Dependence of the surface expression of the glycolipid cerebroside sulfate on its lipid environment: comparison of sphingomyelin and phosphatidylcholine.
The influence of the membrane lipid environment on the reactivity with antibody of the acidic glycolipid cerebroside sulfate (CBS) was examined by using a spin membrane immunoassay. Fewer antibodies in a polyclonal anti-CBS antiserum recognized the antigen in a bovine brain sphingomyelin/cholesterol (SM/CHOL) environment than in dipalmitoylphosphatidylcholine/cholesterol (DPPC/CHOL). Changes in the CBS ceramide group appeared to have less influence on antibody recognition of CBS in SM/CHOL than in DPPC/CHOL [Crook et al. (1986) Biochemistry 25, 7488-7494]. Although the fatty acid chain length of phosphatidylcholine strongly influences CBS recognition, the fatty acid chain length of sphingomyelin had only a moderate effect on CBS recognition and did not account for the decreased recognition in SM compared to in DPPC. Inhibition studies revealed that the antibodies which recognize CBS in SM/CHOL (S antibodies) form a population distinct from those which recognize CBS in DPPC/CHOL (P antibodies). The specificity of the P and S antibodies was examined further by comparing the efficacy of various substances, which share chemical features with the components of CBS in a SM/CHOL or DPPC/CHOL environment, to inhibit lysis of liposomes containing CBS. Intact CBS, cholesterol, and a phosphocholine lipid, at certain antigen densities, were required for optimal recognition of the antigen, especially by the P antibodies, suggesting that a complex of all three lipids in a multivalent array may be recognized by these antibodies. The S antibodies may recognize a smaller complex or monomers of CBS.(ABSTRACT TRUNCATED AT 250 WORDS)
Stewart
R J
RJ
Department of Clinical Biochemistry, University of Toronto, Ontario, Canada.
Boggs
J M
JM
D000818:Animals; D000906:Antibodies / Q000276:immunology; D000941:Antigens / Q000276:immunology; D001667:Binding, Competitive; D002417:Cattle; D002554:Cerebrosides / Q000276:immunology*; D002784:Cholesterol; D008081:Liposomes; D010713:Phosphatidylcholines / Q000276:immunology; D010743:Phospholipids / Q000276:immunology; D013109:Sphingomyelins / Q000276:immunology; D013431:Sulfates / Q000378:metabolism*
D000906:Antibodies; D000941:Antigens; D002554:Cerebrosides; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D013109:Sphingomyelins; D013431:Sulfates; D002784:Cholesterol