scholarly journals Membrane stiffness is a key determinant of E coli MscS channel mechanosensitivity

2019 ◽  
Author(s):  
Feng Xue ◽  
Charles D. Cox ◽  
Navid Bavi ◽  
Paul R Rohde ◽  
Yoshitaka Nakayama ◽  
...  
Keyword(s):  
Response Curve ◽  
Membrane Lipids ◽  
Bending Rigidity ◽  
Rightward Shift ◽  
E Coli ◽  
Tension Response ◽  
Global Properties ◽  
Membrane Stiffness ◽  
Membrane Bending ◽  
Branched Chain

AbstractProkaryotic mechanosensitive (MS) channels have an intimate relationship with membrane lipids. Membrane lipids may influence channel activity by directly interacting with bacterial MS channels or by influencing the global properties of the membrane such as area stretch and bending moduli. Previous work has implicated membrane stiffness as a key determinant of the mechanosensitivity of E. coli (Ec)MscS. Here we systematically tested this hypothesis using patch fluorometry of azolectin liposomes doped with lipids of increasing area stretch moduli. Increasing DOPE content of azolectin liposomes causes a rightward shift in the tension response curve of EcMscS. These rightward shifts are further magnified by the addition of stiffer forms of PE such as the branched chain lipid DPhPE and the fully saturated lipid DSPE. Furthermore, a comparison of the branched chain lipid DPhPC to the stiffer DPhPE showed a rightward shift in the tension response curve in the presence of the stiffer DPhPE. We show that these changes are not due to changes in membrane bending rigidity as the tension threshold of EcMscS in membranes doped with PC18:1 and PC18:3 are the same, despite a two-fold difference in their bending rigidity. We also show that after prolonged pressure application sudden removal of force in softer membranes causes a rebound reactivation of EcMscS and we discuss the relevance of this phenomenon to bacterial osmoregulation. Collectively, our data demonstrate that membrane stiffness is a key determinant of the mechanosensitivity of EcMscS.

Role of endothelin-converting enzyme, chymase and neutral endopeptidase in the processing of big ET-1, ET-1(1-21) and ET-1(1-31) in the trachea of allergic mice

2002 ◽  
Vol 103 (s2002) ◽  
pp. 353S-356S ◽  
Author(s):  
Benjamin A. DE CAMPO ◽  
Roy G. GOLDIE ◽  
Arco Y. JENG ◽  
Peter J. HENRY
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Response Curve ◽  
Histological Analysis ◽  
Neutral Endopeptidase ◽  
Converting Enzyme ◽  
Rightward Shift ◽  
Endothelin Converting Enzyme ◽  
Mast Cell Chymase

The present study examined the roles of endothelin-converting enzyme (ECE), neutral endopeptidase (NEP) and mast cell chymase as processors of the endothelin (ET) analogues ET-1(1–21), ET-1(1–31) and big ET-1 in the trachea of allergic mice. Male CBA/CaH mice were sensitized with ovalbumin (10µg) delivered intraperitoneal on days 1 and 14, and exposed to aerosolized ovalbumin on days 14, 25, 26 and 27 (OVA mice). Mice were killed and the trachea excised for histological analysis and contraction studies on day 28. Tracheae from OVA mice had 40% more mast cells than vehicle-sensitized mice (sham mice). Ovalbumin (10µg/ml) induced transient contractions (15±3% of the Cmax) in tracheae from OVA mice. The ECE inhibitor CGS35066 (10µM) inhibited contractions induced by big ET-1 (4.8-fold rightward shift of dose-response curve; P<0.05), but not those induced by either ET-1(1–21) or ET-1(1–31). The chymase inhibitors chymostatin (10µM) and Bowman-Birk inhibitor (10µM) had no effect on contractions induced by any of the ET analogues used. The NEP inhibitor CGS24592 (10µM) inhibited contractions induced by ET-1(1–31) (6.2-fold rightward shift; P<0.05) but not ET-1(1–21) or big ET-1. These data suggest that big ET-1 is processed predominantly by a CGS35066-sensitive ECE within allergic airways rather than by mast cell-derived proteases such as chymase. If endogenous ET-1(1–31) is formed within allergic airways, it is likely to undergo further conversion by NEP to more active products.

scholarly journals Construction of an artificial biosynthetic pathway for hyperextended archaeal membrane lipids in the bacterium Escherichia coli

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Ryo Yoshida ◽  
Hisashi Hemmi
Keyword(s):  
Escherichia Coli ◽  
Biosynthetic Pathway ◽  
Membrane Lipids ◽  
Extreme Environments ◽  
Halophilic Archaea ◽  
Coli Strain ◽  
Glycerol Moiety ◽  
Hyperthermophilic Archaeon ◽  
E Coli ◽  
Aeropyrum Pernix

Abstract Archaea produce unique membrane lipids, which possess two fully saturated isoprenoid chains linked to the glycerol moiety via ether bonds. The isoprenoid chain length of archaeal membrane lipids is believed to be important for some archaea to thrive in extreme environments because the hyperthermophilic archaeon Aeropyrum pernix and some halophilic archaea synthesize extended C25,C25-archaeal diether-type membrane lipids, which have isoprenoid chains that are longer than those of typical C20,C20-diether lipids. Natural archaeal diether lipids possessing longer C30 or C35 isoprenoid chains, however, have yet to be isolated. In the present study, we attempted to synthesize such hyperextended archaeal membrane lipids. We investigated the substrate preference of the enzyme sn-2,3-(digeranylfarnesyl)glycerol-1-phosphate synthase from A. pernix, which catalyzes the transfer of the second C25 isoprenoid chain to the glycerol moiety in the biosynthetic pathway of C25,C25-archaeal membrane lipids. The enzyme was shown to accept sn-3-hexaprenylglycerol-1-phosphate, which has a C30 isoprenoid chain, as a prenyl acceptor substrate to synthesize sn-2-geranylfarnesyl-3-hexaprenylglycerol-1-phosphate, a supposed precursor for hyperextended C25,C30-archaeal membrane lipids. Furthermore, we constructed an artificial biosynthetic pathway by introducing 4 archaeal genes and 1 gene from Bacillus subtilis in the cells of Escherichia coli, which enabled the E. coli strain to produce hyperextended C25,C30-archaeal membrane lipids, which have never been reported so far.

Effects of inhibitors of cyclic nucleotide phosphodiesterase on actions of cholecystokinin, bombesin, and carbachol on pancreatic acini

1983 ◽  
Vol 245 (5) ◽  
pp. G676-G680
Author(s):  
J. D. Gardner ◽  
V. E. Sutliff ◽  
M. D. Walker ◽  
R. T. Jensen
Keyword(s):  
Dose Response ◽  
Cyclic Nucleotide ◽  
Response Curve ◽  
Dose Response Curve ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Rightward Shift ◽  
Stimulation Of

In dispersed acini from guinea pig pancreas two inhibitors of cyclic nucleotide phosphodiesterase, Ro 20-1724 and 3-isobutyl-1-methylxanthine (IBMX), augmented the increase in amylase secretion caused by supramaximal concentrations of cholecystokinin but did not alter the stimulation of enzyme secretion caused by bombesin. The augmentations of the action of cholecystokinin caused by Ro 20-1724 or IBMX could be reproduced by 8-bromo-cAMP. When tested alone or with theophylline, cholecystokinin did not alter cAMP in pancreatic acini; however, with Ro 20-1724 or IBMX, concentrations of cholecystokinin that were supramaximal for stimulating amylase secretion caused a significant increase in cellular cAMP. These findings indicate that Ro 20-1724 and IBMX augment the action of cholecystokinin on enzyme secretion by inhibiting cyclic nucleotide phosphodiesterase and allowing a significant cholecystokinin-induced increase in cellular cAMP. IBMX but not Ro 20-1724 caused a parallel rightward shift in the dose-response curve for the stimulation of amylase secretion caused by carbachol. IBMX also caused a parallel rightward shift in the dose-response curve for the stimulation of outflux of 45Ca caused by carbachol. These results indicate that IBMX, but not Ro 20-1724, can function as a muscarinic cholinergic antagonist.

Nanoindentation hardness of a Steigmann–Ogden surface bounding an elastic half-space

2018 ◽  
Vol 24 (9) ◽  
pp. 2754-2766 ◽  
Author(s):  
Xiaobao Li ◽  
Changwen Mi
Keyword(s):  
Surface Tension ◽  
Half Space ◽  
Surface Elasticity ◽  
Elastic Half Space ◽  
Indentation Hardness ◽  
Bending Rigidity ◽  
Size Dependent ◽  
Significant Difference ◽  
Nanoindentation Hardness ◽  
Membrane Stiffness

Previous studies demonstrate that, for nanostructures under transverse bending, the effective Young modulus is appreciably greater (in magnitude) than that of the same elements under axial loads. Therefore, in addition to the conventional residual surface tension and membrane stiffness, the curvature dependence of surface energy is desired for inhomogeneously strained nanostructures. In this paper, we aim to reevaluate the size-dependent nanoindentation hardness of an elastic half-space subjected to nanosized frictionless traction, through the use of both the curvature-independent Gurtin–Murdoch and the curvature-dependent Steigmann–Ogden models of surface elasticity. The nanoindentation problem is solved by the integration of Boussinesq’s method of displacement potentials and Hankel integral transforms. As examples, the effects of residual surface tension, membrane stiffness, and bending rigidity of the half-space boundary are parametrically analyzed in detail for a uniform circular pressure and a concentrated normal force. The observations in semianalytical calculations suggest a significant difference in the nanoindentation hardnesses predicted from the two popular models of surface mechanics. In most cases, the inclusion of bending rigidity results in smaller displacements and stresses, and therefore higher indentation hardness. Based on physically interpretable numerical values of surface material properties, we show that a curvature-dependent model of surface elasticity is required in order to characterize the size-dependent feature of nanoindentation problems correctly.

scholarly journals Impact of Sterol Tilt on Membrane Bending Rigidity in Cholesterol and 7DHC-Containing DMPC Membrane

2012 ◽  
Vol 102 (3) ◽  
pp. 413a
Author(s):  
George Khelashvili ◽  
Michael Rappolt ◽  
See-Wing Chiu ◽  
Georg Pabst ◽  
Daniel Harries
Keyword(s):  
Bending Rigidity ◽  
Membrane Bending ◽  
Dmpc Membrane

scholarly journals The Multi-Copper-Ion Oxidase CueO of Salmonella enterica Serovar Typhimurium Is Required for Systemic Virulence

2010 ◽  
Vol 78 (5) ◽  
pp. 2312-2319 ◽  
Author(s):  
Maud E. S. Achard ◽  
Jai J. Tree ◽  
James A. Holden ◽  
Kim R. Simpfendorfer ◽  
Odilia L. C. Wijburg ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Copper Ions ◽  
Copper Ion ◽  
Mesenteric Lymph Nodes ◽  
E Coli ◽  
Significant Difference ◽  
Serovar Typhimurium ◽  
Branched Chain ◽  
Periplasmic Enzyme

ABSTRACT Salmonella enterica serovar Typhimurium possesses a multi-copper-ion oxidase (multicopper oxidase), CueO (also known as CuiD), a periplasmic enzyme known to be required for resistance to copper ions. CueO from S. Typhimurium was expressed as a recombinant protein in Escherichia coli, and the purified protein exhibited a high cuprous oxidase activity. We have characterized an S. Typhimurium cueO mutant and confirmed that it is more sensitive to copper ions. Using a murine model of infection, it was observed that the cueO mutant was significantly attenuated, as indicated by reduced recovery of bacteria from liver and spleen, although there was no significant difference in recovery from Peyer's patches and mesenteric lymph nodes. However, the intracellular survival of the cueO mutant in unprimed or gamma-interferon-primed murine macrophages was not statistically different from that of wild-type Salmonella, suggesting that additional host factors are involved in clearance of the cueO mutant. Unlike a cueO mutant from E. coli, the S. Typhimurium cueO mutant did not show greater sensitivity to hydrogen peroxide and its sensitivity to copper ions was not affected by siderophores. Similarly, the S. Typhimurium cueO mutant was not rescued from copper ion toxicity by addition of the branched-chain amino acids and leucine.

Calculation of membrane bending rigidity using field-theoretic umbrella sampling

2015 ◽  
Vol 143 (24) ◽  
pp. 243155 ◽  
Author(s):  
Y. G. Smirnova ◽  
M. Müller
Keyword(s):  
Umbrella Sampling ◽  
Bending Rigidity ◽  
Membrane Bending

scholarly journals Pretreatment or Posttreatment with Aripiprazole Attenuates Methamphetamine-induced Stereotyped Behavior in Mice

2015 ◽  
Vol 9s1 ◽  
pp. JEN.S27733 ◽  
Author(s):  
Nobue Kitanaka ◽  
Junichi Kitanaka ◽  
F. Scott Hall ◽  
Masaru Kayama ◽  
Hironobu Sugimori ◽  
...  
Keyword(s):  
Response Curve ◽  
Partial Agonist ◽  
Stereotyped Behavior ◽  
Dependent Manner ◽  
Third Generation ◽  
Potential Treatment ◽  
Single Administration ◽  
Rightward Shift ◽  
Stereotypical Behavior ◽  
Dose Dependent

Aripiprazole is a third-generation atypical antipsychotic and a dopamine D2 receptor partial agonist. In the present study, we investigated whether a single administration of aripiprazole to mice, either as a pretreatment or as a posttreatment, would affect stereotypy induced by methamphetamine (METH). Pretreatment of male ICR mice with aripiprazole (1 or 10 mg/kg, i.p.) attenuated the incidence of METH-induced stereotypical behavior in a dose-dependent manner. Pretreatment of mice with 1 mg/kg aripiprazole produced an increase in the locomotor activity in mice treated with METH compared with mice treated with vehicle plus METH and with 10 mg/kg aripiprazole plus METH. This increase in locomotion is indicative of a rightward shift in the dose-response curve for METH, consistent with a shift in the type of stereotypical behavior observed from biting to sniffing. Aripiprazole posttreatment, after METH-induced stereotypical behavior, was fully expressed and also significantly attenuated overall stereotypy in an aripiprazole dose-dependent manner. These data suggest that the antagonism of METH effects by aripiprazole should be investigated as a potential treatment for acute METH overdose.

scholarly journals β-Ketoacyl-Acyl Carrier Protein Synthase III (FabH) Is a Determining Factor in Branched-Chain Fatty Acid Biosynthesis

2000 ◽  
Vol 182 (2) ◽  
pp. 365-370 ◽  
Author(s):  
Keum-Hwa Choi ◽  
Richard J. Heath ◽  
Charles O. Rock
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Chain Fatty Acid ◽  
Carrier Protein ◽  
Acid Biosynthesis ◽  
Biochemical Basis ◽  
E Coli ◽  
Branched Chain

ABSTRACT A universal set of genes encodes the components of the dissociated, type II, fatty acid synthase system that is responsible for producing the multitude of fatty acid structures found in bacterial membranes. We examined the biochemical basis for the production of branched-chain fatty acids by gram-positive bacteria. Two genes that were predicted to encode homologs of the β-ketoacyl-acyl carrier protein synthase III of Escherichia coli (eFabH) were identified in theBacillus subtilis genome. Their protein products were expressed, purified, and biochemically characterized. Both B. subtilis FabH homologs, bFabH1 and bFabH2, carried out the initial condensation reaction of fatty acid biosynthesis with acetyl-coenzyme A (acetyl-CoA) as a primer, although they possessed lower specific activities than eFabH. bFabH1 and bFabH2 also utilized iso- and anteiso-branched-chain acyl-CoA primers as substrates. eFabH was not able to accept these CoA thioesters. Reconstitution of a complete round of fatty acid synthesis in vitro with purified E. coli proteins showed that eFabH was the only E. colienzyme incapable of using branched-chain substrates. Expression of either bFabH1 or bFabH2 in E. coli resulted in the appearance of a branched-chain 17-carbon fatty acid. Thus, the substrate specificity of FabH is an important determinant of branched-chain fatty acid production.

Evidence against KATP channel involvement in adenosine receptor-mediated dilation of epicardial vessels

1994 ◽  
Vol 267 (2) ◽  
pp. H716-H724 ◽  
Author(s):  
S. R. Makujina ◽  
H. A. Olanrewaju ◽  
S. J. Mustafa
Keyword(s):  
Adenosine Receptor ◽  
Katp Channel ◽  
Response Curve ◽  
Channel Blocker ◽  
Rightward Shift ◽  
Prostaglandin F2 Alpha ◽  
Phenylisopropyl Adenosine ◽  
Concentration Response Curve ◽  
Channel Activator

The purpose of this study was to determine whether ATP-glyburide-sensitive K+ (KATP-glyburide) channels are involved in the adenosine-induced vasorelaxation of porcine and canine epicardial vessels in vitro. Adenosine and its analogues, 2-chloroadenosine (CAD), 5'-N-ethylcarboxamidoadenosine (NECA), R-N6-(2-phenylisopropyl)adenosine (R-PIA), N6-cyclopentyladenosine (CPA), N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)]adenosine (DPMA), 2-phenylaminoadenosine (CV-1808), 2-[m-(carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS-22988), 2-[(2-cyclohexylethyl)amino]adenosine (CGS-22492), 2-[(p-amino)phenethylamino]adenosine (APE), and 2-(1-octynyl)adenosine (YT-146) (10 nM-100 microM), produced concentration-dependent relaxations in endothelium-intact and -denuded arterial ring segments contracted with 30 mM KCl, 10 nM endothelin-1, or 10 microM prostaglandin F2 alpha. Sodium nitroprusside (SNP; 1 nM-10 microM) and KATP-channel activator, pinacidil (10 nM-10 microM), also produced similar vasodilatory responses. Glyburide, a KATP-channel blocker, caused a rightward shift of the concentration-response curve to pinacidil but did not alter the responses elicited by SNP or adenosine and its analogues. The data suggest that KATP-glyburide channels are not involved in the mechanism whereby adenosine and its analogues elicit their vasorelaxant response in isolated porcine or canine epicardial vessels.

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