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831.
SK Weeratunga A Osman NJ Hu CK Wang L Mason S Svärd G Hope MK Jones A Hofmann 《Journal of molecular biology》2012,423(2):169-181
Alpha-giardins constitute the annexin proteome (group E annexins) in the intestinal protozoan parasite Giardia and, as such, represent the evolutionary oldest eukaryotic annexins. The dominance of alpha-giardins in the cytoskeleton of Giardia with its greatly reduced actin content emphasises the importance of the alpha-giardins for the structural integrity of the parasite, which is particularly critical in the transformation stage between cyst and trophozoite. In this study, we report the crystal structures of the apo- and calcium-bound forms of α1-giardin, a protein localised to the plasma membrane of Giardia trophozoites that has recently been identified as a vaccine target. The calcium-bound crystal structure of α1-giardin revealed the presence of a type III site in the first repeat as known from other annexin structures, as well as a novel calcium binding site situated between repeats I and IV. By means of comparison, the crystal structures of three different alpha-giardins known to date indicate that these proteins engage different calcium coordination schemes, among each other, as well as compared to annexins of groups A-D. Evaluation of the calcium-dependent binding to acidic phosphoplipid membranes revealed that this process is not only mediated but also regulated by the environmental calcium concentration. Uniquely within the large family of annexins, α1-giardin disengages from the phospholipid membrane at high calcium concentrations possibly due to formation of a dimeric species. The observed behaviour is in line with changing calcium levels experienced by the parasite during excystation and may thus provide first insights into the molecular mechanisms underpinning the transformation and survival of the parasite in the host. 相似文献
832.
833.
Astrid Gadeyne Clara Sánchez-Rodríguez Steffen Vanneste Simone Di Rubbo Henrik Zauber Kevin Vanneste Jelle Van Leene Nancy De Winne Dominique Eeckhout Geert Persiau Eveline Van De Slijke Bernard Cannoot Leen Vercruysse Jonathan R. Mayers Maciek Adamowski Urszula Kania Matthias Ehrlich Alois Schweighofer Tijs Ketelaar Steven Maere Sebastian Y. Bednarek Jiří Friml Kris Gevaert Erwin Witters Eugenia Russinova Staffan Persson Geert De Jaeger Daniël Van Damme 《Cell》2014
834.
Lena Innala Ewa Berglin Bozena M?ller Lotta Ljung Torgny Smedby Anna S?dergren Staffan Magnusson Solbritt Rantap??-Dahlqvist Solveig W?llberg-Jonsson 《Arthritis research & therapy》2014,16(2):R94
Introduction
Disease activity, severity and comorbidity contribute to increased mortality in patients with rheumatoid arthritis (RA). We evaluated the impact of age at disease onset on prognostic risk factors and treatment in patients with early disease.Methods
In this study, 950 RA patients were followed regularly from the time of inclusion (<12 months from symptom onset) for disease activity (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), tender and/or swollen joints, Visual Analogue Scale pain and global scores, and Disease Activity Score in 28 joints (DAS28)) and function (Health Assessment Questionnaire (HAQ)). Disease severity, measured on the basis of radiographs of the hands and feet (erosions based on Larsen score), extraarticular disease, nodules, and comorbidities and treatment (disease-modifying antirheumatic drugs (DMARDs), corticosteroids, biologics and nonsteroidal anti-inflammatory drugs) were recorded at the time of inclusion and at 5 years. Autoantibodies (rheumatoid factor, antinuclear antibodies and antibodies against cyclic citrullinated peptides (ACPAs)) and genetic markers (human leucocyte antibody (HLA) shared epitope and protein tyrosine phosphatase nonreceptor type 22 (PTPN22)) were analysed at the time of inclusion. Data were stratified as young-onset RA (YORA) and late-onset RA (LORA), which were defined as being below or above the median age at the time of onset of RA (58 years).Results
LORA was associated with lower frequency of ACPA (P < 0.05) and carriage of PTPN22-T variant (P < 0.01), but with greater disease activity at the time of inclusion measured on the basis of ESR (P < 0.001), CRP (P < 0.01) and accumulated disease activity (area under the curve for DAS28 score) at 6 months (P < 0.01), 12 months (P < 0.01) and 24 months (P < 0.05), as well as a higher HAQ score (P < 0.01) compared with YORA patients. At baseline and 24 months, LORA was more often associated with erosions (P < 0.01 for both) and higher Larsen scores (P < 0.001 for both). LORA was more often treated with corticosteroids (P < 0.01) and less often with methotrexate (P < 0.001) and biologics (P < 0.001). YORA was more often associated with early DMARD treatment (P < 0.001). The results of multiple regression analyses supported our findings regarding the impact of age on chosen treatment.Conclusion
YORA patients were more frequently ACPA-positive than LORA patients. LORA was more often associated with erosions, higher Larsen scores, higher disease activity and higher HAQ scores at baseline. Nevertheless, YORA was treated earlier with DMARDs, whilst LORA was more often treated with corticosteroids and less often with DMARDs in early-stage disease. These findings could have implications for the development of comorbidities. 相似文献835.
836.
Abundances and distributions of species are usually associated. This implies that as a species declines in abundance so does the number of sites it occupies. Conversely, when there is an increase in a species' range size, it is usually followed by an increase in population size (Gaston et al. 2000 ). This ecological phenomenon, also known as the abundance–occupancy relationship (AOR), is well documented in several species of animals and plants (Gaston et al. 2000 ) but has been little investigated in parasites. In this issue of Molecular Ecology, Drovetski et al. ( 2014 ) investigated the AOR in avian haemosporidians (vector‐borne blood parasites) using data from four well‐sampled bird communities. In support of the AOR, the research group found that the abundance of parasite cytochrome b lineages (a commonly used proxy for species identification within this group of parasites) was positively linked with the abundance of susceptible avian host species and that the most abundant haemospordian lineages were those with larger ranges. Drovetski et al. ( 2014 ) also found evidence for both hypotheses proposed to explain the AOR in parasites: the trade‐off hypothesis (TOH) and the niche‐breadth hypothesis (NBH). Interestingly, the main predictor of the AOR was the number of susceptible hosts (i.e. number of infected birds) and not the number of host species the parasites were able to exploit. 相似文献
837.
Katri Korpela Pekka Helle Heikki Henttonen Erkki Korpim?ki Esa Koskela Otso Ovaskainen Hannu Pieti?inen Janne Sundell Jari Valkama Otso Huitu 《Proceedings. Biological sciences / The Royal Society》2014,281(1797)
The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data collected throughout Finland during 1986–2011, we analyse the spatio-temporal variation in the interactions between populations of voles and specialist, generalist and avian predators, and investigate by simulations the roles of the different predators in the vole cycle. We test the hypothesis that vole population cyclicity is dependent on predator–prey interactions during winter. Our results support the importance of the small mustelids for the vole cycle. However, weakening specialist predation during winters, or an increase in generalist predation, was not associated with the loss of cyclicity. Strengthening of delayed density dependence coincided with strengthening small mustelid influence on the summer population growth rates of voles. In conclusion, a strong impact of small mustelids during summers appears highly influential to vole population dynamics, and deteriorating winter conditions are not a viable explanation for collapsing small mammal population cycles. 相似文献
838.
Lion fecal DNA extracts from four individuals each from Yankari Game Reserve and Kainji‐Lake National Park (central northeast and west Nigeria, respectively) were Sanger‐sequenced for the mitochondrial cytochrome b gene. The sequences were aligned against 61 lion reference sequences from other parts of Africa and India. The sequence data were analyzed further for the construction of phylogenetic trees using the maximum‐likelihood approach to depict phylogenetic patterns of distribution among sequences. Our results show that Nigerian lions grouped together with lions from West and Central Africa. At the smaller geographical scale, lions from Kainji‐Lake National Park in western Nigeria grouped with lions from Benin (located west of Nigeria), whereas lions from Yankari Game Reserve in central northeastern Nigeria grouped with the lion populations in Cameroon (located east of Nigeria). The finding that the two remaining lion populations in Nigeria have different phylogenetic origins is an important aspect to consider in future decisions regarding management and conservation of rapidly shrinking lion populations in West Africa. 相似文献
839.
Praveen Krishnamoorthy Clara Sanchez-Rodriguez Ingo Heilmann Staffan Persson 《Annals of botany》2014,114(6):1049-1057
Background
Plant cell walls are complex matrices of carbohydrates and proteins that control cell morphology and provide protection and rigidity for the plant body. The construction and maintenance of this intricate system involves the delivery and recycling of its components through a precise balance of endomembrane trafficking, which is controlled by a plethora of cell signalling factors. Phosphoinositides (PIs) are one class of signalling molecules with diverse roles in vesicle trafficking and cytoskeleton structure across different kingdoms. Therefore, PIs may also play an important role in the assembly of plant cell walls.Scope
The eukaryotic PI pathway is an intricate network of different lipids, which appear to be divided in different pools that can partake in vesicle trafficking or signalling. Most of our current understanding of how PIs function in cell metabolism comes from yeast and mammalian systems; however, in recent years significant progress has been made towards a better understanding of the plant PI system. This review examines the current state of knowledge of how PIs regulate vesicle trafficking and their potential influence on plant cell-wall architecture. It considers first how PIs are formed in plants and then examines their role in the control of vesicle trafficking. Interactions between PIs and the actin cytoskeleton and small GTPases are also discussed. Future challenges for research are suggested. 相似文献840.
Kai Wei Kelvin Lee Saravanan Periasamy Manisha Mukherjee Chao Xie Staffan Kjelleberg Scott A Rice 《The ISME journal》2014,8(4):894-907
Most studies of biofilm biology have taken a reductionist approach, where single-species biofilms have been extensively investigated. However, biofilms in nature mostly comprise multiple species, where interspecies interactions can shape the development, structure and function of these communities differently from biofilm populations. Hence, a reproducible mixed-species biofilm comprising Pseudomonas aeruginosa, Pseudomonas protegens and Klebsiella pneumoniae was adapted to study how interspecies interactions affect biofilm development, structure and stress responses. Each species was fluorescently tagged to determine its abundance and spatial localization within the biofilm. The mixed-species biofilm exhibited distinct structures that were not observed in comparable single-species biofilms. In addition, development of the mixed-species biofilm was delayed 1–2 days compared with the single-species biofilms. Composition and spatial organization of the mixed-species biofilm also changed along the flow cell channel, where nutrient conditions and growth rate of each species could have a part in community assembly. Intriguingly, the mixed-species biofilm was more resistant to the antimicrobials sodium dodecyl sulfate and tobramycin than the single-species biofilms. Crucially, such community level resilience was found to be a protection offered by the resistant species to the whole community rather than selection for the resistant species. In contrast, community-level resilience was not observed for mixed-species planktonic cultures. These findings suggest that community-level interactions, such as sharing of public goods, are unique to the structured biofilm community, where the members are closely associated with each other. 相似文献