[en] This book provides in-depth coverage of the current thinking and the latest developments in the field of calcitonins and calcitonin-gene related peptides (CGRP). (Auth.)

[en] Amyloid formation and aberrant protein aggregation have been implicated in more than 15 different human diseases and an even wider range of proteins form amyloid in vitro. From a structural perspective the proteins which form amyloid can be divided into two classes: those which adopt a compact globular fold and must presumably at least partially unfold to form amyloid and those which are unstructured in their monomeric state. Important examples of the latter include the Aβ peptide of Alzheimer's disease, atrial natriuretic factor, calcitonin, pro-calcitonin, islet amyloid polypeptide (IAPP, amylin), α-synuclein and the medin polypeptide. The kinetics of amyloid assembly are complex and typically involve a lag phase during which little or no fibril material is formed, followed by a rapid growth stage leading to the β-sheet-rich amyloid structure. Increasing evidence suggests that some natively unfolded polypeptides populate a helical intermediate during the lag phase. We propose a model in which early oligomerization is linked to helix formation and is promoted by helix–helix association. Recent work has highlighted the potential importance of polypeptide membrane interactions in amyloid formation and helical intermediates appear to play an important role here as well. Characterization of helical intermediates is experimentally challenging but new spectroscopic techniques are emerging which hold considerable promise and even have the potential to provide residue specific information

[en] The human islet amyloid polypeptide (hIAPP) co-operates with insulin to maintain glycemic balance. It also constitutes the amyloid plaques that aggregate in the pancreas of type-II diabetic patients. We have performed extensive in silico investigations to analyse the structural landscape of monomeric hIAPP, which is presumed to be intrinsically disordered. For this, we construct from first principles a highly predictive energy function that describes a monomeric hIAPP observed in a nuclear magnetic resonance experiment, as a local energy minimum. We subject our theoretical model of hIAPP to repeated heating and cooling simulations, back and forth between a high temperature regime where the conformation resembles a random walker and a low temperature limit where no thermal motions prevail. We find that the final low temperature conformations display a high level of degeneracy, in a manner which is fully in line with the presumed intrinsically disordered character of hIAPP. In particular, we identify an isolated family of α-helical conformations that might cause the transition to amyloidosis, by nucleation

[en] Receptor activator of nuclear factor κB-ligand (RANKL) transduces a differentiation signal appropriate to osteoclasts likely through induction a receptor homotrimer; however, biological importance of RANK-trimerizarion is unknown. To address the signaling mechanism of the RANK receptor, we analyzed the effect of two different types of homodimer inducers RANK-TM-FKBP36v and hEpoR-RANK-TM on osteoclastogenesis. Dimerizing component FKBP36v or extracellular portion of human erythropoietin receptor (hEpoR) was fused to RANK lacking the extracellular domain, and the dimerization of this fusion protein was induced by addition of the chemical inducer of dimerization AP20187 or erythropoietin, respectively. Such treatment resulted in induction of TRAP-activity, a marker of osteoclast in a dose dependent manner, with an efficiency equivalent to that of induction by RANKL. However, dimerized-RANK-induced osteoclasts showed relatively low levels of multinucleation, pit forming activity, and expression of calcitonin receptor and cathepsin K, compared with osteoclasts which were induced in the presence of RANKL. As expression of nuclear factor of activated T cells 1 (NFATc1) was also reduced in dimerized-RANK-induced osteoclasts, RANK oligomerization by RANKL is a critical event to generate fully matured osteoclasts through upregulation of NFATc1

[en] Endothelial dysfunction (ED) is a well-recognized instigator of cardiovascular diseases and develops in chronic kidney disease (CKD) with high rate. Recent studies have implicated that leptin is associated with endothelial dysfunction. We investigated the relationship between leptin and markers of ED in CKD patients and how leptin contributed to endothelial damage. 140 CKD patients and 140 healthy subjects were studied. Serum leptin levels were significantly higher in CKD than in controls and displayed significantly positive association with the increase levels of sICAM-1 and sVCAM-1 but negative correlation with flow-mediated dilatation (FMD) reduction in patients. Our in vitro study demonstrated that leptin induced overexpression of ICAM-1 and VCAM-1, led to f-actin reorganization and vinculin assembly, increased endothelial monolayer permeability for FITC-dextran, and accelerated endothelial cell migration; these changes were markedly reversed when the cells were transfected with AKT or β-catenin shRNA vectors. Notably, high leptin resulted in hyper-phosphorylation of AKT and GSK3β, along with nuclear accumulation of β-catenin. In conclusion, serum leptin was elevated in CKD patients and it might contribute to endothelial dysfunction by disarrangement of f-actin cytoskeleton via a mechanism involving the AKT/GSK3β and β-catenin pathway. - Highlights: • Serum leptin was elevated in CKD patients and it was associated with endothelial dysfunction. • Leptin induced endothelial dysfunction by remodeling cytoskeleton in HUVECs. • Leptin promoted endothelial dysfunction via a mechanism involving the AKT/GSK3β and β-catenin signals.

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No abstract available

[en] We report on the mechanical characterization of individual mature amyloid fibrils by atomic force microscopy (AFM) and AFM-based single-molecule force spectroscopy (SMFS). These self-assembling materials, formed from the 29-residue amphiphatic peptide hormone glucagon, were found to display a reversible elastic behaviour. Based on AFM morphology and SMFS studies, we suggest that the observed elasticity is due to a force-induced conformational transition which is reversible due to the β-helical conformation of protofibrils, allowing a high degree of extension. The elastic properties of such mature fibrils contribute to their high stability, suggesting that the internal hydrophobic interactions of amyloid fibrils are likely to be of fundamental importance in the assembly of amyloid fibrils and therefore for the understanding of the progression of their associated pathogenic disorders. In addition, such biological amyloid fibril structures with highly stable mechanical properties can potentially be used to produce nanofibres (nanowires) that may be suitable for nanotechnological applications

[en] Proteases belong to an important class of enzymes known as hydrolases and catalyze hydrolysis of proteins. They act primarily to degrade proteins that are used for energy production and as biosynthetic precursors. In the following study, protease produced from Aspergillus terreus was found to be thermo stable and included in the category of alkaline serine and metallo protease. During partial purification, presence of enzyme in 60% (NH/sub 4/)/sub 2/SO/sub 4/ indicated small molecular weight polypeptide; later purification with Sephadex G-75 fractionation yielded a single proteolytic active molecule. At final purification step, the increase in specific activity of the enzyme was 7.5 fold with 23% yield. SDS-PAGE analysis revealed that alkaline protease of Aspergillus terreus is a monomer with approximate molecular weight of 35 kDa. Optimum pH for protease activity was found in the range of 7.5-11.0 (maximum at pH 8.5), thus apparently classified as an alkaline protease. The enzyme was thermo stable towards high temperature (60 deg. C), however it denatured irreversibly at 70 deg. C showing 80% loss of activity. The maximum proteolytic activity was found at 40 deg. C. The enzyme was effectively inhibited by PMSF, EDTA and urea whereas iodoacetamide and thiourea did not result in any loss in activity while cysteine was found to be activator molecule. The study with metal ions Mg/sup +2/, Mn/sup +2/ and Fe/sup +3/ (1 mM each) showed minute stimulatory effects on enzyme activity. Co/sup +2/ and Ca/sup +2/ (1 mM) had neither excitatory nor inhibitory effect while Hg/sup +2/ and Cu/sup +2/ (1 mM) slightly reduced the enzyme activity. (author)

[en] Pentagastrin (t-boc-β-Ala-Trp-Met-Asp-Phe-NH₂) is a diagnostic agent for evaluating gastric acid secretory function. The conformation of this pentapeptide has been investigated by NMR and perturbative configuration interaction using localized orbitals (PCILO) methods. Two conformations have been predicted by PCILO calculations. The first has an extended structure at the C-terminal and is folded about the N-terminal, with a γ-bend at Met. In addition, the CO and NH groups of β-Ala are involved in intramolecular hydrogen bonding. The second conformation is nearly fully extended, except about the β-Ala residue where the above mentioned intramolecular hydrogen bond again appears. The first conformation is only about 1.7 kcal/mol lower in energy as compared to the second one. The solution conformation as determined by NMR techniques such as 2-D-COSY, NOESY, ROESY, ³J_NHα coupling constants and temperature coefficients of NH resonance is predominantly extended. The solution conformation of the peptide in lipid bilayers was found to be an extended one. Based on these findings, the biologically active conformation of pentagastrin has been deduced. (author). 22 refs., 4 figs., 3 tabs