Taurine deficiency damages retinal neurones: cone photoreceptors and retinal ganglion cells

In 1970s, taurine deficiency was reported to induce photoreceptor degeneration in cats and rats. Recently, we found that taurine deficiency contributes to the retinal toxicity of vigabatrin, an antiepileptic drug. However, in this toxicity, retinal ganglion cells were degenerating in parallel to cone photoreceptors. The aim of this study was to re-assess a classic mouse model of taurine deficiency following a treatment with guanidoethane sulfonate (GES), a taurine transporter inhibitor to determine whether retinal ganglion cells are also affected. GES treatment induced a significant reduction in the taurine plasma levels and a lower weight increase. At the functional level, photopic electroretinograms were reduced indicating a dysfunction in the cone pathway. A change in the autofluorescence appearance of the eye fundus was explained on histological sections by an increased autofluorescence of the retinal pigment epithelium. Although the general morphology of the retina was not affected, cell damages were indicated by the general increase in glial fibrillary acidic protein expression. When cell quantification was achieved on retinal sections, the number of outer/inner segments of cone photoreceptors was reduced (20?%) as the number of retinal ganglion cells (19?%). An abnormal synaptic plasticity of rod bipolar cell dendrites was also observed in GES-treated mice. These results indicate that taurine deficiency can not only lead to photoreceptor degeneration but also to retinal ganglion cell loss. Cone photoreceptors and retinal ganglion cells appear as the most sensitive cells to taurine deficiency. These results may explain the recent therapeutic interest of taurine in retinal degenerative pathologies.     

Post-translational modification of plant-made foreign proteins; glycosylation and beyond

The complex and diverse nature of the post-translational modification (PTM) of proteins represents an efficient and cost-effective mechanism for the exponential diversification of the genome. PTMs have been shown to affect almost every aspect of protein activity, including function, localisation, stability, and dynamic interactions with other molecules. Although many PTMs are evolutionarily conserved there are also important kingdom-specific modifications which should be considered when expressing recombinant proteins. Plants are gaining increasing acceptance as an expression system for recombinant proteins, particularly where eukaryotic-like PTMs are required. Glycosylation is the most extensively studied PTM of plant-made recombinant proteins. However, other types of protein processing and modification also occur which are important for the production of high quality recombinant protein, such as hydroxylation and lipidation. Plant and/or protein engineering approaches offer many opportunities to exploit PTM pathways allowing the molecular farmer to produce a humanised product with modifications functionally similar or identical to the native protein. Indeed, plants have demonstrated a high degree of tolerance to changes in PTM pathways allowing recombinant proteins to be modified in a specific and controlled manner, frequently resulting in a homogeneity of product which is currently unrivalled by alternative expression platforms. Whether a recombinant protein is intended for use as a scientific reagent, a cosmetic additive or as a pharmaceutical, PTMs through their presence and complexity, offer an extensive range of options for the rational design of humanised (biosimilar), enhanced (biobetter) or novel products.     

Phototherapy and orange-tinted goggles for night-shift adaptation of police officers on patrol

The aim of the present combined field and laboratory study was to assess circadian entrainment in two groups of police officers working seven consecutive 8/8.5-h night shifts as part of a rotating schedule. Eight full-time police officers on patrol (mean age ± SD: 29.8 ± 6.5 yrs) were provided an intervention consisting of intermittent exposure to wide-spectrum bright light at night, orange-tinted goggles at sunrise, and maintenance of a regular sleep/darkness episode in the day. Orange-tinted goggles have been shown to block the melatonin-suppressing effect of light significantly more than neutral gray density goggles. Nine control group police officers (mean age ± SD: 30.3 ± 4.1 yrs) working the same schedule were enrolled. Police officers were studied before, after (in the laboratory), and during (ambulatory) a series of seven consecutive nights. Urine samples were collected at wake time and bedtime throughout the week of night work and during laboratory visits (1 × /3 h) preceding and following the work week to measure urinary 6-sulfatoxymelatonin (UaMT6s) excretion rate. Subjective alertness was assessed at the start, middle, and end of night shifts. A 10-min psychomotor vigilance task was performed at the start and end of each shift. Both laboratory visits consisted of two 8-h sleep episodes based on the prior schedule. Saliva samples were collected 2 × /h during waking episodes to assay their melatonin content. Subjective alertness (3 × /h) and performance (1 × /2 h) were assessed during wake periods in the laboratory. A mixed linear model was used to analyze the progression of UaMt6s excreted during daytime sleep episodes at home, as well as psychomotor performance and subjective alertness during night shifts. Two-way analysis of variance (ANOVA) (factors: laboratory visit and group) were used to compare peak salivary melatonin and UaMT6s excretion rate in the laboratory. In both groups of police officers, the excretion rate of UaMT6s at home was higher during daytime sleep episodes at the end compared to the start of the work week (p 相似文献   

Host Protein BSL1 Associates with Phytophthora infestans RXLR Effector AVR2 and the Solanum demissum Immune Receptor R2 to Mediate Disease Resistance

Plant pathogens secrete effector proteins to modulate plant immunity and promote host colonization. Plant nucleotide binding leucine-rich repeat (NB-LRR) immunoreceptors recognize specific pathogen effectors directly or indirectly. Little is known about how NB-LRR proteins recognize effectors of filamentous plant pathogens, such as Phytophthora infestans. AVR2 belongs to a family of 13 sequence-divergent P. infestans RXLR effectors that are differentially recognized by members of the R2 NB-LRR family in Solanum demissum. We report that the putative plant phosphatase BSU-LIKE PROTEIN1 (BSL1) is required for R2-mediated perception of AVR2 and resistance to P. infestans. AVR2 associates with BSL1 and mediates the interaction of BSL1 with R2 in planta, possibly through the formation of a ternary complex. Strains of P. infestans that are virulent on R2 potatoes express an unrecognized form, Avr2-like (referred to as A2l). A2L can still interact with BSL1 but does not promote the association of BSL1 with R2. Our findings show that recognition of the P. infestans AVR2 effector by the NB-LRR protein R2 requires the putative phosphatase BSL1. This reveals that, similar to effectors of phytopathogenic bacteria, recognition of filamentous pathogen effectors can be mediated via a host protein that interacts with both the effector and the NB-LRR immunoreceptor.     

Finite element study of a tissue-engineered cartilage transplant in human tibiofemoral joint

Most tissue-engineered cartilage constructs are more compliant than native articular cartilage (AC) and are poorly integrated to the surrounding tissue. To investigate the effect of an implanted tissue-engineered construct (TEC) with these inferior properties on the mechanical environment of both the engineered and adjacent native tissues, a finite element study was conducted. Biphasic swelling was used to model tibial cartilage and an implanted TEC with the material properties of either native tissue or a decreased elastic modulus and fixed charged density. Creep loading was applied with a rigid impermeable indenter that represented the femur. In comparison with an intact joint, compressive strains in the transplant, surface contact stress in the adjacent native AC and load partitioning between different phases of cartilage were affected by inferior properties of TEC. Results of this study may lead to a better understanding of the complex mechanical environment of an implanted TEC.     

Degradation of the Endoplasmic Reticulum by Autophagy during Endoplasmic Reticulum Stress in Arabidopsis

In this article, we show that the endoplasmic reticulum (ER) in Arabidopsis thaliana undergoes morphological changes in structure during ER stress that can be attributed to autophagy. ER stress agents trigger autophagy as demonstrated by increased production of autophagosomes. In response to ER stress, a soluble ER marker localizes to autophagosomes and accumulates in the vacuole upon inhibition of vacuolar proteases. Membrane lamellae decorated with ribosomes were observed inside autophagic bodies, demonstrating that portions of the ER are delivered to the vacuole by autophagy during ER stress. In addition, an ER stress sensor, INOSITOL-REQUIRING ENZYME-1b (IRE1b), was found to be required for ER stress–induced autophagy. However, the IRE1b splicing target, bZIP60, did not seem to be involved, suggesting the existence of an undiscovered signaling pathway to regulate ER stress–induced autophagy in plants. Together, these results suggest that autophagy serves as a pathway for the turnover of ER membrane and its contents in response to ER stress in plants.     

The physical properties of the capsular polysaccharides from Cryptococcus neoformans suggest features for capsule construction

The most distinctive feature of the human pathogenic fungus is a polysaccharide capsule that is essential for virulence and is composed primarily of glucuronoxylomannan (GXM) and galactoxylomannan (GalXM). GXM mediates multiple deleterious effects on host immune function, yet relatively little is known about its physical properties. The average mass of Cryptococcus neoformans GXM from four antigenically different strains ranged from 1.7 to 7 x 10(6) daltons as calculated from Zimm plots of light-scattering data. GalXM was significantly smaller than GXM, with an average mass of 1 x 10(5) daltons. These molecular masses imply that GalXM is the most numerous polysaccharide in the capsule on a molar basis. The radius of gyration of the capsular polysaccharides ranged between 68 and 208 nm. Viscosity measurements suggest that neither polysaccharide altered fluid dynamics during infection since GXM behaved in solution as a polyelectrolyte and GalXM did not increase solution viscosity. Immunoblot analysis indicated heterogeneity within GXM. In agreement with this, scanning transmission electron microscopy of GXM preparations revealed a tangled network of two different types of molecules. Mass per length measurements from light scattering and scanning transmission electron microscopy were consistent and suggested GXM molecules self-associate. A mechanism for capsule growth is proposed based on the extracellular release and entanglement of GXM molecules.     

Purification, kinetic characterization, and mapping of the minimal catalytic domain and the key polar groups of Helicobacter pylori alpha-(1,3/1,4)-fucosyltransferases

The minimal catalytic domain of alpha-(1,3/1,4)-fucosyltransferases (FucTs) from Helicobacter pylori strains NCTC11639 and UA948 was mapped by N- and C-terminal truncations. Only the C terminus could be truncated without significant loss of activity. 11639FucT and UA948FucT contain 10 and 8 heptad repeats, respectively, which connect the catalytic domain with the C-terminal putative amphipathic alpha-helices. Deletion of all heptad repeats almost completely abolished enzyme activity. Nevertheless, with only one heptad repeat 11639FucT is fully active, whereas UA948FucT is partially active. Removal of the two putative amphipathic alpha-helices dramatically increased protein expression and solubility, enabling purification with yields of milligrams/liter. Steady-state kinetic analysis of the purified FucTs showed that 11639FucTs possessed slightly tighter binding affinity for both Type II acceptor and GDP-fucose donor than UA948FucT, and its kcat of 2.3 s(-1) was double that of UA948FucT, which had a kcat value of 1.1 s(-1) for both Type II and Type I acceptors. UA948FucT strongly favors Type II over the Type I acceptor with a 20-fold difference in acceptor Km. Sixteen modified Type I and Type II series acceptors were employed to map the molecular determinants of acceptors required for recognition by H. pylori alpha-(1,3/1,4)-FucTs. Deoxygenation at 6-C of the galactose in Type II acceptor caused a 5000-fold decrease in alpha1,3 activity, whereas in Type I acceptor this completely abolished alpha1,4 activity, indicating that this hydroxyl group is a key polar group.