Novel sulfur and selenium containing bis-α-amino acids from 4-hydroxyproline

The synthesis of new substituted prolines carrying at C-4 a second α-amino acid residue is reported. The amino acid, l-cysteine or l-selenocysteine, is linked to the proline ring through the sulfur or the selenium atom, respectively. The products were prepared with different stereochemistry at C-4, in few and clean high-yielding steps, with suitable protections for solid phase applications. The introduction of both sulfur and selenium atoms at C-4 of the proline ring seems to enhance significantly the cis geometry at the prolyl amide bond.     

Expression of pro-inflammatory TACE-TNF-α-amphiregulin axis in Sjögren’s syndrome salivary glands

The tumor-necrosis-factor-converting-enzyme (TACE)-TNF-α-Amphiregulin (AREG) axis plays an important pathogenic role in inflammatory and autoimmune disorders. However, the pathological roles of these proteins in the chronic autoimmune disease Sjögren’s syndrome (SS) remain to be elucidated. It is known that the TACE–AREG axis is clearly part of a larger cascade of signals that starts with the activation of Furin, responsible for maturation of TACE that, in turn, determines the production of active TNF-α, directly involved in the up-regulation of AREG expression. This study showed that Furin, TACE, TNF-α, and AREG proteins, detected in acinar and ductal cells of human salivary glands from SS patients, increased remarkably in comparison with biopsies of labial salivary glands from healthy controls. The changes in Furin, TACE, TNF- α, and AREG proteins’ level detected in salivary glands biopsies of SS patients could be responsible for pro-inflammatory cytokines overexpression characterizing Sjögren’s syndrome.     

Recognition of Smac-mimetic compounds by the BIR domain of cIAP1

Inhibitor of apoptosis proteins (IAPs) are negative regulators of apoptosis. As IAPs are overexpressed in many tumors, where they confer chemoresistance, small molecules inactivating IAPs have been proposed as anticancer agents. Accordingly, a number of IAP-binding pro-apoptotic compounds that mimic the sequence corresponding to the N-terminal tetrapeptide of Smac/DIABLO, the natural endogenous IAPs inhibitor, have been developed. Here, we report the crystal structures of the BIR3 domain of cIAP1 in complex with Smac037, a Smac-mimetic known to bind potently to the XIAP-BIR3 domain and to induce degradation of cIAP1, and in complex with the novel Smac-mimetic compound Smac066. Thermal stability and fluorescence polarization assays show the stabilizing effect and the high affinity of both Smac037 and Smac066 for cIAP1- and cIAP2-BIR3 domains.     

Phosphorylation pattern of the NDUFS4 subunit of complex I of the mammalian respiratory chain

The NDUFS4 subunit of complex I of the mammalian respiratory chain has a fully conserved carboxy-terminus with a canonical RVSTK phosphorylation site. Immunochemical analysis with specific antibodies shows that the serine in this site of the protein is natively present in complex I in both the phosphorylated and non-phosphorylated state. Two-dimensional IEF/SDS–PAGE electrophoresis, ³²P labelling and immunodetection show that “in vitro” PKA phosphorylates the serine in the C-terminus of the NDUFS4 subunit in isolated bovine complex I. ³²P labelling and TLC phosphoaminoacid mapping show that PKA phosphorylates serine and threonine residues in the purified heterologous human NDUFS4 protein.     

Acute metal stress in Populus tremula×P. alba (717‐1B4 genotype): Leaf and cambial proteome changes induced by cadmium2+

The comprehension of metal homeostasis in plants requires the identification of molecular markers linked to stress tolerance. Proteomic changes in leaves and cambial zone of Populus tremula×P. alba (717‐1B4 genotype) were analyzed after 61 days of exposure to cadmium (Cd) 360 mg/kg soil dry weight in pot‐soil cultures. The treatment led to an acute Cd stress with a reduction of growth and photosynthesis. Cd stress induced changes in the display of 120 spots for leaf tissue and 153 spots for the cambial zone. It involved a reduced photosynthesis, resulting in a profound reorganisation of carbon and carbohydrate metabolisms in both tissues. Cambial cells underwent stress from the Cd actually present inside the tissue but also a deprivation of photosynthates caused by leaf stress. An important tissue specificity of the response was observed, according to the differences in cell structures and functions.     

Common basis for the mechanism of metallo and non-metallo KDO8P synthases

The three-dimensional structures of metal and non-metal enzymes that catalyze the same reaction are often quite different, a clear indication of convergent evolution. However, there are interesting cases in which the same scaffold supports both a metal and a non-metal catalyzed reaction. One of these is 3-deoxy-D-manno-octulosonate 8-phosphate (KDO8P) synthase (KDO8PS), a bacterial enzyme that catalyzes the synthesis of KDO8P and inorganic phosphate (P_i) from phosphoenolpyruvate (PEP), arabinose 5-phosphate (A5P), and water. This reaction is one of the key steps in the biosynthesis of bacterial endotoxins. The evolutionary tree of KDO8PS is evenly divided between metal and non-metal forms, both having essentially identical structures. Mutagenesis and crystallographic studies suggest that one or two residues at most determine whether or not KDO8PS requires a metal for function, a clear example of “minimalist evolution”. Quantum mechanical/molecular mechanical (QM/MM) simulations of both the enzymatic and non-enzymatic synthesis of KDO8P have revealed the mechanism underlying the switch between metal and non-metal dependent catalysis. The principle emerging from these studies is that this conversion is possible in KDO8PS because the metal is not involved in an activation process, but primarily contributes to orienting properly the reactants to lower the activation energy, an action easily mimicked by amino acid side-chains.     

Aluminium and iron air pollution near an iron casting and aluminium foundry in Turin district (Italy)

This work reports the results of an environmental survey carried out in an industrial area in the Province of Turin: its main aim is to assess the levels of iron and aluminium in the outside air during the period from July to September to assess the influence of industrial activity (a cast-iron and aluminium foundry) which is interrupted during the month of August, on the level of metals present in the air. Conducting the analysis during this period of time made it possible to avoid the confounding effect of pollution due to domestic central heating. The measurements were taken from nine areas at different distances from the foundry in the area and according to the direction of the prevailing winds, as deduced from the historical data. The results of this survey show a statistically significant difference in iron and aluminium levels in the outside air in the geographic areas between the two main periods examined: during August (no foundry activity) v/s July-September (foundry activity). The values recorded are: Aluminium 0.4+/-0.45 microg/m(3) v/s 1.12+/-1.29 microg/m(3) (p<0.0001); Iron 0.95+/-0.56 microg/m(3) v/s 1.6+/-1.0 microg/m(3) (p<0.0001). There were no statistically significant differences between the nine sampling points from the point of view of the sampling sites, climate conditions and wind directions. We found no correlation with car traffic, in terms of the number of vehicles, and metals. The values of iron tended to be higher in the areas farther away from the foundry site in the areas located along the path of the prevailing winds.     

Analysis of compensatory beta-cell response in mice with combined mutations of Insr and Irs2

Type 2 diabetes results from impaired insulin action and beta-cell dysfunction. There are at least two components to beta-cell dysfunction: impaired insulin secretion and decreased beta-cell mass. To analyze how these two variables contribute to the progressive deterioration of metabolic control seen in diabetes, we asked whether mice with impaired beta-cell growth due to Irs2 ablation would be able to mount a compensatory response in the background of insulin resistance caused by Insr haploinsufficiency. As previously reported, approximately 70% of mice with combined Insr and Irs2 mutations developed diabetes as a consequence of markedly decreased beta-cell mass. In the initial phases of the disease, we observed a robust increase in circulating insulin levels, even as beta-cell mass gradually declined, indicating that replication-defective beta-cells compensate for insulin resistance by increasing insulin secretion. These data provide further evidence for a heterogeneous beta-cell response to insulin resistance, in which compensation can be temporarily achieved by increasing function when mass is limited. The eventual failure of compensatory insulin secretion suggests that a comprehensive treatment of beta-cell dysfunction in type 2 diabetes should positively affect both aspects of beta-cell physiology.