Glycosphingolipid synthesis requires FAPP2 transfer of glucosylceramide

The molecular machinery responsible for the generation of transport carriers moving from the Golgi complex to the plasma membrane relies on a tight interplay between proteins and lipids. Among the lipid-binding proteins of this machinery, we previously identified the four-phosphate adaptor protein FAPP2, the pleckstrin homology domain of which binds phosphatidylinositol 4-phosphate and the small GTPase ARF1. FAPP2 also possesses a glycolipid-transfer-protein homology domain. Here we show that human FAPP2 is a glucosylceramide-transfer protein that has a pivotal role in the synthesis of complex glycosphingolipids, key structural and signalling components of the plasma membrane. The requirement for FAPP2 makes the whole glycosphingolipid synthetic pathway sensitive to regulation by phosphatidylinositol 4-phosphate and ARF1. Thus, by coupling the synthesis of glycosphingolipids with their export to the cell surface, FAPP2 emerges as crucial in determining the lipid identity and composition of the plasma membrane.     

Structure of the yeast polarity protein Sro7 reveals a SNARE regulatory mechanism

Polarized exocytosis requires coordination between the actin cytoskeleton and the exocytic machinery responsible for fusion of secretory vesicles at specific sites on the plasma membrane. Fusion requires formation of a complex between a vesicle-bound R-SNARE and plasma membrane Qa, Qb and Qc SNARE proteins. Proteins in the lethal giant larvae protein family, including lethal giant larvae and tomosyn in metazoans and Sro7 in yeast, interact with Q-SNAREs and are emerging as key regulators of polarized exocytosis. The crystal structure of Sro7 reveals two seven-bladed WD40 beta-propellers followed by a 60-residue-long 'tail', which is bound to the surface of the amino-terminal propeller. Deletion of the Sro7 tail enables binding to the Qbc SNARE region of Sec9 and this interaction inhibits SNARE complex assembly. The N-terminal domain of Sec9 provides a second, high-affinity Sro7 interaction that is unaffected by the tail. The results suggest that Sro7 acts as an allosteric regulator of exocytosis through interactions with factors that control the tail. Sequence alignments indicate that lethal giant larvae and tomosyn have a two-beta-propeller fold similar to that of Sro7, but only tomosyn appears to retain the regulatory tail.     

Legionella pneumophila proteins that regulate Rab1 membrane cycling

Rab1 is a GTPase that regulates the transport of endoplasmic-reticulum-derived vesicles in eukaryotic cells. The intracellular pathogen Legionella pneumophila subverts Rab1 function to create a vacuole that supports bacterial replication by a mechanism that is not well understood. Here we describe L. pneumophila proteins that control Rab1 activity directly. We show that a region in the DrrA (defect in Rab1 recruitment A) protein required for recruitment of Rab1 to membranes functions as a guanine nucleotide dissociation inhibitor displacement factor. A second region of the DrrA protein stimulated Rab1 activation by functioning as a guanine nucleotide exchange factor. The LepB protein was found to inactivate Rab1 by stimulating GTP hydrolysis, indicating that LepB has GTPase-activating protein activity that regulates removal of Rab proteins from membranes. Thus, L. pneumophila encodes proteins that regulate three distinct biochemical reactions critical for Rab GTPase membrane cycling to redirect Rab1 to the pathogen-occupied vacuole and to control Rab1 function.     

小浪底水利枢纽工程投资分摊研究

水利枢纽工程投资费用合理分摊是正确计算各部门效益的前提,本文首先用主次分摊法,枢纽指标系数分摊法,效益比分摊法,可分离投资费用－剩余效益分摊法等常用方法对小浪底枢纽工程投资费用进行分摊。     

The genome of Theobroma cacao

We sequenced and assembled the draft genome of Theobroma cacao, an economically important tropical-fruit tree crop that is the source of chocolate. This assembly corresponds to 76% of the estimated genome size and contains almost all previously described genes, with 82% of these genes anchored on the 10 T. cacao chromosomes. Analysis of this sequence information highlighted specific expansion of some gene families during evolution, for example, flavonoid-related genes. It also provides a major source of candidate genes for T. cacao improvement. Based on the inferred paleohistory of the T. cacao genome, we propose an evolutionary scenario whereby the ten T. cacao chromosomes were shaped from an ancestor through eleven chromosome fusions.     

Common variants near ATM are associated with glycemic response to metformin in type 2 diabetes

Metformin is the most commonly used pharmacological therapy for type 2 diabetes. We report a genome-wide association study for glycemic response to metformin in 1,024 Scottish individuals with type 2 diabetes with replication in two cohorts including 1,783 Scottish individuals and 1,113 individuals from the UK Prospective Diabetes Study. In a combined meta-analysis, we identified a SNP, rs11212617, associated with treatment success (n = 3,920, P = 2.9 × 10(-9), odds ratio = 1.35, 95% CI 1.22-1.49) at a locus containing ATM, the ataxia telangiectasia mutated gene. In a rat hepatoma cell line, inhibition of ATM with KU-55933 attenuated the phosphorylation and activation of AMP-activated protein kinase in response to metformin. We conclude that ATM, a gene known to be involved in DNA repair and cell cycle control, plays a role in the effect of metformin upstream of AMP-activated protein kinase, and variation in this gene alters glycemic response to metformin.     

miR-124-3p is a chronic regulator of gene expression after brain injury

Traumatic brain injury (TBI) initiates molecular and cellular pathologies that underlie post-injury morbidities, including hippocampus-related memory decline and epileptogenesis. Non-coding small RNAs are master regulators of gene expression with the potential to affect multiple molecular pathways. To evaluate whether hippocampal gene expression networks are chronically regulated by microRNAs after TBI, we sampled the dentate gyrus of rats with severe TBI induced by lateral fluid-percussion injury 3 months earlier. Ingenuity pathway analysis revealed 30 upregulated miR-124-3p targets, suggesting that miR-124-3p is downregulated post-TBI (z-score?=?? 5.146, p?<?0.05). Droplet digital polymerase chain reaction (ddPCR) and in situ hybridization confirmed the chronic downregulation of miR-124-3p (p?<?0.05). Quantitative PCR analysis of two targets, Plp2 and Stat3, indicated that their upregulation correlated with the miR-124-3p downregulation (r?=?? 0.647, p?<?0.05; r?=?? 0.629, p?<?0.05, respectively). Immunohistochemical staining of STAT3 confirmed the increased protein expression. STRING analysis showed that 9 of the 30 miR-124-3p targets belonged to a STAT3 network. Reactome analysis and data mining connected the targets especially to inflammation and signal transduction. L1000CDS2 software revealed drugs (e.g., importazole, trichostatin A, and IKK-16) that could reverse the observed molecular changes. The translational value of our data was emphasized by in situ hybridization showing chronic post-traumatic downregulation of miR-124-3p in the dentate gyrus of TBI patients. Analysis of another brain injury model, status epilepticus, highlighted the fact that chronic downregulation of miR-124 is a common phenomenon after brain injury. Together, our findings indicate that miR-124-3p is a chronic modulator of molecular networks relevant to post-injury hippocampal pathologies in experimental models and in humans.     

Gain of function of TMEM16E/ANO5 scrambling activity caused by a mutation associated with gnathodiaphyseal dysplasia

Mutations in the human TMEM16E (ANO5) gene are associated both with the bone disease gnathodiaphyseal dysplasia (GDD; OMIM: 166260) and muscle dystrophies (OMIM: 611307, 613319). However, the physiological function of TMEM16E has remained unclear. We show here that human TMEM16E, when overexpressed in mammalian cell lines, displayed partial plasma membrane localization and gave rise to phospholipid scrambling (PLS) as well as non-selective ionic currents with slow time-dependent activation at highly depolarized membrane potentials. While the activity of wild-type TMEM16E depended on elevated cytosolic Ca²⁺ levels, a mutant form carrying the GDD-causing T513I substitution showed PLS and large time-dependent ion currents even at low cytosolic Ca²⁺ concentrations. Contrarily, mutation of the homologous position in the Ca²⁺-activated Cl^? channel TMEM16B paralog hardly affected its function. In summary, these data provide the first direct demonstration of Ca²⁺-dependent PLS activity for TMEM16E and suggest a gain-of-function phenotype related to a GDD mutation.     

The reproductive strategies of clausiliid land snails from Northern Vietnam (Gastropoda: Stylommatophora)

Under laboratory conditions we scrutinized the reproduction and development of two clausiliid land snail species from northern Vietnam: Phaedusa paviei (Morlet, 1892) and Oospira vanbuensis (Bavay and Dautzenberg, 1899). These species, very similar in shell size and shape, feature different reproductive modes. The former is viviparous, giving birth to one or two neonates on a single occasion, with the number of developing embryos retained in the reproductive tract ranging from 1 to 11. The embryonic shells are 1.8–4.7 mm in height. The latter species is oviparous and produces eggs in clutches (four to six per clutch). Hatching occurs 18–21 days after egg-laying. Both species exhibit a similar growth pattern: the ultimate shell size is attained after 6.5–8.5 months and reproduction starts 5–7 months later. The distribution of viviparous reproduction among the Phaedusinae and its taxonomic importance are discussed.