The presence of a secretory phospholipase A2 in the nuclei of neuronal and glial cells of rat brain cortex

Confocal immunofluorescence analysis indicated a relatively high localization of group V secretory phospholipase A2 (GV) in the nuclei of cultured PC12 and U251 astrocytoma cells. Here, we report the biochemical evidence for the presence of a secretory PLA2 in the nuclei of neuronal and glial cells from rat brain cortex. Enzymic activity was determined using [3H]oleate labelled Escherichia coli membranes in intact nuclei and in their soluble fractions in which the specific activity was significantly more elevated. The treatment of soluble nuclear fractions with inhibitors of cytosolic Ca2+-dependent or Ca2+-independent phospholipases A2 was ineffective whereas DTT or Indoxam, a specific inhibitor of all isoforms of sPLA2, abolished enzyme activity. The enzyme was identified as group V secretory phospholipase A2 (GV) by Western blot analysis and its nucleoplasmic localization was demonstrated by CLSM.