Contributions to maxima in protein kinase C activation.
In many lipid systems, the activity of protein kinase C (PKC) exhibits a peak followed by a decline as the mol % of one component is increased. In these systems, an increase in one lipid component is always at the expense of another or accompanied by a change in total lipid concentration. Here we report that in saturated phosphatidylserine (PS)/phosphatidylcholine (PC)/diacylglycerol (DAG) mixtures, increasing PS or DAG at the expense of PC revealed an optimal mol % PS, dependent on mol % DAG, with higher mol % PS diminishing activity. The decrease at high mol % PS is probably not attributable simply to more gel-phase lipid due to the higher melting temperature of saturated PS versus PC because a similar peak in activity occurred in unsaturated lipid systems. Increasing the total lipid concentration at suboptimal mol % PS provided the same activity as higher mol % PS at lower total lipid concentration. However, at optimal mol % PS, activity increased and then decreased as a function of total lipid concentration. PKC autophosphorylation also exhibited an optimum as a function of mol % PS, and increasing the PKC concentration increased the mol % PS at which activity decreased, both for autophosphorylation and for heterologous phosphorylation. Formation of two-dimensional crystals of PKC on lipid monolayers also exhibited a peak as a function of mol % PS, and the unit cell size of the crystals formed shifts from 50 x 50 A at low mol % PS to 75 x 75 A at higher PS. Collectively, these data suggest the existence of optimal lipid compositions for PKC activation, with increased quantity of these domains serving to dilute out enzyme-substrate aggregates and/or enzyme-enzyme aggregates on the lipid surface.
Sando
J J
JJ
Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA. jjs@virginia.edu
Chertihin
O I
OI
Owens
J M
JM
Kretsinger
R H
RH
D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D011493:Protein Kinase C / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018411:Spodoptera; D013379:Substrate Specificity; D014162:Transfection; D014494:Unithiol / Q000494:pharmacology
D004075:Diglycerides; D007527:Isoenzymes; D008081:Liposomes; D009842:Oligopeptides; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D011994:Recombinant Proteins; D014494:Unithiol; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta