The role of hydrophobic interactions in the phospholipid-dependent activation of protein kinase C.
The effects of hydrophobic interaction on the activation of Ca2+-stimulated phospholipid-dependent protein kinase (protein kinase C), isolated from mouse brain, by phosphatidylserine (PS) and diacylglycerol (DAG) or phorbol 12-myristate 13-acetate were studied. To maintain bilayer structure during assay conditions, phosphatidylcholine was added to the PS vesicles. The vesicular structure of all types of PS was confirmed by freeze-fracture electron microscopy. The PS-dependent activation of purified protein kinase C from mouse brain is affected by the fatty acid composition of PS: an inverse relationship between the unsaturation index of PS (isolated from bovine heart, bovine spinal cord or bovine brain) and the ability to activate protein kinase C was demonstrated. In highly saturated PS lipid dispersions, only slight additional activation of protein kinase C by DAG was found, in contrast with highly unsaturated PS lipid dispersion, where DAG increased protein kinase C activity by 2-3-fold at optimal PS concentrations. We quantified the formation of the protein kinase C-Ca2+-PS-phorbol ester complex by using [3H]phorbol 12,13-dibutyrate [( 3H]PDBu). The efficiency of complex-formation, determined as the amount of [3H]PDBu bound, is not affected by variations in the hydrophobic part of PS. These results indicate a role of the hydrophobic part of the activating phospholipid in the activation mechanism of protein kinase C and in the action of cofactors.
Snoek
G T
GT
Hubrecht Laboratory, Netherlands Institute of Developmental Biology, Utrecht.
Feijen
A
A
Hage
W J
WJ
van Rotterdam
W
W
de Laat
S W
SW
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000032:analysis; D008081:Liposomes / Q000378:metabolism; D046911:Macromolecular Substances; D051379:Mice; D008854:Microscopy, Electron; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D005227:Fatty Acids; D008081:Liposomes; D046911:Macromolecular Substances; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium