Mucosal addressin cell adhesion molecule-1: a structural and functional analysis demarcates the integrin binding motif.
The leukocyte integrin receptor, alpha 4 beta 7, and the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are postulated to be important in regulating lymphocyte trafficking to normal intestine. Here we provide the first description of MAdCAM-1 expression in inflamed intestine. Using mouse models of experimentally induced colitis, we show a concordant increase in MAdCAM-1 expression associated with increased cellular infiltrates in areas of intestinal inflammation. To understand more of the molecular nature of the interactions between MAdCAM-1 and its leukocyte ligand, the alpha 4 beta 7 integrin receptor, we have analyzed the structural and functional properties of chimeric recombinant MAdCAM-1 proteins in vitro. Using site-directed mutagenesis and molecular modeling, we demarcate the alpha 4 beta 7 binding motif as three linear residues within the C-D loop in the first domain of MAdCAM-1. Mutation of residue L40, D41, or T42 in the first domain completely abrogates alpha 4 beta 7+ cell binding and cellular activation. Mutagenesis of other residues in the first domain do not impact these functions. We have modeled peptides based on the predicted structure of the alpha 4 beta 7 integrin binding motif on MAdCAM-1 and are able to show specific and selective blocking of cell binding. These observations suggest that the amino acid residues LDT on MAdCAM-1 play a role in the interaction with alpha 4 beta 7 in cell adherence and cell activation.
Viney
J L
JL
Department of Immunology, Genentech, Inc., South San Francisco, CA 94080, USA.
Jones
S
S
Chiu
H H
HH
Lagrimas
B
B
Renz
M E
ME
Presta
L G
LG
Jackson
D
D
Hillan
K J
KJ
Lew
S
S
Fong
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D015815:Cell Adhesion Molecules; D003092:Colitis / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D007136:Immunoglobulins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D016023:Integrins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D011485:Protein Binding / Q000276:immunology; D011487:Protein Conformation; D016201:Receptors, Lymphocyte Homing / Q000737:chemistry* / Q000502:physiology*; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism
D015815:Cell Adhesion Molecules; D007136:Immunoglobulins; D016023:Integrins; C489082:Madcam1 protein, mouse; D009088:Mucoproteins; D010455:Peptides; D016201:Receptors, Lymphocyte Homing; D011994:Recombinant Proteins