Production and protein kinase C activation of diacylglycerols containing polymethylene-interrupted PUFA

Sciadonic acid (20:3, delta-5c,11 c,14c) is a polymethylene-interrupted PUFA (PMI-PUFA) that is present in conifer seeds and known to be incorporated into animal cells and to accumulate in membrane PI as a substitute for arachidonate. In this study, we investigated whether PI having sciadonate could serve as source of DAG that could activate protein kinase C (PKC). When Swiss 3T3 cells cultured with sciadonic acid were stimulated with 100 nM of bombesin, 1-stearoyl-2-sciadonoyl-glycerol (G) and 1-stearoyl-2-arachidonoyl-G were produced. The net increments of these two molecular species of DAG reflected the levels of the two molecular species in the PI in the cells. When cells cultured with juniperonic acid (20:4, delta-5c,11c,14c,17c) were stimulated, 1-stearoyl-2-juniperonoyl-G was produced in proportion to the level of this molecular species in PI in the cells. We also examined PKC activation by synthetic DAG using a partially purified PKC fraction from rat brain and found that both 1-stearoyl-2-sciadonoyl-G and 1-stearoyl-2-juniperonoyl-G could activate PKC comparably to 1 -stearoyl-2-arachidonoyl-G. These results indicate that 1-stearoyl-PI having these C20 PMI-PUFA residues can serve as sources of potential signaling molecules.