Nuclear phosphoinositide signalling enzyme in human B lymphoid cells.

The modulation of phosphoinositidase C (PIG) 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 phos-phatidyl-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 Daudi cells selected for the resistance to the antiproliferative action of interferon alpha but no modulation of the enzyme has 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 lymphoma cells is mediated by a possible recruitment of nuclear PIC beta 1 expression.