Evidence for nuclear phosphoinositidase C activity in the antiproliferative signals produced by interferon in Burkitt lymphoma cells.

The influence of interferon alpha on nuclear phosphoinositidase C (PIC) in Daudi cells has been analysed. Results showed an early increase of PIC activity detectable within 90 min of interferon treatment concomitant with an increase of diacylglycerol (DAG) levels. Since the interferon-induced DAG production is not modified by the addition of propranolol, a compound known to inhibit production of DAG from phosphatidylcholine hydrolysis, it is suggested that the interferon antiproliferative signal is transduced into the nucleus via the inositol lipid pathway. A parallel analysis performed on intact cells showed a rapid inhibition of PIC activity accompanied by an increase of DAG level thus suggesting that interferon-generated signals at plasma-membrane level use pathways different from that of inositol lipids. A selected clone of Daudi cells resistant to interferon action provided a control for specificity of results.