Insulin forms amyloid in a strain-dependent manner: an FT-IR spectroscopic study

The presence of 20% (v/v) ethanol triggers growth of insulin amyloid with distinct infrared spectroscopic features, compared with the fibrils obtained under ambient conditions. Here we report that the two insulin amyloid types behave in the prion strain-like manner regarding seeding specificity and ability of the self-propagating conformational template to overrule unfavorable environmental factors and maintain the initial folding pattern. The type of the original seed has been shown to prevail over cosolvent effects and determines spectral position and width of the amide I' infrared band of the heterogeneously seeded amyloid. These findings imply that "strains" may be a common generic trait of amyloids.     

New information on the invasive to Europe aphid species <Emphasis Type="Italic">Brachycaudus divaricatae</Emphasis> Shaposhnikov, 1956 (Hemiptera: Aphididae)

Brachycaudus divaricatae (Hemiptera: Aphididae), a recent invader to Europe, has already reached Czech Republic. Partial sequences of mitochondrial COI and nuclear EF-1α genes have been analysed across the sixteen Czech samples of B. divaricatae, together with morphometric analysis of the same samples based on eighteen morphological characters of the apterous viviparous females. For comparative studies, thirteen samples from the Eastern Baltic region of Europe (Latvia, Lithuania and Poland) were used. All sampled populations appeared similar in their genetic and morphological characters studied. One haplotype of mitochondrial COI gene was predominant; it was characteristic for all samples from Czech Republic and 8 out of 13 samples from Eastern Baltic region. Two other haplotypes were found in the Eastern Baltic region only. Four different haplotypes of EF-1α gene were detected. Most of the samples (except one sample from the Eastern Baltic region and two samples from Czech Republic) had the same haplotype. Out of remaining three haplotypes, one was unique for the Eastern Baltic region, whilst two were found in Czech Republic only. For the present, Moravia is the southernmost region in Europe, where B. divaricatae has been already reported. Presumably, this invasive aphid species has entered the Czech Republic from the north via the Moravian Gate, a natural pass formed by the depression between the Western Carpathians and Eastern Sudetes.     

Phylogenetic relationships of Dysaphis pyri (Boyer de Fonscolombe) and Dysaphis reaumuri (Mordvilko) (Hemiptera, Sternorrhyncha: Aphididae): COI and EF-1α evidence

Dysaphis (Pomaphis) pyri (Boyer de Fonscolombe, 1841) and Dysaphis (Pomaphis) reaumuri (Mordvilko, 1928) are two holocyclic aphid species alternating between Pyrus (Rosaceae) and Galium (Rubiaceae). Comparative phylogenetic analysis was performed using partial mitochondrial cytochrome oxidase subunit I (COI) and nuclear elongation factor 1 alpha (EF-1??) sequences. Partial COI data indicate the possibility of the early divergence in the D. pyri?CD. reaumuri stem, which might have occurred even before the splitting of the common ancestral species of the D. reaumuri?CD. plantaginea complex. Such a conclusion seems to be compatible with the available data on host specificity, life cycles and distribution of both species. This introductory phylogenetic analysis based on partial COI and EF-1?? sequences indicates the need for reconsideration of the subgeneric structure in the genus Dysaphis.     

Driving forces and structural determinants of steric zipper peptide oligomer formation elucidated by atomistic simulations

Understanding the structural and energetic requirements of non-fibrillar oligomer formation harbors the potential to decipher an important yet still elusive part of amyloidogenic peptide and protein aggregation. Low-molecular-weight oligomers are described to be transient and polymorphic intermediates in the nucleated self-assembly process to highly ordered amyloid fibers and were additionally found to exhibit a profound cytotoxicity. However, detailed structural information on the oligomeric species involved in the nucleation cannot be readily inferred from experiments. Here, we study the spontaneous assembly of steric zipper peptides from the tau protein, insulin and α-synuclein with atomistic molecular dynamics simulations on the microsecond timescale. Detailed analysis of the forces driving the oligomerization reveals a common two-step process akin to a general condensation-ordering mechanism and thus provides a rational understanding of the molecular basis of peptide self-assembly. Our results suggest that the initial formation of partially ordered peptide oligomers is governed by the solvation free energy, whereas the dynamical ordering and emergence of β-sheets are mainly driven by optimized inter-peptide interactions in the collapsed state. A novel mapping technique based on collective coordinates is employed to highlight similarities and differences in the conformational ensemble of small oligomer structures. Elucidating the dynamical and polymorphic β-sheet oligomer conformations at atomistic detail furthermore suggests complementary sheet packing characteristics similar to steric zipper structures, but with a larger heterogeneity in the strand alignment pattern and sheet-to-sheet arrangements compared to the cross-β motif found in the fibrillar or crystalline states.     

Mitochondrial COI and morphological evidence for host specificity of the black cherry aphids Myzus cerasi (Fabricius, 1775) collected from different cherry tree species in Europe (Hemiptera,Aphididae)

Partial sequences of the mitochondrial COI gene of forty eight European and two Turkish population samples of Myzus cerasi from different winter hosts (Prunus spp.) were subjected to phylogenetic analyses. The analysed M. cerasi samples emerged as paraphyletic relative to a Myzus borealis sample used as an out-group, and formed two major clades in neighbor joining, maximum parsimony, maximum likelihood and Bayesian inference trees, corresponding to subspecies living specifically on Prunus avium and P. cerasus. Multivariate discriminant analysis (method of canonical variates) was applied to find out if morphological variation of samples correlated with mitochondrial COI and host plant information. Mean scores on the first two canonical variables clustered samples fully in accordance with their COI haplotypes and host plants confirming the existence of two morphologically similar winter host - specific subspecies of M. cerasi in Europe. No single morphological character enabled satisfactory discrimination between apterous viviparous females of the two subspecies. A three-character linear discriminant function enabled 92.37% correct identification of apterous viviparous females of M. cerasi cerasi (n = 118) and 93.64% of M. cerasi pruniavium (n = 110). A key for the morphological identification of the two subspecies is presented and their taxonomic status is discussed.     

Conformational Stability of Mammalian Prion Protein Amyloid Fibrils Is Dictated by a Packing Polymorphism within the Core Region

Mammalian prion strains are believed to arise from the propagation of distinct conformations of the misfolded prion protein PrP^Sc. One key operational parameter used to define differences between strains has been conformational stability of PrP^Sc as defined by resistance to thermal and/or chemical denaturation. However, the structural basis of these stability differences is unknown. To bridge this gap, we have generated two strains of recombinant human prion protein amyloid fibrils that show dramatic differences in conformational stability and have characterized them by a number of biophysical methods. Backbone amide hydrogen/deuterium exchange experiments revealed that, in sharp contrast to previously studied strains of infectious amyloid formed from the yeast prion protein Sup35, differences in β-sheet core size do not underlie differences in conformational stability between strains of mammalian prion protein amyloid. Instead, these stability differences appear to be dictated by distinct packing arrangements (i.e. steric zipper interfaces) within the amyloid core, as indicated by distinct x-ray fiber diffraction patterns and large strain-dependent differences in hydrogen/deuterium exchange kinetics for histidine side chains within the core region. Although this study was limited to synthetic prion protein amyloid fibrils, a similar structural basis for strain-dependent conformational stability may apply to brain-derived PrP^Sc, especially because large strain-specific differences in PrP^Sc stability are often observed despite a similar size of the PrP^Sc core region.     

The Granular Chloride Channel ClC-3 Is Permissive for Insulin Secretion

Insulin secretion from pancreatic β cells is dependent on maturation and acidification of the secretory granule, processes necessary for prohormone convertase cleavage of proinsulin. Previous studies in isolated β cells revealed that acidification may be dependent on the granule membrane chloride channel ClC-3, in a step permissive for a regulated secretory response. In this study, immuno-EM of β cells revealed colocalization of ClC-3 and insulin on secretory granules. Clcn3^−/− mice as well as isolated islets demonstrate impaired insulin secretion; Clcn3^−/− β cells are defective in regulated insulin exocytosis and granular acidification. Increased amounts of proinsulin were found in the majority of secretory granules in the Clcn3^−/− mice, while in Clcn3^+/+ cells, proinsulin was confined to the immature secretory granules. These results demonstrate that in pancreatic β cells, chloride channels, specifically ClC-3, are localized on insulin granules and play a role in insulin processing as well as insulin secretion through regulation of granular acidification.     

The genetic structure of red raspberry (<Emphasis Type="Italic">Rubus idaeus</Emphasis> L.) populations in Lithuania

The red raspberry (Rubus idaeus L.) is widely distributed in Lithuania and occupies a range of habitats. The presence of coadapted gene pools in local populations of R. idaeus is a question of interest not only to plant scientists, but also to plant breeders. In this study, we investigated the genetic structure of R. idaeus and the influence of local habitats on the genetic diversity within and among populations. Nineteen populations of R. idaeus were sampled from different habitats in various agroclimatic subregions of Lithuania, and analyzed using RAPD markers. 113 RAPD bands were identified among 315 individuals; 84.31% of these were polymorphic. The mean values of Shannon’s information index for different populations ranged from 0.341 to 0.455. Nei’s gene diversity established within populations averaged 0.266. An AMOVA revealed 74% of genetic variation among individuals within populations of R. idaeus, and 23% among populations. The remaining genetic variation was distributed among populations from different agroclimatic subregions (3%). The results of this study suggest that the genetic structure of R. idaeus populations in Lithuania may be influenced partially by isolation by distance as well as by local environmental conditions.     

Aploparaksis kornyushini n. sp. (Cestoda: Hymenolepididae), a parasite of the woodcock Scolopax rusticola (L.), and its life-cycle

Aploparaksis kornyushini n. sp. is described from a woodcock Scolopax rusticola L. from Lithuania, Russia (Tver' Region) and the Ukraine. Initially, one specimen of this tapeworm was described and figured by Kornyushin (1975) as A. scolopacis Yamaguti, 1935 together with another specimens belonging to the latter species. A. kornyushini n. sp. and A. scolopacis are morphologically very similar species. They can be distinguished by the slightly different length of the rostellar hooks and by the shape of the cirrus, which lacks basal bulbus in the new species. A. kornyushini can be readily distinguished from the remaining species of Aploparaksis Clerc, 1903 from woodcocks by the structure of its fully-developed embryophore, which has polar thickenings and two large or a few smaller lateral projection; this combination of characters is unknown for embryophores other Aploparaksis spp. (except for A. scolopacis). The life-cycle of A. kornyushini was studied under experimental conditions in Lithuania. The metacestodes were located under the chlorogogenous tissue of the intestine of Dendrobaena octaedra (Lumbricidae). The metacestode exhibits a pattern of postembryonal development typical for the cysticercoid modification termed an 'ovoid diplocyst'.     

Using lysozyme amyloid fibrils as a means of scavenging aggregation-inhibiting compounds

The aggregation of amyloidogenic proteins is linked to several amyloidoses, including neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. Currently there are very few effective cures or treatments available, despite countless screenings and clinical trials. One of the most challenging aspects of potential anti-amyloid drug discovery is finding which molecules are the actual inhibitors out of mixtures, which may contain hundreds of distinct compounds. Considering that anti-amyloid compounds would interact with the aggregate, this affinity could be used as a means of separating such compounds from ineffective ones. In this work, we attempt to scavenge potential aggregation-inhibiting molecules out of four, different complexity mixtures, ranging from oxidized gallic acid to tea extract, using lysozyme amyloid fibrils. We show that these compounds bind to aggregates with high affinity and can be later separated from them by different methods.