Characterization of two Arabidopsis thaliana acyltransferases with preference for lysophosphatidylethanolamine

Background  

Two previously uncharacterized Arabidopsis genes that encode proteins with acyltransferase PlsC regions were selected for study based on their sequence similarity to a recently identified lung lysophosphatidylcholine acyltransferase (LPCAT). To identify their substrate specificity and biochemical properties, the two Arabidopsis acyltransferases, designated AtLPEAT1, (At1g80950), and AtLPEAT2 (At2g45670) were expressed in yeast knockout lines ale1 and slc1 that are deficient in microsomal lysophosphatidyl acyltransferase activities.     

Marine protected areas can be useful but are not a silver bullet for kelp conservation

Kelp forests are among the most valuable ecosystems on Earth, but they are increasingly being degraded and lost due to a range of human-related stressors, leading to recent calls for their improved management and conservation. One of the primary tools to conserve marine species and biodiversity is the establishment of marine protected areas (MPAs). International commitments to protect 30% of the world's ecosystems are gaining momentum, offering a promising avenue to secure kelp forests into the Anthropocene. However, a clear understanding of the efficacy of MPAs for conserving kelp forests in a changing ocean is lacking. In this perspective, we question whether strengthened global protection will create meaningful conservation outcomes for kelp forests. We explore the benefits of MPAs for kelp conservation under a suite of different stressors, focusing on empirical evidence from protected kelp forests. We show that MPAs can be effective against some drivers of kelp loss (e.g., overgrazing, kelp harvesting), particularly when they are maintained in the long-term and enforced as no-take areas. There is also some evidence that MPAs can reduce impacts of climate change through building resilience in multi-stressor situations. However, MPAs also often fail to provide protection against ocean warming, marine heatwaves, coastal darkening, and pollution, which have emerged as dominant drivers of kelp forest loss globally. Although well-enforced MPAs should remain an important tool to protect kelp forests, successful kelp conservation will require implementing an additional suite of management solutions that target these accelerating threats.     

A comparative study of hepatic trace element levels in wild moose, roe deer, and reindeer from Norway

Liver samples from 422 wild moose (Alces alces), 280 roe deer (Capreolus capreolus), and 73 reindeer (Rangifer tarandus) collected by hunters in various localities in Norway, 2002-2003, were analyzed for the essential trace elements cobalt, copper (Cu), manganese (Mn), molybdenum, selenium (Se), and zinc. Significant differences in hepatic concentrations among species were found for all elements except for Mn, and considerable individual and geographic variations were seen. Roe deer had statistically significant lower Se levels (median: 0.51 μg Se/g dry weight) than did moose (0.77 μg Se/g) and reindeer (0.85 μg Se/g). Moose from two coastal municipalities with high precipitation had considerably higher Se concentrations than those from the other localities studied. Seventy-nine roe deer (28%) and 36 moose (9%) had Se concentrations below that regarded as deficient in domestic ruminants. The Se status in roe deer was lower than previously reported in Europe. Moose had a significantly higher Cu (222 μg Cu/g dw) than did roe deer (112 μg Cu/g) and reindeer (105 μg Cu/g). The Cu status of moose and roe deer in Norway are among the highest reported in Europe. However, a suboptimal Se and Cu status was found in moose from Tvedestrand, a population which has suffered from a reduced condition and productivity. The variability in trace element status among hunted cervids, with no apparent signs of deficiency or toxicity, probably reflects adaptations in these wild ruminant species to cope with this. However, subtle clinical signs and lesions are difficult to detect and further research is needed.     

On the existence of a possible A2A-D2-β-Arrestin2 complex: A2A agonist modulation of D2 agonist-induced β-arrestin2 recruitment

Given that coactivation of adenosine A(2A) (A(2A)R) and dopamine D(2) (D(2)R) receptors results in the coaggregation, cointernalization, and codesensitization of the A(2A)R and D(2)R and the role of scaffolding protein β-arrestin2 in the desensitization, internalization, and signaling of G-protein-coupled receptors, in this study we explored the ability of the A(2A)R agonist CGS21680 in A(2A)R-D(2)R-coexpressing cells to modulate the D(2)R agonist-induced recruitment of β-arrestin2 to the D(2)R by means of proximity-based bioluminescence resonance energy transfer (BRET(2)) and co-trafficking analysis. We found evidence that CGS21680 can increase the maximal BRET(2) signal between β-arrestin2(RLuc) and D(2L)R(GFP2) upon D(2)R activation, by increasing the potency of the D(2)R agonist to exert this action. In addition, this change was associated with an increased formation of cytoplasmic clusters containing β-arrestin2(GFP2) and D(2L)R(YFP) as seen from the co-trafficking analysis. Furthermore, the A(2A)R agonist advanced the time for the increase in Akt phosphorylation obtained with the D(2)R agonist. Finally, using a novel bioinformatics approach to predict the protein-protein interface, we have also found that amino acid pro-triplets TNY, LLS, RAF, and VSR may be crucial for the -induced β-arrestin2 recruitment by A(2A)R-D(2)R heteromers. Taken together, the results indicate that the antagonistic A(2A)R-D(2)R allosteric receptor-receptor interaction in A(2A)R-D(2)R heteromers favors β-arrestin2 recruitment to the D(2L)R protomer with subsequent cointernalization associated with a reduced time onset of Akt phosphorylation followed by a rapid dephosphorylation. Thus, β-arrestin2 action becomes more rapid and short-lasting and, in this way, mimics G-protein-mediated signaling.     

The role of cAMP dependent protein kinase in modulating spontaneous intracellular Ca waves in interstitial cells of Cajal from the rabbit urethra

Interstitial cells of Cajal (ICC) serve as electrical pacemakers in the rabbit urethra. Pacemaking activity in ICC results from spontaneous intracellular Ca²⁺ waves that rely on Ca²⁺ release from endoplasmic reticulum (ER) stores. The purpose of this study was to investigate if the action of protein kinase A (PKA) affected the generation of Ca²⁺ waves in ICC. Intracellular [Ca²⁺] was measured in fluo-4 loaded ICC, freshly isolated from the rabbit urethra using a Nipkow spinning disc confocal microscope. Application of the PKA inhibitor H-89 (10 μM) significantly inhibited the generation of spontaneous Ca²⁺ waves in ICC and this was associated with a significant decrease in the ER Ca²⁺ load, measured with 10 mM caffeine responses. Ca²⁺ waves could be rescued in the presence of H-89 by stimulating ryanodine receptors (RyRs) with 1 mM caffeine but not by activation of inositol 1,4,5 tri-phosphate receptors (IP₃Rs) with 10 μM phenylephrine. Increasing intracellular PKA with the cAMP agonists forskolin and 8-bromo-cAMP failed to yield an increase in Ca²⁺ wave activity. We conclude that PKA may be maximally active under basal conditions in ICC and that inhibition of PKA with H-89 leads to a decreased ER Ca²⁺ load sufficient to inactivate IP₃Rs but not RyRs.     

Relationship between a Common Variant in the Fatty Acid Desaturase (FADS) Cluster and Eicosanoid Generation in Humans

Dramatic shifts in the Western diet have led to a marked increase in the dietary intake of the n-6 polyunsaturated fatty acid (PUFA), linoleic acid (LA). Dietary LA can then be converted to arachidonic acid (ARA) utilizing three enzymatic steps. Two of these steps are encoded for by the fatty acid desaturase (FADS) cluster (chromosome 11, 11q12.2-q13) and certain genetic variants within the cluster are highly associated with ARA levels. However, no study to date has examined whether these variants further influence pro-inflammatory, cyclooxygenase and lipoxygenase eicosanoid products. This study examined the impact of a highly influential FADS SNP, rs174537 on leukotriene, HETE, prostaglandin, and thromboxane biosynthesis in stimulated whole blood. Thirty subjects were genotyped at rs174537 (GG, n = 11; GT, n = 13; TT, n = 6), a panel of fatty acids from whole serum was analyzed, and precursor-to-product PUFA ratios were calculated as a marker of the capacity of tissues (particularly the liver) to synthesize long chain PUFAs. Eicosanoids produced by stimulated human blood were measured by LC-MS/MS. We observed an association between rs174537 and the ratio of ARA/LA, leukotriene B₄, and 5-HETE but no effect on levels of cyclooxygenase products. Our results suggest that variation at rs174537 not only impacts the synthesis of ARA but the overall capacity of whole blood to synthesize 5-lipoxygenase products; these genotype-related changes in eicosanoid levels could have important implications in a variety of inflammatory diseases.     

Long Term Expression of Drosophila melanogaster Nucleoside Kinase in Thymidine Kinase 2-deficient Mice with No Lethal Effects Caused by Nucleotide Pool Imbalances

Mitochondrial DNA depletion caused by thymidine kinase 2 (TK2) deficiency can be compensated by a nucleoside kinase from Drosophila melanogaster (Dm-dNK) in mice. We show that transgene expression of Dm-dNK in Tk2 knock-out (Tk2^−/−) mice extended the life span of Tk2^−/− mice from 3 weeks to at least 20 months. The Dm-dNK^+/−Tk2^−/− mice maintained normal mitochondrial DNA levels throughout the observation time. A significant difference in total body weight due to the reduction of subcutaneous and visceral fat in the Dm-dNK^+/−Tk2^−/− mice was the only visible difference compared with control mice. This indicates an effect on fat metabolism mediated through residual Tk2 deficiency because Dm-dNK expression was low in both liver and fat tissues. Dm-dNK expression led to increased dNTP pools and an increase in the catabolism of purine and pyrimidine nucleotides but these alterations did not apparently affect the mice during the 20 months of observation. In conclusion, Dm-dNK expression in the cell nucleus expanded the total dNTP pools to levels required for efficient mitochondrial DNA synthesis, thereby compensated the Tk2 deficiency, during a normal life span of the mice. The Dm-dNK^+/− mouse serves as a model for nucleoside gene or enzyme substitutions, nucleotide imbalances, and dNTP alterations in different tissues.     

Moose body mass variation revisited: disentangling effects of environmental conditions and genetics

Large-scale geographical variation in phenotypic traits within species is often correlated to local environmental conditions and population density. Such phenotypic variation has recently been shown to also be influenced by genetic structuring of populations. In ungulates, large-scale geographical variation in phenotypic traits, such as body mass, has been related to environmental conditions and population density, but little is known about the genetic influences. Research on the genetic structure of moose suggests two distinct genetic lineages in Norway, structured along a north-south gradient. This corresponds with many environmental gradients, thus genetic structuring provides an additional factor affecting geographical phenotypic variation in Norwegian moose. We investigated if genetic structure explained geographical variation in body mass in Norwegian moose while accounting for environmental conditions, age and sex, and if it captured some of the variance in body mass that previously was attributed to environmental factors. Genetic structuring of moose was the most important variable in explaining the geographic variation in body mass within age and sex classes. Several environmental variables also had strong explanatory power, related to habitat diversity, environmental seasonality and winter harshness. The results suggest that environmental conditions, landscape characteristics, and genetic structure should be evaluated together when explaining large-scale patterns in phenotypic characters or life history traits. However, to better understand the role of genetic and environmental effects on phenotypic traits in moose, an extended individual-based study of variation in fitness-related characters is needed, preferably in an area of convergence between different genetic lineages.