A tale of a tail: Structural insights into the conformational properties of the polyglutamine protein ataxin-3.

Ataxin-3 is the protein responsible for the neurodegenerative polyglutamine disease Spinocerebellar ataxia type 3. Full structural characterisation of ataxin-3 is required to aid in understanding the mechanism of disease. Despite extensive study, little is known about the conformational properties of the full-length protein, in either its non-expanded healthy or expanded pathogenic forms, particularly since its polyglutamine-containing region has denied structural elucidation. In this work, travelling-wave ion mobility spectrometry-mass spectrometry and limited proteolysis have been used to compare the conformational properties of full-length non-expanded ataxin-3 (14Q) and its isolated N-terminal Josephin domain (JD). Limited proteolysis experiments have confirmed that the JD is stable, being extremely resistant to trypsin digestion, with the exception of the α2/α3 hairpin which is flexible and exposed to protease cleavage in solution. The C-terminal region of ataxin-3 which contains the glutamine-rich sequences is largely unstructured, showing little resistance to limited proteolysis. Using ion mobility spectrometry-mass spectrometry we show that ataxin-3 (14Q) adopts a wide range of conformational states in vitro conferred by the flexibility of its C-terminal tail and the α2/α3 hairpin of the N-terminal JD. This study highlights how the power of MS-based approaches to protein structural characterisation can be particularly useful when the target protein is aggregation-prone and has intrinsically unordered regions.

Validation of 3-day rainfall forecast at the regional scale.

Nearly half of the natural disasters in the world are due to hydro-geomorphological hazards. Therefore, rainfall forecast is a key parameter for the implementation of landslides and flash-floods early warning systems. In this work we developed a routine in R software that enables the validation of a 3-day rainfall forecast by comparison with the daily rainfall data recorded in 101 automatic meteorological stations available in mainland Portugal. The routine integrates the pre-processing of base data, the matching between the 3-day rainfall forecast and the daily rainfall registered in the automatic meteorological stations based on sequence of days, the estimation of the difference between the forecasted and the real rainfall values and the computation of error measures, such as the bias, the mean absolute error, the mean absolute percentage error and the root mean square error. The results from the error measures, estimated for the 101 automatic meteorological stations, are then exported to an excel file. The routine is implemented for mainland Portugal and tested using data from February 2015, however, the spatial and temporal data can be easily updated for other regions.•A routine to validate the rainfall forecast at the regional scale using R programming language is implemented.•The automated routine can be easily updated and adapted with different spatial and temporal scales.

Guild Vertical Stratification and Drivers of Bat Foraging in a Semi-Arid Tropical Region, Kenya.

Africa faces significant challenges in reconciling economic and social development while preserving its natural resources. Little is known about the diverse bat community on the continent, particularly in drier ecosystems. A better understanding of the bat community will help improve and inform the management of these ecosystems. Our study aimed to provide detailed information on the main drivers of bat richness and activity at three different heights above the ground in a semi-arid region of Kenya. We assessed how bat activity varied with space and height using acoustic sampling and complementary methods. We sampled 48 sites at ground level and two sites on meteorological masts at 20 m and 35 m above the ground. We recorded more than 20 bat species, including one species of concern for conservation. Our models showed that the use of space varies with bat guild, creating trade-offs in the variables that affect their activity. Low-flying bat species are mostly associated with habitat variables, whereas high-flying species are more dependent on weather conditions. Our study highlights the richness of bat assemblages in semi-arid environments and emphasizes the need for management measures to protect bat diversity in the face of habitat degradation caused by climate change, land management, and development projects.

Individual variability in space use near power lines by a long-lived territorial raptor.

Evaluating species responses to anthropogenic infrastructures and other habitat changes is often used to assess environmental impacts and to guide conservation actions. However, such studies are generally carried out at the population level, disregarding inter-individual variability. Here, we investigate population- and individual-level responses toward power lines of a territorial raptor, the Bonelli's eagle Aquila fasciata. We used GPS-PTT tracking data of 17 adult eagles to model space use as a function of distance to transmission and distribution lines, while accounting for other habitat features known to affect this species. At population level, eagles increased the intensity of space use in the proximity of power lines (up to 1,000 m), suggesting an attraction effect. At individual level, some eagles shared the general population attraction pattern, while others showed reduced intensity of space use in the proximity of power lines. These differential responses were unrelated to the sex of individuals, but were affected by the characteristics of the power grid, with a tendency for apparent attraction to be associated with individuals occupying home ranges with a denser network of transmission lines and transmission pylons. However, the study could not rule out the operation of other potentially influential factors, such as individual idiosyncrasies, the spatial distribution of prey availability, and the availability of natural perches and nesting sites. Overall, these results suggest that power lines may drive different behaviors and have differential impacts across individuals, with those attracted to the proximity of power lines potentially facing increased risk of mortality through electrocution and collision, and those avoiding power lines being potentially subject to exclusion effects. More generally, our results reinforce the need to understand individual variability when assessing and mitigating impacts of anthropogenic infrastructures.

Bats use topography and nocturnal updrafts to fly high and fast.

During the day, flying animals exploit the environmental energy landscape by seeking out thermal or orographic uplift, or extracting energy from wind gradients.1-6 However, most of these energy sources are not thought to be available at night because of the lower thermal potential in the nocturnal atmosphere, as well as the difficulty of locating features that generate uplift. Despite this, several bat species have been observed hundreds to thousands of meters above the ground.7-9 Individuals make repeated, energetically costly high-altitude ascents,10-13 and others fly at some of the fastest speeds observed for powered vertebrate flight.14 We hypothesized that bats use orographic uplift to reach high altitudes,9,15-17 and that both this uplift and bat high-altitude ascents would be highly predictable.18 By superimposing detailed three-dimensional GPS tracking of European free-tailed bats (Tadarida teniotis) on high-resolution regional wind data, we show that bats do indeed use the energy of orographic uplift to climb to over 1,600 m, and also that they reach maximum sustained self-powered airspeeds of 135 km h-1. We show that wind and topography can predict areas of the landscape able to support high-altitude ascents, and that bats use these locations to reach high altitudes while reducing airspeeds. Bats then integrate wind conditions to guide high-altitude ascents, deftly exploiting vertical wind energy in the nocturnal landscape.

From Amazonia to southern Africa: atmospheric moisture transport through low-level jets and atmospheric rivers.

A Lagrangian analysis is applied to identify the main moisture source areas associated with atmospheric rivers (ARs) making landfall along the west coast of South Africa during the extended austral winter months from 1980 to 2014. The results show that areas that provide the anomalous uptake of moisture can be categorized into four regions: (1) the South Atlantic Ocean between 10°S and 30°S, (2) a clear local maximum in the eastern South Atlantic, (3) a continental source of anomalous uptake to the north of the Western Cape, and (4) over South America at a distance of more than 7000 km from the target region. It emerges that the South American moisture source can be linked to a particular phase of the South American low-level jet, known as a no Chaco jet event (NCJE), which transports moisture to the western and central South Atlantic basin. Concisely, we provide strong evidence that the two margins of the South Atlantic Ocean appear connected by two meteorological structures, with the NCJE playing a key role of transporting moisture from South America to the western and central South Atlantic basin, feeding the AR that transports some of the moisture to the west coast of South Africa.

NEDD8: a new ataxin-3 interactor.

Machado-Joseph disease (MJD/SCA3) is an autosomal dominant neurodegenerative disease caused by the expansion of a CAG tract in the coding portion of the ATXN3 gene. The presence of ubiquitin-positive aggregates of the defective protein in affected neurons is characteristic of this and most of the polyglutamine disorders. Recently, the accumulation of the neural precursor cell expressed developmentally downregulated 8 (NEDD8), a ubiquitin-like protein, in the inclusions of MJD brains was reported. Here, we report a new molecular interaction between wild-type ataxin-3 and NEDD8, using in vitro and in situ approaches. Furthermore, we show that this interaction is not dependent on the ubiquitin-interacting motifs in ataxin-3, since the presence of the Josephin domain is sufficient for the interaction to occur. The conservation of the interaction between the Caenorhabditis elegans ataxin-3 homologue (atx-3) and NEDD8 suggests its biological and functional relevance. Molecular docking studies of the NEDD8 molecule to the Josephin domain of ataxin-3 suggest that NEDD8 interacts with ataxin-3 in a substrate-like mode. In agreement, ataxin-3 displays deneddylase activity against a fluorogenic NEDD8 substrate.

Ataxin-3 plays a role in mouse myogenic differentiation through regulation of integrin subunit levels.

BACKGROUND: During myogenesis several transcription factors and regulators of protein synthesis and assembly are rapidly degraded by the ubiquitin-proteasome system (UPS). Given the potential role of the deubiquitinating enzyme (DUB) ataxin-3 in the UPS, and the high expression of the murine ataxin-3 homolog in muscle during embryogenesis, we sought to define its role in muscle differentiation. METHODOLOGY/PRINCIPAL FINDINGS: Using immunofluorescence analysis, we found murine ataxin-3 (mATX3) to be highly expressed in the differentiated myotome of E9.5 mouse embryos. C2C12 myoblasts depleted of mATX3 by RNA interference exhibited a round morphology, cell misalignment, and a delay in differentiation following myogenesis induction. Interestingly, these cells showed a down-regulation of alpha5 and alpha7 integrin subunit levels both by immunoblotting and immunofluorescence. Mouse ATX3 was found to interact with alpha5 integrin subunit and to stabilize this protein by repressing its degradation through the UPS. Proteomic analysis of mATX3-depleted C2C12 cells revealed alteration of the levels of several proteins related to integrin signaling. CONCLUSIONS: Ataxin-3 is important for myogenesis through regulation of integrin subunit levels.