Genomic blueprint of Hahella chejuensis, a marine microbe producing an algicidal agent

Harmful algal blooms, caused by rapid growth and accumulation of certain microalgae in the ocean, pose considerable impacts on marine environments, aquatic industries and even public health. Here, we present the 7.2-megabase genome of the marine bacterium Hahella chejuensis including genes responsible for the biosynthesis of a pigment which has the lytic activity against a red-tide dinoflagellate. H.chejuensis is the first sequenced species in the Oceanospiralles clade, and sequence analysis revealed its distant relationship to the Pseudomonas group. The genome was well equipped with genes for basic metabolic capabilities and contained a large number of genes involved in regulation or transport as well as with characteristics as a marine heterotroph. Sequence analysis also revealed a multitude of genes of functional equivalence or of possible foreign origin. Functions encoded in the genomic islands include biosynthesis of exopolysacchrides, toxins, polyketides or non-ribosomal peptides, iron utilization, motility, type III protein secretion and pigmentation. Molecular structure of the algicidal pigment, which was determined through LC-ESI-MS/MS and NMR analyses, indicated that it is prodigiosin. In conclusion, our work provides new insights into mitigating algal blooms in addition to genetic make-up, physiology, biotic interactions and biological roles in the community of a marine bacterium.     

Polymorphisms of complement receptor 1 and interleukin-10 genes and systemic lupus erythematosus: a meta-analysis

A number of studies have tested the association of the complement receptor 1 (CR1) and Interleukin-10 (IL10) polymorphisms with systemic lupus erythematosus (SLE), but reported conflicting results. The aim of the study is to explore whether the CR1 and IL10 genes are associated with SLE susceptibility. We surveyed studies on the CR1 and IL10 polymorphisms and SLE using comprehensive Medline search and review of the references. A meta-analysis was conducted in a fixed effects model or random effects model based on between-study heterogeneity. Eighteen comparisons from 13 studies were included in the CR1 meta-analysis and a total of 16 separate comparisons were used for the IL10 meta-analysis. The CR1 meta-analysis showed no significant association of the CR1 functional polymorphisms with SLE. In contrast, the S structural variant of the CR1 showed a significant association (OR=1.544, 95% CI, 1.217–1.959, P<0.001). Stratification by ethnicity indicated that the CR1 S variant was associated with SLE in Caucasians (OR=1.667, 95% CI, 1.193–2.357, P=0.003). The IL10 meta-analysis showed a significant association between SLE and the G11 allele of IL10.G (OR=1.279, 95% CI; 1.027–1.593, P=0.028) in whole populations, and IL10 promoter −1082G allele was associated with SLE in Asians (OR=1.358, 95% CI; 1.015–1.816, P=0.039). In conclusion, the CR1 meta-analysis revealed the association of the S structural variant of the CR1 with SLE and the IL10 meta-analysis showed the association of IL10.G11 allele and SLE in whole populations and the association between promoter -A1082G polymorphism and SLE in Asians.     

Encapsulating live cells with water-soluble chitosan in physiological conditions

A new class of microcapsules was prepared under physiological conditions by polyelectrolyte complexation between two oppositely-charged, water-soluble polymers. The microcapsules consisted of an inner core of half N-acetylated chitosan and an outer shell of methacrylic acid (MAA) (20.4%)-hydroxyethyl methacrylate (HEMA) (27.4%)-methyl methacrylate (MMA) (52.2%) (MAA-HEMA-MMA) terpolymer. Both 400 and 150 kDa half N-acetylated chitosans maintained good water solubility and supplied enough protonated amino groups to coacervate with terpolymer at pH 7.0-7.4, in contrast to other chitosan-based microcapsules which must be prepared at pH <6.5. The viscosity of half N-acetylated chitosan solutions between 80 and 3000 cPas allowed the formation of microcapsules with spherical shape. Molar mass, pH and concentration of half N-acetylated chitosan, and reaction time, influenced the morphology, thickness and porosity of the microcapsules. Microcapsules formed with high concentration of half N-acetylated chitosan exhibited improved mechanical stability, whereas microcapsules formed with low concentration of half N-acetylated chitosan exhibited good permeability. This 3D microenvironment has been configured to cultivate sensitive anchorage-dependent cells such as hepatocytes to maintain high level of functions.     

The G protein-coupled receptor kinase-2 is a TGFbeta-inducible antagonist of TGFbeta signal transduction

Signaling from the activin/transforming growth factor beta (TGFbeta) family of cytokines is a tightly regulated process. Disregulation of TGFbeta signaling is often the underlying basis for various cancers, tumor metastasis, inflammatory and autoimmune diseases. In this study, we identify the protein G-coupled receptor kinase 2 (GRK2), a kinase involved in the desensitization of G protein-coupled receptors (GPCR), as a downstream target and regulator of the TGFbeta-signaling cascade. TGFbeta-induced expression of GRK2 acts in a negative feedback loop to control TGFbeta biological responses. Upon TGFbeta stimulation, GRK2 associates with the receptor-regulated Smads (R-Smads) through their MH1 and MH2 domains and phosphorylates their linker region. GRK2 phosphorylation of the R-Smads inhibits their carboxyl-terminal, activating phosphorylation by the type I receptor kinase, thus preventing nuclear translocation of the Smad complex, leading to the inhibition of TGFbeta-mediated target gene expression, cell growth inhibition and apoptosis. Furthermore, we demonstrate that GRK2 antagonizes TGFbeta-induced target gene expression and apoptosis ex vivo in primary hepatocytes, establishing a new role for GRK2 in modulating single-transmembrane serine/threonine kinase receptor-mediated signal transduction.     

Single amino acid substitutions in the severe acute respiratory syndrome coronavirus spike glycoprotein determine viral entry and immunogenicity of a major neutralizing domain

Neutralizing antibodies (NAbs) against severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) spike (S) glycoprotein confer protection to animals experimentally infected with the pathogenic virus. We and others previously demonstrated that a major mechanism for neutralizing SARS-CoV was through blocking the interaction between the S glycoprotein and the cellular receptor angiotensin-converting enzyme 2 (ACE2). In this study, we used in vivo electroporation DNA immunization and a pseudovirus-based assay to functionally evaluate immunogenicity and viral entry. We characterized the neutralization and viral entry determinants within the ACE2-binding domain of the S glycoprotein. The deletion of a positively charged region Sdelta(422-463) abolished the capacity of the S glycoprotein to induce NAbs in mice vaccinated by in vivo DNA electroporation. Moreover, the Sdelta(422-463) pseudovirus was unable to infect HEK293T-ACE2 cells. To determine the specific residues that contribute to related phenotypes, we replaced eight basic amino acids with alanine. We found that a single amino acid substitution (R441A) in the full-length S DNA vaccine failed to induce NAbs and abolished viral entry when pseudoviruses were generated. However, another substitution (R453A) abolished viral entry while retaining the capacity for inducing NAbs. The difference between R441A and R453A suggests that the determinants for immunogenicity and viral entry may not be identical. Our findings provide direct evidence that these basic residues are essential for immunogenicity of the major neutralizing domain and for viral entry. Our data have implications for the rational design of vaccine and antiviral agents as well as for understanding viral tropism.     

The effect of rate of distraction osteogenesis on structure and function of anterior digastric muscle fibers

The authors hypothesized that distraction at a rate of 3 mm/day, compared with mandibular distraction at a rate of 1 mm/day, would produce a maladaptive response in adjacent muscles of mastication. The authors further hypothesized that the maladaptive response would manifest at the single fiber level by means of increased sarcomeric heterogeneity, decreased maximum force output, and increased susceptibility to stretch-induced injury. In an ovine model, distraction osteogenesis of the right hemimandible was performed at either 1 mm/day for 21 days (n = 2) or 3 mm/day for 7 days (n = 2) to achieve a total distraction distance of 21 mm. The left hemimandibles served as controls. After a consolidation period of 2 days, the anterior digastric muscles were harvested; in six randomly selected single fibers from each muscle, maximum calcium-activated force (Po) was measured at optimal sarcomere length. The amount of damage to the sarcomeres in each fiber was assessed microscopically. To test susceptibility to contraction-induced injury, each fiber was given an activated stretch of 20 percent. Compared with control fibers and fibers distracted at 1 mm/day, maximum tetanic force (Po) was significantly lower in fibers distracted at 3 mm/day. Compared with control fibers, specific Po (Po/cross-sectional area) was lower in fibers distracted at 3 mm/day. The number of sarcomeres appearing damaged in fibers distracted at 3 mm/day was significantly higher than in control fibers or in fibers distracted at 1 mm/day. A greater deficit in Po was observed after a single activated stretch in fibers distracted at 3 mm/day than in control fibers or in fibers distracted at 1 mm/day. The authors conclude that distraction of the anterior digastric muscle in sheep at 3 mm/day produces a maladaptive response in the muscle fibers but a rate of 1 mm/day is tolerated by the muscle fibers. These data are consistent with the hypothesis that distraction of skeletal muscle at high rates results in increased heterogeneity of sarcomere lengths and that this increase in heterogeneity is the most likely potential mechanism resulting in whole muscle force deficits and in increased susceptibility to stretch-induced injury in distracted muscles.