Interaction of the Integrin β1 Cytoplasmic Domain with ICAP-1 Protein*
- From the Dana-Farber Cancer Institute and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115
Abstract
In a yeast two-hybrid screen, a protein named ICAP-1 (β1 integrin cytoplasmic domain associated protein) associated with the integrin β1 cytoplasmic tail but not with tails from three other integrin β subunits (β2, β3, and β5) or from seven different α subunits. Likewise in human cells, ICAP-1 associated specifically with the β1 but not β2, β3, or β5 tails. The carboxyl-terminal 14 amino acids of β1 were critical for ICAP-1 interaction. ICAP-1 is a ubiquitously expressed protein of 27 and 31 kDa, with the smaller form being preferentially solubilized by Triton X-100. Phosphorylation of both 27- and 31-kDa forms was constitutive but was increased by 1.5–2-fold upon cell spreading on fibronectin, compared with poly-l-lysine. Also, ICAP-1 contributes to β1 integrin-dependent migration because (i) ICAP-1 transfection markedly increased chemotactic migration of COS7 cells through fibronectin-coated but not vitronectin-coated porous filters, and (ii) support of β1-dependent cell migration (in Chinese hamster ovary cells transfected with various wild type and mutant β1 forms) correlated with ICAP-1 association. In summary, ICAP-1 (i) associates specifically with β1 integrins, (ii) is phosphorylated upon β1 integrin-mediated adhesion, and (iii) may regulate β1-dependent cell migration.
Footnotes
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↵* This work was supported by National Institutes of Health Grant GM46526.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: Dana-Farber Cancer Institute, Rm. D-1410, 44 Binney St., Boston, MA 02115. Tel.: 617-632-3410; Fax: 617-632-2662; Email:Martin_Hemler{at}dfci.harvard.edu.
- Abbreviations:
- RACK
-
receptor for activated protein kinase C
- CHO
-
Chinese hamster ovary cell line
- FCS
-
fetal calf serum
- FN
-
fibronectin
- GST
-
glutathioneS-transferase
- dhfr
-
dihydrofolate reductase
- HEK293
-
human embryonic kidney 293 cell line
- HA
-
hemagglutinin
- ICAP-1
-
integrin cytoplasmic domain-associated protein-1
- mAb
-
monoclonal antibody
- PCR
-
polymerase chain reaction
- PLL
-
poly l-lysine
- X-gal
-
5-bromo-4-chloro-3-indolyl β-d-galactopyranoside
- MEM
-
minimum Eagle’s medium
- DMEM
-
Dulbecco’s modified Eagle’s medium
- PBS
-
phosphate-buffered saline.
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- Received April 1, 1998.
- Revision received September 30, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
