Monopalmitoylphosphatidylcholine incorporation into human erythrocyte ghost membranes causes protein and lipid immobilization and cholesterol depletion.
The effects of lysophosphatidylcholine (lysoPC) on human erythrocyte (RBC) ghost morphology, transmembrane protein and lipid lateral mobilities, and membrane lipid composition were studied in order to elucidate mechanisms by which lysoPC immobilizes ghost membrane components [Golan, D. E., Brown, C. S., Cianci, C. M. L., Furlong, S. T., & Caulfield, J. P. (1986) J. Cell Biol. 103, 819-828]. Under standardized conditions 1.0-1.5 micrograms/mL egg lysoPC lysed 50% of RBCs and induced, in some ghosts, the formation of large patches of wrinkled membrane. Patches exhibited complete immobilization of glycophorin and band 3 and partial immobilization of the phospholipid analogue fluorescein phosphatidylethanolamine (Fl-PE), whereas adjacent smooth membrane areas manifested only partial immobilization of proteins and no immobilization of Fl-PE. Supralytic concentrations of lysoPC induced both progressive, homogeneous wrinkling of RBC ghost membranes and concentration-dependent decreases in the lateral mobilities of glycophorin, band 3, and Fl-PE. Complete immobilization of glycophorin and band 3 occurred at 8.4 micrograms/mL lysoPC and of Fl-PE at 16.8 micrograms/mL lysoPC. Monopalmitoylphosphatidylcholine (MPPC), the major component of egg lysoPC, induced both membrane wrinkling and a concentration-dependent decrease in Fl-PE mobility, with complete immobilization at 10 micrograms/mL. Other synthetic lysoPCs did not completely immobilize Fl-PE, although some caused membrane wrinkling. MPPC was incorporated into ghost membranes with a linear dependence (r = 0.97) on MPPC concentration. Relative to total membrane lipid, the lysoPC mole fraction increased from 0.2 +/- 0.1% at 0 micrograms/mL MPPC to 25 +/- 2% at 16 micrograms/mL MPPC.(ABSTRACT TRUNCATED AT 250 WORDS)
Golan
D E
DE
Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115.
Furlong
S T
ST
Brown
C S
CS
Caulfield
J P
JP
D002784:Cholesterol / Q000097:blood*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006801:Humans; D008244:Lysophosphatidylcholines / Q000097:blood*; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000097:blood*; D008565:Membrane Proteins / Q000097:blood*; D008856:Microscopy, Fluorescence
D005452:Fluoresceins; D005456:Fluorescent Dyes; D008244:Lysophosphatidylcholines; D008563:Membrane Lipids; D008565:Membrane Proteins; C027912:fluorescein thiosemicarbazide; D002784:Cholesterol