Role of the Kinesin-like Protein KipB in Aspergillus nidulans

Molecular motors are protein machines, which power almost all forms of movement in the living world. Among the best known are the motors that hydrolyze ATP and use the derived energy to generate force. They are involved in a variety of diverse cellular functions as vesicle and organelle transport, cytoskeleton dynamics, morphogenesis, polarized growth, cell movements, spindle formation, chromosome movement, nuclear fusion, and signal transduction. Three superfamilies of molecular motors, kinesins, dyneins, and myosins, have so far been well characterized. These motors use microtubules (in the case of kinesines and dyneins) or actin filaments (in the case of myosins) as tracks to transport cargo materials within a cell. Analysis of fungal genomes revealed at least 10 distinct kinesins in filamentous fungi, some of which are not found in yeasts. We used the motor domain of conventional kinesin (KinA) from Aspergillus nidulans to perfom BLAST searches at the public A. nidulans genome database, at the Whitehead Center for Genome Research (Cambridge USA), and identified eleven putative kinesin motors. They grouped into nine of the eleven families, two kinesins being found in the Unc104 familiy and interestingly, one did not fall into any of the known families. The present work analyses the function of a kinesin-like protein in A. nidulans, KipB, which is a member of the Kip3 kinesin family. This family includes one representative in Saccharomyces cerevisiae (Kip3, the family founding member), two in Schizosaccharomyces pombe, Klp5 and Klp6 and one in Drosophila, Klp67A, the single one reported so far for higher eukaryotes in this family. Kip3 kinesins are implicated in microtubule disassembly and are required for chromosome segregation in mitosis and meiosis. To assess the function of KipB kinesin in A. nidulans, a kipB disruption strain was constructed. Analysis of the DkipB mutant revealed new features concerning the cellular functions of Kip3 proteins, but also some conserved ones. kipB is not essential for vegetative growth, and meiosis and ascospore formation were not affected in the DkipB mutant. The KipB protein was shown to be involved in the turnover of interphase cytoplasmic, mitotic and astral microtubules. DkipB mutants are less sensitive to the microtubule-destabilizing drug benomyl, and the microtubule cytoskeleton of interphase cells in DkipB mutants appears altered. Interestingly, spindle morphology and positioning were severely affected. Spindles were highly mobile, could overpass each other, moved over long distances through the cytoplasm, and displayed in 64% of the cases an extremely bent shape, latter feature being the first time reported for Kip3 kinesins. Mitotic progression was delayed in the DkipB mutant and a higher number of cytoplasmic microtubules remained intact during mitosis. DkipB heterozygous strains showed an increased instability of diploid nuclei, which proved once more KipB involvement in mitosis, along with DkipB clear genetic interaction with a mutation in another mitotic kinesin in A. nidulans, bimC4. An N-terminal GFP-KipB construct localized to cytoplasmic microtubules in interphase cells and to spindle and astral microtubules during mitosis, in a discontinuous pattern. Speckles of GFP-KipB appeared to be aligned in the cell. Time-lapse video microscopy indicated that the spots were moving independently towards the microtubule plus ends. This advanced the hypothesis that KipB could display processivity and intrinsic motility along microtubules, or that other kinesins involved in organelle motility are able to target the KipB protein to the microtubule plus ends. In the case of C-terminally truncated GFP-KipB protein versions, a stronger GFP signal was obtained and colocalization with a-tubulin-GFP revealed that they uniformly stain cytoplasmic, mitotic and astral microtubules. This suggests that the C-terminus is important for the correct localization and the movement of KipB protein along microtubules

Immunological characterization of chromogranins A and B and secretogranin II in the bovine pancreatic islet

Antisera against chromogranin A and B and secretogranin II were used for analysing the bovine pancreas by immunoblotting and immunohistochemistry. All three antigens were found in extracts of fetal pancreas by one dimensional immunoblotting. A comparison with the soluble proteins of chromaffin granules revealed that in adrenal medulla and in pancreas antigens which migrated identically in electrophoresis were present. In immunohistochemistry, chromogranin A was found in all pancreatic endocrine cell types with the exception of most pancreatic polypeptide-(PP-) producing cells. For chromogranin B, only a faint immunostaining was obtained. For secretorgranin II, A-and B-cells were faintly positive, whereas the majority of PP-cells exhibited a strong immunostaining for this antigen. These results establish that chromogranins A and B and secretogranin II are present in the endocrine pancreas, but that they exhibit a distinct cellular localization

Helminths and HIV infection: epidemiological observations on immunological hypotheses

Parasitic helminths have co-evolved with the mammalian immune system. Current hypotheses suggest that immunological stimulation in the presence of helminths is balanced by immuno-regulation and by the broad spectrum of mechanisms possessed by helminths for countering the host immune response. The degree to which this balance is perfected, and the mechanisms by which this is achieved, vary between helminth species; we suggest that this is reflected not only in the degree of pathology induced by helminths but also in a variety of relationships with HIV infection and HIV disease. Available epidemiological data regarding interactions between helminths and HIV are largely observational; results are variable and generally inconclusive. Well designed, controlled intervention studies are required to provide definitive information on the species-specific nature of these interactions and on the advantages, disadvantages and optimal timing of de-worming in relation to HIV infection

Backbone rigidity and static presentation of guanidinium groups increases cellular uptake of arginine-rich cell-penetrating peptides

In addition to endocytosis-mediated cellular uptake, hydrophilic cell-penetrating peptides are able to traverse biological membranes in a non-endocytic mode termed transduction, resulting in immediate bioavailability. Here we analysed structural requirements for the non-endocytic uptake mode of arginine-rich cell-penetrating peptides, by a combination of live-cell microscopy, molecular dynamics simulations and analytical ultracentrifugation. We demonstrate that the transduction efficiency of arginine-rich peptides increases with higher peptide structural rigidity. Consequently, cyclic arginine-rich cell-penetrating peptides showed enhanced cellular uptake kinetics relative to their linear and more flexible counterpart. We propose that guanidinium groups are forced into maximally distant positions by cyclization. This orientation increases membrane contacts leading to enhanced cell penetration

A Condensation-Ordering Mechanism in Nanoparticle-Catalyzed Peptide Aggregation

Nanoparticles introduced in living cells are capable of strongly promoting the aggregation of peptides and proteins. We use here molecular dynamics simulations to characterise in detail the process by which nanoparticle surfaces catalyse the self- assembly of peptides into fibrillar structures. The simulation of a system of hundreds of peptides over the millisecond timescale enables us to show that the mechanism of aggregation involves a first phase in which small structurally disordered oligomers assemble onto the nanoparticle and a second phase in which they evolve into highly ordered beta-sheets as their size increases

Natural variation in sensory-motor white matter organization influences manifestations of Huntington's disease

While the HTT CAG-repeat expansion mutation causing Huntington's disease (HD) is highly correlated with the rate of pathogenesis leading to disease onset, considerable variance in age-at-onset remains unexplained. Therefore, other factors must influence the pathogenic process. We asked whether these factors were related to natural biological variation in the sensory-motor system. In 243 participants (96 premanifest and 35 manifest HD; 112 controls), sensory-motor structural MRI, tractography, resting-state fMRI, electrophysiology (including SEP amplitudes), motor score ratings, and grip force as sensory-motor performance were measured. Following individual modality analyses, we used principal component analysis (PCA) to identify patterns associated with sensory-motor performance, and manifest versus premanifest HD discrimination. We did not detect longitudinal differences over 12 months. PCA showed a pattern of loss of caudate, grey and white matter volume, cortical thickness in premotor and sensory cortex, and disturbed diffusivity in sensory-motor white matter tracts that was connected to CAG repeat length. Two further major principal components appeared in controls and HD individuals indicating that they represent natural biological variation unconnected to the HD mutation. One of these components did not influence HD while the other non-CAG-driven component of axial versus radial diffusivity contrast in white matter tracts were associated with sensory-motor performance and manifest HD. The first component reflects the expected CAG expansion effects on HD pathogenesis. One non-CAG-driven component reveals an independent influence on pathogenesis of biological variation in white matter tracts and merits further investigation to delineate the underlying mechanism and the potential it offers for disease modification

Scabies Mite Peritrophins Are Potential Targets of Human Host Innate Immunity

The gut of most invertebrates is lined by a protective layer of chitin and glycoproteins, often designated as a peritrophic matrix. Previous research suggests that it forms a barrier that may protect the midgut epithelium from abrasive food particles and pathogens. Parasitic invertebrates ingesting vertebrate plasma have evolved additional strategies to protect themselves from hazardous host molecules consumed during feeding. An important part of the immediate defense in vertebrate plasma is complement-mediated killing. The Complement system is a complex network of more than 35 proteins present in human plasma that results in killing of foreign cells including the gut epithelial cells of a feeding parasite. Recently we found that scabies mites, who feed on skin containing plasma, produce several proteins that inhibit human complement within the mite gut. The mites excrete these molecules into the upper epidermis where they presumably also inhibit complement activity. Mite gut antigens that initially trigger the complement cascade have not been identified previously. Obvious possible targets of complement attack within the mite gut could be peritrophins. Our study describes the first peritrophin identified in scabies mites and indicates a possible role in complement activation

Regional movements of the tiger shark, Galeocerdo cuvier, off northeastern Brazil: inferences regarding shark attack hazard

An abnormally high shark attack rate verified off Recife could be related to migratory behavior of tiger sharks. This situation started after the construction of the Suape port to the south of Recife. A previous study suggested that attacking sharks could be following northward currents and that they were being attracted shoreward by approaching vessels. In this scenario, such northward movement pattern could imply a higher probability of sharks accessing the littoral area of Recife after leaving Suape. Pop-up satellite archival taus were deployed on five tiger sharks caught off Recife to assess their movement patterns off northeastern Brazil. All tags transmitted from northward latitudes after 7-74 days of freedom. The shorter, soak distance between deployment and pop-up locations ranged between 33-209 km and implied minimum average speeds of 0.02-0.98 km.h(-1). Both pop-up locations and depth data suggest that tiger shark movements were conducted mostly over the continental shelf. The smaller sharks moved to deeper waters within 24 hours after releasing, but they assumed a shallower (< 50 m) vertical distribution for most of the monitoring period. While presenting the first data on tiger shark movements in the South Atlantic, this study also adds new information for the reasoning of the high shark attack rate verified in this region,State Government of Pernambuco and Petrobras (Brazil); Fundacao para a Ciencia e Tecnologia (Portugal) [MCTES/FCT/SFRH/BD/37065/2007

Prototypes for Content-Based Image Retrieval in Clinical Practice

Content-based image retrieval (CBIR) has been proposed as key technology for computer-aided diagnostics (CAD). This paper reviews the state of the art and future challenges in CBIR for CAD applied to clinical practice