Lymphoblastoid cell adhesion mediated by a dimeric and polymeric endogenous beta-galactoside-binding lectin (galaptin).
Glutaraldehyde-polymerized human splenic galaptin, a beta-galactoside-binding lectin, was demonstrated to have enhanced hemagglutinating and asialofetuin binding activity relative to native dimeric galaptin when these lectins were present in solution. The polymerized lectin consisted primarily of 2-, 4- and 12-membered species after reductive alkylation. Both forms of galaptin bound, at 4 degrees C, to saturable B lymphoblastoid cell surface receptors. Estimates obtained by Scatchard analyses, with the binding data expressed in terms of 14.5 kDa subunit molarity, were 5 x 10(7) binding sites/cell with affinity constant Ka = 2.2 x 10(5) M for dimeric galaptin and 17 x 10(7) binding sites/cell with Ka = 3.4 x 10(5) M-1 for polymeric galaptin. Both forms of galaptin adsorbed to polystyrene with high efficiency; however, only plastic-adsorbed polymeric galaptin mediated adhesion of lymphoblastoid cells. Cell adhesion was inhibited by lactose. Plastic-adsorbed polymeric galaptin bound asialofetuin more efficiently than dimeric galaptin. Asialofetuin binding was inhibited 65% and 30-50% by lactose for plastic-adsorbed polymeric and dimeric galaptin, respectively. Native fetuin bound to the adsorbed dimeric galaptin in a lactose-insensitive manner. These data indicate that cell surface receptor-galaptin interaction is carbohydrate specific whereas polystyrene-adsorbed galaptin may demonstrate protein-protein interactions with soluble ligands.
Ahmed
H
H
Department of Surgical Oncology, Roswell Park Cancer Institute, Buffallo, NY 14263.
Sharma
A
A
DiCioccio
R A
RA
Allen
H J
HJ
D001212:Asialoglycoproteins / Q000378:metabolism; D001704:Biopolymers; D015815:Cell Adhesion Molecules / Q000502:physiology*; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D060748:Fetuins; D037161:Galectins; D006388:Hemagglutinins / Q000502:physiology*; D006801:Humans; D008214:Lymphocytes / Q000502:physiology*; D011485:Protein Binding; D000509:alpha-Fetoproteins / Q000378:metabolism
D001212:Asialoglycoproteins; D001704:Biopolymers; D015815:Cell Adhesion Molecules; D060748:Fetuins; D037161:Galectins; D006388:Hemagglutinins; D000509:alpha-Fetoproteins; C017029:asialofetuin