‘Should I stay or should I go?’: myosin V function in organelle trafficking

Actin- and microtubule-based motors can propel different cargos along filaments. Within cells, they control the distribution of membrane-bound compartments by performing complementary tasks. Organelles make long journeys along microtubules, with class V myosins ensuring their capture and their dispersal in actin-rich regions. Myosin Va is recruited on to diverse organelles, such as melanosomes and secretory vesicles, by a mechanism involving Rab GTPases. The role of myosin Va in the recruitment of secretory vesicles at the plasma membrane reveals that the cortical actin network cannot merely be seen as a physical barrier hindering vesicle access to release sites. In neurons, myosin Va controls the targeting of IP(3) (inositol 1,4,5-trisphosphate)-sensitive Ca(2+) stores to dendritic spines and the transport of mRNAs. These defects probably account for the severe neurological symptoms observed in Griscelli syndrome due to mutations in the MYO5A gene.     

Should I Stay or Should I Go? Eukaryotic Translation Initiation Factors 1 and 1A Control Start Codon Recognition

Start codon selection is a key step in translation initiation as it sets the reading frame for decoding. Two eukaryotic initiation factors, eIF1 and eIF1A, are key actors in this process. Recent work has elucidated many details of the mechanisms these factors use to control start site selection. eIF1 prevents the irreversible GTP hydrolysis that commits the ribosome to initiation at a particular codon. eIF1A both promotes and inhibits commitment through the competing influences of its two unstructured termini. Both factors perform their tasks through a variety of interactions with other components of the initiation machinery, in many cases mediated by the unstructured regions of the two proteins.     

46,X,t(Y;Y)(p1I;p1I）合并无精症一例报告

患者男性,28岁。因婚后3年不育而就 诊。患者为头胎足月顺产。其母孕期无有害物 质或放射线接触史,无发烧及病毒感染史,无服 药史。其父母非近亲婚配。家族中无不育或多 发畸形及智力低下者。患者共兄弟3人,其两 个弟弟均已结婚,并有正常生育能力。其妻作 过各项不孕症检查,未见异常。     

Cloning and functional analysis of chicory root fructan1‐exohydrolase I (1‐FEH I): a vacuolar enzyme derivedfrom a cell‐wall invertase ancestor? Mass fingerprint of the 1‐FEH I enzyme

This paper describes the cloning and functional analysis of chicory (Cichorium intybus L.) fructan 1-exohydrolase I cDNA (1-FEH I). To our knowledge it is the first plant FEH cloned. Full-length cDNA was obtained by a combination of RT-PCR, 5' and 3' RACE using primers based on N-terminal and conserved amino acid sequences. Electrophoretically purified 1-FEH I enzyme was further analyzed by in-gel trypsin digestion followed by matrix-assisted laser desorption ionization and electrospray time-of-flight tandem mass spectrometry. Functionality of the cDNA was demonstrated by heterologous expression in potato tubers. 1-FEH I takes a new, distinct position in the phylogenetic tree of plant glycosyl hydrolases being more homologous to cell-wall invertases (44-53%) than to vacuolar invertases (38-41%) and fructosyl transferases (33-38%). The 1-FEH I enzyme could not be purified from the apoplastic fluid at significantly higher levels than can be explained by cellular leakage. These and other data suggest a vacuolar localization for 1-FEH I. Also, the pI of the enzyme (6.5) is lower than expected from a typical cell-wall invertase. Unlike plant fructosyl transferases that are believed to have evolved from a vacuolar invertase, 1-FEH I might have evolved from a cell-wall invertase-like ancestor gene that later obtained a vacuolar targeting signal. 1-FEH I mRNA quantities increase in the roots throughout autumn, and especially when roots are stored at low temperature.     

Fishing for Accessory Binding Sites at GPCRs with ‘Loop‐Hooks’ – An Approach towards Selectivity? Part I

Receptor‐subtype selectivity is an important issue in medicinal chemistry and can become very difficult to achieve if the actual binding pockets of the respective receptors are highly conserved. For such cases, known unselective ligands could be equipped with a spacer that sticks outside the actual orthosteric binding pocket towards the extracellular loops. The end of the spacer bears certain functional groups to enable specific or unspecific interactions with the receptor residues outside the binding cavity. Our experiments indicated that it is possible to achieve selectivity within the dopamine D1 family with such ‘loop‐hooks’.     

Die<Emphasis Type="Italic">Pseudotextularia</Emphasis>-Zone der Bohrung Maasbüll I und ihre Foraminiferen-Fauna

The Foraminifera of thePseudotextularia-Zone from a borehole-section at Maasbüll (Schleswig), w. Germany, are described and figured. Between them are 9 new species of the generaHeterostomella, Gaudryina, Neoftabellina, Nodogenerina, Bolivina, Gavelinopsis, Globigerina — and 1 subspecies ofGavelinella pertusa.Faunas of two localities from Danmark, same horizon, are treated also. Comparisons are given with other faunas of same age, particularly from Egypt and Israel.     

Should I stay or should I go? Mycorrhizal plants are more likely to invest in long‐distance seed dispersal than non‐mycorrhizal plants

Seed dispersal and mycorrhizal associations are key mutualisms for the functioning and regeneration of plant communities; however, these processes have seldom been explored together. We hypothesised that obligatory mycorrhizal plants will be less likely to have long‐distance dispersal (LDD) syndromes since the probability of finding suitable mycorrhizal partners is likely to decrease with distance to the mother plant. We contrasted the mycorrhizal status and LDD syndromes for 1960 European plant species, using phylogenetically corrected log‐linear models. Contrary to our expectation, having specialised structures for LDD is more frequent in obligate mycorrhizal plants than in non‐mycorrhizal plants, revealing that lack of compatible mutualists does not constrain investment in LDD structures in the European Flora. Ectomycorrhizal plants associated with wind‐dispersing fungi are also more likely to have specialised structures for wind dispersal. Habitat specificity and narrower niche of non‐mycorrhizal plants might explain the smaller investment in specialised structures for seed dispersal.     

Mapitjakuna—Shall I Go Away From Myself Towards You? Being‐with and Looking‐at Across Cultural Divides

Anthropologists increasingly express links between individuals or collectivities through the discursively convenient prefix ‘‐inter’; inter‐personal, inter‐subjective, inter‐cultural, inter‐textual. However, attempts to describe the psychodynamics that effect the linkings that are integral to human social experience have not held pace. I want to suggest that a regard for the ontogenetic primary forms of encounter—looking, eating, playing—can substantiate the analysis of being a self among other selves within and across the boundaries of social worlds. Engaging a phenomenological and psychoanalytic perspective, this paper examines how We‐relationships have been variously structured by Pitjantjatjara Aborigines in encountering others at home and in Germany.     

Subcomplex Iλ Specifically Controls Integrated Mitochondrial Functions in Caenorhabditis elegans

Complex I dysfunction is a common, heterogeneous cause of human mitochondrial disease having poorly understood pathogenesis. The extensive conservation of complex I composition between humans and Caenorhabditis elegans permits analysis of individual subunit contribution to mitochondrial functions at both the whole animal and mitochondrial levels. We provide the first experimentally-verified compilation of complex I composition in C. elegans, demonstrating 84% conservation with human complex I. Individual subunit contribution to mitochondrial respiratory capacity, holocomplex I assembly, and animal anesthetic behavior was studied in C. elegans by RNA interference-generated knockdown of nuclear genes encoding 28 complex I structural subunits and 2 assembly factors. Not all complex I subunits directly impact respiratory capacity. Subcomplex Iλ subunits along the electron transfer pathway specifically control whole animal anesthetic sensitivity and complex II upregulation, proportionate to their relative impairment of complex I-dependent oxidative capacity. Translational analysis of complex I dysfunction facilitates mechanistic understanding of individual gene contribution to mitochondrial disease. We demonstrate that functional consequences of complex I deficiency vary with the particular subunit that is defective.     

Biochemical characterization of <Emphasis Type="Italic">Candida albicans</Emphasis> α-glucosidase I heterologously expressed in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Protein glycosylation is one of the most common post-translational modifications present in the eukaryotic cell. The N-linked glycosylation is a biosynthetic pathway where an oligosaccharide is added to asparagine residues within the endoplasmic reticulum. Upon addition of the N-linked glycan to nascent proteins, α-glucosidase I removes the outermost α1,2-glucose unit from the N-linked core Glc₃Man₉GlcNAc₂. We have previously demonstrated that the endoplasmic reticulum α-glucosidase I is required for normal cell wall composition, and virulence of the human pathogen Candida albicans. In spite of the importance of this enzyme for normal cell biology, little is known about its structure and the amino acids participating in enzyme catalysis. Here, a DNA fragment corresponding to the 3′-end fragment of C. albicans CWH41, the encoding gene for α-glucosidase I, was expressed in a bacterial system and the recombinant peptide showed α-glucosidase activity, despite lacking 419 amino acids from the N-terminal end. The biochemical characterisation of the recombinant enzyme showed that presence of hydroxyl groups at carbons 3 and 6, and orientation of hydroxyl moiety at C-2 are important for glucose recognition. Additionally, results suggest that cysteine rather than histidine residues are involved in the catalysis by the recombinant enzyme.     

Succinate is the controller of O<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack>/H<Subscript>2</Subscript>O<Subscript>2</Subscript> release at mitochondrial complex I : negative modulation by malate,positive by cyanide

Mitochondrial production of H₂O₂ is low with NAD substrates (glutamate/pyruvate, 3 and 2 mM) (G/P) and increases over ten times upon further addition of succinate, with the formation of a sigmoidal curve (semimaximal value at 290 μM, maximal H₂O₂ production at 600 μM succinate). Malate counteracts rapidly the succinate induced increased H₂O₂ release and moves the succinate dependent H₂O₂ production curve to the right. Nitric oxide (NO) and carbon monoxide (CO) are cytochrome c oxidase inhibitors which increase mitochondrial ROS production. Cyanide (CN⁻) was used to mimic NO and CO. In the presence of G/P and succinate (300 μM), CN⁻ progressively increased the H₂O₂ release rate, starting at 1.5 μM. The succinate dependent H₂O₂ production curve was moved to the left by 30 μM CN⁻. The V_max was little modified. We conclude that succinate is the controller of mitochondrial H₂O₂ production, modulated by malate and CN⁻. We propose that succinate promotes an interaction between Complex II and Complex I, which activates O₂⁻ production.     

On the generation of OH<Superscript>·</Superscript> radical species from H<Subscript>2</Subscript>O<Subscript>2</Subscript> by Cu(I) amyloid beta peptide model complexes: a DFT investigation

According to different studies, the interaction between amyloid β-peptide (Aβ) and copper ions could yield radical oxygen species production, in particular the highly toxic hydroxyl radical OH^· that is suspected to contribute to Alzheimer’s disease pathogenesis. Despite intensive experimental and computational studies, the nature of the interaction between copper and Aβ peptide, as well as the redox reactivity of the system, are still matter of debate. It was proposed that in Cu(II) → Cu(I) reduction the complex Cu(II)–Aβ could follow a multi-step conformational change with redox active intermediates that may be responsible for OH^· radical production from H₂O₂ through a Fenton-like process. The purpose of this work is to evaluate, using ab initio Density Functional Theory computations, the reactivity of different Cu(I)–Aβ coordination modes proposed in the literature, in terms of OH^· production. For each coordination model, we considered the corresponding H₂O₂ adduct and performed a potential energy surface scan along the reaction coordinate of O–O bond dissociation of the peroxide, resulting in the production of OH^· radical, obtaining reaction profiles for the evaluation of the energetic of the process. This procedure allowed us to confirm the hypothesis according to which the most populated Cu(I)–Aβ two-histidine coordination is not able to perform efficiently H₂O₂ reduction, while a less populated three-coordinated form would be responsible for the OH^· production. We show that coordination modes featuring a third nitrogen containing electron-donor ligand (an imidazole ring of an histidine residue is slightly favored over the N-terminal amine group) are more active towards H₂O₂ reduction.     

Diversity of<Emphasis Type="Italic"> Mhc</Emphasis> class I and IIB genes in house sparrows (<Emphasis Type="Italic">Passer domesticus</Emphasis>)

In order to understand the expression and evolution of host resistance to pathogens, we need to examine the links between genetic variability at the major histocompatibility complex (Mhc), phenotypic expression of the immune response and parasite resistance in natural populations. To do so, we characterized the Mhc class I and IIB genes of house sparrows with the goal of designing a PCR-based genotyping method for the Mhc genes using denaturing gradient gel electrophoresis (DGGE). The incredible success of house sparrows in colonizing habitats worldwide allows us to assess the importance of the variability of Mhc genes in the face of various pathogenic pressures. Isolation and sequencing of Mhc class I and IIB alleles revealed that house sparrows have fewer loci and fewer alleles than great reed warblers. In addition, the Mhc class I genes divided in two distinct lineages with different levels of polymorphism, possibly indicating different functional roles for each gene family. This organization is reminiscent of the chicken B complex and Rfp-Y system. The house sparrow Mhc hence appears to be intermediate between the great reed warbler and the chicken Mhc, both in terms of numbers of alleles and existence of within-class lineages. We specifically amplified one Mhc class I gene family and ran the PCR products on DGGE gels. The individuals screened displayed between one and ten DGGE bands, indicating that this method can be used in future studies to explore the ecological impacts of Mhc diversity.     

Recovery of photosystem I and II activities during re-hydration of lichen<Emphasis Type="Italic"> Hypogymnia physodes</Emphasis> thalli

Photochemical efficiencies of photosystem I (PSI) and photosystem II (PSII) were studied in dry thalli of the lichen Hypogymnia physodes and during their re-hydration. In dry thalli, PSII reaction centers are photochemically inactive, as evidenced by the absence of variable chlorophyll (Chl) fluorescence, whereas the primary electron donor of PSI, P700, exhibits irreversible oxidation under continuous light. Upon application of multiple- and, particularly, single-turnover pulses in dry lichen, P700 oxidation partially reversed, which indicated recombination between P700⁺ and the reduced acceptor F_X of PSI. Re-wetting of air-dried H. physodes initiated the gradual restoration of reversible light-induced redox reactions in both PSII and PSI, but the recovery was faster in PSI. Two slow components of P700⁺ reduction occurred after irradiation of partially and completely hydrated thalli with strong white light. In contrast, no slow component was found in the kinetics of re-oxidation of Q_A^–, the reduced primary acceptor of PSII, after exposure of such thalli to white light. This finding indicated the inability of PSII in H. physodes to provide the reduction of the plastoquinone pool to significant levels. It is concluded that slow alternative electron transport routes may contribute to the energetics of photosynthesis to a larger extent in H. physodes than in higher plants.Abbreviations A₀ and A₁ Primary acceptor chlorophyll and secondary electron acceptor phylloquinone - Chl a Chlorophyll a - F_m Maximal level of chlorophyll fluorescence when all PSII centers are closed - F_o Minimal level of fluorescence when all PSII centers are open after dark adaptation - FR Far-red - F_v Variable fluorescence (=F_m–F_o) - F_X, F_A, and F_B Iron–sulfur centers - MT pulse Multiple-turnover pulse - PS Photosystem - P700 Reaction center chlorophyll of PSI - Q_A Primary quinone acceptor of PSII - Q_B Secondary quinone acceptor of PSII - ST pulse Single-turnover pulse     

Should I stay or should I go? Hormonal control of nest abandonment in a long-lived bird, the Adélie penguin

According to life-history theory, long-lived birds should favor their survival over the current reproductive attempt, when breeding becomes too costly. In seabirds, incubation is often associated with spontaneous long-term fasting. Below a threshold in body reserves, hormonal and metabolic shift characteristics of a switch from lipid to protein utilization (phase III, PIII) occur. These metabolic changes are paralleled by nest abandonment and stimulation of refeeding behavior. Parental behavior is then under control of two hormones with opposite effects: corticosterone (CORT) and prolactin which stimulate foraging and incubation behavior, respectively.The aim of this study was to determine the respective role of these two hormones in nest abandonment by Adélie penguins. To this end, plasma hormone levels were measured before egg-laying and at departure from the colony (i.e. when birds were relieved by their partner or abandoned their nest), and related to nutritional state and incubation success.We found that males abandoning their nest in PIII presented high CORT levels and low prolactin levels. Interestingly, males which presented high plasma levels of prolactin in PIII did not abandon. We show that although CORT is the first hormone to be affected by prolonged energy constraints, the combined effects of high CORT and low prolactin levels are necessary for parents to favor self-maintenance and abandon the nest. We provide insights into time-course changes of the endocrine profile as PIII proceeds and report that reaching proteolytic late fasting is not sufficient to induce nest abandonment in a long-lived bird.     

Evaluation of novel <Superscript>99m</Superscript>Tc(I)-labeled homobivalent α-melanocyte-stimulating hormone analogs for melanocortin-1 receptor targeting

Abstract  

Aiming to apply the multivalency concept to melanoma imaging, we have assessed the in vivo melanocortin type 1 receptor (MC1R)-targeting properties of ^99mTc(I)-labeled homobivalent peptide conjugates which contain copies of the α-melanocyte-stimulating hormone (α-MSH) analog [Ac-Nle⁴, Asp⁵, d-Phe⁷, Lys¹¹]α-MSH_4–11 separated by linkers of different length (L ² nine atoms and L ³ 14 atoms). The MC1R-binding affinity of L ² and L ³ is significantly higher than that of the monovalent conjugate L ¹ . Metallation of these conjugates yielded the complexes fac-[M(CO)₃(k³-L)]⁺ (M is ^99mTc/Re; 1/1a, L is L ¹ ; 2/2a, L is L ² ; 3/3a, L is L ³ ), with IC₅₀ values in the subnanomolar and nanomolar range. The MC1R-mediated internalization of 2 and 3 is higher than that of 1 in B16F1 melanoma cells. Biodistribution studies in melanoma-bearing mice have shown low nonspecific accumulation with a tumor uptake that correlates with IC₅₀ values. However, no correlation between tumor uptake and valency was found. Nevertheless, 2 displayed the highest tumor retention, and the best tumor to nontarget organ ratios.