Modulation of functional properties of galectin-3 by monoclonal antibodies binding to the non-lectin domains.
Galectin-3 is a member of a newly defined family of animal lectins, which is composed of three domains: a small amino-terminal domain, a domain containing repeating elements, and a carboxyl-terminal domain containing the carbohydrate-recognition site. Various functions have been described or proposed for this lectin, and it appears that galectin-3 has diverse roles. Murine monoclonal antibodies (MAbs) have been generated from mice hyperimmunized with recombinant human galectin-3 or galectin-3C (the carboxyl-terminal domain), and seven MAbs have been characterized in detail. All MAbs generated against the intact galectin-3 recognize the amino-terminal region of the molecule, as demonstrated by ELISA and immunoblotting using recombinant galectin-3C and galectin-3NR, which contains the amino-terminal domain and all the repeating elements. Their epitopes were all found to be within the first 45 amino acids of galectin-3, as determined by using galectin-3 mutants with a truncated amino-terminal region. However, these MAbs were found to profoundly modulate the lectin activities of galectin-3. The MAb B2C10 inhibited (i) the binding of 125I-labeled galectin-3 to IgE coated on microtiter plates; (ii) the galectin-3's hemagglutination activity; and (iii) galectin-3-induced superoxide production by human neutrophils. Other MAbs, especially A3A12, caused marked potentiation of these activities. The results support our model that the lectin function of galectin-3 is influenced by protein homodimerization resulting from self-association of the amino-terminal region of the molecule. The potentiating activities of some MAbs are probably due to facilitation of dimerization galectin-3, and the inhibitory activity of MAb B2C10 is probably the result of its disruption of the self-association process.
Liu
F T
FT
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037-1093, USA.
Hsu
D K
DK
Zuberi
R I
RI
Hill
P N
PN
Shenhav
A
A
Kuwabara
I
I
Chen
S S
SS
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000943:Antigens, Differentiation / Q000276:immunology / Q000378:metabolism*; D001483:Base Sequence; D001666:Binding Sites, Antibody; D002462:Cell Membrane / Q000378:metabolism; D017931:DNA Primers; D000939:Epitopes / Q000378:metabolism; D037502:Galectin 3; D006386:Hemagglutination Tests; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D017931:DNA Primers; D000939:Epitopes; D037502:Galectin 3; D037102:Lectins; D007073:Immunoglobulin E