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M S Setchenska

Publications and source records attributed to M S Setchenska.

18 recordsLinked to original sources
PubMed1992

Phospholipid-dependence of rat liver plasma membrane protein kinase activities--a new approach.

The influence of the phospholipid composition and fluidity on protein kinase A and protein kinase C activities in rat liver plasma membranes was studied. We observed that enrichment of membranes with phosphatidylglycerol, phosphatidylserine, phosphatidylethanolamine and dioleoylphosphatidylcholine caused activation of both protein kinases. Phosphatidylglycerol was found to be most effective activator. The enrichment of plasma membranes with dipalmitoylphosphatidylcholine and sphingomyelin led to decrease in protein kinase A and C activities. The stimulatory effect of phosphatidylglycerol was confirmed in plasma membranes pretreated with exogenous phospholipases A2, C and D, and subsequently enriched with phosphatidylglycerol. We suggest that besides the specific presence of definite phospholipids protein kinases A and C require a more fluid membrane lipid bilayer to display an optimal activity.

Animals↗
PubMed1992

Effect of a sunflower oil-supplemented diet on protein kinase activities of rat liver plasma membranes.

1. The effect of a sunflower oil-enriched diet on plasma membrane-bound protein kinase C, protein kinase A, casein and tyrosine kinase activities was studied. 2. The diet induced an increase in the content of linoleic acid and a decrease in the content of palmitic acid. The anisotropy parameter (rs) of the fluorescence probe DPH and SDPH decreased strongly in the experimental group. 3. Protein kinase C was stimulated more than two times. Tyrosine kinase, protein kinase A and casein kinase activities were increased by 65, 57 and 40%, respectively. 4. We suggest that a more fluid lipid environment favours higher plasma membrane-bound protein kinase activities.

Animals↗
PubMed1992

Effect of triiodothyronine on cAMP-dependent and cAMP-independent protein kinase activities in developing chick embryo liver.

1. Changes in liver cytosol cAMP-dependent kinase and cAMP-independent growth-related quercetin-inhibited casein kinase activities during chick embryo development were studied. 2. Both kinase activities were found to increase continuously during the experimental period. 3. Upon treatment of embryos with triiodothyronine, an activation of cAMP-dependent kinase A and cAMP-independent casein kinase was observed which was most pronounced on days 12 and 14.

Animals↗
PubMed1992

Sphingomyelin-metabolizing enzymes and protein kinase C activity in liver plasma membranes of rats fed with cholesterol-supplemented diet.

The effect of cholesterol-supplemented diet on the activities of rat liver plasma membrane sphingomyelin-metabolizing enzymes and protein kinase C was studied. Protein kinase C, phosphatidylcholine:ceramide-phosphocholine transferase, and phosphatidylethanolamine:ceramide-phosphoethanolamine transferase activities were found to increase continuously and almost in parallel during the experimental period on cholesterol diet (days 10, 20, and 30). Linear regression analysis showed a positive correlation between these activities with correlation coefficients r = 0.959 for protein kinase C and phosphatidylcholine:ceramide-phosphocholine transferase, and r = 0.998 for protein kinase C and phosphatidylethanolamine:ceramide-phosphoethanolamine transferase. On the other hand, protein kinase C activation does not correspond to sphingomyelinase activity changes. These data suggest that protein kinase C activation observed in cholesterol-enriched plasma membranes is due to increased production of diacylglycerol and increased acylation of sphingosine to ceramide.

Animals↗
PubMed1990

Forskolin as an activator of adenylate cyclase complex of differentiating erythroid bone-marrow cells.

The study concerns the manner in which forskolin activates the adenylate cyclase system of differentiating rabbit bone-marrow erythroid cells. The results presented show that forskolin can stimulate the basal activity of adenylate cyclase in the absence of guanine nucleotides in an in vitro assay containing plasma membranes derived from both dividing and non-dividing cells. In the presence of guanine nucleotide the activation of adenylate cyclase by forskolin is increased, but the effect is not additive and is abolished by the beta-thio analogue of GDP. Addition of forskolin to cell cultures causes a transient increase in the activity of adenylate cyclase, which is maximal by 30 minutes and disappears within 24 hours. The conclusion is made that the effect of forskolin on adenylate cyclase complex of differentiating rabbit bone-marrow erythroblasts is similar to the effect of erythropoietin (Bonanou-Tzedaki et al., 1986) and is transdusing via stimulatory guanine nucleotide-regulatory protein.

Adenylyl Cyclases↗
PubMed1990

Adenylate cyclase system of differentiating erythroid cells.

The review provides a survey of current knowledge about the changes in hormone-sensitive adenylate cyclase complex of erythroid cells. The basal enzyme activity decreases continuously during differentiation and maturation. Guanine nucleotides (GTP and GMP-P (NH)P) increase the adenylate cyclase activity of both early and late rabbit bone marrow erythroblasts. The stimulating effect of the beta 2-adrenergic drugs such as L-isoprenaline is limited to the immature cells. L-noradrenaline, a beta 1-agonist is inactive. The lack of response of non-dividing rabbit erythroblasts to beta-adrenergic stimuli is not due to loss of beta-receptors during differentiation, but to a decrease in the effectiveness of the coupling between the components of the system: receptor-guanine nucleotide regulatory protein-catalytic subunit. Prostaglandins E1 and E2 consistently enhance adenylate cyclase activity of erythroblasts on different stages of development. Erythropoietin (0.2 U/ml) causes a transient increase in the activity of adenylate cyclase, which is maximal by 20 min incubation of the cells in the presence of the hormone and disappears within 4 hours. The magnitude of the response to erythropoietin depends on the stage of erythroid cell development and is inverse related to the extent of previous hormonal stimulation of the cell.

Adenylyl Cyclases↗
PubMed1990

Protein phosphorylation in erythroid cell development.

Changes in the phosphorylation of proteins during erythroid cell development have been investigated by assaying the activity of three protein kinases in circulating reticulocytes, and dividing and non-dividing erythroblasts obtained from the bone marrow of anaemic rabbits. Kinase activities decreased during erythroid cell development, but protein phosphorylation was generally limited by substrate availability rather than enzyme activity. Using permeabilized cells some changes in the patterns of proteins phosphorylated by [gamma-32P]ATP were observed during erythroid cell development.

Animals↗
PubMed1988

Independent activation of adenylate cyclase by erythropoietin and isoprenaline.

The possibility that catecholamines modulate the erythropoietin-induced increase in production of cyclic AMP was investigated by examining the effect of erythropoietin and/or L-isoprenaline on the activity of the plasma membrane adenylate cyclase of anaemic rabbit bone marrow erythroblasts. Membranes isolated from cells cultured in the presence of both hormones exhibited both the transient stimulation of basal activity characteristic of erythropoietin action and the loss of the in vitro response to L-isoprenaline, concomitant with the loss of beta-adrenergic receptors, characteristic of L-isoprenaline stimulation. The presence of erythropoietin during cell culture with L-isoprenaline had no effect on the desensitization or number of beta-adrenergic receptors. The stimulation of adenylate cyclase by erythropoietin was observed also in the presence of the beta-antagonist propranolol, when both were added either to whole cells or to isolated membranes. We conclude that these two hormones activate adenylate cyclase independently of each other, via different receptors, with little evidence of cross-modulation.

Adenylyl Cyclases↗
PubMed1987

The effect of erythropoietin on the adenylate cyclase activity of rabbit bone marrow erythroblasts.

The involvement of adenylate cyclase in the response elicited by erythropoietin was investigated in fractionated erythroblasts obtained from anaemic rabbit bone marrow. Addition of 0.2 U/ml erythropoietin to cell cultures caused a transient increase in the activity of plasma membrane adenylate cyclase, which was observed within 5 minutes, was maximal by 20 minutes and disappeared within 4 hours. The magnitude of the response to hormonal stimulation depended on the stage of erythroid cell development and was greater in the more immature cells. Erythropoietin could also stimulate the basal activity of adenylate cyclase in an in vitro assay containing plasma membranes of immature, but not mature, erythroid cells. The degree of activation was hormone-concentration dependent, was maximal at 0.2-0.5 U/ml erythropoietin (5-12 nM) and was observed in the absence of exogenous guanine nucleotides. The in vitro effect of erythropoietin, however, was abolished by GDP (S) and extensive washing of the membranes made hormone action GTP-dependent. The ability of the hormone to stimulate adenylate cyclase activity in vitro was inversely related to the extent of hormonal stimulation in vivo. This desensitization was observed within 20 minutes and persisted for many hours. It is suggested that erythropoietin activates the adenylate cyclase of immature erythroblasts via a receptor and a guanine nucleotide-binding protein with high affinity for GTP.

Adenylyl Cyclases↗
PubMed1986

Classification of beta-adrenergic subtypes in immature rabbit bone marrow erythroblasts.

The beta-adrenergic receptors of immature rabbit bone marrow erythroid cells (proerythroblasts and basophilic erythroblasts) were identified. [125I]iodocyanopindolol bound to membrane preparations derived from these erythroblasts in a rapid, reversible and saturable manner. Scatchard analysis of binding data revealed a single class of binding sites (Hill coefficient of 0.954) with an apparent equilibrium dissociation constant (Kd) of 8 pM, and a density of binding sites (Bmax) of 1.53 pM/10(6) cells, corresponding to 920 receptors per cell. The binding of [125I]iodocyanopindolol was inhibited stereospecifically by concentrations of (-)-propranolol 2 orders of magnitude lower than by the (+)-isomer. Only L-isoprenaline and L-adrenaline activated the adenylate cyclase of immature rabbit erythroblasts, while L-noradrenaline, a beta 1-adrenergic agonist, was inactive. The order of potency of different agonists for displacement of bound [125I]iodocyanopindolol was: isoprenaline greater than adrenaline greater than noradrenaline with respective EC50 (concentration required for half maximal inhibition of binding) of 7.9 X 10(-7) M, 1.5 X 10(-5) M and 7.9 X 10(-5) M. This agonist potency series did not change with differentiation of rabbit bone marrow erythroblasts. The inhibition of specific [125I]iodocyanopindolol binding to immature cells by beta 1- and beta 2-selective drugs (noradrenaline, practolol, procaterol and butoxamine) resulted in linear Hofstee plots. The inhibition curves obtained with procaterol and butoxamine, with apparent Kd values of 3.1 X 10(-9) M and 4.9 X 10(-9) M, further evidence that the high-affinity binding sites correspond to a homogeneous beta 2-receptor subtype.

Adenylyl Cyclases↗
PubMed1986

Stimulation of the adenylate cyclase activity of rabbit bone marrow immature erythroblasts by erythropoietin and haemin.

The effect of two agents of erythroid cell differentiation on the adenylate cyclase activity of fractionated rabbit bone marrow erythroblasts has been investigated. Addition of 0.2U/ml erythropoietin to cell cultures causes a transient increase in the activity of plasma membrane adenylate cyclase, which is maximal by 20 min and disappears within 4 h. The magnitude of the response to hormonal stimulation depends on the stage of erythroid cell development and is greater in the more immature cells. Addition of 50 microM haemin to cultures of erythroblasts also causes an increase in the activity of adenylate cyclase, which differs from the effect of erythropoietin in kinetics and specificity of target cells. With immature cells the haemin-induced stimulation starts after the first hour and continues to increase up to 20 h of culture. Erythropoietin but not haemin can stimulate the basal activity of adenylate cyclase in an in vitro assay containing plasma membranes of immature erythroid cells. The degree of activation depends on the concentration of erythropoietin and is maximal with 0.2-0.5 U/ml hormone (5-12 nM). In the presence of guanine nucleotides the activation of adenylate cyclase by erythropoietin is increased further but the effect is not additive. With respect to the basal and the guanine-nucleotide-stimulated activities of adenylate cyclase erythropoietin acts differently from the beta-agonist l-isoprenaline. The in vitro effect of erythropoietin is abolished by the beta-thio analogue of GDP, GDP[beta S], and extensive washing of membranes makes hormone action GTP-dependent. The stimulation of adenylate cyclase by the addition of erythropoietin to the reaction mixture is inversely related to the extent of previous hormonal stimulation of the cells from which the membranes were prepared. This loss of hormonal responsiveness is due to desensitization or receptor down-regulation and persists for up to 20 h. We conclude that in immature erythroblasts erythropoietin acts via a receptor and a guanine nucleotide-binding protein with high affinity for GTP (EC50 less than 10 nM), whereas haemin appears to activate adenylate cyclase indirectly, as a consequence of progressive perturbations of the plasma membrane.

Adenylyl Cyclases↗
PubMed1978

Studies on the kinetic effects of cyclic nucleotides dependent glutamate dehydrogenase.

Stopped-flow spectrophotometric studies of the reductive amination of L-ketoglutarate by L-glutamate dehydrogenase showed a biphase time course, which consisted of a rapid first phase lasting 60-100 msec and a slow final phase in which the rate of coenzyme oxidation increased until the coenzyme was depleted. The effects of 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP) on the time course of both phases were established. The results showed that in the concentration ranges used the cyclic nucleotides accelerate the catalytic reaction. The effect of cAMP was more pronounced as compared to cGMP. In all cases this influence was most clearly expressed in the first phase. Using an Arrhenius plot the activation parameters were calculated. The experiments with cAMP and cGMP at different molar ratios showed that a specific cAMP binding may occur.

Amination↗
PubMed1978

Changes in the lactate dehydrogenase isoenzyme pattern during differentiation of rabbit bone-marrow erythroid cells.

1. Differentiation and maturation of rabbit bone-marrow erythroid cells was accompanied by a 15-fold decrease in lactate dehydrogenase activity from approx. 0.1pmol of NADH utilized/min per cell in basophilic cells to 0.007 pmol of NADH/min per cell in reticulocytes. 2. In early cells, cell division takes place with a corresponding decrease in cell volume, but the concentration of lactate dehydrogenase remains almost constant. 3. When cell division ceases, qualitative as well as quantitative changes in the lactate dehydrogenase isoenzyme pattern become apparent and reticulocytes were found to contain almost exclusively the H4 isoenzyme, whereas early erythroblasts contained also the M4 and hybrid isoenzymes. 4. Extracts from a lysosome-enriched subcellular fraction of bone-marrow erythroid cells specifically degraded the M4 isoenzyme in vitro, but the H4 form was stable. It is suggested that lysosomal enzymes are involved in bringing about the observed changes in lactate dehydrogenase isoenzyme patterns in vivo.

Animals↗