The transition metals copper and iron in neurodegenerative diseases

Neurodegenerative diseases constitute a worldwide health problem. Metals like iron and copper are essential for life, but they are also involved in several neurodegenerative mechanisms such as protein aggregation, free radical generation and oxidative stress. The role of Fe and Cu, their pathogenic mechanisms and possible therapeutic relevance are discussed regarding four of the most common neurodegenerative diseases, Alzheimer's, Parkinson's and Huntington's diseases as well as amyotrophic lateral sclerosis. Metal-mediated oxidation by Fenton chemistry is a common feature for all those disorders and takes part of a self-amplifying damaging mechanism, leading to neurodegeneration. The interaction between metals and proteins in the nervous system seems to be a crucial factor for the development or absence of neurodegeneration. The present review also deals with the therapeutic strategies tested, mainly using metal chelating drugs. Metal accumulation within the nervous system observed in those diseases could be the result of compensatory mechanisms to improve metal availability for physiological processes.     

Mode of antiviral action of silver nanoparticles against HIV-1

Background  

Silver nanoparticles have proven to exert antiviral activity against HIV-1 at non-cytotoxic concentrations, but the mechanism underlying their HIV-inhibitory activity has not been not fully elucidated. In this study, silver nanoparticles are evaluated to elucidate their mode of antiviral action against HIV-1 using a panel of different in vitro assays.     

Amerind ancestry, socioeconomic status and the genetics of type 2 diabetes in a Colombian population

The "thrifty genotype" hypothesis proposes that the high prevalence of type 2 diabetes (T2D) in Native Americans and admixed Latin Americans has a genetic basis and reflects an evolutionary adaptation to a past low calorie/high exercise lifestyle. However, identification of the gene variants underpinning this hypothesis remains elusive. Here we assessed the role of Native American ancestry, socioeconomic status (SES) and 21 candidate gene loci in susceptibility to T2D in a sample of 876 T2D cases and 399 controls from Antioquia (Colombia). Although mean Native American ancestry is significantly higher in T2D cases than in controls (32% v 29%), this difference is confounded by the correlation of ancestry with SES, which is a stronger predictor of disease status. Nominally significant association (P<0.05) was observed for markers in: TCF7L2, RBMS1, CDKAL1, ZNF239, KCNQ1 and TCF1 and a significant bias (P<0.05) towards OR>1 was observed for markers selected from previous T2D genome-wide association studies, consistent with a role for Old World variants in susceptibility to T2D in Latin Americans. No association was found to the only known Native American-specific gene variant previously associated with T2D in a Mexican sample (rs9282541 in ABCA1). An admixture mapping scan with 1,536 ancestry informative markers (AIMs) did not identify genome regions with significant deviation of ancestry in Antioquia. Exclusion analysis indicates that this scan rules out ~95% of the genome as harboring loci with ancestry risk ratios >1.22 (at P < 0.05).     

The Evolutionary Fate of the Horizontally Transferred Agrobacterial Mikimopine Synthase Gene in the Genera Nicotiana and Linaria

Few cases of spontaneously horizontally transferred bacterial genes into plant genomes have been described to date. The occurrence of horizontally transferred genes from the T-DNA of Agrobacterium rhizogenes into the plant genome has been reported in the genus Nicotiana and in the species Linaria vulgaris. Here we compare patterns of evolution in one of these genes (a gene encoding mikimopine synthase, mis) following three different events of horizontal gene transfer (HGT). As this gene plays an important role in Agrobacterium, and there are known cases showing that genes from pathogens can acquire plant protection function, we hypothesised that in at least some of the studied species we will find signs of selective pressures influencing mis sequence. The mikimopine synthase (mis) gene evolved in a different manner in the branch leading to Nicotiana tabacum and N. tomentosiformis, in the branch leading to N. glauca and in the genus Linaria. Our analyses of the genus Linaria suggest that the mis gene began to degenerate soon after the HGT. In contrast, in the case of N. glauca, the mis gene evolved under significant selective pressures. This suggests a possible role of mikimopine synthase in current N. glauca and its ancestor(s). In N. tabacum and N. tomentosiformis, the mis gene has a common frameshift mutation that disrupted its open reading frame. Interestingly, our results suggest that in spite of the frameshift, the mis gene could evolve under selective pressures. This sequence may still have some regulatory role at the RNA level as suggested by coverage of this sequence by small RNAs in N. tabacum.     

Intracellular Domain Fragment of CD44 Alters CD44 Function in Chondrocytes

The hyaluronan receptor CD44 undergoes sequential proteolytic cleavage at the cell surface. The initial cleavage of the CD44 extracellular domain is followed by a second intramembranous cleavage of the residual CD44 fragment, liberating the C-terminal cytoplasmic tail of CD44. In this study conditions that promote CD44 cleavage resulted in a diminished capacity to assemble and retain pericellular matrices even though sufficient non-degraded full-length CD44 remained. Using stable and transient overexpression of the cytoplasmic domain of CD44, we determined that the intracellular domain interfered with anchoring of the full-length CD44 to the cytoskeleton and disrupted the ability of the cells to bind hyaluronan and assemble a pericellular matrix. Co-immunoprecipitation assays were used to determine whether the mechanism of this interference was due to competition with actin adaptor proteins. CD44 of control chondrocytes was found to interact and co-immunoprecipitate with both the 65- and 130-kDa isoforms of ankyrin-3. Moreover, this interaction with ankyrin-3 proteins was diminished in cells overexpressing the CD44 intracellular domain. Mutating the putative ankyrin binding site of the transiently transfected CD44 intracellular domain diminished the inhibitory effects of this protein on matrix retention. Although CD44 in other cells types has been shown to interact with members of the ezrin/radixin/moesin (ERM) family of adaptor proteins, only modest interactions between CD44 and moesin could be demonstrated in chondrocytes. The data suggest that release of the CD44 intracellular domain into the cytoplasm of cells such as chondrocytes exerts a competitive or dominant-negative effect on the function of full-length CD44.     

Role of Protein Synthesis in the Ischemic Tolerance Acquisition Induced by Transient Forebrain Ischemia in the Rat

Although ischemic preconditioning of the heart and brain is a well-documented neuroprotective phenomenon, the mechanism underlying the increased resistance to severe ischemia induced by a preceding mild ischemic exposure remains unclear. In this study we have determined the effect of ischemic preconditioning on ischemia/reperfusion-associated translation inhibition in the neocortex and hippocampus of the rat. We studied the effect of the duration on the sublethal ischemic episode (3, 4, 5 or 8 min), as well as the amount of time elapsed between sublethal and lethal ischemia on the cell death 7 days after the last ischemic episode. In addition, the rate of protein synthesis in vitro and expression of the 72-kD heat shock protein (hsp) were determined under the different experimental conditions. Our results suggest that two different mechanisms are essential for the acquisition of ischemic tolerance, at least in the CA1 sector of hippocampus. The first mechanism implies a highly significant reduction in translation inhibition after lethal ischemia, especially at an early time of reperfusion, in both vulnerable and nonvulnerable neurons. For the acquisition of full tolerance, a second mechanism, highly dependent on the time interval between preconditioning (sublethal ischemia) and lethal ischemia, is absolutely necessary; this second mechanism involves synthesis of protective proteins, which prevent the delayed death of vulnerable neurons.     

ARF6 Regulates Neuron Differentiation through Glucosylceramide Synthase

The small GTPase ADP ribosylation factor 6 (ARF6) mediates endocytosis and has in addition been shown to regulate neuron differentiation. Here we investigated whether ARF6 promotes differentiation of Neuro-2a neuronal cells by modifying the cellular lipid composition. We showed that knockdown of ARF6 by siRNA in Neuro-2a cells increased neuronal outgrowth as expected. ARF6 knockdown also resulted in increased glucosylceramide levels and decreased sphingomyelin levels, but did not affect the levels of ceramide or phospholipids. We speculated that the ARF6 knockdown-induced increase in glucosylceramide was caused by an effect on glucosylceramide synthase and, in agreement, showed that ARF6 knockdown increased the mRNA levels and activity of glucosylceramide synthase. Finally, we showed that incubation of Neuro-2a cells with the glucosylceramide synthase inhibitor D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) normalized the increased neuronal outgrowth induced by ARF6 knockdown. Our results thus show that ARF6 regulates neuronal differentiation through an effect on glucosylceramide synthase and glucosylceramide levels.     

Involvement of abscisic acid in photosynthetic process in Hordeum vulgare L. during salinity stress

In Hordeum vulgare L. plants, NaCl stress imposed through the root medium for a period of 8 days decreased the rate of CO₂ assimilation, the chlorophyll and protein leaf content, and the activity of ribulose-1,5-bisphosphate carboxylase. The activity of phosphoenolpyruvate carboxylase was twofold over the control. Pretreatment with abscisic acid (ABA) for 3 days before salinization diminished the inhibitory effect of NaCl on the rate of CO₂ fixation. The leaf Na⁺ and Cl^– content decreased in ABA-pretreated plants. Both ABA and NaCl treatments led to an increase in the endogenous level of ABA in the plant leaves. Patterns of total proteins extracted from the leaves of control or ABA- and salt-treated plants were compared. Both ABA and NaCl induced marked quantitative and qualitative changes in the polypeptide profiles concerning mainly the proteins with approximately equal mobility. The results are discussed in terms of a possible role of ABA in increasing the salt tolerance when ABA is applied to the plants for a short period before exposure to salinity stress, thus improving the invulnerability to unfavorable conditions.Abbreviations RuBPC ribulose-1,5-bisphosphate carboxylase - PSII photosystem II - ABA abscisic acid - PEPC phosphoenolpyruvate carboxylase - DTTr dithiothreitol - BSA bovine serum albumin - ELISA enzyme-linked immunosorbent assay - SDS sodium dodecyl sulfate - PAGEr polyacrylamide gel electrophoresis     

Heavy metal accumulation by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> cells armed with metal binding hexapeptides targeted to the inner face of the plasma membrane

Accumulation of heavy metals without developing toxicity symptoms is a phenotype restricted to a small group of plants called hyperaccumulators, whose metal-related characteristics suggested the high potential in biotechnologies such as bioremediation and bioextraction. In an attempt to extrapolate the heavy metal hyperaccumulating phenotype to yeast, we obtained Saccharomyces cerevisiae cells armed with non-natural metal-binding hexapeptides targeted to the inner face of the plasma membrane, expected to sequester the metal ions once they penetrated the cell. We describe the construction of S. cerevisiae strains overexpressing metal-binding hexapeptides (MeBHxP) fused to the carboxy-terminus of a myristoylated green fluorescent protein (myrGFP). Three non-toxic myrGFP-MeBHxP (myrGFP-H6, myrGFP-C6, and myrGFP-(DE)3) were investigated against an array of heavy metals in terms of their effect on S. cerevisiae growth, heavy metal (hyper) accumulation, and capacity to remove heavy metal from contaminated environments.     

Effect of temperature of imbibition on phospholipid metabolism in pea embryonic axes

Pea seeds were imbibed in radioactive choline and then germinated. Treatments were either at 5° or 25° and the seeds were imbibed for 5 hr at one temperature and then transferred to the other. [$\text{Me}$-¹⁴C]Choline incorporation into phosphatidyl choline in the ER and the plasma membrane obtained from the embryonic axes after germination was measured. Seeds kept constantly at 25° had a very rapid initial incorporation of choline followed by a loss of label. Seeds kept at 5° had a very much lower rate of incorporation. However, seeds transferred from 5 to 25° behaved for at least 48 hr as if continuously kept at 5°, while in seeds transferred from 25 to 5° incorporation stopped after 15 hr. The seeds apparently respond to transient exposure to temperature by a changed metabolism of phospholipid. Data are also given for the choline content of the seeds under the different treatments and for the changes in total phospholipid.