The ability of the mitochondrial Ca2+-binding glycoprotein to restore Ca2+ transport in glycoprotein-depleted rat liver mitochondria

Rat liver mitochondria may be subfractionated in sediment and supernatant fractions by swelling in the presence of EDTA and oxaloacetate. The sediment is largely depleted of the Ca²⁺-binding glycoprotein and its Ca²⁺-transporting activity may be as low as 10–20% of the starting value. Both the rate of Ca²⁺ uptake and the capacity to maintain a high Ca²⁺ concentration gradient across the membrane are depressed. Addition of an osmotic supernatant to the assay mixture may partially restore the original Ca²⁺-transporting ability. The active component in the supernatant is the Ca²⁺-binding glycoprotein. This is shown by the following facts: (a) the effect is enhanced by the addition of the purified glycoprotein to the supernatant; (b) precipitation of the glycoprotein from the supernatant by affinity chromatography-purified antibodies abolishes the stimulatory effect, and (c) in the presence of 130 μM Mg²⁺, the glycoprotein alone may restore fully the Ca²⁺-transporting ability of the particles. The maximal velocity is already reached at 0.1 μg glycoprotein/mg mitochondrial protein.     

Gene electro-transfer of an improved erythropoietin plasmid in mice and non-human primates

BACKGROUND: Anemia due to impaired erythropoietin (EPO) production is associated with kidney failure. Recombinant proteins are commonly administered to alleviate the symptoms of this dysfunction, whereas gene therapy approaches envisaging the delivery of EPO genes have been tried in animal models in order to achieve stable and long-lasting EPO protein production. Naked DNA intramuscular injection is a safe approach for gene delivery; however, transduction levels show high inter-individual variability in rodents and very poor efficiency in non-human primates. Transduction can be improved in several animal models by application of electric pulses after DNA injection. METHODS: We have designed a modified EPO gene version by changing the EPO leader sequence and optimizing the gene codon usage. This modified gene was electro-injected into mice, rabbits and cynomolgus monkeys to test for protein production and biological effect. CONCLUSIONS: The modified EPO gene yields higher levels of circulating transgene product and a more significant biological effect than the wild-type gene in all the species tested, thus showing great potential in clinically developable gene therapy approaches for EPO delivery.     

Prostaglandins differently regulate FGF-2 and FGF receptor expression and induce nuclear translocation in osteoblasts via MAPK kinase

We have previously reported that prostaglandin F₂ (PGF₂) and its selective agonist fluprostenol increase basic fibroblast growth factor (FGF-2) mRNA and protein production in osteoblastic Py1a cells. The present report extends our previous studies by showing that Py1a cells express FGF receptor-2 (FGFR2) and that treatment with PGF₂ or fluprostenol decreases FGFR2 mRNA. We have used confocal and electron microscopy to show that, under PGF₂ stimulation, FGF-2 and FGFR2 proteins accumulate near the nuclear envelope and colocalize in the nucleus of Py1a cells. Pre-treatment with cycloheximide blocks nuclear labelling for FGF-2 in response to PGF₂. Treatment with SU5402 does not block prostaglandin-mediated nuclear internalization of FGF-2 or FGFR2. Various effectors have been used to investigate the signal transduction pathway. In particular, pre-treatment with phorbol 12-myristate 13-acetate (PMA) prevents the nuclear accumulation of FGF-2 and FGFR2 in response to PGF₂. Similar results are obtained by pre-treatment with the protein kinase C (PKC) inhibitor H-7. In addition, cells treated with PGF₂ exhibit increased nuclear labelling for the mitogen-activated protein kinase (MAPK), p44/ERK2. Pre-treatment with PMA blocks prostaglandin-induced ERK2 nuclear labelling, as confirmed by Western blot analysis. We conclude that PGF₂ stimulates nuclear translocation of FGF-2 and FGFR2 by a PKC-dependent pathway; we also suggest an involvement of MAPK/ERK2 in this process.This research was supported by grants from University of Camerino and Fondazione Carima Italy and by National Institutes of Health Grant AR-46025 (to M.M.H)     

Replacement of K-Ras with H-Ras supports normal embryonic development despite inducing cardiovascular pathology in adult mice

Ras proteins are highly related GTPases that have key roles in regulating growth, differentiation and tumorigenesis. Gene-targeting experiments have shown that, out of the three mammalian ras genes, only K-ras is essential for normal mouse embryogenesis, and that mice deprived of H-ras and/or N-ras show no major phenotype. We generated mice (HrasKI) in which the K-ras gene had been modified to encode H-Ras protein. HrasKI mice produce undetectable amounts of K-Ras but-in contrast to mice homozygous for a null K-ras allele-they are born at the expected mendelian frequency, indicating that H-Ras can be substituted for K-Ras in embryonic development. However, adult HrasKI mice show dilated cardiomyopathy associated with arterial hypertension. Our results show that K-Ras can be replaced by H-Ras in its essential function in embryogenesis, and indicate that K-Ras has a unique role in cardiovascular homeostasis.     

The extraordinary ligand binding properties of human serum albumin

Human serum albumin (HSA), the most prominent protein in plasma, binds different classes of ligands at multiple sites. HSA provides a depot for many compounds, affects pharmacokinetics of many drugs, holds some ligands in a strained orientation providing their metabolic modification, renders potential toxins harmless transporting them to disposal sites, accounts for most of the antioxidant capacity of human serum, and acts as a NO-carrier. The globular domain structural organization of monomeric HSA is at the root of its allosteric properties which are reminiscent of those of multimeric proteins. Here, structural, functional, biotechnological, and biomedical aspects of ligand binding to HSA are summarized.     

Electromagnetic fields from mobile phones do not affect the inner auditory system of Sprague-Dawley rats

The auditory system is the first biological structure facing the electromagnetic fields emitted by mobile phones. The aim of this study was to evaluate the cochlear functionality of Sprague-Dawley rats exposed to electromagnetic fields at the typical frequencies of GSM mobile phones (900 and 1800 MHz) by distortion product otoacoustic emissions, which are a well-known indicator of the status of the cochlea's outer hair cells. A population of 48 rats was divided into exposed and sham-exposed groups. Three sets of four loop antennas, one for sham-exposed animals and two for exposed animals, were used for the local exposures. Rats were exposed 2 h/day, 5 days/week for 4 weeks at a local SAR of 2 W/kg in the ear. Distortion product otoacoustic emissions tests were carried out before, during and after the exposure. The analysis of the data shows no statistically significant differences between the audiological signals recorded for the different groups.     

Structural determinants of unexpected agonist activity in a retro-peptide analogue of the SDF-1alpha N-terminus

We have synthesised two retro-peptide analogues of the stromal cell derived growth factor 1 (SDF-1alpha) segment known to be critical for CXCR4 receptor binding, corresponding to the sequences HSEFFRCPCRFFESH and HSEFFRGGGRFFESH. We have assayed the ability of these peptides to activate extracellular signal-regulated kinase 1/2 phosphorylation in cells over expressing the SDF-1alpha receptor, finding that the first variant was able to serve as an agonist of CXCR4, whereas the second one was inactive. Finally, by comparing representative solution structures of the two peptides, we have found that the biological response of HSEFFRCPCRFFESH may be ascribed to a beta-beta-type turn motif centred on Phe(4)-Phe(5).