Nuclear Phosphoinositide Signalling Enzyme in Human B Lymphoid Cells.

Abstract

ABSTRACT. The modulation of phosphoinositidase C (PIC) beta activity upon interferon treatment in Burkitt lymphoma cells (Daudi) and its localization and expression have been analyzed by Western blotting, immunocytochemical and immunoelectronmicroscopy analysis. Results have disclosed an early increase of phosphatidyl-inositol-bisphosphate (PIP2) hydrolysis at nuclear level upon interferon (IFN) treatment paralleled by the evidence of an increase of PIC beta 1 expression. PIC beta 1 expression has been detected in the nuclear compartment also in a clone of Daudicells selected for the resistance to the antiproliferative action of interferon alpha but no modulation of the enzymehas been detected upon interferon treatment. Since no changes in terms of PIP2 hydrolysis have been found at nuclear level in this selected line, we suggest that the antiproliferative action of interferon on Burkitt lymphomacells is mediated by a possible recruitment of nuclear PIC beta 1 expression.The control and modulation of cell growth by the interaction of specific agents with cell surface receptors is an intriguing phenomenon certainly driven by cascades of several molecular events able to transduce biological signals to the cell nucleus. Such a cascade would presumably activate a process of redirection of nuclear genetic programs leading to the control of given cellular functions like the control of cell growth (12,17,20,28,29).Amongthe pathways involved in the signal transduction system from the plasma membraneto the nucleus and inside the nucleus itself, inositol lipids have been recently shown to be possible regulatory molecules in the control of signals related to cell metabolism (2, ll, 13, 15, 16, 18, 21, 26). This signalling system generating second messengers has been recently found involved mainly at nuclear level in the metabolic events related to the growth inhibitory action of interferon alpha in Daudi lymphoma cells (5, 10,22,27). The response of the cytoplasmic compartment to interferon treatment in terms of inositol lipids, in fact, has been reported to display different features compared to the nucleus suggesting the recruitment of different routes at plasma membrane and nuclear level (7). These results have prompted the question of the intracellular localization and distribution of phosphoinositidase C in Daudi lymphomacells and the modulation, if any, of its expression upon inter- plemented with 10% fetal calf serum, glutamine, penicillinstreptomycin and neomycin. Cells from Daudi resistant clones were continuously maintained in culture in the presence of recombinant interferon alpha 2A (La Roche). The resistant phenotype was stable without any interferon treatment for up to six culture doublings and resistant cells underwent at least three doublings without interferon prior to use in experiments. Viability was determined by the trypan blue exclusion test. R interferon alpha 2A treatment of the cells (500 I.U. /ml) was performed for different intervals up to 24 hr. Cellfractionation. Cells were resuspended in a bu...

Nuclear inositides: inconsistent consistencies

“…This type of experiment has been carried out using nuclei from various tissues and cell types with results that are essentially the same as the original data from Smith and Wells [54][55][56][57][58][59][60][61]. A number of studies have taken these experiments further, in order to define whether this nuclear pathway is a target of regulation by growth factors and cellular processes [55,57,58,[62][63][64][65][66][67]. Nuclei isolated from control cells, or from those differentiated down an erythroid pathway, showed differences in their labelling patterns after incubation with 32P-ATP.…”

Immunocytochemical Detection of Phosphatidylinositol 3 Kinase in Burkitt Lymphoma Cells.

“…Such a signalling system was found also involved in the downstream metabolic events related to the growth inhibitory action of R interferon a in Daudi lymphomacells (5)(6)(7)(8)(9). Indeed, results on the expression and the activity of different isoforms of phosphatidylinositol phospholipase C (PI-PLC), the enzyme responsible for the hydrolysis of phosphatidylinositolbisphosphate (PIP2) producing the well known second messengers diacylglycerol (DAG) and inositoltriphosphate (IP3), evidenced a peculiar involvement of different PLCisoforms in the cytoplasmic and nuclear compartments in response to interferon treatment (10-1 1).…”