Alpha 3 beta 1 adhesion to laminin-5 and invasin: critical and differential role of integrin residues clustered at the boundary between alpha 3 N-terminal repeats 2 and 3.
Integrin/ligand interaction is a therapeutic target for many diseases. We previously reported that residues critical for ligand binding are clustered in N-terminal repeat 3 (in the predicted 2-3 loop) of alpha 4, alpha 5 and alpha IIb. Here we have localized residues critical for ligand binding in the alpha 3 subunit of integrin alpha 3 beta 1 with distinct ligand specificity (laminin-5). We identified an alpha 3 epitope common to several function-blocking anti-alpha 3 antibodies at the boundary between repeats 1 and 2 (residues 75-80). We found that swapping the predicted 4-1 loop (residues 153-165) at the boundary between repeats 2 and 3 with the corresponding alpha 4 sequence and mutating Thr-162 and Gly-163 residues in this predicted loop block laminin-5 binding. Thr-162 and Gly-163 and the antibody epitope are separated in the primary structure; however, they are close to each other in the proposed beta-propeller model. Mutating residues recently reported to block (Tyr-186 and Trp-188) or enhance (Asp-122) laminin-5 binding to alpha 3 beta 1 [Krukonis, E. S., Dersch, P., Eble, J. A., and Isberg, R. R.(1998) J. Biol. Chem. 273, 31837-31843] did not affect laminin-5 binding under the assay conditions used. Thr-162 and Gly-163 are not critical for adhesion to invasin, indicating that laminin-5 and invasin may use different recognition mechanisms, and that mutation of Thr-162 and Gly-163 does not drastically affect the integrity of alpha 3 beta 1. These results suggest that residues critical for ligand binding may be similarly (but not identically) located in repeat 3 of the alpha subunit regardless of ligand specificity.
Zhang
X P
XP
Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Puzon-McLaughlin
W
W
Irie
A
A
Kovach
N
N
Prokopishyn
N L
NL
Laferté
S
S
Takeuchi
K
K
Tsuji
T
T
Takada
Y
Y
D018829:Adhesins, Bacterial; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000378:metabolism*; D006224:Cricetinae; D018604:Epitope Mapping; D006801:Humans; D039422:Integrin alpha3; D039201:Integrin alpha3beta1; D016023:Integrins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020014:K562 Cells; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D013379:Substrate Specificity; D000097794:Kalinin
D018829:Adhesins, Bacterial; D015703:Antigens, CD; D001426:Bacterial Proteins; D015815:Cell Adhesion Molecules; D039422:Integrin alpha3; D039201:Integrin alpha3beta1; D016023:Integrins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D000097794:Kalinin; C053476:invasin, Yersinia