Phospholipid metabolism in Plasmodium-infected erythrocytes: guidelines for further studies using radioactive precursor incorporation.
The biosynthesis of phospholipids is extensive in Plasmodium knowlesi-infected simian erythrocytes due to the synthesis of membranes by this single-cell eukaryote in a host erythrocyte devoid of any pathway for lipid biosynthesis. In the present paper, we show that the incorporation of [3H]glycerol, which reflects de novo biosynthesis, is better studied at 300 microM-1 mM than at the trace doses, since this non-physiological precursor does not modify the amount of phosphatidylcholine biosynthesis from [3H]choline. Time-course incorporation of radioactive glycerol, oleate, lysophosphatidylcholine, choline, and inositol in RPMI 1640 medium containing nutrients for lipid synthesis showed that the optimum incubation time for phospholipid studies is 60-90 min, after which radioactive incorporation slows considerably. On the other hand, studies with [14C]serine revealed that incubation for 2-3 h is necessary for isotopic labelling of phosphatidylcholine via phosphatidylserine decarboxylation and phosphatidylethanolamine N-methylation. Incorporation of the various fatty acids into individual lipids was related to the molecular species composing each of them. Studies with [14C palmitoyl] lysophosphatidylcholine showed a very fast intracellular release of radioactive fatty acids, which indicates a potent lysophospholipase activity. Taken together, these data define the indispensable conditions for an experimental system suitable for further studies.
Vial
H J
HJ
CNRS UA 530, INSERM U 58, Montpellier, France.
Ancelin
M L
ML
Thuet
M J
MJ
Philippot
J R
JR
D000818:Animals; D002794:Choline / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism* / Q000469:parasitology; D005227:Fatty Acids / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D008252:Macaca fascicularis; D008288:Malaria / Q000097:blood*; D010743:Phospholipids / Q000096:biosynthesis*; D010961:Plasmodium / Q000254:growth & development*; D012694:Serine / Q000378:metabolism
D005227:Fatty Acids; D010743:Phospholipids; D012694:Serine; D002794:Choline; D005990:Glycerol