Shear-induced unfolding activates von Willebrand factor A2 domain for proteolysis

BACKGROUND

To avoid pathological platelet aggregation by von Willebrand factor (VWF), VWF multimers are regulated in size and reactivity for adhesion by ADAMTS13-mediated proteolysis in a shear flow dependent manner.

OBJECTIVE AND METHODS

We examined whether tensile stress in VWF under shear flow activates the VWF A2 domain for cleavage by ADAMTS13 using molecular dynamics simulations. We generated a full length mutant VWF featuring a homologous disulfide bond in A2 (N1493C and C1670S), in an attempt to lock A2 against unfolding.

RESULTS

We indeed observed stepwise unfolding of A2 and exposure of its deeply buried ADAMTS13 cleavage site. Interestingly, disulfide bonds in the adjacent and highly homologous VWF A1 and A3 domains obstruct their mechanical unfolding. We find this mutant A2 (N1493C and C1670S) to feature ADAMTS13-resistant behavior in vitro.

CONCLUSIONS

Our results yield molecular-detail evidence for the force-sensing function of VWF A2, by revealing how tension in VWF due to shear flow selectively exposes the A2 proteolysis site to ADAMTS13 for cleavage while keeping the folded remainder of A2 intact and functional. We find the unconventional 'knotted' Rossmann fold of A2 to be the key to this mechanical response, tailored for regulating VWF size and activity. Based on our model we discuss the pathomechanism of some natural mutations in the VWF A2 domain that significantly increase the cleavage by ADAMTS13 without shearing or chemical denaturation, and provide with the cleavage-activated A2 conformation a structural basis for the design of inhibitors for VWF type 2 diseases.

JWA regulates melanoma metastasis by integrin alphaVbeta3 signaling

JWA, a newly identified novel microtubule-associated protein (MAP), was recently demonstrated to be indispensable for the rearrangement of actin cytoskeleton and activation of MAPK cascades induced by arsenic trioxide (As(2)O(3)) and phorbol ester (PMA). JWA depletion blocked the inhibitory effect of As(2)O(3) on HeLa cell migration, but enhanced cell migration after PMA treatment. As cancer cell migration is a hallmark of tumor metastasis and the functional role of JWA in cancer metastasis is not understood, here we show that JWA has an important role in melanoma metastasis. Our data demonstrated that JWA knockdown increased the adhesion and invasion abilities of melanoma cells. Furthermore, JWA knockdown in B16-F10 and A375 melanoma cells significantly promoted the formation and growth of metastatic colonies in vivo. Moreover, in the tumor biopsies from human melanoma patients, JWA expression was significantly decreased in malignant melanoma compared with normal nevi. In addition, we found that JWA knockdown could intensify tumor integrin alpha(V)beta(3) signaling by regulating nuclear factor Sp1. These findings suggest that JWA suppresses melanoma metastasis and may serve a potential therapeutic target for human melanoma.

Ferromagnetism in semihydrogenated graphene sheet

Single layer of graphite (graphene) was predicted and later experimentally confirmed to undergo metal-semiconductor transition when fully hydrogenated (graphane). Using density functional theory we show that when half of the hydrogen in this graphane sheet is removed, the resulting semihydrogenated graphene (which we refer to as graphone) becomes a ferromagnetic semiconductor with a small indirect gap. Half-hydrogenation breaks the delocalized pi bonding network of graphene, leaving the electrons in the unhydrogenated carbon atoms localized and unpaired. The magnetic moments at these sites couple ferromagnetically with an estimated Curie temperature between 278 and 417 K, giving rise to an infinite magnetic sheet with structural integrity and magnetic homogeneity. This is very different from the widely studied finite graphene nanostrucures such as one-dimensional nanoribbons and two-dimensional nanoholes, where zigzag edges are necessary for magnetism. From graphene to graphane and to graphone, the system evolves from metallic to semiconducting and from nonmagnetic to magnetic. Hydrogenation provides a novel way to tune the properties with unprecedented potentials for applications.

Growth of long range forward-backward multiplicity correlations with centrality in Au + Au collisions at square root of sNN = 200 GeV

Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au + Au and p + p collisions at square root of s(NN) = 200 GeV. Strong short- and long-range correlations (LRC) are seen in central Au + Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short-range correlations are observed in peripheral Au + Au collisions. Both the dual parton model (DPM) and the color glass condensate (CGC) predict the existence of the long-range correlations. In the DPM, the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC, longitudinal color flux tubes generate the LRC. The data are in qualitative agreement with the predictions of the DPM and indicate the presence of multiple parton interactions.

Regulation of glucose-6-phosphatase gene expression by insulin and metformin

The biguanide derivative metformin is a potent anti-diabetic drug widely used in the treatment of type 2 diabetes mellitus. Its major effect on glucose metabolism consists in the inhibition of hepatic glucose production. Since the mechanisms of metformin action are only partially understood at the molecular level, we studied the regulation of the gene promoter activity of glucose-6-phosphatase (G6Pase), the central hepatic gluconeogenic enzyme, by this drug. We have found that both metformin and insulin inhibit the basal and dexamethasone/cAMP-stimulated G6Pase promoter activity in hepatoma cells. Since one of the pharmacological targets of metformin is AMP-activated protein kinase (AMPK) and activation of AMPK is known to inhibit hepatic glucose production by the suppression of G6Pase gene transcription, we studied the effect of AMPK in this context. Under nonstimulated conditions, the inhibitory effect of both insulin and metformin was partially counteracted to a similar extent by treatment with compound C, a specific inhibitor of AMPK. In contrast, under conditions of stimulation with dexamethasone and cAMP, treatment with compound C reversed the inhibitory effect of metformin on G6Pase promoter activity to a similar extent as compared to nonstimulated conditions, whereas the effect of insulin was almost resistant to treatment with the AMPK-antagonist. These data indicate a differential AMPK-dependent regulation of G6Pase gene expression by insulin and metformin under basal and dexamethasone/cAMP-stimulated conditions.

Biphasic effects of dexamethasone on glycogen metabolism in primary cultured rat hepatocytes

Glucocorticoids (GC), the basic function of which is modulating carbohydrates metabolism, play a critical role in stress response by enhancing the organism's resistance. It is widely believed that they could promote glycogen synthesis. However, it is doubtful whether GC can still stimulate glycogen deposition in stress response, as it is known that glucose is imperatively needed at that time. Here, we used primary cultured rat hepatocytes to investigate the effects of GC on glycogen metabolism in vitro to exclude other influences in stress. The results showed that dexamethasone (Dex) played biphasic effects on hepatocytes glycogen metabolism depending on its dosage and the duration of stimulation. Dex could decrease glycogen content of hepatocytes in the higher concentration within a relatively shorter period of time, which could not be blocked by cycloheximide. Therefore, dual roles in hepatic glycogen metabolism played by GC were demonstrated, and a non-genomic mechanism might be involved in the glycogenolytic action of GC. We postulated that the biphasic effects of GC on hepatic glycogen metabolism might be of important significance in stress response.

Repulsive Casimir force in chiral metamaterials

We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.

K/pi Fluctuations at relativistic energies

We report K/pi fluctuations from Au + Au collisions at sqrt[s(NN)]= 19.6, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. K/pi fluctuations in central collisions show little dependence on incident energy and are on the same order as those from NA49 at the Super Proton Synchrotron in central Pb + Pb collisions at sqrt[s(NN)]=12.3 and 17.3 GeV. We report results for the collision centrality dependence of K/pi fluctuations and results for charge-separated fluctuations. We observe that the K/pi fluctuations scale with the charged particle multiplicity density.

Strong optical activity from twisted-cross photonic metamaterials

Following a recent theoretical suggestion and microwave experiments, we fabricate photonic metamaterials composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. The resulting two effective resonances of the coupled system lie in the 1-2 microm wavelength regime and exhibit pronounced circular dichroism, while the circular polarization conversion is very small. In between the two resonances, we find a fairly broad spectral regime with strong optical activity, i.e., with a pure rotation of incident linear polarization. The measured optical transmittance spectra agree well with theory.

Genetic analysis of familial non-syndromic primary failure of eruption

OBJECTIVES

While some eruption disorders occur as part of a medical syndrome, primary failure of eruption (PFE) - defined as a localized failure of secondary tooth eruption - exists without systemic involvement. Recent studies support that heredity may play an important role in the pathogenesis of PFE. The objective of our human genetic study is to investigate the genetic contribution to PFE.

MATERIALS AND METHODS

Four candidate genes POSTN, RUNX2, AMELX, and AMBN) were investigated because of their relationship to tooth eruption or putative relationship to each other. Families and individuals were ascertained based on the clinical diagnosis of PFE. Pedigrees were constructed and analyzed by inspection to determine the mode of inheritance in four families. The candidate genes were directly sequenced for both unrelated affected individuals and unaffected individuals. A genome wide scan using 500 microsatellite markers followed by linkage analysis was carried out for one family.

RESULTS

Pedigree analysis of families suggests an autosomal dominant inheritance pattern with complete penetrance and variable expressivity. Sequence analysis revealed two non-functional polymorphisms in the POSTN gene and no other sequence variations in the remaining candidate genes. Genotyping and linkage analysis of one family yielded a LOD score of 1.51 for markers D13S272; D15S118 and D17S831 on chromosomes 13, 15 and 17 respectively.

CONCLUSIONS

While LOD scores were not significant evidence of linkage, extension of current pedigrees and novel SNP chip technology holds great promise for identification of a causative locus for PFE.

Anti‐inflammatory and anti‐oxidative effects of cherries on Freund's adjuvant‐induced arthritis in rats

OBJECTIVES

To investigate the anti-inflammatory and anti-oxidative effects of anthocyanins from cherries on Freund's adjuvant-induced arthritis (AIA) in rats.

METHODS

Arthritis was induced intradermally by injection with 0.1 mL of complete Freund's adjuvant (CFA) into the right hind footpad of male Sprague Dawley (SD) rats. Anthocyanins at 40, 20 and 10 mg/kg (body weight) were administered orally to the treated rats for 28 days after the injection. Tumour necrosis factor-alpha (TNFalpha) in serum and prostaglandin E2 (PGE2) in paws were assayed by radioimmunoassay (RIA), and anti-oxidative effects was assayed by measuring total anti-oxidative capacity (T-AOC), superoxide dismutase (SOD) and malondialdehyde (MDA) in serum.

RESULTS

Anthocyanins at 40 mg/kg significantly decreased the levels of TNFalpha in serum and PGE2 in paws, simultaneously improving the anti-oxidative status of AIA. We found that at this dosage T-AOC was potentized, the activity of SOD increased and the level of MDA in serum decreased. However, anthocyanins at 20 and 10 mg/kg had less effect on the inflammatory factors and anti-oxidative capacity of AIA.

CONCLUSIONS

Anthocyanins have potential anti-inflammatory and anti-oxidative effects on AIA.

Deferred modification of antiretroviral regimen following documented treatment failure in Asia: results from the TREAT Asia HIV Observational Database (TAHOD)

OBJECTIVE

The aim of the study was to examine the rates and predictors of treatment modification following combination antiretroviral therapy (cART) failure in Asian patients with HIV enrolled in the TREAT Asia HIV Observational Database (TAHOD).

METHODS

Treatment failure (immunological, virological and clinical) was defined by World Health Organization criteria. Countries were categorized as high or low income by World Bank criteria.

RESULTS

Among 2446 patients who initiated cART, 447 were documented to have developed treatment failure over 5697 person-years (7.8 per 100 person-years). A total of 253 patients changed at least one drug after failure (51.6 per 100 person-years). There was no difference between patients from high- and low-income countries [adjusted hazard ratio (HR) 1.02; P=0.891]. Advanced disease stage [Centers for Disease Control and Prevention (CDC) category C vs. A; adjusted HR 1.38, P=0.040], a lower CD4 count (>or=51 cells/microL vs. <or=50 cells/microL; adjusted HR 0.61, P=0.022) and a higher HIV viral load (>or=400 HIV-1 RNA copies/mL vs. <400 copies/mL; adjusted HR 2.69, P<0.001) were associated with a higher rate of treatment modification after failure. Compared with patients from low-income countries, patients from high-income countries were more likely to change two or more drugs (67%vs. 49%; P=0.009) and to change to a protease-inhibitor-containing regimen (48%vs. 16%; P<0.001).

CONCLUSIONS

In a cohort of Asian patients with HIV infection, nearly half remained on the failing regimen in the first year following documented treatment failure. This deferred modification is likely to have negative implications for accumulation of drug resistance and response to second-line treatment. There is a need to scale up the availability of second-line regimens and virological monitoring in this region.