stearates and 9-10-tetradecenol

We studied the effects of membrane modulation on the interaction of Plasmodium falciparum rhoptry proteins of 140/130/110 kDa (Rhop-H) with human and mouse erythrocytes. Cells treated with 2-(2-methoxyethoxy)ethyl-8-(cis-2-n-octylcyclopropyl)octanoate, myristoleyl alcohol, and proteins extracted with sublytic concentrations of membrane solubilizing detergents were used in erythrocyte binding assays. Protein binding was evaluated by immunoblotting using Rhop-H- and SERA-specific antisera, 1B9, K15, and 5E3, respectively. Protein binding to liposomes prepared with dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) or dilauroyl-L-alpha-phosphatidylcholine (DLPC) was also examined. Our results show that erythrocyte membrane modulation markedly enhanced direct Rhop-H binding to intact human erythrocytes. Binding of SERA to intact human erythrocytes appeared unaffected. Both DPPC and DLPC liposomes had similar Rhop-H and SERA protein binding activities. However, binding to DLPC liposomes was reduced. Rhop-H and SERA extracted with the detergents octanoyl-N-methylglucamide, decanoyl-N-methylglucamide, sodium deoxycholate, and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate bound directly to intact human erythrocytes, probably by partitioning hydrophobically into the membranes. Sodium carbonate treatment demonstrated a nonintegral association of Rhop-H with the erythrocyte membrane during invasion. Membrane modulation may expose cryptic phospholipid binding sites in the bilayer.

Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Detergents; Erythrocyte Membrane; Fatty Alcohols; Humans; Immunoblotting; Liposomes; Mice; Neuraminidase; Plasmodium falciparum; Protein Binding; Protozoan Proteins; Stearates; Subcellular Fractions; Trypsin

To evaluate the effect of membrane lipid acyl-chain packing on the efficiency of cell lysis by complement, we have studied membrane modulation by 2-(2-methoxy)-ethoxyethyl-8-(cis-2-n-octylcyclopropyl)-octanoate (A2C) and by myristoleyl alcohol, the cis isomer of a C14:1 aliphatic alcohol. These substances are known to increase the membrane lipid disorder by virtue of the bend in their acyl chains, which is believed to loosen the phospholipid acyl-chain packing. We have found that both of these compounds markedly enhance the lysis of erythrocytes by the terminal complement proteins C5b-9. The enhancing effect by A2C is operative in the formation of erythrocytes carrying complement components C5b, C6, and C7, as well as in the subsequent reactions with complement components C8 and C9. We have also found that A2C-treated erythrocytes bind C5b6 to a measurable extent, whereas untreated erythrocytes do not. We attribute this to a shift in the partition equilibrium of C5b6 toward membrane association, which would improve lytic efficiency. The increase of membrane lipid disorder by these agents would also be expected to increase insertion of hydrophobic peptides from C7, C8, and C9, with consequent gain in lytic efficiency. Treatment of erythrocytes with sublytic doses of NaDodSO4, or Triton X-100 did not enhance lysis by C5b-9 appreciably, suggesting that enhancement of lysis by C5b-9 is not a general property of amphiphiles.

Topics: Complement C5; Complement C6; Complement C7; Complement C8; Complement C9; Erythrocyte Membrane; Erythrocytes; Fatty Alcohols; Humans; Polyethylene Glycols; Sodium Dodecyl Sulfate; Stearates; Stearic Acids; Stimulation, Chemical