Modulatory effect of guanosine-3':5' cyclic monophosphate on macrophage susceptibility to Trypanosoma cruzi infection

The effects of agents that elevate intracellular levels of cGMP on macrophage internalization of the unicellular parasite Trypanosoma cruzi and latex particles were examined in an attempt to define characteristics of the infective process. Presence of imidazole, a drug that prevents degradation of the cGMP by inhibiting cGMP phosphodiesterase activity, during macrophage-T. cruzi interaction resulted in a marked increase in the number of parasites associated with the cells and the percentage of infected cells. Similar results were obtained when sodium nitroprusside (SNP), which increases cGMP levels by an as yet undefined mechanism, dibutyryl-cGMP, or both imidazole and dibutyryl-cGMP were added to the system. In contrast, the presence of imidazole, SNP, or dibutyryl-cGMP had no significant consequence on latex particle uptake by the macrophages. Whereas pretreatment of macrophages with imidazole plus dibutyryl-cGMP readily increased T. cruzi infection, pretreatment of the parasite with these drugs had no significant effect on the interaction. Furthermore, results of radioimmunoassays showed that imidazole and SNP indeed elevated cGMP levels in the macrophages but not in the parasites. Taken together, these results indicate that cGMP plays a facilitating role in macrophage infection by T. cruzi that contrasts with the lack of effect on the uptake of inert latex particles and the previously reported inhibitory effect of cAMP in the same system. Thus, cyclic nucleotides appear to play a role in modulating internalization of the parasite but not in the uptake of an inert particle by macrophages.     

Association of shiftwork and immune cells among police officers from the Buffalo Cardio-Metabolic Occupational Police Stress study

Shift workers suffer from a constellation of symptoms associated with disruption of circadian rhythms including sleep abnormalities, and abnormal hormone secretion (e.g. melatonin, cortisol). Recent, but limited, evidence suggests that shift workers have elevated levels of circulating white blood cells (WBCs) compared to their day working counterparts. Interestingly, recent reviews highlight the strong linkage between the immune system and circadian rhythms which includes, but is not limited to, circulating cell populations and functions. The elevated levels of these WBCs may be associated with the increased chronic disease risk observed among this group. The purpose of this analysis was to examine the cross-sectional association between long- and short-term (3, 5, 7, and 14 days) shiftwork (SW) and counts of WBCs among officers in the Buffalo Cardio-Metabolic Occupational Police Stress (BCOPS) cohort. Data collection for this analysis took place among 464 police officers working in Buffalo, New York, USA between 2004 and 2009. Precise SW histories were obtained using electronic payroll records. Officers were assigned a shift type based on the shift (i.e. day, evening, night) that they spent a majority (i.e. ≥50%) of their time from 1994 to the data collection date for long-term SW. The same process was applied to SW over 3, 5, 7, and 14 days prior to data collection. A fasted blood sample collected in the morning of a non-work day was used for characterization of WBCs (total), neutrophils, monocytes, lymphocytes, eosinophils, and basophils. Potential confounding factors included demographic characteristics (e.g. age, sex, race), occupational characteristics (e.g. rank), health behaviors (e.g. smoking, alcohol consumption, diet), anthropometrics, and other biomarkers (e.g. lipids, hemoglobin A1C, leptin). Generalized linear models were used to estimate least square means of the immune cells according to SW categorization for long- and short-term SW histories. Compared to the day shift group, those working long-term night shifts had greater absolute numbers of total WBCs, neutrophils, lymphocytes, and monocytes (all p < 0.05). Those working mainly on the night shift over 7-days had elevated counts of WBCs, lymphocytes, and monocytes (p < 0.05) compared to those mainly working day shifts. Results based on 3-, 5-, and 14-day SW were similar to the 7-day results. This study corroborates other studies with similar findings. However, this analysis provided insights into the effect of both long- and short-term SW on the number of circulating WBCs. SW may lead to disruption of circadian-influenced components of the immune system, which in term, may result in various chronic diseases. These findings, plus previous findings, may provide evidence that SW may lead to immune system dysregulation. Future research is needed to understand whether increases in immune cells among shift workers may be associated with the increased disease risk among this group.     

The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1)

Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain.     

Long-Term Weight Change: Association with Impaired Glucose Metabolism in Young Austrian Adults

Little is known about the associations between long-term weight change and the natural history of impaired fasting glucose (IFG) in young adults. We investigated the association between long-term body mass index (BMI) change and the risk of IFG using data of 24,930 20- to 40-year-old participants from the Vorarlberg Health Monitoring and Promotion Program (VHM&PP) cohort. Poisson models were applied to estimate the 10-year risk for new development of IFG (≥5.6 mmol/L), and persistence of IFG. Over 10 years, most men (68.2%) and women (70.0%) stayed within their initial BMI category. The risk for incident IFG was highest for men and women with persisting obesity (37.4% and 24.1%) and lowest with persisting normal weight (15.7% and 9.3%). Men transitioning from normal to overweight increased their risk of incident IFG by factor 1.45 (95%-CI: 1.31, 1.62), women by 1.70 (95%-CI: 1.50, 1.93), whereas transitioning from overweight to normal weight decreased the risk in men by 0.69 (95%-CI: 0.53, 0.90) and 0.94 (95%-CI: 0.66, 1.33) in women. Relative risks for men and women transitioning from obesity to overweight were 0.58 and 0.44, respectively. In conclusion, 10 year weight increase was associated with an increased IFG risk, weight decrease with a decreased risk of IFG in young adults.     

Conservatism and novelty in the genetic architecture of adaptation in Heliconius butterflies

Understanding the genetic architecture of adaptive traits has been at the centre of modern evolutionary biology since Fisher; however, evaluating how the genetic architecture of ecologically important traits influences their diversification has been hampered by the scarcity of empirical data. Now, high-throughput genomics facilitates the detailed exploration of variation in the genome-to-phenotype map among closely related taxa. Here, we investigate the evolution of wing pattern diversity in Heliconius, a clade of neotropical butterflies that have undergone an adaptive radiation for wing-pattern mimicry and are influenced by distinct selection regimes. Using crosses between natural wing-pattern variants, we used genome-wide restriction site-associated DNA (RAD) genotyping, traditional linkage mapping and multivariate image analysis to study the evolution of the architecture of adaptive variation in two closely related species: Heliconius hecale and H. ismenius. We implemented a new morphometric procedure for the analysis of whole-wing pattern variation, which allows visualising spatial heatmaps of genotype-to-phenotype association for each quantitative trait locus separately. We used the H. melpomene reference genome to fine-map variation for each major wing-patterning region uncovered, evaluated the role of candidate genes and compared genetic architectures across the genus. Our results show that, although the loci responding to mimicry selection are highly conserved between species, their effect size and phenotypic action vary throughout the clade. Multilocus architecture is ancestral and maintained across species under directional selection, whereas the single-locus (supergene) inheritance controlling polymorphism in H. numata appears to have evolved only once. Nevertheless, the conservatism in the wing-patterning toolkit found throughout the genus does not appear to constrain phenotypic evolution towards local adaptive optima.     

Tableau-based protein substructure search using quadratic programming

Background  

Searching for proteins that contain similar substructures is an important task in structural biology. The exact solution of most formulations of this problem, including a recently published method based on tableaux, is too slow for practical use in scanning a large database.     

Recombinant protein expression by targeting pre-selected chromosomal loci

Background  

Recombinant protein expression in mammalian cells is mostly achieved by stable integration of transgenes into the chromosomal DNA of established cell lines. The chromosomal surroundings have strong influences on the expression of transgenes. The exploitation of defined loci by targeting expression constructs with different regulatory elements is an approach to design high level expression systems. Further, this allows to evaluate the impact of chromosomal surroundings on distinct vector constructs.     

mTORC1 activity is supported by spatial association with focal adhesions

The mammalian target of rapamycin complex 1 (mTORC1) integrates mitogenic and stress signals to control growth and metabolism. Activation of mTORC1 by amino acids and growth factors involves recruitment of the complex to the lysosomal membrane and is further supported by lysosome distribution to the cell periphery. Here, we show that translocation of lysosomes toward the cell periphery brings mTORC1 into proximity with focal adhesions (FAs). We demonstrate that FAs constitute discrete plasma membrane hubs mediating growth factor signaling and amino acid input into the cell. FAs, as well as the translocation of lysosome-bound mTORC1 to their vicinity, contribute to both peripheral and intracellular mTORC1 activity. Conversely, lysosomal distribution to the cell periphery is dispensable for the activation of mTORC1 constitutively targeted to FAs. This study advances our understanding of spatial mTORC1 regulation by demonstrating that the localization of mTORC1 to FAs is both necessary and sufficient for its activation by growth-promoting stimuli.     

Type II NADH dehydrogenase of the respiratory chain of Plasmodium falciparum and its inhibitors

Plasmodium falciparum NDH2 (pfNDH2) is a non-proton pumping, rotenone-insensitive alternative enzyme to the multi-subunit NADH:ubiquinone oxidoreductases (Complex I) of many other eukaryotes. Recombinantly expressed pfNDH2 prefers coenzyme CoQ₀ as an acceptor substrate, and can also use the artificial electron acceptors, menadione and dichlorophenol–indophenol (DCIP). Previously characterized NDH2 inhibitors, dibenziodolium chloride (DPI), diphenyliodonium chloride (IDP), and 1-hydroxy-2-dodecyl-4(1H)quinolone (HDQ) do not inhibit pfNDH2 activity. Here, we provide evidence that HDQ likely targets another P. falciparum mitochondrial enzyme, dihydroorotate dehydrogenase (pfDHOD), which is essential for de novo pyrimidine biosynthesis.