CRIM1 complexes with ß-catenin and cadherins, stabilizes cell-cell junctions and is critical for neural morphogenesis

In multicellular organisms, morphogenesis is a highly coordinated process that requires dynamically regulated adhesion between cells. An excellent example of cellular morphogenesis is the formation of the neural tube from the flattened epithelium of the neural plate. Cysteine-rich motor neuron protein 1 (CRIM1) is a single-pass (type 1) transmembrane protein that is expressed in neural structures beginning at the neural plate stage. In the frog Xenopus laevis, loss of function studies using CRIM1 antisense morpholino oligonucleotides resulted in a failure of neural development. The CRIM1 knockdown phenotype was, in some cases, mild and resulted in perturbed neural fold morphogenesis. In severely affected embryos there was a dramatic failure of cell adhesion in the neural plate and complete absence of neural structures subsequently. Investigation of the mechanism of CRIM1 function revealed that it can form complexes with ?-catenin and cadherins, albeit indirectly, via the cytosolic domain. Consistent with this, CRIM1 knockdown resulted in diminished levels of cadherins and ?-catenin in junctional complexes in the neural plate. We conclude that CRIM1 is critical for cell-cell adhesion during neural development because it is required for the function of cadherin-dependent junctions.     

Irreversible gelation of thermally unfolded proteins: structural and mechanical properties of lysozyme aggregates

The formation of protein aggregates is important in many fields of life science and technology. The morphological and mechanical properties of protein solutions depend upon the molecular conformation and thermodynamic and environmental conditions. Non-native or unfolded proteins may be kinetically trapped into irreversible aggregates and undergo precipitation or gelation. Here, we study the thermal aggregation of lysozyme in neutral solutions. We characterise the irreversible unfolding of lysozyme by differential scanning calorimetry. The structural properties of aggregates and their mechanisms of formation with the eventual gelation are studied at high temperature by spectroscopic, rheological and scattering techniques. The experiments show that irreversible micron-sized aggregates are organised into larger clusters according to a classical mechanism of diffusion and coagulation, which leads to a percolative transition at high concentrations. At a smaller length scale, optical and atomic force microscopy images reveal the existence of compact aggregates, which are the origin of the aggregation irreversibility.     

Small molecules interacting with α-synuclein: antiaggregating and cytoprotective properties

Curcumin, a dietary polyphenol, has shown a potential to act on the symptoms of neurodegenerative disorders, including Alzheimer’s and Parkinson’s diseases, as a consequence of its antioxidant, anti-inflammatory and anti-protein aggregation properties. Unfortunately, curcumin undergoes rapid degradation at physiological pH into ferulic acid, vanillin and dehydrozingerone, making it an unlikely drug candidate. Here, we evaluated the ability of some curcumin by-products: dehydrozingerone (1), its O-methyl derivative (2), zingerone (3), and their biphenyl analogues (4–6) to interact with α-synuclein (AS), using CD and fluorescence spectroscopy. In addition, the antioxidant properties and the cytoprotective effects in rat pheochromocytoma (PC12) cells prior to intoxication with H₂O₂, MPP+ and MnCl₂ were examined while the Congo red assay was used to evaluate the ability of these compounds to prevent aggregation of AS. We found that the biphenyl zingerone analogue (6) interacts with high affinity with AS and also displays the best antioxidant properties while the biphenyl analogues of dehydrozingerone (4) and of O-methyl-dehydrozingerone (5) are able to partially inhibit the aggregation process of AS, suggesting the potential role of a hydroxylated biphenyl scaffold in the design of AS aggregation inhibitors.     

Ascorbic acid as a factor controlling "in vivo" its biosynthetic pathway

The capacity of ascorbic acid biosynthesis in potato tuber tissue is closely correlated with the ascorbic acid content of the cells: the lower the endogenous content of ascorbic acid, the greater its biosynthesis. At the highest level of ascorbic acid found in the cells, the biosynthetic capacity is virtually zero. In these conditions, adding glucose (the first precursor of ascorbic acid) has no effect whatsoever, whereas adding galactono-gamma-lactone (the last precursor) induces a high rate of ascorbic acid synthesis. It is suggested that AA biosynthesis is subject to a regulatory mechanism "in vivo" which controls an initial step in the biosynthetic pathway. The last step in this pathway, catalyzed by galactone oxidase, is never blocked and, moreover, its activity is greater than that of the preceding steps.     

Different patterns of expression of five neuropeptides in the adrenal gland and kidney of two species of frog

The aim of this study was to demonstrate in the adrenocortical and renal tissues of two species of frog, Rana italica and Rana esculenta, the presence and distribution of five neuropeptides: atrial natriuretic peptide (ANP), Leu-enkephalin (Leu-ENK), neuropeptide Y (NPY), substance P (SP) and vasoactive intestinal peptide (VIP).In anurans, the adrenal medulla is the site for the synthesis, storage and secretion of not only catecholamines but also various peptides. These peptides should not be regarded only as neurotransmitters or modulators for the secretion of catecholamines, but also as hormonal substances that induce systemic effects.All the peptides studied (ANP, Leu-ENK, NPY, SP and VIP) are present in both organs. However, different patterns of expression were observed for some of the peptides in two frogs.Immunopositivity to ANP was found in small clusters of chromaffin cells in both frogs whereas a clear strong positivity was present only in Rana esculenta kidney. Large clusters of chromaffin cells were immunoreactive to Leu-ENK in Rana italica but there were approximately 25% fewer compared to the positive cells present in Rana esculenta. Epithelial cells of renal tubules showed strong immunopositivity to Leu-ENK in Rana esculenta but not in Rana italica. A large number of adrenal cells (70–80%) were immunoreactive to NPY in Rana italica, while in Rana esculenta this peptide was localized in small clusters of chromaffin cells. Both frogs showed many NPY-positive cells in kidney. Many chromaffin cells were found positive to SP and VIP. A strong positivity was also observed in kidney in both frogs. These observations suggest a possible role of these peptides in the control of the physiological functions of adrenal glands and kidney of the two species of frogs studied.     

Ubiquinol and a Coenzyme Q Reducing System Protect Platelet Mitochondrial Function of Transfusional Buffy Coats from Oxidative Stress

The conditions under which Coenzyme Q (CoQ) may protect platelet mitochondrial function of transfusional buffy coats from aging and from induced oxidative stress were investigated. The Pasteur effect, i.e. the enhancement of lactate production after inhibition of mitochondrial respiratory chain, was exploited as a marker of mitochondrial function as it allows to calculate the ratio of mitochondrial ATP to glycolytic ATP. Reduced CoQ 10 improves platelet mitochondrial function of transfusional buffy coats and protects the cells from induced oxidative stress. Oxidized CoQ is usually less effective, despite the presence, shown for the first time in this study, of quinone reductase activities in the platelet plasma membranes. The addition of a CoQ reducing system to platelets is effective in enhancing the protection of platelet mitochondrial function from the oxidative stress. The results support on one hand a possibility of protection of mitochondrial function in aging by exogenous CoQ intake, on the other a possible application in protection of transfusional buffy coats from storage conditions and oxidative deterioration.