Similar but nonidentical amino acid residues on vascular cell adhesion molecule-1 are involved in the interaction with alpha 4 beta 1 and alpha 4 beta 7 under different activity states.
The integrin receptors alpha 4 beta 1 and alpha 4 beta 7 both bind to vascular cell adhesion molecule-1 (VCAM-1). Here, we report that the amino acid residue requirements for murine VCAM-1 adhesion to murine alpha 4 beta 1 (WEHI 231) and alpha 4 beta 7 (38C13/beta 7-transfectant) positive cells are strikingly similar but nonidentical under multiple adhesion activity states. By site-directed mutagenesis of domain 1 of VCAM-1, the amino acid residues on the loop between beta strands C and D (R36, Q38, I39, D40, P42) and on the adjacent antiparallel beta strand F (L70 and T72) were required for basal level adhesion to both alpha 4 beta 1-positive and alpha 4 beta 7-positive cells. Mutation at two other sites, N44 (loop between beta strands C and D) and E66 (loop between beta strands E and F), specifically reduced alpha 4 beta 7-positive cell adhesion, but not alpha 4 beta 1-positive cell adhesion. Mutation H85A augmented alpha 4 beta 7 binding but not alpha 4 beta 1 binding. These apparent differences relate to the higher intrinsic activity state of alpha 4 beta 1 on WEHI 231 than on alpha 4 beta 7 (38C13/beta 7-transfectant). In contrast, under higher adhesion activity states induced by either MnCl2 or truncation of the beta 7 cytoplasmic tail, mutation of either amino acid residue D40 or L70 completely blocked cell adhesion without evidence of structural perturbation of VCAM-1. These results suggested that the two structurally discontinuous amino acid residues, the negatively charged D40 and the hydrophobic L70 adjacently located on domain 1 of VCAM-1, are essential for interaction under multiple activity states with both alpha 4 beta 1 and alpha 4 beta 7 integrin receptors.
Chiu
H H
HH
Department of Immunology, Genetech, Inc., South San Francisco, CA 94080, USA.
Crowe
D T
DT
Renz
M E
ME
Presta
L G
LG
Jones
S
S
Weissman
I L
IL
Fong
S
S
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002448:Cell Adhesion; D018604:Epitope Mapping; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D039041:Integrin alpha4beta1; D016023:Integrins; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; C071777:integrin alpha4beta7; D008345:Manganese