|
|
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.
More:
Purified human paraoxonase-1 interacts with plasma membrane lipid rafts and mediates cholesterol efflux from macrophages.
By admin, on February 15th, 2012
Hum Vaccin Immunother . 2012 Mar 1; 8(3): Sizemore D, Warner E, Lawrence J, Thomas LJ, Roland K, Killeen K Preclinical studies evaluating plague vaccine candidates have demonstrated that the F1 and V antigen proteins of Yersinia pestis provide protection against challenge from virulent strains. Live-attenuated ΔphoP/Q Salmonella typhimurium recombinants expressing either F1, V antigen, F1 plus V antigen, or a F1-V fusion from Asd (+) balanced-lethal plasmids were constructed
See more here:
Construction and screening of attenuated ΔphoP/Q Salmonella typhimurium vectored plague vaccine candidates.
By admin, on February 15th, 2012
Hum Vaccin Immunother . 2012 Mar 1; 8(3): Sizemore D, Warner E, Lawrence J, Thomas LJ, Roland K, Killeen K Preclinical studies evaluating plague vaccine candidates have demonstrated that the F1 and V antigen proteins of Yersinia pestis provide protection against challenge from virulent strains.
Go here to read the rest:
Construction and screening of attenuated ΔphoP/Q Salmonella typhimurium vectored plague vaccine candidates.
By admin, on February 15th, 2012
EMBO J. 2012 Feb 10;
Jouannet V, Moreno AB, Elmayan T, Vaucheret H, Crespi MD, Maizel A
Formation of trans-acting small interfering RNAs (ta-siRNAs) from the TAS3 precursor is triggered by the AGO7/miR390 complex, which primes TAS3 for conversion into double-stranded RNA by the RNA-dependent RNA polymerase RDR6 and SGS3. These ta-siRNAs control several aspects of plant development. The mechanism routing AGO7-cleaved TAS3 precursor to RDR6/SGS3 and its subcellular organization are unknown. We show that AGO7 accumulates together with SGS3 and RDR6 in cytoplasmic siRNA bodies that are distinct from P-bodies. siRNA bodies colocalize with a membrane-associated viral protein and become positive for stress-granule markers upon stress-induced translational repression, this suggests that siRNA bodies are membrane-associated sites of accumulation of mRNA stalled during translation. AGO7 congregates with miR390 and SGS3 in membranes and its targeting to the nucleus prevents its accumulation in siRNA bodies and ta-siRNA formation. AGO7 is therefore required in the cytoplasm and membranous siRNA bodies for TAS3 processing, revealing a hitherto unknown role for membrane-associated ribonucleoparticles in ta-siRNA biogenesis and AGO action in plants.
Read the original:
Cytoplasmic Arabidopsis AGO7 accumulates in membrane-associated siRNA bodies and is required for ta-siRNA biogenesis.
By admin, on February 4th, 2012
PLoS One . 2012; 7(1): e30767 Nakamura Y, Kitamura N, Shinogi D, Yoshida M, Goda O, Murai R, Kamino H, Arakawa H Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins
Read the original:
BNIP3 and NIX Mediate Mieap-Induced Accumulation of Lysosomal Proteins within Mitochondria.
By admin, on February 4th, 2012
PLoS One . 2012; 7(1): e30767 Nakamura Y, Kitamura N, Shinogi D, Yoshida M, Goda O, Murai R, Kamino H, Arakawa H Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins.
Read the original here:
BNIP3 and NIX Mediate Mieap-Induced Accumulation of Lysosomal Proteins within Mitochondria.
By admin, on January 25th, 2012
PLoS One. 2012; 7(1): e30425
Hossain Z, Amyot L, McGarvey B, Gruber M, Jung J, Hannoufa A
The eukaryotic translation elongation factor eEF-1Bβ1 (EF1Bβ) is a guanine nucleotide exchange factor that plays an important role in translation elongation. In this study, we show that the EF1Bβ protein is localized in the plasma membrane and cytoplasm, and that the transcripts should be expressed in most tissue types in seedlings. Sectioning of the inflorescence stem revealed that EF1Bβ predominantly localizes to the xylem vessels and in the interfascicular cambium. EF1Bβ gene silencing in efβ caused a dwarf phenotype with 38% and 20% reduction in total lignin and crystalline cellulose, respectively. This loss-of-function mutant also had a lower S/G lignin monomer ratio relative to wild type plants, but no changes were detected in a gain-of-function mutant transformed with the EF1Bβ gene. Histochemical analysis showed a reduced vascular apparatus, including smaller xylem vessels in the inflorescence stem of the loss-of-function mutant. Over-expression of EF1Bβ in an eli1 mutant background restored a WT phenotype and abolished ectopic lignin deposition as well as cell expansion defects in the mutant. Taken together, these data strongly suggest a role for EF1Bβ in plant development and cell wall formation in Arabidopsis.
Link:
The Translation Elongation Factor eEF-1Bβ1 Is Involved in Cell Wall Biosynthesis and Plant Development in Arabidopsis thaliana.
By admin, on January 25th, 2012
Haematologica . 2012 Jan 22; Necchi V, Minelli A, Sommi P, Vitali A, Caruso R, Longoni D, Frau MR, Nasi C, De Gregorio F, Zecca M, Ricci V, Danesino C, Solcia E Background. Shwachman-Diamond syndrome is an autosomal recessive disorder with severe bone marrow dysfunction causing neutropenia and increased leukemia risk.
View original post here:
Ubiquitin-proteasome-rich cytoplasmic structures in neutrophils of patients with Shwachman-Diamond syndrome.
By admin, on January 19th, 2012
FEBS J . 2012 Jan 17; Reusch RN Outer membrane protein A (OmpA) of Escherichia coli is a paradigm for the biogenesis of outer membrane proteins; however, the structure and assembly of OmpA have remained controversial. A review of studies to date supports the hypothesis that native OmpA is a single-domain large pore, while a two-domain narrow pore structure is a folding intermediate or minor conformer
Go here to see the original:
Insights into the Structure and Assembly of Escherichia coli Outer Membrane Protein A.
By admin, on January 17th, 2012
Exp Cell Res. 2012 Jan 5;
Houghton FJ, Bellingham SA, Hill AF, Bourges D, Ang DK, Gemetzis T, Gasnereau I, Gleeson PA
Regulation of membrane transport is controlled by small G proteins, which include members of the Rab and Arf families. Whereas the role of the classic Arf family members are well characterized, many of the Arf-like proteins (Arls) remain poorly defined. Here we show that Arl5a and Arl5b are localised to the trans-Golgi in mammalian cells, and furthermore have identified a role for Arl5b in the regulation of retrograde membrane transport from endosomes to the trans-Golgi network (TGN). The constitutively active Arl5b (Q70L)-GFP mutant was localised efficiently to the Golgi in HeLa cells whereas the dominant-negative Arl5b (T30N)-GFP mutant was dispersed throughout the cytoplasm and resulted in perturbation of the Golgi apparatus. Stable HeLa cells expressing GFP-tagged Arl5b (Q70L) showed an increased rate of endosome-to-Golgi transport of the membrane cargo TGN38 compared with control HeLa cells. Depletion of Arl5b by RNAi resulted in an alteration in the intracellular distribution of mannose-6-phosphate receptor, and significantly reduced the endosome-to-TGN transport of the membrane cargo TGN38 and of Shiga toxin, but had no affect on the anterograde transport of the cargo E-cadherin. Collectively these results suggest that Arl5b is a TGN-localised small G protein that plays a key role in regulating transport along the endosome-TGN pathway.
Read more from the original source:
Arl5b is a Golgi-localised small G protein involved in the regulation of retrograde transport.
By admin, on January 17th, 2012
J Biochem. 2012 Jan 13;
Tokuda N, Kawai K, Lee YH, Ikegami T, Yamaguchi S, Yagisawa H, Fukui Y, Tuzi S
Differences in the conformation of the pleckstrin homology (PH) domain of switch-associated protein-70 (SWAP-70) in solution and at the lipid bilayer membrane surface were examined using CD, fluorescence, and NMR spectroscopy. Intracellular relocalization of SWAP-70 from the cytoplasm to the plasma membrane and then to the nucleus is associated with its cellular functions. The PH domain of SWAP-70 contains a phosphoinositide-binding site and a nuclear localization signal (NLS) which localize SWAP-70 to the plasma membrane and nucleus, respectively. CD and fluorescence spectra showed that a significant conformational alteration involving formation of disordered structure occurs when the PH domain binds to D-myo-phosphatidylinositol 3,4,5-trisphosphate or D-myo-phosphatidylinositol 4,5-bisphosphate embedded in lipid bilayer vesicles. NMR spectra indicate that Ala and Trp residues located in the C-terminal α-helix of the PH domain undergo conformational alterations to form a disordered structure at the vesicle surface. These conformational alterations were not induced by association with inositol 1,3,4,5-tetrakisphosphate in solution or coexistence of phosphatidylcholine vesicles. Interaction with the plane of the lipid bilayer via association with the phosphoinositides is required for the unfolding of the C-terminal α-helix of the PH domain. The unwinding of the C-terminal α-helix could regulate the functions of SWAP-70 at the plasma membrane surface.
Originally posted here:
Membrane-induced alteration of the secondary structure in the SWAP-70 pleckstrin homology domain.
By admin, on January 15th, 2012
J Biol Chem. 2012 Jan 12;
Karst JC, Barker R, Devi U, Swann M, Davi M, Roser SJ, Ladant D, Chenal A
The adenylate cyclase toxin (CyaA), one of the virulence factors secreted by Bordetella pertussis, the pathogenic bacteria responsible for whooping cough, plays a critical role in the early stages of respiratory tract colonization by this bacterium. The CyaA toxin is able to invade eukaryotic cells by translocating its N-terminal catalytic domain directly across the plasma membrane of the target cells where, activated by endogenous calmodulin, it produces supraphysiological levels of cAMP. How the catalytic domain is transferred from the hydrophilic extracellular medium into the hydrophobic environment of the membrane and then to the cell cytoplasm, remains an unsolved question. In this report, we have characterized the membrane interacting properties of the CyaA catalytic domain. We showed that a protein covering the catalytic domain (AC384, encompassing residues 1-384 of CyaA) displayed no membrane association propensity. However, a longer polypeptide (AC489), encompassing residues 1 to 489 of CyaA, exhibited the intrinsic property to bind to membranes and to induce lipid bilayer destabilization. We further showed that deletion of residues 375 to 485 within CyaA totally abrogated the toxin ability to increase intracellular cAMP in target cells. These results indicate that, while the calmodulin dependent enzymatic domain is restricted to the amino terminal residues 1 to 384 of CyaA, the membrane-interacting, translocation-competent domain extents up to residue 489. This thus suggests an important role of the region adjacent to the catalytic domain of CyaA in promoting its interaction with and its translocation across the plasma membrane of target cells.
Visit link:
Identification of a region that assists membrane insertion and translocation of the catalytic domain of Bordetella pertussis CyaA toxin.
By admin, on January 15th, 2012
J Biol Chem. 2012 Jan 12;
Karst JC, Barker R, Devi U, Swann M, Davi M, Roser SJ, Ladant D, Chenal A
The adenylate cyclase toxin (CyaA), one of the virulence factors secreted by Bordetella pertussis, the pathogenic bacteria responsible for whooping cough, plays a critical role in the early stages of respiratory tract colonization by this bacterium. The CyaA toxin is able to invade eukaryotic cells by translocating its N-terminal catalytic domain directly across the plasma membrane of the target cells where, activated by endogenous calmodulin, it produces supraphysiological levels of cAMP. How the catalytic domain is transferred from the hydrophilic extracellular medium into the hydrophobic environment of the membrane and then to the cell cytoplasm, remains an unsolved question. In this report, we have characterized the membrane interacting properties of the CyaA catalytic domain. We showed that a protein covering the catalytic domain (AC384, encompassing residues 1-384 of CyaA) displayed no membrane association propensity. However, a longer polypeptide (AC489), encompassing residues 1 to 489 of CyaA, exhibited the intrinsic property to bind to membranes and to induce lipid bilayer destabilization. We further showed that deletion of residues 375 to 485 within CyaA totally abrogated the toxin ability to increase intracellular cAMP in target cells. These results indicate that, while the calmodulin dependent enzymatic domain is restricted to the amino terminal residues 1 to 384 of CyaA, the membrane-interacting, translocation-competent domain extents up to residue 489. This thus suggests an important role of the region adjacent to the catalytic domain of CyaA in promoting its interaction with and its translocation across the plasma membrane of target cells.
Read the original here:
Identification of a region that assists membrane insertion and translocation of the catalytic domain of Bordetella pertussis CyaA toxin.
By admin, on January 10th, 2012
By admin, on January 10th, 2012
Virus Res. 2011 Dec 31;
Fuchs W, Granzow H, Veits J, Mettenleiter TC
pUL11 is a highly conserved, small, acylated, membrane-associated tegument protein of herpesviruses. It is involved in final envelopment of nascent virions in the cytoplasm, although the precise mechanism is still unknown. By screening of mouse monoclonal antibodies (mAb) raised against purified particles of infectious laryngotracheitis virus (ILTV) of chickens (Veits et al., 2003a), we identified two mAb recognizing the 15kDa UL11 protein (pUL11) of this avian alphaherpesvirus. These mAb permitted detection and precise localization of pUL11 in mature ILT virions, as well as in the cytoplasm of infected chicken cells by Western blot analyses, indirect immunofluorescence tests, and immunoelectron microscopy. For investigation of gene function UL11-deleted ILTV recombinants were generated. Like its homologues in several other alphaherpesviruses, ILTV-pUL11 was shown to be nonessential for productive virus replication. However, compared to wild-type and UL11 rescued ILTV the deletion mutants exhibited significantly reduced virus yields and moderately impaired spread in cell culture. In the absence of pUL11, electron microscopy of infected cells revealed accumulations of tegument proteins with nucleocapsids, and marked distortions of Golgi membranes in the cytoplasm, which obviously inhibited the formation of mature, enveloped virus particles. Taken together, our results demonstrate that pUL11 is relevant for secondary envelopment of ILTV, and confirm functional conservation of this protein in herpesviruses. The now available unique pUL11-specific mAb will help to further analyze this function, which is presumably mediated by physical interactions with other viral gene products, in cultured cells and in the natural animal host of ILTV.
Go here to read the rest:
Identification and functional analysis of the small membrane-associated protein pUL11 of avian infectious laryngotracheitis virus.
By admin, on January 10th, 2012
Virus Res. 2011 Dec 31;
Fuchs W, Granzow H, Veits J, Mettenleiter TC
pUL11 is a highly conserved, small, acylated, membrane-associated tegument protein of herpesviruses. It is involved in final envelopment of nascent virions in the cytoplasm, although the precise mechanism is still unknown. By screening of mouse monoclonal antibodies (mAb) raised against purified particles of infectious laryngotracheitis virus (ILTV) of chickens (Veits et al., 2003a), we identified two mAb recognizing the 15kDa UL11 protein (pUL11) of this avian alphaherpesvirus. These mAb permitted detection and precise localization of pUL11 in mature ILT virions, as well as in the cytoplasm of infected chicken cells by Western blot analyses, indirect immunofluorescence tests, and immunoelectron microscopy. For investigation of gene function UL11-deleted ILTV recombinants were generated. Like its homologues in several other alphaherpesviruses, ILTV-pUL11 was shown to be nonessential for productive virus replication. However, compared to wild-type and UL11 rescued ILTV the deletion mutants exhibited significantly reduced virus yields and moderately impaired spread in cell culture. In the absence of pUL11, electron microscopy of infected cells revealed accumulations of tegument proteins with nucleocapsids, and marked distortions of Golgi membranes in the cytoplasm, which obviously inhibited the formation of mature, enveloped virus particles. Taken together, our results demonstrate that pUL11 is relevant for secondary envelopment of ILTV, and confirm functional conservation of this protein in herpesviruses. The now available unique pUL11-specific mAb will help to further analyze this function, which is presumably mediated by physical interactions with other viral gene products, in cultured cells and in the natural animal host of ILTV.
Visit link:
Identification and functional analysis of the small membrane-associated protein pUL11 of avian infectious laryngotracheitis virus.
|
