Beta7 integrin β7 subunit
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
Lymphocyte
100 / 115

Expression
b7 combines with the a4 subunit CD49d to form the a4b7 integrin and with the aE subunit CD103 to form the aEb7 integrin HML-1.  Both antigens are expressed on mucosal lymphocytes.  Adult human lymphocytes have a heterogeneous expression of  a4b7, whereas expression on newborn lymphocytes is more homogeneous.  a4b7 is also expressed on NK cells and eosinophils.  a4b7 is expressed on 95% of intraepithelial lymphocytes but only 1%-2% on peripheral blood lymphocytes.  Its level of expression on lymphocytes can be upregulated by lymphocyte mitogens.

Structure
The b7 integrin subunit is a single chain type 1 glycopeptide.  It is most closely related to the b2 integrin subunit CD18 including the cytoplasmic segment, in which 2 NPX Y/F motifs for potential tyrosine kinase binding are found.  Most integrin b  subunits have 56 conserved cysteine-residues in their extracellular portion.  The last 2 cysteines are missing from the b7 subunit.  The N-terminus has been determined by protein sequencing.

MOLECULAR MASS
Cell Type Unreduced Reduced
105 kDa 110 kDa



Ligands
Like the a4b1 integrin, a4b7 binds CD106 VCAM-1 and the CS1 region of fibronectin.  In addition, a4b7 binds the mucosal addressin MAdCAM-1. aEb7 binds E-cadherin on epithelial cells.

Function
The a4b7 integrin mediates the binding of lymphocytes to MAdCAM-1 on the high endothelial venules, thereby directing the homing of lymphocytes into Peyer's patches and the intestinal lamina propria.  The interaction between aEb7 and E-cadherin may be of importance in the homing and retention of aEb7 expressing lymphocytes to the intestinal epithelium.


Comments


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
MouseA46271P26011M68903
MouseM95632
Antibodies
FIB504   View Reactivity

Revised June 25, 2008


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