Social waves in giant honeybees repel hornets

Giant honeybees (Apis dorsata) nest in the open and have evolved a plethora of defence behaviors. Against predatory wasps, including hornets, they display highly coordinated Mexican wave-like cascades termed 'shimmering'. Shimmering starts at distinct spots on the nest surface and then spreads across the nest within a split second whereby hundreds of individual bees flip their abdomens upwards. However, so far it is not known whether prey and predator interact and if shimmering has anti-predatory significance. This article reports on the complex spatial and temporal patterns of interaction between Giant honeybee and hornet exemplified in 450 filmed episodes of two A. dorsata colonies and hornets (Vespa sp.). Detailed frame-by-frame analysis showed that shimmering elicits an avoidance response from the hornets showing a strong temporal correlation with the time course of shimmering. In turn, the strength and the rate of the bees' shimmering are modulated by the hornets' flight speed and proximity. The findings suggest that shimmering creates a 'shelter zone' of around 50 cm that prevents predatory wasps from foraging bees directly from the nest surface. Thus shimmering appears to be a key defence strategy that supports the Giant honeybees' open-nesting life-style.     

The Arabidopsis class VIII myosin ATM2 is involved in endocytosis

Members of the class XI of the myosin superfamily comprising higher plant, actin-based molecular motors have been shown to be involved in peroxisome and Golgi vesicle trafficking comparable to yeast and animal class V myosins. The tasks of the second class of myosins of higher plants, class VIII, are unclear. In this study the class VIII myosin ATM2 from the model plant Arabidopsis thaliana was selected for the examination of cargo specificity in vivo. Fluorescent protein-fusion plasmid constructs with fragments of the ATM2 cDNA were generated and used for Agrobacterium tumefaciens-based transient transformation of Nicotiana benthamiana leaves. The resulting subcellular localization patterns were recorded by live imaging with confocal laser scanning microscopy (CLSM) in epidermal leaf cells. Expression of a nearly full-length construct displayed labeling of filaments and vesicles, a head + neck fragment led to decoration of filaments only. However, expression of fluorescent protein-tagged C-terminal tail domain constructs labeled vesicular structures of different appearance. Most importantly, coexpression of different RFP/YFP-ATM2 tail fusion proteins showed colocalization and, hence, binding to the same type of vesicular target. Further coexpression experiments of RFP/YFP-ATM2 tail fusion proteins with the endosomal marker FYVE and the endosomal tracer FM4-64 demonstrated colocalization with endosomes. Colocalization was also detected by expression of the CFP-tagged membrane receptor BRI1 as marker, which is constantly recycled via endosomes. Occasionally the ATM2 tail targeted to sites at the plasma membrane closely resembling the pattern obtained upon expression of the YFP-ATM1 C-terminal tail. ATM1 is known for its localization at the plasma membrane at sites of plasmodesmata.     

Mapping of macrophage elastase cleavage sites in insoluble human skin elastin

Macrophage elastase (MMP-12) is a member of the family of matrix metalloproteinases (MMPs) and is active against multiple extracellular protein substrates such as elastin. Its effect on elastin is central to emphysema in the lung and photoaging of skin. Its expression in the skin increases on photodamaged skin and upon aging. Detecting and characterizing peptides cleaved in elastin, therefore, helps to understand such degradative disease processes in the skin and is also needed to assist in the rational design of agents that specifically inhibit the degradation. In this study, cleavage sites of MMP-12 in human skin elastin were extensively investigated. The peptides formed as a result of cleavages by this enzyme in the human skin elastin were characterized using mass spectrometry. A total of 41 peptides ranging from 4 to 41 amino acids were identified and 36 cleavage sites were determined. Amino acids encoded by exons 5, 6, 26, 28-31 were particularly susceptible to cleavages by MMP-12 and none or very few cleavages were detected from domains encoded by the remaining exons. The amino acid preferences of the different subsites on the catalytic domain of MMP-12 were analyzed.     

Separation and mass spectrometric characterization of covalently bound skin ceramides using LC/APCI-MS and Nano-ESI-MS/MS

Ceramides covalently bound to keratinocytes are essential for the barrier function of the skin, which can be disturbed in diseases, such as psoriasis and atopic dermatitis. These ceramides of the classes omega-hydroxyacyl-sphingosine and omega-hydroxyacyl-6-hydroxysphingosine contain an omega-hydroxy fatty acid. For their separation and identification, a new analytical approach based on normal phase liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry and tandem nano-electrospray mass spectrometry, respectively, is presented here. Tandem mass spectrometry provided structural information about the sphingoid base as well as the fatty acid moieties. The chain lengths of the bases ranged from C12 to C22, the chain lengths of the fatty acids varied between C28 and C36. In total, 67 ceramide species have been identified in human skin. The analytical methods presented in this work can be helpful for investigating alterations in the ceramide composition of the skin as seen in psoriasis, atopic dermatitis, and diseases with impaired epidermal barrier function.     

TAP score: torsion angle propensity normalization applied to local protein structure evaluation

Background  

Experimentally determined protein structures may contain errors and require validation. Conformational criteria based on the Ramachandran plot are mainly used to distinguish bet ween distorted and adequately refined models. While the readily available criteria are sufficient to detect totally wrong structures, establishing the more subtle differences between plausible structures remains more challenging.