The regulation of necroptosis by ubiquitylation

Necroptosis is a programmed necrosis that is mediated by receptor-interacting protein kinases RIPK1, RIPK3 and the mixed lineage kinase domain-like protein, MLKL. Necroptosis must be strictly regulated to maintain normal tissue homeostasis, and dysregulation of necroptosis leads to the development of various inflammatory, infectious, and degenerative diseases. Ubiquitylation is a widespread post-translational modification that is essential for balancing numerous physiological processes. Over the past decade, considerable progress has been made in the understanding of the role of ubiquitylation in regulating necroptosis. Here, we will discuss the regulatory functions of ubiquitylation in necroptosis signaling pathway. An enhanced understanding of the ubiquitylation enzymes and regulatory proteins in necroptotic signaling pathway will be exploited for the development of new therapeutic strategies for necroptosis-related diseases.

     

Warsaw Breakage Syndrome, a Cohesinopathy Associated with Mutations in the XPD Helicase Family Member DDX11/ChlR1

The iron-sulfur-containing DNA helicases XPD, FANCJ, DDX11, and RTEL represent a small subclass of superfamily 2 helicases. XPD and FANCJ have been connected to the genetic instability syndromes xeroderma pigmentosum and Fanconi anemia. Here, we report a human individual with biallelic mutations in DDX11. Defective DDX11 is associated with a unique cellular phenotype in which features of Fanconi anemia (drug-induced chromosomal breakage) and Roberts syndrome (sister chromatid cohesion defects) coexist. The DDX11-deficient patient represents another cohesinopathy, besides Cornelia de Lange syndrome and Roberts syndrome, and shows that DDX11 functions at the interface between DNA repair and sister chromatid cohesion.     

Testicular morphology and expression of aromatase in testes of mice with the mosaic mutation (Atp7a mo-ms)

The aim of this study was to determine whether testicular cells of mice with the mosaic mutation, associated with abnormal copper metabolism, are able to aromatize androgens to estrogens, and what is the putative role of estrogens in the gonad of the mutant male. Mosaic is a lethal mutation; affected males usually die on about day 16. Those, which survive to reach sexual maturity, are valuable research subjects. In testes of young and adult mutants, histological analysis revealed the presence of many degenerating seminiferous tubules besides normal-looking ones. Additionally, high numbers of apoptotic germ cells were observed, especially in young mutants when compared with the controls. Positive immunostaining for aromatase was found in cultured Leydig cells and testicular sections of both control and mutant males. The intensity of immunostaining was always stronger in the mosaic mice. In both groups, Western-blot analysis revealed the presence of aromatase protein as a single band of approximately 55 kDa. In the mosaic males, levels of testosterone in cultured Leydig cells, whole testes, and in blood plasma were lower than in those of the respective controls. On the contrary, estradiol concentrations were always higher in the mutants. Both in vivo and in vitro studies indicate that morphological and functional changes in the testes of the mosaic mice mainly result from defective copper metabolism. The higher level of endogenous estrogens can additionally enhance morphological alterations within the testes. It seems also likely that excess estrogens may affect the survival rate of the mosaic males.     

Novel Inhibitors of Staphylococcus aureus Virulence Gene Expression and Biofilm Formation

Staphylococcus aureus is a major human pathogen and one of the more prominent pathogens causing biofilm related infections in clinic. Antibiotic resistance in S. aureus such as methicillin resistance is approaching an epidemic level. Antibiotic resistance is widespread among major human pathogens and poses a serious problem for public health. Conventional antibiotics are either bacteriostatic or bacteriocidal, leading to strong selection for antibiotic resistant pathogens. An alternative approach of inhibiting pathogen virulence without inhibiting bacterial growth may minimize the selection pressure for resistance. In previous studies, we identified a chemical series of low molecular weight compounds capable of inhibiting group A streptococcus virulence following this alternative anti-microbial approach. In the current study, we demonstrated that two analogs of this class of novel anti-virulence compounds also inhibited virulence gene expression of S. aureus and exhibited an inhibitory effect on S. aureus biofilm formation. This class of anti-virulence compounds could be a starting point for development of novel anti-microbial agents against S. aureus.     

Endemic Foci of the Tick-Borne Relapsing Fever Spirochete Borrelia crocidurae in Mali,West Africa,and the Potential for Human Infection

Background

Tick-borne relapsing fever spirochetes are maintained in endemic foci that involve a diversity of small mammals and argasid ticks in the genus Ornithodoros. Most epidemiological studies of tick-borne relapsing fever in West Africa caused by Borrelia crocidurae have been conducted in Senegal. The risk for humans to acquire relapsing fever in Mali is uncertain, as only a few human cases have been identified. Given the high incidence of malaria in Mali, and the potential to confuse the clinical diagnosis of these two diseases, we initiated studies to determine if there were endemic foci of relapsing fever spirochetes that could pose a risk for human infection.

Methodology/Principal Findings

We investigated 20 villages across southern Mali for the presence of relapsing fever spirochetes. Small mammals were captured, thin blood smears were examined microscopically for spirochetes, and serum samples were tested for antibodies to relapsing fever spirochetes. Ornithodoros sonrai ticks were collected and examined for spirochetal infection. In total, 11.0% of the 663 rodents and 14.3% of the 63 shrews tested were seropositive and 2.2% of the animals had active spirochete infections when captured. In the Bandiagara region, the prevalence of infection was higher with 35% of the animals seropositive and 10% infected. Here also Ornithodoros sonrai were abundant and 17.3% of 278 individual ticks tested were infected with Borrelia crocidurae. Fifteen isolates of B. crocidurae were established and characterized by multi-locus sequence typing.

Conclusions/Significance

The potential for human tick-borne relapsing fever exists in many areas of southern Mali.     

Role of the Actin Ala-108–Pro-112 Loop in Actin Polymerization and ATPase Activities

Actin plays fundamental roles in a variety of cell functions in eukaryotic cells. The polymerization-depolymerization cycle, between monomeric G-actin and fibrous F-actin, drives essential cell processes. Recently, we proposed the atomic model for the F-actin structure and found that actin was in the twisted form in the monomer and in the untwisted form in the filament. To understand how the polymerization process is regulated (Caspar, D. L. (1991) Curr. Biol. 1, 30–32), we need to know further details about the transition from the twisted to the untwisted form. For this purpose, we focused our attention on the Ala-108–Pro-112 loop, which must play crucial roles in the transition, and analyzed the consequences of the amino acid replacements on the polymerization process. As compared with the wild type, the polymerization of P109A was accelerated in both the nucleation and the elongation steps, and this was attributed to an increase in the frequency factor of the Arrhenius equation. The multiple conformations allowed by the substitution presumably resulted in the effective formation of the collision complex, thus accelerating polymerization. On the other hand, the A108G mutation reduced the rates of both nucleation and elongation due to an increase in the activation energy. In the cases of polymerization acceleration and deceleration, each functional aberration is attributed to a distinct elementary process. The rigidity of the loop, which mediates neither too strong nor too weak interactions between subdomains 1 and 3, might play crucial roles in actin polymerization.     

Functional assessment of cryopreserved pig aortas for pharmaceutical research

Several in vitro studies have demonstrated diminished post-thaw functional activity. Therefore, the aim of this study was to investigate the consequences of thawing and storage method used on the post-thaw functional activity of cryopreserved pig aortas with the aim of adjusting the freezing and thawing protocol so that the vascular segments are preserved in the best possible state, maintaining structure and functionality so that they can later be transplanted with success. In vitro responses of frozen, thawed pig aortas were used to investigate the functional activity after thawing at 15 degrees C and 100 degrees C/min and after storage in gas or liquid phase of liquid nitrogen. Cryopreservation was performed in RPMI 1640 medium + 10% dimethylsulfoxide and the rate of cooling was -1 degrees C/min, until -150 degrees C was reached.After thawing the maximal contractile responses to all the contracting agonists tested (KCl, noradrenaline) were in the ranges of 13-27% compared with the responses in unfrozen pig aortas. Contractile responses were slightly better when thawing was performed at 15 degrees C/min compared with 100 degrees C/min. The endothelium independent relaxant responses to sodium nitroprusside were reduced ( P < 0.05). Cryostorage of pig arteries also resulted in a loss of the endothelium-dependent relaxant response to acetylcholine. The cryopreservation method used provided a limited preservation of pig aorta contractibility, a reduction of the endothelium independent relaxant responses, and no apparent preservation of the endothelium-dependent relaxation. It is possible that further refinements of the cryopreservation protocol might allow better post-thaw functional recovery of pig aortas.     

Aspergillus niger DLFCC-90 rhamnoside hydrolase, a new type of flavonoid glycoside hydrolase

A novel rutin-α-L-rhamnosidase hydrolyzing α-L-rhamnoside of rutin, naringin, and hesperidin was purified and characterized from Aspergillus niger DLFCC-90, and the gene encoding this enzyme, which is highly homologous to the α-amylase gene, was cloned and expressed in Pichia pastoris GS115. The novel enzyme was classified in glycoside-hydrolase (GH) family 13.     

Impact of treadmill running and sex on hippocampal neurogenesis in the mouse model of amyotrophic lateral sclerosis

Hippocampal neurogenesis in the subgranular zone (SGZ) of dentate gyrus (DG) occurs throughout life and is regulated by pathological and physiological processes. The role of oxidative stress in hippocampal neurogenesis and its response to exercise or neurodegenerative diseases remains controversial. The present study was designed to investigate the impact of oxidative stress, treadmill exercise and sex on hippocampal neurogenesis in a murine model of heightened oxidative stress (G93A mice). G93A and wild type (WT) mice were randomized to a treadmill running (EX) or a sedentary (SED) group for 1 or 4 wk. Immunohistochemistry was used to detect bromodeoxyuridine (BrdU) labeled proliferating cells, surviving cells, and their phenotype, as well as for determination of oxidative stress (3-NT; 8-OHdG). BDNF and IGF1 mRNA expression was assessed by in situ hybridization. Results showed that: (1) G93A-SED mice had greater hippocampal neurogenesis, BDNF mRNA, and 3-NT, as compared to WT-SED mice. (2) Treadmill running promoted hippocampal neurogenesis and BDNF mRNA content and lowered DNA oxidative damage (8-OHdG) in WT mice. (3) Male G93A mice showed significantly higher cell proliferation but a lower level of survival vs. female G93A mice. We conclude that G93A mice show higher hippocampal neurogenesis, in association with higher BDNF expression, yet running did not further enhance these phenomena in G93A mice, probably due to a 'ceiling effect' of an already heightened basal levels of hippocampal neurogenesis and BDNF expression.