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Role of Integrin α4β7/α4βP in Lymphocyte Adherence to Fibronectin and VCAM-1 and in Homotypic Cell Clustering

Curzio Rüegg, Antonio A. Postigo, Elizabeth E. Sikorski, Eugene C. Butcher, Robert Pytela and David J. Erle
The Journal of Cell Biology
Vol. 117, No. 1 (Apr., 1992), pp. 179-189
Stable URL: http://www.jstor.org/stable/1615061
Page Count: 11
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Role of Integrin α4β7/α4βP in Lymphocyte Adherence to Fibronectin and VCAM-1 and in Homotypic Cell Clustering
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Abstract

Integrins are heterodimeric cell surface proteins that mediate both cell-cell and cell-extracellular matrix interactions. We and others recently identified cDNAs encoding a novel integrin β subunit, β7, in lymphocytes. We have now detected β7 mRNA in mouse TK-1 T lymphoma cells, which are known to express the putative Peyer's patch homing receptor α4βP. We used an anti-peptide antiserum and a novel mAb against the β7 subunit to show that TK-1 cells express β7 as the only subunit associated with α4. We conclude that β7 and βP are identical. We also show that activated peripheral blood T cells express α4β7. We studied the function of α4β7/α4βP in TK-1 cells, which do not express very late antigen (VLA)-4 (α4β1). Cells adhered to intact fibronectin and to a fibronectin fragment containing the CS-1 region, but not to a fragment containing the RGD sequence. Adhesion to fibronectin was inhibited by antibodies to α4, suggesting that α4β7 is a fibronectin receptor. We confirmed that α4β7 binds to the CS-1 region of fibronectin using affinity chromatography. TK-1 cell adhesion to the vascular cell adhesion molecule VCAM-1 was also inhibited by antibodies to α4, implying that α4β7 also plays a role in the adherence of lymphocytes to endothelial cells. TK-1 cell binding to fibronectin and VCAM-1 is markedly increased by brief PMA stimulation. We also found that mAbs against α4 and β7 induce homotypic clustering of TK-1 cells. Taken together these results suggest that α4β7/α4βP recognizes some or all of the same widely distributed ligands recognized by VLA-4 (α4β1) and that the role of α4β7/α4βP may not be restricted to lymphocyte homing.

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