Calcium-dependent translocation of cytosolic phospholipase A2 in pancreatic beta-cells.

Cytosolic phospholipase A(2)(cPLA(2)), an enzyme responsible for the generation of arachidonic acid, is located in the cytosolic compartment in most tissues and it translocates to membrane compartments when activated. We found that cPLA(2) distribution in pancreatic beta-cells is different from that of most other mammalian cells: it is evenly distributed throughout the beta-cell, in both cytoplasmic and nuclear compartments. Agents that increased intracellular Ca(2+) in the MIN6 beta-cell line also stimulated a redistribution of cPLA(2) immunoreactivity such that the majority of the enzyme moved from the nucleus to the cytoplasm. The time course of events was compatible with the elevation in Ca(2+) being responsible for translocation of cPLA(2). These observations suggest that cPLA(2) may be compartmentalised in unstimulated beta-cells, perhaps to limit its access to substrate prior to elevations in intracellular Ca(2+).