Molecular mapping of functional antibody binding sites of alpha 4 integrin.
Integrin alpha 4 beta 1 is a leukocyte receptor for fibronectin and vascular cell adhesion molecule-1 (VCAM-1). It is important in inflammatory recruitment of leukocytes, lymphopoiesis, and a number of development events. Here we have mapped a panel of functional monoclonal antibodies (mAbs) recognizing the integrin alpha 4 chain, using murine/human chimeric constructs expressed in COS7 cells. We find that: 1) mAbs that induce homotypic aggregation (epitope A mAbs) map to the most N-terminal 100 amino acids of the human alpha 4 chain; 2) mAbs that block adhesion of alpha 4 beta 1 to VCAM-1 and fibronectin (epitope B mAbs) map to a 52-amino-acid region between residues 152 and 203 of human alpha 4; 3) epitope B mAbs that do or do not induce aggregation (epitope B2 and B1 mAbs, respectively) map to the same regions and are therefore indistinguishable by this analysis; 4) mAbs that neither induce homotypic aggregation nor block adhesion (epitope C mAbs) map to a distinct region of the molecule comprising amino acids 422-606. The N-terminal region of the alpha 4 chain identified by functional A and B epitope mAbs does not correspond to ligand binding sites identified in other alpha subunits, such as cation binding sites or the "I-domain," which alpha 4 lacks, and thus represents a novel site for epitope functionality among the integrins.
Schiffer
S G
SG
Biogen, Inc., Cambridge, Massachusetts 02142, USA.
Hemler
M E
ME
Lobb
R R
RR
Tizard
R
R
Osborn
L
L
D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology*; D001666:Binding Sites, Antibody / Q000235:genetics; D002460:Cell Line; D018076:DNA, Complementary; D018604:Epitope Mapping; D006801:Humans; D039441:Integrin alpha4; D051379:Mice
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018076:DNA, Complementary; D039441:Integrin alpha4