Nuclear diacylglycerol and PKC-β_II import at G2/M (p. 983)

In G2/M phase, PKC-β_II translocates to the nucleus, where it is proposed to stimulate disassembly of the nuclear lamina by phosphorylating lamin B₁. But PKC-β_II is just one of a host of cellular PKC isoforms. How do cells selectively translocate PKC-β_II? Janet Lord and co-workers have addressed this question by analysing the levels of potential PKC-activating lipids in nuclei during the cell cycle; they used centrifugal elutriation to isolate cells at different stages of the cell cycle and thereby avoid the use of cell cycle inhibitors. The authors find that nuclear translocation of PKC-β_II correlates with an increase in the levels of nuclear diacylglycerol - in particular the tetraunsaturated species 1-stearoyl,2-arachidonyl glycerol (SAG). They show that SAG potently activates PKC-α and PKC-β_II but not the novel isoform PKC-δ. Lord and co-workers propose that generation of nuclear SAG at G2/M facilitates association of PKC-β_II with the nuclear membrane - perhaps as part of a general mechanism for differential control of PKC signalling by distinct forms of diacylglycerol.