Expression and function of an IgE-binding animal lectin (epsilon BP) in mast cells.
epsilon BP (IgE-binding protein) is a 31,000 M(r) protein originally identified in rat basophilic leukemia (RBL) cells. The protein is composed of two domains with the amino-terminal domain containing a highly conserved repetitive sequence and the carboxyl-terminal domain containing consensus sequences shared by other beta-galactoside-binding soluble lectins. The protein has wide tissue distribution, is found on cell surfaces and in extracellular milieu. By combined efforts from several research groups including ours a multifunctional nature of this lectin began to emerge. This review emphasizes the following characteristics of epsilon BP: (i) epsilon BP is secreted by cells such as macrophages; (ii) like many other lectins, epsilon BP functions at least bivalently; (iii) epsilon BP has specificity for distinct oligosaccharide structures that have a terminal galactose not masked by sialic acids; and (iv) in addition to binding IgE, epsilon BP binds to surfaces of various cell types via lectin-carbohydrate interaction. Importantly, epsilon BP binds to the IgE receptor on mast cells. We propose that epsilon BP can function as a modulatory protein on various cells by cross-linking critical cell surface glycoproteins. The proposed action of epsilon BP on mast cells is presented as a model.
Liu
F T
FT
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037.
Frigeri
L G
LG
Gritzmacher
C A
CA
Hsu
D K
DK
Robertson
M W
MW
Zuberi
R I
RI
D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D001665:Binding Sites; D004591:Electrophoresis, Polyacrylamide Gel; D037502:Galectin 3; D037102:Lectins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D008264:Macrophages / Q000276:immunology; D008407:Mast Cells / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017455:Receptors, IgE / Q000378:metabolism*
D000943:Antigens, Differentiation; D037502:Galectin 3; D037102:Lectins; D008562:Membrane Glycoproteins; D017455:Receptors, IgE