A Biochemical Characterization of the Binding of Osteopontin to Integrins 
and 
(*)
- Dana D. Hu(1)(§),
- Emme C. K. Lin(1)(¶),
- Nicholas L. Kovach(2),
- John R. Hoyer(3)(**) and
- Jeffrey W. Smith(1)
- From the (1) Cancer Research Center, Program on Cell Adhesion and the Extracellular Matrix, La Jolla Cancer Research Foundation, La Jolla, California 92037,
- the (2) University of Washington, School of Medicine, Division of Hematology, Seattle, Washington 98195, and
- the (3) Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
Abstract
Osteopontin (OPN) is an extracellular matrix protein that binds to integrin α
β
. Here we demonstrate that two other integrins, α
β
and α
β
, are also receptors for OPN. Human embryonic kidney 293 cells adhere to human recombinant osteopontin (glutathione S-transferase-osteopontin; GST-OPN) using integrin α
β
. When the 293 cells are transfected with the β
subunit, they can also adhere to GST-OPN using integrin α
β
. Divalent cations regulate the binding of GST-OPN to both α
β
and α
β
. Mg
and Mn
support the binding of GST-OPN to these integrins but Ca
does not. The highest affinity is observed in Mn
. In the presence of this ion, the affinity of GST-OPN for α
β
is 18 nM and the affinity for α
β
is 48 nM. The antibody 8A2, which is an agonist for β
, promotes the adhesion of 293 cells to GST-OPN even when Ca
is present. This observation suggests that cellular events could modulate the affinity of α
β
for OPN. Collectively, these findings prove that integrins α
β
, α
β
, and α
β
have similar affinity for OPN. Therefore, all three integrins must be considered when evaluating the biological affects of
OPN.
Footnotes
-
↵§ Supported initially by a postdoctoral grant from Monsanto/Searle and then by a postdoctoral fellowship from the California Affiliate of the American Heart Association.
-
↵¶ Supported by a postdoctoral grant from the Cancer Research Institute.
-
↵** Established investigator of the American Heart Association and Genentech.
-
↵* This work was supported in part by National Institutes of Health Grants CA 56483 and AR 42750 (to J. W. S.), DK 10964 (to N. L. K.), and DK 33501 (to J. R. H.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- OPN
-
osteopontin
- GST-OPN
-
recombinant osteopontin that is a fusion protein with glutathione S-transferase
- RGD
-
Arg-Gly-Asp
- mAb
-
monoclonal antibody
- FACS
-
fluorescence-activated cell sorting.
-
- Received May 15, 1995.
- Revision received August 14, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
