Binding of GPI-PLD-treated DAF to the surface of Schistosoma mansoni schistosomula.
Decay accelerating factor (DAF,CD55) is a 70-kDa glycosylphosphatidylinositol (GPI)-anchored protein that protects human erythrocytes (HuE) from complement-mediated damage by regulation of the C3-convertase. Purified human DAF can be incorporated into sheep red blood cell (SRBC) membrane and confer complement resistance on these DAF-deficient cells. Here, we demonstrate that normal HuE or their stroma (HuES) incubated at 37 degrees C for 24 h release soluble DAF in a biologically active form into the culture medium. This soluble DAF neither inserts into SRBC plasma membranes nor presents the cross-reacting determinant (CRD) characteristic of the hydrolysis by phosphatidylinositol-specific phospholipases C (PI-PLC) but binds to schistosomula of S. mansoni protecting them from antibody-mediated complement-dependent damage. To study the binding of DAF to schistosomula in vitro, we have used purified human DAF labeled with 125I(125I-DAF), intact or treated with either PI-PLC or GPI-PLD (glycosylphosphatidylinositol-specific phospholipase D). We have found that GPI-PLD-treated DAF binds to the surface of parasites more readily than intact or PI-PLC-treated DAF. Immunoprecipitation of the samples with a monoclonal anti-human DAF antibody (IA10) revealed that schistosomula incubated with GPI-PLD-treated 125I-DAF emit a stronger signal than their counterparts. This result indicates that the surface of schistosomula is capable of acquiring GPI-PLD-treated DAF more effectively than intact or PI-PLC-treated molecules.
Carvalho
E M
EM
Departamento de Bioquímica-Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil.
Metz
C N
CN
Davitz
M A
MA
Ramalho-Pinto
F J
FJ
D000818:Animals; D015703:Antigens, CD / Q000494:pharmacology; D018958:CD55 Antigens; D006801:Humans; D008562:Membrane Glycoproteins / Q000494:pharmacology; D010739:Phospholipase D / Q000187:drug effects / Q000378:metabolism*; D012550:Schistosoma mansoni / Q000378:metabolism*
D015703:Antigens, CD; D018958:CD55 Antigens; D008562:Membrane Glycoproteins; D010739:Phospholipase D; C065017:glycoprotein phospholipase D