ROLE OF PHOSPHOLIPIDS CONTAINING DOCOSAHEXAENOYL CHAINS IN MODULATING THE ACTIVITY OF PROTEIN-KINASE-C

It is known that the phospholipids of the brain cells of fish are altered during cold adaptation, In particular, the l-monounsaturated 2-polyunsaturated phosphatidylethanolamines (PEs) increase 2- to 3-fold upon adaptation to cold, One of the most striking changes is in the 18:1/22:6 species of PE. We determined how this lipid affected the bilayer-to-hexagonal-phase transition temperature of 16:1/16:1 PE, We found that it was more effective in lowering this transition temperature than were other, less unsaturated, PE species, In addition, it was not simply the presence of the 18:1/22:6 acyl chains which caused this effect, since the 18:1/22:6 species of phosphatidylcholine had the opposite effect on this transition temperature. Zwitterionic substances that lo,ver the bilayer-to-hexagonal-phase transition temperature often cause an increase in the activity of protein kinase C (PKC), Indeed, the 18:1/22:6 PE caused an increase in the rate of histone phosphorylation by PKC which was greater than that caused by other, less unsaturated, PEs, The 18:1/22:6 phosphatidylcholine had no effect on this enzyme, The stimulation of the activity of PKC by the 18:1/22:6 PE is a consequence of this lipid's increasing the partitioning of PKC to the membrane.