstream of caspase-3 to trigger DNA fragmentation during apoptosis

We have identified and purified from HeLa cytosol a protein that induces DNA fragmentation in coincubated nuclei after it is activated by caspase-3. This protein, designated DNA Fragmentation Factor (DFF), is a heterodimer of 40 kDa and 45 kDa subunits. The amino acid sequence of the 45 kDa subunit, determined from its cDNA sequence, reveals it to be a novel protein. Caspase-3 cleaves the 45 kDa subunit at two sites to generate an active factor that produces DNA fragmentation without further requirement for caspase-3 or other cytosolic proteins. In cells undergoing apoptosis, the 45 kDa subunit is cleaved in the same pattern as it is cleaved by caspase-3 in vitro. These data delineate a direct signal transduction pathway during apoptosis: caspase-3 to DFF to DNA fragmentation.

Identification of a vertebrate sister-chromatid separation inhibitor involved in transformation and tumorigenesis

A vertebrate securin (vSecurin) was identified on the basis of its biochemical analogy to the Pds1p protein of budding yeast and the Cut2p protein of fission yeast. The vSecurin protein bound to a vertebrate homolog of yeast separins Esp1p and Cut1p and was degraded by proteolysis mediated by an anaphase-promoting complex in a manner dependent on a destruction motif. Furthermore, expression of a stable Xenopus securin mutant protein blocked sister-chromatid separation but did not block the embryonic cell cycle. The vSecurin proteins share extensive sequence similarity with each other but show no sequence similarity to either of their yeast counterparts. Human securin is identical to the product of the gene called pituitary tumor-transforming gene (PTTG), which is overexpressed in some tumors and exhibits transforming activity in NIH 3T3 cells. The oncogenic nature of increased expression of vSecurin may result from chromosome gain or loss, produced by errors in chromatid separation.

Requirement for BMP signaling in interdigital apoptosis and scale formation

Interdigital cell death leads to regression of soft tissue between embryonic digits in many vertebrates. Although the signals that regulate interdigital apoptosis are not known, BMPs--signaling molecules of the transforming growth factor-beta superfamily--are expressed interdigitally. A dominant negative type I BMP receptor (dnBMPR-IB) was used here to block BMP signaling. Expression of dnBMPR in chicken embryonic hind limbs greatly reduced interdigital apoptosis and resulted in webbed feet. In addition, scales were transformed into feathers. The similarity of the webbing to webbed duck feet led to studies that indicate that BMPs are not expressed in the duck interdigit. These results indicate BMP signaling actively mediates cell death in the embryonic limb.

The 40-kDa subunit of DNA fragmentation factor induces DNA fragmentation and chromatin condensation during apoptosis

We report here the reconstitution of a pathway that leads to the apoptotic changes in nuclei by using recombinant DNA fragmentation factor (DFF), a heterodimeric protein of 40 and 45 kDa. Coexpression of DFF40 and DFF45 is required to generate recombinant DFF, which becomes activated when DFF45 is cleaved by caspase-3. The cleaved fragments of DFF45 dissociate from the DFF40, the active component of DFF. Purified DFF40 exhibited an intrinsic DNase activity that was markedly stimulated by chromatin-associated proteins histone H1 and high mobility group proteins. DFF40 also triggered chromatin condensation when incubated with nuclei. These data suggest that DFF40 is sufficient to trigger both DNA fragmentation and chromatin condensation during apoptosis.

Distinct roles of type I bone morphogenetic protein receptors in the formation and differentiation of cartilage

The bone morphogenetic proteins (BMPs), TGF beta superfamily members, play diverse roles in embryogenesis, but how the BMPs exert their action is unclear and how different BMP receptors (BMPRs) contribute to this process is not known. Here we demonstrate that the two type I BMPRs, BMPR-IA and BMPR-IB, regulate distinct processes during chick limb development. BmpR-IB expression in the embryonic limb prefigures the future cartilage primordium, and its activity is necessary for the initial steps of chondrogenesis. During later chondrogenesis, BmpR-IA is specifically expressed in prehypertrophic chondrocytes. BMPR-IA regulates chondrocyte differentiation, serving as a downstream mediator of Indian Hedgehog (IHH) function in both a local signaling loop and a longer-range relay system to PTHrP. BMPR-IB also regulates apoptosis: Expression of activated BMPR-IB results in increased cell death, and we showed previously that dominant-negative BMPR-IB inhibits apoptosis. Our studies indicate that in TGF beta signaling systems, different type I receptor isoforms are dedicated to specific functions during embryogenesis.

Dual inhibition of sister chromatid separation at metaphase

Separation of sister chromatids in anaphase is mediated by separase, an endopeptidase that cleaves the chromosomal cohesin SCC1. Separase is inhibited by securin, which is degraded at the metaphase-anaphase transition. Using Xenopus egg extracts, we demonstrate that high CDC2 activity inhibits anaphase but not securin degradation. We show that separase is kept inactive under these conditions by a mechanism independent of binding to securin. Mutation of a single phosphorylation site on separase relieves the inhibition and rescues chromatid separation in extracts with high CDC2 activity. Using quantitative mass spectrometry, we show that, in intact cells, there is complete phosphorylation of this site in metaphase and significant dephosphorylation in anaphase. We propose that separase activation at the metaphase-anaphase transition requires the removal of both securin and an inhibitory phosphate.

Virologic factors associated with failure to passive-active immunoprophylaxis in infants born to HBsAg-positive mothers

In infants born to hepatitis B surface antigen (HBsAg)-positive mothers, failure after passive-active immunization still occurs. The role of maternal hepatitis B DNA level and other risk factors in this setting remains unclear. This study retrospectively evaluated virologic and other risk factors associated with immunoprophylaxis failure in infants born to HBsAg-positive mothers. Between January 2007 and March 2010, we reviewed the clinical and virologic tests in 869 mother-infant pairs. All infants received the identical passive-active immunization schedule after birth. The failure infants (HBsAg positive at 7-12 months of age) were compared to infants who were HBsAg negative when tested during this time period. Among 869 infants, 27 (3.1%) infants were immunoprophylaxis failures and the other 842 (96.9%) infants remained HBsAg negative. When mothers' pre-delivery HBV DNA levels were stratified to <6, 6-6.99, 7-7.99 and ≥ 8 log(10) copies/mL, the corresponding rates of immunoprophylaxis failure were 0%, 3.2% (3/95), 6.7% (19/282) and 7.6% (5/66), respectively (P < 0.001 for the trend). All failure infants were born to hepatitis B e antigen (HBeAg)-positive mothers. Multivariate logistic regression analysis identified maternal HBV DNA levels [odds ratio (OR) = 1.88, 95% confidence interval (CI): 1.07-3.30] and detectable HBV DNA in the cord blood (OR = 39.67, 95% CI: 14.22-110.64) as independent risk factors for immunoprophylaxis failure. All failure infants were born to HBeAg-positive mothers with HBV DNA levels ≥ 6 log(10) copies/mL. The presence of HBV DNA in cord blood predicted failure to passive-active immunization.

Dark is a Drosophila homologue of Apaf-1/CED-4 and functions in an evolutionarily conserved death pathway

Here we identify a new gene, dark, which encodes a Drosophila homologue of mammalian Apaf-1 and Caenorhabditis elegans CED-4, cell-death proteins. Like Apaf-1, but in contrast to CED-4, Dark contains a carboxy-terminal WD-repeat domain necessary for interactions with the mitochondrial protein cytochrome c. Dark selectively associates with another protein involved in apoptosis, the fly apical caspase, Dredd. Dark-induced cell killing is suppressed by caspase-inhibitory peptides and by a dominant-negative mutant Dredd protein, and enhanced by removal of the WD domain. Loss-of-function mutations in dark attenuate programmed cell deaths during development, causing hyperplasia of the central nervous system, and other abnormalities including ectopic melanotic tumours and defective wings. Moreover, ectopic cell killing by the Drosophila cell-death activators, Reaper, Grim and Hid, is substantially suppressed in dark mutants. These findings establish dark as an important apoptosis effector in Drosophila and raise profound evolutionary considerations concerning the relationship between mitochondrial components and the apoptosis-promoting machinery.

A cyclic voltammetry method suitable for characterizing antioxidant properties of wine and wine phenolics

Phenolic antioxidants are ranked by reducing strength and characterized for reversibility using cyclic voltammetry at a glassy carbon electrode. Phenolics with an ortho-diphenol group show a first oxidation peak close to 400 mV (vs. Ag/AgCl) in a model wine solution (12% ethanol, 0.033 M tartaric acid, adjusted to pH 3.6), with a linear concentration dependence below 0.01 mM. Dilution of white wines 10x, and red wines 400x, gave first oxidation peak currents in the 1.5 to 2.2 microA range and 1.9 to 3.4 microC of charge passed by 500 mV, producing values for the concentrations of phenolic antioxidants with low oxidation potentials in the wines. Further peaks in the cyclic voltammograms of the diluted wines correspond to classes of phenolics with higher oxidation potentials, providing a qualitative assessment of wine phenolics based on reducing strength.

Holliday junctions accumulate in replication mutants via a RecA homolog-independent mechanism

The Holliday junction recombination intermediate, an X-shaped DNA molecule (xDNA), was analyzed at rDNA in mitotically growing yeast. In wild-type cells, xDNA is only detected at S phase, suggesting that recombination is stimulated to repair replication-related lesions. A search for mutations that increase the level of xDNA uncovered a gene encoding a subunit of DNA polymerase alpha. Systematic examination of replication mutants revealed that defects in polymerase alpha and delta but not the epsilon complex stimulate the level of xDNA. These xDNAs are Holliday junctions and not replication intermediates. The level of Holliday junctions is greatly reduced in rad52 mutants, but surprisingly, not in mutants defective in the three known mitotically expressed yeast RecA homologs.

Invited review: arteriolar smooth muscle mechanotransduction: Ca(2+) signaling pathways underlying myogenic reactivity

The smooth muscle of arterioles responds to an increase in intraluminal pressure with vasoconstriction and with vasodilation when pressure is decreased. Such myogenic vasoconstriction provides a level of basal tone that enables arterioles to appropriately adjust diameter in response to neurohumoral stimuli. Key in this process of mechanotransduction is the role of changes in intracellular Ca(2+). However, it is becoming clear that considerable complexity exists in the spatiotemporal characteristics of the Ca(2+) signal and that changes in intracellular Ca(2+) may play roles other than direct effects on the contractile process via activation of myosin light-chain phosphorylation. The involvement of Ca(2+) may extend to modulation of ion channels and release of Ca(2+) from the sarcoplasmic reticulum, alterations in Ca(2+) sensitivity, and coupling between cells within the vessel wall. The purpose of this brief review is to summarize the current literature relating to Ca(2+) and the arteriolar myogenic response. Consideration is given to coupling of Ca(2+) changes to the mechanical stimuli, sources of Ca(2+), involvement of ion channels, and spatiotemporal aspects of intracellular Ca(2+) signaling.

Broad antitumor and antiangiogenic activities of AG3340, a potent and selective MMP inhibitor undergoing advanced oncology clinical trials

We studied AG3340, a potent metalloproteinase (MMP) inhibitor with pM affinities for inhibiting gelatinases (MMP-2 and -9), MT-MMP-1 (MMP-14), and collagenase-3 (MMP-13) in many tumor models. AG3340 produced dose-dependent pharmacokinetics and was well tolerated after intraperitoneal (i.p.) and oral dosing in mice. Across human tumor models, AG3340 produced profound tumor growth delays when dosing began early or late after tumor implantation, although all established tumor types did not respond to AG3340. A dose-response relationship was explored in three models: COLO-320DM colon, MV522 lung, and MDA-MB-435 breast. Dose-dependent inhibitions of tumor growth (over 12.5-200 mg/kg given twice daily, b.i.d.) were observed in the colon and lung models; and in a third (breast), maximal inhibitions were produced by the lowest dose of AG3340 (50 mg/kg, b.i.d.) that was tested. In another model, AG3340 (100 mg/kg, once daily, i.p.) markedly inhibited U87 glioma growth and increased animal survival. AG3340 also inhibited tumor growth and increased the survival of nude mice bearing androgen-independent PC-3 prostatic tumors. In a sixth model, KKLS gastric, AG3340 did not inhibit tumor growth but potentiated the efficacy of Taxol. Importantly, AG3340 markedly decreased tumor angiogenesis (as assessed by CD-31 staining) and cell proliferation (as assessed by bromodeoxyuridine incorporation), and increased tumor necrosis and apoptosis (as assessed by hematoxylin and eosin and TUNEL staining). These effects were model dependent, but angiogenesis was commonly inhibited. AG3340 had a superior therapeutic index to the cytotoxic agents, carboplatin and Taxol, in the MV522 lung cancer model. In combination, AG3340 enhanced the efficacy of these cytotoxic agents without altering drug tolerance. Additionally, AG3340 decreased the number of murine melanoma (B16-F10) lesions arising in the lung in an intravenous metastasis model when given in combination with carboplatin or Taxol. These studies directly support the use of AG3340 in front-line combination chemotherapy in ongoing clinical trials in patients with advanced malignancies of the lung and prostate.

Affinity membrane chromatography for the analysis and purification of proteins

Affinity chromatography is unique among separation methods as it is the only technique that permits the purification of proteins based on biological functions rather than individual physical or chemical properties. The high specificity of affinity chromatography is due to the strong interaction between the ligand and the proteins of interest. Membrane separation allows the processing of a large amount of sample in a relatively short time owing to its structure, which provides a system with rapid reaction kinetics. The integration of membrane and affinity chromatography provides a number of advantages over traditional affinity chromatography with porous-bead packed columns, especially with regard to time and recovery of activity. This review gives detailed descriptions of materials used as membrane substrates, preparation of basic membranes, coupling of affinity ligands to membrane supports, and categories of affinity membrane cartridges. It also summarizes the applications of cellulose/glycidyl methacrylate composite membranes for proteins separation developed in our laboratory.

Activation of the apoptotic endonuclease DFF40 (caspase-activated DNase or nuclease). Oligomerization and direct interaction with histone H1

DNA fragmentation factor (DFF) is a heterodimeric protein composed of 45-kDa (DFF45) and 40-kDa (DFF40) subunits, a protein that mediates regulated DNA fragmentation and chromatin condensation in response to apoptotic signals. DFF45 is a specific molecular chaperone and an inhibitor for the nuclease activity of DFF40. Previous studies have shown that upon cleavage of DFF45 by caspase-3, the nuclease activity of DFF40 is relieved of inhibition. Here we further investigate the mechanism of DFF40 activation. We demonstrate that DFF45 can also be cleaved and inactivated by caspase-7 but not by caspase-6 and caspase-8. The cleaved DFF45 fragments dissociate from DFF40, allowing DFF40 to oligomerize to form a large functional complex that cleaves DNA by introducing double strand breaks. Histone H1 directly interacts with DFF, confers DNA binding ability to DFF, and stimulates the nuclease activity of DFF40 by increasing its Kcat and decreasing its Km.

Chromatographic separation of proteins on metal immobilized iminodiacetic acid-bound molded monolithic rods of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate)

Continuous rod of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) was prepared by a free radical polymerization within the confines of a stainless-steel column. The epoxide groups of the rod were modified by a reaction with iminodiacetic acid (IDA) that affords the active site to form metal IDA chelates used for immobilized metal affinity chromatography (IMAC). The efficiency of coupling of IDA to the epoxide-contained matrix was studied as a function of reaction time and temperature. High-performance separation of proteins, based on immobilized different metals on the column, were described. The influence of pH on the adsorption capacity of bovine serum albumin on the Cu2+-IDA continuous rod column was investigated in the range from 5.0 to 9.0. Purification of lysozyme from egg white and human serum albumin (HSA) on the commercially available HSA solution were performed on the naked IDA and Cu2+-IDA continuous rod columns, respectively; and the purity of the obtained fractions was detected by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry.

Immunomodulatory effects of acupuncture in the treatment of allergic asthma: a randomized controlled study

OBJECTIVE

According to Traditional Chinese Medicine (TCM) acupuncture is a suitable treatment for complex chronic diseases such as bronchial asthma. In a randomized, controlled study we investigated immunologic effects of Chinese acupuncture on patients with allergic asthma.

PATIENTS AND METHODS

The effects of acupuncture treatment given according to the principles of TCM (TCM group, n = 20) were compared with those of acupuncture treatment using points not specific for asthma (control group, n = 18). All patients were treated 12 times for 30 minutes over a time period of 4 weeks. Patients' general well-being and several peripheral blood parameters (eosinophils, lymphocyte subpopulations, cytokines, in vitro lymphocyte proliferation) were determined before and after acupuncture treatment.

RESULTS

In the TCM group, significantly more patients indicated an improvement in general well-being (79% in the TCM group versus 47% in the control group; p = 0.049) after acupuncture treatment. The following changes were found in the TCM group: within the lymphocyte subpopulations the CD3+ cells (p = 0.005) and CD4+ cells (p = 0.014) increased significantly. There were also significant changes in cytokine concentrations: interleukin (IL)-6 (p = 0.026) and IL-10 (p = 0.001) decreased whereas IL-8 (p = 0.050) rose significantly. Additionally, the in vitro lymphocyte proliferation rate increased significantly (p = 0.035) while the number of eosinophils decreased from 4.4% to 3.3% after acupuncture (p > 0.05). The control group, however, showed no significant changes apart from an increase in the CD4+ cells (p = 0.012).

CONCLUSION

The results imply that asthma patients benefit from acupuncture treatment given in addition to conventional therapy. Furthermore, acupuncture performed in accordance with the principles of TCM showed significant immune-modulating effects.

Capillary electrochromatography for separation of peptides driven with electrophoretic mobility on monolithic column

A mode of capillary electrochromatography for separation of ionic compounds driven by electrophoretic mobility on a neutrally hydrophobic monolithic column was developed. The monolithic column was prepared from the in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate to form a C12 hydrophobic stationary phase. It was found that EOF in this hydrophobic monolithic column was very poor, even the pH value of mobile phase at 8.0. The peptides at acidic buffer were separated on the basis of their differences in electrophoretic mobility and hydrophobic interaction with the stationary phase; therefore, different separation selectivity can be obtained in CEC from that in capillary zone electrophoresis (CZE). Separation of peptides has been realized with high column efficiency (up to 150,000 plates/meter) and good reproducibility (migration time with RSD <0.5%), and all of the peptides, including some basic peptides, showed good peak symmetry. Effects of the mobile phase compositions on the retention of peptides at low pH have been investigated in a hydrophobic capillary monolithic column. The significant difference in selectivity of peptides in CZE and CEC has been observed. Some peptide isomers that cannot be separated by CZE have been successfully separated on the capillary monolithic column in this mode with the same buffer used.

Biomedical ultrasound beam forming

The principles of biomedical ultrasound beam forming control the quality of diagnostic imaging. Beam parameters associated with imaging quality are: (1) lateral and axial resolutions; (2) depth of field; (3) contrast and (4) frame rate. In this paper, we review some of the current beam forming techniques and their principles. We focus on trade-offs among the above four aspects of beam forming and relate them to system parameters such as aperture size, f-number (the ratio between focal length and aperture diameter), central frequency (wavelength), system bandwidth and sidelobes. Methods for steering conventional and limited diffraction beams with array transducers are also reviewed.