Protein kinase Cdelta and calmodulin regulate epidermal growth factor receptor recycling from early endosomes through Arp2/3 complex and cortactin

The intracellular trafficking of the epidermal growth factor receptor (EGFR) is regulated by a cross-talk between calmodulin (CaM) and protein kinase Cδ (PKCδ). On inhibition of CaM, PKCδ promotes the formation of enlarged early endosomes and blocks EGFR recycling and degradation. Here, we show that PKCδ impairs EGFR trafficking due to the formation of an F-actin coat surrounding early endosomes. The PKCδ-induced polymerization of actin is orchestrated by the Arp2/3 complex and requires the interaction of cortactin with PKCδ. Accordingly, inhibition of actin polymerization by using cytochalasin D or by overexpression of active cofilin, restored the normal morphology of the organelle and the recycling of EGFR. Similar results were obtained after down-regulation of cortactin and the sequestration of the Arp2/3 complex. Furthermore we demonstrate an interaction of cortactin with CaM and PKCδ, the latter being dependent on CaM inhibition. In summary, this study provides the first evidence that CaM and PKCδ organize actin dynamics in the early endosomal compartment, thereby regulating the intracellular trafficking of EGFR.     

Action du cordo-mésoderme dorsal sur la régionalisation et la différenciation du massif endodermique chezRana dalmatina Bon. (Amphibien Anoure)

Résumé Du cordo-mésoderme dorsal greffé sur la région ventrale d'un massif endodermique de même âge provoque sa différenciation locale (st. 17/neurula). Des néo-formations nombreuses et variées sont obtenues en faisant varier les caractéristiques du greffon (cordo-mésoderme) et du porte-greffe (endoderme). L'existence, la nature et le volume de ces néo-formations dépendent: de l'étroitesse et de la durée du contact greffon/porte-greffe, de l'âge du cordo-mésoderme et de l'âge de l'endoderme, des niveaux de contact, plus ou moins antérieurs, du greffon et du porte-greffe.Les résultats des greffes (st. 17) sont interprétés grâce à la construction de modèles théoriques. Ces modèles sont bâtis sur les quatre paramètres suivants: 1) l'existence de 2 facteurs morphogénétiques, l'un de nature endodermique et l'autre de nature cordo-mésodermique. Ces 2 facteurs sont responsables de l'apparition de néo-formations; 2) la localisation de ces 2 facteurs actifs dans les deux tiers (antérieur et moyen) de l'endoderme et du cordo-mésoderme; 3) la décroissance de l'activité des 2 facteurs selon l'axe antéro-postérieur de l'embryon; 4) le rôle différent de chacun de ces 2 facteurs. Le facteur endodermique déterminerait la nature et la taille des néo-formations; le facteur cordo-mésodermique jouerait un rôle stimulant.Une discussion est engagée sur la méthode, la démarche et l'intérêt de ce type d'interprétation des résultats.

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Effect of dorsal chordo-mesoderm on regionalisation and differentiation of the endodermal mass inRana dalmatina bon (Amphibia Anura)Elaboration of a theoretical model

Summary Chordo-mesoderm grafted onto the ventral area of yolk endoderm of the same age causes its local differentiation (Rana dalmatina: st. 17/neurula). Numerous and various neo-formations are achieved by variation of the grafted tissue (chordo-mesoderm) and host (endoderm) characteristics. The existence, the constitution and the volume of the neo-formations are dependant on: the tightness and the duration of the graft/host contact, the age of the chordo-mesoderm and the age of the endoderm, and the antero-posterior level of contact with grafted tissue and host.The results of the grafts (st. 17) are explained by the elaboration of a theoretical model. These models are elaborated according to four parameters: (1) the existence of two morphogenetic factors, one endodermal and the other mesodermal. These two factors are responsible for the constitution of neo-formations; (2) the localization of these two factors, active in the anterior and median thirds of the endoderm and the chorda-mesoderm; (3) decreasing activity of these two factors along to the antero-posterior axis of the embryo; (4) the different notes of each of these two factors. The endodermal factor might determine the constitution and the size of the neo-formations; the chordo-mesodermal factor might play a stimulatory role.The method, the procedure and the interpretation of this kind of results are discussed.

     

Complete genome sequence of the proteolytic Clostridium botulinum type A5 (B3') strain H04402 065

H04402 065 is one of a very small group of strains of proteolytic Clostridium botulinum that form type A5 neurotoxin. Here, we report the complete 3.9-Mb genome sequence and annotation of strain H04402 065, which was isolated from a botulism patient in the United Kingdom in 2004.     

Interaction of statins with phospholipid bilayers studied by solid-state NMR spectroscopy

Statins are drugs that specifically inhibit the enzyme HMG-CoA reductase and thereby reduce the concentration of low-density lipoprotein cholesterol, which represents a well-established risk factor for the development of atherosclerosis. The results of several clinical trials have shown that there are important intermolecular differences responsible for the broader pharmacologic actions of statins, even beyond HMG-CoA reductase inhibition. According to one hypothesis, the biological effects exerted by these compounds depend on their localization in the cellular membrane. The aim of the current work was to study the interactions of different statins with phospholipid membranes and to investigate their influence on the membrane structure and dynamics using various solid-state NMR techniques. Using ¹H NOESY MAS NMR, it was shown that atorvastatin, cerivastatin, fluvastatin, rosuvastatin, and some percentage of pravastatin intercalate the lipid-water interface of POPC membranes to different degrees. Based on cross-relaxation rates, the different average distribution of the individual statins in the bilayer was determined quantitatively. Investigation of the influence of the investigated statins on membrane structure revealed that lovastatin had the least effect on lipid packing and chain order, pravastatin significantly lowered lipid chain order, while the other statins slightly decreased lipid chain order parameters mostly in the middle segments of the phospholipid chains.     

Mapping marginal croplands suitable for cellulosic feedstock crops in the Great Plains,United States

Growing cellulosic feedstock crops (e.g., switchgrass) for biofuel is more environmentally sustainable than corn‐based ethanol. Specifically, this practice can reduce soil erosion and water quality impairment from pesticides and fertilizer, improve ecosystem services and sustainability (e.g., serve as carbon sinks), and minimize impacts on global food supplies. The main goal of this study was to identify high‐risk marginal croplands that are potentially suitable for growing cellulosic feedstock crops (e.g., switchgrass) in the US Great Plains (GP). Satellite‐derived growing season Normalized Difference Vegetation Index, a switchgrass biomass productivity map obtained from a previous study, US Geological Survey (USGS) irrigation and crop masks, and US Department of Agriculture (USDA) crop indemnity maps for the GP were used in this study. Our hypothesis was that croplands with relatively low crop yield but high productivity potential for switchgrass may be suitable for converting to switchgrass. Areas with relatively low crop indemnity (crop indemnity <$2 157 068) were excluded from the suitable areas based on low probability of crop failures. Results show that approximately 650 000 ha of marginal croplands in the GP are potentially suitable for switchgrass development. The total estimated switchgrass biomass productivity gain from these suitable areas is about 5.9 million metric tons. Switchgrass can be cultivated in either lowland or upland regions in the GP depending on the local soil and environmental conditions. This study improves our understanding of ecosystem services and the sustainability of cropland systems in the GP. Results from this study provide useful information to land managers for making informed decisions regarding switchgrass development in the GP.     

The second Ca(2+)-binding domain of NCX1 binds Mg2+ with high affinity

We report the effects of binding of Mg(2+) to the second Ca(2+)-binding domain (CBD2) of the sodium-calcium exchanger. CBD2 is known to bind two Ca(2+) ions using its Ca(2+)-binding sites I and II. Here, we show by nuclear magnetic resonance (NMR), circular dichroism, isothermal titration calorimetry, and mutagenesis that CBD2 also binds Mg(2+) at both sites, but with significantly different affinities. The results from Mg(2+)-Ca(2+) competition experiments show that Ca(2+) can replace Mg(2+) from site I, but not site II, and that Mg(2+) binding affects the affinity for Ca(2+). Furthermore, thermal unfolding circular dichroism data demonstrate that Mg(2+) binding stabilizes the domain. NMR chemical shift perturbations and (15)N relaxation data reveal that Mg(2+)-bound CBD2 adopts a state intermediate between the apo and fully Ca(2+)-loaded forms. Together, the data show that at physiological Mg(2+) concentrations CBD2 is loaded with Mg(2+) preferentially at site II, thereby stabilizing and structuring the domain and altering its affinity for Ca(2+).     

Absorption and retinol equivalence of beta-carotene in humans is influenced by dietary vitamin A intake

The effect of vitamin A supplements on metabolic behavior of an oral tracer dose of [14C]beta-carotene was investigated in a longitudinal test-retest design in two adults. For the test, each subject ingested 1 nmol of [14C]beta-carotene (100 nCi) in an emulsified olive oil-banana drink. Total urine and stool were collected for up to 30 days; concentration-time patterns of [14C]beta-carotene, [14C]retinyl esters, and [14C]retinol were determined for 46 days. On Day 53, the subjects were placed on a daily vitamin A supplement (10000 IU/day), and a second dose of [14C]beta-carotene (retest) was given on Day 74. All 14C determinations were made using accelerator mass spectrometry. In both subjects, the vitamin A supplementation was associated with three main effects: 1). increased apparent absorption: test versus retest values rose from 57% to 74% (Subject 1) and from 52% to 75% (Subject 2); 2). an approximately 10-fold reduction in urinary excretion; and 3). a lower ratio of labeled retinyl ester/beta-carotene concentrations in the absorptive phase. The molar vitamin A value of the dose for the test was 0.62 mol (Subject 1) and 0.54 mol (Subject 2) vitamin A to 1 mol beta-carotene. Respective values for the retest were 0.85 and 0.74. These results show that while less cleavage of beta-carotene occurred due to vitamin A supplementation, higher absorption resulted in larger molar vitamin A values.     

A reappraisal of sterol biosynthesis and metabolism in aphids

Aphids of Schizaphis graminum (Rondani) (biotype C) reared on its host-plant, Sorghum bicolor (L.) Moench, sequestered campesterol, stigmasterol and sitosterol. Aphids reared for 72 hr on holidic diets supplemented with [4-¹⁴C]-sitosterol contained both [¹⁴C]-sitosterol and [¹⁴C]-cholesterol, indicating that these aphids are capable of dealkylation at C-24. When aphids were reared on artificial diets containing [2-¹⁴C]-mevalonic acid, no detectable amounts of radioactively labelled desmethyl sterols, nor metabolic intermediates in sterol synthesis (i.e. squalene, 2,3-oxidosqualene, 4,4-dimethyl and 4-monomethyl sterols) were found to accumulate in their tissues. The relevance of these findings to previous research suggesting the ability of aphids, via their symbiotes, to synthesize sterols is discussed.