Structure-function analysis of the integrin beta 7 subunit: identification of domains involved in adhesion to MAdCAM-1.
Beta 7 integrins serve special roles in mucosal immunity. Alpha 4 beta 7-mediated adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) directs lymphocyte homing to the gut, and alpha E beta 7 mediates binding of lymphocytes to E-cadherin on epithelial cells. Since alpha 4 beta 7 mediates adhesion to MAdCAM-1 but alpha 4 beta 1 does not, we used beta 7/beta 1 chimeras to directly assess the importance of specific regions of beta 7 in MAdCAM-1 binding. We found a region of beta 7 (residues 46-386) that accounts for specificity of alpha 4 beta 7 binding to MAdCAM-1. We also used human/mouse and human/rat chimeric beta 7 subunits to map epitopes recognized by fifteen anti-beta 7 mAbs. Six of seven Abs that block adhesion to MAdCAM-1 and E-cadherin (Fib 21, 22, 27, 30, 504; Act-1) mapped to amino acid residues 176-250. Residues 176-250 lie within the region of beta 7 that specifies MAdCAM-1 binding and also within a region that has a predicted structure homologous to the metal ion-dependent adhesion site (MIDAS) domains of the integrin subunits alpha L and alpha M. Three new Abs that recognize beta 7 in the presence of Mn2+, but not Ca2+, and promote adhesion to MAdCAM-1, mapped to amino acids 46-149. One blocking and five other Abs mapped to other regions (amino acids 387-725). We conclude that a MIDAS-like domain serves a critical role in beta 7 integrin-mediated adhesion.
Tidswell
M
M
Lung Biology Center, Department of Medicine, University of California, San Francisco 94143, USA. easd@itsa.ucsf.edu
Pachynski
R
R
Wu
S W
SW
Qiu
S Q
SQ
Dunham
E
E
Cochran
N
N
Briskin
M J
MJ
Kilshaw
P J
PJ
Lazarovits
A I
AI
Andrew
D P
DP
Butcher
E C
EC
Yednock
T A
TA
Erle
D J
DJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D002412:Cations; D015815:Cell Adhesion Molecules; D018604:Epitope Mapping; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology / Q000378:metabolism*; D039641:Integrin beta Chains; D016023:Integrins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding / Q000276:immunology; D017434:Protein Structure, Tertiary; D051381:Rats; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012694:Serine / Q000276:immunology / Q000502:physiology; D013329:Structure-Activity Relationship; D014162:Transfection / Q000276:immunology; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D002412:Cations; D015815:Cell Adhesion Molecules; D007136:Immunoglobulins; D039641:Integrin beta Chains; D016023:Integrins; D008024:Ligands; C504265:MADCAM1 protein, human; C489082:Madcam1 protein, mouse; C504268:Madcam1 protein, rat; D009088:Mucoproteins; D016201:Receptors, Lymphocyte Homing; D011993:Recombinant Fusion Proteins; C091368:integrin beta7; D012694:Serine