Structure and evolution of <Emphasis Type="Italic">Apetala3</Emphasis>, a sex-linked gene in <Emphasis Type="Italic">Silene latifolia</Emphasis>

Background  

The evolution of sex chromosomes is often accompanied by gene or chromosome rearrangements. Recently, the gene AP3 was characterized in the dioecious plant species Silene latifolia. It was suggested that this gene had been transferred from an autosome to the Y chromosome.     

Retrieval of the Alzheimer's amyloid precursor protein from the endosome to the TGN is S655 phosphorylation state-dependent and retromer-mediated

Background

Retrograde transport of several transmembrane proteins from endosomes to the trans-Golgi network (TGN) occurs via Rab 5-containing endosomes, mediated by clathrin and the recently characterized retromer complex. This complex and one of its putative sorting receptor components, SorLA, were reported to be associated to late onset Alzheimer's disease (AD). The pathogenesis of this neurodegenerative disorder is still elusive, although accumulation of amyloidogenic Abeta is a hallmark. This peptide is generated from the sucessive β- and γ- secretase proteolysis of the Alzheimer's amyloid precursor protein (APP), events which are associated with endocytic pathway compartments. Therefore, APP targeting and time of residence in endosomes would be predicted to modulate Abeta levels. However, the formation of an APP- and retromer-containing protein complex with potential functions in retrieval of APP from the endosome to the TGN had, to date, not been demonstrated directly. Further, the motif(s) in APP that regulate its sorting to the TGN have not been characterized.

Results

Through the use of APP-GFP constructs, we show that APP containing endocytic vesicles targeted for the TGN, are also immunoreactive for clathrin-, Rab 5- and VPS35. Further, they frequently generate protruding tubules near the TGN, supporting an association with a retromer-mediated pathway. Importantly, we show for the first time, that mimicking APP phosphorylation at S655, within the APP 653YTSI656 basolateral motif, enhances APP retrieval via a retromer-mediated process. The phosphomimetic APP S655E displays decreased APP lysosomal targeting, enhanced mature half-life, and decreased tendency towards Abeta production. VPS35 downregulation impairs the phosphorylation dependent APP retrieval to the TGN, and decreases APP half-life.

Conclusions

We reported for the first time the importance of APP phosphorylation on S655 in regulating its retromer-mediated sorting to the TGN or lysosomes. Significantly, the data are consistent with known interactions involving the retromer, SorLA and APP. Further, these findings add to our understanding of APP targeting and potentially contribute to our knowledge of sporadic AD pathogenesis representing putative new targets for AD therapeutic strategies.     

Instantaneous benthic response to different organic matter quality: In situ experiments in the Benguela Upwelling System

The benthic community in continental slope and deep-sea sediments of the Benguela Upwelling System was supplied with ¹³C-labelled organic matter (OM) of two different qualities using a benthic chamber lander. Freeze-dried cultures of Skeletonema costatum served as 'fresh' OM. 'Altered' OM of the same material had been additionally dialysed to remove low-molecular weight compounds. In order to investigate the benthic response pattern, mineralization of labelled OM, uptake by macrofauna and incorporation into bacteria were followed over 18-36 h. Total oxygen uptake was not affected beyond natural variation by the OM addition. Mineralization dominated the ¹³C-labelled phytodetritus processing, constituting 71-95% of the total processed OM. Bacterial incorporation of phytodetrital carbon exceeded macrofaunal uptake at all stations. Stations situated in a major centre of OM deposition showed phytodetritus processing rates on average twice as high as outside the depocentre. Phytodetritus processing was 1.5, 2.5 and 4.3 times higher for fresh than for altered OM at 605, 1019 and 1335 m water depth, respectively. Our observations clearly indicate the importance of OM quality on mineralization rates.     

Second-Harmonic Generation from Dendritic Fractal Structures

Plasmonics - Nanostructured conductive surfaces have been exploited for a variety of applications in photonics and optical sensing due to the broad spectral tunability of the localized surface...     

A single amino acid change (Y318F) in the L-arabitol dehydrogenase (LadA) from Aspergillus niger results in a significant increase in affinity for D-sorbitol

Background  

L-arabitol dehydrogenase (LAD) and xylitol dehydrogenase (XDH) are involved in the degradation of L-arabinose and D-xylose, which are among the most abundant monosaccharides on earth. Previous data demonstrated that LAD and XDH not only differ in the activity on their biological substrate, but also that only XDH has significant activity on D-sorbitol and may therefore be more closely related to D-sorbitol dehydrogenases (SDH). In this study we aimed to identify residues involved in the difference in substrate specificity.     

Characterization of Vibrio cholerae eltor in the city of Kazan in 2001

Information on V. cholerae eltor isolated in the focus of cholera in Kazan in 2001 at different periods of the outbreak is presented. The identity of strains isolated from patients, vibriocarriers and environmental objects, including their antibioticograms (sensitivity to cyprofloxacin and resistance to trimethoprim--sulfamethoxazole, streptomycin, furazolidone and nalidixic acid, which may be regarded as markers), is shown. Variable tandem repetitions in the DNA of 30 isolates strains of different origin have been determined. The results of this determination make it possible to classify all these strains as one genotype, which confirms the suggestion on the circulation of one subclone of the infective agent of cholera in the focus. As revealed in this investigation, the isolated strains are labile with respect to diagnostic phage eltor, while ctx+ strains are resistant to phage eltor ctx+.     

Evaluation of polysaccharide antigens of Vibrio cholerae O139 of different origin by monoclonal antibodies

The epitope composition of O-polysaccharides in the lipopolysaccharide (LPS) of V. cholerae, serogroup O139, isolated from clinical material and water of surface reservoirs was analyzed with the use of monoclonal antibodies. The analysis demonstrated that these O-polysaccharides were similar in their structure and chemical composition. In LPS of V. cholerae O139 clinical strains O-polysaccharide determinants occurred more often. Among V. cholerae isolated from water strains on whose surface individual epitopes of O-polysaccharide occurred less frequently or were absent appeared to be more numerous. A decrease in the concentration of microbial cells in the process of their testing by immunological methods led to increased percent of negative reactions with specific antibodies. Some V. cholerae O139 strains isolated from water were similar in the epitope composition of their O-polysaccharide and binding activity to cultures isolated from humans. As indicated by the results of these studies, cholera vibrios Bengal and vibrios isolated from river water on the territory of Russia had quantitative differences due to a higher level of the production of O-polysaccharide determinants and their occurrence in V. cholerae of serogroup O139.     

Characterization of Vibrio cholerae O1 cultures isolated from environmental objects on the territory of the Russian Federation in 2002

The biological properties of 46 V. cholerae O1 eltor cultures isolated in 2002 from water environment on the territory of Russia are presented. All isolated vibrios proved to be typical in their cultural, morphological, biochemical and serological properties. The atypical character of some of them was mainly linked with their phage resistance. The appearance of vibrios, sensitive to bacteriophage ctx+ and containing gene tcp in the absence gene ctx, was noted. Multilocus VNTR typing made it possible to group the cultures under study in 34 genotypes. The presence of toxin coregulated pili was found to be directly related to locus VcB. The necessity of the systematic study of the pheno- and genotypes of the isolated cultures with the aim of epidemiological surveillance of this infection is emphasized.     

The determination of the optimal conditions for the production of a number of pathogenicity factors in Vibrio cholerae

Conditions for the cultivation of V. cholerae of different sero- and biovars on tryptone medium, ensuring the maximum production of cholera toxin (CT), dermonecrotic factor (DNF), hemorrhagic factor (HF) and new cholera toxin (NCT) have been determined. The lack of coincidence in the optimum conditions ensuring the maximum production of CT, DNF and HF has been established, which may be indicative of different nature of these toxic substances. NCT, produced by vct- strains, is similar to CN in biological activity as determined in the skin permeability test and in the conditions of accumulation in tryptone medium.