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

Abstract

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.

• Authors: T Suzuki, R Sadasivan, T Saito-Taki, D J Stechschulte, L Balentine, G M Helmkamp Jr
• Journal: Biochemistry (Biochemistry) Vol. 19 Issue 26 Pg. 6037-44 (Dec 23 1980) ISSN: 0006-2960 [Print] United States
• PMID: 6970591 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Amino Acids
• Immunoglobulin G
• Receptors, Fc
• Phospholipases
• Phospholipases A
• Phospholipases A2

Topics

• 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)