Studies of Fc gamma receptors of human B lymphocytes: phospholipase A2 activity of Fc gamma receptors

The presence of phospholipase A2 activity within human B cell Fc gamma receptors was investigated. Lysate produced by detergent treatment of chronic lymphocytic leukemia cells that had 1% of the cells surface radioiodinated was subjected to affinity chromatography by using either rac-1-(9-carboxynon...

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Bibliographic Details
Published in:Biochemistry (Easton) 1980-12, Vol.19 (26), p.6037-6044
Main Authors: Suzuki, T, Sadasivan, R, Saito-Taki, T, Stechschulte, D J, Balentine, L, Helmkamp, Jr, G M
Format: Article
Language:English
Subjects:
Amino Acids - analysis
B-Lymphocytes - enzymology
Cell Membrane - enzymology
Chromatography, Affinity
Humans
Immunoglobulin G - metabolism
Isoelectric Focusing
Leukemia, Lymphoid - enzymology
Phospholipases - metabolism
Phospholipases A - metabolism
Phospholipases A2
Receptors, Fc - metabolism
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Summary:The presence of phospholipase A2 activity within human B cell Fc gamma receptors was investigated. Lysate produced by detergent treatment of chronic lymphocytic leukemia cells that had 1% of the cells surface radioiodinated was subjected to affinity chromatography by using either rac-1-(9-carboxynonyl)-2-hexadecylglycero-3-phosphorylcholine-Sepharose (PC-Sepharose) or heat-aggregated human IgG-Sepharose 4B conjugate (IgG-Sepharose). The materials eluted from both adsorbants by ethylenediaminetetraacetate- or urea-containing buffer were further purified by gel filtration and isoelectric focusing in the presence of 6 M urea. Both isolated PC- and IgG-binding materials were homogeneous, when judged by gel filtration and isoelectric focusing, and had identical isoelectric points (pI = 6.5), peptide maps, and amino acid compositions. Furthermore, both preparations catalyzed equally the hydrolysis of phosphatidylcholine to release fatty acid from the 2 position. Optimal enzymatic activity depended on the presence of Ca2+, was maximal at pH 9.5, and was augmented by Fc gamma fragments. Both preparations specifically bound to the Fc portion of IgG and inhibited human antibody-coated erythrocyte rosette formation by peripheral mononuclear cells. Our data thus demonstrate the identity of PC- and IgG-binding materials and suggest that a functional activity of the human B cell Fc gamma receptor is the generation of phospholipase A2 activity within the plasma membrane.
ISSN:0006-2960
DOI:10.1021/bi00567a014