Drosophila caspase transduces Shaggy/GSK-3beta kinase activity in neural precursor development

Caspases are well known for their role in the execution of apoptotic programs, in which they cleave specific target proteins, leading to the elimination of cells, and for their role in cytokine maturation. In this study, we identified a novel substrate, which, through cleavage by caspases, can regulate Drosophila neural precursor development. Shaggy (Sgg)46 protein, an isoform encoded by the sgg gene and essential for the negative regulation of Wingless signaling, is cleaved by the Dark-dependent caspase. This cleavage converts it to an active kinase, which contributes to the formation of neural precursor (sensory organ precursor (SOP)) cells. Our evidence suggests that caspase regulation of the wingless pathway is not associated with apoptotic cell death. These results imply a novel role for caspases in modulating cell signaling pathways through substrate cleavage in neural precursor development.     

Three ent-secoaromadendrane-type sesquiterpene hemiacetals and a bicyclogermacrene from Plagiochila ovalifolia and Plagiochila yokogurensis

A new ent-secoaromadendrane-type sesquiterpene hemiacetal, plagiochiline G, was isolated from Plagiochila ovalifolia. Four new ent-sesquiterpene hemiacetals, plagiochiline H and I, and two pungent methoxyplagiochilines A₁, A₂ and non-pungent methoxyplagiochiline C were also isolated from P. yokogurensis. The methoxylated plagiochilines A₁, A₂ and C were derived from the plagiochilines A and C during the extraction procedure. A new germacrene, ent-3α-acetoxybicyclogermacrene, ent-maaliol and the previously known ent- aromadendrane-type sesquiterpenes have been obtained from P. yokogurensis. The structures of the new compounds were elucidated by ¹H NMR spectral data and by chemical correlation.     

Properties of ionic channels formed by the antibiotic syringomycin E in lipid bilayers: dependence on the electrolyte concentration in the bathing solution.

Using the planar lipid bilayer technique, organization of ionic channels formed by the lipodepsipeptide antibiotic syringomycin E applied to one (cis) side of a lipid bilayer was studied. Low concentrations of NaCl (0.01-0.1 M) induced the opening and closing of two types of channels - "small" and "large". The large channels had single channel conductances approximately six times greater than those of the small channels. An increase in the NaCl concentration (0.6-1.0 M) decreased almost completely the chance to reveal the large channels. Although the syringomycin channels exhibited the anion selectivity within the entire range of NaCl concentrations in the bathing solutions (from 0.001 to 1.0 M) whereas the concentration gradients across the bilayers were 2 and 4, the transfer numbers for Cl-decreased with an increase in the mean NaCl concentration (from 0.83 for 0.005 M to 0.70 for 0.5 M). Moreover, at each mean value of NaCl concentration, all conductance levels had the same ion selectivity (identical reversal potential). These results suggest that at low NaCl concentrations the large channels are clusters of small channels which synchronously open and close, while at high electrolyte concentrations the screening of the charged groups responsible for channel interactions prevents the cluster formation. A new theoretical approach for the estimation of the channel radius and the number of elementary charges located at its inner surface (based on the experimental curve of the dependence of transfer number on the NaCl concentration) was developed. Based on this theoretical approach, the channel radius equal to 1 nm and one elementary charge located at its inner surface were obtained.     

Antipeptide Antibodies That Can Distinguish Specific Subunit Polypeptides of Glutamine Synthetase from Bean (Phaseolus vulgaris L.)

The amino acid sequences of the β and γ subunit polypeptides of glutamine synthetase from bean (Phaseolus vulgaris L.) root nodules are very similar. However, there are small regions within the sequences that are significantly different between the two polypeptides. The sequences between amino acids 2 and 9 and between 264 and 274 are examples. Three peptides (γ_2-9, γ_264-274, and β_264-274) corresponding to these sequences were synthesized. Antibodies against these peptides were raised in rabbits and purified with corresponding peptide-Sepharose affinity chromatography. Western blot analysis of polyacrylamide gel electrophoresis of bean nodule proteins demonstrated that the anti-β_264-274 antibodies reacted specifically with the β polypeptide and the anti-γ_264-274 and anti-γ_2-9 antibodies reacted specifically with the γ polypeptide of the native and denatured glutamine synthetase. These results showed the feasibility of using synthetic peptides in developing antibodies that are capable of distinguishing proteins with similar primary structures.     

Correlation between structure and temperature in prokaryotic metabolic networks

Background  

In recent years, an extensive characterization of network structures has been made in an effort to elucidate design principles of metabolic networks, providing valuable insights into the functional organization and the evolutionary history of organisms. However, previous analyses have not discussed the effects of environmental factors (i.e., exogenous forces) in shaping network structures. In this work, we investigate the effect of temperature, which is one of the environmental factors that may have contributed to shaping structures of metabolic networks.     

Suppression of mitogen-induced lymphocyte proliferation by syringomycin-E

Abstract Syringomycin E (SR-E) is low molecular weight bacterial lipodepsipeptide with antifungal properties. Owing to immunosuppressive activities of such compounds as cyclosporine, FK506 and rapamycin, we studied the effect of SR-E on proliferation of human blood lymphocytes in vitro. SR-E, by itself, had no effect but the mitogen-induced lymphocyte proliferation was significantly suppressed. The suppressive effect was more pronounced with pokeweed mitogen (PWM) as compared to phytohemagglutinin (PHA) or monoclonal antibody to CD3 (anti-CD3). Since these mitogens induce cellular immunity (T cell-dependent), SR-E may potentially be a novel immunosuppressive compound.