Rats are not the only introduced rodents producing ecosystem impacts on islands

In addition to rats, nutria (Myocastor coypus) and the North American beaver (Castor canadensis) have certainly caused damage at an ecosystem level when introduced to islands, in both cases primarily by ecosystem engineering. Of other introduced rodents successfully established on islands, the gray squirrel (Sciurus carolinensis) may be in the process of damaging entire forest ecosystems, particularly by bark-stripping. Though introduced muskrats (Ondatra zibethicus) have had ecosystem-level impacts in continental Europe, their impact on islands worldwide to which they have been introduced has been very limited. The North American red squirrel (Tamiasciurus hudsonicus) and Barbary ground squirrel (Atlantoxerus getulus) have each had substantial impacts when introduced to particular islands, but for neither species have these impacts yet been demonstrated to spread through an entire ecosystem. Introduced house mice (Mus musculus) may well generate ecosystem impacts on remote islands lacking rats, and it is possible that explosions of house mice on islands after rat eradication, a common occurrence, will lead in some instances to ecosystem impacts.     

NADPH oxidases 1 and 4 mediate cellular senescence induced by resveratrol in human endothelial cells

Resveratrol is believed to be partially responsible for the French paradox—the low risk of cardiovascular disease despite a high-fat diet in the French population. Recently, resveratrol has also been discussed as a life-span booster in several organisms. Age-related diseases are associated on the cellular level with senescence. We, therefore, hypothesized that resveratrol is vasoprotective by counteracting endothelial cell senescence. Surprisingly, we observed that chronic treatment with resveratrol (10 μM) was prosenescent in primary human endothelial cells. Resveratrol induced elevated reactive oxygen species (ROS) levels that were associated with and causally linked to an accumulation of cells in the S phase of the cell cycle, as measured by flow cytometry. We further show that cell accumulation in S phase leads to increased ROS and finally senescence. Using an siRNA approach, we clearly identified two NADPH oxidases, Nox1 and Nox4, as major targets of resveratrol and primary sources of ROS that act upstream of the observed S-phase accumulation.     

Conserved motifs in mechanosensitive channels MscL and MscS

Mechanosensitive (MS) channels play a major role in protecting bacterial cells against hypo-osmotic shock. To understand their function, it is important to identify the conserved motifs using sequence analysis methods. In this study, the sequence conservation was investigated by an in silico analysis to generate sequence logos. We have identified new conserved motifs in the domains TM1, TM2 and the cytoplasmic helix from 231 homologs of MS channel of large conductance (MscL). In addition, we have identified new motifs for the TM3 and the cytoplasmic carboxy-terminal domain from 309 homologs of MS channel of small conductance (MscS). We found that the conservation in MscL homologs is high for TM1 and TM2 in the three domains of life. The conservation in MscS homologs is high only for TM3 in Bacteria and Archaea. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Observation of sequence specificity in the seeding of protein amyloid fibrils

It is well established that the rate of formation of fibrils by amyloidogenic proteins is enhanced by the addition of preformed fibrils, a phenomenon known as seeding. We show that the efficiency of seeding fibril formation from solutions of hen lysozyme by a series of other proteins depends strongly on the similarity of their sequences. This observation is consistent with the importance of long-range interactions in stabilizing the core structure of amyloid fibrils and may be associated with the existence of a species barrier observed in the transmissible spongiform encephalopathies. In addition, it is consistent with the observation of a single dominant type of protein in the deposits associated with each form of amyloid disease.     

Different transport routes for high density lipoprotein and its associated free sterol in polarized hepatic cells

We analyzed the intracellular transport of HDL and its associated free sterol in polarized human hepatoma HepG2 cells. Using pulse-chase protocols, we demonstrated that HDL labeled with Alexa 488 at the apolipoprotein (Alexa 488-HDL) was internalized by a scavenger receptor class B type I (SR-BI)-dependent process at the basolateral membrane and became enriched in a subapical/apical recycling compartment. Most Alexa 488-HDL was rapidly recycled to the basolateral cell surface and released from cells. Within 30 min of chase at 37 degrees C, approximately 3% of the initial cell-associated Alexa 488-HDL accumulated in the biliary canaliculus (BC) formed at the apical pole of polarized HepG2 cells. Even less Alexa 488-HDL was transported to late endosomes or lysosomes. The fluorescent cholesterol analog dehydroergosterol (DHE) incorporated into Alexa 488-HDL was delivered to the BC within a few minutes, independent of the labeled apolipoprotein. This transport did not require metabolic energy and could be blocked by antibodies against SR-BI. The fraction of cell-associated DHE transported to the BC was comparable when cells were incubated with either Alexa 488-HDL containing DHE or with DHE bound to methyl-beta-cyclodextrin. We conclude that rapid, nonvesicular transport of sterol to the BC and efficient recycling of HDL particles underlies the selective sorting of sterol from HDLs in hepatocytes.     

Expression of prohibitin 3′ untranslated region suppressor RNA alters morphology and inhibits motility of breast cancer cells

The prohibitin 3 untranslated region (3UTR) belongs to a novel class of non-coding regulatory RNAs. It arrests cell cycle progression by blocking G1-S transition in breast and other cancers. Our previous studies comparing MCF7 derived clones constitutively expressing a common allelic form of prohibitin RNA (UTR/C) to various controls demonstrated that it functions as a tumor suppressor. Here, we further characterized the morphology and motility of these transgenic breast cancer cells when grown in cell culture and on nude mice. In contrast to empty vector (EV) cells, UTR/C cells were observed to grow in an organized manner with more cell-cell contact and differentiate into structures with a duct-like appearance. Computer assisted cytometry to evaluate differences in nuclear morphology was performed on UTR/C and EV tissues from nude mice. Receiver operator curve areas generated using a logistic regression model were 0.8, indicating the ability to quantitatively distinguish UTR/C from EV tissues. Keratinocyte growth factor-induced motility experiments showed that migration of UTR/C cells was significantly reduced (80–90%) compared to EV cells. Together, these data indicate that this novel 3UTR influences not only the tumorigenic phenotype but also may play a role in differentiation and migration of breast cancer cells.     

The myokine decorin is regulated by contraction and involved in muscle hypertrophy

The health-promoting effects of regular exercise are well known, and myokines may mediate some of these effects. The small leucine-rich proteoglycan decorin has been described as a myokine for some time. However, its regulation and impact on skeletal muscle has not been investigated in detail. In this study, we report decorin to be differentially expressed and released in response to muscle contraction using different approaches. Decorin is released from contracting human myotubes, and circulating decorin levels are increased in response to acute resistance exercise in humans. Moreover, decorin expression in skeletal muscle is increased in humans and mice after chronic training. Because decorin directly binds myostatin, a potent inhibitor of muscle growth, we investigated a potential function of decorin in the regulation of skeletal muscle growth. In vivo overexpression of decorin in murine skeletal muscle promoted expression of the pro-myogenic factor Mighty, which is negatively regulated by myostatin. We also found Myod1 and follistatin to be increased in response to decorin overexpression. Moreover, muscle-specific ubiquitin ligases atrogin1 and MuRF1, which are involved in atrophic pathways, were reduced by decorin overexpression. In summary, our findings suggest that decorin secreted from myotubes in response to exercise is involved in the regulation of muscle hypertrophy and hence could play a role in exercise-related restructuring processes of skeletal muscle.     

Effects of biotic disturbances on forest carbon cycling in the United States and Canada

Forest insects and pathogens are major disturbance agents that have affected millions of hectares in North America in recent decades, implying significant impacts to the carbon (C) cycle. Here, we review and synthesize published studies of the effects of biotic disturbances on forest C cycling in the United States and Canada. Primary productivity in stands was reduced, sometimes considerably, immediately following insect or pathogen attack. After repeated growth reductions caused by some insects or pathogens or a single infestation by some bark beetle species, tree mortality occurred, altering productivity and decomposition. In the years following disturbance, primary productivity in some cases increased rapidly as a result of enhanced growth by surviving vegetation, and in other cases increased slowly because of lower forest regrowth. In the decades following tree mortality, decomposition increased as a result of the large amount of dead organic matter. Net ecosystem productivity decreased immediately following attack, with some studies reporting a switch to a C source to the atmosphere, and increased afterward as the forest regrew and dead organic matter decomposed. Large variability in C cycle responses arose from several factors, including type of insect or pathogen, time since disturbance, number of trees affected, and capacity of remaining vegetation to increase growth rates following outbreak. We identified significant knowledge gaps, including limited understanding of carbon cycle impacts among different biotic disturbance types (particularly pathogens), their impacts at landscape and regional scales, and limited capacity to predict disturbance events and their consequences for carbon cycling. We conclude that biotic disturbances can have major impacts on forest C stocks and fluxes and can be large enough to affect regional C cycling. However, additional research is needed to reduce the uncertainties associated with quantifying biotic disturbance effects on the North American C budget.     

Deep Proteomic Evaluation of Primary and Cell Line Motoneuron Disease Models Delineates Major Differences in Neuronal Characteristics

The fatal neurodegenerative disorders amyotrophic lateral sclerosis and spinal muscular atrophy are, respectively, the most common motoneuron disease and genetic cause of infant death. Various in vitro model systems have been established to investigate motoneuron disease mechanisms, in particular immortalized cell lines and primary neurons. Using quantitative mass-spectrometry-based proteomics, we compared the proteomes of primary motoneurons to motoneuron-like cell lines NSC-34 and N2a, as well as to non-neuronal control cells, at a depth of 10,000 proteins. We used this resource to evaluate the suitability of murine in vitro model systems for cell biological and biochemical analysis of motoneuron disease mechanisms. Individual protein and pathway analysis indicated substantial differences between motoneuron-like cell lines and primary motoneurons, especially for proteins involved in differentiation, cytoskeleton, and receptor signaling, whereas common metabolic pathways were more similar. The proteins associated with amyotrophic lateral sclerosis also showed distinct differences between cell lines and primary motoneurons, providing a molecular basis for understanding fundamental alterations between cell lines and neurons with respect to neuronal pathways with relevance for disease mechanisms. Our study provides a proteomics resource for motoneuron research and presents a paradigm of how mass-spectrometry-based proteomics can be used to evaluate disease model systems.Motoneurons are extremely extended neurons that mediate the control of all muscle types by the central nervous system. Therefore, diseases involving progressive motoneuron degeneration such as amyotrophic lateral sclerosis (ALS)¹ (OMIM: 105400) or spinal muscle atrophy (OMIM: 253300) are particularly devastating and generally fatal disorders. Today, ALS is believed to form a phenotypic continuum with the disease entity frontotemporal lobe degeneration (OMIM: 600274) (1, 2). About 10% of ALS cases are known to be inherited, but the vast majority are considered sporadic. The number of inherited cases might be underestimated because of incomplete family histories, non-paternity, early death of family members, or incomplete penetrance (3).Mutations in several genes have been reported for the familial form, including in Sod1 (4), Als2 (5), Setx (6), Vapb (7), Tardbp (8, 9), Fus/Tls (10, 11), Vcp (12), Pfn1 (13), and several others (reviewed in Ref. 14). The most frequent genetic cause of inherited ALS was recently shown to be a hexanucleotide repeat expansion in an intron of a gene of unknown function called C9orf72 (15–17). Based on the spectrum of known mutations, several disease mechanisms for ALS have been proposed, including dysfunction of protein folding, axonal transport, RNA splicing, and metabolism (reviewed in Refs. 14, 18, and 19). Despite intensive research, it is still unclear whether a main common molecular pathway or mechanism underlies motoneuron degeneration in ALS and frontotemporal lobe degeneration. Spinal muscle atrophy is caused by homozygous mutations or deletions in the survival of motor neuron gene (Smn1) that presumably impair the RNA metabolism through diminished functionality of the Smn1 gene product (20). Over recent decades several model systems have been established to investigate ALS (21). These include transgenic animal models such as mouse (22), drosophila (23), and zebrafish (24). In cell-based studies, primary motoneurons cultured from rodent embryos (25) or motoneuron-like cell lines are employed. Primary cells are considered to more closely mimic the in vivo situation, but they are more challenging to establish and maintain. In contrast, the degree of functional relevance of cell lines can be difficult to establish, but they can be propagated without limitation and are well suited for high-throughput analysis. In particular, the spinal cord neuron–neuroblastoma hybrid cell line NSC-34 (26) and the mouse neuroblastoma cell line N2a (27) are widely used not only to assess motoneuron function, but also to study disease mechanisms in motoneurons (28, 29).As proteins are the functional actors in cells, proteomics should be able to make important contributions to the characterization and evaluation of cellular models. In particular, by identifying and quantifying the expressed proteins and bioinformatically interpreting the results, one can obtain enough information to infer functional differences. Our laboratory has previously shown proof of concept of such an approach by comparing the expression levels of about 4,000 proteins between primary hepatocytes and a hepatoma cell line (30). Very recently, mass-spectrometry-based proteomics has achieved sufficient depth and accuracy to quantify almost the entire proteome of mammalian cell lines (31–33). Furthermore, new instrumentation and algorithms now make it possible to perform label-free quantification between multiple cellular systems and with an accuracy previously associated only with stable isotope labeling techniques (34, 35).To evaluate the suitability of motoneuron-like cell lines as cellular model systems for research on ALS and related disorders, we characterized the proteomes of two widely used cell lines, NSC-34 and N2a, and compared them with the proteomes of mouse primary motoneurons and non-neuronal control cell lines. To generate primary motoneurons, we employed a recently described culturing system that makes it possible to isolate highly enriched motoneuron populations in less than 8 h (25). We identified more than 10,000 proteins and investigated differences in quantitative levels of individual neuron-associated proteins and pathways related to motoneuron function and disease mechanisms.