The insect antimicrobial peptide, L-pyrrhocoricin, binds to and stimulates the ATPase activity of both wild-type and lidless DnaK

Recent reports have indicated that insect antimicrobial peptides kill bacteria by inhibiting the molecular chaperone DnaK. It was proposed that the antimicrobial peptide, all-L-pyrrhocoricin (L-PYR), binds to two sites on DnaK, the conventional substrate-binding site and the multi-helical C-terminal lid, and that inhibition of DnaK comes about from the lid mode of binding. In this report, we show using two different assays that L-PYR binds to and stimulates the ATPase activity of both wild-type and a lidless variant of DnaK. Our study shows that L-PYR interacts with DnaK much like the all-L NR (NRLLLTG) peptide, which is known to bind in the conventional substrate-binding site of DnaK. L-PYR antimicrobial activity is thus a consequence of the competitive inhibition of bacterial DnaK.     

alpha-Synuclein, oxidative stress and apoptosis from the perspective of a yeast model of Parkinson's disease

The neuronal protein α-synuclein (α-syn) has been suggested to be one of the factors linked to Parkinson's disease (PD). Several organisms, including the rat, mouse, worm, and fruit fly, are being used to study α-syn pathobiology. A new model organism was recently added to this armamentarium: the budding yeast Saccharomyces cerevisiae . The yeast system recapitulates many of the findings made with higher eukaryotes. For example, yeast cells expressing α-syn accumulate lipid droplets, have vacuolar/lysosomal defects, and exhibit markers of apoptosis, including the externalization of phosphatidylserine, the release of cytochrome c , and the accumulation of reactive oxygen species. This MiniReview focuses on the mechanisms by which α-syn induces oxidative stress and the mechanisms by which yeast cells respond to this stress. Three classes of therapeutics are discussed.     

Nebulin regulates thin filament length, contractility, and Z-disk structure in vivo

The precise assembly of the highly organized filament systems found in muscle is critically important for its function. It has been hypothesized that nebulin, a giant filamentous protein extending along the entire length of the thin filament, provides a blueprint for muscle thin filament assembly. To test this hypothesis, we generated a KO mouse model to investigate nebulin functions in vivo. Nebulin KO mice assemble thin filaments of reduced lengths and approximately 15% of their Z-disks are abnormally wide. Our data demonstrate that nebulin functions in vivo as a molecular ruler by specifying pointed- and barbed-end thin filament capping. Consistent with the shorter thin filament length of nebulin deficient mice, maximal active tension was significantly reduced in KO animals. Phenotypically, the murine model recapitulates human nemaline myopathy (NM), that is, the formation of nemaline rods combined with severe skeletal muscle weakness. The myopathic changes in the nebulin KO model include depressed contractility, loss of myopalladin from the Z-disk, and dysregulation of genes involved in calcium homeostasis and glycogen metabolism; features potentially relevant for understanding human NM.     

Mice lacking the nuclear pore complex protein ALADIN show female infertility but fail to develop a phenotype resembling human triple A syndrome

Triple A syndrome is a human autosomal recessive disorder characterized by adrenal insufficiency, achalasia, alacrima, and neurological abnormalities affecting the central, peripheral, and autonomic nervous systems. In humans, this disease is caused by mutations in the AAAS gene, which encodes ALADIN, a protein that belongs to the family of WD-repeat proteins and localizes to nuclear pore complexes. To analyze the function of the gene in the context of the whole organism and in an attempt to obtain an animal model for human triple A syndrome, we generated mice lacking a functional Aaas gene. The Aaas-/- animals were found to be externally indistinguishable from their wild-type littermates, although their body weight was on the average lower than that of wild-type mice. Histological analysis of various tissues failed to reveal any differences between Aaas-/- and wild-type mice. Aaas-/- mice exhibit unexpectedly mild abnormal behavior and only minor neurological deficits. Our data show that the lack of ALADIN in mice does not lead to a triple A syndrome-like disease. Thus, in mice either the function of ALADIN differs from that in humans, its loss can be readily compensated for, or additional factors, such as environmental conditions or genetic modifiers, contribute to the disease.     

Generation of cloned transgenic pigs rich in omega-3 fatty acids

Meat products are generally low in omega-3 (n-3) fatty acids, which are beneficial to human health. We describe the generation of cloned pigs that express a humanized Caenorhabditis elegans gene, fat-1, encoding an n-3 fatty acid desaturase. The hfat-1 transgenic pigs produce high levels of n-3 fatty acids from n-6 analogs, and their tissues have a significantly reduced ratio of n-6/n-3 fatty acids (P < 0.001).     

Assessment of energy requirement for the retinal arterial network in normal and hypertensive subjects

The retinal arterial network structure can be altered by systemic diseases such as hypertension and diabetes. In order to compare the energy requirement for maintaining retinal blood flow and vessel wall metabolism between normal and hypertensive subjects, 3D hypothetical models of a representative retinal arterial bifurcation were constructed based on topological features derived from retinal images. Computational analysis of blood flow was performed, which accounted for the non-Newtonian rheological properties of blood and peripheral vessel resistance. The results suggested that the rate of energy required to maintain the blood flow and wall metabolism is much lower for normal subjects than for hypertensives, with the latter requiring 49.2% more energy for an entire retinal arteriolar tree. Among the several morphological factors, length-to-diameter ratio was found to have the most significant influence on the overall energy requirement.     

Sensitive detection of idiotypic platelet-reactive alloantibodies by an electrical protein chip

To prevent and treat immune-mediated platelet disorders (e.g. neonatal allo-immune thrombocytopenia and platelet transfusion refractoriness) the causative idiotypic platelet-reactive antibodies have to be detected with high sensitivity and specificity. The "Monoclonal Antibody Immobilization Platelet Assay" (MAIPA) is the diagnostic gold standard for immunotyping sera with respect to alloantibodies against human platelet antigens (HPA). However, it is labor-intensive and time-consuming. In this work, an automated protein chip assay (enzyme-linked sandwich immunoassay) based on interdigitated gold microelectrodes in combination with an electrical read-out system was developed and optimized. For this purpose, specific capture antibodies were immobilized on the gold electrodes. The binding of the target is detected via an enzyme-labeled detection antibody by a redox-recycling process that corresponds to the amount of bound target molecule. With this electrical chip assay it is possible to detect antibodies against HPA-1a, HPA-5b and HLA with high sensitivity and specificity in less than half the duration of the MAIPA protocol with similar intra- and interassay variance.