bluuebunny/crossref_metadata_2025 huggingface dataset:
Ganglioside glycosyltransferases and newly synthesized gangliosides are excluded from detergent-insoluble complexes of Golgi membranes
Authors: CRESPO Pilar M. , ZURITA Adolfo R. , GIRAUDO Claudio G. , MACCIONI Hugo J. F. , DANIOTTI Jose L.
Published: November 2007

GEM (glycosphingolipid-enriched microdomains) are specialized detergent-resistant domains of the plasma membrane in which some gangliosides concentrate. Although genesis of GEM is considered to occur in the Golgi complex, where the synthesis of gangliosides also occurs, the issue concerning the incorporation of ganglioside species into GEM is still poorly understood. In this work, using Chinese hamster ovary K1 cell clones with different glycolipid compositions, we compared the behaviour with cold Triton X-100 solubilization of plasma membrane ganglioside species with the same species newly synthesized in Golgi membranes. We also investigated whether three ganglioside glycosyltransferases (a sialyl-, a N-acetylgalactosaminyl- and a galactosyl-transferase) are included or excluded from GEM in Golgi membranes. Our data show that an important fraction of plasma membrane GM3, and most GD3 and GT3, reside in GEM. Immunocytochemical examination of GD3-expressing cells showed GD3 to be distributed as cold-detergent-resistant patches in the plasma membrane. These patches did not co-localize with a glycosylphosphatidylinositol-anchored protein used as GEM marker, indicating a heterogeneous composition of plasma membrane GEM. In Golgi membranes we were unable to find evidence for GEM localization of either ganglioside glycosyltransferases or newly synthesized gangliosides. Since the same ganglioside species appear in plasma membrane GEM, it was concluded that in vivo nascent GD3, GT3 and GM3 segregate from their synthesizing transferases and then enter GEM. This latter event could have taken place shortly after synthesis in the Golgi cisternae, along the secretory pathway and/or at the cell surface.
Catalytic- and ecto-domains of membrane type 1-matrix metalloproteinase have similar inhibition profiles but distinct endopeptidase activities
Authors: HURST Douglas R. , SCHWARTZ Martin A. , GHAFFARI Mohammad A. , JIN Yonghao , TSCHESCHE Harald , FIELDS Gregg B. , SANG Qing-Xiang Amy
Published: November 2007

Membrane type 1-matrix metalloproteinase (MT1-MMP/MMP-14) is a major collagenolytic enzyme that plays a vital role in development and morphogenesis. To elucidate further the structure–function relationship between the human MT1-MMP active site and the influence of the haemopexin domain on catalysis, substrate specificity and inhibition kinetics of the cdMT1-MMP (catalytic domain of MT1-MMP) and the ecto domain ΔTM-MT1-MMP (transmembrane-domain-deleted MT1-MMP) were compared. For substrate 1 [Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2, where Mca stands for (7-methoxycoumarin-4-yl)acetyl- and Dpa for N-3-(2,4-dinitrophenyl)-l-2,3-diaminopropionyl], the activation energy Ea was determined to be 11.2 and 12.2 kcal/mol (1 cal=4.184 J) for cdMT1-MMP and ΔTM-MT1-MMP respectively, which is consistent with kcat/KM values of 7.37 and 1.46×104 M−1·s−1. The kcat/KM values for a series of similar single-stranded peptide substrates were determined and found to correlate with a slope of 0.17 for the two enzyme forms. A triple-helical peptide substrate was predicted to have a kcat/KM of 0.87×104 M−1·s−1 for ΔTM-MT1-MMP based on the value for cdMT1-MMP of 5.12×104 M−1·s−1; however, the actual value was determined to be 2.5-fold higher, i.e. 2.18×104 M−1·s−1. These results suggest that cdMT1-MMP is catalytically more efficient towards small peptide substrates than ΔTM-MT1-MMP and the haemopexin domain of MT1-MMP facilitates the hydrolysis of triple-helical substrates. Diastereomeric inhibitor pairs were utilized to probe further binding similarities at the active site. Ratios of Ki values for the inhibitor pairs were found to correlate between the enzyme forms with a slope of 1.03, suggesting that the haemopexin domain does not significantly modify the enzyme active-site structure.
WBP-2, a WW domain binding protein, interacts with the thyroid-specific transcription factor Pax8
Authors: NITSCH Roberto , DI PALMA Tina , MASCIA Anna , ZANNINI Mariastella
Published: November 2007

The Pax gene family encodes transcription factors that are essential in organogenesis and in the differentiation of various organs in higher eukaryotes. Pax proteins have a DNA binding domain at the N-terminus, and a transcriptional activation domain at the C-terminus. How these domains interact with the transcriptional machinery of the cell is still unclear. In the present paper, we describe the identification by means of immunological screening of the WW domain binding protein WBP-2 as a biochemical interactor of Pax8 (a WW domain is a protein-interaction domain containing two conserved tryptophan residues). Pax8 is required for the morphogenesis of the thyroid gland and for the maintenance of the thyroid differentiated cellular phenotype. WBP-2 was identified originally as a WW domain binding protein, and its function is still unknown. WBP-2 binds to Pax8 in vitro in pulldown assays, and in vivo in tissue culture cells in co-immunoprecipitation assays. Interestingly, Pax8 does not contain a WW domain. Our results point to the identification of a new protein-interacting domain that is present in the C-terminal portion of Pax8 and that is required for protein–protein interaction with WBP-2. Our results demonstrate that WBP-2 is not a transcriptional co-activator of Pax8, but rather behaves as an adaptor molecule, as suggested in other studies.
Peroxide-mediated chromatin remodelling of a nuclear factor kappaB site in the mouse inducible nitric oxide synthase promoter
Authors: WEI Junping , GUO Hongtao , GAO Chengjiang , KUO Paul C.
Published: November 2007

Hepatocyte expression of iNOS (inducible nitric oxide synthase) and synthesis of nitric oxide convey protective antioxidant functions in models of sepsis, shock and reperfusion. However, the underlying redox-sensitive mechanisms that regulate hepatocyte expression of iNOS and its antioxidant functions are largely unknown. Activity of the transcription factor NF-κB (nuclear factor κB) is known to be redox-modulated. In this regard, the mouse hepatocyte iNOS promoter has NF-κB-binding sites at nt −1044 to −1034 and at nt −114 to −104, which are considered to be critical for iNOS expression in response to pro-inflammatory cytokine stimulation. The relative contribution of these two NF-κB-binding sites in the mouse iNOS promoter to hepatocyte iNOS promoter activity in the context of oxidative stress has not been characterized previously. In addition, although the cis- and trans-regulatory factors controlling mouse hepatocyte iNOS expression have been well-characterized, the local changes in chromatin structure that accompany activation of iNOS gene transcription have not been considered. In the present study, we demonstrate that (1) in the absence of exogenous oxidative stress, the NF-κB site at nt −114 is inactive and (2) peroxide-mediated oxidative stress induces hyperacetylation and enhanced accessibility of the restriction enzyme to this NF-κB region. Our results suggest that chromatin structural changes activate this NF-κB site and increase interleukin-1β-stimulated iNOS expression in the presence of oxidative stress.
Decreased expression levels of rat liver glutathione S-transferase A2 and albumin during the acute phase response are mediated by HNF1 (hepatic nuclear factor 1) and IL6DEX-NP
Authors: WHALEN Richard , VOSS Susan H. , BOYER Thomas D.
Published: November 2007

The acute phase response is characterized by positive and negative regulation of many liver proteins including GSTs (glutathione S-transferases) and albumin. The expression of albumin and some GSTs are dependent on HNF1 (hepatic nuclear factor 1). Interleukin 6 plus dexamethasone induce a nuclear protein (IL6DEX-NP) in rat hepatocytes in vitro that binds to a promoter element adjacent to the HNF1 site of rGSTA2 and decreases its expression. We determined how HNF1 and IL6DEX-NP regulate rGSTA2 and albumin expression in rats during the acute phase response after LPS (lipopolysaccharide) treatment. Expression of rGSTA2 and albumin mRNA decreased 3 h after LPS treatment and remained low for 48 h. Transcription rates showed a similar pattern but albumin transcription was less affected. HNF1 and IL6DEX-NP binding to the rGSTA2 promoter was present in control livers but was absent at 3 and 6 h after LPS. By 12 h, HNF1 and IL6DEX-NP binding to the rGSTA2 promoter reappeared and increased to above normal at 48 h. The patterns of HNF1 and IL6DEX-NP binding to the albumin promoter were similar. Affinity of IL6DEX-NP for the albumin promoter was less than that for the rGSTA2 promoter and changes in the transcription rates were consistent with the difference. Early decreases in rGSTA2 and albumin during the acute phase response are due to decreased binding of HNF1. Later persistent decreases in transcriptional rate of rGSTA2 and to a lesser extent albumin are due to increased IL6DEX-NP binding. IL6DEX-NP appears to be an important negative regulator of gene expression in vitro and in vivo.
Structure and function of human Vps20 and Snf7 proteins
Authors: PECK Jeremy W. , BOWDEN Emma T. , BURBELO Peter D.
Published: November 2007

Snf7p (sucrose non-fermenting) and Vps20p (vacuolar protein-sorting) are small coil-coiled proteins involved in yeast MVB (multivesicular body) structure, formation and function. In the present study, we report the identification of three human homologues of yeast Snf7p, designated hSnf7-1, hSnf7-2 and hSnf7-3, and a single human Vps20p homologue, designated hVps20, that may have similar roles in humans. Immunofluorescence studies showed that hSnf7-1 and hSnf7-3 localized in large vesicular structures that also co-localized with late endosomal/lysosomal structures induced by overexpressing an ATPase-defective Vps4-A mutant. In contrast, overexpressed hVps20 showed a typical endosomal membrane-staining pattern, and co-expression of hVps20 with Snf7-1 dispersed the large Snf7-staining vesicles. Interestingly, overexpression of both hSnf7 and hVps20 proteins induced a post-endosomal defect in cholesterol sorting. To explore possible protein–protein interactions involving hSnf7 proteins, we used information from yeast genomic studies showing that yeast Snf7p can interact with proteins involved in MVB function. Using a glutathione S-transferase-capture approach with several mammalian homologues of such yeast Snf7p-interacting proteins, we found that all three hSnf7s interacted with mouse AIP1 [ALG-2 (apoptosis-linked gene 2) interacting protein 1], a mammalian Bro1p [BCK1 (bypass of C kinase)-like resistance to osmotic shock]-containing protein involved in cellular vacuolization and apoptosis. Whereas mapping experiments showed that the N-terminus of AIP1 containing both a Bro1 and an α-helical domain were required for interaction with hSnf7-1, Snf7-1 did not interact with another human Bro1-containing molecule, rhophilin-2. Co-immunoprecipitation experiments confirmed the in vivo interaction of hSnf7-1 and AIP1. Additional immunofluorescence experiments showed that hSnf7-1 recruited cytosolic AIP1 to the Snf7-induced vacuolar-like structures. Together these results suggest that mammalian Vps20, AIP1 and Snf7 proteins, like their yeast counterparts, play roles in MVB function.
Detection of novel intracellular agonist responsive pools of phosphatidylinositol 3,4-bisphosphate using the TAPP1 pleckstrin homology domain in immunoelectron microscopy
Authors: WATT Stephen A. , KIMBER Wendy A. , FLEMING Ian N. , LESLIE Nick R. , DOWNES C. Peter , LUCOCQ John M.
Published: November 2007

PtdIns(3,4)P2, a breakdown product of the lipid second messenger PtdIns(3,4,5)P3, is a key signalling molecule in pathways controlling various cellular events. Cellular levels of PtdIns(3,4)P2 are elevated upon agonist stimulation, mediating downstream signalling pathways by recruiting proteins containing specialized lipid-binding modules, such as the pleckstrin homology (PH) domain. A recently identified protein, TAPP1 (tandem-PH-domain-containing protein 1), has been shown to interact in vitro with high affinity and specificity with PtdIns(3,4)P2 through its C-terminal PH domain. In the present study, we have utilized this PH domain tagged with glutathione S-transferase (GST–TAPP1-PH) as a probe in an on-section immunoelectron microscopy labelling procedure, mapping the subcellular distribution of PtdIns(3,4)P2. As expected, we found accumulation of PtdIns(3,4)P2 at the plasma membrane in response to the agonists platelet-derived growth factor and hydrogen peroxide. Importantly, however, we also found agonist stimulated PtdIns(3,4)P2 labelling of intracellular organelles, including the endoplasmic reticulum and multivesicular endosomes. Expression of the 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10) in PTEN-null U87MG cells revealed differential sensitivity of these lipid pools to the enzyme. These data suggest a role for PtdIns(3,4)P2 in endomembrane function.
Structural and functional dissection of a conserved destabilizing element of cyclo-oxygenase-2 mRNA: evidence against the involvement of AUF-1 [AU-rich element/poly(U)-binding/degradation factor-1], AUF-2, tristetraprolin, HuR (Hu antigen R) or FBP1 (far-upstream-sequence-element-binding protein 1)
Authors: SULLY Gareth , DEAN Jonathan L. E. , WAIT Robin , RAWLINSON Lesley , SANTALUCIA Tomas , SAKLATVALA Jeremy , CLARK Andrew R.
Published: November 2007

COX-2 (cyclo-oxygenase-2) mRNA is degraded rapidly in resting cells, but is stabilized by the mitogen-activated protein kinase p38 signalling pathway in response to pro-inflammatory stimuli. A conserved ARE (AU-rich element) of the COX-2 3´ untranslated region, CR1 (conserved region 1), acts as a potent instability determinant, and mediates stabilization in response to p38 activation. A detailed structural and functional analysis of this element was performed in an attempt to identify RNA-binding proteins involved in the regulation of COX-2 mRNA stability. Destabilization of a β-globin reporter mRNA was dependent upon two distinct AREs within CR1, each containing three copies of the sequence AUUUA. CR1 was shown to bind AUF-1 [ARE/poly(U)-binding/degradation factor-1] and/or AUF-2, HuR (Hu antigen R), TTP (tristetraprolin) and FBP1 (far-upstream-sequence-element-binding protein 1), yet these factors did not appear to account for the effects of CR1 upon mRNA stability. Mutant sequences were identified that were incapable of destabilizing a reporter mRNA, yet showed unimpaired binding of FBP1 and AUF-1 and/or -2. TTP was absent from the HeLa cell line used in this analysis. Finally, RNA interference experiments argued against a prominent role for HuR in the CR1-mediated regulation of mRNA stability. We conclude that at least one critical regulator of COX-2 mRNA stability is likely to remain unidentified at present.
Oxygenation by COX-2 (cyclo-oxygenase-2) of 3-HETE (3-hydroxyeicosatetraenoic acid), a fungal mimetic of arachidonic acid, produces a cascade of novel bioactive 3-hydroxyeicosanoids
Authors: Ciccoli Roberto , Sahi Shakti , Singh Sandhya , Prakash Hridayesh , Zafiriou Maria-Patapia , Ishdorj Ganchimeg , Kock Johan L. F. , Nigam Santosh
Published: November 2007

Cyclo-oxygenases-1/2 (COX-1/2) catalyse the oxygenation of AA (arachidonic acid) and related polyunsaturated fatty acids to endoperoxide precursors of prostanoids. COX-1 is referred to as a constitutive enzyme involved in haemostasis, whereas COX-2 is an inducible enzyme expressed in inflammatory diseases and cancer. The fungus Dipodascopsis uninucleata has been shown by us to convert exogenous AA into 3(R)-HETE [3(R)-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid]. 3R-HETE is stereochemically identical with AA, except that a hydroxy group is attached at its C-3 position. Molecular modelling studies with 3-HETE and COX-1/2 revealed a similar enzyme–substrate structure as reported for AA and COX-1/2. Here, we report that 3-HETE is an appropriate substrate for COX-1 and -2, albeit with a lower activity of oxygenation than AA. Oxygenation of 3-HETE by COX-2 produced a novel cascade of 3-hydroxyeicosanoids, as identified with EI (electron impact)–GC–MS, LC–MS–ES (electrospray) and LC–MS–API (atmospheric pressure ionization) methods. Evidence for in vitro production of 3-hydroxy-PGE2 (3-hydroxy-prostaglandin E2) was obtained upon infection of HeLa cells with Candida albicans at an MOI (multiplicity of infection) of 100. Analogous to interaction of AA and aspirin-treated COX-2, 3-HETE was transformed by acetylated COX-2 to 3,15-di-HETE (3,15-dihydroxy-HETE), whereby C-15 showed the (R)-stereochemistry. 3-Hydroxy-PGs are potent biologically active compounds. Thus 3-hydroxy-PGE2 induced interleukin-6 gene expression via the EP3 receptor (PGE2 receptor 3) in A549 cells, and raised cAMP levels via the EP4 receptor in Jurkat cells. Moreover, 3R,15S-di-HETE triggered the opening of the K+ channel in HTM (human trabecular meshwork) cells, as measured by the patch–clamp technique. Since many fatty acid disorders are associated with an ‘escape’ of 3-hydroxy fatty acids from the β-oxidation cycle, the production of 3-hydroxyeicosanoids may be critical in modulation of effects of endogenously produced eicosanoids.
PKCδ mediates up-regulation of NOX1, a catalytic subunit of NADPH oxidase, via transactivation of the EGF receptor: possible involvement of PKCδ in vascular hypertrophy
Authors: Fan Chun Yuan , Katsuyama Masato , Yabe-Nishimura Chihiro
Published: November 2007

NADPH oxidase is the major source of superoxide production in cardiovascular tissues. We reported previously that PG (prostaglandin) F2α caused hypertrophy of vascular smooth muscle cells by induction of NOX1, a catalytic subunit of NADPH oxidase. PGF2α-induced NOX1 expression was mediated by transactivation of the EGF (epidermal growth factor) receptor and subsequent activation of ERK (extracellular-signal-regulated kinase) 1/2, PI3K (phosphoinositide 3-kinase) and ATF-1 (activating transcription factor-1), a member of the CREB (cAMP-response-element-binding protein)/ATF family. As the receptor for PGF2α is known to activate PKC (protein kinase C), involvement of PKC in up-regulation of NOX1 expression was investigated in A7r5 cells. GF109203x, a non-selective inhibitor of PKC, dose-dependently suppressed the induction of NOX1 mRNA by PGF2α. Whereas an inhibitor of the conventional PKC, Gö 6976, and a PKCϵ translocation-inhibitor peptide had no effect, an inhibitor of PKCδ, rottlerin, significantly attenuated the PGF2α-induced increase in NOX1 mRNA. Gene silencing of PKCδ by RNA interference significantly suppressed the PGF2α-induced increase in NOX1 mRNA, as well as phosphorylation of the EGF receptor, ERK1/2 and ATF-1. Silencing of the PKCδ gene also attenuated the PDGF (platelet-derived growth factor)- induced increase in NOX1 mRNA and transactivation of the EGF receptor. Moreover, the augmented synthesis of the protein induced by PGF2α or PDGF was abolished by gene silencing of PKCδ. These results suggest that PKCδ-mediated transactivation of the EGF receptor is elicited not only by PGF2α, but also by PDGF, and that the subsequent activation of ERK1/2 and ATF-1 leads to up-regulation of NOX1 gene expression and ensuing hypertrophy in the vascular cell lineage.
Phosphorylation of PEA-15 switches its binding specificity from ERK/MAPK to FADD
Authors: Renganathan Hemamalini , Vaidyanathan Hema , Knapinska Anna , Ramos Joe W.
Published: November 2007

Cell signalling pathways that regulate proliferation and those that regulate programmed cell death (apoptosis) are co-ordinated. The proteins and mechanisms that mediate the integration of these pathways are not yet fully described. The phosphoprotein PEA-15 (phosphoprotein enriched in astrocytes) can regulate both the ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) pathway and the death receptor-initiated apoptosis pathway. This is the result of PEA-15 binding to the ERK/MAPK or the proapoptotic protein FADD (Fas-activated death domain protein) respectively. The mechanism by which binding of PEA-15 to these proteins is controlled has not been elucidated. PEA-15 is a phosphoprotein containing a Ser-104 phosphorylated by protein kinase C and a Ser-116 phosphorylated by CamKII (calcium/calmodulin-dependent protein kinase II) or AKT. Phosphorylation of Ser-104 is implicated in the regulation of glucose metabolism, while phosphorylation at Ser-116 is required for PEA-15 recruitment to the DISC (death-initiation signalling complex). Moreover, PEA-15 must be phosphorylated at Ser-116 to inhibit apoptosis. In the present study, we report that phosphorylation at Ser-104 blocks ERK binding to PEA-15 in vitro and in vivo, whereas phosphorylation at Ser-116 promotes its binding to FADD. We further characterize phospho-epitope-binding antibodies to these sites. We report that phosphorylation does not influence the distribution of PEA-15 between the cytoplasm and nucleus of the cell since all phosphorylated states are found predominantly in the cytoplasm. We propose that phosphorylation of PEA-15 acts as the switch that controls whether PEA-15 influences proliferation or apoptosis.
Specificity and versatility of SH3 and other proline-recognition domains: structural basis and implications for cellular signal transduction
Authors: Li Shawn S.-C.
Published: November 2007

Protein–protein interactions occurring via the recognition of short peptide sequences by modular interaction domains play a central role in the assembly of signalling protein complexes and larger protein networks that regulate cellular behaviour. In addition to spatial and temporal factors, the specificity of signal transduction is intimately associated with the specificity of many co-operative, pairwise binding events upon which various pathways are built. Although protein interaction domains are usually identified via the recognition code, the consensus sequence motif, to which they selectively bind, they are highly versatile and play diverse roles in the cell. For example, a given interaction domain can bind to multiple sequences that exhibit no apparent identity, and, on the other hand, domains of the same class or different classes may favour a given consensus motif. This promiscuity in ligand selection is typified by the SH3 (Src homology 3) domain and several other interaction modules that commonly recognize proline-rich sequences. Furthermore, interaction domains are highly adaptable, a property that is essential for the evolution of novel pathways and modulation of signalling dynamics. The ability of certain interaction domains to perform multiple tasks, however, poses a challenge for the cell to control signalling specificity when cross-talk between pathways is undesired. Extensive structural and biochemical analysis of many interaction domains in recent years has started to shed light on the molecular basis underlying specific compared with diverse binding events that are mediated by interaction domains and the role affinity plays in affecting domain specificity and regulating cellular signal transduction.
Connective tissue growth factor (CTGF) promotes activated mesangial cell survival via up-regulation of mitogen-activated protein kinase phosphatase-1 (MKP-1)
Authors: Wahab Nadia , Cox Dimity , Witherden Abigail , Mason Roger M.
Published: November 2007

Activated mesangial cells are thought to play a pivotal role in the development of kidney fibrosis under chronic pathological conditions, including DN (diabetic nephropathy). Their prolonged survival may enhance the development of the disease since they express increased amounts of growth factors and extracellular matrix proteins. CTGF (connective tissue growth factor) is one of the growth factors produced by activated mesangial cells and is reported to play a key role in the pathogenesis of DN. Previous studies have shown that addition of exogenous CTGF to HMCs (human mesangial cells) rapidly activates ERK1/2 (extracellular-signal-regulated kinase 1/2) MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase) MAPK, but not the p38 MAPK, despite the activation of the upstream kinases, MKK3/6 (MAPK kinase 3/6). The aim of the present study was to investigate whether the lack of phosphorylated p38 MAPK by CTGF has an anti-apoptotic effect on activated HMCs. We show that in HMC CTGF induces the rapid transcriptional activation and synthesis of MKP-1 (MAPK phosphatase-1), a dual specificity phosphatase that dephosphorylates p38 MAPK. This in turn prevents the anti-apoptotic protein, Bcl-2, from being phosphorylated and losing its function, leading to the survival of the cells. Knockout of MKP-1 protein in mesangial cells treated with CTGF, using siRNA (small interfering RNA) or antisense oligonucleotides, allows p38 MAPK activation and induces mesangial cell death.
CgNa, a type I toxin from the giant Caribbean sea anemoneCondylactis giganteashows structural similarities to both type I and II toxins, as well as distinctive structural and functional properties
Authors: Salceda Emilio , Pérez-Castells Javier , López-Méndez Blanca , Garateix Anoland , Salazar Hector , López Omar , Aneiros Abel , Ständker Ludger , Béress Lászlo , Forssmann Wolf-Georg , Soto Enrique , Jiménez-Barbero Jesús , Giménez-Gallego Guillermo
Published: November 2007

CgNa (Condylactis gigantea neurotoxin) is a 47-amino-acid- residue toxin from the giant Caribbean sea anemone Condylactis gigantea. The structure of CgNa, which was solved by 1H-NMR spectroscopy, is somewhat atypical and displays significant homology with both type I and II anemone toxins. CgNa also displays a considerable number of exceptions to the canonical structural elements that are thought to be essential for the activity of this group of toxins. Furthermore, unique residues in CgNa define a characteristic structure with strong negatively charged surface patches. These patches disrupt a surface-exposed cluster of hydrophobic residues present in all anemone-derived toxins described to date. A thorough characterization by patch–clamp analysis using rat DRG (dorsal root ganglion) neurons indicated that CgNa preferentially binds to TTX-S (tetrodotoxin-sensitive) voltage-gated sodium channels in the resting state. This association increased the inactivation time constant and the rate of recovery from inactivation, inducing a significant shift in the steady state of inactivation curve to the left. The specific structural features of CgNa may explain its weaker inhibitory capacity when compared with the other type I and II anemone toxins.
Succinate modulation of H2O2 release at NADH:ubiquinone oxidoreductase (Complex I) in brain mitochondria
Authors: Zoccarato Franco , Cavallini Lucia , Bortolami Silvia , Alexandre Adolfo
Published: November 2007

Complex I (NADH:ubiquinone oxidoreductase) is responsible for most of the mitochondrial H2O2 release, both during the oxidation of NAD-linked substrates and during succinate oxidation. The much faster succinate-dependent H2O2 production is ascribed to Complex I, being rotenone-sensitive. In the present paper, we report high-affinity succinate-supported H2O2 generation in the absence as well as in the presence of GM (glutamate/malate) (1 or 2 mM of each). In brain mitochondria, their only effect was to increase from 0.35 to 0.5 or to 0.65 mM the succinate concentration evoking the semi-maximal H2O2 release. GM are still oxidized in the presence of succinate, as indicated by the oxygen-consumption rates, which are intermediate between those of GM and of succinate alone when all substrates are present together. This effect is removed by rotenone, showing that it is not due to inhibition of succinate influx. Moreover, α-oxoglutarate production from GM, a measure of the activity of Complex I, is decreased, but not stopped, by succinate. It is concluded that succinate-induced H2O2 production occurs under conditions of regular downward electron flow in Complex I. Succinate concentration appears to modulate the rate of H2O2 release, probably by controlling the hydroquinone/quinone ratio.
Molecular analysis of the sea anemone toxin Av3 reveals selectivity to insects and demonstrates the heterogeneity of receptor site-3 on voltage-gated Na+ channels
Authors: Moran Yehu , Kahn Roy , Cohen Lior , Gur Maya , Karbat Izhar , Gordon Dalia , Gurevitz Michael
Published: November 2007

Av3 is a short peptide toxin from the sea anemone Anemonia viridis shown to be active on crustaceans and inactive on mammals. It inhibits inactivation of Navs (voltage-gated Na+ channels) like the structurally dissimilar scorpion α-toxins and type I sea anemone toxins that bind to receptor site-3. To examine the potency and mode of interaction of Av3 with insect Navs, we established a system for its expression, mutagenized it throughout, and analysed it in toxicity, binding and electrophysiological assays. The recombinant Av3 was found to be highly toxic to blowfly larvae (ED50=2.65±0.46 pmol/100 mg), to compete well with the site-3 toxin LqhαIT (from the scorpion Leiurus quinquestriatus) on binding to cockroach neuronal membranes (Ki=21.4±7.1 nM), and to inhibit the inactivation of Drosophila melanogaster channel, DmNav1, but not that of mammalian Navs expressed in Xenopus oocytes. Moreover, like other site-3 toxins, the activity of Av3 was synergically enhanced by ligands of receptor site-4 (e.g. scorpion β-toxins). The bioactive surface of Av3 was found to consist mainly of aromatic residues and did not resemble any of the bioactive surfaces of other site-3 toxins. These analyses have portrayed a toxin that might interact with receptor site-3 in a different fashion compared with other ligands of this site. This assumption was corroborated by a D1701R mutation in DmNav1, which has been shown to abolish the activity of all other site-3 ligands, except Av3. All in all, the present study provides further evidence for the heterogeneity of receptor site-3, and raises Av3 as a unique model for design of selective anti-insect compounds.
Phospholipase C β3 is a key component in the Gβγ/PKCη/PKD-mediated regulation of trans-Golgi network to plasma membrane transport
Authors: Díaz Añel Alberto M.
Published: November 2007

The requirement of DAG (diacylglycerol) to recruit PKD (protein kinase D) to the TGN (trans-Golgi network) for the targeting of transport carriers to the cell surface, has led us to a search for new components involved in this regulatory pathway. Previous findings reveal that the heterotrimeric Gβγ (GTP-binding protein βγ subunits) act as PKD activators, leading to fission of transport vesicles at the TGN. We have recently shown that PKCη (protein kinase Cη) functions as an intermediate member in the vesicle generating pathway. DAG is capable of activating this kinase at the TGN, and at the same time is able to recruit PKD to this organelle in order to interact with PKCη, allowing phosphorylation of PKD's activation loop. The most qualified candidates for the production of DAG at the TGN are PI-PLCs (phosphatidylinositol-specific phospholipases C), since some members of this family can be directly activated by Gβγ, utilizing PtdIns(4,5)P2 as a substrate, to produce the second messengers DAG and InsP3. In the present study we show that βγ-dependent Golgi fragmentation, PKD1 activation and TGN to plasma membrane transport were affected by a specific PI-PLC inhibitor, U73122 [1-(6-{[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione]. In addition, a recently described PI-PLC activator, m-3M3FBS [2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl)benzenesulfonamide], induced vesiculation of the Golgi apparatus as well as PKD1 phosphorylation at its activation loop. Finally, using siRNA (small interfering RNA) to block several PI-PLCs, we were able to identify PLCβ3 as the sole member of this family involved in the regulation of the formation of transport carriers at the TGN. In conclusion, we demonstrate that fission of transport carriers at the TGN is dependent on PI-PLCs, specifically PLCβ3, which is necessary to activate PKCη and PKD in that Golgi compartment, via DAG production.
Contribution of prostanoids to endothelium-dependent vasodilatation in the digital circulation of women with primary Raynaud's disease
Authors: EASTER Melanie J. , MARSHALL Janice M.
Published: November 2007

In 15 women with PR (primary Raynaud's) disease and in 15 matched control women, ACh (acetylcholine) was delivered by iontophoresis to the dorsum of the finger (seven 20 s pulses of 0.1 mA, followed by one 20 s pulse of 0.2 mA, applied at 60 s intervals). Cutaneous RCF (red cell flux) was recorded from the same site by the laser Doppler technique. ACh evoked progressive increases in RCF that were comparable in pre- and post-menopausal women with PR [maxima of 294±113 and 259±59 pu (perfusion units) respectively, n=7 and 8 respectively], and in pre-menopausal controls (225±92 pu, n=7), but smaller in post-menopausal controls (140±63 pu, n=8; P<0.05). Aspirin (600 mg, orally), a COX (cyclo-oxygenase) inhibitor, potentiated the ACh-evoked dilator responses in pre- and post-menopausal women with PR (343±129 and 311±48 pu respectively) and post-menopausal controls (277±124 pu; P<0.05), but had no effect in pre-menopausal controls (225±92 pu). These results suggest that vasoconstrictor COX products limit ACh-evoked endothelium-dependent cutaneous dilatation in the digits in pre- and post-menopausal women with PR and in post-menopausal, but not pre-menopausal, control women. We propose that PR disease is associated with abnormality in the ability of oestrogen to modulate the synthesis of endothelium-dependent vasodilator and/or vasoconstrictor COX products.
Prognostic potential of brain natriuretic peptide (BNP) in predialysis chronic kidney disease patients
Authors: CARR Susan J. , BAVANANDAN Sunita , FENTUM Barbara , NG Leong
Published: November 2007

In the present study, we investigated the potential of N-BNP (N-terminal B-type natriuretic peptide) as a prognostic marker for risk of CV (cardiovascular) events, overall mortality and progression to ESRD (end-stage renal disease) in a cohort of 83 pre-dialysis CKD (chronic kidney disease) patients without clinical evidence of heart failure. During the study, ten patients reached the combined end point of overall mortality and/or CV event. Univariate factors associated with the combined end point were plasma N-BNP (P<0.0005), creatinine (P<0.002), systolic blood pressure (P<0.009) and age (P<0.015). N-BNP levels were higher in patients with CV events (P<0.0005). Cox model regression analysis yielded log10 N-BNP (hazard ratio, 9.608; P<0.007) and pre-existing CV disease (hazard ratio, 4.571; P<0.029) as independent predictors of overall mortality or CV events. Kaplan–Meier analysis curves for the subgroup with supramedian creatinine levels (225 μmol/l) showed significant separation of the curves stratified for plasma N-BNP levels above and below the group median (291 pmol/l) for all end points. Receiver-operator-characteristic curves for N-BNP (355 pmol/l cut-off) demonstrated a specificity of 65.8% at a sensitivity of 100% for predicting CV events/overall mortality. The measurement of plasma N-BNP may aid in the risk stratification of pre-dialysis CKD patients. The high sensitivity and negative predictive value (100%) may enable the selection of patients who could safely be excluded from further investigations, resulting in better focusing of resources.
Opposite changes in carotid versus aortic stiffness during healthy human pregnancy
Authors: MERSICH Beatrix , RIGÓ János , BESENYEI Csilla , LÉNÁRD Zsuzsanna , STUDINGER Péter , KOLLAI Márk
Published: November 2007

Systemic arterial compliance has been known to increase during healthy pregnancy, whereas, recently, the carotid artery has been reported to stiffen. To clarify this controversy, we simultaneously measured aortic PWV (pulse wave velocity) and carotid artery elastic parameters in a cohort of pregnant women. Twelve normotensive pregnant women were studied longitudinally during the three trimesters of pregnancy (T1, T2 and T3 respectively) and 12 weeks PP (postpartum). Carotid artery diastolic diameter and pulsatile distension was measured by an echo-wall tracking method and carotid pulse pressure by applanation tonometry. Carotid strain, compliance, distensibility coefficient, stiffness index β, Einc (incremental elastic modulus) and augmentation index were calculated. Aortic PWV was determined to estimate aortic distensibility. All carotid artery elastic parameters indicated significant stiffening from T1 to T3 (1.8±0.2 versus 2.9±0.3 mmHg for Einc), which was reversed after delivery (2.3±0.2 mmHg). Aortic PWV decreased during pregnancy (6.2±0.2 versus 5.4±0.2 m/s) and increased in the PP period (6.7±0.2 m/s). No correlation was found between changes in carotid artery elastic parameters and changes in aortic PWV either from T1 to T3 or from T3 to PP. The carotid artery exhibits regionally specific stiffening during pregnancy, which appears to represent a qualitatively different change in arterial elastic behaviour.
Biodistribution, plasma kinetics and quantification of single-pass pulmonary clearance of adrenomedullin
Authors: DUPUIS Jocelyn , CARON Alexandre , RUËL Nathalie
Published: November 2007

The biodistribution, pharmacokinetics and multi-organ clearance of the vasodilator peptide AM (adrenomedullin) were evaluated in rats and its single-pass pulmonary clearance was measured in dogs by the indicator-dilution technique. Intravenously administered 125I-rAM(1–50) [rat AM(1–50)] was rapidly cleared following a two-compartment model with a very rapid distribution half-life of 2.0 min [95% CI (confidence interval), 1.98–2.01] and an elimination half-life of 15.9 min (95% CI, 15.0–16.9). The lungs retained most of the injected activity with evidence of single-pass clearance, since retention was lower after intra-arterial (13.5±0.6%) compared with intravenous (30.4±1.5%; P<0.001) injection. Lung tissue levels of total endogenous AM were 20-fold higher than in other organs with no difference in plasma levels across the pulmonary circulation. In dogs, there was 36.4±2.1% first-pass unidirectional extraction of 125I-rAM(1–50) by the lungs that was reduced to 21.9±2.4% after the administration of unlabelled rAM(1–50) (P<0.01). Extraction was not affected by calcitonin-gene-related peptide administration (40.6±2.9%), but was slightly reduced by the C-terminal fragment of human AM(22–52) (31.4±3.3%; P<0.01). These data demonstrate that the lungs are a primary site for AM clearance in vivo with approx. 36% first-pass extraction through specific receptors. This suggests that the lungs not only modulate circulating levels of this peptide, but also represent its primary target.
Different contribution of interleukin-6 and cortisol activity to total plasma fibrin concentration and to acute mental stress-induced fibrin formation
Authors: von KÄNEL Roland , KUDIELKA Brigitte M. , HANEBUTH Dirk , PRECKEL Daniel , FISCHER Joachim E.
Published: November 2007

Acute mental stress may contribute to atherosclerosis by affecting inflammation and coagulation; however, the crosstalk between inflammation and coagulation during stress has not been studied. In the present study, we investigated the association of plasma fibrinogen, plasma IL-6 (interleukin-6) and free salivary cortisol with the procoagulant marker D-dimer reflecting fibrin formation both over a 2-h period and in response to acute mental stress. Twenty-one male volunteers (mean age, 47±8 years) underwent the Trier Social Stress Test combining a 3-min preparation phase, a 5-min job interview and 5-min mental arithmetic test before an audience. IL-6, fibrinogen, D-dimer and cortisol were measured immediately before and after stress, and after 45 min and 105 min of recovery from stress. Two distinct areas under the curve were computed to obtain integrated measures of total protein activity over the entire 2-h period and of stress reactivity of proteins. IL-6 (P<0.001), fibrinogen (P=0.001), D-dimer (P=0.021) and cortisol (P<0.001) had all significantly changed across the four time points assessed, as determined by ANOVA. For the entire 2-h period, total fibrinogen activity (R2=0.33, P=0.007) and total cortisol activity (ΔR2=0.17, P=0.034) explained 50% of the variance in total D-dimer activity. Stress-induced changes in fibrinogen (R2=0.47, P=0.001) and IL-6 (ΔR2=0.18, P=0.008) together explained 65% of the variance in D-dimer reactivity to stress. Total fibrin formation was independently predicted by fibrinogen and hypothalamo–pituitary–adrenal activity. Pro-inflammatory and procoagulant changes with stress were associated. Aside from fibrinogen reactivity, IL-6 reactivity was an independent predictor of stress-induced fibrin formation.
Therapeutic uses of autologous endothelial cells for vascular disease
Authors: GULATI Rajiv , LERMAN Amir , SIMARI Robert D.
Published: November 2007

Endothelial cells play important structural and functional roles in vascular homoeostasis. Perturbations in endothelial cell number and function are directly involved with the initiation and progression of multiple cardiovascular diseases, including atherosclerosis, hypertension and congestive heart failure. Attempts to modify these disorders have included pharmacological strategies to improve vascular and thus endothelial function. A goal of biological approaches to these disorders is the delivery of endothelial cells that might act to provide beneficial endothelial-derived factors. However, this approach has generally been limited by the lack of readily available autologous endothelial cells for delivery. The isolation of circulation-derived endothelial progenitor cells allows for direct access to autologous endothelial cells for preclinical and clinical studies. Preclinical studies using autologous endothelial cells have demonstrated beneficial effects when delivered in animal models of vascular injury and grafting. These effects are related to the endothelial nature of the cells and may be paracrine in nature. Ongoing studies are aimed at defining the nature of these effects and optimizing delivery strategies cognizant of these mechanisms.
Increased levels of tumour necrosis factor-α (TNF-α) in patients with Type II diabetes mellitus after myocardial infarction are related to endothelial dysfunction
Authors: Nyström Thomas , Nygren Arne , Sjöholm Åke
Published: November 2007

The pathophysiology of insulin resistance and atherosclerosis may share a common inflammatory basis, maintaining endothelial dysfunction, suggesting why patients with T2DM (Type II diabetes mellitus) have an impaired prognosis after an MI (myocardial infarction), but it remains unclear how these parameters are inter-related. Forty patients with an MI (20 patients with and 20 patients without T2DM) took part in this cross-sectional study. Endothelium-dependent [FMD (flow-mediated dilation)] and -independent [NTG (nitroglycerine)] vasodilatation (determined by ultrasound), SI (insulin sensitivity index; determined by isoglycaemic–hyperinsulinaemic clamp) and serum levels of CRP (C-reactive protein), TNF-α (tumour necrosis factor-α), IL-6 (interleukin 6), resistin and adiponectin (determined by ELISA) were measured. Associations between FMD/NTG and SI, and CRP, TNF-α, IL-6, adiponectin, resistin, lipids, blood pressure, BMI (body mass index) and brachial artery diameter were then assessed. FMD (2.1 compared with 4.7%; P<0.05), NTG (14.9 compared with 21.2%; P<0.05) and SI [4.3 compared with 6.6 10−4 dl·kg−1 of body weight·min−1·(μ-units/ml)−1; P<0.05], and adiponectin levels (3.1 compared with 6.4 μg/ml; P<0.01) were all lower in patients with T2DM. TNF-α (6.9 compared with 1.8 pg/ml; P<0.01) and IL-6 (2.3 compared with 1.2 pg/ml; P<0.01) levels were higher in patients with T2DM, whereas differences in CRP and resistin levels did not attain statistical significance between the two groups. TNF-α concentrations and brachial artery diameter were negatively, whereas SI was positively, correlated with FMD. Adjustment for age weakened the association for SI, whereas TNF-α and brachial artery diameter remained significantly associated with FMD after adjustment for group, age and BMI. Endothelial dysfunction and low-grade inflammation co-exist in T2DM after MI. These results suggest that the endothelium is negatively impacted in multiple ways by the diabetic state after an MI.
Use of the prone position in the acute respiratory distress syndrome: how should we assess benefit?
Authors: Treacher David F.
Published: November 2007

Prone positioning of patients with acute respiratory failure was first suggested over 30 years ago. In the present issue of Clinical Science, Reutershan and co-workers have studied the changes in end-expiratory lung volume in 12 patients with ARDS (acute respiratory distress syndrome) over an 8 h period following manual turning from the supine to prone position. From the data presented, the authors suggest that baseline end-expiratory lung volume could be used to identify responders, and serial measurements would permit appropriate ‘dosing’ of the therapy. Although this is an interesting study that provides data that have rarely been collected when assessing the response to prone positioning, there are a number of limitations that need to be considered. However, despite the limitations, the study does stimulate a number of important questions related not only to the use of the prone position, but also to the management of patients with ARDS in general.
Impact of age on the vasovagal response provoked by sublingual nitroglycerine in routine tilt testing
Authors: Verheyden Bart , Gisolf Janneke , Beckers Frank , Karemaker John M. , Wesseling Karel H. , Aubert André E. , Wieling Wouter
Published: November 2007

NTG (nitroglycerine) is used in routine tilt testing to elicit a vasovagal response. In the present study we hypothesized that with increasing age NTG triggers a more gradual BP (blood pressure) decline due to a diminished baroreflex-buffering capacity. The purpose of the present study was to examine the effect of NTG on baroreflex control of BP in patients with distinct age-related vasovagal collapse patterns. The study groups consisted of 29 patients (16–71 years old, 17 females) with clinically suspected VVS (vasovagal syncope) and a positive tilt test. Mean FAP (finger arterial pressure) was monitored continuously (Finapres). Left ventricular SV (stroke volume), CO (cardiac output) and SVR (systemic vascular resistance) were computed from the pressure pulsations (Modelflow). BRS (baroreflex sensitivity) was estimated in the time domain. In the first 3 min after NTG administration, BP was well-maintained in all patients. This implied an adequate arterial resistance response to compensate for steeper reductions in SV and CO with increasing age. HR (heart rate) increased and the BRS decreased after NTG administration. The rate of mean FAP fall leading to presyncope was inversely related to age (r=0.51, P=0.005). Accordingly, patients with a mean FAP fall >1.44 mmHg/s (median) were generally younger compared with patients with a slower mean FAP-fall (30±10 years compared with 51±17 years; P=0.001). The main determinant of the rate of BP fall on approach of presyncope was the rate of fall in HR (r=0.75, P<0.001). It was concluded that, in older patients, sublingual NTG provokes a more gradual BP decline compared with younger patients. This gradual decline cannot be ascribed to failure of the baroreflex-buffering capacity with increasing age. Age-related differences in the laboratory presentation of a vasovagal episode depend on the magnitude of the underlying bradycardic response.