Leber's hereditary optic neuropathy (LHON) pathogenic mutations induce mitochondrial-dependent apoptotic death in transmitochondrial cells incubated with galactose medium

Leber's hereditary optic neuropathy (LHON), a maternally inherited form of central vision loss, is associated with mitochondrial DNA pathogenic point mutations affecting different subunits of complex I. We here report that osteosarcoma-derived cytoplasmic hybrids (cybrid) cell lines harboring one of the three most frequent LHON pathogenic mutations, at positions 11778/ND4, 3460/ND1, and 14484/ND6, undergo cell death when galactose replaces glucose in the medium, contrary to control cybrids that maintain some growth capabilities. This is a well known way to produce a metabolic stress, forcing the cells to rely on the mitochondrial respiratory chain to produce ATP. We demonstrate that LHON cybrid cell death is apoptotic, showing chromatin condensation and nuclear DNA laddering. Moreover, we also document the mitochondrial involvement in the activation of the apoptotic cascade, as shown by the increased release of cytochrome c into the cytosol in LHON cybrid cells as compared with controls. Cybrids bearing the 3460/ND1 and 14484/ND6 mutations seemed more readily prone to undergo apoptosis as compared with the 11778/ND4 mutation. In conclusion, LHON cybrid cells forced by the reduced rate of glycolytic flux to utilize oxidative metabolism are sensitized to an apoptotic death through a mechanism involving mitochondria.     

IFN-gamma production in rabbits: behavioral and endocrine correlates

Freely interacting male rabbits were studied to establish the effect of exogenous testosterone on interferon-gamma (IFN-gamma) production in peripheral blood mononuclear cells (PBMCs) and to evaluate if this effect is related to season, social rank, plasma corticosterone and glucocorticoid receptors (GcR) in PBMCs. Dominance behavior increases after testosterone propionate (TP) administration only in rank 1 animals, while submission behavior increases after TP only in rank 4 animals, indicating a reinforcing effect of TP on the behavior. Corticosterone and IFN-gamma production are higher and GcR binding capacity is lower in spring than in autumn, suggesting that seasonal fluctuations in the immune system may be related to the pattern of secretion of immunomodulatory hormones. In autumn, corticosterone decreases after TP treatment and increases after social interaction, while GcR binding capacity decreases after TP treatment and social interaction. IFN-gamma production decreases in spring and increases in autumn after TP treatment plus social interaction, indicating that the modulating action of testosterone is related to the current immune status. The relationship between dominance, testosterone and the immune system in spring is suggested by the finding that GcR binding capacity after TP treatment is directly related to social rank, as confirmed by the positive correlation with dominance behavior frequency. The dominance index is positively correlated with GcR binding capacity and negatively with IFN-gamma production before TP treatment, indicating that high receptor activity in immunocompetent cells and low immunoreactivity could be prerequisites for dominance behavior. The immunosuppressive effect of corticosterone and the mechanism of down-regulation on GcR are confirmed by the negative correlations with IFN-gamma production and GcR binding capacity.     

3D structure of Sulfolobus solfataricus carboxypeptidase developed by molecular modeling is confirmed by site-directed mutagenesis and small angle X-ray scattering

Sulfolobus solfataricus carboxypeptidase (CPSso) is a thermostable zinc-metalloenzyme with a M(r) of 43,000. Taking into account the experimentally determined zinc content of one ion per subunit, we developed two alternative 3D models, starting from the available structures of Thermoactinomyces vulgaris carboxypeptidase (Model A) and Pseudomonas carboxypeptidase G2 (Model B). The former enzyme is monomeric and has one metal ion in the active site, while the latter is dimeric and has two bound zinc ions. The two models were computed by exploiting the structural alignment of the one zinc- with the two zinc-containing active sites of the two templates, and with a threading procedure. Both computed structures resembled the respective template, with only one bound zinc with tetrahedric coordination in the active site. With these models, two different quaternary structures can be modeled: one using Model A with a hexameric symmetry, the other from Model B with a tetrameric symmetry. Mutagenesis experiments directed toward the residues putatively involved in metal chelation in either of the models disproved Model A and supported Model B, in which the metal-binding site comprises His(108), Asp(109), and His(168). We also identified Glu(142) as the acidic residue interacting with the water molecule occupying the fourth chelation site. Furthermore, the overall fold and the oligomeric structure of the molecule was validated by small angle x-ray scattering (SAXS). An ab initio original approach was used to reconstruct the shape of the CPSso in solution from the experimental curves. The results clearly support a tetrameric structure. The Monte Carlo method was then used to compare the crystallographic coordinates of the possible quaternary structures for CPSso with the SAXS profiles. The fitting procedure showed that only the model built using the Pseudomonas carboxypeptidase G2 structure as a template fitted the experimental data.     

Convenient preparation of L-arabino-hexos-5-ulose derivatives from lactose

2,6-di-O-benzyl- (9), 2-O-benzyl-3,4-O-isopropylidene- (19), and 2-O-benzyl-6-O-m-chlorobenzoyl-L-arabino-hexos-5-ulose (20) have been prepared using 4'-deoxy-4'-eno- and 6'-deoxy-5'-eno lactose dimethyl acetal derivatives 7 and 14 as key intermediates. The synthesis of enol ethers 7 and 14 has been performed with good yields by base-promoted elimination of acetone or p-toluenesulfonic acid from 2',6'-di-O-benzyl-, and 6'-O-p-toluenesulfonyl-2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal, respectively. The epoxidation with MCPBA of 7 and 14 in methanol or dichloromethane furnishes C-5'-methoxy and C-5'-m-chlorobenzoyloxy derivatives, easily transformed with good yields into L-arabino 5-ketoaldohexoses 9, 19 and 20.     

Apoptosis meets proteasome, an invaluable therapeutic target of anticancer drugs

This report reviews the current status of extensive efforts directed towards the interpretation of crosstalk between apoptosis and proteasome to understanding the molecular mechanism of anticancer agents targeting proteasome, with particular focus on MG132 and PS-341. The discovery that all cancer cells have retained the apoptotic death program has offered to the researchers new biochemical targets to design anticancer drugs. Moreover, the demonstration that proteasome inhibition induces apoptosis and sensitizes cancer cells to traditional tumoricidal agents has proposed the proteasome as an attractive target for development of new anticancer drugs. Since then, a number of both naturally occurring and synthetic inhibitors of the proteasome have been identified. The best characterized and most widely used inhibitors of the proteasome are the peptide aldehydes; among these MG132, due to its broad spectrum of action, low cost and rapid reversibility of action, still remains the first choice to study proteasome function in cell and tissue cultures. Recently, a very potent new class of selective and reversible proteasome inhibitors which contains an inhibitory boronate group has been described. PS-341 represent the first of this promising class of agents that could have application in cancer therapy and it is the only that has progressed to clinical trials.     

The Klebsiella pneumoniae wabG gene: role in biosynthesis of the core lipopolysaccharide and virulence

To determine the function of the wabG gene in the biosynthesis of the core lipopolysaccharide (LPS) of Klebsiella pneumoniae, we constructed wabG nonpolar mutants. Data obtained from the comparative chemical and structural analysis of LPS samples obtained from the wild type, the mutant strain, and the complemented mutant demonstrated that the wabG gene is involved in attachment to alpha-L-glycero-D-manno-heptopyranose II (L,D-HeppII) at the O-3 position of an alpha-D-galactopyranosyluronic acid (alpha-D-GalAp) residue. K. pneumoniae nonpolar wabG mutants were devoid of the cell-attached capsular polysaccharide but were still able to produce capsular polysaccharide. Similar results were obtained with K. pneumoniae nonpolar waaC and waaF mutants, which produce shorter LPS core molecules than do wabG mutants. Other outer core K. pneumoniae nonpolar mutants in the waa gene cluster were encapsulated. K. pneumoniae waaC, waaF, and wabG mutants were avirulent when tested in different animal models. Furthermore, these mutants were more sensitive to some hydrophobic compounds than the wild-type strains. All these characteristics were rescued by reintroduction of the waaC, waaF, and wabG genes from K. pneumoniae.