SOD-Like Activity of Copper(II) Containing Metallopeptides Branched By 2,3-Diaminopropionic Acid: What the N-Termini Elevate,the C-Terminus Ruins

International Journal of Peptide Research and Therapeutics - Relations between structural modifiactions and SOD-like activity of four branched CuII-metallopeptides based on l-2,3-diaminopropionic...     

Early life of fathers affects offspring fitness in a wild rodent

Intergenerational fitness effects on offspring due to the early life of the parent are well studied from the standpoint of the maternal environment, but intergenerational effects owing to the paternal early life environment are often overlooked. Nonetheless, recent laboratory studies in mammals and ecologically relevant studies in invertebrates predict that paternal effects can have a major impact on the offspring's phenotype. These nongenetic, environment‐dependent paternal effects provide a mechanism for fathers to transmit environmental information to their offspring and could allow rapid adaptation. We used the bank vole Myodes glareolus, a wild rodent species with no paternal care, to test the hypothesis that a high population density environment in the early life of fathers can affect traits associated with offspring fitness. We show that the protein content in the diet and/or social environment experienced during the father's early life (prenatal and weaning) influence the phenotype and survival of his offspring and may indicate adaptation to density‐dependent costs. Furthermore, we show that experiencing multiple environmental factors during the paternal early life can lead to a different outcome on the offspring phenotype than stimulated by experience of a single environmental factor, highlighting the need to study developmental experiences in tandem rather than independent of each other.     

Origin and evolution of human microRNAs from transposable elements

We sought to evaluate the extent of the contribution of transposable elements (TEs) to human microRNA (miRNA) genes along with the evolutionary dynamics of TE-derived human miRNAs. We found 55 experimentally characterized human miRNA genes that are derived from TEs, and these TE-derived miRNAs have the potential to regulate thousands of human genes. Sequence comparisons revealed that TE-derived human miRNAs are less conserved, on average, than non-TE-derived miRNAs. However, there are 18 TE-derived miRNAs that are relatively conserved, and 14 of these are related to the ancient L2 and MIR families. Comparison of miRNA vs. mRNA expression patterns for TE-derived miRNAs and their putative target genes showed numerous cases of anti-correlated expression that are consistent with regulation via mRNA degradation. In addition to the known human miRNAs that we show to be derived from TE sequences, we predict an additional 85 novel TE-derived miRNA genes. TE sequences are typically disregarded in genomic surveys for miRNA genes and target sites; this is a mistake. Our results indicate that TEs provide a natural mechanism for the origination miRNAs that can contribute to regulatory divergence between species as well as a rich source for the discovery of as yet unknown miRNA genes.     

Pyrophosphate inhibits mineralization of osteoblast cultures by binding to mineral, up-regulating osteopontin, and inhibiting alkaline phosphatase activity

Inorganic pyrophosphate (PP(i)) produced by cells inhibits mineralization by binding to crystals. Its ubiquitous presence is thought to prevent "soft" tissues from mineralizing, whereas its degradation to P(i) in bones and teeth by tissue-nonspecific alkaline phosphatase (Tnap, Tnsalp, Alpl, Akp2) may facilitate crystal growth. Whereas the crystal binding properties of PP(i) are largely understood, less is known about its effects on osteoblast activity. We have used MC3T3-E1 osteoblast cultures to investigate the effect of PP(i) on osteoblast function and matrix mineralization. Mineralization in the cultures was dose-dependently inhibited by PP(i). This inhibition could be reversed by Tnap, but not if PP(i) was bound to mineral. PP(i) also led to increased levels of osteopontin (Opn) induced via the Erk1/2 and p38 MAPK signaling pathways. Opn regulation by PP(i) was also insensitive to foscarnet (an inhibitor of phosphate uptake) and levamisole (an inhibitor of Tnap enzymatic activity), suggesting that increased Opn levels did not result from changes in phosphate. Exogenous OPN inhibited mineralization, but dephosphorylation by Tnap reversed this effect, suggesting that OPN inhibits mineralization via its negatively charged phosphate residues and that like PP(i), hydrolysis by Tnap reduces its mineral inhibiting potency. Using enzyme kinetic studies, we have shown that PP(i) inhibits Tnap-mediated P(i) release from beta-glycerophosphate (a commonly used source of organic phosphate for culture mineralization studies) through a mixed type of inhibition. In summary, PP(i) prevents mineralization in MC3T3-E1 osteoblast cultures by at least three different mechanisms that include direct binding to growing crystals, induction of Opn expression, and inhibition of Tnap activity.     

Tissue-specific autophagy alterations and increased tumorigenesis in mice deficient in Atg4C/autophagin-3

Atg4C/autophagin-3 is a member of a family of cysteine proteinases proposed to be involved in the processing and delipidation of the mammalian orthologues of yeast Atg8, an essential component of an ubiquitin-like modification system required for execution of autophagy. To date, the in vivo role of the different members of this family of proteinases remains unclear. To gain further insights into the functional relevance of Atg4 orthologues, we have generated mutant mice deficient in Atg4C/autophagin-3. These mice are viable and fertile and do not display any obvious abnormalities, indicating that they are able to develop the autophagic response required during the early neonatal period. However, Atg4C-/--starved mice show a decreased autophagic activity in the diaphragm as assessed by immunoblotting studies and by fluorescence microscopic analysis of samples from Atg4C-/- GFP-LC3 transgenic mice. In addition, animals deficient in Atg4C show an increased susceptibility to develop fibrosarcomas induced by chemical carcinogens. Based on these results, we propose that Atg4C is not essential for autophagy development under normal conditions but is required for a proper autophagic response under stressful conditions such as prolonged starvation. We also propose that this enzyme could play an in vivo role in events associated with tumor progression.     

Possible molecular evolution of biomembranes: from single-chain to double-chain lipids

We have studied a possible evolution process permitting a 'primitive' membrane to evolve towards a membrane structure with an outer wall, similar to that of bacteria. We have investigated whether a polysaccharide bearing hydrophobic phytyl or cholesteryl chains coats giant vesicles made of single- or double-chain lipids. Phytyl-pullulan 5b was found to bind to the surface of vesicles made of either single- or double-chain lipids. In contrast, cholesteryl-pullulan 5a only coated the surface of vesicles made of double-chain lipids. These results indicate that there must be a close match between the size and shape of membrane constituents and the hydrophobic molecules to be inserted. This process could, thus, provide a selection mechanism of lipid-membrane constituents during the course of biomembrane evolution. The presence of the above 'hydrophobized' polysaccharides on the surface of different giant vesicles was identified by lectin binding. Both concanavalin A and annexin V were shown by fluorescence microscopy to bind spontaneously to vesicles made of double-chain lipids. Our experiments exemplify that self-organization of amphiphiles into closed vesicles in aqueous solution automatically leads to the coating of vesicles by 'hydrophobized' polysaccharides, which then permit lectin binding. This is a possible mechanism for the evolution of primitive membranes towards 'proto-cells'.     

Control of the autophagy maturation step by the MAPK ERK and p38: lessons from environmental carcinogens

Macroautophagy (hereafter referred to as autophagy) is the major degradative pathway of long-lived proteins and organelles that fulfils key functions in cell survival, tissue remodeling and tumor suppression. Consistently, alterations in autophagy have been involved in a growing list of pathologies including toxic injury, infections, neurodegeneration, myopathies and cancers. Although critical, the molecular mechanisms that control autophagy remain largely unknown. We have recently exploited the disruption of autophagy by environmental carcinogens as a powerful model to uncover the underlying signaling pathways. Our work published in Cancer Research revealed that the sustained activation of the MAPK ERK pathway by the carcinogen Lindane or the MEK1(+) oncogene alters autophagy selectively at the maturation step resulting in the accumulation of large defective autolysosomes. Consistent with our findings, a similar defect is observed with other common xenobiotics such as dichlorodiphenyltrichloroethane and biphenol A that specifically activate ERK. Conversely, Pentachlorophenol that activates both ERK and p38, fails to induce autophagic vacuolation. In addition, evidence is provided that abrogation of p38 by SB203580 is sufficient to interfere with the normal autophagic maturation step. Altogether, these findings underscore the critical role played by MAPK ERK and p38 in the tight control of the autophagy process at the maturation step.     

Aging-associated reductions in AMP-activated protein kinase activity and mitochondrial biogenesis

Recent studies have demonstrated a strong relationship between aging-associated reductions in mitochondrial function, dysregulated intracellular lipid metabolism, and insulin resistance. Given the important role of the AMP-activated protein kinase (AMPK) in the regulation of fat oxidation and mitochondrial biogenesis, we examined AMPK activity in young and old rats and found that acute stimulation of AMPK-alpha(2) activity by 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and exercise was blunted in skeletal muscle of old rats. Furthermore, mitochondrial biogenesis in response to chronic activation of AMPK with beta-guanidinopropionic acid (beta-GPA) feeding was also diminished in old rats. These results suggest that aging-associated reductions in AMPK activity may be an important contributing factor in the reduced mitochondrial function and dysregulated intracellular lipid metabolism associated with aging.