Dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin mediates binding and internalization of Aspergillus fumigatus conidia by dendritic cells and macrophages

Aspergillus fumigatus is responsible for a large percentage of nosocomial opportunistic fungal infections in immunocompromised hosts, especially during cytotoxic chemotherapy and after bone marrow transplantation, and is currently a major direct cause of death in leukemia patients. Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) is a type II C-type lectin that functions as an adhesion receptor and is used by viral and bacterial pathogens to gain access to human DC. We report that DC-SIGN specifically interacts with clinical isolates of A. fumigatus. DC-SIGN-dependent binding of A. fumigatus conidia can be demonstrated with stable transfectants and monocyte-derived DC and is inhibited by anti-DC-SIGN Abs. Binding and internalization of A. fumigatus conidia correlates with DC-SIGN cell surface expression levels and is abolished in the presence of A. fumigatus-derived cell wall galactomannans. The clinical relevance of this interaction is emphasized by the presence of DC-SIGN in lung DC and alveolar macrophages, and further illustrated by the DC-SIGN-dependent attachment of A. fumigatus conidia to the cell membrane of IL-4-treated monocyte-derived macrophages. Our results suggest the involvement of DC-SIGN in the initial stages of pulmonary infection as well as in fungal spreading during invasive aspergillosis.     

Structure of stable protein folding intermediates by equilibrium phi-analysis: the apoflavodoxin thermal intermediate

Protein intermediates in equilibrium with native states may play important roles in protein dynamics but, in cases, can initiate harmful aggregation events. Investigating equilibrium protein intermediates is thus important for understanding protein behaviour (useful or pernicious) but it is hampered by difficulties in gathering structural information. We show here that the phi-analysis techniques developed to investigate transition states of protein folding can be extended to determine low-resolution three-dimensional structures of protein equilibrium intermediates. The analysis proposed is based solely on equilibrium data and is illustrated by determination of the structure of the apoflavodoxin thermal unfolding intermediate. In this conformation, a large part of the protein remains close to natively folded, but a 40 residue region is clearly unfolded. This structure is fully consistent with the NMR data gathered on an apoflavodoxin mutant designed specifically to stabilise the intermediate. The structure shows that the folded region of the intermediate is much larger than the proton slow-exchange core at 25 degrees C. It also reveals that the unfolded region is made of elements whose packing surface is more polar than average. In addition, it constitutes a useful guide to rationally stabilise the native state relative to the intermediate state, a far from trivial task.     

Unconventional secretion of Acb1 is mediated by autophagosomes

Starving Dictyostelium discoideum cells secrete AcbA, an acyl coenzyme A–binding protein (ACBP) that lacks a conventional signal sequence for entering the endoplasmic reticulum (ER). Secretion of AcbA in D. discoideum requires the Golgi-associated protein GRASP. In this study, we report that starvation-induced secretion of Acb1, the Saccharomyces cerevisiae ACBP orthologue, also requires GRASP (Grh1). This highlights the conserved function of GRASP in unconventional secretion. Although genes required for ER to Golgi or Golgi to cell surface transport are not required for Acb1 secretion in yeast, this process involves autophagy genes and the plasma membrane t-SNARE, Sso1. Inhibiting transport to vacuoles does not affect Acb1 secretion. In sum, our experiments reveal a unique secretory pathway where autophagosomes containing Acb1 evade fusion with the vacuole to prevent cargo degradation. We propose that these autophagosome intermediates fuse with recycling endosomes instead to form multivesicular body carriers that then fuse with the plasma membrane to release cargo.     

Long Lasting Effects of Electroconvulsive Seizures on Brain Oxidative Parameters

This work was performed in order to determine the level of oxidative damage and antioxidant enzymes activities late after acute and chronic electroconvulsive shock (ECS) in rats. We measured oxidative parameters in hippocampus, cortex, and striatum, at 45, 60, 90 and 120 days after a single or multiple ECS. We demonstrated an increase in lipid peroxidation after multiple ECS in the hippocampus and striatum. This was also the case for protein carbonyls in the single or multiple protocols. In this way, we demonstrated an increase in catalase in cortex in contrast to striatum and hippocampus, were there were decreases sometimes in chronic ECS. The superoxide dismutase activities decrease in different times after single and multiple ECS in the hippocampus. Our findings demonstrated that there is a delayed increase after ECS in oxidative damage and decrease in antioxidant enzymes activities in hippocampus and striatum.     

Sinorhizobium fredii HH103 mutants affected in capsular polysaccharide (KPS) are impaired for nodulation with soybean and Cajanus cajan

The Sinorhizobium fredii HH103 rkp-1 region, which is involved in capsular polysaccharides (KPS) production, was isolated and sequenced. The organization of the S. fredii genes identified, rkpUAGHIJ and kpsF3, was identical to that described for S. meliloti 1021 but different from that of S. meliloti AK631. The long rkpA gene (7.5 kb) of S. fredii HH103 and S. meliloti 1021 appears as a fusion of six clustered AK631 genes, rkpABCDEF. S. fredii HH103-Rif(r) mutants affected in rkpH or rkpG were constructed. An exoA mutant unable to produce exopolysaccharide (EPS) and a double mutant exoA rkpH also were obtained. Glycine max (soybean) and Cajanus cajan (pigeon pea) plants inoculated with the rkpH, rkpG, and rkpH exoA derivatives of S. fredii HH103 showed reduced nodulation and severe symptoms of nitrogen starvation. The symbiotic capacity of the exoA mutant was not significantly altered. All these results indicate that KPS, but not EPS, is of crucial importance for the symbiotic capacity of S. fredii HH103-Rif(r). S. meliloti strains that produce only EPS or KPS are still effective with alfalfa. In S. fredii HH103, however, EPS and KPS are not equivalent, because mutants in rkp genes are symbiotically impaired regardless of whether or not EPS is produced.     

A molecular approach to the characterization of the eukaryotic communities of an extreme acidic environment: methods for DNA extraction and denaturing gradient gel electrophoresis analysis

The diversity of the phytobenthonic community present in six acidophilic microbial mats from Río Tinto (Iberian Pyritic Belt, SW Spain) was analysed by optical microscopy and two molecular techniques, denaturing gradient gel electrophoresis (DGGE) and sequence analysis of 18S rDNA cloned gene fragments. Sixteen DNA isolation protocols as well as two commercial DNA extraction kits were tested and their efficiency compared. Purified DNA extracts were amplified by PCR using universal eukaryotic primers and the PCR products analysed by DGGE. Bead-mill homogenization was found to be superior to the other cell lysis methodologies assayed (sonication or freeze-thawing cycles) as it allowed efficiencies of cell disruption of over 95%. The methods combining bead-mill homogenization in the presence of SDS, treatment with chemical extractants (hexadecylmethylammonium bromide or guanidine isothiocyanate) and phenol extraction resulted in DNA preparations that amplified the same number of bands when analysed by DGGE as the two commercial kits assayed. The phylogenetic affiliations of the DGGE bands were determined by a BLAST search, and nine different species related to the Chlorophyta, Ciliophora, Kinetoplastida, Ascomycota, Streptophyta and Colcochaetales taxonomical groups were identified. Similar levels of diversity were found using cloning procedures. Although not all the species observed under the microscope were detected using molecular techniques, e.g. euglenas, heliozoan, or amoebae, DGGE fingerprints showed rather well the level of diversity present in the samples analysed, with limitations similar to cloning techniques.     

Differential subcellular distribution of glucose transporters GLUT1-6 and GLUT9 in human cancer: ultrastructural localization of GLUT1 and GLUT5 in breast tumor tissues

It has been proposed that the enhanced metabolic activity of tumor cells is accompanied by an increased expression of facilitative hexose transporters (GLUTs). However, a previous immunohistochemical analysis of GLUT1 expression in 154 malignant human neoplasms failed to detect the GLUT1 isoform in 87 tumors. We used 146 normal human tissues and 215 tumor samples to reassess GLUT1 expression. A similar number of samples were used to compare the expression of GLUT2-6 and 9. The classical expression of GLUT1-5 in different normal human tissues was confirmed, however, we were unable to detect GLUT2 in human pancreatic islet cells. GLUT6 was principally detected in testis germinal cells and GLUT9 was localized in kidney, liver, heart, and adrenal. In tumor samples, GLUT1, 2, and 5 were the main transporters detected. GLUT1 was the most widely expressed transporter, however, 42% of the samples had very low-to-negative expression levels. GLUT2 was detected in 31% of the samples, being mainly expressed in breast, colon, and liver carcinoma. GLUT5 was detected in 27% of breast and colon adenocarcinoma, liver carcinoma, lymphomas, and testis seminoma samples. In situ RT-PCR and ultrastructural immunohistochemistry confirmed GLUT5 expression in breast cancer. GLUT6 and 9 are not clearly over-expressed in human cancer. The extensive expression of GLUT2 and 5 (glucose/fructose and fructose transporters, respectively) in malignant human tissues indicates that fructose may be a good energy substrate in tumor cells. Our functional data obtained in vitro in different tumor cells support this hypothesis. Additionally, these results suggest that fructose uptake could be used for positron emission tomography imaging and, may possibly represent a novel target for the development of therapeutic agents in different human cancers.     

Knockdown of Nav1.6a Na+ channels affects zebrafish motoneuron development

In addition to rapid signaling, electrical activity provides important cues to developing neurons. Electrical activity relies on the function of several different types of voltage-gated ion channels. Whereas voltage-gated Ca2+ channel activity regulates several aspects of neuronal differentiation, much less is known about developmental roles of voltage-gated Na+ channels, essential mediators of electrical signaling. Here, we focus on the zebrafish Na+ channel isotype, Nav1.6a, which is encoded by the scn8a gene. A restricted set of spinal neurons, including dorsal sensory Rohon-Beard cells, two motoneuron subtypes with different axonal trajectories, express scn8a during embryonic development. CaP, an early born primary motoneuron subtype with ventrally projecting axons expresses scn8a, as does a class of secondary motoneurons with axons that project dorsally. To test for developmental roles of scn8a, we knocked down Nav1.6a protein using antisense morpholinos. Na+ channel protein and current amplitudes were reduced in neurons that express scn8a. Furthermore, Nav1.6a knockdown altered axonal morphologies of some but not all motoneurons. Dorsally projecting secondary motoneurons express scn8a and displayed delayed axonal outgrowth. By contrast, CaP axons developed normally, despite expression of the gene. Surprisingly, ventrally projecting secondary motoneurons, a population in which scn8a was not detected, displayed aberrant axonal morphologies. Mosaic analysis indicated that effects on ventrally projecting secondary motoneurons were non cell-autonomous. Thus, voltage-gated Na+ channels play cell-autonomous and non cell-autonomous roles during neuronal development.     

Role of NPR-C natriuretic receptor in nitric oxide system activation induced by atrial natriuretic peptide

Atrial natriuretic peptide (ANP) exerts its hypotensive, natriuretic and diuretic effects, almost in part, through the activation of nitric oxide synthase (NOS). The aim was to investigate the natriuretic receptor type and the signaling cascade involved in NOS activation induced by ANP. Male Wistar rats were sacrificed and NOS activity was determined in kidney, aorta and heart with L-[U14C]-arginine, as substrate. ANP and cANP (4-23), a selective NPR-C ligand, increased NOS activity in all tissues. ANP induced a more marked activation in aorta and kidney than cANP (4-23), but no difference in atria NOS activation was observed. NOS activity induced by both peptides was blunted by nifedipine (L-type channel blocker) and calmidazolium (calmodulin antagonist) in heart and aorta. In kidney, nifedipine and calmidazolium abolished NOS activity stimulated by cANP (4-23) but only partially inhibited NOS activity elicited by ANP. Gi inhibition with pertussis toxin abolished NOS activity stimulated by ANP and cANP in atria but only partially inhibited the increased NOS activity induced by ANP and cANP in kidney, aorta and ventricle. Our results show that NPR-C receptor would mediate the activation of NOS by ANP in atria. In kidney, aorta and ventricle, NOS activation would also involve NPR-A and/or B. ANP would interact with NPR-C coupled via Gi to activation Ca2+ -dependent NOS.     

Activation of the 12-lipoxygenase and signal transducer and activator of transcription pathway during neointima formation in a model of the metabolic syndrome

Insulin resistance (IR) is associated with an increased risk of cardiovascular diseases. The obese Zucker rat (ZR) is a model of IR that shows markedly increased insulin and triglyceride concentrations without major changes in glucose. In this study, we evaluated the response of obese and lean ZR to carotid balloon injury and determined potential mechanisms and treatments. The neointima-to-media ratio of obese ZR was greater than that of lean ZR, starting at 14 days after injury, and persisted until at least day 30. An enhanced inflammatory response to balloon injury in the obese ZR was reflected by significantly higher ED1-positive macrophage cells in the injured vessel wall compared with that in lean ZR at 3, 7, and 14 days after balloon injury. Inflammatory mediators 12-lipoxygenase (12-LO) and STAT4 were studied in neointimal lesions. Expression of 12-LO RNA was increased beginning at day 7 and showed increases of 4.3-fold on day 14 and 7-fold on day 30 in obese ZR compared with lean animals. Staining of phosphorylated STAT4 (PSTAT4), the activated form of STAT4, in lesions from obese ZR was also increased compared with that in leans. We tested the effects of a novel anti-inflammatory agent, lisofylline (LSF), in the obese ZR. LSF markedly reduced neointimal formation in the obese ZR. LSF also reduced monocyte/macrophage infiltration into the vessel wall and the activation of PSTAT4. These studies suggest both the presence of an exaggerated injury response in the insulin-resistant obese ZR model and that inflammation plays a major role in mediating neointimal growth.