Balancing crosstalk between 20-hydroxyecdysone-induced autophagy and caspase activity in the fat body during Drosophila larval-prepupal transition

In the fruitfly, Drosophila melanogaster, autophagy and caspase activity function in parallel in the salivary gland during metamorphosis and in a common regulatory hierarchy during oogenesis. Both autophagy and caspase activity progressively increase in the remodeling fat body, and they are induced by a pulse of the molting hormone (20-hydroxyecdysone, 20E) during the larval-prepupal transition. Inhibition of autophagy and/or caspase activity in the remodeling fat body results in 25–40% pupal lethality, depending on the genotypes. Interestingly, a balancing crosstalk occurs between autophagy and caspase activity in this tissue: the inhibition of autophagy induces caspase activity and the inhibition of caspases induces autophagy. The Drosophila remodeling fat body provides an in vivo model for understanding the molecular mechanism of the balancing crosstalk between autophagy and caspase activity, which oppose with each other and are induced by the common stimulus 20E, and blockage of either path reinforces the other path.     

Altered Intracellular Localization of SOD1 in Leukocytes from Patients with Sporadic Amyotrophic Lateral Sclerosis

Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease.     

The Redox Biochemistry of Protein Sulfenylation and Sulfinylation

Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO₂H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling.     

Massive Seed Predation of Pseudobombax grandiflorum (Bombacaceae) by Parakeets Brotogeris versicolurus (Psittacidae) in a Forest Fragment in Brazil1

Here we report massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by Botogeris versicolurus (Psittacidae) in a forest fragment in Brazil. The intensity of seed predation was very high when compared to other studies in continuous forest, perhaps resulting from a scarcity of resources in such areas. This scarcity may limit the range of parrot's diet to a few plant species. It suggests that studies of Psittacidae seed predation may be important for conservation of some plants in fragments.     

Gene transfection of the HuLy-m2 (Leu-9) antigen into mouse L cells

Human DNA was transfected into mouse L cells and tk⁺ HuLy-m2⁺ (= CD7⁺) transfectants isolated after growth in hypoxanthine, aminopterin, thymidine medium and repeated cloning. After several cycles of transfection, > 90% of HuLy-m2⁺ L cells could be detected, by rosetting and by cytofluorography, which showed the transfectants to have a density of CD7 two to five times that found on peripheral blood lymphocytes. Despite this, the 37 kd CD7⁺ dimer could only be identified with difficulty using cell-surface radioiodination and sodium dodecyl sulfate-polyacrylamide gel electrophoresis techniques. An antiserum was produced (C3H anti-HuLy-m2⁺ L cells) which, after absorption, was shown to react with HuLy-m2 antigens present on human thymocytes and lymphocytes and on CD7⁺ transfected L cells.Abbreviations BSA bovine serum albumin - DME Dulbecco's modified Eagle's medium - EDTA ethylenediamine-tetraacetate - HAT hypoxanthine, aminopterin, thymidine - HSV herpes simplex virus - PBL peripheral blood lymphocyte - PBS phosphate-buffered saline - RFC rosette-forming cell - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - tk thymidine kinase     

The sialic acid residue of exogenous GM1 ganglioside is recycled for biosynthesis of sialoglycoconjugates in rat liver.

In order to assess metabolic recycling of sialic acid, GM1 ganglioside [nomenclature of Svennerholm (1964) J. Lipid. Res. 5, 145-155; IUPAC-IUB Recommendations (1977) Lipids 12, 455-468], 14C-radiolabelled at the acetyl group of sialic acid, was intravenously injected into Wistar rats, and the presence of radioactive sialic acid in liver sialoglycolipids (gangliosides) and sialoglycoproteins was ascertained. A time-course study (20 min-72 h) showed that the radioactivity present in the liver distributed in the following fractions, with reciprocal proportion varying with time: the protein (glycoprotein) fraction, the ganglioside fraction and the diffusible fraction, which contained low-Mr compounds, including sialic acid. Ganglioside-linked radioactivity gradually decreased with time; protein-linked radioactivity appeared soon after injection (20 min), reached a maximum around 20 h, then slowly diminished; diffusible radioactivity provided a sharp peak at 4 h, then rapidly decreased till disappearing after 40 h. The behaviour of bound radioactivity in the individual liver gangliosides was as follows: (a) rapid diminution with time in GM1, although with a lower rate at the longer times after injection; (b) early appearance (20 min) with a peak at 1 h, followed by continuous diminution, in GM2; (c) early appearance (20 min), peak at 1 h, diminution till 4 h, followed by a plateau, in GM3; (d) appearance at 60 min, maximum around 40 h and slow diminution thereafter, in GD1a, GD1b and GT1b. A detailed study, accomplished at 40 h after injection, demonstrated that almost all radioactivity present in the protein fraction was released by mild acid treatment and recovered in purified sialic acid; most of radioactive glycoprotein-bound sialic acid was releasable by sialidase action. In addition, the radioactivity present in the different gangliosides was exclusively carried by sialic acid and present in both sialidase-resistant and sialidase-labile residues. Only in the case of GD1a was the specific radioactivity of sialidase-resistant sialic acid superior to that of sialidase-releasable sialic acid. The results obtained lead to the following conclusions: (a) radioactive GM3 and GM2 were produced by degradation of GM1 taken up; GM3 originated partly by a process of neosynthesis; (b) radioactive GM1 consisted in part of residual exogenous GM1 and in part of a neosynthetized product; (c) radioactive GD1a originated in part by direct sialylation of GM1 taken up and in part by a neosynthetic process; (d) radioactive GD1b and GT1b resulted only from neosynthesis.(ABSTRACT TRUNCATED AT 400 WORDS)