Synergistic Effects of Diacylglycerols and Fatty Acids on Membrane Structure and Protein Kinase C Activity

Abstract

The synergistic effects of diacylglycerol (DAG) and fatty acid (FA) in activating protein kinase C have been investigated by correlating their individual and combined effects on enzymatic activity and on membrane structure in phosphatidylcholine/phosphatidylserine (4:1) lipid mixtures using a combination of specific enzymatic assays and 31P and 2H NMR. Addition of DAGs and unsaturated FAs to the bilayers synergistically increased the tendency of the lipids to form nonbilayer phases with a concomitant increase in PKC activity until a maximum was achieved. Further increases in the DAG/FA concentration led to the formation of the nonbilayer lipid phases under the conditions of the PKC activity assays and correlated with decreased activity. The nonbilayer lipid phases still supported PKC activity, although with less than 50% efficiency as compared with the bilayer lipids. Long-chain saturated FA increased DAG-induced PKC activity by causing a lateral phase separation of gel (Lbeta) and liquid-crystalline (Lalpha) domains. Due to the preferential partitioning of DAGs into liquid-crystalline domains, the local DAG concentration increased in these domains, leading to an increase in PKC activity. Because a wide range of lipophilic compounds is capable of altering curvature stress, and therefore the tendency for nonbilayer phase formation in cellular membranes, these compounds would be expected to modulate PKC activity and the activities of a number of other membrane-associated enzymes that are sensitive to biophysical properties of lipid membranes.

The Novel Anticancer Drug Hydroxytriolein Inhibits Lung Cancer Cell Proliferation via a Protein Kinase Cα– and Extracellular Signal-Regulated Kinase 1/2–Dependent Mechanism

“…In this scenario, nonlamellar prone lipids promote the cytoplasmic-to-membrane translocation of PKC (Goldberg et al, 1994;Escribá et al, 1995) and therefore its activity (Epand et al, 1991;Goldberg and Zidovetzki, 1998). We show here that HTO induces PKCa cytosol to membrane translocation and that PKCa is in part responsible for the antitumor effects of HTO.…”

Characterization of the Interaction of Ingenol 3-Angelate with Protein Kinase C

“…ingenol 3-angelate could not cause the same degree of association of the C1b domain with lipid that is induced by DAG or PMA. The basis of the decrease in association of the C1b domain at high ligand concentrations is uncertain, but optimal concentrations of different activators for maximal activation have been reported previously (52,53), suggesting submaximal effects at higher ligand concentrations. It clearly does not appear to reflect a major change in the composition of the bulk lipid phase, because the incorporation of the ligand into the liposome in the absence of receptor was modest (see Fig.…”

AA/12-lipoxygenase signaling contributes to inhibitory learning in Hermissenda Type B photoreceptors

“…Among the more important indirect mechanisms are: (1) AA's stimulation of protein kinases and phosphatases (Shearman et al, 1989; Golberg and Zidovetzki, 1998), (2) AA acting as a substrate for enzymatic modification by lipoxygenases, cyclooxygenases, cytochrome P450 enzymes etc (Samuelsson et al, 1987; Marks and Furstenberger, 1999). The latter class of mechanisms has been found to be especially critical for AA's increase in K + channel activity, and decreases in the strength of synaptic transmission (Northover, 1977; Piomelli et al, 1987b; Schwartz, 1991; Amin et al, 1999; Tegeder et al, 2001).…”