Translocator Protein 18 kDa (TSPO) Is Regulated in White and Brown Adipose Tissue by Obesity

Translocator protein 18 kDa (TSPO) is an outer-mitochondrial membrane transporter which has many functions including participation in the mitochondrial permeability transition pore, regulation of reactive oxygen species (ROS), production of cellular energy, and is the rate-limiting step in the uptake of cholesterol. TSPO expression is dysregulated during disease pathologies involving changes in tissue energy demands such as cancer, and is up-regulated in activated macrophages during the inflammatory response. Obesity is associated with decreased energy expenditure, mitochondrial dysfunction, and chronic low-grade inflammation which collectively contribute to the development of the Metabolic Syndrome. Therefore, we hypothesized that dysregulation of TSPO in adipose tissue may be a feature of disease pathology in obesity. Radioligand binding studies revealed a significant reduction in TSPO ligand binding sites in mitochondrial extracts from both white (WAT) and brown adipose tissue (BAT) in mouse models of obesity (diet-induced and genetic) compared to control animals. We also confirmed a reduction in TSPO gene expression in whole tissue extracts from WAT and BAT. Immunohistochemistry in WAT confirmed TSPO expression in adipocytes but also revealed high-levels of TSPO expression in WAT macrophages in obese animals. No changes in TSPO expression were observed in WAT or BAT after a 17 hour fast or 4 hour cold exposure. Treatment of mice with the TSPO ligand PK11195 resulted in regulation of metabolic genes in WAT. Together, these results suggest a potential role for TSPO in mediating adipose tissue homeostasis.     

Tree allometry of Douglas fir and Norway spruce on a nutrient-poor and a nutrient-rich site

Research related to the allometric relationships of tree height and projected tree crown area to diameter at breast height was conducted to look at the biological suitability and timber production potential of Douglas fir under the conditions present in central Europe. The dependence of allometric relationships on soil nutrient conditions were described in forest stands of Douglas fir and Norway spruce. The studied sites were climatically similar but differed in soil nutrient availability. A significant difference was found in the allometric relationships of Norway spruce trees from the nutrient poor and nutrient rich site. In contrast to the Norway spruce, there was no significant effect of site fertility on allometric relationships for Douglas fir suggesting that its allocation patterns were less sensitive to site nutrient conditions. Stem growth increment, which was measured weekly during two consecutive seasons for both species, was related to the weather conditions and available soil moisture. Stem growth of Douglas fir began about 2 weeks earlier than in the Norway spruce at both sites. At the nutrient rich site, most of the stem growth of both species occurred at the beginning of the season, while growth at the other site was more evenly distributed throughout the season. Data obtained in this study will be useful for modeling stem growth and analysis of water use efficiency of these two tree species.     

Design,synthesis and evaluation of inhibitor of apoptosis protein (IAP) antagonists that are highly selective for the BIR2 domain of XIAP

We recently reported the systematic ligand-based rational design and synthesis of monovalent Smac mimetics that bind preferentially to the BIR2 domain of the anti-apoptotic protein XIAP. Expanded structure–activity relationship (SAR) studies around these peptidomimetics led to compounds with significantly improved selectivity (>60-fold) for the BIR2 domain versus the BIR3 domain of XIAP. The potent and highly selective IAP antagonist 8q (ML183) sensitized TRAIL-resistant prostate cancer cells to apoptotic cell death, highlighting the merit of this probe compound as a valuable tool to investigate the biology of XIAP.     

Recent rapid speciation and ecomorph divergence in Indo‐Australian sea snakes

The viviparous sea snakes (Hydrophiinae) are a young radiation of at least 62 species that display spectacular morphological diversity and high levels of local sympatry. To shed light on the mechanisms underlying sea snake diversification, we investigated recent speciation and eco‐morphological differentiation in a clade of four nominal species with overlapping ranges in Southeast Asia and Australia. Analyses of morphology and stomach contents identified the presence of two distinct ecomorphs: a ‘macrocephalic’ ecomorph that reaches >2 m in length, has a large head and feeds on crevice‐dwelling eels and gobies; and a ‘microcephalic’ ecomorph that rarely exceeds 1 m in length, has a small head and narrow fore‐body and hunts snake eels in burrows. Mitochondrial sequences show a lack of reciprocal monophyly between ecomorphs and among putative species. However, individual assignment based on newly developed microsatellites separated co‐distributed specimens into four significantly differentiated clusters corresponding to morphological species designations, indicating limited recent gene flow and progress towards speciation. A coalescent species tree (based on mitochondrial and nuclear sequences) and isolation‐migration model (mitochondrial and microsatellite markers) suggest between one and three transitions between ecomorphs within the last approximately 1.2 million to approximately 840 000 years. In particular, the macrocephalic ‘eastern’ population of Hydrophis cyanocinctus and microcephalic H. melanocephalus appear to have diverged very recently and rapidly, resulting in major phenotypic differences and restriction of gene flow in sympatry. These results highlight the viviparous sea snakes as a promising system for speciation studies in the marine environment.     

Transmembrane and cytoplasmic domains in integrin activation and protein-protein interactions (Review)

Integrins are heterodimeric membrane-spanning adhesion receptors that are essential for a wide range of biological functions. Control of integrin conformational states is required for bidirectional signalling across the membrane. Key components of this control mechanism are the transmembrane and cytoplasmic domains of the α and β subunits. These domains are believed to interact, holding the integrin in the inactive state, while inside-out integrin activation is accompanied by domain separation. Although there are strong indications for domain interactions, the majority of evidence is insufficient to precisely define the interaction interface. The current best model of the complex, derived from computational calculations with experimental restraints, suggests that integrin activation by the cytoplasmic protein talin is accomplished by steric disruption of the α/β interface. Better atomic-level resolution structures of the α/β transmembrane/cytoplasmic domain complex are still required for the resting state integrin to corroborate this. Integrin activation is also controlled by competitive interactions involving the cytoplasmic domains, particularly the β-tails. The concept of the β integrin tail as a focal adhesion interaction ‘hub’ for interactions and regulation is discussed. Current efforts to define the structure and affinity of the various complexes formed by integrin tails, and how these interactions are controlled, e.g. by phosphorylation and localization, are described.     

‘It’s Always About the Eating Disorder’: Finding the Person Through Recovery-Oriented Practice for Bulimia

Culture, Medicine, and Psychiatry - Bulimia is an eating disorder characterised primarily by binging and ‘inappropriate’ compensatory behaviours, such as purging or excessive exercise....     

Plasticity in flower size as an adaptation to variation in pollinator specificity

1. Mutualisms, including plant-pollinator interactions, are an important component of ecosystems. 2. Plants can avoid the costs of variation in pollinator benefit by maintaining specificity. 3. We hypothesise a novel mechanism to ensure specificity, which takes advantage of the cognitive abilities of specific pollinators to exclude non-specific flower visitors. 4. Inflorescences of the tropical vine genus Psiguria produce flowers at regular intervals, with subsequent flowers smaller than predecessors. 5. The principle pollinators, Heliconius spp., possess an excellent spatial memory. 6. Therefore, decreasing flower size may ensure specific pollination: once Heliconius individuals have learnt the location of an inflorescence they will return, but inconspicuous flowers should reduce visits by non-specific pollinators with poorer spatial memories. 7. We tested the predictions of this hypothesis with field experiments in Panama. We confirmed that flowers on inflorescences are smaller than their predecessors. 8. Paired experiments showed that larger flowers attracted more pollinators and that the presence of an initial large flower increased subsequent visitation by Heliconius spp. to small flowers, indicating learning behaviour. 9. These results suggest that learning behaviour and decreasing flower size maintain visits from specific pollinators while reducing those from non-specific pollinators. We propose this as a novel mechanism for promoting pollinator specificity and discuss its ecological significance.     

Cumulative deamidations of the major lens protein γS‐crystallin increase its aggregation during unfolding and oxidation

Age‐related lens cataract is the major cause of blindness worldwide. The mechanisms whereby crystallins, the predominant lens proteins, assemble into large aggregates that scatter light within the lens, and cause cataract, are poorly understood. Due to the lack of protein turnover in the lens, crystallins are long‐lived. A major crystallin, γS, is heavily modified by deamidation, in particular at surface‐exposed N14, N76, and N143 to introduce negative charges. In this present study, deamidated γS was mimicked by mutation with aspartate at these sites and the effect on biophysical properties of γS was assessed via dynamic light scattering, chemical and thermal denaturation, hydrogen‐deuterium exchange, and susceptibility to disulfide cross‐linking. Compared with wild type γS, a small population of each deamidated mutant aggregated rapidly into large, light‐scattering species that contributed significantly to the total scattering. Under partially denaturing conditions in guanidine hydrochloride or elevated temperature, deamidation led to more rapid unfolding and aggregation and increased susceptibility to oxidation. The triple mutant was further destabilized, suggesting that the effects of deamidation were cumulative. Molecular dynamics simulations predicted that deamidation augments the conformational dynamics of γS. We suggest that these perturbations disrupt the native disulfide arrangement of γS and promote the formation of disulfide‐linked aggregates. The lens‐specific chaperone αA‐crystallin was poor at preventing the aggregation of the triple mutant. It is concluded that surface deamidations cause minimal structural disruption individually, but cumulatively they progressively destabilize γS‐crystallin leading to unfolding and aggregation, as occurs in aged and cataractous lenses.     

Fetal uninephrectomy in male sheep alters the systemic and renal responses to angiotensin II infusion and AT1R blockade

Fetal uninephrectomy (uni-x) at 100 days of gestation results in compensatory nephrogenesis in the remaining kidney, resulting in a 30% reduction in total nephron number in male sheep. Recently, we showed that uni-x males at 6 mo of age have elevated arterial pressure, reduced renal blood flow (RBF), glomerular filtration rate (GFR), and low plasma renin levels (Singh R, Denton K, Bertram J, Jefferies A, Head G, Lombardo P, Schneider-Kolsky M, Moritz K. J Hypertens 27: 386-396, 2009; Singh R, Denton K, Jefferies A, Bertram J, Moritz K. Clin Sci (Lond) 118: 669-680, 2010). We hypothesized this was due to upregulation of the intrarenal renin-angiotensin system (RAS). In this study, renal responses to ANG II infusion and ANG II type 1 receptor (AT1R) blockade were examined in the same 6-mo-old male sheep. Uni-x animals had reduced levels of renal tissue and plasma renin and ANG II. Renal gene expression of renin, and gene and protein levels of AT1R and AT2R, were significantly lower in uni-x animals. In response to graded ANG II infusion, sham animals had the expected decrease in conscious RBF and GFR. Interestingly, the response was biphasic in uni-x sheep, with GFR initially decreasing, but then increasing at higher ANG II doses (34 ± 7%; P(group × treatment) < 0.001), due to a paradoxical decrease in renal vascular resistance (P(group × treatment) < 0.001). In response to AT1R blockade, while GFR and RBF responded similarly between groups, there was a marked increase in sodium excretion in uni-x compared with sham sheep (209 ± 35 vs. 25 ± 12%; P < 0.001). In conclusion, in 6-mo-old male sheep born with a single kidney, these studies demonstrate that this is a low-renin form of hypertension, in which responses to ANG II are perturbed and the intrarenal RAS is downregulated.