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By admin, on February 22nd, 2012
J Biol Chem. 2012 Feb 17;
Zhao Y, Wang Y, Hu J, Zhang X, Zhang YW
Accumulation of the neurotoxic β-amyloid (Aβ) peptide in the brain is central to the pathogenesis of Alzheimer disease (AD). Aβ is derived from the β-amyloid precursor protein (APP) through sequential cleavages by β- and γ-secretases; and the production of Aβ is greatly affected by the subcellular localization of these factors. CUTA, the mammalian cutA divalent cation tolerance homolog (E.coli), has been proposed to mediate acetylcholinesterase activity and copper homeostasis which are important in AD pathology. However, the exact function of CUTA remains largely unclear. Here we show that human CUTA has several variants that differ in their amino- (N-) terminal length and are separated as heavy (H) and light (L) components. The H component has the longest N-terminus and is membrane-associated, whereas the L component is N-terminally truncated at various sites and localized in the cytosol. Importantly, we demonstrate that the H component of CUTA interacts through its N-terminus with the transmembrane domain of β-site APP cleaving enzyme 1 (BACE1), the putative β-secretase, mainly in the Golgi/trans-Golgi network (TGN). Overexpression and RNA interference knockdown of CUTA can reduce and increase BACE1-mediated APP processing/Aβ secretion, respectively. RNA interference of CUTA decelerates intracellular trafficking of BACE1 from the Golgi/TGN to the cell surface and reduces the steady-state level of cell surface BACE1. Our results identify the H component of CUTA as a novel BACE1-interacting protein that mediates the intracellular trafficking of BACE1 and the processing of APP to Aβ.
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CutA divalent cation tolerance homolog (E. coli) (CUTA) regulates β-cleavage of β-amyloid precursor protein (APP) through interacting with β-Site APP cleaving protein 1 (BACE1).
By admin, on February 22nd, 2012
J Biol Chem. 2012 Feb 17;
Zhao Y, Wang Y, Hu J, Zhang X, Zhang YW
Accumulation of the neurotoxic β-amyloid (Aβ) peptide in the brain is central to the pathogenesis of Alzheimer disease (AD). Aβ is derived from the β-amyloid precursor protein (APP) through sequential cleavages by β- and γ-secretases; and the production of Aβ is greatly affected by the subcellular localization of these factors. CUTA, the mammalian cutA divalent cation tolerance homolog (E.coli), has been proposed to mediate acetylcholinesterase activity and copper homeostasis which are important in AD pathology. However, the exact function of CUTA remains largely unclear. Here we show that human CUTA has several variants that differ in their amino- (N-) terminal length and are separated as heavy (H) and light (L) components. The H component has the longest N-terminus and is membrane-associated, whereas the L component is N-terminally truncated at various sites and localized in the cytosol. Importantly, we demonstrate that the H component of CUTA interacts through its N-terminus with the transmembrane domain of β-site APP cleaving enzyme 1 (BACE1), the putative β-secretase, mainly in the Golgi/trans-Golgi network (TGN). Overexpression and RNA interference knockdown of CUTA can reduce and increase BACE1-mediated APP processing/Aβ secretion, respectively. RNA interference of CUTA decelerates intracellular trafficking of BACE1 from the Golgi/TGN to the cell surface and reduces the steady-state level of cell surface BACE1. Our results identify the H component of CUTA as a novel BACE1-interacting protein that mediates the intracellular trafficking of BACE1 and the processing of APP to Aβ.
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CutA divalent cation tolerance homolog (E. coli) (CUTA) regulates β-cleavage of β-amyloid precursor protein (APP) through interacting with β-Site APP cleaving protein 1 (BACE1).
By admin, on February 21st, 2012
Mol Microbiol. 2012 Feb 13;
Takeshita N, Diallinas G, Fischer R
Apical sterol-rich plasma membrane domains (SRDs), which can be viewed using the sterol-binding fluorescent dye filipin, are gaining attention for their important roles in polarized growth of filamentous fungi. The microdomain scaffolding protein flotillin/reggie and related stomatin were thought to be good candidates involved in the formation of SRDs. Here, we show that the flotillin/reggie orthologue FloA tagged with GFP localized as stable dots along the plasma membrane except hyphal tips. Deletion of floA reduced the growth rate, often resulted in irregularly shaped hyphae and impaired SRDs. In contrast, the stomatin orthologue StoA, tagged with GFP, localized at the cortex of young branch tips and at the subapical cortex in long hyphal tips, and was transported bi-directionally along microtubules on endosomes. Deletion of stoA resulted in irregular hyphal morphology and increased branching especially in young hyphae, but did not obviously affect SRDs. Double deletion of floA and stoA enhanced the defects of growth and hyphal morphology. Our data suggest that the plasma membrane of hyphal tips and in subapical regions are distinct and that FloA is involved in membrane compartmentalization and probably indirectly in SRD maintenance.
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The role of flotillin FloA and stomatin StoA in the maintenance of apical sterol-rich membrane domains and polarity in the filamentous fungus Aspergillus nidulans.
By admin, on February 21st, 2012
Mol Microbiol. 2012 Feb 13;
Takeshita N, Diallinas G, Fischer R
Apical sterol-rich plasma membrane domains (SRDs), which can be viewed using the sterol-binding fluorescent dye filipin, are gaining attention for their important roles in polarized growth of filamentous fungi. The microdomain scaffolding protein flotillin/reggie and related stomatin were thought to be good candidates involved in the formation of SRDs. Here, we show that the flotillin/reggie orthologue FloA tagged with GFP localized as stable dots along the plasma membrane except hyphal tips. Deletion of floA reduced the growth rate, often resulted in irregularly shaped hyphae and impaired SRDs. In contrast, the stomatin orthologue StoA, tagged with GFP, localized at the cortex of young branch tips and at the subapical cortex in long hyphal tips, and was transported bi-directionally along microtubules on endosomes. Deletion of stoA resulted in irregular hyphal morphology and increased branching especially in young hyphae, but did not obviously affect SRDs. Double deletion of floA and stoA enhanced the defects of growth and hyphal morphology. Our data suggest that the plasma membrane of hyphal tips and in subapical regions are distinct and that FloA is involved in membrane compartmentalization and probably indirectly in SRD maintenance.
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The role of flotillin FloA and stomatin StoA in the maintenance of apical sterol-rich membrane domains and polarity in the filamentous fungus Aspergillus nidulans.
By admin, on February 21st, 2012
Plant Cell Environ. 2012 Feb 15;
Xu W, Shi W, Jia L, Liang J, Zhang J
14-3-3 proteins are a large family of proteins but exact roles of their members in plant response to abiotic stresses are not clear, especially under nutrient deficiency. We investigated the expressions of all the tomato 14-3-3 gene family members (TFT1 – TFT12) under low-phosphorus-stress and found that TFT6 belongs to the later responsive gene while TFT7 belongs to the early responsive gene. When the two genes were separately introduced into Arabidopsis and over-expressed, their plant growth under low-phosphorus-stress was much enhanced compared to wild-type plant. TFT6 over-expressing plants showed reduced starch synthase activity, reduced starch content but enhanced sucrose loading into phloem in the shoot under low-phosphorus-stress. TFT7 over-expressing plants had much enhanced H(+) flux along their root tip and activity of plasma membrane H(+) -ATPase in the roots under low-phosphorus-stress. Our results suggest that TFT6 and TFT7 play different roles in plant adaption to low-phosphorus-stress. TFT6 acts mainly in leaves and is involved in the systemic response to low-phosphorus-stress by regulating leaf carbon allocation and increasing phloem sucrose transport to promote root growth, while TFT7 directly functions in root by activating root plasma membrane H(+) -ATPase to release more protons under low-phosphorus-stress. © 2012 Blackwell Publishing Ltd.
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TFT6 and TFT7, two different members of tomato 14-3-3 gene family, play distinct roles in plant adaption to low phosphorus stress.
By admin, on February 21st, 2012
Plant Cell Environ. 2012 Feb 15;
Xu W, Shi W, Jia L, Liang J, Zhang J
14-3-3 proteins are a large family of proteins but exact roles of their members in plant response to abiotic stresses are not clear, especially under nutrient deficiency. We investigated the expressions of all the tomato 14-3-3 gene family members (TFT1 – TFT12) under low-phosphorus-stress and found that TFT6 belongs to the later responsive gene while TFT7 belongs to the early responsive gene. When the two genes were separately introduced into Arabidopsis and over-expressed, their plant growth under low-phosphorus-stress was much enhanced compared to wild-type plant. TFT6 over-expressing plants showed reduced starch synthase activity, reduced starch content but enhanced sucrose loading into phloem in the shoot under low-phosphorus-stress. TFT7 over-expressing plants had much enhanced H(+) flux along their root tip and activity of plasma membrane H(+) -ATPase in the roots under low-phosphorus-stress. Our results suggest that TFT6 and TFT7 play different roles in plant adaption to low-phosphorus-stress. TFT6 acts mainly in leaves and is involved in the systemic response to low-phosphorus-stress by regulating leaf carbon allocation and increasing phloem sucrose transport to promote root growth, while TFT7 directly functions in root by activating root plasma membrane H(+) -ATPase to release more protons under low-phosphorus-stress. © 2012 Blackwell Publishing Ltd.
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TFT6 and TFT7, two different members of tomato 14-3-3 gene family, play distinct roles in plant adaption to low phosphorus stress.
By admin, on February 21st, 2012
Prostate Cancer Prostatic Dis. 2012 Feb 14;
Price RS, Cavazos DA, De Angel RE, Hursting SD, Degraffenried LA
Background:Obesity is associated with larger tumors, shorter time to PSA failure, and higher Gleason scores. However, the mechanism(s) by which obesity promotes aggressive prostate cancer remains unknown. We hypothesize that circulating factors related to obesity promote prostate cancer progression by modulating components of the metastatic cascade.Methods:Male C57BL/6 mice (6 weeks) were fed an ad libitum diet-induced obesity (60% fat) or control diet (10% fat) for 12 weeks. Serum was collected, metabolic and inflammatory proteins were measured by an antibody array. Sera were used to measure, in vitro, characteristics of a metastatic phenotype.Results:Comparable to obese men, obese sera contained higher levels or leptin, vascular endothelial growth factor, PAI-1, interleukin-6 (IL-6) and lower levels of testosterone. In prostate cells, serum was used to assess: proliferation, invasion, migration, epithelial-mesenchymal-transition (EMT) and matrix metalloproteinase (MMP) activity. LNCaP and PacMetUT1 cells exposed to obese sera increased proliferation, whereas PrEC and DU145 were unaffected. LNCaP, PacMetUT1 and DU145 cancer cells exposed to obese sera resulted in increased invasion, migration and MMP-9 activity. Prostate cancer cells exposed to obese sera showed increased vimentin, dispersion of e-cadherin and β-catenin from the plasma membrane.Conclusion:We report, prostate cancer cells exposed to sera from obese mice increases proliferation, invasion, migration, MMP activity and induces changes in proteins critical for EMT.Prostate Cancer and Prostatic Diseases advance online publication, 14 February 2012; doi:10.1038/pcan.2011.54.
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Obesity-related systemic factors promote an invasive phenotype in prostate cancer cells.
By admin, on February 21st, 2012
Prostate Cancer Prostatic Dis. 2012 Feb 14;
Price RS, Cavazos DA, De Angel RE, Hursting SD, Degraffenried LA
Background:Obesity is associated with larger tumors, shorter time to PSA failure, and higher Gleason scores. However, the mechanism(s) by which obesity promotes aggressive prostate cancer remains unknown. We hypothesize that circulating factors related to obesity promote prostate cancer progression by modulating components of the metastatic cascade.Methods:Male C57BL/6 mice (6 weeks) were fed an ad libitum diet-induced obesity (60% fat) or control diet (10% fat) for 12 weeks. Serum was collected, metabolic and inflammatory proteins were measured by an antibody array. Sera were used to measure, in vitro, characteristics of a metastatic phenotype.Results:Comparable to obese men, obese sera contained higher levels or leptin, vascular endothelial growth factor, PAI-1, interleukin-6 (IL-6) and lower levels of testosterone. In prostate cells, serum was used to assess: proliferation, invasion, migration, epithelial-mesenchymal-transition (EMT) and matrix metalloproteinase (MMP) activity. LNCaP and PacMetUT1 cells exposed to obese sera increased proliferation, whereas PrEC and DU145 were unaffected. LNCaP, PacMetUT1 and DU145 cancer cells exposed to obese sera resulted in increased invasion, migration and MMP-9 activity. Prostate cancer cells exposed to obese sera showed increased vimentin, dispersion of e-cadherin and β-catenin from the plasma membrane.Conclusion:We report, prostate cancer cells exposed to sera from obese mice increases proliferation, invasion, migration, MMP activity and induces changes in proteins critical for EMT.Prostate Cancer and Prostatic Diseases advance online publication, 14 February 2012; doi:10.1038/pcan.2011.54.
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Obesity-related systemic factors promote an invasive phenotype in prostate cancer cells.
By admin, on February 21st, 2012
Plant Physiol. 2012 Feb 13;
Qi D, Deyoung BJ, Innes RW
The Arabidopsis RPS5 disease resistance protein mediates recognition of the Pseudomonas syringae effector protein AvrPphB. RPS5 belongs to the coiled-coil-nucleotide binding site-leucine-rich repeat (CC-NBS-LRR) family and is activated by AvrPphB-mediated cleavage of the protein kinase PBS1. Here we present a structure-function analysis of the CC and LRR domains of RPS5 using transient expression assays in Nicotiana benthamiana. We found that substituting the CC domain of RPS2 for the RPS5 CC domain did not alter RPS5 specificity and only moderately reduced its ability to activate programmed cell death, suggesting that the CC domain does not play a direct role in the recognition of PBS1 cleavage. Analysis of an RPS5-super Yellow Fluorescent Protein (sYFP) fusion revealed that RPS5 localizes to the plasma membrane (PM). Alanine substitutions of predicted myristoylation (glycine 2) and palmitoylation residues (cysteine 4) affected RPS5 PM localization, protein stability, and function in an additive manner, indicating that PM localization is essential to RPS5 function. The first 20 amino acids of RPS5 were sufficient for directing sYFP to the PM. C-terminal truncations of RPS5 revealed that the first 4 LRR repeats are sufficient for inhibiting RPS5 autoactivation; however, the complete LRR domain was required for recognition of PBS1 cleavage. Substitution of the RPS2 LRR domain resulted in autoactivation of RPS5, indicating that the LRR domain must co-evolve with the NBS domain. We conclude that the RPS5 LRR domain functions to suppress RPS5 activation in the absence of PBS1 cleavage, and promotes RPS5 activation in its presence.
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Structure-Function Analysis of the Coiled-Coil and Leucine-Rich Repeat Domains of the RPS5 Disease Resistance Protein.
By admin, on February 21st, 2012
Plant Physiol. 2012 Feb 13;
Qi D, Deyoung BJ, Innes RW
The Arabidopsis RPS5 disease resistance protein mediates recognition of the Pseudomonas syringae effector protein AvrPphB. RPS5 belongs to the coiled-coil-nucleotide binding site-leucine-rich repeat (CC-NBS-LRR) family and is activated by AvrPphB-mediated cleavage of the protein kinase PBS1. Here we present a structure-function analysis of the CC and LRR domains of RPS5 using transient expression assays in Nicotiana benthamiana. We found that substituting the CC domain of RPS2 for the RPS5 CC domain did not alter RPS5 specificity and only moderately reduced its ability to activate programmed cell death, suggesting that the CC domain does not play a direct role in the recognition of PBS1 cleavage. Analysis of an RPS5-super Yellow Fluorescent Protein (sYFP) fusion revealed that RPS5 localizes to the plasma membrane (PM). Alanine substitutions of predicted myristoylation (glycine 2) and palmitoylation residues (cysteine 4) affected RPS5 PM localization, protein stability, and function in an additive manner, indicating that PM localization is essential to RPS5 function. The first 20 amino acids of RPS5 were sufficient for directing sYFP to the PM. C-terminal truncations of RPS5 revealed that the first 4 LRR repeats are sufficient for inhibiting RPS5 autoactivation; however, the complete LRR domain was required for recognition of PBS1 cleavage. Substitution of the RPS2 LRR domain resulted in autoactivation of RPS5, indicating that the LRR domain must co-evolve with the NBS domain. We conclude that the RPS5 LRR domain functions to suppress RPS5 activation in the absence of PBS1 cleavage, and promotes RPS5 activation in its presence.
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Structure-Function Analysis of the Coiled-Coil and Leucine-Rich Repeat Domains of the RPS5 Disease Resistance Protein.
By admin, on February 20th, 2012
J Mol Biol . 2012 Jan 30; Papadakos G, Housden NG, Lilly KJ, Kaminska R, Kleanthous C TolB and Pal are members of the Tol-Pal system that spans the cell envelope of Gram-negative bacteria and contributes to the stability and integrity of the bacterial outer membrane (OM).
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Kinetic Basis for the Competitive Recruitment of TolB by the Intrinsically Disordered Translocation Domain of Colicin E9.
By admin, on February 20th, 2012
J Mol Biol . 2012 Jan 30; Papadakos G, Housden NG, Lilly KJ, Kaminska R, Kleanthous C TolB and Pal are members of the Tol-Pal system that spans the cell envelope of Gram-negative bacteria and contributes to the stability and integrity of the bacterial outer membrane (OM).
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Kinetic Basis for the Competitive Recruitment of TolB by the Intrinsically Disordered Translocation Domain of Colicin E9.
By admin, on February 20th, 2012
Free Radic Biol Med. 2012 Feb 1;
Berrougui H, Loued S, Khalil A
Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme thought to make a major contribution to the antioxidant and anti-inflammatory capacities of HDLs. However, the role of PON1 in the modulation of cholesterol efflux is poorly understood. The aim of our study was to investigate the involvement of PON1 in the regulation of cholesterol efflux, especially the mechanism by which it modulates HDL-mediated cholesterol transport. The enrichment of HDL(3) with human PON1 enhanced, in a dose-dependent manner, cholesterol efflux from THP-1 macrophage-like cells and ABCA1-enriched J774 macrophages. Moreover, an additive effect was observed when ABCA1-enriched J774 macrophages were incubated with both PON1 and apo-AI. Interestingly, PON1 alone was able to mediate cholesterol efflux from J774 macrophages and to upregulate ABCA1 expression on J774 macrophages. Immunofluorescence measurement showed an increase in PON1 levels in the cytoplasm of J774 macrophages overexpressing ABCA1. PON1 used an apo-AI-like mechanism to modulate cholesterol efflux from rapid and slow efflux pools derived from the lipid raft and nonraft domains of the plasma membrane, respectively. This was supported by the fact that ABCA1 protein was incrementally expressed by J774 macrophages within the first few hours of incubation with cholesterol-loaded J774 macrophages and that cyclodextrin significantly inhibited the capacity of PON1 to modulate cholesterol efflux from macrophages. This finding suggested that PON1 plays an important role in the antiatherogenic properties of HDLs and may exert its protective function outside the lipoprotein environment.
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Purified human paraoxonase-1 interacts with plasma membrane lipid rafts and mediates cholesterol efflux from macrophages.
By admin, on February 20th, 2012
Free Radic Biol Med. 2012 Feb 1;
Berrougui H, Loued S, Khalil A
Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme thought to make a major contribution to the antioxidant and anti-inflammatory capacities of HDLs. However, the role of PON1 in the modulation of cholesterol efflux is poorly understood. The aim of our study was to investigate the involvement of PON1 in the regulation of cholesterol efflux, especially the mechanism by which it modulates HDL-mediated cholesterol transport. The enrichment of HDL(3) with human PON1 enhanced, in a dose-dependent manner, cholesterol efflux from THP-1 macrophage-like cells and ABCA1-enriched J774 macrophages. Moreover, an additive effect was observed when ABCA1-enriched J774 macrophages were incubated with both PON1 and apo-AI. Interestingly, PON1 alone was able to mediate cholesterol efflux from J774 macrophages and to upregulate ABCA1 expression on J774 macrophages. Immunofluorescence measurement showed an increase in PON1 levels in the cytoplasm of J774 macrophages overexpressing ABCA1. PON1 used an apo-AI-like mechanism to modulate cholesterol efflux from rapid and slow efflux pools derived from the lipid raft and nonraft domains of the plasma membrane, respectively. This was supported by the fact that ABCA1 protein was incrementally expressed by J774 macrophages within the first few hours of incubation with cholesterol-loaded J774 macrophages and that cyclodextrin significantly inhibited the capacity of PON1 to modulate cholesterol efflux from macrophages. This finding suggested that PON1 plays an important role in the antiatherogenic properties of HDLs and may exert its protective function outside the lipoprotein environment.
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Purified human paraoxonase-1 interacts with plasma membrane lipid rafts and mediates cholesterol efflux from macrophages.
By admin, on February 20th, 2012
Curr Top Microbiol Immunol . 2012 Feb 8; Hogardt M, Heesemann J Pseudomonas aeruginosa is the leading pathogen of chronic cystic fibrosis (CF) lung infection. Life-long persistance of P
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Microevolution of Pseudomonas aeruginosa to a Chronic Pathogen of the Cystic Fibrosis Lung.
By admin, on February 20th, 2012
J Phys Chem B . 2012 Feb 15; Horst R, Stanczak P, Serrano P, Wüthrich K ABSTRACT: Aqueous solutions of the detergent Fos-10 (n-decylphosphocholine) without and with addition of the integral membrane protein (IMP) OmpX (outer membrane protein X) have been characterized using pulsed field gradient-stimulated echo (PFG-STE) NMR experiments for measurements of translational diffusion coefficients. Effective diffusion coefficients for Fos-10 micelles in the absence of OmpX were obtained by observation of NMR signals from 10-bromodecan-1-ol that had been inserted into the micelles, and in the presence of OmpX by NMR observation of the protein.
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Translational Diffusion Measurements by Micro-coil NMR in Aqueous Solutions of the Fos-10 Detergent-Solubilized Membrane Protein OmpX.
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