The influence of polystyrene nanoparticles on the fractal kinetics of lactate dehydrogenase

Plastics are ubiquitous in the aquatic environment and their degradation of fragments down to the nanoscale level have raised concerns given their ability to pervade cells. The accumulation of nanoparticles could lead to molecular crowding which can alter the normal functioning of enzymes. The purpose of this study was to examine the influence of polystyrene nanoparticles (NPs) on the fractal kinetics of the lactate dehydrogenase reaction: pyruvate + NADH ? lactate + NAD⁺. The influence of NPs on LDH activity was examined first in vitro to highlight specific effects and secondly in mussels exposed to NPs in vivo for 24h at 15 °C. The reaction rates of LDH were determined with increasing concentrations of pyruvate to reach saturation at circa 1 mM pyruvate. The addition of F-actin, a known binding template for LDH, revealed a characteristic change in reaction rates associated with fractal organization. The addition of 50 and 100 nm transparent NPs also produced these changes. The fractal dimension was determined and revealed that both F-actin and NPs reduced the fractal dimension of the LDH reaction. The addition of viscosity sensor probe in the reaction media revealed viscosity waves during the reaction at low substrate concentrations thought to be associated to synchronized switching between the relaxed and tensed states of LDH. The amplitude and the frequency of viscosity waves were increased by both NPs and F-actin which were associated with increased reaction rates. In mussels exposed to NPs, the isolation of digestive gland subcellular fraction revealed that LDH activity was significantly influenced by the fractal dimension of the LDH reaction where a loss of affinity (high fractal K_M) was detected in mussels exposed to the high concentrations of NPs. It is concluded that polystyrene NPs could change the biophysical properties of the cytoplasm such as the fractal organization of the intracellular environment during the LDH reaction.     

Bioengineering potato plants to produce benzylglucosinolate for improved broad-spectrum pest and disease resistance

Transgenic Research - In traditional, small-scale agriculture in the Andes, potatoes are frequently co-cultivated with the Andean edible tuber Tropaeolum tuberosum, commonly known as mashua, which...     

PIK3R1 Mutations Cause Syndromic Insulin Resistance with Lipoatrophy

Short stature, hyperextensibility of joints and/or inguinal hernia, ocular depression, Rieger anomaly, and teething delay (SHORT) syndrome is a developmental disorder with an unknown genetic cause and hallmarks that include insulin resistance and lack of subcutaneous fat. We ascertained two unrelated individuals with SHORT syndrome, hypothesized that the observed phenotype was most likely due to de novo mutations in the same gene, and performed whole-exome sequencing in the two probands and their unaffected parents. We then confirmed our initial observations in four other subjects with SHORT syndrome from three families, as well as 14 unrelated subjects presenting with syndromic insulin resistance and/or generalized lipoatrophy associated with dysmorphic features and growth retardation. Overall, we identified in nine affected individuals from eight families de novo or inherited PIK3R1 mutations, including a mutational hotspot (c.1945C>T [p.Arg649Trp]) present in four families. PIK3R1 encodes the p85α, p55α, and p50α regulatory subunits of class IA phosphatidylinositol 3 kinases (PI3Ks), which are known to play a key role in insulin signaling. Functional data from fibroblasts derived from individuals with PIK3R1 mutations showed severe insulin resistance for both proximal and distal PI3K-dependent signaling. Our findings extend the genetic causes of severe insulin-resistance syndromes and provide important information with respect to the function of PIK3R1 in normal development and its role in human diseases, including growth delay, Rieger anomaly and other ocular affections, insulin resistance, diabetes, paucity of fat, and ovarian cysts.     

EDTA/gelatin zymography method to identify C1s versus activated MMP‐9 in plasma and immune complexes of patients with systemic lupus erythematosus

Gelatin zymography analysis is a sensitive method and commonly used to characterize and quantify the presence of the gelatinases (MMP‐2 and MMP‐9) in biological samples. In human plasma samples from healthy controls and systemic lupus erythematosus (SLE) patients, we observed a gelatinolytic molecule at 80 kDa, suggestive for activated human MMP‐9. However, by developing and using the EDTA/gelatin zymography method and after purification of the 80 kDa entity, we proved that this molecule was the C1s subunit of the complement system. The zymolytic capacity of C1s was validated and found to be enhanced, in the absence of calcium and in the presence of EDTA. Our findings indicate that for correct identification of gelatinolytic proteins in complex biological samples the use of EDTA/gelatin zymography for enzyme development is advised. In addition, by quantification of EDTA/gelatin zymography analysis and ELISA, we observed that the levels of C1s were higher in plasma and immune complexes of SLE patients than of healthy individuals. Therefore, our data imply that C1s may become a marker for the diagnosis of SLE.     

MCC, a new interacting protein for Scrib, is required for cell migration in epithelial cells

To further characterize the molecular events supporting the tumor suppressor activity of Scrib in mammals, we aim to identify new binding partners. We isolated MCC, a recently identified binding partner for β-catenin, as a new interacting protein for Scrib. MCC interacts with both Scrib and the NHERF1/NHERF2/Ezrin complex in a PDZ-dependent manner. In T47D cells, MCC and Scrib proteins colocalize at the cell membrane and reduced expression of MCC results in impaired cell migration. By contrast to Scrib, MCC inhibits cell directed migration independently of Rac1, Cdc42 and PAK activation. Altogether, these results identify MCC as a potential scaffold protein regulating cell movement and able to bind Scrib, β-catenin and NHERF1/2.

Structured summary

MINT-7211022: SCRIB (uniprotkb:Q14160) and MCC (uniprotkb:P23508) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7210609: SCRIB (uniprotkb:Q14160) physically interacts (MI:0915) with MCC (uniprotkb:P23508) by two hybrid (MI:0018)MINT-7210759, MINT-7210792: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with PIX beta (uniprotkb:Q14155) by pull down (MI:0096)MINT-7210883, MINT-7210820: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with MCC (uniprotkb:P23508) by anti bait coimmunoprecipitation (MI:0006)MINT-7210634, MINT-7210690, MINT-7210731: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with MCC (uniprotkb:P23508) by pull down (MI:0096)MINT-7211267: E6 (uniprotkb:P06463) physically interacts (MI:0915) with SCRIB (uniprotkb:Q14160), SNX27 (uniprotkb:Q96L92), UTRN (uniprotkb:P46939), CASK (uniprotkb:O14936), DMD (uniprotkb:P11532) and Dlg (uniprotkb:Q12959) by pull down (MI:0096)MINT-7211237: MCC (uniprotkb:P23508) physically interacts (MI:0915) with SCRIB (uniprotkb:Q14160), EZR (uniprotkb:P15311), SNX27 (uniprotkb:Q96L92), NHERF1 (uniprotkb:O14745) and NHERF2 (uniprotkb:Q15599) by pull down (MI:0096)     

Relationship between Vitreous Levels of Matrix Metalloproteinases and Vascular Endothelial Growth Factor in Proliferative Diabetic Retinopathy

To investigate which matrix metalloproteinases (MMPs) are more likely to be involved in the angiogenic process in proliferative diabetic retinopathy (PDR), we measured the levels of MMPs in the vitreous fluid from patients with PDR and controls and correlated these levels with the levels of vascular endothelial growth factor (VEGF). Vitreous samples from 32 PDR and 24 nondiabetic patients were studied by mosaic multiplex MMPs enzyme-linked immunosorbent assay (ELISA), single ELISA, Western blot and zymography analysis. Epiretinal membranes from 11 patients with PDR were studied by immunohistochemistry. MMP-8 and MMP-13 were not detected. ELISA, Western blot and gelatin ymography assays revealed significant increases in the expression levels of MMP-1, MMP-7, MMP-9 and VEGF in vitreous samples from PDR patients compared to nondiabetic controls, whereas MMP-2 and MMP-3 were not upregulated in vitreous samples from PDR patients. Significant correlations existed between ELISA and zymography assays for the quantitation of MMP-2 (r=0.407; p=0.039) and MMP-9 (r=0.711; p<0.001). Significant correlations were observed between levels of VEGF and levels of MMP-1 (r=0.845; P<0.001) and MMP-9 (r=0.775; p<0.001), and between levels of MMP-1 and MMP-9 (r=0.857; p<0.001). In epiretinal membranes, cytoplasmic immunoreactivity for MMP-9 was present in vascular endothelial cells and stromal monocytes/macrophages and neutrophils. Our findings suggest that among the MMPs measured, MMP-1 and MMP-9 may contribute to the angiogenic switch in PDR.     

Natural Haemozoin Induces Expression and Release of Human Monocyte Tissue Inhibitor of Metalloproteinase-1

Recently matrix metalloproteinase-9 (MMP-9) and its endogenous inhibitor (tissue inhibitor of metalloproteinase-1, TIMP-1) have been implicated in complicated malaria. In vivo, mice with cerebral malaria (CM) display high levels of both MMP-9 and TIMP-1, and in human patients TIMP-1 serum levels directly correlate with disease severity. In vitro, natural haemozoin (nHZ, malarial pigment) enhances monocyte MMP-9 expression and release. The present study analyses the effects of nHZ on TIMP-1 regulation in human adherent monocytes. nHZ induced TIMP-1 mRNA expression and protein release, and promoted TNF-α, IL-1β, and MIP-1α/CCL3 production. Blocking antibodies or recombinant cytokines abrogated or mimicked nHZ effects on TIMP-1, respectively. p38 MAPK and NF-κB inhibitors blocked all nHZ effects on TIMP-1 and pro-inflammatory molecules. Still, total gelatinolytic activity was enhanced by nHZ despite TIMP-1 induction. Collectively, these data indicate that nHZ induces inflammation-mediated expression and release of human monocyte TIMP-1 through p38 MAPK- and NF-κB-dependent mechanisms. However, TIMP-1 induction is not sufficient to counterbalance nHZ-dependent MMP-9 enhancement. Future investigation on proteinase-independent functions of TIMP-1 (i.e. cell survival promotion and growth/differentiation inhibition) is needed to clarify the role of TIMP-1 in malaria pathogenesis.     

The role of arginine methylation in the DNA damage response

Post-translational modifications are well-known modulators of DNA damage signaling and epigenetic gene expression. Protein arginine methylation is a covalent modification that results in the addition of methyl groups to the nitrogen atoms of the arginine side chains and is catalyzed by a family of protein arginine methyltransferases (PRMTs). In the past, arginine methylation was mainly observed on abundant proteins such as RNA-binding proteins and histones, but recent advances have revealed a plethora of arginine methylated proteins implicated in a variety of cellular processes including RNA metabolism, epigenetic regulation and DNA repair pathways. Herein, we discuss these recent advances, focusing on the role of PRMTs in DNA damage signaling and its importance for maintaining genomic stability.     

Gelatin degradation assay reveals MMP-9 inhibitors and function of O-glycosylated domain

AIM: To establish a novel, sensitive and high-throughput gelatinolytic assay to define new inhibitors and compare domain deletion mutants of gelatinase B/matrix metalloproteinase (MMP)-9. METHODS: Fluorogenic Dye-quenched (DQ)TM-gelatin was used as a substrate and biochemical parameters (substrate and enzyme concentrations, DMSO solvent concentrations) were optimized to establish a highthroughput assay system. Various small-sized libraries (ChemDiv, InterBioScreen and ChemBridge) of hetero-cyclic, drug-like substances were tested and compared with prototypic inhibitors. RESULTS: First, we designed a test system with gelatin as a natural substrate. Second, the assay was validated by selecting a novel pyrimidine-2,4,6-trione (barbitu- rate) inhibitor. Third, and in line with present structural data on collagenolysis, it was found that deletion of the O-glycosylated region significantly decreased gelatinolytic activity (kcat/kM ± 40% less than full-length MMP-9). CONCLUSION: The DQTM-gelatin assay is useful in high-throughput drug screening and exosite targeting. We demonstrate that flexibility between the catalytic and hemopexin domain is functionally critical for gelatinolysis.