Nonredundant roles of mitochondria-associated F-box proteins Mfb1 and Mdm30 in maintenance of mitochondrial morphology in yeast

Mitochondria constantly fuse and divide to adapt organellar morphology to the cell's ever-changing physiological conditions. Little is known about the molecular mechanisms regulating mitochondrial dynamics. F-box proteins are subunits of both Skp1-Cullin-F-box (SCF) ubiquitin ligases and non-SCF complexes that regulate a large number of cellular processes. Here, we analyzed the roles of two yeast F-box proteins, Mfb1 and Mdm30, in mitochondrial dynamics. Mfb1 is a novel mitochondria-associated F-box protein. Mitochondria in mutants lacking Mfb1 are fusion competent, but they form aberrant aggregates of interconnected tubules. In contrast, mitochondria in mutants lacking Mdm30 are highly fragmented due to a defect in mitochondrial fusion. Fragmented mitochondria are docked but nonfused in Deltamdm30 cells. Mitochondrial fusion is also blocked during sporulation of homozygous diploid mutants lacking Mdm30, leading to a mitochondrial inheritance defect in ascospores. Mfb1 and Mdm30 exert nonredundant functions and likely have different target proteins. Because defects in F-box protein mutants could not be mimicked by depletion of SCF complex and proteasome core subunits, additional yet unknown factors are likely involved in regulating mitochondrial dynamics. We propose that mitochondria-associated F-box proteins Mfb1 and Mdm30 are key components of a complex machinery that regulates mitochondrial dynamics throughout yeast's entire life cycle.     

What is MRI bone oedema in rheumatoid arthritis and why does it matter?

MRI bone oedema occurs in various forms of inflammatory and non-inflammatory arthritis and probably represents a cellular infiltrate within bone. It is common in early rheumatoid arthritis and is associated with erosive progression and poor functional outcome. Histopathological studies suggest that a cellular infiltrate comprising lymphocytes and osteoclasts may be detected in subchondral bone and could mediate the development of erosions from the marrow towards the joint surface. There is emerging evidence from animal models that such an infiltrate corresponds with MRI bone oedema, pointing towards the bone marrow as a site for important pathology driving joint damage in rheumatoid arthritis.     

Putting proteomics on target: activity-based profiling of ubiquitin and ubiquitin-like processing enzymes

Modification of proteins with ubiquitin (Ub) and Ub-like modifiers (Ubls) plays a fundamental role in cell biology. As a consequence, proteomics-based efforts were developed to characterize proteins that are modified by Ub or Ubls. A more focused functional proteomics strategy relies on active-site probes based on the Ub/Ubl scaffold, which specifically targets Ub/Ubl-processing enzymes. Activity-based profiling with such tools led to the identification of novel gene products with Ub/Ubl-processing activity and uncovered novel control mechanisms regulating their activity. This review discusses recent advances in chemistry-based functional proteomics applications, and how this information can provide a framework for drug development against Ub/Ubl-processing enzymes.     

Populations of a susceptible amphibian species can grow despite the presence of a pathogenic chytrid fungus

Disease can be an important driver of host population dynamics and epizootics can cause severe host population declines. Batrachochytrium dendrobatidis (Bd), the pathogen causing amphibian chytridiomycosis, may occur epizootically or enzootically and can harm amphibian populations in many ways. While effects of Bd epizootics are well documented, the effects of enzootic Bd have rarely been described. We used a state-space model that accounts for observation error to test whether population trends of a species highly susceptible to Bd, the midwife toad Alytes obstetricans, are negatively affected by the enzootic presence of the pathogen. Unexpectedly, Bd had no negative effect on population growth rates from 2002-2008. This suggests that negative effects of disease on individuals do not necessarily translate into negative effects at the population level. Populations of amphibian species that are susceptible to the emerging disease chytridiomycosis can persist despite the enzootic presence of the pathogen under current environmental conditions.     

Computational identification of phospho-tyrosine sub-networks related to acanthocyte generation in neuroacanthocytosis

Acanthocytes, abnormal thorny red blood cells (RBC), are one of the biological hallmarks of neuroacanthocytosis syndromes (NA), a group of rare hereditary neurodegenerative disorders. Since RBCs are easily accessible, the study of acanthocytes in NA may provide insights into potential mechanisms of neurodegeneration. Previous studies have shown that changes in RBC membrane protein phosphorylation state affect RBC membrane mechanical stability and morphology. Here, we coupled tyrosine-phosphoproteomic analysis to topological network analysis. We aimed to predict signaling sub-networks possibly involved in the generation of acanthocytes in patients affected by the two core NA disorders, namely McLeod syndrome (MLS, XK-related, Xk protein) and chorea-acanthocytosis (ChAc, VPS13A-related, chorein protein). The experimentally determined phosphoproteomic data-sets allowed us to relate the subsequent network analysis to the pathogenetic background. To reduce the network complexity, we combined several algorithms of topological network analysis including cluster determination by shortest path analysis, protein categorization based on centrality indexes, along with annotation-based node filtering. We first identified XK- and VPS13A-related protein-protein interaction networks by identifying all the interactomic shortest paths linking Xk and chorein to the corresponding set of proteins whose tyrosine phosphorylation was altered in patients. These networks include the most likely paths of functional influence of Xk and chorein on phosphorylated proteins. We further refined the analysis by extracting restricted sets of highly interacting signaling proteins representing a common molecular background bridging the generation of acanthocytes in MLS and ChAc. The final analysis pointed to a novel, very restricted, signaling module of 14 highly interconnected kinases, whose alteration is possibly involved in generation of acanthocytes in MLS and ChAc.     

Glycomic strategy for efficient linkage analysis of di-, oligo- and polysialic acids

Sialic acid polymers of glycoproteins and glycolipids are characterized by a high diversity in nature and are involved in distinct biological processes depending inter alia on the glycosidic linkages between the present sialic acid residues. Though suitable protocols are available for chain length and sialic acid determination, sensitive methods for linkage analysis of di-, oligo-, and polysialic acids (di/oligo/polySia) are still pending. In this study, we have established a highly sensitive glycomic strategy for this purpose which is based on permethylation of di/oligo/polySia after tagging their reducing ends with the fluorescent dye 1,2-diamino-4,5-methylenedioxybenzene (DMB). Using DMB-labeled sialic acid di/oligo/polymers glycosidic linkages could be efficiently determined and, optionally, the established working procedure can be combined with HPLC for in depth characterization of distinct di/oligo/polySia chains. Moreover, the outlined approach can be directly applied to mammalian tissue samples and linkage analysis of sialic acid polymers present in biopsy samples of neuroblastoma tissue demonstrating the usefulness of the outlined work flow to screen, for example, cancer tissue for the presence of distinct variants of di/oligo/polySia as potentially novel biomarkers. Hence, the described strategy offers a highly sensitive and efficient strategy for identification of glycosidic linkages in sialic acid di/oligo/polymers of glycoproteins and glycolipids.     

Detection of multiple autoantibodies in patients with ankylosing spondylitis using nucleic acid programmable protein arrays

Ankylosing spondylitis (AS) is a common, inflammatory rheumatic disease that primarily affects the axial skeleton and is associated with sacroiliitis, uveitis, and enthesitis. Unlike other autoimmune rheumatic diseases, such as rheumatoid arthritis or systemic lupus erythematosus, autoantibodies have not yet been reported to be a feature of AS. We therefore wished to determine whether plasma from patients with AS contained autoantibodies and, if so, characterize and quantify this response in comparison to patients with rheumatoid arthritis (RA) and healthy controls. Two high density nucleic acid programmable protein arrays expressing a total of 3498 proteins were screened with plasma from 25 patients with AS, 17 with RA, and 25 healthy controls. Autoantigens identified were subjected to Ingenuity Pathway Analysis to determine the patterns of signaling cascades or tissue origin. 44% of patients with ankylosing spondylitis demonstrated a broad autoantibody response, as compared with 33% of patients with RA and only 8% of healthy controls. Individuals with AS demonstrated autoantibody responses to shared autoantigens, and 60% of autoantigens identified in the AS cohort were restricted to that group. The autoantibody responses in the AS patients were targeted toward connective, skeletal, and muscular tissue, unlike those of RA patients or healthy controls. Thus, patients with AS show evidence of systemic humoral autoimmunity and multispecific autoantibody production. Nucleic acid programmable protein arrays constitute a powerful tool to study autoimmune diseases.     

Safety of the Recombinant Cholera Toxin B Subunit, Killed Whole-Cell (rBS-WC) Oral Cholera Vaccine in Pregnancy

Introduction

Mass vaccinations are a main strategy in the deployment of oral cholera vaccines. Campaigns avoid giving vaccine to pregnant women because of the absence of safety data of the killed whole-cell oral cholera (rBS-WC) vaccine. Balancing this concern is the known higher risk of cholera and of complications of pregnancy should cholera occur in these women, as well as the lack of expected adverse events from a killed oral bacterial vaccine.

Methodology/Principal Findings

From January to February 2009, a mass rBS-WC vaccination campaign of persons over two years of age was conducted in an urban and a rural area (population 51,151) in Zanzibar. Pregnant women were advised not to participate in the campaign. More than nine months after the last dose of the vaccine was administered, we visited all women between 15 and 50 years of age living in the study area. The outcome of pregnancies that were inadvertently exposed to at least one oral cholera vaccine dose and those that were not exposed was evaluated. 13,736 (94%) of the target women in the study site were interviewed. 1,151 (79%) of the 1,453 deliveries in 2009 occurred during the period when foetal exposure to the vaccine could have occurred. 955 (83%) out of these 1,151 mothers had not been vaccinated; the remaining 196 (17%) mothers had received at least one dose of the oral cholera vaccine. There were no statistically significant differences in the odds ratios for birth outcomes among the exposed and unexposed pregnancies.

Conclusions/Significance

We found no statistically significant evidence of a harmful effect of gestational exposure to the rBS-WC vaccine. These findings, along with the absence of a rational basis for expecting a risk from this killed oral bacterial vaccine, are reassuring but the study had insufficient power to detect infrequent events.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00709410","term_id":"NCT00709410"}}NCT00709410     

Remote Ischemic Conditioning to Protect against Ischemia-Reperfusion Injury: A Systematic Review and Meta-Analysis

Background

Remote ischemic conditioning is gaining interest as potential method to induce resistance against ischemia reperfusion injury in a variety of clinical settings. We performed a systematic review and meta-analysis to investigate whether remote ischemic conditioning reduces mortality, major adverse cardiovascular events, length of stay in hospital and in the intensive care unit and biomarker release in patients who suffer from or are at risk for ischemia reperfusion injury.

Methods and Results

Medline, EMBASE and Cochrane databases were searched for randomized clinical trials comparing remote ischemic conditioning, regardless of timing, with no conditioning. Two investigators independently selected suitable trials, assessed trial quality and extracted data. 23 studies in patients undergoing cardiac surgery (15 studies), percutaneous coronary intervention (four studies) and vascular surgery (four studies), comprising in total 1878 patients, were included in this review. Compared to no conditioning, remote ischemic conditioning did not reduce mortality (odds ratio 1.22 [95% confidence interval 0.48, 3.07]) or major adverse cardiovascular events (0.65 [0.38, 1.14]). However, the incidence of myocardial infarction was reduced with remote ischemic conditioning (0.50 [0.31, 0.82]), as was peak troponin release (standardized mean difference −0.28 [−0.47, −0.09]).

Conclusion

There is no evidence that remote ischemic conditioning reduces mortality associated with ischemic events; nor does it reduce major adverse cardiovascular events. However, remote ischemic conditioning did reduce the incidence of peri-procedural myocardial infarctions, as well as the release of troponin.