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F J Moreno

Publications and source records attributed to F J Moreno.

At least 37 records · Page 2Linked to original sources
PubMed1995

Casein kinase 2 inactivation by Mg2+, Mn2+ and Co2+ ions.

Mg2+ as well as Mn2+, and Co2+, which may substitute Mg2+ in the mental ion requirement of casein kinase 2 (Gatica et al., FEBS Lett: 315:173-173, 1993), have been repeatedly reported to display an optimal concentration at which activity of casein kinase 2 is maximal. As far as we know this intriguing property has always been observed with casein as substrate. This phosphoprotein is not the natural substrate of the enzyme, and it is well known that it binds divalent metal ions, which provoke the aggregation and precipitation of the protein. Since an optimal concentration of metal ion might have a regulatory role, we have examined if it is a consequence of the particular properties of casein, or it is an inherent property of the enzyme, extensive to other substrates. We have used the type II regulatory subunit of protein kinase A which is a physiological substrate of the enzyme, and the peptide RRREEETEEE as a specific substrate. No optimal concentration of Mg2+ is observed when these two substrates are used. The results explain, however, why that optimum is observed with casein. Although low concentration of Mn2+, and Co2+ render about 25% of the maximal activity found with Mg2+, they inactivate the enzyme almost fully at concentrations at which Mg2+ yield the maximal activity.

Amino Acid Sequence↗
PubMed1995

Glycogen synthase kinase 3 phosphorylates recombinant human tau protein at serine-262 in the presence of heparin (or tubulin).

Tau protein, the major component of the aberrant structures termed paired helical filaments (PHFs) present in the brain of Alzheimer's disease patients, is pathologically phosphorylated in sites in and around the tubulin-binding sites. A single protein kinase, glycogen synthase kinase 3 (GSK 3), is able to phosphorylate tau at the flanking regions and, additionally, at the tubulin-binding motifs if heparin or tubulin is present. Serines-262 and -324 have been found to be modified at the tubulin-binding region of tau protein by GSK 3 in the presence of heparin or tubulin.

Amino Acid Sequence↗
PubMed1994

Bromocriptine treatment increases lipolysis and steady-state levels of G proteins in adipocytes from lactating rats.

An increase in the rate of lipogenesis and a decrease in the lipolytic response to catecholamines can be observed in adipocytes after weaning or litter removal. Bromocriptine treatment of lactating rats also produces an increase in lipogenesis but fails to decrease the lipolytic response of adipocytes to catecholamines seen after weaning or litter removal. No changes in total number or affinity of beta-adrenergic receptors or adenosine A1 receptors were detected by bromocriptine treatment using radioligand binding assays. However, we observed an increase in the amount of radioactivity from [32P]NAD+ incorporated into alpha-Gs (192 +/- 26%) and alpha-Gi (178 +/- 33%) by cholera- and pertussis-toxin-catalyzed ADP-ribosylation, respectively, with the same treatment, Immunoblotting using RM/1 and AS/7 antisera, which specifically recognize alpha-Gs and alpha-Gi 1,2, respectively, confirmed the increase in the steady-state levels of these G-protein alpha-subunits. The increase in the steady-state levels of alpha-Gs may account, at least in part, for the increased lipolytic response of adipocytes to catecholamines in bromocriptine-treated rats.

Adenosine↗
PubMed1993

A polylysine-induced aggregation of substrate accompanies the stimulation of casein kinase II by polylysine.

Casein kinase II (CK-II) activation by polylysine parallels an aggregation of substrates promoted by the polycation. CK-II is known to be stimulated by basic polypeptides and polyamines. The mechanism by which this stimulation takes place, however, is not yet fully understood. Here we show that, in the usual CK-II assay, polylysine induces the aggregation of casein. This aggregation has been monitored by turbidimetry, electron microscopy and gel filtration. The polylysine-concentration-dependence of the casein aggregation parallels the polylysine-concentration-dependence of the enzyme stimulation. In the presence of polylysine the enzyme is incorporated into the casein aggregates promoted by the polycation, thus supporting the view that this substrate aggregation is directly related to the mechanism of CK-II stimulation. Preliminary results show that a similar parallelism occurs with other natural substrates of the enzyme. The physiological meaning of this substrate aggregation, and its possible relation to other polylysine-stimulated enzymes and polylysine-aggregated proteins, are discussed.

Animals↗
PubMed1992

Dipyridamole stimulates types II cAMP-dependent protein kinase in vitro.

Dipyridamole activates in vitro type II cAMP-dependent protein kinase. This agent stimulates the autophosphorylation of the regulatory subunit in the presence of cAMP but not so in the absence of the cyclic nucleotide. The activation was also observed with exogenous substrates such as casein, histone 2A and MAP2. This stimulation did not seem to be related to the cAMP binding to the R II subunit of the enzyme. Competition binding experiments showed that dipyridamole does not compete with adenosine for the A1 receptor. The results suggest that the reported regulatory properties of dipyridamole on lipid metabolism (González-Nicolás et al. Int J Biochem 21: 883-888, 1989) might be mediated through a direct action--an activation--on the catalytic subunit of a cAMP-dependent protein kinase.

Adipose Tissue↗
PubMed1992

Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats.

The effects of litter removal on the status of different components of the hormone-sensitive adenylate cyclase system were analysed in plasma membranes of rat adipocytes. These effects were correlated with the decreased lipolytic response of adipose tissue. No changes in total number of A1 adenosine receptors or their affinity were detected in response to litter removal. In contrast, beta-adrenergic receptors showed a decrease (35%) in total number of receptors, without any significant change in their affinity. The status of alpha-GS and alpha-Gi, the alpha-subunits of G proteins which mediate stimulation and inhibition respectively of adenylate cyclase, were probed by cholera- and pertussis-toxin-catalysed ADP-ribosylation respectively and by immunoblot. Associated with litter removal, decreases of 63% and 62% in the incorporation of [alpha 32P]ADP-ribose catalysed by cholera toxin and pertussis toxin into alpha-Gs and alpha-Gi respectively were detected. Immunoblotting using RM/1 (anti-alpha-Gs) and AS/7 (anti-alpha-Gi) antisera also showed decreases in the levels of alpha-Gs (52%) and alpha-Gi (55%) in adipocyte membranes from litter-removed rats compared with lactating rats. Alterations in the status of hormone-sensitive adenylate cyclase components, such as those described herein, may be biochemical mechanism(s) by which adipose tissue shows a decreased lipolytic response during recovery from lactation.

Adenylyl Cyclases↗
PubMed1992

Characterization and immunolocalization of a nucleolar antigen with anti-NOR serum in HeLa cells.

We have used a serum from a patient with rheumatoid arthritis and found it to immunoblot with a 92- to 88-kDa protein doublet with an isoelectric point of around 7.5 after mono- and two-dimensional electrophoresis in whole HeLa cells. By means of immunofluorescence and immunoelectron microscopy we have found it to specifically react with the nucleolar fibrillar component. After quantitative analysis under the electron microscope, we have demonstrated a similar labeling both in the fibrillar centers and the dense fibrillar component, using two different gold-coupled markers. When transcription was inhibited under physiological conditions (mitosis) or after AMD treatment the antigen remained, as shown by immunoblotting and immunolabeling with anti-NOR serum. These biochemical characteristics, which coincide with those of the ribosomal transcription human upstream binding factor, together with the immunolocalization with anti-NOR serum, allow us to discuss the possible role of these antigens in rDNA transcription.

Arthritis, Rheumatoid↗
PubMed1992

Characterization and immunolocalization of RNA polymerase I transcription factor UBF with anti-NOR serum in protozoa, higher plant and vertebrate cells.

We have used anti-NOR serum from a patient with rheumatoid arthritis, to study its reactivity on different phylogenetically separated species such as protozoa, higher plants, birds and mammals. The biochemical characteristics of the antigens detected after applying mono- and two-dimensional electrophoresis and electrophoretic transfers confirm that they correspond to the rRNA polymerase I transcription factor UBF. We have demonstrated the different molecular sizes, depending on the cell complexity, but the same neutral isoelectric points in whole cell extracts of the different species. We have also demonstrated an immunolocalization of this transcription factor to the fibrillar component in all the species studied. These results suggest a high conservation of UBF throughout evolution and the possibility of using this anti-NOR serum as a tool for the study of the structure, nucleolar organization and functional roles of the different nucleolar components.

Allium↗
PubMed1990

Different phosphorylation behaviour of regulatory subunit isoforms of type II cAMP-dependent protein kinase from bovine heart.

Two forms of the regulatory subunit of the type II cAMP-dependent protein kinase (RII55 and RII52) were identified from bovine heart by gel electrophoretic behaviour. After autophosphorylation the RII55 isoform migrated more slowly (RII55/57) while the migration of RII52 isoform did not shift. Both isoforms showed different affinity for cAMP. The RII55/57 isoform was eluted from a cAMP-agarose column at 10 mM cAMP at low ionic strength whereas the RII52 isoform required cAMP, plus 2M NaCl. Partial proteolysis, using trypsin or formic acid, of autophosphorylated regulatory subunit isoforms resulted in different cleavage pattern as determined by peptide mapping. However, the V8 125I-peptides patterns of both isoforms are quite similar. Incubation of partially purified holoenzyme with 10 nM [gamma-32P]ATP (low ATP concentration) yielded a single band of Mr = 57,000 which corresponds to the RII55/57 isoform. The incubation, however, at 20 microM [gamma-32P]ATP yielded two phosphobands corresponding to both RII55/57 and RII52 isoforms. The phosphorylation of RII52 took place with a lower efficiency and was more sensitive to the cAMP than the corresponding phosphorylation of the RII55/57.

Adenosine Triphosphate↗
PubMed1990

Integration of lipid metabolism in the mammary gland and adipose tissue by prolactin during lactation.

Prolactin deficiency, induced by bromocryptine treatment, brought about reciprocal changes in the ability of adipocytes and acini isolated from lactating rats to synthesize lipids. The capacity to synthesize fatty acids and phospholipids decreased in the mammary gland and increased in adipocytes by bromocryptine treatment. In the mammary gland, the maximum potential activity of the pentose shunt as well as the specific activities of the pathway dehydrogenases were significantly reduced by bromocryptine treatment. Simultaneously, adipose tissue increased its lipogenic capacity but neither the maximum potential of the shunt nor the specific activities of the pentose phosphate shunt dehydrogenases were significantly changed with respect to the control lactating rats. Thus, a differential regulatory mechanism(s) of the pentose phosphate shunt activity appears to operate in these two tissues. Adipocytes from lactating rats showed a poor responsiveness to insulin in terms of lipid synthesis from glucose. In contrast, in adipocytes from bromocryptine treated rats insulin was able to increase lipid synthesis (105%). Sheep prolactin administration 'in vivo' partially reversed the effects of bromocryptine. These data suggest that prolactin mediates adipocytes resistance to insulin during lactation. Phospholipid synthesis, as occurred in fatty acid synthesis, is increased in adipose tissue and decreased in mammary gland by bromocryptine treatment. However, alpha 1-adrenergic stimulation increases phosphatidylinositol turnover to about the same percentages in both mammary gland acini and adipocytes from lactating rats independently of bromocryptine treatment.

Adipose Tissue↗
PubMed1990

Some aspects of metabolic adaptations in lipid metabolism during starvation are mimicked by epinephrine in rat adipocytes.

1. The effects of fasting on the neutral lipid synthesis to insulin and/or epinephrine in isolated fat cells have been examined using [1-14C]glucose. 2. The ability of adipocytes from starved rats to synthesize fatty acids from both labeled substrates was markedly diminished compared to adipocytes from control rats. 3. The response of lipogenic stimulation to insulin at all concentrations tested was greatly diminished in adipocytes from 24 hr starved rats. 4. [1-14C]glucose utilization rates in the absence or in the presence of insulin were not significantly different in adipocytes from 24 hr starved rats as compared with control adipocytes, although basal and insulin stimulated glyceride-glycerol synthesis were significantly higher in starved adipocytes. 5. Epinephrine acutely inhibited [1-14C]acetate incorporation into fatty acids for insulin-stimulated lipogenesis in control adipocytes, in contrast, this lipolytic agent strongly increased [1-14C]glucose conversion to triacylglycerols. 6. In both cases, the differences in lipid synthesis capacities found in both nutritional states were abolished by epinephrine.

Acetates↗
PubMed1990

Ag-NOR proteins and rDNA transcriptional activity in plant cells.

In this work we used Allium cepa root meristem cells in actively growing conditions and under treatment with the protein synthesis inhibitors cycloheximide (CHM) and puromycin. Morphological and quantitative results indicate that these drugs induce dramatic alterations in nucleolar structure reflected by a decrease of nucleolar size, much more evident under treatment with CHM, and by segregation of its main components. Quantitative analysis shows a decrease in NOR-silver staining after treatment with CHM, whereas in cells treated with puromycin NOR-silver staining remains constant. Our results reveal a decrease in the Ag-NOR proteins under conditions of diminished cell activity, suggesting a direct relationship between the quantity of Ag-NOR proteins and transcriptional activity. Using two-dimensional gel electrophoresis and NOR-silver staining in gels, we have characterized some proteins corresponding to molecular weights of 28 and 31 KD and pI of approximately 5.2. After treatment with CHM, reactivity of these proteins against NOR-silver staining is diminished. By means of a morphological study, analysis of NOR-silver staining, and of anti-DNA and RNAse-gold labeling, we have tried an approach to the nucleolar organization in plant cells. Our results suggest that the fibrillar component shows a reticular distribution where fibrillar centers, as described in animal cells, are not distinguished.

Allium↗
PubMed1989

Regulation of lipid metabolism by dipyridamole and adenosine antagonists in rat adipocytes.

1. Acute effects of dipyridamole, an inhibitor of adenosine transport, direct activators of adenylate cyclase and thirteen adenosine antagonist analogs on fatty acid synthesis have been examined in terms of the control of [1-14C]acetate incorporation into labeled fatty acids in the presence of glucose. 2. This monosaccharide acts as a stimulator of lipogenesis by generating NADPH for the lipid synthesis. 3. The relationship between lipogenesis and lipolysis was compared with a variety of adenylate cyclase stimulators. 4. The data obtained reveals that dipyridamole potentiated the inhibitory or stimulatory effects of isoproterenol and forskolin on lipogenesis and on lipolysis, respectively. 5. In these cases the data show that it exists an inverse relationship between lipogenesis and lipolysis. 6. Dipyridamole and methylxanthine analogs only moderately affect the rate of lipolysis whereas its effects are more potent on lipogenesis and lend further support to the hypothesis that dipyridamole antagonize adenosine actions as well as methyl xanthines. 7. These results suggest that dipyridamole and adenosine antagonists alter lipogenesis independently of the lipolytic process and that it exists an inverse relationship between lipogenesis and lipolysis under some conditions whereas there are not under others.

Adenosine↗
PubMed1988

Sperm tail differentiation in the nudibranch mollusc Hypselodoris tricolor (Gastropoda, Opisthobranchia).

The sperm axoneme of Hypselodoris tricolor forms from a single centriole that is located initially beneath the plasma membrane and then migrates to the nuclear surface. A conspicuous centriolar adjunct-like formation is present in the neck of midspermatids, but it becomes very reduced at the end of spermiogenesis. In spermatocyte and spermatid mitochondria, intracristal bodies originate from the accumulation of a dense material in some cristae. From our observations and foregoing reports, it may be concluded that the process of sperm tail differentiation in opisthobranchs resembles that in pulmonates, whereas it differs in many respects from that occurring in prosobranchs. The appearance of intracristal bodies in modified mitochondria seems to be a special feature of spermatogenesis in the opisthobranchs that does not occur in the two other groups of gastropod molluscs.

Animals↗
PubMed1988

Silver staining of the nucleolar organizer regions (NORs) in semithin Lowicryl sections.

The one-step silver technique was applied to semithin Lowicryl sections of root meristem cells of Allium cepa and a human tumor cell line (TG cells). In vegetal cells, after 5 min of staining reaction, the Ag-NOR proteins formed ring-shaped structures peripherally within the nucleolus. In animal cells silver granules were distributed over the entire nucleolus. The specificity of the staining reaction was increased by incubation of the sections in NH4Cl and Schiff's reagent prior to Ag-NOR silver staining.

Allium↗
PubMed1987

Metabolic antagonism between insulin action and activators of adenylate cyclase in rat fat cells.

1. Short-term effects of lipolytic agents in the absence or in the presence of insulin on fatty acid biosynthesis have been examined, in terms of the control rate of [1-14C]acetate incorporation into labeled fatty acids in the presence of glucose, as stimulator of lipogenesis by generating NADPH for the process. 2. The relationship between lipogenesis and lipolysis in the absence or in the presence of insulin was compared with a variety of adenylate cyclase activators. 3. The data obtained reveal that a reciprocal relationship exists between lipogenesis and lipolysis. 4. The changes in the activity of hexose monophosphate shunt produced by activation or inhibition of lipogenic process has been studied. 5. The regulation of the hexose monophosphate shunt activity mainly by the intracellular fatty acyl-CoA concentration and NADPH/NADP ratio is discussed.

1-Methyl-3-isobutylxanthine↗