Adipose triglyceride lipase regulates eicosanoid production in activated human mast cells

Human mast cells (MCs) contain TG-rich cytoplasmic lipid droplets (LDs) with high arachidonic acid (AA) content. Here, we investigated the functional role of adipose TG lipase (ATGL) in TG hydrolysis and the ensuing release of AA as substrate for eicosanoid generation by activated human primary MCs in culture. Silencing of ATGL in MCs by siRNAs induced the accumulation of neutral lipids in LDs. IgE-dependent activation of MCs triggered the secretion of the two major eicosanoids, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4). The immediate release of PGD2 from the activated MCs was solely dependent on cyclooxygenase (COX) 1, while during the delayed phase of lipid mediator production, the inducible COX-2 also contributed to its release. Importantly, when ATGL-silenced MCs were activated, the secretion of both PGD2 and LTC4 was significantly reduced. Interestingly, the inhibitory effect on the release of LTC4 was even more pronounced in ATGL-silenced MCs than in cytosolic phospholipase A₂-silenced MCs. These data show that ATGL hydrolyzes AA-containing TGs present in human MC LDs and define ATGL as a novel regulator of the substrate availability of AA for eicosanoid generation upon MC activation.     

Analysis of conformational motions and related key residue interactions responsible for a specific function of proteins with elastic network model

Protein collective motions play a critical role in many biochemical processes. How to predict the functional motions and the related key residue interactions in proteins is important for our understanding in the mechanism of the biochemical processes. Normal mode analysis (NMA) of the elastic network model (ENM) is one of the effective approaches to investigate the structure-encoded motions in proteins. However, the motion modes revealed by the conventional NMA approach do not necessarily correspond to a specific function of protein. In the present work, a new analysis method was proposed to identify the motion modes responsible for a specific function of proteins and then predict the key residue interactions involved in the functional motions by using a perturbation approach. In our method, an internal coordinate that accounts for the specific function was introduced, and the Cartesian coordinate space was transformed into the internal/Cartesian space by using linear approximation, where the introduced internal coordinate serves as one of the axes of the coordinate space. NMA of ENM in this internal/Cartesian space was performed and the function-relevant motion modes were identified according to their contributions to the specific function of proteins. Then the key residue interactions important for the functional motions of the protein were predicted as the interactions whose perturbation largely influences the fluctuation along the internal coordinate. Using our proposed methods, the maltose transporter (MalFGK₂) from E. Coli was studied. The functional motions and the key residue interactions that are related to the channel-gating function of this protein were successfully identified.     

Reliably Detecting Clinically Important Variants Requires Both Combined Variant Calls and Optimized Filtering Strategies

A diversity of tools is available for identification of variants from genome sequence data. Given the current complexity of incorporating external software into a genome analysis infrastructure, a tendency exists to rely on the results from a single tool alone. The quality of the output variant calls is highly variable however, depending on factors such as sequence library quality as well as the choice of short-read aligner, variant caller, and variant caller filtering strategy. Here we present a two-part study first using the high quality ‘genome in a bottle’ reference set to demonstrate the significant impact the choice of aligner, variant caller, and variant caller filtering strategy has on overall variant call quality and further how certain variant callers outperform others with increased sample contamination, an important consideration when analyzing sequenced cancer samples. This analysis confirms previous work showing that combining variant calls of multiple tools results in the best quality resultant variant set, for either specificity or sensitivity, depending on whether the intersection or union, of all variant calls is used respectively. Second, we analyze a melanoma cell line derived from a control lymphocyte sample to determine whether software choices affect the detection of clinically important melanoma risk-factor variants finding that only one of the three such variants is unanimously detected under all conditions. Finally, we describe a cogent strategy for implementing a clinical variant detection pipeline; a strategy that requires careful software selection, variant caller filtering optimizing, and combined variant calls in order to effectively minimize false negative variants. While implementing such features represents an increase in complexity and computation the results offer indisputable improvements in data quality.     

A Neural Model of Auditory Space Compatible with Human Perception under Simulated Echoic Conditions

In a typical auditory scene, sounds from different sources and reflective surfaces summate in the ears, causing spatial cues to fluctuate. Prevailing hypotheses of how spatial locations may be encoded and represented across auditory neurons generally disregard these fluctuations and must therefore invoke additional mechanisms for detecting and representing them. Here, we consider a different hypothesis in which spatial perception corresponds to an intermediate or sub-maximal firing probability across spatially selective neurons within each hemisphere. The precedence or Haas effect presents an ideal opportunity for examining this hypothesis, since the temporal superposition of an acoustical reflection with sounds arriving directly from a source can cause otherwise stable cues to fluctuate. Our findings suggest that subjects’ experiences may simply reflect the spatial cues that momentarily arise under various acoustical conditions and how these cues are represented. We further suggest that auditory objects may acquire “edges” under conditions when interaural time differences are broadly distributed.     

The ADP/ATP carrier is the 32-kilodalton receptor for an NH2-terminally myristylated src peptide but not for pp60src polypeptide.

Membrane binding of pp60src is initiated via its myristylated NH2 terminus. To identify a candidate pp60src docking protein or receptor in the membrane, a radiolabelled peptide corresponding to the pp60src NH2-terminal membrane binding domain was cross-linked to fibroblast membranes and found to specifically label a 32-kDa protein. This protein was purified by appending an affinity tag to the peptide probe so that the cross-linked complex could be isolated via affinity chromatography. Microsequencing indicated that the 32-kDa protein was the mitochondrial ADP/ATP carrier (AAC). This result was further confirmed by the ability of an antibody to the AAC to immunoprecipitate the cross-linked complex, by the ability of certain inhibitors of the AAC to block cross-linking, and by membrane fractionation to show that complex formation occurred essentially exclusively in the mitochondrial fraction. While the AAC bound the myristyl-src peptide in a specific manner both in vitro and in vivo, its localization to the inner membrane of the mitochondrion precludes its being a pp60src binding protein. An analysis of pp60v-src binding in vitro was consistent with this expectation. Thus, use of a myristyl-src peptide revealed an unexpected and previously unidentified binding capacity of the AAC, most likely related to the ability of long-chain fatty acyl coenzyme As to serve as AAC inhibitors. The amphipathic nature of the pp60src NH2 terminus suggests alternative strategies for uncovering pp60src membrane binding species.     

Shallow water rissoiform gastropods from Tristan da Cunha, South Atlantic Ocean, with records of species from Gough Island

Shallow water rissoiform gastropods collected by the Norwegian Scientific Expedition (1937-1938) to Tristan da Cunha are described. The fauna consists of Powellisefia cf. philomelae (Watson) (Rissoidae), three new species of Eatoniella, E. trochiformisa, E. lineuta , and E. tristanensis (Eatoniellidae). two new species of Onoba, O. crassicordara and O. tristanensis (Rissoidae) and Rissoella cf. irma (Bartsch) (Rissoellidae). A small collection from Cough Island is also described, containing three species referred to Onoha , one of which is described as new. O. merelinoides , and a species of Eutoniella. The biogeographie relationships of the fauna are briefly discussed.