Analysis of the minimal specificity of caspase-2 and identification of Ac-VDTTD-AFC as a caspase-2-selective peptide substrate.

Caspase-2 is an evolutionarily conserved but enigmatic protease whose biological role remains poorly understood. To date, research into the functions of caspase-2 has been hampered by an absence of reagents that can distinguish its activity from that of the downstream apoptotic caspase, caspase-3. Identification of protein substrates of caspase-2 that are efficiently cleaved within cells may also provide clues to the role of this protease. We used a yeast-based transcriptional reporter system to define the minimal substrate specificity of caspase-2. The resulting profile enabled the identification of candidate novel caspase-2 substrates. Caspase-2 cleaved one of these proteins, the cancer-associated transcription factor Runx1, although with relatively low efficiency. A fluorogenic peptide was derived from the sequence most efficiently cleaved in the context of the transcriptional reporter. This peptide, Ac-VDTTD-AFC, was efficiently cleaved by purified caspase-2 and auto-activating caspase-2 in mammalian cells, and exhibited better selectivity for caspase-2 relative to caspase-3 than reagents that are currently available. We suggest that this reagent, used in parallel with the traditional caspase-3 substrate Ac-DEVD-AFC, will enable researchers to monitor caspase-2 activity in cell lysates and may assist in the determination of stimuli that activate caspase-2 in vivo.

Amyloid fibrils as a nanoscaffold for enzyme immobilization.

Amyloid fibrils are a misfolded state, formed by many proteins when subjected to denaturing conditions. Their constituent amino acids make them ideally suited as a readily functionalized nanoscaffold for enzyme immobilization and their strength, stability, and nanometer size are attractive features for exploitation in the creation of new bionanomaterials. We report successful functionalization of amyloid fibrils by conjugation to glucose oxidase (GOD) using glutaraldehyde. GOD retained activity upon attachment and successful cross-linking was determined using electrophoresis, centrifugation, sucrose gradient centrifugation, and TEM. The resulting functionalized enzyme scaffold was then incorporated into a model poly(vinyl alcohol) (PVOH) film, to create a new bionanomaterial. The antibacterial effect of the functionalized film was then tested on E. coli, the growth of which was inhibited, demonstrating the incorporation of GOD antibacterial activity into the PVOH film. The incorporation of the GOD-functionalized amyloid fibrils into PVOH provides an excellent 'proof of concept' model for the creation of a new bionanomaterial using a functionalized amyloid fibril scaffold.

NO modulates NADPH oxidase function via heme oxygenase-1 in human endothelial cells.

NO is known to induce expression of heme oxygenase-1, an antioxidant enzyme in blood vessels. We tested whether NO might modulate the endothelial NADPH oxidase function via heme oxygenase-1. In human microvascular endothelial cells, the NO donor DETA-NONOate (0.1 to 1 mmol/L) strongly induced expression of heme oxygenase-1 but not Cu/Zn superoxide dismutase. This was associated with a reduction of the superoxide-generating capacity of NADPH oxidase, an effect that depended on de novo gene transcription and heme oxygenase-1 activity. Activation of NADPH oxidase by tumor necrosis factor (TNF) alpha increased generation of reactive oxygen species. DETA-NONOate alone had little effect on TNF-stimulated reactive oxygen species, but it enhanced the TNF response when: (1) heme oxygenase-1 expression was blocked with specific small-interfering RNA; (2) heme oxygenase-1 activity was blocked by zinc-protoporphyrin; or (3) NADPH oxidase activity was blocked by diphenyleneiodonium. Moreover, the heme oxygenase-1 end product bilirubin directly inhibited fully functional NADPH oxidase and seemed to interrupt the assembly and activation of the oxidase. In conclusion, NO may modulate superoxide production by NADPH oxidase in human vascular endothelial cells, at least partly by inducing heme oxygenase-1. Our results indicate that suppression of NADPH oxidase-dependent reactive oxygen species formation may represent a novel mechanism underlying the cardiovascular protective actions of heme oxygenase-1 and bilirubin.

In vivo clearance of human protein S in a mouse model: influence of C4b-binding protein and the Heerlen polymorphism.

OBJECTIVE: To explore the effect of the Heerlen polymorphism and C4b-binding protein (C4BP) on protein S catabolism in vitro and in vivo. METHODS AND RESULTS: Radiolabeled protein S was efficiently bound and intracellularly degraded by THP-1 macrophages, and both processes were strongly reduced in the presence of the protein S-carrier protein C4BP. To test whether C4BP displays a similar protective effect in vivo, survival experiments were performed in mice. In the absence of C4BP, radiolabeled human protein S disappeared in a biphasic manner (mean residence time [MRT] 2 hours). However, the presence of C4BP resulted in a 4-fold prolonged survival of protein S (MRT 8 hours; P<0.0001). We also applied this experimental model to recombinant protein S-Heerlen, a naturally occurring variant that contains a Ser460Pro substitution. These clearance experiments revealed a strongly decreased survival of recombinant protein S-S460P (MRT 0.6 hours; P=0.021), which could be compensated partially by C4BP (MRT 1.4 hours; P=0.012 compared with protein S-S460P). CONCLUSIONS: Protein S-S460P has a reduced survival in vivo, which may explain the low levels of free protein S in individuals carrying this polymorphism. Furthermore, C4BP prevents premature clearance of protein S and uses this ability to compensate the increased clearance of protein S-S460P.

Dihydrodipicolinate synthase (DHDPS) from Escherichia coli displays partial mixed inhibition with respect to its first substrate, pyruvate.

Dihydrodipicolinate synthase (DHDPS, E.C. 4.2.1.52) mediates the first unique reaction of (S)-lysine biosynthesis in plants and microbes-the condensation of (S)-aspartate-beta-semialdehyde ((S)-ASA) and pyruvate. It has been shown that DHDPS is partially feedback inhibited by (S)-lysine; it is suggested that this mechanism regulates flux through the DAP biosynthetic pathway. Others have characterised DHDPS from Escherichia coli with respect to (S)-lysine inhibition. They have concluded that, with respect to pyruvate, the first substrate of the reaction, DHDPS shows uncompetitive inhibition: as such, they further suggest that (S)-lysine inhibits DHDPS via interaction with the binding site for the second substrate, (S)-ASA. Yet, this finding is based on the assumption that (S)-lysine is a fully uncompetitive inhibitor. In light of crystallographic studies, which lead to the proposal that (S)-lysine affects the putative proton-relay of DHDPS, we re-evaluated the inhibition mechanism of DHDPS with respect to (S)-lysine by incorporating the observed hyperbolic inhibition. Our data showed that lysine is not an uncompetitive inhibitor, but a mixed inhibitor when pyruvate and (S)-lysine concentrations were varied. Thus, consistent with the crystallographic data, (S)-lysine must have an effect on the initial steps of the DHDPS reaction, including the binding of pyruvate and Schiff base formation.

Genetic variation in dopaminergic pathways and short-term effectiveness of the nicotine patch.

Polymorphisms in the dopamine D2 receptor (DRD2 C/T and DRD2 A/G) and in dopamine beta hydroxylase (DBH A/G) have been implicated in modulation of smoking and other reward-seeking behaviours. We hypothesized that these alleles would predict the outcome of nicotine patch therapy for smoking cessation. In 1991-93, we performed a randomized controlled trial of the nicotine patch on 1686 heavy smokers (> or = 15 cigarettes/day). In 1999-2000, we contacted 1532 of the 1612 subjects still available; 767 (50%) completed a questionnaire and gave a blood sample. In the 755 cases in which DNA was successfully genotyped, we examined associations between the polymorphisms in DRD2 and DBH, and smoking cessation. At 1 week, the patch was more effective for smokers with DRD2 CT/TT genotype [patch/placebo odds ratio (OR) 2.8, 95% confidence interval (CI) 1.7-4.6] than with CC (OR 1.4, 0.9-2.1; P for difference in ORs 0.04). Smokers with both DRD2 CT/TT and DBH GA/AA genotypes had an OR of 3.6 (2.0-6.5) compared to 1.4 (1.0-2.1) for others (P = 0.01). At 12 weeks, the ORs for these genotypic groups were 3.6 (1.7-7.8) and 1.4 (0.9-2.3), respectively (P = 0.04). There was no association between patch effectiveness and DRD2 exon 8. Short-term effectiveness of the nicotine patch may be related to dopamine beta-hydroxylase and dopamine D2 receptor genotype. Our results support the need for further investigation into personalized therapies for smoking cessation based on individual genotype.

MARSSIM vs. DOE Order 5400.5: the Final Status Survey plan at the Rocky Flats Environmental Technology Site.

A challenge unique to the decommissioning of Department of Energy (DOE) facilities involves the compromise between the existing and newly recommended standards for the unrestricted release of property and materials. The Rocky Flats Environmental Technology Site (RFETS) is currently decommissioning numerous plutonium contaminated facilities. The default DOE standard for unrestricted release, Order 5400.5, defines surface activity guidelines as averaged over a 1-square-meter area with a maximum value defined for any given 100-square-centimeter area. While the Order was initially developed to release property and materials from an operating site, it is restrictive in its use when performing Final Status Survey and, to date, no new complex wide standard has been developed. However, the RFETS stakeholders selected the MARSSIM, which provides a progressive method to demonstrate compliance with the defined "dose-based" limits for a specific site, as the governing document in developing a final survey method. The end result is a hybrid final status survey plan that incorporates the requirements of both documents. This plan represents several years of development and negotiation between the contractor, the DOE, the Colorado Department of Public Health and Environment, the Rocky Flats stakeholders, and other interested parties.

The preparation of (S)-aspartate semi-aldehyde appropriate for use in biochemical studies.

We report two three-step syntheses of (S)-aspartate semi-aldehyde, an important synthetic and biosynthetic precursor, from diprotected aspartic acid. The first synthesis proceeds via a thioester, the second via a Weinreb amide. Each route yields pure (S)-aspartate semi-aldehyde in excellent yield. (S)-Aspartate semi-aldehyde prepared in this manner has proved appropriate as a substrate for detailed enzyme studies.