Filamin Binds to the Cytoplasmic Domain of the β1-Integrin
IDENTIFICATION OF AMINO ACIDS RESPONSIBLE FOR THIS INTERACTION*
Abstract
Integrins play an important role in regulating cell adhesion, motility, and activation. In an effort to identify intracellular proteins expressed by activated T cells that interact with the cytoplasmic domain of β1-integrin (CD29), we used the β1-integrin cytoplasmic domain as bait in the yeast two-hybrid system. Here we report that the cytoplasmic domain of β1-integrin specifically interacts with the cytoskeletal protein filamin. This interaction required all but the most carboxyl-terminal three residues of the cytoplasmic domain of β1, and the carboxyl-terminal 477 residues of filamin containing the terminal 4.5 ∼96-residue tandem repeats of filamin. To verify this interaction in vivo, we showed that filamin specifically coprecipitated with β1 in mammalian cells. We also showed that recombinant filamin chimeric proteins were able to bind to the β1 cytoplasmic domain in vitro. We observed that a subset of single point mutations in the cytoplasmic domain of β1, which had been previously reported to impair its function, disrupt the interaction between β1and filamin. Taken together, these findings suggest that the interaction between β1 and filamin, which in turn can bind actin, provides a mechanism for the interaction of this cell surface receptor with cytoskeletal proteins and that this interaction plays a role in normal receptor function.
Footnotes
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed: BMS-PRI, P. O. Box 4000, Princeton, NJ 08543. Tel.: 609-252-5780; Fax: 609-252-6058; E-mail: lood{at}bms.com.
- Abbreviations:
- mAb
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monoclonal antibody
- PCR
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polymerase chain reaction
- PBS
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phosphate-buffered saline
- SD
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Specimen Diluent.
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- Received December 16, 1997.
- Revision received May 20, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
