1,720,996 research outputs found
Nuclear localization and signalling activity of inositol lipids
No full textIt has been recently shown that also the nucleus is a site for both synthesis and hydrolysis of the phosphorylated forms of phosphatidylinositol. Among the enzymes of the cycle we and others have demonstrated that phospholipase C specific for inositol lipids (PLC) is one of the main steps of the inositol lipid cycle. The PLC family and namely the type raised a noticeable interest since, because of their common COOH-terminus, it has been shown a nuclear localisation in addition to that at the plasma membrane. The autonomous intranuclear inositide cycle is endowed, besides the PLC, with conventional lipid kinases and phosphatidylinositol 3 kinase (PI 3-kinase) which plays an important role in granulocytic differentiation. The combination of morphology and molecular biology gave us the opportunity to localise the sites inside the nucleus where the cycle takes place and to understand the physiological significance of such a subcellular compartmentalisation both during cell growth and differentiation
Chromatin Phospholipids in Normal and Chronic Lymphocytic Leukemia Lymphocytes
No full textCertain phospholipids are associated with the nonhistone chromosomal proteins extracted from normal B- and chronic lymphocytic leukemia lymphocytes. The ratio of phospholipids to nonhistone chromosomal proteins was constant with the different methods used for isolating nuclei and extracting the chromatin, although the various methods allowed a different recovery of total lipids from chromatin. Three phospholipids were extractable from the nonhistone protein fraction, but their respective ratios varied in chronic lymphocytic leukemia compared to normal B-lymphocytes. The most significant variation concerns the reduction of sphingomyelin content in leukemic lymphocytes, since this prospholipid in vitro affects both DNA stability and transcription
Lipid-F1 nucleohistone interactions
No full textHigh concentrations of phospholipids determine destabilization of F1 histone-DNA complex at the weight ratios, histone:DNA, 0.8:1 and 1:1, but low concentrations cause only negligible destabilization. Cholesterol at high weight ratios has little effect on nucleohistone stability. Only linolenic acid of the fatty acids used reproduces similar changes in the thermal stability of F1 histone-DNA complex as phospholipids. The type of interaction of phospholipids with the F1 histone-DNA complex is analyzed, and the involvement of phospholipids in DNA replication in vivo is discussed
Effect of phospholipid vesicles on the activity of terminal transferase
No full textThe terminaI transferase activity is modified in the presence of
Iipid vesicles. A deep inhibitory effect takes pIace with phosphati-
dylserine and phosphatidylinositol, while some stimulation is pre-
sent with sphingomyelin and almost no effect has been detected with
phosphatidylethanolamine vesicles. These effects seem to be related
to the charge properties of the Iipid membranes.
A possible involvement of phospholipids in the mechanism of action
of the terminaI transferase is suggested
Lipid--DNA interactions. II. Phospholipids, cholesterol, glycerophosphorylcholine, spingosine and fatty acids.
No full textHigh concentrations of lecitin, phosphadylethanolamine, phosphatidyl-serine, cholesterol and lauric acid have a destabilizing effect on the DNA helix. On the contrary, lower concentrations of the same lipids produce stabilization on DNA. The stabilizing and destabilizing effects with sphingomyelin components can be mainly attributed to sphingosine and lignocerin acid components, whwreas glycerophosphorycholine probably has a minimal effect. The saturated long-chain fatty acids were capable of having a moderate destabilizing effect on DNA; however, the unsaturated fatty acids were found to be generally more stabilizing in nature. The type of bonding within the lipid-DNA interaction has been investigated and the existence of a lipid-DNA complex in vivo has been considered
In vitro phosphorylation of lamin B by protein kinase C in friend erythroleukemia. Effect of chemically induced differentiation
No full textNuclear matrix isolated from murine erythroleukemia cells (Friend cells) has been phosphorylated with gamma 32P-ATP and purified protein kinase C in order to identify specific nuclear substrates for the enzyme. HMBA has been employed to induce the cell to differentiate and to compare the changes of phosphorylation profile after erythroid differentiation. Lamin B has been found to be hyperphosphorylated by rat brain PK-C in nuclear matrix purified from uninduced cells. This difference characterizes the cells from 14 to 72 hrs of HMBA treatment and indicates that the ability of lamin B to be phosphorylated by PK-C is linked to the differentiated state. The involvement of PK-C in lamin phosphorylation might represent an early step of the signalling pathway utilized by erythroid differentiating agents to target the cell nucleus. © 1991
TNF-related apoptosis-inducing ligand (TRAIL) and erythropoiesis: a role for PKCepsilon.
No full textThe regulation of the hematopoietic stem cell pool size and the processes of cell differentiation along the hematopoietic lineages involve apoptosis. Among the different factors with a recognized activity on blood progenitor cells, TRAIL - a member of the TNF family of cytokines - has an emerging role in the modulation of normal hematopoiesis.PKC(epsilon) levels are regulated by EPO in differentiating erythroid progenitors and control the protection against the apoptogenic effect of TRAIL. EPO-induced erythroid CD34 cells are insensitive to the apoptogenic effect of TRAIL between day 0 and day 3, due to the lack of specific surface receptors expression. Death receptors appear after day 3 of differentiation and consequently erythroid cells become sensitive to TRAIL up to day 9/10, when the EPO-driven up-regulation of PKC epsilon intracellular levels inhibits the TRAIL-mediated apoptosis, via Bcl-2. In the time interval between day 3 and 9, therefore, the number of erythroid progenitors can be limited by the presence of soluble or membrane-bound TRAIL present in the bone marrow microenvironment
Nuclear proteins and chromatin ultrastructure in normal and CLL lymphocytes.
No full textHistones and non-hìstone chromosomai proteins (NHCP) of normai and CLL
Iymphocytes were characterized respectively by polyacryIamide and SDS-
poIyacryIamide eIectrophoresis.
Purified B normai and CLL, monoclonal B Iymphocytes were examined by
eIectron microscope for a quantitative evaluation of heterochromatin contento
The results indicate distinct differences between NHCP of B and CLL lympho-
cytes as well as an increase both of F3 histone and heterochromatin in CLL
Iymphocytes.
A possibie reiation between these characteristic nuc1ear features and the ac-
cumulation of immunologically incompetent Iymphocytes in the course of CLL
is suggested
Lymphocyte clones from old subjects: growing rate and functional activity.
No full textOld subjects exhibit a decline in circulating T cells and an impaired
proliferative response to mitogens, plus a relative increase in cells with NK
phenotype not associated with a concomitant increase in their cytolitic
activity.In the present study a limiting dilution assay was used to evaluate the
phenotype, the functional activity and the proliferative capacity of clones
obtained from peripheral blood lymphocytes of old and young subjects. CD5+ CD8+
clones from old people showed a significant impairment in their proliferative
capacity and a decreased lytic activity against K562 and P815-IgG cell lines
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