Influence of Heparin Mimetics on Assembly of the FGF·FGFR4 Signaling Complex

Fibroblast growth factor (FGF) signaling regulates mammalian development and metabolism, and its dysregulation is implicated in many inherited and acquired diseases, including cancer. Heparan sulfate glycosaminoglycans (HSGAGs) are essential for FGF signaling as they promote FGF·FGF receptor (FGFR) binding and dimerization. Using novel organic synthesis protocols to prepare homogeneously sulfated heparin mimetics (HM), including hexasaccharide (HM₆), octasaccharide (HM₈), and decasaccharide (HM₁₀), we tested the ability of these HM to support FGF1 and FGF2 signaling through FGFR4. Biological assays show that both HM₈ and HM₁₀ are significantly more potent than HM₆ in promoting FGF2-mediated FGFR4 signaling. In contrast, all three HM have comparable activity in promoting FGF1·FGFR4 signaling. To understand the molecular basis for these differential activities in FGF1/2·FGFR4 signaling, we used NMR spectroscopy, isothermal titration calorimetry, and size-exclusion chromatography to characterize binding interactions of FGF1/2 with the isolated Ig-domain 2 (D2) of FGFR4 in the presence of HM, and binary interactions of FGFs and D2 with HM. Our data confirm the existence of both a secondary FGF1·FGFR4 interaction site and a direct FGFR4·FGFR4 interaction site thus supporting the formation of the symmetric mode of FGF·FGFR dimerization in solution. Moreover, our results show that the observed higher activity of HM₈ relative to HM₆ in stimulating FGF2·FGFR4 signaling correlates with the higher affinity of HM₈ to bind and dimerize FGF2. Notably FGF2·HM₈ exhibits pronounced positive binding cooperativity. Based on our findings we propose a refined symmetric FGF·FGFR dimerization model, which incorporates the differential ability of HM to dimerize FGFs.     

Heterocyclic analogues of squamocin as inhibitors of mitochondrial complex I. On the role of the terminal lactone of annonaceous acetogenins

Heterocyclic analogues of squamocin have been semisynthesized by condensation reactions between squamocin-derived alpha-keto esters and heterodinucleophiles. The strong complex I inhibitory potency of squamocin-benzimidazole, a hybrid derivative, illustrates for the first time the functional analogy existing between the terminal butenolide of annonaceous acetogenins and heteroaromatic substructures of classic inhibitors of the enzyme. This finding supports the categorization of this atypical group of inhibitors as antagonists of the ubiquinone substrates. In addition, competition experiments of squamocin-benzimidazole versus squamocin and rolliniastatin-2 suggest that the binding of this hybrid inhibitor is responsible for a negative allosteric effect at the level of the first ubiquinone-binding site (A site) of mitochondrial complex I. This result supports the existence of a large cooperatively regulated inhibitor/ubiquinone-binding pocket located within the catalytic core of the enzyme, consisting of the association of the previously defined affinity sites A and B.     

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.     

Consistent detection of QTLs for crown rust resistance in Italian ryegrass (<Emphasis Type="Italic">Lolium multiflorum</Emphasis> Lam.) across environments and phenotyping methods

Crown rust, caused by Puccinia coronata f. sp. lolii, is one of the most important diseases of temperate forage grasses, such as ryegrasses (Lolium spp.), affecting yield and nutritional quality. Therefore, resistance to crown rust is a major goal in ryegrass breeding programmes. In a two-way pseudo-testcross population consisting of 306 Lolium multiflorum individuals, multisite field evaluations as well as alternative methods based on artificial inoculation with natural inoculate in controlled environments were used to identify QTLs controlling resistance to crown rust. Disease scores obtained from glasshouse and leaf segment test (LST) evaluations were highly correlated with scores from a multisite field assessment (r = 0.66 and 0.79, P < 0.01, respectively) and thus confirmed suitability of these methods for crown rust investigations. Moreover, QTL mapping based on a linkage map consisting of 368 amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers revealed similar results across different phenotyping methods. Two major QTLs were consistently detected on linkage group (LG) 1 and LG 2, explaining up to 56% of total phenotypic variance (V _p). Nevertheless, differences between position and magnitude of QTLs were observed among individual field locations and suggested the existence of specific local pathogen populations. The present study not only compared QTL results among crown rust evaluation methods and environments, but also identified molecular markers closely linked to previously undescribed QTLs for crown rust resistance in Italian ryegrass with the potential to be applied in marker-assisted forage crop breeding. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparison of pelagic food webs in lakes along a trophic gradient and with seasonal aspects: influence of resource and predation

Composition and seasonal dynamics of phytoplankton, bacteria,and zooplankton (including heterotrophic flagellates, ciliates,rotifers and crustaceans) were studied in 55 lakes in NorthernGermany with different trophic status, ranging from mesotrophicto hypertrophic. Mean abundance and biomass of all groups increasedsignificantly with trophic level of the lake, but bacteria andmetazooplankton showed only a weak correlation and a slightincrease with chlorophyll concentration. Composition of phytoplanktonshowed a dominance of cyanobacteria in hypertrophic lakes, whereasthe importance of chrysophytes and dinophytes decreased withan increase in trophic status. Protozoans (heterotrophic flagellatesand ciliates) made up 24% (mesotrophic lakes) to 42% (hypertrophiclakes) of total zooplankton biomass on average, and were dominatedby ciliates (62–80% of protozoan biomass). Seasonally,protozoans can build up to 60% of zooplankton biomass in spring,when heterotrophic flagellates can contribute     

Cu(I)-thionein release from copper-loaded yeast cells

Summary The release of intact CU(I)₈-thionein from copper-resistant copper-loaded yeast cells, strain X 2180-1Aa, has been shown. This copper(I)-thiolate-rich protein was characterized and compared with the chemical and physicochemical properties of intracellular yeast Cu-thionein. The same molecular mass and stoichiometry of 8 mol copper atoms/mol protein was found. No detectable difference between the Cu-thioneins was seen in luminescence emission, electronic absorption in the ultraviolet region, chiroptical data or amino acid composition. The importance of stable Cu(I)-thiolates in Cu-thionein as a safe vehicle for transporting copper in a non-reactive manner is confirmed.     

Pedestal hairs of the ant Echinopla melanarctos (Hymenoptera, Formicidae): morphology and functional aspects

The South East Asian arboreal Formicine Echinopla melanarctos, as well as some other members of this genus possess a cuticular structure unique in ants, the pedestal hairs. In E. melanarctos, about 700 pedestal hairs are situated on the dorsal and lateral surfaces of the head, the alitrunk, the petiole and the gaster. They are arranged in a polygon-like figuration. On the summit of each of the up to 200-μm high pedestals, a single central hair inserts. This hair (up to 500-μm long) is innervated by a single bipolar mechanosensitive sensory cell. The lumen of each tube-like pedestal contains (1) epithelial cells (2) the sensory cell and the auxiliary cells of the central hair and (3) the long efferent ductules of up to ten isolated bicellular glandular units. Each glandular unit is composed of a secretory glandular cell and a duct cell, all of which are located at the base of a pedestal. The cytoplasm of a glandular cell contains a well-developed end apparatus and is characterised by stacks of smooth and granular endoplasmic reticulum, numerous polyribosomes, a lot of mitochondria and some up to 5-μm large secretory vesicles. The secretion of the gland cells is released on the apex of the pedestal wall via small pores. Approximately 30 μm below their summit, some pedestals possess additionally (up to six) mechanosensitive hairs that are arranged ray-like. We suppose that the pedestal hairs are important in nest-space protection and find that only in ants with high pedestals on the head (Echinopla melanarctos and Echinopla pallipes), the compound eyes are stalked thus overtopping the pedestals.