Cortisol effect on (Na++K+)-stimulated ATPase activity and on bilayer fluidity of dog brain synaptosomal plasma membranes

1985 ◽  
Vol 10 (12) ◽  
pp. 1605-1613 ◽  
Author(s):  
George Deliconstantinos
Keyword(s):  
Atpase Activity ◽  
Plasma Membranes ◽  
Dog Brain ◽  
Synaptosomal Plasma Membranes

Stimulation of Brain Synaptosome - Associated Adenylate Cyclase by Acidic Phospholipids

1984 ◽  
Vol 39 (11-12) ◽  
pp. 1196-1198 ◽  
Author(s):  
Stylianos Tsakiris
Keyword(s):  
Enzyme Activity ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Protein S ◽  
Enzyme Activation ◽  
Dog Brain ◽  
The Central Nervous System ◽  
Acidic Phospholipids ◽  
Synaptosomal Plasma Membranes ◽  
Stimulation Of

Phosphatidylserine (PS), phosphatidylinositol (PIN) or phosphatidylglycerol (PGL) incubated with synaptosomal plasma membranes (SPM) of dog brain, stimulated adenylate cyclase. The enzyme activity showed a dramatic increase at around 1.6 μmol PS/mg protein, while use of higher concentrations led to inhibition of the activity with respect to the maximal percentage of stimulation. Moreover, PS stimulated the dopamine-sensitive adenylate cyclase. Solubilization of SPM by the detergent Lubrol-PX did not affect the enzyme activation induced by dopamine. The solubilization, also, showed that the enzyme activity does not change at any PS, PIN or PGL concentration used. These results indicate that acidic phospholipids do not directly act on adenylate cyclase, but indirectly, affecting the membrane fluidity probably. Such modifications of interactions through lipid-protein(s) of adenylate cyclase may have implications to physiological responses to hormones or/and neurotransm itters in the central nervous system.

scholarly journals Influence of phosphatidylserine on (Na+ + K+)-stimulated ATPase and acetylcholinesterase activities of dog brain synaptosomal plasma membranes

1984 ◽  
Vol 220 (1) ◽  
pp. 301-307 ◽  
Author(s):  
S Tsakiris ◽  
G Deliconstantinos
Keyword(s):  
Protein Interactions ◽  
Plasma Membranes ◽  
Physiological Processes ◽  
Maximal Stimulation ◽  
Dog Brain ◽  
The Central Nervous System ◽  
Hill Coefficients ◽  
Lipid Protein Interactions ◽  
Synaptosomal Plasma Membranes ◽  
Allosteric Properties

Phosphatidylserine (PtdSer) incubated with synaptosomal plasma membranes (SPM) of dog brain is incorporated into SPM in proportion to its concentration in the incubation medium. Low PtdSer concentrations progressively activated the SPM-associated (Na+ + K+)-stimulated ATPase and acetylcholinesterase. Increasing the PtdSer concentration above that which maximally stimulated the enzyme activities effected a progressive inhibition with respect to maximal stimulation. Arrhenius plots of (Na+ + K+ + Mg2+)-dependent ATPase and 5′-nucleotidase revealed a clear break at 23-24 degrees C for both enzymes in SPM untreated with PtdSer (controls), whereas a linear relation was obtained for SPM treated with PtdSer. Changes in the allosteric properties of (Na+ + K+)-stimulated ATPase by fluoride (F-) and/or of 5′-nucleotidase by concanavalin A (i.e. changes of Hill coefficients) indicate that PtdSer increases the membrane fluidity. These results suggest that modifications of lipid-protein interactions in SPM induced by PtdSer may have implications in the physiological processes in the central nervous system.

Evoked effects of cholesterol binding on integral proteins and lipid fluidity of dog brain synaptosomal plasma membranes

1989 ◽  
Vol 67 (1) ◽  
pp. 16-24 ◽  
Author(s):  
George Deliconstantinos ◽  
Lioudmila Kopeikina ◽  
Vassiliki Villiotou
Keyword(s):  
Fluorescence Polarization ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Break Point ◽  
Hill Coefficient ◽  
Dog Brain ◽  
Integral Proteins ◽  
The Hill ◽  
Synaptosomal Plasma Membranes ◽  
Allosteric Properties

Binding of cholesterol into dog brain synaptosomal plasma membranes (SPM) within the limits of concentration used (0.5–5 μM) follows an exponential curve described by the general formula y = a∙ebx. This curve, which represents the total binding (specific and nonspecific), acquires sigmoid character in the presence of 100 μM cholesterol glucoside, with a Hill coefficient of h = 2.98 ± 0.18. The specific activity of the Na+/K+-transporting ATPase and Ca2+-transporting ATPase rose after a 2-h preincubation of SPM with cholesterol (up to 5 μM) or its glucoside (up to 50 μM) to at least 50% above their original values. Fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) increased with cholesterol glucoside (50 μM) incorporation. Cholesterol (5 μM) had no effect on the DPH fluorescence polarization. Arrhenius plots of Na+/K+-transporting ATPase activity exhibited a break point at 23.2 ± 1.1 °C in control SPM, which was elevated to 29.5 ± 1.4 °C in SPM treated with cholesterol glucoside (50 μM) and abolished in SPM treated with cholesterol (5 μM). The allosteric properties of SPM-bound Na+/K+-transporting ATPase inhibited by F− and Ca2+-transporting ATPase inhibited by Na+ (as reflected by changes in the Hill coefficient) were modulated by cholesterol. It could be stated that cholesterol glucoside (50 μM) produced an increased packing of the bulk lipids, while cholesterol (5 μM) increased the fluidity of the lipid microenvironment of both Na+/K+-transporting ATPase and Ca2+-transporting ATPase.Key words: cholesterol, cholesterol glucoside, (NA+/K+)ATPase, Ca2+-ATPase, membrane fluidity, fluorescence polarization.

Cooperative nature of the binding of cholesterol on to synaptosomal plasma membranes of dog brain

1981 ◽  
Vol 643 (3) ◽  
pp. 642-649 ◽  
Author(s):  
Spyridon G.A. Alivisatos, ◽  
George Deliconstantinos ◽  
Anastasios Papaphilis ◽  
George P. Theodosiadis
Keyword(s):  
Plasma Membranes ◽  
Dog Brain ◽  
Synaptosomal Plasma Membranes

scholarly journals Hepatic endosome fractions contain an ATP-driven proton pump

1985 ◽  
Vol 225 (1) ◽  
pp. 51-58 ◽  
Author(s):  
T Saermark ◽  
N Flint ◽  
W H Evans
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Atpase Activity ◽  
Proton Pump ◽  
Subcellular Distribution ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Ph Gradients ◽  
Subcellular Organelle ◽  
Liver Homogenates

Endosome fractions were isolated from rat liver homogenates on the basis of the subcellular distribution of circulating ligands, e.g. 125I-asialotransferrin internalized by hepatocytes by a receptor-mediated process. The distribution of endocytosed 125I-asialotransferrin 1-2 min and 15 min after uptake by liver and a monensin-activated Mg2+-dependent ATPase activity coincided on linear gradients of sucrose and Nycodenz. The monensin-activated Mg2+-ATPase was enriched relative to the liver homogenates up to 60-fold in specific activity in the endosome fractions. Contamination of the endosome fractions by lysosomes, endoplasmic reticulum, mitochondria, plasma membranes and Golgi-apparatus components was low. By use of 9-aminoacridine, a probe for pH gradients, the endosome vesicles were shown to acidify on addition of ATP. Acidification was reversed by addition of monensin. The results indicate that endosome fractions contain an ATP-driven proton pump. The ionophore-activated Mg2+-ATPase in combination with the presence of undegraded ligands in the endosome fractions emerge as linked markers for this new subcellular organelle.

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